- Email: [email protected]
Role of core temperature in the pathogenesis of gastric erosions in a spinal rat model
92
ABSTRACTS:
SURVIVAL
(Supported by the Deutsche Forschungsgemeinschaft, Wu 63/5).
24. Cheyne-Stokes Breathing Pattern as Respiratory Adaptation to Deep Hibernation Hypothermia. H. TAHTI,
M. NIKINMAA,
AND A. SOIVIO
(De-
partment of Biomedical Sciences, University of Tampere, and Division of Physiology, Department of Zoology, University of Helsinki, Finland). Periodic or Cheyne-Stokes respiration is a sensitive indicator of deep undisturbed hibernation hypothermia. Hedgehogs (Erinaceus europaeus L.) hibernating at an ambient temperature of 4°C show most clear Cheyne-Stokes respiration with longapnoeic periods (about 60 min) and short breathing periods (3-5 min). Disturbances (mechanical disturbances, suffcient changes in ambient temperature, and in air CO, or 0, concentrations) abolish this type of respiration. The oscillations of pH, pCO,, PO,, and blood pressure (BP) during various phases of CheyneeStokes rhythm have been reported previously by Tahti and Soivio (Ann. Zoo/. Fennici 12, 188-192 (1975)). Because of the very low pOp values at the end of apnoeic periods, it seems that the hypothermic hedgehog is able to use almost all the oxygen present in the blood. The results suggest that pCOZ or pH is the main regulator in the Cheyne-Stokes rhythm. Ventilatory stability is probably preserved by the chemical drive in hibernating hedgehogs. A theoretical attempt is made to find reasons for periodic breathing pattern in a hibernating hedgehog and to evaluate it as an adaptation mechanism to hibernation hypothermia. 25. Tympanic Temperature During REM Sleep in Humans Exposed to Cold. JOSEPH W. PALCA, JAMES
M.
WALKER,
AND
RALPH
J. BERCER
(Thimann Laboratories, University of California, Santa Cruz, California 95060). ThreeHubjects slept nude except for shorts on a bed made from nylon webbing. Standard electrodes for polysomnographic recordings were attached, as well as thermocouples for recording skin, rectal, and tympanic membrane temperature (TMT). Each subject spent 12 consecutive nights in the lab: 5 nights at 29°C (thermoneutrality), 5 experimental nights at 21°C (cold condition), and 2 recovery nights at 29°C. TMT is thought to be an accurate index of hypothalamic temperature, which is considered to be a critical variable in the control of thermoregulation. No consistent pattern of TMT change was seen immediately following REM onset in either cold or thermoneutral conditions. During REM periods in the cold, however, TMT increased in 16 of 18 REM periods. The mean change in temperature when the first 5 min of a REM period was compared to the last 5 min of that REM period was 0.03”C for thermoneutral conditions and O.lI”C for
IN
COLD
cold conditions. The larger increase in the cold suggests an active response during REM to cold stress conditions. Sleep stage data failed to show large decreases in REM time, although considerable individual differences were present. These results are most interesting in light of earlier animal evidence indicating that REM is essentially a poikilothermic state. Maintenance of a high brain temperature may be an important adaptive function of REM sleep in humans. 26. Nightly Torpor in the Ringed-Neck Dove: An Extension of Sleep. J. M. WALKER, L. E. WALKER,
