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The content of urea and activity of arginase in the brain and liver have been determined in squirrels falling into hibernation and in rats with an artificial decrease of the body temperature. It is shown that the intensity of urea synthesis under hypothermia (20, 10 degrees C) in the studied organs of animals falling into hibernation remains at high level in contrast to animals without such adaptation.
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With the help of thermometry and general calorimetry, changes in the heat exchange were determined in the non-hibernating mammals (rats) upon their getting out of artificial deep hypothermia (the temperature in the rectum was 22-24 degrees C) at the temperature in the calorimeter chamber 22 degrees C. An attempt was made to find out what part of the heal production during animal self-warming is used for increasing its body temperature and what part of the heat production is released to the environment by the animal. The experiments revealed a complex relationship between the body temperature, the heat loss, and the total heat production during the animal self-warming. The result was that the total heat production first increased and, after reaching the maximum, decreased gradually. The experiments showed that during two and more hours of observation the body temperature did not reach the starting level, the same was true for the total heat production, which was the sum of the heat loss and the heat production spent for warming the animal body.
Essential seasonal changes are found in the total activity of phosphorylase and the activity of its forms in the Rana ridibunda tissues. They are mostly pronounced in the liver and myocardium tissues. A week hibernation (2-4 degrees C) and artificial hypothermia (2-4 degrees C) of the same duration cause changes of different direction in the phosphorylases a and b ratio in the musculus trapezius and myocardium of frogs. Healing after hypothermia, as distinct from heating after hibernation, increases the enzyme total activity in all the tissues under study as well as the phosphorylase alpha activity in the skeletal muscles and myocardium. When the animal awakes from hibernation the enzyme activity increases only in the liver tissue due to the inactive form.
In ovariectomized adult female macaque monkeys, cannulae were affixed bilaterally to the skull for intracerbroventricular injection. Baseline temperature, heart rate, food and water intakes were monitored in each animal after it had been acclimatized to a primate restraining chair. Lyophilized serum albumin fractions extracted from the blood of hibernating woodchucks or summer active, nonhibernating woodchucks were reconstituted in an artificial CSF. Following the intracerebroventricular injection of 3.0 to 4.0 mg of hibernating woodchuck albumin (HWA) in a volume of 300 to 400 microliters, a decline in the temperature of the monkey occurred which varied in magnitude and duration. A marked inhibition of food intake, accompanied by a decline in prandial water intake, persisted for 24 to 36 hours. This hypophagia was due mainly to a reduction in the number of feeding episodes during the periods of observation. Although heart rate declined intermittently, respiratory rates remained unchanged. Summer active woodchuck albumin (SAWA) or bovine serum albumin (BSA) given in the identical range of doses, as well as artificial CSF, exerted little or no effect either on body temperature of the primate or on its food intake. These results demonstrate for the first time that a plasma "trigger" factor, obtained from a hibernating animal in torpor, exerts a direct physiological action on the brain of a mammal which is incapable of entering into hibernation. Vital metabolic, thermoregulatory and other control processes mediated by diencephalic and other systems in the CNS are directly suppressed by the "trigger" factor. The clinical implications of these findings are presented.
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Golden-mantled ground squirrels (Spermophilus lateralis) are herbivores that hibernate during winter. Although little is known about the nutritional/physiological constraints on hibernation, numerous studies have demonstrated that increasing the amount of linoleic acid (a polyunsaturated fatty acid) in the diet enhances hibernation. This is probably because high linoleic acid diets reduce the melting points of the depot fats produced for hibernation which makes them more metabolizable at low body temperatures. This suggests that a major limitation on hibernation may be obtaining enough linoleic acid in the diet for proper hibernation. In all previous studies, however, the amount of linoleic acid in the diets of free-ranging animals was either not considered, or the range of dietary linoleic acid contents in the experiments was less than that of natural diets. It is thus not known whether the amount of linoleic acid available to hibernators under natural conditions actually limits their torpor patterns. A series of laboratory feeding and hibernation experiments were conducted with S. lateralis and artificial diets with different linoleic acid contents that were either below or above the linoleic acid content of the natural diet. The results demonstrated that when dietary linoleic acid contents are either below or above natural levels, hibernation ability is greatly reduced. Hibernation ability was reduced when the squirrels were maintained on a high linoleic acid diet probably by the production of toxic lipid peroxides in brown adipose tissues. The results indicate that there is an optimal level of dietary linoleic acid for proper hibernation, and this is equal to that of the natural diet.(ABSTRACT TRUNCATED AT 250 WORDS)
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1. Uptake of [3H]uridine into the nucleotide precursor pool after intraventricular injection occurs with the same intensity in the brain of torpid and normothermic awakened ground squirrels. This indicates that the membrane uridine transporters and uridine kinases operate in the hibernator's brain in a hypothermia-tolerant way. 2. Utilization of the [3H]uridine pool for synthesis of the rapidly labelled RNA in the brain of torpid ground squirrels falls more than eight times against RNA labelling in the brain of the active animals between bouts of hibernation. 3. Two hours from the beginning of the artificially provoked awakening, RNA uridine incorporation in the brain of ground squirrels has risen 6.5 times. 4. Drastic changes in [3H]uridine RNA labelling under the stable uridine uptake exclude the precursors and energy supply as the main factors determining changes in intensity of the brain RNA synthesis in the different stages of hibernation.
