- Email: [email protected]
Developmental trends of liver parenchyma in the terminal period of gestation: a stereological approach
Exp. Path. 21, 187-192 (1982) Department of Pathology, Faculty of Medicine, Comenius University, Martin, CSSR (Head: Prof. J. PLANK, lVLD.C.Sc.)
Developmental trends of liver parenchyma in the terminal period of gestation: a stereological approach By F. NOVOMESKY, J. PLANK and A. LEV elK With 3 figures (Received August 26, 1981) Address for correspondence: F. NOVOMESKY, M.D.C.Sc., Department of Pathology, Faculty of Medicine, University Hospital, Kollarova 10, CS - 03659 Martin, 0SSR Key words: liver development; intra-uterine growth retardation; stereology; gestation; fetus at risk; portal vein; hepatal vein; hepatal arterial branches; human
Summary The aim of the presented study was to establish the baseline data concerning the volume of basic architectonic components of human fetal liver parenchyma. The stereological measuring principles of the point-counting method were used. The livers of 38 appropriate for ges.tational age fetuses, and 12 small for gestational age fetuses were measured. All fetuses investigated were stillborns. A lower volume density of hepatocytic popUlation was found in full-term mature fetuses, when compared with the adults. A lower volume density of hepatocytes has been also disclosed in intra-uterine growth retarded fetuses, when compared with their physiologically developed counterparts of the same gestational age. den~ity
Introduction The increasing importance of clinical entity "fetus at risk" has drawn the attention to disturbances of development and maturation of the human fetus. From this point of view the works of PLANK: (1965, 1967 a, 1967b, 1973), PLANK and BEN CAT (1979), HISLOP and REID (1974), and NAEYE (1975) concerning the normal and abnormal development of the lung and kidney, and PLANK and BESEDA (1970), and BESEDA (1974) concerning the maturation of the gut are of a great importance. However, the quantitative aspect of the dynamics of the liver development has not yet been determined. Knowing this, we have tried to find by stereological measurements the quantitatively determined morphological criteria (base-line data) of the maturation process of growing liver parenchyma in physiologically developed human fetuses (appropriate for gestational age) of various stages of maturity (PLANK and NOVOMESKY 1980). Those data were then compared with the same data obtained in the group of intra-uterine growth retarded (small for gestational age) fetuses.
lvIaterial and Methods The livers of 38 human fetuses classified both clinically and morphologically as appropriate for their gestational age, and 12 livers of fetuses classified as intra-uterine growth retarded were investigated. The range of gestational age of all fetuses was between the 25th and 42nd week of intra-uterine life. All fetuses were stillborns in attempt to avoid circulatory changes in the livers after birth. Only the fetuses who died shortly ante partum or intra partum were chosen because of our intention to obtain the material without structural changes due to autolytic process. The estimation of the time of death was perhaps the major problem when completing the group of stillborns to be investigated. Here we were almost completely dependent on the clinical informations. Intra partum deaths of the fetuses might happen rather rarely in the obstetric practice, and most of the ante partum died fetuses were yet autolysed. In its consequence, this reality had considerably reduced our group of stillborns chosen for investigation. The standard excisions from the left liver lobe were taken in every suitable
187
