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The ontogenesis of skin and organ characteristics in the Syrian golden hamster
Exp. PathoL 1990; 40: 139 - 153 Gustav Fischer Verlag l ena
I) Central Animal Laboratory, University of Essen , F.R.G . 2) Diabetes Research Institute, University of Dusseldorf, F.R .G .
The ontogenesis of skin and organ characteristics in the Syrian golden hamster ll. Body and organ weights as well as blood glucose and plasma insulin levels By K. MILITZER l ) , L. HERBERG2) and D. BUTTNER l ) With 8 figures Received : July 25, 1989 ; Accepted : August 26, 1989
Address for correspondence: Priv-Doz. Dr. med. vet.
K LAUS MILITZER, Zentrales Tierlaboratorium am Universitatsklinikum, HufelandstraBe 55, W - 4300 Essen 1, F.R .G.
Key words: ontogenesis, organ weights ; liver, organ weights, ontogenesis ; kidney, organ weights, ontogenesis; adrenals, organ weights, ontogenesis; testis, organ weights, ontogenesis ; ovary, organ weights, ontogenesis ; blood glucose ; insulin level, plasma ; plasma insulin ; Syrian hamster ; organ weights, ontogenesis; skin, ontogenesis; age development ; body weight
Summary
The ontogenesis of the organ weights of the liver, kidneys, adrenals, testes and ovaries as well as the blood glucose and plasma insulin levels were studied in a total of 464 golden hamsters of both sexes of the acromelanic white inbred strain Bio 1.5 and agouti coloured outbred strain Han :AURA. Familial and seasonal influences were excluded by means of randomisati on (25 groups from 1- 365 days of life). Body weight development was found to be sigmoid and showed significant differences in terms of age, sex, and strain. Liver and kidney weights developed in parallel. Here, too, strain differences (agoutis> acromelanics) were seen, and sex differences were observed in the case of the kidneys (females > males). The increased adrenal weight in male hamsters compared to females was in accordance with species- but not rodent-t ypical behaviour. Both the testes and ovarian weights varied considerably. Age as well as, in part, strain differences were seen in the case of the blood glucose and insulin levels. The continual development of body and organ weight could be explained in terms of physiological changes.
Introduction The choice of suitable conditions for animal experiments can only be made rationally. if details concerning the species-specific development of the characteristics to be tested are already known during the experimental planning. Quantitat ive data on skin and organ characteristics for Exp. Pathol. 40 ( 1990) 3
139
the golden hamster and which take the influence of age, strain, and sex into consideration at the same time are also missing in the latest monographs (VAN HOOSIER and MCPHERSON 1987; HOBBS 1987). Our own studies were thus intended to overcome such decisive informational deficits. As a result, the development of the major skin compartments in the two strains of golden hamsters was described and quantified in Part I (MILITZER et al. 1990). Here, we describe the organ weight development in the liver, kidneys, adrenals, testes and ovaries. Our results for the first year of life of the hamsters are able to supplement both the temporally restricted data of SCHUMACHER et al. (1965 a-d) and FRAHM (1971) as well as those of HOGER et al. (1983). In Part I we have already reported on the size development of subcutaneous adipocytes in the golden hamster. Now, by measuring blood glucose and insulin levels, we additionally determined important parameters of the energy status in the hamster. The ontogenetic approach to as many as possible characteristics of anyone species delivers basic data for establishing growth models (CALDER 1984). In consequence, this is one of the major attempts of the present investigations. From a comparison of the data for 2 defined hamster strains, the strict randomised grouping as well as the duration of study from the 1st to 365th day of life, the below mentioned findings achieve particular significance.
Materials and Methods A total of 464 male and female Syrian hamsters was studied. Approximately half the animals were from agouti coloured outbred stock (Han: AURA) and the rest from an acromelanic white inbred strain (Bio 1.5). Details concerning breeding, maintenance, and grouping as well as statistical analysis are given in Part I (MILITZER et al. 1990). Blood glucose and plasma insulin determinations Blood was always removed retro-orbitally from adult hamsters in deep ether anaesthesia between 9.00 and 9.15 a. m. or pooled from vessels in the neck of younger animals (up to day 15 of life). The samples for the glucose determination were immediately centrifuged and deproteinated. Glucose was measured with hexokinase using the Gluco-quant combination test and control serum Precinorm (Boehringer, Mannheim, F.R. G.). Two serum samples per hamster were used for measuring plasma insulin levels (IRI = immunoreactive insulin) and which were stored at -16°C until assayed using solid-phaseimmunoassay (Deutsche Pharmacia, Frankfurt a. M., F.R.G.). The means of the samples determined in duplicates were used for statistical analysis. Body and organ weight determination Body weights were measured after killing the hamsters with an overdose of ether. Organ weights were only determined in hamsters older than 20 days. In younger animals the methodological error involved in the removal of organs was greater than the deviation between the animals. The liver, kidneys, adrenals, testes, and ovaries were removed, carefully freed from fat, and then kept in a moist chamber and weighed.
Results The results of the statistical tests involving the 3-fold analysis of variance are shown in table 1. All major data and t-test results for sexes and strains can be obtained from the author. Body weight In general, the body weights showed a typical sigmoidal distribution (fig. 1). At first, hamsters had a weight of 2 to 4 g. The body weight increased after day 2 and had doubled after days 5 to 7. The full-grown weight was largely reached between days 70 and 100 of life, so that 140
Exp. Pathol. 40 (1990) 3
Table 1. Results of the three-fold analysis of variance for the body and organ weights as well as biochemical data (overall results). It is shown for which of the factors strain, sex and age (subdivided into 5 classes) as well as their interactions there is a statistically significant effect on parameter size.
only a slight increase in body weight was observed later. Hence, 3 distinct phases were thus clearly recognizable: infant development, juvenile development from days 20 to 100 and the subsequent adult phase. The analysis of variance (table 1) showed significant deviations for the factors strain, sex, and age classes within the experimental groups. Significant strain differences could only be observed at certain dates such as days 40-90 and day 130 of life. At the end of the experiment, the male agoutis with an average body weight of 155g were 23 % heavier than the male acromelanic whites. Correspondingly, female agoutis of 140g b. wt. weighed 28 % more than the acromelanics. Hence, adult males were thus always significantly heavier than females. The fact that body weight differences occurred during the course of development is shown by the significant F-values in the analysis of variance of age classes (table I). The significant interrelations between strain and age classes resulted from the asynchronous increase in body weights. Liver weight
Overall, the steepest increase in liver weight after weaning was seen between days 25 and 40 (fig. 2), reaching a plateau in older age. The analysis of variance showed significant results only in the case of strain and age classes (table 1). In the females, strain differences largely occurred between days 40 to 80 and from day 120 onwards. At the age of one year, the liver weights in male and female agoutis were 42 % and 33 % heavier, respectively, than in the acromelanics. Kidney weight
The data always refer to the weight of both kidneys. Overall, there was a rapid increase in organ weight up to day 50 of life followed by a distinctly slow but continual increase in weight (fig. 3). The analysis of variance showed significant findings for the factors strain, sex and age classes. The higher kidney weights of up to 20 % in adult female agoutis were largely statistically significant (p = 0.05) in comparison to the acromelanics. 1l
Exp. Pathol. 40 (1990) 3
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Significant sex differences for agouti hamsters were found for days 150 to 200 as well as day 300 of life. During this period, the female kidneys were, on an average, 16-30% heavier than those of the males. As shown by the interrelations between strain and sex, sex and age classes as well as strain, sex and age classes (table 1), the development of kidney weight showed a temporal asynchrony both for the sexes as well as for the strains. Adrenal weight
Fig. 4 shows the group mean values for both adrenal weights. From the overall presentation it can be seen that there is a rapid increase in adrenal weights up to day 70 of life, followed by a plateau up to about day 150. At the end of the experiment, the adrenal weights decreased marginally. Strain differences were mainly found in the females. Whereas the adrenal weights in agouti 142
Exp. Pathol. 40 (1990) 3
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females remained constant up to day 365, acromelanic females showed a slow but continual reduction in weight. Similar but slighter differences in strain were also found in the case of the males. The differences in weight between sexes and strains particularly arose during the period from day 110 onwards. Male hamsters always showed higher adrenal weights. Testes and ovarian weights Overall , the weights of both testes without epididymides (fig. 5) showed a particularly long, persistent and overproportionally rapid growth in comparison to the development of other organs. Strain differences in testis weights were only found to be statistically significant on days 50 , 250 and 365 of life (p = 0.05). Despite greater deviations in weight at the times of investigation, the testes of agouti hamsters were, in the main, heavier than those of the acromelanics. The group mean values for ovarian weights are also shown in fig. 5. From the overall presentation, 2 bursts in ovarian weight development could be seen during the juvenile phase. In each case, a maximum was recognizable between days 40 to 50 as well as days 80 to 90 life. This 11*
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was followed by a plateau up to day 200 after whichtheovarian weights again increased slowly up to the end of the experiment. The analysis of variance (table 1) showed significant differences for both strain and age classes. The strain differences mainly occurred during adult age. On day 365 of life, the weight of the ovaries (79.4 mg) in the agoutis was 38 % higher than in the acromelanics. The significant interrelation (table 1) between the strains and age classes indicated that the development of ovarian weight did not take place at the same time in the 2 strains.