J. W.
PALCA,
AND
R. I.
BERCER
(University of California, Santa Cruz, Santa Cruz, California 95060). Shallow torpor was induced in the dove by 3- to 6-day food deprivation over a period during which time-continuous electrophysiological and Tskin measurements were obtained. Tskln decreased 1-W below baseline nocturnal levels during the first night following food removal and returned to baseline diurnal levels the following day. Incremental I-3°C decreases occurred on subsequent nights such that on the third night of food deprivation, Tskinin one dove decreased from 39 to 30°C. The subsequent return to diurnal levels of Tsklnindicates that these nightly decreases in body temperature were-indeed torpor and not hypothermia. Decreases in Trkin occurred during the major sleep period and the change in sleep patterns accompanying decreases in Tskln paralleled those of mammals entering hibernation (Heller et al. “Strategies in Cold,” 1978). Sleep time increased whereas REM sleep decreased in conjunction with decreases in Trkln. For example, at a Tskinof 37°C sleep comprised 85% of the 12 hr dark period, with REM sleep constituting 9% of sleep time. In the same bird at aT sklnof 32.5”C, sleep comprised 95% of the dark period and REM sleep only 4% of sleep time. EEG amplitude decreased in conjunction with Tsklnbut slow wave sleep could be identified according to conventional criteria at the lowest T,,,, of 30°C. At a T,,,, of 3O”C, the record was comprised of continuous slowwave sleep. These findings point to striking similarities between sleep patterns in birds and those of mammals during torpor and entrance into torpor, and provide suppqrt for the hypothesis that slow-wave sleep and torpor are homologous. 27. Role of Core Temperature in the Pathogenesis of Gastric Erosions in a Spinal Rat Model. H. H. SIGMAN, AND A. GILLICH (Lady Davis Institute, Jewish General Hospital and McGill University, Montreal, Canada).
An association between hypothermia and gastric ulceration has been reported in cervical cord section and in restraint rat models. The present study was designed to determine this relationship in cervical (C-7)
ABSTRACTS: SURVIVAL and lumbar (L-l) spinal cord-sectioned SpragueDawley rats maintained in ambient temperatures of 23, 28, and 4°C. Rectal temperature changes were noted. The totaled lengths of gross erosions were recorded at sacrifice after 8 hr and histological examination was carried out on representative specimens. A group of IO sham-operated rats was used as controls. Significance of differences were analyzed by Student’s t tests. Cervical section rats kept at 23°C (n = 20) had a significant decrease in core temperature of 10.2 _t 4 compared to 3.9 f 2°C in those maintained at 28°C (n = IO) (P < O.Oal). Ulcer lengths totaled 21.1 mm i: 3.8 (mean 2 SEM) in the 23°C group and 1.85 mm f 0.8 in the 28°C group (P < 0.01j. Lumbar section rats kept at 4°C (n = 20) had a significant decrease in core temperature of 9.1 f 1.1 compared to 0.5 ? 0.3”C (P < 0.001) in those at 23°C (n = 10). Ulcer lengths totaled 3.05 mm + 0.7 in the first group and 0.1 mm f 0.9 in the second (P < 0.01). The data demonstrate a significant relationship between hypothermia and ulceration in the cordsectioned rat which is independent of the level of section, but dependent on ambient temperature. Recent experiments wiih instillation of antacids into cervical rat stomachs at 23°C ambient temperature have shown a significant diminution in ulcerogenesis compared to controls even though there was development of profound hypothermia in both groups. This indicates the importance of acid in ulcer production in this model (supported by Medical Research Council of Canada). 28. The Digestive System in Hibernating, Hypothermic, and Fasted S. lateralis: An Vitrastrucfural Study. D. M. TOTH (University of Oklahoma
College of Medicine, Oklahoma City 73106). In mammals which hibernate the yearly cycle is marked by dramatic seasonal changes in ingestive activity (hyperphagia in fall, fasting in winter), metabolic rate (hibernation < 1/3Oth awake) and body weight (oscillations from - 125-600 g). Previous studies have centered on physiological responses of the digestive system, but morphological alterations have remained undefined. To determine how these ingestive and metabolic fluctuations are reflected in ultrastructure, the small intestme of the ground squirrel, S. lateralis, was examined in hibernating animals and compared to tissue of euthermic, hypothermic, and fasted animals. After rapid intracardiac perfusion, jejuno-ileal segments were processed for electron microscopic examination in routine manner. As expected, the morphological features of the small intestine of hibernating animals gave evidence of profoundly decreased activity when compared to active euthermic animals. However, these changes were unlike those observed in hypothermic or fasted animals. When hibernating animals were compared to euthermic, hypothermic, or fasted animals, the Paneth cells were observed to possess smaller nuclei, with less prominent nucleoli and an increase in the proportion of heterochromatin. The
