Endocrine cells in the large intestine epithelium in various vertebrate species

Amount of argyrophile and argentoffin endocrine cells per 1 mm2 of the large intestine mucous membrane has been counted in the turtle, pigeon, white rat and frog at various periods of their life (winter hibernation, awakening, active life). As the animal's organization becomes more complicated, the amount of the endocrine cells in the epithelium increases both in the initial and in the terminal parts of the large intestine, their amount in the terminal (rectum) part being less than in the initial one. The greatest amount of the endocrine cells is found in simmer frogs at the expense of increasing content of the elements that do not belong to the argentaffin group. The latter do not significantly change during various seasons.     

Seasonal dynamics of the gastric APUD cell count in a hibernator

Light microscopy was applied to study variation in the composition and number of apudocytes in the gastric epithelium of red-cheeked sousliks over time. During hibernation, the content of serotonin-producing EC cells was elevated. This is in agreement with serotonin involvement in the maintenance of the hibernation state. The number of non-EC cells taking part in digestion, which does not occur during hibernation, was lowered. Spring awakening was accompanied with an increase in the number of non-EC cells and the lack of significant changes in cells. In souslics, which were active in winter, the content of non-cells was high, since the animals continued feeding on, and the content of EC-cells was elevated similarly to that in hibernating animals, which could be explained by genetic dependence. The number of apudocytes in the gastric mucosa was discovered to correlate in the main with the features of their function at different seasons.     

Endocrine cells of the mucous membrane of the fundus region of the stomach of hibernating rodents]

The gastric mucous membrane was studied in the hibernating animal Citellus erythrogenys in different seasons (during 7-8 months a year the animal is in hibernation and its digestive tract is not functioning). During hibernation the general amount of enterochromaffin-like cells decreases and their composition changes: the number of active cells diminishes and that of less active cells grows. Such dynamics of cells suggests the participation of enterochromaffin-like cells of Citellus erythrogenys in the regulation of gastric secretion (in rats and mice these cells contain histamine stimulating the mucous membrane glands). The amount of true enterochromaffin cells is not sufficiently changed and they seem to be not directly related with digestion but to be producers of serotonin which (together with serotonin of the brain) takes part in sustaining the mechanisms of appearance and supporting of winter hibernation.     

Seasonal changes in phosphorylation of myosin regulatory light chains and C-protein in myocardium of hibernating ground squirrel Citellus undulatus

A comparative study concerning the extent of phosphorylation of myosin regulatory light chains and C-protein from the left ventricle of hibernating ground squirrel Citellus undulatus during the periods of hibernation and activity was carried out. During hibernation, regulatory light chains of ground squirrel were found to be completely dephosphorylated. In active animals, the share of phosphorylated light chains averages 40-45% of their total amount. The extent of phosphorylation of the cardiac C-protein during hibernation is about two times higher than that in the active state. Seasonal differences in phosphorylation of the two proteins of ground squirrel myocardium are discussed in the context of adaptation to hibernation.     

Seasonal dynamics of adrenal 11-hydroxycorticosteroid secretion in Citellus erythrogenus susliks

It has been demonstrated that during different periods of life cycle of the ground squirrels their adrenals produce various amounts of glucocorticoids. Maximum secretion of 11-oxycorticosteroids by the adrenals was noted in active period of animals (May), decreasing to the period of preparation to hibernation (August). During hibernation of the animals, 11-oxycorticosteroid secretion exhibits intrinsic endogenous rhythm. Whereas the first half of hibernation is characterized by a constant secretion (October, November, December), during the second one (from January till March) the secretion of 11-oxycorticosteroids by the adrenals increases.     

Ultrastructure of cells from the liver-endocrine pancreas system in hibernating animals

In hibernated ground squirrel (Citellus erythrogenys) during various periods of hibernation morphological changes in organs participating in insurance of energoplastic homeostasis (liver, endocrine part of the pancreas) have been followed. At the beginning of hibernation certain signs of functional strain in the liver are observed-shortening and swelling of the endoplasmic reticulum (ER) canaliculi, decreases of glycogen resources and activation of the lysosomal apparatus, as well as certain features demonstrating its decreased activity--shortening cisterns in the Golgi complex, poorly manifested granular ER, tightening of mitochondrial matrix. At a deep hibernation, the signs of strain disappear, ultrastructure of hepatocytes corresponds to a new lower level of functioning in comparison to that in the active state and at the beginning of hibernation. During these periods the structure of endocrine cells in the pancreas demonstrates certain changes in the character of functioning of the cells. Ultrastructural transformations in the liver and endocrine part of the pancreas in the ground squirrel are mutually correlated.     