Blood glucose and plasma insulin levels For the determination of glucose and insulin levels, blood was drawn from non-fasted hamsters but always at the same time of day. Overall, the blood glucose level increased during the course of juvenile development, reaching a maximum at about day 50 of life (fig. 6). This was 144
Exp. Pathol. 40 (1990) 3
later followe d by a slow decrease . A mean value of 140mg/lOO ml was observed in the full-grown hamster. The blood glucose levels showed age- and strain-dependent differen ces, which were express ed in the statistically sivnifican t interrelation between strains and age classes . No significant sex differen ces cou lu ul: established (table I) . The plasma insul in levels are sho wn in fig. 7. Th e overall pre sentat ion shows parti cularl y large standard deviations of the group mean values. Even so, there was an increase in the insulin level during the infant and j uvenile phase followed by a decline at later times. On average , the mean overall insulin level was 88 ~lU/ ml but was lowe r ( 5 4 ~Ulml ) prior to weaning and higher (110 ~U/ml) in the ju venile phase. The large variations in insul in level s between the different hamster groups and times of investigation become even more apparent from the individual data (fig . 7). The curv es for the strain were found to be asynchronous as shown by the significant interrelation between strain and age classes (table I ). Both the glu cose and plasma insulin levels, in the main , showed no statistically significant mg . . . - -- -- --
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Exp. Pathol. 40 (1990) 3
Discussion Up to now, the setting-up of experimental groups for ontogenic studies has only seldom been described. On the one hand, unknown individual animals were scattered indiscriminately over the experimental period and, on the other, genetically defined siblings were used as groups for each investigation time-point. Only rarely, animals with known degree of relationship were assigned specifically and systematically to groups over the whole time of investigation. Our groups were made up at random of non-closely related animals from the most diverse families. By means of the time-consuming system of randomisation, it was ensured that each litter mate received the same chance of being assigned to one of the 25 age groups. Even so, it took 3 years until all hamster groups were adequately filled. Thus, from the start we took the population "golden hamster" into consideration and not familial or seasonal characteristics. As early as 1978, BUROW and RAPP had pointed out the necessity of such an experimental design for mice as well as describing the possible errors resulting from deviations in the most drastic terms. In spite of this, this method has up to now received little attention in studies involving hamsters or other laboratory animals . A vast array of individual data on body weight development in the golden hamster exists and could be confumed from our results. In general, the growth curve was s-shaped with a steep increase 2- 5 days after birth and an initial maximum between days 40 and 60 of life (BOND 1945; HOGER at al. 1983; LoCHBRUNNER 1956; ROBINSON 1973, and others). Our findings also revealed that the first steep increase in weight was completed between days 50 and 100, although the agouti hamsters showed a more rapid weight growth than the acromelanics. From an analysis of already published data on body weight development, SAGER (1985) confirmed the sigmoidal shape of the growth curve in the hamster. At the age of at least 200 days, the agoutis weighed between 106 and 177g (HOGER et aI. 1983 ; LOCHBRUNNER 1956) similar to that of our animals . OTHAKI (1979), HOGER et al. (1983) as well BIRT and CONRAD (1981) found that the female hamsters had the largest body weight. By contrast, FRAHM (1971) and LocnBRUNNER (1956) showed that, on average, the males were heavier than the females. A sex-specific disposition to adiposis in the dermis and abdomial cavity was considered to be responsible for the larger body weight in females, probably based on qualitative impressions (HOGER et aI. 1983). The size determination of inguinal adipocytes in our 2 strains of hamsters did not substantiate a hypertrophy of adipose tissue (MILlTZER et al. 1990). By contrast, our results showed that there were differences in body weight development with respect to both age as well as strains (fig. I , table 1). Earlier published findings were generally lacking in precise details concerning strains, but probably always referred to outbred agoutis. Our findings have shown that one must carefully differentiate between fast-growing, heavier agoutis and slower-growing hamster strains (acromelanic white). In particular, other authors (VAN DoNGEN et aI. 1980) have also pointed out the genetic basis of body growth in 3 strains of golden hamsters. The post-natal development of liver weight in baby hamsters (SCHUMACHER et al. 1965b) and adults (HOGER et al. 1983) has been extensively documented in the literature. It proceeded rapidly in the juvenile phase and in parallel to the body weight. The final organ weights of 5.9 and 5.2 g in males and females, respectively, were reached after about 70 days. We were able to confirm these data, which again are probably only valid for agoutis in their tendency for a defined outbred strain . The development of the liver weight, however, was not completed before day 100 (fig. 2), and was not so heavy as reported by the above mentioned authors. For the first time, there were indications of strain differences in golden hamsters (SHAW and TURTON 1979): animals of the acromelanic strain ALAClLac had lower organ weights compared to the agouti hamsters . This also applied to our acromelanic white hamsters . No statistically significant sex differences could be observed by us. By contrast , considerably lower liver weights (4.2-4 .7g) have been reported for male hamsters of approximately lOOg b. wt. (Ho 1975; JUSZKIEWICZ and STEFANIAK 1969). A part of the data from Ho (1975) are based on experiments involving a cholesterol-rich diet. The result clearly shows that liver weight can be enhanced by one-third through changes in the diet alone. Thus, only strictly standardized, uniform diets for various experimental groups can be expected to deliver comparable weight data . Exp, Pathol. 40 (1990) 3
149