IN COLD
93
cytoplasm of the hibernators’ Paneth cells contained large numbers of free ribosomes, but the rough endoplasmic reticulum was fragmentary and poorly organized (nonlamellar). The Golgi complex was also smaller, with condensing vacuoles which were electron lucent. Both hibernating and fasted Paneth cells contained a greater number of apical secretory granules than cells from fed euthermic or hypothermic animals; however, in the hibernators’ cells the granules were more densely packed and the electron density of the matrix was more variable. The intestinal absorptive cells of hibernating animals were observed also to possess evidence of decreased activity when compared to all other conditions, i.e., fewer mitotic figures, smaller heterochromatic nuclei and, surprisingly, a smaller Golgi complex. The muciparous goblet cells of hibernators were almost indistinguishable from those of the control animals. These differences suggest that the ultrastructural changes observed in the small intestine of hibernating ground squirrels were not the direct result of fasting or hypothermia (low temperature and low oxygen consumption). SESSION 4. THERMOGENESIS IN HI3ERNATION AND COLD ADAPTATION 29. Maximum Thermogenesis in Hibernators: Magnitudes and Seasonal Variations. LAWRENCE
C. H. WANG AND BRUCEABBOTTS(Department of Zoology, University of Alberta. Edmonton, Alberta, T6G 2E9, Canada). The maximum thermogenic capabilities during acute cold exposure in various species of hibernators are measured and compared to those found in nonhibemating species for possible intrinsic differences in aerobic capacity. The effects of temperature acclimation and seasonal acclimatization on maximum thermogenesis in the hibernators are discussed and compared to those found in the nonhibernators. Seasonal differences in maximum thermogenesis and the proportion of shivering to nonshivering thermogenesis in a hibernating species are illustrated using the Richardson’s ground squirrel (Spermophifus richardsonii). In this hibernator, the rate of maximum thermogenesis appears to be relatively constant in all seasons and after temperature acclimation to 5 or 20°C. However, during the hibernating phase of the yearly cycle, the magnitude of nonshivering thermogenesis increases significantly at the expense of reduced shivering thermogenesis. It is reasoned that the increased nonshivering thermogenic capability may facilitate heat production during periodic rewarming from hibernation. The lack of seasonal and cold acclimation effects on maximum thermogenesis in this hibernator is in strong contrast to those found in the nonhibemators where maximum thermogenesis can be significantly increased after cold acclimation or winter acclimation due to enhanced nonshivering thermogenesis
ABSTRACTS:
SURVIVAL
(Supported by the Deutsche Forschungsgemeinschaft, Wu 63/5).
24. Cheyne-Stokes Breathing Pattern as Respiratory Adaptation to Deep Hibernation Hypothermia. H. TAHTI,
M. NIKINMAA,
AND A. SOIVIO
(De-
partment of Biomedical Sciences, University of Tampere, and Division of Physiology, Department of Zoology, University of Helsinki, Finland). Periodic or Cheyne-Stokes respiration is a sensitive indicator of deep undisturbed hibernation hypothermia. Hedgehogs (Erinaceus europaeus L.) hibernating at an ambient temperature of 4°C show most clear Cheyne-Stokes respiration with longapnoeic periods (about 60 min) and short breathing periods (3-5 min). Disturbances (mechanical disturbances, suffcient changes in ambient temperature, and in air CO, or 0, concentrations) abolish this type of respiration. The oscillations of pH, pCO,, PO,, and blood pressure (BP) during various phases of CheyneeStokes rhythm have been reported previously by Tahti and Soivio (Ann. Zoo/. Fennici 12, 188-192 (1975)). Because of the very low pOp values at the end of apnoeic periods, it seems that the hypothermic hedgehog is able to use almost all the oxygen present in the blood. The results suggest that pCOZ or pH is the main regulator in the Cheyne-Stokes rhythm. Ventilatory stability is probably preserved by the chemical drive in hibernating hedgehogs. A theoretical attempt is made to find reasons for periodic breathing pattern in a hibernating hedgehog and to evaluate it as an adaptation mechanism to hibernation hypothermia. 25. Tympanic Temperature During REM Sleep in Humans Exposed to Cold. JOSEPH W. PALCA, JAMES
M.