Changes in cyclin and cyclin-dependent protein kinase expression in the long-tailed ground squirrel (<Emphasis Type="Italic">Spermophilus undulatus</Emphasis>) brain during hibernation and awakening

We have studied the expression of cyclins (Cicl A and Cicl B1) and cyclin-dependent protein kinases (Cdk1, Cdk2, Cdk4, and Cdk5) in the brain of the long-tailed ground squirrel (Spermophilus undulatus) during different phases of their yearly cycle of life activities. We found that the expression of protein kinases in the frontal neocortex, hippocampus, and caudal brainstem differed by from three to five times, which indicates the regional specificity of the activity of cell-cycle proteins in the brain of a hibernating animal. During the end of winter hibernation, a significant increase in the expression of Cdk1, Cdk2, and Cdk4 were found in the hippocampus, which is due to the presence of progenitor neural cells in the subgranular region of the dentate gyrus. These cells are able to produce new neurons during all of ontogenesis. Our results show that during winter hibernation and awakening, region-specific changes in the expression of cell cycle proteins occur in the brain of a long-tail ground squirrel, which provides the appropriate activity of the cell cycle during the new functional state of a hibernating animal.     

Prediction of the changes in thermodynamic stability of proteins caused by single amino acid substitutions

The functional (synthetic) activity of blood lymphocytes and bone marrow hematopoietic cells in ground squirrels was studied in different seasons and at different stages of the torpor-arousal cycle. The effect of γ-irradiation on animals in different physiological states was also studied. The synthetic activity of cells was estimated from the amount of active RNA per unit DNA in the cell (parameter α). The α values in lymphocytes were minimal in hibernating animals (January–March), reached a peak upon their complete awakening (April), slightly decreased in the summer activity period, and decreased further in the prehibernation autumn period (November). During winter arousals between torpor bouts, this parameter reached the same values as in summer. The dynamics of parameter α in bone marrow hematopoietic cells were generally similar: minimal values in November and higher between torpor bouts than in summer. The peak of synthetic activity of proliferating hematopoietic cells recorded upon awakening from hibernation in April was mainly due to the accumulation of cells in the G₁ and G₂ phases of the cell cycle, and its decrease in summer reflected prevalent transition from G₂ to mitosis and then partly to G₀. In the torpor-arousal-euthermia cycle, two stages of awakening were distinguished, differing considerably in most of the test parameters. The synthetic activity and the total number of blood and bone marrow cells in ground squirrels irradiated in the state of torpor did not differ significantly from those in nonirradiated torpid animals. The adverse effect of radiation in animals irradiated at the initial stage of awakening was lesser than in animals irradiated in the active state, whereas animals at the second stage of awakening proved more vulnerable to acute irradiation. The physiological state of ground squirrels exposed to ionizing radiation at different phases of the torpor-arousal-euthermia cycle plays a key role in the dynamics of qualitative and quantitative characteristics of blood system cells. The results of this study indicate that the hypometabolic state of ground squirrels during hibernation is a factor of protection from the impact of ionizing radiation on the whole body and on the immune system in particular.     

Macro- and micromorphological remodeling of olfactory organs throughout the ontogeny of the fire salamander Salamandra salamandra (Linnaeus, 1758)

This article studies the morphological remodeling of olfactory organs in the fire salamander (Salamandridae, Caudata), from the larval stages of ontogeny to the adult and throughout the course of the annual cycle. The fire salamander exhibits adaptations to the aquatic environment during premetamorphic life and terrestrial adaptations after metamorphosis. During adulthood, the annual activity of this species is divided into three seasonal periods: a breeding period, a nonbreeding period, and hibernation. We observed significant differences in morphology of olfactory organs between developmental stages as well as between each period within the annual cycle. For the first time in caudates, we examined the morphology of olfactory organs during the winter period (wintering larvae, hibernating adults). The results show that the remodeling of olfactory organs during the life of the fire salamander occurs both on macro- and micromorphological levels. Macromorphological ontogenetic variability includes the shape of the main olfactory chamber (MOC) and the distribution of olfactory epithelium (OE) in the MOC and in the vomeronasal organ (VNO). In larvae, the vomeronasal epithelium (VNE) is in a separate cavity, while in the post-metamorphic stages of ontogeny, the VNE occurs in the diverticulum of the MOC. In adult fire salamanders, both olfactory organs are most developed during the breeding season and reduced during hibernation. The VNE and OE in the MOC are also reduced during hibernation. Micro-morphological changes included different types/subtypes of olfactory receptor neurons (ORNs) in the OE in particular stages of ontogeny and periods within the annual cycle, for example, ciliate ORNs are present in the VNE only in the larval stages and giant ORNs occur only in nonbreeding adults. Also, there was a variable set of types of olfactory supporting cells in the VNO of the fire salamander during pre- and postmetamorphic life stages.     

An autoradiographic study of the uptake of tritiated proline by osteoblasts during hibernation

Twenty-four LSH and LVG strain golden hamsters, Mesocricetus auratus, were used. Experimental animals were maintained at 5 C and allowed to hibernate. Control animals were kept at 27 C. Six animals (3 experimental, 3 control) were injected subcutaneously with 1 microCi of 3H-proline/gm body wt. (Spec. act. 3 Ci/mM) after hibernation lasting 12 hours, 1 day, 3 days, or 7 days. Animals were killed 1 hour after injection and autoradiographs were prepared from 5 microns thick decalcified sections of femurs. A greater number of endosteal cells were labeled than periosteal cells and also exhibited a greater magnitude of labeling throughout the study. Differences between endosteal and periosteal cells both in percentage of cells labeled and magnitude of labeling were maximum in control animals and progressively decreased with increasing periods of hibernation. A reduction in synthesis of matrix proteins during the early period of hibernation was seen and was attributed to a significant reduction both in average cell activity and in the number of active cells during hibernation. The latter phenomenon apparently made a large contribution to the reduced matrical synthesis. 3H-proline uptake by osteoblasts probably reflects the reduced requirements of matrical synthesis during hibernation.     