The relationships between the end of hibernation and testicular and thyroid endocrine recrudescence were tested in Vipera aspis by subjecting hibernating vipers to experimental climatic conditions. Vipers kept under artificially warmed conditions (for 3.5 hr during the day to a thermal gradient from 11 to 27 degrees) 1 month before emergence showed an increase in plasma testosterone before vipers exposed to natural conditions (outdoor enclosures) did. The use of different photoperiodic conditions, long, LD 12:12, and short, LD 8:16, shows that photoperiod length has no effect on this increase. For vipers kept under prolonged hibernation (under a uniform temperature of 5 degrees or exposed to natural conditions at the northern limit of the species' distribution), testicular endocrine recrudescence was observed as soon as the first emergence only for the vipers placed at the northern range limit. Whatever the conditions, experimental or natural, the emergence of vipers always corresponds to a weight loss correlated with the increase of plasma thyroxine level. The relationship between the end of hibernation and testicular and thyroid endocrine recrudescence is discussed.
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Under natural and artificial conditions, Alpine marmots (Marmota marmota) are true hibernators with a single breeding season starting immediately upon emergence from hibernation. Over three mating and breeding seasons, hormonal and mating patterns of colony-housed reproductive female marmots were investigated after exit from hibernation. Blood samples were taken for progesterone, oestrogen and relaxin assays with parallel ultrasound investigations. Copulations were observed from the first day after exit from hibernation until the end of pregnancy and reached a maximum number on day 37 before parturition. Mating behaviour was observed between the dominant animals as well as between dominant and subdominant group members. In the first week after exit from hibernation, plasma progesterone was detected in half of the animals. During the third week, progesterone concentrations were significantly higher in pregnant than in non-pregnant animals or animals that had aborted. Immediately after emerging from hibernation, all successfully mated females showed higher serum relaxin values than non-successfully mated animals and this increase in relaxin concentration lasted until the end of pregnancy. The total concentration of oestrogen did not differ between pregnant and non-pregnant animals. The results of this study indicate that progesterone and relaxin might be useful indicators of early pregnancy in Alpine marmots.
To identify the actual location of central endogenous opioid systems which may be involved in regulating the hibernation cycle, differences in the pattern of central methionine-enkephalin (Met-EK) immunoreactivity were compared between hibernating (body temperature, Tb = 7 degrees C) and non-hibernating (Tb = 37 degrees C) Columbian ground squirrels using the peroxidase-antiperoxidase technique. In non-hibernating animals, Met-EK-immunoreactive perikarya were observed in telencephalic (putamen, caudate nucleus, medial septum-diagonal band complex, amygdala) and diencephalic (periventricular hypothalamic nucleus, lateral hypothalamic area) regions, whereas immunoreactive fibers were found in the lateral septum, stria terminalis nucleus, various hypothalamic areas, arcuate nucleus, median eminence, thalamic intralaminar, periventricular nucleus and lateral habenular nucleus. Compared to the non-hibernating animal, a marked increase in the number of Met-EK-immunoreactive fibers was found in the lateral septal nucleus, the periventricular nucleus, the intralaminar thalamus and the paraventricular hypothalamus of hibernating ground squirrels. Since these changes in immunoreactivity were not observed in the artificially induced hypothermic ground squirrels (Tb = 7 degrees C), it is unlikely that the dissimilarity in immunoreactivity between animals from different hibernating phases is due to differences in their Tb. In combination with our previous studies, these results tend to suggest that hibernation may be brought about by an increase in endogenous opioid activity, especially in the lateral septal region.