The kidney weights of golden hamsters showed a close correlation to body weight development up to day 160 (SCHUMACHER et al. 1965b; HOGER et al. 1983). Kidney weights of 100 dayold hamsters were reported to be 0.85 ± 0.01 g and 1.04 ± 0.11 g in males and females, respectively (HACKBARTH et al. 1987). The corresponding weights in over 300 day-old animals were 1.3 and 1.8g. The sex-dependent increase in weight was attributed to an amyloidosis in all females (HOGER et al. 1983). A glomerular amyloidosis of the kidneys was seen by BUSCH (1987) only in exceptional cases in both the strains investigated by us. Sex differences in favour of the females at lower absolute kidney weights have been described by FRAHM (1971) and REZNIK et al. (1973). The kidney weights of adult males ranged from 0.7 to 0.8 (Ho 1975; JUSZKIEWICZ and STEFANIAK 1969). Our results confirm the reported course of kidney weight development and sex differences for fully-grown hamsters. However, similar extreme weights as observed by HOGER et al. (1983) were not reached in our animals. For the first time, however, significant strain differences were seen. The adrenal weight development in the hamster already showed a distinct sex difference at the age of 4 weeks. Contrary to other laboratory rodents, males had up to 55 % higher organ weights than females. This behaviour has been described in detail by HOGER et al. (1983), OHTAKI (1979), REZNIK et al. (1973). The cause of weight increase, namely a higher number of reticular cells in the adrenal cortex of the males, has been pointed out, in particular, by ZIEGER et al. (1974, 1982) as well as VAN HOOSIER and MCPHERSON (1987). Adrenal weights of 20 to 34 mg in adult males and 12 to 18mg in females have been reported (JUSZKIEWICZ and STEFANIAK 1969; KNIGGE 1954). We found statistically significant sex differences in adrenal weight from day 100 onwards. We were also able to confirm weight data for agouti hamsters. The acromelanics, however, had markedly lower adrenal weights in both sexes. From the results obtained concomitantly from 2 differently aggressive strains (MILITZER et al. 1990) it could be ruled out that the increase in adrenal weight in male golden hamsters was the result of social stress due to varying group composition. The course of testis weight development has been amply documented by SCHUMACHER et al. (1965b), FRAHM (1971) and HOGER et al. (1983), ranging from infancy up to adult age in the hamster (days 168 to 339). They showed that there was an overproportional testicular growth compared to body weight during the predominant part of juvenile development. At the age of 60 days, the hamsters had mean testis weights of 1.6± 1.2g (HOGER et al. 1983) to 3.3g (FRAHM 1971). Our own results as well as those of RASIM (1987) for the identical agouti-strain confirm the weight data of FRAHM. A considerable degree of variance in testis weights was observed in the various age groups (coefficient of variance == 75 %: FRAHM 1971). In our case, the coeffIcient of variance for testis weights in fully-grown animals ranged from 6-11 % (acrome1anic white inbred strain) and 4- 37 % (agouti outbred strain). HOGER et al. (1983) explained the large scatter as being due to a chance increase in cases with testicular atrophy. Studies involving our strain (RASIM 1987) could not confirm this effect. A distinct age-dependence has been reported in the cases of young animals up to the age of 2 months (0.7 to 1.5 g: MILLER et al. 1977; ORTIZ 1947) and adult hamsters (2.5 to 4.4g: OHTAKI 1979; REZNIK et al. 1973; RISSMAN 1980; TUREK 1979) despite a large variation in testis weight within the various periods of life. The testis weight development in golden hamsters could be affected by variations in the maintenance temperature and light period (BEX et al. 1978; HOFFMANN 1981; NUNEZ et al. 1985; STEGER et al. 1985). Since the conditions of maintenance were strictly defined for our hamsters from birth on, variable environmental effects as the cause of variation in testis weight could be absolutely ruled out. From the studies by HOGER et al. (1983) as well as FRAHM (1971) on agouti hamsters, the ovarian weights increased continuously with age and reached 30.8 - 36mg in adult females. By contrast, other authors have reported ovarian weights of 56.6 - 60mg (OHTAKI 1979; REZNIK et al. 1973). These larger weights agree more closely with our measurements. The rapid ovarian growth phase was completed between days 70-80, so that we refer to this period as the maturation boundary. Since the ovaries are only very small organs in the golden hamster, this would easily explain the mistakes arising from their preparation as well as the considerable deviations in organ weights between different investigations. 150
Exp. Pathol. 40 (1990) 3
The progress of the glucose level in hamsters was significantly age-dependent as described by BIRT (l982a, b), but there was no sexual dimorphism. Independent of the variable protein content of the diet, the glucose level reached a maximum between the first and sixth month of life and decreased markedly below the adolescent level up to the age of 1.5 years. A similar behaviour was seen in both hamster strains. ROBINSON (1968) reported glucose levels of 88.9 and 92.3 mgllOOml in juvenile and adult animals, respectively. Other studies have shown corresponding figures (VAUGHAN et al. 1982) which largely agreed with our findings. In general, glucose levels ranged from 44.7 to 156mg/100ml for hamsters not defined by age, sex or strain (DI BATTISTA 1982; GIRlet al. 1985; ROBINSON 1968). In 2 defined golden hamster strains (Lak : LVG, BIOFID) and for both sexes, MAXWELL et al. (1985) found blood glucose levels ranging from 37-213mg/ 100ml. As it was the case in our investigations (table I), significant differences in glucose levels were seen in both strains. Up to now, no studies on the age-dependence of plasma insulin levels in Syrian hamsters have been conducted. Our results showed marked age and strain effects despite the considerable variations seen. A decrease in plasma insulin levels as a function of age has only been described in the case ofrats (TURINSKY 1974). Levels of 1.9±0.5ng/ml were seen in adult female hamsters fed ad libitum (BORER et al. 1979). This corresponded to approximately 23.5-27.5/-lU/ml in our experiment. Male animals from the control group in the study by GIRl et al. (1985) had levels of 1.7- 2.1 ng/ml. Investigations on a species related to the golden hamster, the dwarf hamster Phodopus sungorus campbelli, showed a blood glucose level of 117.2mg/IOOml and a plasma insulin level of 61.3/-lU/ml in animals fed ad libitum (HERBERG et al. 1980). In the main, these data corresponded to the results from agouti Syrian hamsters. Because of marked fluctuations in daily rhythms of the biochemical parameters glucose and insulin levels as well as considerable influences through nutritional status and handling (general: JARRETT 1979; for glucose in the rat: GARTNER et al. 1980), the results from various investigators should, however, be compared with caution. Thus, agreement or deviations in the data for the biochemical parameters tested between various collections can only be seen in a few, methodologically comparable cases. In spite of this, our glucose levels in golden hamsters, always measured at the same time of day, showed that the animals were norrnoglycaemic, i. e., there were no deviations in blood glucose regulation. The glucose levels reported by GIRl et al. (1985) for hypoglycaemic golden hamsters were reached just as little as those glucose and plasma insulin levels measured by HERBERG et al. (1980) in glycosuric dwarf hamsters.
References BEX, F., BARTKE, A., GOLDMAN, B. D., DALTERIO, S.: Prolactin, growth hormone, luteinizing hormone receptors, and seasonal changes in testicular activity in the golden hamster. Endocrinology 1978; 103: 2069-2079. BrRT, D. F., CONRAD, R. D.: Weight gain, reproduction, and survival of Syrian hamsters fed five natural ingredient diets. Lab. Anim. Sci. 1981; 31: 149-155. - The effects of dietary fat and protein levels fed to Syrian hamsters early in life, on blood chemistry throughout life. Age 1982a; 5: 58-67. - The influence of dietary fat and protein on the aging hamster: Hemoglobin, glucose, triglycerides, and serum proteins. Age 1982b; 5: 92-99. BOND, C. R.: The golden hamster (Cricetus auratus), care, breeding, and growth. Physiol. Zoo!. 1945; 18: 52-59. BORER, K. T., PETERS, N. L., KELCH, R. P., TSAI, A. c., HOLDER, S.: Contribution of growth, fatness, and activity to weight disturbance after septohypothalamic cuts in adult hamsters. J. Compo Physio!. Psycho!. 1979; 93: 907-918. BUSCH, R.: Histometrische und histopathologische Charakterisierung altersabhangiger Nierenveranderungen an den Malpighischen Korperchen bei zwei Stammen des Syrischen Goldhamsters (Mesocricetus auratus W.). Vet. Med. Diss., GieBen 1987. CALDER, W. A.: Size, Function, and Life History. University Press, Harvard 1984. Dr BATTISTA, D.: Effects of 5-thioglucose on feeding and glycemia in the hamster. Physiol. Behav. 1982; 29: 803-806. Exp. Pathol. 40 (1990) 3