WALKER,
AND
RALPH
J. BERCER
(Thimann Laboratories, University of California, Santa Cruz, California 95060). ThreeHubjects slept nude except for shorts on a bed made from nylon webbing. Standard electrodes for polysomnographic recordings were attached, as well as thermocouples for recording skin, rectal, and tympanic membrane temperature (TMT). Each subject spent 12 consecutive nights in the lab: 5 nights at 29°C (thermoneutrality), 5 experimental nights at 21°C (cold condition), and 2 recovery nights at 29°C. TMT is thought to be an accurate index of hypothalamic temperature, which is considered to be a critical variable in the control of thermoregulation. No consistent pattern of TMT change was seen immediately following REM onset in either cold or thermoneutral conditions. During REM periods in the cold, however, TMT increased in 16 of 18 REM periods. The mean change in temperature when the first 5 min of a REM period was compared to the last 5 min of that REM period was 0.03”C for thermoneutral conditions and O.lI”C for
IN
COLD
cold conditions. The larger increase in the cold suggests an active response during REM to cold stress conditions. Sleep stage data failed to show large decreases in REM time, although considerable individual differences were present. These results are most interesting in light of earlier animal evidence indicating that REM is essentially a poikilothermic state. Maintenance of a high brain temperature may be an important adaptive function of REM sleep in humans. 26. Nightly Torpor in the Ringed-Neck Dove: An Extension of Sleep. J. M. WALKER, L. E. WALKER,
J. W.
PALCA,
AND
R. I.
BERCER
(University of California, Santa Cruz, Santa Cruz, California 95060). Shallow torpor was induced in the dove by 3- to 6-day food deprivation over a period during which time-continuous electrophysiological and Tskin measurements were obtained. Tskln decreased 1-W below baseline nocturnal levels during the first night following food removal and returned to baseline diurnal levels the following day. Incremental I-3°C decreases occurred on subsequent nights such that on the third night of food deprivation, Tskinin one dove decreased from 39 to 30°C. The subsequent return to diurnal levels of Tsklnindicates that these nightly decreases in body temperature were-indeed torpor and not hypothermia. Decreases in Trkin occurred during the major sleep period and the change in sleep patterns accompanying decreases in Tskln paralleled those of mammals entering hibernation (Heller et al. “Strategies in Cold,” 1978). Sleep time increased whereas REM sleep decreased in conjunction with decreases in Trkln. For example, at a Tskinof 37°C sleep comprised 85% of the 12 hr dark period, with REM sleep constituting 9% of sleep time. In the same bird at aT sklnof 32.5”C, sleep comprised 95% of the dark period and REM sleep only 4% of sleep time. EEG amplitude decreased in conjunction with Tsklnbut slow wave sleep could be identified according to conventional criteria at the lowest T,,,, of 30°C. At a T,,,, of 3O”C, the record was comprised of continuous slowwave sleep. These findings point to striking similarities between sleep patterns in birds and those of mammals during torpor and entrance into torpor, and provide suppqrt for the hypothesis that slow-wave sleep and torpor are homologous. 27. Role of Core Temperature in the Pathogenesis of Gastric Erosions in a Spinal Rat Model. H. H. SIGMAN, AND A. GILLICH (Lady Davis Institute, Jewish General Hospital and McGill University, Montreal, Canada).