ease. The exeisions passed through the normal histological processing cycle and were stained by hematoxylin-eosin and van Gieson method, which proved to be suitable for our purposes. All slides were examined thoroughly in the light microscope with the aim to eliminate all cases with the slightest signs of autolysis. For the stereological analysis the point-counting method according to WEIBEL (1966, 1967) was chosen. This method had allowed us to estimate the volume density of each basic architectonic component of liver parenchyma, e.g. hepatocytic population, vascular sinusoidal network, and so-called extralobular spaces. Endothelial sinusoidal lining, Kupffer cells, and hemopoietic elements were included within the values for sinusoidal network as such. Extralobular spaces were further divided as follows: 1. Connective tissue 2. Bile ducts 3. Portal vein branches (inci. terminal portal venules) 4. Hepatal vein branches (inci. terminal hepatal venules) 5. Hepatal arterial branches. The ocular grid (WILD®) was used for the point-counting measuring process. This grid consists of 42 test points arranged in a hexagonal manner. The ocular grid was permanently installed in the normal light microscope, and the specimen was driven on the stage of the microscope semiautomatically by an ELTINOR driving device (VEB Carl Zeiss JENA). This driving system completely supressed the subjectivism in the measuring process, and the basic condition of stereological measurement concerning the random selection of components to be measured was also fulfilled. When the conditions described are strictly kept, it can be stated after measuring the sufficient surface of the specimen, that the fraction of points which "hit" one or another component of liver parenchyma represents the equivalent volume density of this component in the liver tissue as a three-dimensional structure. In every suitable section of the liver parenchyma 2,100 test points were counted (50 fields of the ocular grid) while strictly keeping all necessary rules of stereological analysis and its mathematical evaluation described elsewhere (WEIBEL 1962, 1969, 1975). The physiologically developed appropriate for gestational age fetuses were divided into four subgroups according to their increasing gestational age, as follows: 1. 25th-29th week of gestation: 17 cases 2. 30th-34th week of gestation: 9 cases 3. 35th-39th week of gestation: 7 cases 4. 40th-42nd week of gestation: 5 cases. The group of intra-uterine growth retarded (lUG R) fetuses was naturally heterogeneous and its subdivision was as follows: 1. 25th-29th week of gestation: no suitable case 2. 30th-34th week of gestation: 4 cases 3. 35th-39th week of gestation: 6 cases 4. 40th-42nd week of gestation: 2 cases. In the group of intra-uterine growth retarded fetuses all major congenital anomalies were excluded, and the presumable causes of intra-uterine growth retardation were as follows: 1. 32nd gest.week: Unwed mother, causes of IUGR not clear 2. 33rd gest.week: heavy smoking habit of the mother in pregnancy 3. 34th gest. week: severe viral febrile infection of the mother in pregnancy 4. 34th gest. week: single umbilical artery 5. 35th gest.week: minor fetal congenital heart anomaly 6. 35th gest.week: triploidismus 69 7. 37th gest.week: by pregnancy induced hypertony 8. 37th gest. week: hypoplastic uterus, partus per sectione 9. 38th gest.week: by pregnancy induced hypertony 10. 39th gest.week: causes of IUG R not clear 11. 40th gest.week: 35 years old primipara, causes of IUGR not clear 12. 42nd gest.week: obesity of the mother, causes of IUGR not clear.
Results I. Physiologically developed fetuses appropriate for gestational age Here the livers from physiologically developed fetuses were investigated only. The hepatocytic population was of the main interest, an almost continuous rise was found in volume density of hepatocytes, together with increaeing gestational age of the fetus. Mirror-like decrement of sinusoidal volume density was also noted. There were no statistically significant differences in values for extralobular spaces, hence these values are excluded from the diagram (fig. 1). All values were found to be significant even statistically.
188
VVi
HEPATOCYTES
SINUSOIDS
60
en
N
It'i
N
~
50
ci
PI
oX
C!J ~
It'i
PI
...:en
40
enN
~
g I
I
It'i N
P
<
I!J
N -4'
I
I
PI
I
~
...: en
8.
N -4'
ci
CI
enPI Iri
en
PI
I!J
35
oX
I
-4'
ci -4'
0.001
P < 0.001
Fig. 1. Graphic representation of growth dynamics in the human fetal liver parenchyma (appropriate for gestational age fetuses). Main components only, VVi = volume density (%). Table 1. Volume density (%) of basic architectonic components of the human fetal liver parenchyma Component
Hepatocytes Sinusoids Extralobular tissue Extralo bular tissue Connective tissue Bile ducts Portal veins (inc!. TPV) Hepatal veins (inc!. THV) Hepatal arteries (inc!. THA)