151
DONGEN, C. G. VAN, DOHERTY, P., HOMBURGER, F.: Factors affecting growth in various strains of inbred Syrian hamsters. Fed. Proc. 1980; 39: 3 (Abstract 4497). FRAHM, H.: Metrische Untersuchungen an den Organen von Hamstem der Gattungen Phodopus, Mesocricetus und Cricetus. Matb-naturw. Diss, Kiel 1971. GARTNER, K., BUTTNER, D., DOHLER, K., FRIEDEL, R., LINDENA, J., TRAUTSCHOLD, J.: Stress response of rats to handling and experimental producers. Lab. Anim. Sci. 1980; 14: 267-274. GIRl, S. N., NAKASHIMA, J. M., CURRY, D. L.: Effects of intratracheal administration of bleomycin or saline in pair-fed and control-fed hamsters on daily food intake and on plasma levels of glucose, cortisol, and insulin, and lung levels of calmodulin, calcium and collagen. Exp. Mol. Pathol. 1985; 42: 206- 217. HACKBARTH, H., BUCHHOLZ, CH., FRANKE, P., GUNTER, L., TAPKEN, H., MESSOW, C.: Vergleichende histometrische Untersuchungen zur GroBe der Nieren-Glomeruli bei Maus, Ratte und Hamster. Dtsch. Tieriirztl. Wochenschr. 1987; 94: 58-61. HERBERG, L., BUCHANAN, K. D., HERBERTZ, L. M., KERN, H. F., KLEY, H. K.: The Djungarian hamster, a laboratory animal with inappropriate hyperglycaemia. Compo Biochem. Physiol. 1980; 65A: 35-60. Ho, K.-J.: Effect of cholesterol feeding on circadian rhythm of hepatic and intestinal cholesterol biosynthesis in hamsters. Proc. Soc. Exp. BioI. Med. 1975; 150: 271-277. HOBBS, K. R.: Hamsters. In: The UFAW Handbook on the Care and Management of Laboratory Animals, 6th Edition (ed. POLE, T. B.), pp. 377-392. Longman, Harlow 1987. HOGER, H., GIALAMAS, J., ADAMIKER, D.: Masseentwicklung und Organmasse beim Syrischen Goldhamster mit Beriicksichtigung a1tersbedingter Organveranderungen, Z. Versuchstierkd. 1983; 25: 317- 331. HOFFMANN, K.: 1st die Zirbeldruse der Sauget ein antigonadotropes Organ? Verh. Dtsch. Zool. Ges. 1981: 97-109. HOOSIER, G. VAN, MCPHERSON, C. W. (eds.): Laboratory Hamsters. Academic Press, Orlando 1987. JARRETT, R. J.: Rhythms in insulin and glucose. Compo Endocrinol. 1979; 1: 247-257. JUSZKlEWICZ, T., STEFANIAK, B.: Some normal values for blood and organs in the golden hamster. Vet. Rec. 1969; 85: 501. KNIGGE, K. M.: The effect of acute starvation on the adrenal cortex of the hamster. Anat. Rec. 1954; 120: 555-575. LOCHBRUNNER, A.: Beitrage zur Physiologie des Syrischen Goldhamsters Mesocricetus auratus (Nehring). Zool. Jahrb. Abt. 1. Allg. Zool. Phyiol. Tiere (Jena) 1956; 66: 389-428. MAXWELL, K. 0., WISH, C., MURPHY, J. C., Fox, J. G.: Serum chemistry reference values in two strains of Syrian hamsters. Lab. Anim. Sci. 1985; 35: 67-70. MILITZER, K., HIRCHE, H., MOOG, E.: The ontogenesis of skin and organ characteristics in the Syrian golden hamsters. I. Skin compartments and subcutaneous adipocytes. Exp. Pathol. 1989; 40: 77-93. MILLER, L. L., WHITSETT, J. M., VANDENBERGH, J. G., COLBY, D. R.: Physical and behavioural aspects of sexual maturation in male golden hamsters. J. Compo PhysioJ. Psychol. 1977; 91: 245-259. NUNEZ, A. A., BROWN, M. H., YOUNGSTROM, T. G.: Hypothalamic circuits involved in the regulation of seasonal and circadian rhythms in male golden hamsters. Brain Res. Bull. 1985; 15: 149-153. OHTAKI, S.: Conspicuous sex difference in zona reticularis of the adrenal cortex of Syrian hamsters. Lab. Anim. Sci. 1979; 29: 765-769. ORTIZ, E.: The postnatal development of the reproductive system of the golden hamster (Cricetus auratus) and its reactivity to hormones. Physiol. Zool. 1947; 20: 45-66. RASIM, R.: Histometrische Untersuchungen zur Spermatogenese und Hodenentwicklung von zwei Stammen Syrischer Goldhamster (Mesocricetus auratus Waterhouse) zwischen 1. und 365. Lebenstag. Vet. Med. Diss., Hannover 1987. REZNIK, G., REZNIK-SCHULLER, H., MOHR, U.: Comparative studies of organs in the European hamster (Cricetus cricetus L.), the Syrian golden hamster (Mesocricetus auratus W.) and the Chinese hamster (Cricetus criseus M.). Z. Versuchstierkd. 1973; 15: 272-282. R!SSMANN, E. F.: Prepubertal sensitivity to melatonin in male hamsters. BioI. Reprod. 1980; 22: 277-280. ROBINSON, P. F.: General aspects of physiology. In: The Golden Hamster - Its Biology and Use in Medical Research (eds. HOFMANN, R. A., ROBINSON, P. F., MAGALHAES, H.), pp. 111-118. State University Press, Iowa 1968. ROBINSON, R.: Acromelanic albinism in mammals. Genetica 1973; 44: 454-458. SAGER, G.: Approximationen des Masse- und Langenwachstums beim Goldhamster (Mesocricetus auratus Waterhouse) nach Daten von Du BOIS (1950). Anat. Anz. (lena) 1985; 158: 181-191. SCHUMACHER, G. H., WOLFF, E., JUTZI, E.: Quantitative Untersuchungen tiber das postnatale Organwachstum des Goldhamsters (Mesocricetus auratus Wtrh.). I. Korpcrgewicht-Herz. Gegenbaurs Morphol. Jahrb. 1965a; 107:550-567. - - Quantitative Untersuchungen tiber das postnatale Organwachstum des Goldhamsters (Mesocricetus auratus Wtrh.). II. Lunge-Leber-Milz. Gegenbaurs Morpho!. Jahrb. 1965b; 108: 18-40.
152
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-
-
-
Quantitative Untersuchungen tiber das postnatale Organwachstum des Goldhamsters (Mesocricetus
auratus Wtrh.). III. Thymus-Schilddriise-Nebenniere-Mundspeicheldriise-Oesophagus-Magen-Darrn. Gegenbaues Morpho!. Jahrb. 1965c; 108: 41-66. - - Quantitative Untersuchungen tiber das postnata1e Organwachstum des Goldhamsters (Mesocricetus auratus Wtrh.). IV. Besprechung der Ergebnisse (SchluB). Gegenbaurs Morpho!. Jahrb. 1965d; 108:
123-138. SHAW, D. C., TURTON, J. A.: Inbred and genetically defined strains of laboratory animals, Part 2. 1979; Cit. by HOGER et al. 1983. STEGER, R. W., MATT, K., BARTKE, A.: Neuroendocrine regulation of seasonal reproductive activity in the male golden hamster. Neurosci. Biobehav. Rev. 1985; 9: 191-201. TUREK, F. W.: Effect of melatonin on photic-independent and photic-dependent testicular growth in juvenile and adult male golden hamsters. Bio!. Rep. 1979; 20: 1119-1122. TURlNSKY, J.: Insulin sensitivity and degradation during ontogeny in the rat. Fed. Proc. 1974; 33: 276 (Abstract). VAUGHAN, M. K., RICHARDSON, B. A., CRAFT, C. M., POWANDA, M. C., REITER, R. J.: Interaction of ageing, photoperiod and melatonin on plasma thyroid hormones and cholesterol levels in female Syrian hamsters (Mesocricetus auratus). Gerontology 1982; 28: 345-353. ZIEGER, G., Lux, B., KUBATSCH, B.: Sex dimorphism in the adrenal of hamsters. Acta Endocrino!. 1974: 75: 550-560. ZIEGER, W., KUBATSCH, B.: Effect and duration of gestagen influence on adrenal cortex and ovary. Patho!' Res. Pract. 1982; 173: 202-217.
Exp. Patho!. 1990; 40: 153-154 Gustav Fischer Verlag Jena
Book Review
Thymus Update 1 The Microenvironment of the Human Thymus
edited by M. D. KENDALL and M. A. RITTER. 306 pages, list price $84.00 (SAS price $51.00), ISBN: 3-7186-4806-7. Harwood Academic Publishers, Chur-London-Paris-New York-Melbourne 1988.