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We present evidence that in the absence of the transfer of male gland compounds in the ejaculate as well as of behavioural male traits, such as mate guarding or harming of females, sperm itself affects female life-history traits such as hibernation success, female longevity and female fitness. Using the bumble-bee Bombus terrestris, we artificially inseminated queens (females) with sperm from one or several males and show that sire groups (groups of brother males) vary in their effects on queen hibernation survival, longevity and fitness. In addition, multiply inseminated queens always had a lower performance as compared to singly inseminated queens. Apart from these main effects, sire groups (in situations of multiple insemination) affected queen longevity and fitness not independently of each other, i.e. certain sire group combinations were more harmful to queens than others. So far, the cause(s) of these effects remain(s) elusive. Harmful male traits as detected here are not necessarily expected to evolve in social insects because males depend on females for a successful completion of a colony cycle and thus have strong convergent interests with their mates.
To investigate the effects of ionic changes possibly associated with hibernation, hippocampal slices prepared from golden hamsters were studied in artificial cerebrospinal fluid (ACSF) of variable composition (K+ 3-5 mM, Ca2+ 2-4 mM, Mg2+ 2-4 mM, pH 7.0-7.7) at temperatures of 15-20 degrees C, just above the temperature below which synaptic transmission is blocked. Population action potentials (population spikes, PSs) of CA1 pyramidal cells were evoked by stimulation of the Schaffer collaterals/commissural fibers with paired pulses (interpulse interval 50 ms, interval between pairs 30 s). The responses evoked at given temperatures were investigated as a function of extracellular ion concentrations. In ACSF containing 3 mM K+, 2 mM Ca2+ and 2 mM Mg2+, PSs could be evoked at temperatures of > approximately 16 degrees C whereas at lower temperatures synaptic transmission was blocked. The threshold temperature was slightly higher for the first (PS1) than for the second PS (PS2) evoked by paired-pulse stimulation. The slices displayed paired-pulse facilitation (PPF) at all temperatures. Elevation of [K+]o from 3 to 5 mM depressed the amplitudes of both PS1 and PS2, with a stronger effect on PS2. PPF was reduced and, at near-threshold temperatures, turned into paired-pulse depression (PPD). Elevation of [Ca2+]o from 2 to 4 mM increased the amplitude of PS1. The amplitude of PS2, in contrast, was reduced at near-threshold temperatures. PPF turned into PPD. Elevation of [Mg2+]o from 2 to 4 mM reduced the amplitudes of both PS1 and PS2, with a stronger effect on PS1. Accordingly, PPF was increased. Acidification by 0.3 pH units strongly depressed the amplitudes of PS1 as well as PS2 and increased PPF. Alkalization by 0.4 pH units had only weak effects in the opposite direction. Changes in the ionic composition comparable to those investigated in the present study presumably occur in the brain interstitium of hamsters during entrance into hibernation. According to our results, such changes depress synaptic transmission at low temperatures in the hamster hippocampus in vitro. This modulation may be important for the regulation of neuronal activity during entrance into hibernation.
A short-term cooling of adult rats and gophers up to 30, 25 and 20 degrees C is accompanied by a rise of the glucose level in blood. No dependence is found between lowering the body temperature drop and degree of glycaemia. Prolongation of hypothermia of 30 and 20 degrees C up to 3 h causes (as compared to the control) a decrease in the glucose amount in blood of gophers but not in the rats. The cooling of the eye-opening, month and adult rats up to 20 degrees C is accompanied by a significant increase in the content of glucose in the brain and skeletal muscles. Simultaneously in the eye-opening and adult animals, contrary to the month ones, the level of glucose in the liver and blood rises. The content of glucose in the brain of the normothermal gophers (61.2 mg.) is 3,4 times as high as in the rat brain. At all the studied stages of artificial hypothermia as well as at 15 and 30-day hibernation (5 degrees C) the amount of glucose of the gopher brain remains at a relatively high level (41.6-101.5 mg%).