25 th-29 th week of gestation
30 th-34 th week of gestation
Mean
S. D.
Mean
S. D.
44.66 48.47 6.77
1.88 2.70 2.56
50.05 43.40 6.52
1.57 1.26 1.56
3.78 0.49 1.51 0.74 0.25
1.1145 0.2954 0.7581 0.3341 0.0887
3.16 0.37 1.56 1.06 0.37
0.7361 0.1637 0.3298 0.1973 0.1190
Table 2. Volume density (%) of basic architectonic components of the human fetal liver parenchyma Component
Hepatocytes Sinusoids Extralobular tissue Extralobular tissue Connective tissue Bile ducts Portal veins (inc!. TPV) Hepatal veins (incl. THV) Hepatal arteries (inc!. THA) 13 Exp. Path. 22, H. 3
35 th-39 th week of gestation
40 th-42 nd week of gestation
Mean
S. D.
Mean
S. D.
54.85 36.99 8.14
2.48 2.85 1.43
59.95 32.48 7.51
2.86 2.20 1.91
3.49 0.82 1.73 1.48 0.62
0.4754 0.2842 0.3067 0.2137 0.1634
2.70 0.95 1.70 1.47 0.69
0.4330 0.5063 0.4477 0.2731 0.2272
189
HEPATOCYTES
• Praematuritas
•
y "' 1,008x + 18
rxy • 0,96 pc 0,001
o Small for date
y
= O,8x
+ 17.7
rxy = 0.75 Pc 0.01
25
30
40 Gest. week
35
Fig. 2. Graphic representation of growth dynamics of hepatocytic population in the developing human fetal liver. Black points = appropriate for gestational age fetuses. Empty points = intra-uterine growth retarded (small for gestational age) fetuses. VVi = volume density (%):,Regression lines for both groups. • Praematuritas y= -1,07x + 77.04
rxy =- 0.94 pc 0,001
o Small for date
40
•
30
30
• • •
SINUSOIDS
25
o
35
y =- O. 59x + 68.49 rxy = - 0.5 pc 0.1
• 40 Gest.week
Fig. 3. Graphic representation of growth dynamics of sinusoidal network in the developing human fetal liver. Black points = appropriate for gestational age fetuses. Empty points = intra-uterine growth retarded (small for gestational age) fetuses. VVi = volume density (%). Regression lines for both groups.
II. Intra-uterine growth retarded fetuses (small for gestational age) Here the livers from intra-uterine growth retarded fetuses were investigated and compared with the values of the previous group (physiologically developed fetuses). The rise of hepatocytic population values was also noted, however significantly slower in comparison with the physiologically developed counterparts. The inverse picture wa.s also disclosed in values for the sinusoidal network. There were only minor differences in the values for extralobular spaces, statistically not significant.
190
Discussion ROHR et al. (1976) had performed stereological analysis of the liver parenchyma taken from 4 young adult healthe volunteers by needly biopEY. These authors stated that in the liver of a young, healthy person about 80 volume per cent is represented by liver cell population, and the rest by extrahepatocytic spaces. In ROHR'S work the liver tissue was taken from about 25-year-old persons, in ours the liver tisme is taken from the stillborn fetuses. Although the differences between the biopsy and autopsy material should be kept in mind, nevertheless the differences between our numeric values and those of ROHR et al. (1976) are easily seen. The influence of circulation and intrasinusoidal blood pressure on shaping the architecture of liver parenchyma is evident. On the other hand, the situation will somewhat change after death, when circulation has stopped. Thus it seems that the values from biopsy and autopsy material are almost incomparable. The main purpose of our work was to find developmental trends in human fetal livers during the terminal period of intra-uterine life up to the term of delivery. In this respect our material could be considered homogeneous, having in mind the systematic errors, common when applying mathematical methods in biological material investigation. It is evident, that circulatory changes after the birth will transform the structural intra parenchymatous organization of the liver. For our work this is of no importance when ascertaining the growth tendencies in fetal livers during intra-uterine life only. Anyway, the lower volume density of hepatocytes in neonates is evident when comparing with the adult, regardless the neonate was born in term and apparently fully mature. This difference is going to be even more pronounced in the lower weight group of prematurely born neonates. A quantitatively determined retardation of liver development in the group of intra-uterine growth retarded fetuses has been also found. Many pathological factors may cause premature delivery before an optimal physiological end of gestation. When this happens, the immature fetus suddenly finds himself in the "ex utero" environment, handicapped by morphologically determined immaturity of various organs so important for his survival, including the liver. The risk of neonatal hypoglycemia, which occurs shortly after the birth is clinically a well known fact. It is also known, that the more premature or intra-uterine growth retarded the newborn is, the more serious hypoglycemia occurs (KNOBLOCH et al. 1967; LUBCHENCO and BARD 1971). In cases of untreated hypoglycemia the permanent brain damage may develop (CHASE et al. 1973). When interpreting the neonatal hypoglycemia, despite the peripartal stress and glycogen consuming hypoxia, attention should be focussed also on the insufficient glycogen reserves in neonatal liver, as well as the immature enzymatic apparatus of the liver cell as such. We do consider this statement to be in a good coincidence with our findings of deficit in volume density of hepatocytes, particularly in neonates of lower birth weight categories. This deficit is even higher in the group of intra-uterine growth retarded fetuses. This finding could be perhaps one of the possible explanatiom of dangerous hypoglycemia in such a kind of neonates, which represents one of the major risks for those babies in early postnatal life.