An association between hypothermia and gastric ulceration has been reported in cervical cord section and in restraint rat models. The present study was designed to determine this relationship in cervical (C-7)
ABSTRACTS: SURVIVAL and lumbar (L-l) spinal cord-sectioned SpragueDawley rats maintained in ambient temperatures of 23, 28, and 4°C. Rectal temperature changes were noted. The totaled lengths of gross erosions were recorded at sacrifice after 8 hr and histological examination was carried out on representative specimens. A group of IO sham-operated rats was used as controls. Significance of differences were analyzed by Student’s t tests. Cervical section rats kept at 23°C (n = 20) had a significant decrease in core temperature of 10.2 _t 4 compared to 3.9 f 2°C in those maintained at 28°C (n = IO) (P < O.Oal). Ulcer lengths totaled 21.1 mm i: 3.8 (mean 2 SEM) in the 23°C group and 1.85 mm f 0.8 in the 28°C group (P < 0.01j. Lumbar section rats kept at 4°C (n = 20) had a significant decrease in core temperature of 9.1 f 1.1 compared to 0.5 ? 0.3”C (P < 0.001) in those at 23°C (n = 10). Ulcer lengths totaled 3.05 mm + 0.7 in the first group and 0.1 mm f 0.9 in the second (P < 0.01). The data demonstrate a significant relationship between hypothermia and ulceration in the cordsectioned rat which is independent of the level of section, but dependent on ambient temperature. Recent experiments wiih instillation of antacids into cervical rat stomachs at 23°C ambient temperature have shown a significant diminution in ulcerogenesis compared to controls even though there was development of profound hypothermia in both groups. This indicates the importance of acid in ulcer production in this model (supported by Medical Research Council of Canada). 28. The Digestive System in Hibernating, Hypothermic, and Fasted S. lateralis: An Vitrastrucfural Study. D. M. TOTH (University of Oklahoma
College of Medicine, Oklahoma City 73106). In mammals which hibernate the yearly cycle is marked by dramatic seasonal changes in ingestive activity (hyperphagia in fall, fasting in winter), metabolic rate (hibernation < 1/3Oth awake) and body weight (oscillations from - 125-600 g). Previous studies have centered on physiological responses of the digestive system, but morphological alterations have remained undefined. To determine how these ingestive and metabolic fluctuations are reflected in ultrastructure, the small intestme of the ground squirrel, S. lateralis, was examined in hibernating animals and compared to tissue of euthermic, hypothermic, and fasted animals. After rapid intracardiac perfusion, jejuno-ileal segments were processed for electron microscopic examination in routine manner. As expected, the morphological features of the small intestine of hibernating animals gave evidence of profoundly decreased activity when compared to active euthermic animals. However, these changes were unlike those observed in hypothermic or fasted animals. When hibernating animals were compared to euthermic, hypothermic, or fasted animals, the Paneth cells were observed to possess smaller nuclei, with less prominent nucleoli and an increase in the proportion of heterochromatin. The
IN COLD
93
cytoplasm of the hibernators’ Paneth cells contained large numbers of free ribosomes, but the rough endoplasmic reticulum was fragmentary and poorly organized (nonlamellar). The Golgi complex was also smaller, with condensing vacuoles which were electron lucent. Both hibernating and fasted Paneth cells contained a greater number of apical secretory granules than cells from fed euthermic or hypothermic animals; however, in the hibernators’ cells the granules were more densely packed and the electron density of the matrix was more variable. The intestinal absorptive cells of hibernating animals were observed also to possess evidence of decreased activity when compared to all other conditions, i.e., fewer mitotic figures, smaller heterochromatic nuclei and, surprisingly, a smaller Golgi complex. The muciparous goblet cells of hibernators were almost indistinguishable from those of the control animals. These differences suggest that the ultrastructural changes observed in the small intestine of hibernating ground squirrels were not the direct result of fasting or hypothermia (low temperature and low oxygen consumption). SESSION 4. THERMOGENESIS IN HI3ERNATION AND COLD ADAPTATION 29. Maximum Thermogenesis in Hibernators: Magnitudes and Seasonal Variations. LAWRENCE
C. H. WANG AND BRUCEABBOTTS(Department of Zoology, University of Alberta. Edmonton, Alberta, T6G 2E9, Canada). The maximum thermogenic capabilities during acute cold exposure in various species of hibernators are measured and compared to those found in nonhibemating species for possible intrinsic differences in aerobic capacity. The effects of temperature acclimation and seasonal acclimatization on maximum thermogenesis in the hibernators are discussed and compared to those found in the nonhibernators. Seasonal differences in maximum thermogenesis and the proportion of shivering to nonshivering thermogenesis in a hibernating species are illustrated using the Richardson’s ground squirrel (Spermophifus richardsonii). In this hibernator, the rate of maximum thermogenesis appears to be relatively constant in all seasons and after temperature acclimation to 5 or 20°C. However, during the hibernating phase of the yearly cycle, the magnitude of nonshivering thermogenesis increases significantly at the expense of reduced shivering thermogenesis. It is reasoned that the increased nonshivering thermogenic capability may facilitate heat production during periodic rewarming from hibernation. The lack of seasonal and cold acclimation effects on maximum thermogenesis in this hibernator is in strong contrast to those found in the nonhibemators where maximum thermogenesis can be significantly increased after cold acclimation or winter acclimation due to enhanced nonshivering thermogenesis