Thymus Update 2 T Lymphocyte Differentiation in the Human Thymus
edited by M. D. KENDALL and M. A. RITTER. 324 pages, with illustrations, list price $120.00 (SAS price $59.00), ISBN: 3-7186-4932-2. Harwood Academic Publishers, Chur-London-ParisNew York-Melbourne 1988. These two monographs of the series "Thymus Update" cover the microenvironment of the human thymus (Vol. 1) and the T lymphocyte differentiation in the human thymus (Vol. 2). Additional volumes are in preparation. - The task of this new series of books is to present an upto-date forum for research workers who are interested in the thymus. Everyone is familiar with the problems of an updated information in modem science, e. g., review articles are frequently out of date by the time they reach the reader. This is why the editors and the publishing house will publish the monographs of this series once a year combining a review-type format with the publication speed of a journal. According to the different types of information each volume will be divided into three sections: Exp. Pathol. 40 (1990) 3
153
I) Central Animal Laboratory, University of Essen , F.R.G . 2) Diabetes Research Institute, University of Dusseldorf, F.R .G .
The ontogenesis of skin and organ characteristics in the Syrian golden hamster ll. Body and organ weights as well as blood glucose and plasma insulin levels By K. MILITZER l ) , L. HERBERG2) and D. BUTTNER l ) With 8 figures Received : July 25, 1989 ; Accepted : August 26, 1989
Address for correspondence: Priv-Doz. Dr. med. vet.
K LAUS MILITZER, Zentrales Tierlaboratorium am Universitatsklinikum, HufelandstraBe 55, W - 4300 Essen 1, F.R .G.
Key words: ontogenesis, organ weights ; liver, organ weights, ontogenesis ; kidney, organ weights, ontogenesis; adrenals, organ weights, ontogenesis; testis, organ weights, ontogenesis ; ovary, organ weights, ontogenesis ; blood glucose ; insulin level, plasma ; plasma insulin ; Syrian hamster ; organ weights, ontogenesis; skin, ontogenesis; age development ; body weight
Summary
The ontogenesis of the organ weights of the liver, kidneys, adrenals, testes and ovaries as well as the blood glucose and plasma insulin levels were studied in a total of 464 golden hamsters of both sexes of the acromelanic white inbred strain Bio 1.5 and agouti coloured outbred strain Han :AURA. Familial and seasonal influences were excluded by means of randomisati on (25 groups from 1- 365 days of life). Body weight development was found to be sigmoid and showed significant differences in terms of age, sex, and strain. Liver and kidney weights developed in parallel. Here, too, strain differences (agoutis> acromelanics) were seen, and sex differences were observed in the case of the kidneys (females > males). The increased adrenal weight in male hamsters compared to females was in accordance with species- but not rodent-t ypical behaviour. Both the testes and ovarian weights varied considerably. Age as well as, in part, strain differences were seen in the case of the blood glucose and insulin levels. The continual development of body and organ weight could be explained in terms of physiological changes.
Introduction The choice of suitable conditions for animal experiments can only be made rationally. if details concerning the species-specific development of the characteristics to be tested are already known during the experimental planning. Quantitat ive data on skin and organ characteristics for Exp. Pathol. 40 ( 1990) 3
139
the golden hamster and which take the influence of age, strain, and sex into consideration at the same time are also missing in the latest monographs (VAN HOOSIER and MCPHERSON 1987; HOBBS 1987). Our own studies were thus intended to overcome such decisive informational deficits. As a result, the development of the major skin compartments in the two strains of golden hamsters was described and quantified in Part I (MILITZER et al. 1990). Here, we describe the organ weight development in the liver, kidneys, adrenals, testes and ovaries. Our results for the first year of life of the hamsters are able to supplement both the temporally restricted data of SCHUMACHER et al. (1965 a-d) and FRAHM (1971) as well as those of HOGER et al. (1983). In Part I we have already reported on the size development of subcutaneous adipocytes in the golden hamster. Now, by measuring blood glucose and insulin levels, we additionally determined important parameters of the energy status in the hamster. The ontogenetic approach to as many as possible characteristics of anyone species delivers basic data for establishing growth models (CALDER 1984). In consequence, this is one of the major attempts of the present investigations. From a comparison of the data for 2 defined hamster strains, the strict randomised grouping as well as the duration of study from the 1st to 365th day of life, the below mentioned findings achieve particular significance.
Materials and Methods A total of 464 male and female Syrian hamsters was studied. Approximately half the animals were from agouti coloured outbred stock (Han: AURA) and the rest from an acromelanic white inbred strain (Bio 1.5). Details concerning breeding, maintenance, and grouping as well as statistical analysis are given in Part I (MILITZER et al. 1990). Blood glucose and plasma insulin determinations Blood was always removed retro-orbitally from adult hamsters in deep ether anaesthesia between 9.00 and 9.15 a. m. or pooled from vessels in the neck of younger animals (up to day 15 of life). The samples for the glucose determination were immediately centrifuged and deproteinated. Glucose was measured with hexokinase using the Gluco-quant combination test and control serum Precinorm (Boehringer, Mannheim, F.R. G.). Two serum samples per hamster were used for measuring plasma insulin levels (IRI = immunoreactive insulin) and which were stored at -16°C until assayed using solid-phaseimmunoassay (Deutsche Pharmacia, Frankfurt a. M., F.R.G.). The means of the samples determined in duplicates were used for statistical analysis. Body and organ weight determination Body weights were measured after killing the hamsters with an overdose of ether. Organ weights were only determined in hamsters older than 20 days. In younger animals the methodological error involved in the removal of organs was greater than the deviation between the animals. The liver, kidneys, adrenals, testes, and ovaries were removed, carefully freed from fat, and then kept in a moist chamber and weighed.
Results The results of the statistical tests involving the 3-fold analysis of variance are shown in table 1. All major data and t-test results for sexes and strains can be obtained from the author. Body weight In general, the body weights showed a typical sigmoidal distribution (fig. 1). At first, hamsters had a weight of 2 to 4 g. The body weight increased after day 2 and had doubled after days 5 to 7. The full-grown weight was largely reached between days 70 and 100 of life, so that 140
Exp. Pathol. 40 (1990) 3
Table 1. Results of the three-fold analysis of variance for the body and organ weights as well as biochemical data (overall results). It is shown for which of the factors strain, sex and age (subdivided into 5 classes) as well as their interactions there is a statistically significant effect on parameter size.
only a slight increase in body weight was observed later. Hence, 3 distinct phases were thus clearly recognizable: infant development, juvenile development from days 20 to 100 and the subsequent adult phase. The analysis of variance (table 1) showed significant deviations for the factors strain, sex, and age classes within the experimental groups. Significant strain differences could only be observed at certain dates such as days 40-90 and day 130 of life. At the end of the experiment, the male agoutis with an average body weight of 155g were 23 % heavier than the male acromelanic whites. Correspondingly, female agoutis of 140g b. wt. weighed 28 % more than the acromelanics. Hence, adult males were thus always significantly heavier than females. The fact that body weight differences occurred during the course of development is shown by the significant F-values in the analysis of variance of age classes (table I). The significant interrelations between strain and age classes resulted from the asynchronous increase in body weights. Liver weight
Overall, the steepest increase in liver weight after weaning was seen between days 25 and 40 (fig. 2), reaching a plateau in older age. The analysis of variance showed significant results only in the case of strain and age classes (table 1). In the females, strain differences largely occurred between days 40 to 80 and from day 120 onwards. At the age of one year, the liver weights in male and female agoutis were 42 % and 33 % heavier, respectively, than in the acromelanics. Kidney weight
The data always refer to the weight of both kidneys. Overall, there was a rapid increase in organ weight up to day 50 of life followed by a distinctly slow but continual increase in weight (fig. 3). The analysis of variance showed significant findings for the factors strain, sex and age classes. The higher kidney weights of up to 20 % in adult female agoutis were largely statistically significant (p = 0.05) in comparison to the acromelanics. 1l
Exp. Pathol. 40 (1990) 3
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Significant sex differences for agouti hamsters were found for days 150 to 200 as well as day 300 of life. During this period, the female kidneys were, on an average, 16-30% heavier than those of the males. As shown by the interrelations between strain and sex, sex and age classes as well as strain, sex and age classes (table 1), the development of kidney weight showed a temporal asynchrony both for the sexes as well as for the strains. Adrenal weight
Fig. 4 shows the group mean values for both adrenal weights. From the overall presentation it can be seen that there is a rapid increase in adrenal weights up to day 70 of life, followed by a plateau up to about day 150. At the end of the experiment, the adrenal weights decreased marginally. Strain differences were mainly found in the females. Whereas the adrenal weights in agouti 142
Exp. Pathol. 40 (1990) 3
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females remained constant up to day 365, acromelanic females showed a slow but continual reduction in weight. Similar but slighter differences in strain were also found in the case of the males. The differences in weight between sexes and strains particularly arose during the period from day 110 onwards. Male hamsters always showed higher adrenal weights. Testes and ovarian weights Overall , the weights of both testes without epididymides (fig. 5) showed a particularly long, persistent and overproportionally rapid growth in comparison to the development of other organs. Strain differences in testis weights were only found to be statistically significant on days 50 , 250 and 365 of life (p = 0.05). Despite greater deviations in weight at the times of investigation, the testes of agouti hamsters were, in the main, heavier than those of the acromelanics. The group mean values for ovarian weights are also shown in fig. 5. From the overall presentation, 2 bursts in ovarian weight development could be seen during the juvenile phase. In each case, a maximum was recognizable between days 40 to 50 as well as days 80 to 90 life. This 11*
Exp. Palhol. 40 ( L990) 3
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was followed by a plateau up to day 200 after whichtheovarian weights again increased slowly up to the end of the experiment. The analysis of variance (table 1) showed significant differences for both strain and age classes. The strain differences mainly occurred during adult age. On day 365 of life, the weight of the ovaries (79.4 mg) in the agoutis was 38 % higher than in the acromelanics. The significant interrelation (table 1) between the strains and age classes indicated that the development of ovarian weight did not take place at the same time in the 2 strains.