Literature BESEDA, A., (~uantitative evaluation of the small intestine relief in newborns (Slov.). Bratisl. lek. Listy 62, 257-384 (1974). HISLOP, A., and 1. REID, Development of the acinus in the human lung. Thorax 29, 90-94 (1974). CHASE, H. P., P. A. MARLOW, C. S. DABIERE and N. N. WELCH, Hypoglycemia and brain development. Pediatrics 02, 513-520 (1973). KNOBLOCH, H., J. F. SOTOS, E. S. SHERARD, W. A. HODSON and R. A. WEHE, Prognostic and etiologic factors in hypoglycemia. J. Pediatr. 70, 876-884 (1967). LUBCHENCO, L. 0., and H. B,\RD, Incidence of hypoglycemia in newborn infants classified by birth weight and gestational age. Pediatrics 47, 831-838 (1971). NAEYE, R. L., Fetal lung and kidney maturation in abnormal pregnancies. Arch. Pathol. 99, 533-535 (1975).
PLANK, J., Morphologische Befunde in nicht beatmeten, nicht retrahierten Lungen des Neugeborenen. Vir chows Arch. Abt. A Path. Anat. 338, 245-260 (1965). 13*
191
PLANK, J., A morphological contribution to the development of the humanl ung: observations in the non-retracted lung. Ciba Found. Symp. on Development of the Lung, London, November 1965. ~dit.: DE REUCK, A. V. S., and R. PORTER. J. and A. Churchill Ltd., London 1967, pp. 156-165. - Uber die kongenitale alveolare Dysplasie. Morpho!. Jhrb. 111, 258-264 (1967). - and A. BESEDA, Relief picture of the small intestine mucosa in newborns (Slov.). Bratis!. lek. Listy 54, 275-280 (1970). - The development of the renal corpuscle. Acta Morpho!. Acad. Sci. Hung. Supp!. XIV, 107 (1973). - and M. BENCAT, Evaluation of kidney maturity in newborns (Slov.). Bratis!.lek. Listy 71,16-25 (1979). - and F. NOVOMESKY, Stereologic picture of the developing liver in stillborn human fetuses in the terminal stage of gestation (Slov.). Bratis!. lek. Listy 73, 324-331 (1980). ROHR, H. P., J. LUTHY, F. GUDAT, M. OBERHOLZER, C. GYSIN and L. BIANCHI, Stereology of liver biopsies from healthy volunteers. Virchows Arch. Abt. A Path. Anat. and Histoi. 371, 231-263 (1976). WEIBEL, E. R., and D. M. GOMEZ, A principle for counting tissue structures on random sections. J. Appi. Physiol. 17, 343-348 (1962). - and H. ELIAS, Introduction to stereologic principles. In: Quantitative methods in morphology. Proe. 8th Int. Congr. Anatom., Wiesbaden 1965. Edit.: WEIBEL, E. R., and H. ELIAS. Springer Verlag, Berlin-Heidelberg 1967, pp. 89-98. - G. S. KISTLER and W. F. SCHERLE, Practical stereological methods for morphometric cytology. J. Cell. Bio!. 30, 23-38 (1966). - W. STAUBLI, F. A. HESS and H. R. GNAGI, Correlated morphometric and biochemical studies on the liver cell. J. Cell. BioI. 42, 68-91 (1969). - Quantitation in morphology: possibilities and limits. Beitr. Path. Hiii, 1-7 (1975).
192
Developmental trends of liver parenchyma in the terminal period of gestation: a stereological approach By F. NOVOMESKY, J. PLANK and A. LEV elK With 3 figures (Received August 26, 1981) Address for correspondence: F. NOVOMESKY, M.D.C.Sc., Department of Pathology, Faculty of Medicine, University Hospital, Kollarova 10, CS - 03659 Martin, 0SSR Key words: liver development; intra-uterine growth retardation; stereology; gestation; fetus at risk; portal vein; hepatal vein; hepatal arterial branches; human
Summary The aim of the presented study was to establish the baseline data concerning the volume of basic architectonic components of human fetal liver parenchyma. The stereological measuring principles of the point-counting method were used. The livers of 38 appropriate for ges.tational age fetuses, and 12 small for gestational age fetuses were measured. All fetuses investigated were stillborns. A lower volume density of hepatocytic popUlation was found in full-term mature fetuses, when compared with the adults. A lower volume density of hepatocytes has been also disclosed in intra-uterine growth retarded fetuses, when compared with their physiologically developed counterparts of the same gestational age. den~ity
Introduction The increasing importance of clinical entity "fetus at risk" has drawn the attention to disturbances of development and maturation of the human fetus. From this point of view the works of PLANK: (1965, 1967 a, 1967b, 1973), PLANK and BEN CAT (1979), HISLOP and REID (1974), and NAEYE (1975) concerning the normal and abnormal development of the lung and kidney, and PLANK and BESEDA (1970), and BESEDA (1974) concerning the maturation of the gut are of a great importance. However, the quantitative aspect of the dynamics of the liver development has not yet been determined. Knowing this, we have tried to find by stereological measurements the quantitatively determined morphological criteria (base-line data) of the maturation process of growing liver parenchyma in physiologically developed human fetuses (appropriate for gestational age) of various stages of maturity (PLANK and NOVOMESKY 1980). Those data were then compared with the same data obtained in the group of intra-uterine growth retarded (small for gestational age) fetuses.
lvIaterial and Methods The livers of 38 human fetuses classified both clinically and morphologically as appropriate for their gestational age, and 12 livers of fetuses classified as intra-uterine growth retarded were investigated. The range of gestational age of all fetuses was between the 25th and 42nd week of intra-uterine life. All fetuses were stillborns in attempt to avoid circulatory changes in the livers after birth. Only the fetuses who died shortly ante partum or intra partum were chosen because of our intention to obtain the material without structural changes due to autolytic process. The estimation of the time of death was perhaps the major problem when completing the group of stillborns to be investigated. Here we were almost completely dependent on the clinical informations. Intra partum deaths of the fetuses might happen rather rarely in the obstetric practice, and most of the ante partum died fetuses were yet autolysed. In its consequence, this reality had considerably reduced our group of stillborns chosen for investigation. The standard excisions from the left liver lobe were taken in every suitable
187
ease. The exeisions passed through the normal histological processing cycle and were stained by hematoxylin-eosin and van Gieson method, which proved to be suitable for our purposes. All slides were examined thoroughly in the light microscope with the aim to eliminate all cases with the slightest signs of autolysis. For the stereological analysis the point-counting method according to WEIBEL (1966, 1967) was chosen. This method had allowed us to estimate the volume density of each basic architectonic component of liver parenchyma, e.g. hepatocytic population, vascular sinusoidal network, and so-called extralobular spaces. Endothelial sinusoidal lining, Kupffer cells, and hemopoietic elements were included within the values for sinusoidal network as such. Extralobular spaces were further divided as follows: 1. Connective tissue 2. Bile ducts 3. Portal vein branches (inci. terminal portal venules) 4. Hepatal vein branches (inci. terminal hepatal venules) 5. Hepatal arterial branches. The ocular grid (WILD®) was used for the point-counting measuring process. This grid consists of 42 test points arranged in a hexagonal manner. The ocular grid was permanently installed in the normal light microscope, and the specimen was driven on the stage of the microscope semiautomatically by an ELTINOR driving device (VEB Carl Zeiss JENA). This driving system completely supressed the subjectivism in the measuring process, and the basic condition of stereological measurement concerning the random selection of components to be measured was also fulfilled. When the conditions described are strictly kept, it can be stated after measuring the sufficient surface of the specimen, that the fraction of points which "hit" one or another component of liver parenchyma represents the equivalent volume density of this component in the liver tissue as a three-dimensional structure. In every suitable section of the liver parenchyma 2,100 test points were counted (50 fields of the ocular grid) while strictly keeping all necessary rules of stereological analysis and its mathematical evaluation described elsewhere (WEIBEL 1962, 1969, 1975). The physiologically developed appropriate for gestational age fetuses were divided into four subgroups according to their increasing gestational age, as follows: 1. 25th-29th week of gestation: 17 cases 2. 30th-34th week of gestation: 9 cases 3. 35th-39th week of gestation: 7 cases 4. 40th-42nd week of gestation: 5 cases. The group of intra-uterine growth retarded (lUG R) fetuses was naturally heterogeneous and its subdivision was as follows: 1. 25th-29th week of gestation: no suitable case 2. 30th-34th week of gestation: 4 cases 3. 35th-39th week of gestation: 6 cases 4. 40th-42nd week of gestation: 2 cases. In the group of intra-uterine growth retarded fetuses all major congenital anomalies were excluded, and the presumable causes of intra-uterine growth retardation were as follows: 1. 32nd gest.week: Unwed mother, causes of IUGR not clear 2. 33rd gest.week: heavy smoking habit of the mother in pregnancy 3. 34th gest. week: severe viral febrile infection of the mother in pregnancy 4. 34th gest. week: single umbilical artery 5. 35th gest.week: minor fetal congenital heart anomaly 6. 35th gest.week: triploidismus 69 7. 37th gest.week: by pregnancy induced hypertony 8. 37th gest. week: hypoplastic uterus, partus per sectione 9. 38th gest.week: by pregnancy induced hypertony 10. 39th gest.week: causes of IUG R not clear 11. 40th gest.week: 35 years old primipara, causes of IUGR not clear 12. 42nd gest.week: obesity of the mother, causes of IUGR not clear.
Results I. Physiologically developed fetuses appropriate for gestational age Here the livers from physiologically developed fetuses were investigated only. The hepatocytic population was of the main interest, an almost continuous rise was found in volume density of hepatocytes, together with increaeing gestational age of the fetus. Mirror-like decrement of sinusoidal volume density was also noted. There were no statistically significant differences in values for extralobular spaces, hence these values are excluded from the diagram (fig. 1). All values were found to be significant even statistically.
188
VVi
HEPATOCYTES
SINUSOIDS
60
en
N
It'i
N
~
50
ci
PI
oX
C!J ~
It'i
PI
...:en
40
enN
~
g I
I
It'i N
P
<
I!J
N -4'
I
I
PI
I
~
...: en
8.
N -4'
ci
CI
enPI Iri
en
PI
I!J
35
oX
I
-4'
ci -4'
0.001
P < 0.001
Fig. 1. Graphic representation of growth dynamics in the human fetal liver parenchyma (appropriate for gestational age fetuses). Main components only, VVi = volume density (%). Table 1. Volume density (%) of basic architectonic components of the human fetal liver parenchyma Component
Hepatocytes Sinusoids Extralobular tissue Extralo bular tissue Connective tissue Bile ducts Portal veins (inc!. TPV) Hepatal veins (inc!. THV) Hepatal arteries (inc!. THA)
25 th-29 th week of gestation
30 th-34 th week of gestation
Mean
S. D.
Mean
S. D.
44.66 48.47 6.77
1.88 2.70 2.56
50.05 43.40 6.52
1.57 1.26 1.56
3.78 0.49 1.51 0.74 0.25
1.1145 0.2954 0.7581 0.3341 0.0887
3.16 0.37 1.56 1.06 0.37
0.7361 0.1637 0.3298 0.1973 0.1190
Table 2. Volume density (%) of basic architectonic components of the human fetal liver parenchyma Component
Hepatocytes Sinusoids Extralobular tissue Extralobular tissue Connective tissue Bile ducts Portal veins (inc!. TPV) Hepatal veins (incl. THV) Hepatal arteries (inc!. THA) 13 Exp. Path. 22, H. 3