Blood glucose and plasma insulin levels For the determination of glucose and insulin levels, blood was drawn from non-fasted hamsters but always at the same time of day. Overall, the blood glucose level increased during the course of juvenile development, reaching a maximum at about day 50 of life (fig. 6). This was 144
Exp. Pathol. 40 (1990) 3
later followe d by a slow decrease . A mean value of 140mg/lOO ml was observed in the full-grown hamster. The blood glucose levels showed age- and strain-dependent differen ces, which were express ed in the statistically sivnifican t interrelation between strains and age classes . No significant sex differen ces cou lu ul: established (table I) . The plasma insul in levels are sho wn in fig. 7. Th e overall pre sentat ion shows parti cularl y large standard deviations of the group mean values. Even so, there was an increase in the insulin level during the infant and j uvenile phase followed by a decline at later times. On average , the mean overall insulin level was 88 ~lU/ ml but was lowe r ( 5 4 ~Ulml ) prior to weaning and higher (110 ~U/ml) in the ju venile phase. The large variations in insul in level s between the different hamster groups and times of investigation become even more apparent from the individual data (fig . 7). The curv es for the strain were found to be asynchronous as shown by the significant interrelation between strain and age classes (table I ). Both the glu cose and plasma insulin levels, in the main , showed no statistically significant mg . . . - -- -- --
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Exp. Pathol. 40 (1990) 3
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Exp. Pathol. 40 (1990) 3
Discussion Up to now, the setting-up of experimental groups for ontogenic studies has only seldom been described. On the one hand, unknown individual animals were scattered indiscriminately over the experimental period and, on the other, genetically defined siblings were used as groups for each investigation time-point. Only rarely, animals with known degree of relationship were assigned specifically and systematically to groups over the whole time of investigation. Our groups were made up at random of non-closely related animals from the most diverse families. By means of the time-consuming system of randomisation, it was ensured that each litter mate received the same chance of being assigned to one of the 25 age groups. Even so, it took 3 years until all hamster groups were adequately filled. Thus, from the start we took the population "golden hamster" into consideration and not familial or seasonal characteristics. As early as 1978, BUROW and RAPP had pointed out the necessity of such an experimental design for mice as well as describing the possible errors resulting from deviations in the most drastic terms. In spite of this, this method has up to now received little attention in studies involving hamsters or other laboratory animals . A vast array of individual data on body weight development in the golden hamster exists and could be confumed from our results. In general, the growth curve was s-shaped with a steep increase 2- 5 days after birth and an initial maximum between days 40 and 60 of life (BOND 1945; HOGER at al. 1983; LoCHBRUNNER 1956; ROBINSON 1973, and others). Our findings also revealed that the first steep increase in weight was completed between days 50 and 100, although the agouti hamsters showed a more rapid weight growth than the acromelanics. From an analysis of already published data on body weight development, SAGER (1985) confirmed the sigmoidal shape of the growth curve in the hamster. At the age of at least 200 days, the agoutis weighed between 106 and 177g (HOGER et aI. 1983 ; LOCHBRUNNER 1956) similar to that of our animals . OTHAKI (1979), HOGER et al. (1983) as well BIRT and CONRAD (1981) found that the female hamsters had the largest body weight. By contrast, FRAHM (1971) and LocnBRUNNER (1956) showed that, on average, the males were heavier than the females. A sex-specific disposition to adiposis in the dermis and abdomial cavity was considered to be responsible for the larger body weight in females, probably based on qualitative impressions (HOGER et aI. 1983). The size determination of inguinal adipocytes in our 2 strains of hamsters did not substantiate a hypertrophy of adipose tissue (MILlTZER et al. 1990). By contrast, our results showed that there were differences in body weight development with respect to both age as well as strains (fig. I , table 1). Earlier published findings were generally lacking in precise details concerning strains, but probably always referred to outbred agoutis. Our findings have shown that one must carefully differentiate between fast-growing, heavier agoutis and slower-growing hamster strains (acromelanic white). In particular, other authors (VAN DoNGEN et aI. 1980) have also pointed out the genetic basis of body growth in 3 strains of golden hamsters. The post-natal development of liver weight in baby hamsters (SCHUMACHER et al. 1965b) and adults (HOGER et al. 1983) has been extensively documented in the literature. It proceeded rapidly in the juvenile phase and in parallel to the body weight. The final organ weights of 5.9 and 5.2 g in males and females, respectively, were reached after about 70 days. We were able to confirm these data, which again are probably only valid for agoutis in their tendency for a defined outbred strain . The development of the liver weight, however, was not completed before day 100 (fig. 2), and was not so heavy as reported by the above mentioned authors. For the first time, there were indications of strain differences in golden hamsters (SHAW and TURTON 1979): animals of the acromelanic strain ALAClLac had lower organ weights compared to the agouti hamsters . This also applied to our acromelanic white hamsters . No statistically significant sex differences could be observed by us. By contrast , considerably lower liver weights (4.2-4 .7g) have been reported for male hamsters of approximately lOOg b. wt. (Ho 1975; JUSZKIEWICZ and STEFANIAK 1969). A part of the data from Ho (1975) are based on experiments involving a cholesterol-rich diet. The result clearly shows that liver weight can be enhanced by one-third through changes in the diet alone. Thus, only strictly standardized, uniform diets for various experimental groups can be expected to deliver comparable weight data . Exp, Pathol. 40 (1990) 3
149
The kidney weights of golden hamsters showed a close correlation to body weight development up to day 160 (SCHUMACHER et al. 1965b; HOGER et al. 1983). Kidney weights of 100 dayold hamsters were reported to be 0.85 ± 0.01 g and 1.04 ± 0.11 g in males and females, respectively (HACKBARTH et al. 1987). The corresponding weights in over 300 day-old animals were 1.3 and 1.8g. The sex-dependent increase in weight was attributed to an amyloidosis in all females (HOGER et al. 1983). A glomerular amyloidosis of the kidneys was seen by BUSCH (1987) only in exceptional cases in both the strains investigated by us. Sex differences in favour of the females at lower absolute kidney weights have been described by FRAHM (1971) and REZNIK et al. (1973). The kidney weights of adult males ranged from 0.7 to 0.8 (Ho 1975; JUSZKIEWICZ and STEFANIAK 1969). Our results confirm the reported course of kidney weight development and sex differences for fully-grown hamsters. However, similar extreme weights as observed by HOGER et al. (1983) were not reached in our animals. For the first time, however, significant strain differences were seen. The adrenal weight development in the hamster already showed a distinct sex difference at the age of 4 weeks. Contrary to other laboratory rodents, males had up to 55 % higher organ weights than females. This behaviour has been described in detail by HOGER et al. (1983), OHTAKI (1979), REZNIK et al. (1973). The cause of weight increase, namely a higher number of reticular cells in the adrenal cortex of the males, has been pointed out, in particular, by ZIEGER et al. (1974, 1982) as well as VAN HOOSIER and MCPHERSON (1987). Adrenal weights of 20 to 34 mg in adult males and 12 to 18mg in females have been reported (JUSZKIEWICZ and STEFANIAK 1969; KNIGGE 1954). We found statistically significant sex differences in adrenal weight from day 100 onwards. We were also able to confirm weight data for agouti hamsters. The acromelanics, however, had markedly lower adrenal weights in both sexes. From the results obtained concomitantly from 2 differently aggressive strains (MILITZER et al. 1990) it could be ruled out that the increase in adrenal weight in male golden hamsters was the result of social stress due to varying group composition. The course of testis weight development has been amply documented by SCHUMACHER et al. (1965b), FRAHM (1971) and HOGER et al. (1983), ranging from infancy up to adult age in the hamster (days 168 to 339). They showed that there was an overproportional testicular growth compared to body weight during the predominant part of juvenile development. At the age of 60 days, the hamsters had mean testis weights of 1.6± 1.2g (HOGER et al. 1983) to 3.3g (FRAHM 1971). Our own results as well as those of RASIM (1987) for the identical agouti-strain confirm the weight data of FRAHM. A considerable degree of variance in testis weights was observed in the various age groups (coefficient of variance == 75 %: FRAHM 1971). In our case, the coeffIcient of variance for testis weights in fully-grown animals ranged from 6-11 % (acrome1anic white inbred strain) and 4- 37 % (agouti outbred strain). HOGER et al. (1983) explained the large scatter as being due to a chance increase in cases with testicular atrophy. Studies involving our strain (RASIM 1987) could not confirm this effect. A distinct age-dependence has been reported in the cases of young animals up to the age of 2 months (0.7 to 1.5 g: MILLER et al. 1977; ORTIZ 1947) and adult hamsters (2.5 to 4.4g: OHTAKI 1979; REZNIK et al. 1973; RISSMAN 1980; TUREK 1979) despite a large variation in testis weight within the various periods of life. The testis weight development in golden hamsters could be affected by variations in the maintenance temperature and light period (BEX et al. 1978; HOFFMANN 1981; NUNEZ et al. 1985; STEGER et al. 1985). Since the conditions of maintenance were strictly defined for our hamsters from birth on, variable environmental effects as the cause of variation in testis weight could be absolutely ruled out. From the studies by HOGER et al. (1983) as well as FRAHM (1971) on agouti hamsters, the ovarian weights increased continuously with age and reached 30.8 - 36mg in adult females. By contrast, other authors have reported ovarian weights of 56.6 - 60mg (OHTAKI 1979; REZNIK et al. 1973). These larger weights agree more closely with our measurements. The rapid ovarian growth phase was completed between days 70-80, so that we refer to this period as the maturation boundary. Since the ovaries are only very small organs in the golden hamster, this would easily explain the mistakes arising from their preparation as well as the considerable deviations in organ weights between different investigations. 150
Exp. Pathol. 40 (1990) 3
The progress of the glucose level in hamsters was significantly age-dependent as described by BIRT (l982a, b), but there was no sexual dimorphism. Independent of the variable protein content of the diet, the glucose level reached a maximum between the first and sixth month of life and decreased markedly below the adolescent level up to the age of 1.5 years. A similar behaviour was seen in both hamster strains. ROBINSON (1968) reported glucose levels of 88.9 and 92.3 mgllOOml in juvenile and adult animals, respectively. Other studies have shown corresponding figures (VAUGHAN et al. 1982) which largely agreed with our findings. In general, glucose levels ranged from 44.7 to 156mg/100ml for hamsters not defined by age, sex or strain (DI BATTISTA 1982; GIRlet al. 1985; ROBINSON 1968). In 2 defined golden hamster strains (Lak : LVG, BIOFID) and for both sexes, MAXWELL et al. (1985) found blood glucose levels ranging from 37-213mg/ 100ml. As it was the case in our investigations (table I), significant differences in glucose levels were seen in both strains. Up to now, no studies on the age-dependence of plasma insulin levels in Syrian hamsters have been conducted. Our results showed marked age and strain effects despite the considerable variations seen. A decrease in plasma insulin levels as a function of age has only been described in the case ofrats (TURINSKY 1974). Levels of 1.9±0.5ng/ml were seen in adult female hamsters fed ad libitum (BORER et al. 1979). This corresponded to approximately 23.5-27.5/-lU/ml in our experiment. Male animals from the control group in the study by GIRl et al. (1985) had levels of 1.7- 2.1 ng/ml. Investigations on a species related to the golden hamster, the dwarf hamster Phodopus sungorus campbelli, showed a blood glucose level of 117.2mg/IOOml and a plasma insulin level of 61.3/-lU/ml in animals fed ad libitum (HERBERG et al. 1980). In the main, these data corresponded to the results from agouti Syrian hamsters. Because of marked fluctuations in daily rhythms of the biochemical parameters glucose and insulin levels as well as considerable influences through nutritional status and handling (general: JARRETT 1979; for glucose in the rat: GARTNER et al. 1980), the results from various investigators should, however, be compared with caution. Thus, agreement or deviations in the data for the biochemical parameters tested between various collections can only be seen in a few, methodologically comparable cases. In spite of this, our glucose levels in golden hamsters, always measured at the same time of day, showed that the animals were norrnoglycaemic, i. e., there were no deviations in blood glucose regulation. The glucose levels reported by GIRl et al. (1985) for hypoglycaemic golden hamsters were reached just as little as those glucose and plasma insulin levels measured by HERBERG et al. (1980) in glycosuric dwarf hamsters.