35 th-39 th week of gestation
40 th-42 nd week of gestation
Mean
S. D.
Mean
S. D.
54.85 36.99 8.14
2.48 2.85 1.43
59.95 32.48 7.51
2.86 2.20 1.91
3.49 0.82 1.73 1.48 0.62
0.4754 0.2842 0.3067 0.2137 0.1634
2.70 0.95 1.70 1.47 0.69
0.4330 0.5063 0.4477 0.2731 0.2272
189
HEPATOCYTES
• Praematuritas
•
y "' 1,008x + 18
rxy • 0,96 pc 0,001
o Small for date
y
= O,8x
+ 17.7
rxy = 0.75 Pc 0.01
25
30
40 Gest. week
35
Fig. 2. Graphic representation of growth dynamics of hepatocytic population in the developing human fetal liver. Black points = appropriate for gestational age fetuses. Empty points = intra-uterine growth retarded (small for gestational age) fetuses. VVi = volume density (%):,Regression lines for both groups. • Praematuritas y= -1,07x + 77.04
rxy =- 0.94 pc 0,001
o Small for date
40
•
30
30
• • •
SINUSOIDS
25
o
35
y =- O. 59x + 68.49 rxy = - 0.5 pc 0.1
• 40 Gest.week
Fig. 3. Graphic representation of growth dynamics of sinusoidal network in the developing human fetal liver. Black points = appropriate for gestational age fetuses. Empty points = intra-uterine growth retarded (small for gestational age) fetuses. VVi = volume density (%). Regression lines for both groups.
II. Intra-uterine growth retarded fetuses (small for gestational age) Here the livers from intra-uterine growth retarded fetuses were investigated and compared with the values of the previous group (physiologically developed fetuses). The rise of hepatocytic population values was also noted, however significantly slower in comparison with the physiologically developed counterparts. The inverse picture wa.s also disclosed in values for the sinusoidal network. There were only minor differences in the values for extralobular spaces, statistically not significant.
190
Discussion ROHR et al. (1976) had performed stereological analysis of the liver parenchyma taken from 4 young adult healthe volunteers by needly biopEY. These authors stated that in the liver of a young, healthy person about 80 volume per cent is represented by liver cell population, and the rest by extrahepatocytic spaces. In ROHR'S work the liver tissue was taken from about 25-year-old persons, in ours the liver tisme is taken from the stillborn fetuses. Although the differences between the biopsy and autopsy material should be kept in mind, nevertheless the differences between our numeric values and those of ROHR et al. (1976) are easily seen. The influence of circulation and intrasinusoidal blood pressure on shaping the architecture of liver parenchyma is evident. On the other hand, the situation will somewhat change after death, when circulation has stopped. Thus it seems that the values from biopsy and autopsy material are almost incomparable. The main purpose of our work was to find developmental trends in human fetal livers during the terminal period of intra-uterine life up to the term of delivery. In this respect our material could be considered homogeneous, having in mind the systematic errors, common when applying mathematical methods in biological material investigation. It is evident, that circulatory changes after the birth will transform the structural intra parenchymatous organization of the liver. For our work this is of no importance when ascertaining the growth tendencies in fetal livers during intra-uterine life only. Anyway, the lower volume density of hepatocytes in neonates is evident when comparing with the adult, regardless the neonate was born in term and apparently fully mature. This difference is going to be even more pronounced in the lower weight group of prematurely born neonates. A quantitatively determined retardation of liver development in the group of intra-uterine growth retarded fetuses has been also found. Many pathological factors may cause premature delivery before an optimal physiological end of gestation. When this happens, the immature fetus suddenly finds himself in the "ex utero" environment, handicapped by morphologically determined immaturity of various organs so important for his survival, including the liver. The risk of neonatal hypoglycemia, which occurs shortly after the birth is clinically a well known fact. It is also known, that the more premature or intra-uterine growth retarded the newborn is, the more serious hypoglycemia occurs (KNOBLOCH et al. 1967; LUBCHENCO and BARD 1971). In cases of untreated hypoglycemia the permanent brain damage may develop (CHASE et al. 1973). When interpreting the neonatal hypoglycemia, despite the peripartal stress and glycogen consuming hypoxia, attention should be focussed also on the insufficient glycogen reserves in neonatal liver, as well as the immature enzymatic apparatus of the liver cell as such. We do consider this statement to be in a good coincidence with our findings of deficit in volume density of hepatocytes, particularly in neonates of lower birth weight categories. This deficit is even higher in the group of intra-uterine growth retarded fetuses. This finding could be perhaps one of the possible explanatiom of dangerous hypoglycemia in such a kind of neonates, which represents one of the major risks for those babies in early postnatal life.