References BEX, F., BARTKE, A., GOLDMAN, B. D., DALTERIO, S.: Prolactin, growth hormone, luteinizing hormone receptors, and seasonal changes in testicular activity in the golden hamster. Endocrinology 1978; 103: 2069-2079. BrRT, D. F., CONRAD, R. D.: Weight gain, reproduction, and survival of Syrian hamsters fed five natural ingredient diets. Lab. Anim. Sci. 1981; 31: 149-155. - The effects of dietary fat and protein levels fed to Syrian hamsters early in life, on blood chemistry throughout life. Age 1982a; 5: 58-67. - The influence of dietary fat and protein on the aging hamster: Hemoglobin, glucose, triglycerides, and serum proteins. Age 1982b; 5: 92-99. BOND, C. R.: The golden hamster (Cricetus auratus), care, breeding, and growth. Physiol. Zoo!. 1945; 18: 52-59. BORER, K. T., PETERS, N. L., KELCH, R. P., TSAI, A. c., HOLDER, S.: Contribution of growth, fatness, and activity to weight disturbance after septohypothalamic cuts in adult hamsters. J. Compo Physio!. Psycho!. 1979; 93: 907-918. BUSCH, R.: Histometrische und histopathologische Charakterisierung altersabhangiger Nierenveranderungen an den Malpighischen Korperchen bei zwei Stammen des Syrischen Goldhamsters (Mesocricetus auratus W.). Vet. Med. Diss., GieBen 1987. CALDER, W. A.: Size, Function, and Life History. University Press, Harvard 1984. Dr BATTISTA, D.: Effects of 5-thioglucose on feeding and glycemia in the hamster. Physiol. Behav. 1982; 29: 803-806. Exp. Pathol. 40 (1990) 3
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DONGEN, C. G. VAN, DOHERTY, P., HOMBURGER, F.: Factors affecting growth in various strains of inbred Syrian hamsters. Fed. Proc. 1980; 39: 3 (Abstract 4497). FRAHM, H.: Metrische Untersuchungen an den Organen von Hamstem der Gattungen Phodopus, Mesocricetus und Cricetus. Matb-naturw. Diss, Kiel 1971. GARTNER, K., BUTTNER, D., DOHLER, K., FRIEDEL, R., LINDENA, J., TRAUTSCHOLD, J.: Stress response of rats to handling and experimental producers. Lab. Anim. Sci. 1980; 14: 267-274. GIRl, S. N., NAKASHIMA, J. M., CURRY, D. L.: Effects of intratracheal administration of bleomycin or saline in pair-fed and control-fed hamsters on daily food intake and on plasma levels of glucose, cortisol, and insulin, and lung levels of calmodulin, calcium and collagen. Exp. Mol. Pathol. 1985; 42: 206- 217. HACKBARTH, H., BUCHHOLZ, CH., FRANKE, P., GUNTER, L., TAPKEN, H., MESSOW, C.: Vergleichende histometrische Untersuchungen zur GroBe der Nieren-Glomeruli bei Maus, Ratte und Hamster. Dtsch. Tieriirztl. Wochenschr. 1987; 94: 58-61. HERBERG, L., BUCHANAN, K. D., HERBERTZ, L. M., KERN, H. F., KLEY, H. K.: The Djungarian hamster, a laboratory animal with inappropriate hyperglycaemia. Compo Biochem. Physiol. 1980; 65A: 35-60. Ho, K.-J.: Effect of cholesterol feeding on circadian rhythm of hepatic and intestinal cholesterol biosynthesis in hamsters. Proc. Soc. Exp. BioI. Med. 1975; 150: 271-277. HOBBS, K. R.: Hamsters. In: The UFAW Handbook on the Care and Management of Laboratory Animals, 6th Edition (ed. POLE, T. B.), pp. 377-392. Longman, Harlow 1987. HOGER, H., GIALAMAS, J., ADAMIKER, D.: Masseentwicklung und Organmasse beim Syrischen Goldhamster mit Beriicksichtigung a1tersbedingter Organveranderungen, Z. Versuchstierkd. 1983; 25: 317- 331. HOFFMANN, K.: 1st die Zirbeldruse der Sauget ein antigonadotropes Organ? Verh. Dtsch. Zool. Ges. 1981: 97-109. HOOSIER, G. VAN, MCPHERSON, C. W. (eds.): Laboratory Hamsters. Academic Press, Orlando 1987. JARRETT, R. J.: Rhythms in insulin and glucose. Compo Endocrinol. 1979; 1: 247-257. JUSZKlEWICZ, T., STEFANIAK, B.: Some normal values for blood and organs in the golden hamster. Vet. Rec. 1969; 85: 501. KNIGGE, K. M.: The effect of acute starvation on the adrenal cortex of the hamster. Anat. Rec. 1954; 120: 555-575. LOCHBRUNNER, A.: Beitrage zur Physiologie des Syrischen Goldhamsters Mesocricetus auratus (Nehring). Zool. Jahrb. Abt. 1. Allg. Zool. Phyiol. Tiere (Jena) 1956; 66: 389-428. MAXWELL, K. 0., WISH, C., MURPHY, J. C., Fox, J. G.: Serum chemistry reference values in two strains of Syrian hamsters. Lab. Anim. Sci. 1985; 35: 67-70. MILITZER, K., HIRCHE, H., MOOG, E.: The ontogenesis of skin and organ characteristics in the Syrian golden hamsters. I. Skin compartments and subcutaneous adipocytes. Exp. Pathol. 1989; 40: 77-93. MILLER, L. L., WHITSETT, J. M., VANDENBERGH, J. G., COLBY, D. R.: Physical and behavioural aspects of sexual maturation in male golden hamsters. J. Compo PhysioJ. Psychol. 1977; 91: 245-259. NUNEZ, A. A., BROWN, M. H., YOUNGSTROM, T. G.: Hypothalamic circuits involved in the regulation of seasonal and circadian rhythms in male golden hamsters. Brain Res. Bull. 1985; 15: 149-153. OHTAKI, S.: Conspicuous sex difference in zona reticularis of the adrenal cortex of Syrian hamsters. Lab. Anim. Sci. 1979; 29: 765-769. ORTIZ, E.: The postnatal development of the reproductive system of the golden hamster (Cricetus auratus) and its reactivity to hormones. Physiol. Zool. 1947; 20: 45-66. RASIM, R.: Histometrische Untersuchungen zur Spermatogenese und Hodenentwicklung von zwei Stammen Syrischer Goldhamster (Mesocricetus auratus Waterhouse) zwischen 1. und 365. Lebenstag. Vet. Med. Diss., Hannover 1987. REZNIK, G., REZNIK-SCHULLER, H., MOHR, U.: Comparative studies of organs in the European hamster (Cricetus cricetus L.), the Syrian golden hamster (Mesocricetus auratus W.) and the Chinese hamster (Cricetus criseus M.). Z. Versuchstierkd. 1973; 15: 272-282. R!SSMANN, E. F.: Prepubertal sensitivity to melatonin in male hamsters. BioI. Reprod. 1980; 22: 277-280. ROBINSON, P. F.: General aspects of physiology. In: The Golden Hamster - Its Biology and Use in Medical Research (eds. HOFMANN, R. A., ROBINSON, P. F., MAGALHAES, H.), pp. 111-118. State University Press, Iowa 1968. ROBINSON, R.: Acromelanic albinism in mammals. Genetica 1973; 44: 454-458. SAGER, G.: Approximationen des Masse- und Langenwachstums beim Goldhamster (Mesocricetus auratus Waterhouse) nach Daten von Du BOIS (1950). Anat. Anz. (lena) 1985; 158: 181-191. SCHUMACHER, G. H., WOLFF, E., JUTZI, E.: Quantitative Untersuchungen tiber das postnatale Organwachstum des Goldhamsters (Mesocricetus auratus Wtrh.). I. Korpcrgewicht-Herz. Gegenbaurs Morphol. Jahrb. 1965a; 107:550-567. - - Quantitative Untersuchungen tiber das postnatale Organwachstum des Goldhamsters (Mesocricetus auratus Wtrh.). II. Lunge-Leber-Milz. Gegenbaurs Morpho!. Jahrb. 1965b; 108: 18-40.
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-
-
-
Quantitative Untersuchungen tiber das postnatale Organwachstum des Goldhamsters (Mesocricetus
auratus Wtrh.). III. Thymus-Schilddriise-Nebenniere-Mundspeicheldriise-Oesophagus-Magen-Darrn. Gegenbaues Morpho!. Jahrb. 1965c; 108: 41-66. - - Quantitative Untersuchungen tiber das postnata1e Organwachstum des Goldhamsters (Mesocricetus auratus Wtrh.). IV. Besprechung der Ergebnisse (SchluB). Gegenbaurs Morpho!. Jahrb. 1965d; 108:
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Exp. Patho!. 1990; 40: 153-154 Gustav Fischer Verlag Jena
Book Review
Thymus Update 1 The Microenvironment of the Human Thymus
edited by M. D. KENDALL and M. A. RITTER. 306 pages, list price $84.00 (SAS price $51.00), ISBN: 3-7186-4806-7. Harwood Academic Publishers, Chur-London-Paris-New York-Melbourne 1988.
Thymus Update 2 T Lymphocyte Differentiation in the Human Thymus
edited by M. D. KENDALL and M. A. RITTER. 324 pages, with illustrations, list price $120.00 (SAS price $59.00), ISBN: 3-7186-4932-2. Harwood Academic Publishers, Chur-London-ParisNew York-Melbourne 1988. These two monographs of the series "Thymus Update" cover the microenvironment of the human thymus (Vol. 1) and the T lymphocyte differentiation in the human thymus (Vol. 2). Additional volumes are in preparation. - The task of this new series of books is to present an upto-date forum for research workers who are interested in the thymus. Everyone is familiar with the problems of an updated information in modem science, e. g., review articles are frequently out of date by the time they reach the reader. This is why the editors and the publishing house will publish the monographs of this series once a year combining a review-type format with the publication speed of a journal. According to the different types of information each volume will be divided into three sections: Exp. Pathol. 40 (1990) 3
153