Literature BESEDA, A., (~uantitative evaluation of the small intestine relief in newborns (Slov.). Bratisl. lek. Listy 62, 257-384 (1974). HISLOP, A., and 1. REID, Development of the acinus in the human lung. Thorax 29, 90-94 (1974). CHASE, H. P., P. A. MARLOW, C. S. DABIERE and N. N. WELCH, Hypoglycemia and brain development. Pediatrics 02, 513-520 (1973). KNOBLOCH, H., J. F. SOTOS, E. S. SHERARD, W. A. HODSON and R. A. WEHE, Prognostic and etiologic factors in hypoglycemia. J. Pediatr. 70, 876-884 (1967). LUBCHENCO, L. 0., and H. B,\RD, Incidence of hypoglycemia in newborn infants classified by birth weight and gestational age. Pediatrics 47, 831-838 (1971). NAEYE, R. L., Fetal lung and kidney maturation in abnormal pregnancies. Arch. Pathol. 99, 533-535 (1975).
PLANK, J., Morphologische Befunde in nicht beatmeten, nicht retrahierten Lungen des Neugeborenen. Vir chows Arch. Abt. A Path. Anat. 338, 245-260 (1965). 13*
191
PLANK, J., A morphological contribution to the development of the humanl ung: observations in the non-retracted lung. Ciba Found. Symp. on Development of the Lung, London, November 1965. ~dit.: DE REUCK, A. V. S., and R. PORTER. J. and A. Churchill Ltd., London 1967, pp. 156-165. - Uber die kongenitale alveolare Dysplasie. Morpho!. Jhrb. 111, 258-264 (1967). - and A. BESEDA, Relief picture of the small intestine mucosa in newborns (Slov.). Bratis!. lek. Listy 54, 275-280 (1970). - The development of the renal corpuscle. Acta Morpho!. Acad. Sci. Hung. Supp!. XIV, 107 (1973). - and M. BENCAT, Evaluation of kidney maturity in newborns (Slov.). Bratis!.lek. Listy 71,16-25 (1979). - and F. NOVOMESKY, Stereologic picture of the developing liver in stillborn human fetuses in the terminal stage of gestation (Slov.). Bratis!. lek. Listy 73, 324-331 (1980). ROHR, H. P., J. LUTHY, F. GUDAT, M. OBERHOLZER, C. GYSIN and L. BIANCHI, Stereology of liver biopsies from healthy volunteers. Virchows Arch. Abt. A Path. Anat. and Histoi. 371, 231-263 (1976). WEIBEL, E. R., and D. M. GOMEZ, A principle for counting tissue structures on random sections. J. Appi. Physiol. 17, 343-348 (1962). - and H. ELIAS, Introduction to stereologic principles. In: Quantitative methods in morphology. Proe. 8th Int. Congr. Anatom., Wiesbaden 1965. Edit.: WEIBEL, E. R., and H. ELIAS. Springer Verlag, Berlin-Heidelberg 1967, pp. 89-98. - G. S. KISTLER and W. F. SCHERLE, Practical stereological methods for morphometric cytology. J. Cell. Bio!. 30, 23-38 (1966). - W. STAUBLI, F. A. HESS and H. R. GNAGI, Correlated morphometric and biochemical studies on the liver cell. J. Cell. BioI. 42, 68-91 (1969). - Quantitation in morphology: possibilities and limits. Beitr. Path. Hiii, 1-7 (1975).
192