Morphofunctional analysis of the chief (peptic) glandulocytes in the stomach of hibernating rodents

Ultrastructure of the chief gastric gland cells has been studied in the ground squirrel (Cytellus erythrogenys Brandt) at various seasons of the year. When the ground squirrel is in the active state, the cells studied do not differ from those in other animals. During winter hibernation, their activity is inhibited. During first days of awakening, the activity of the chief cells increases; the protein-synthesizing apparatus, the Golgi complex become activated, secreating granules accumulate. At the same time, the greatest number of the destroing cellular elements and discharge of the residual bodies out of the activizing cells are observed. Restoration of the normal structure in the chief cells is completed by the end of the second week. No signs demonstrating transformation of additional cells into the chief ones are revealed. Non-differentiated cells in the ground squirrel fundal glands are widely distributed along the whole length of the glandular cervix and occur even in the upper parts of its body.     

Distribution of endocrine cells in the digestive tract of Alligator sinensis during the active and hibernating period

The digestive tract is the largest endocrine organ in the body; the distribution pattern of endocrine cells varies with different pathological and physiological states. The aim of the present study was to investigate the distributed density of 5-hydroxytryptamine (5-HT), gastrin (GAS), somatostatin (SS) and vasoactive intestinal peptide (VIP) immunoreactive (IR) cells in the digestive tract of Alligator sinensis during the active and hibernating period by immunohistochemical (IHC) method. The results indicated that 5-HT-IR cells were distributed throughout the entire digestive tract, which were most predominant in duodenum and jejunum. The density increased significantly in stomach and duodenum during hibernation. GAS-IR cells were limited in small stomach and small intestine. The density decreased significantly in small stomach during hibernation, while increased in duodenum. What's more, most of the endocrine cells in duodenum were generally spindle shaped with long cytoplasmic processes ending in the lumen during hibernation. SS-IR cells were limited in stomach and small stomach. The density increased in stomach while decreased in small stomach during hibernation, meanwhile, fewer IR cells occurred in small intestine. VIP-IR cells occurred in stomach and small stomach. The density decreased in small stomach, while increased in stomach during hibernation. These results indicated that the endocrine cells in different parts of digestive tract varied differently during hibernation, their changes were adaptive response to the hibernation.     

光照黑暗循环条件下达乌尔黄鼠的冬眠模式和能量消耗

为研究冬眠季节的光照条件对贮脂类冬眠动物入眠的影响,在达乌尔黄鼠腹腔埋植体温记录元件iButton,在体重高峰后的下降阶段置于5℃和12L:12D的光照条件下,观察测定其冬眠模式和能量消耗。达乌尔黄鼠冬眠模式出现深冬眠型、少冬眠型和不冬眠型,蛰眠阵包括深冬眠阵、短冬眠阵和日眠阵。不同冬眠阵中最低体温、冬眠阵的持续时间、阵间产热的持续时间、冷却速率和复温速率差异显著;阵间产热的最高体温基本相同。平均每日能量消耗在日眠阵中最高、短冬眠阵中居中、深冬眠阵中最低。入眠时间多集中于黑暗时相,觉醒时间多集中于光照时相。本实验结果提示,在冬眠季节施加光照黑暗循环条件可减少达乌尔黄鼠冬眠的时间,升高阵间最低体温,缩短冬眠阵与阵间产热的持续时间,降低复温速率;增加冬眠期间能量消耗。入眠与觉醒受光照条件影响,具有明显的光暗节律。     

Physiological ecology of cheirogaleid primates: variation in hibernation and torpor

Torpor (i.e. the reduction of body temperature and metabolic rate for less than 24 h) and hibernation (i.e. torpor phases longer than 24 h) are among the most extreme adaptations to seasonality in primate habitats. Although widespread among mammals, this form of extreme thermoregulation is rare among primates and is reported only for species of the cheirogaleid family. Understanding their physiological ecology is crucial for many aspects of cheirogaleid socioecology like their social organization and their mating systems. This paper first provides an overview of published information on hibernation and torpor and identifies a patchy distribution for the occurrence of hibernation across genera, species and populations. Based on a review of published studies from the wild and from captivity, we then propose a possible explanation for variation in hibernation behavior among Microcebus species and populations. Accordingly, the amount of energy that can be saved during torpor early in the lean dry season, which is determined by the minimum ambient temperature will be decisive. Only where temperatures are low, early dry season torpor bouts will be long enough to save enough energy to build up fat reserves for longer bouts of hibernation. Finally, we summarize information on the causal factors for the occurrence of hibernation by analyzing sex differences within populations. Further physiological studies on other cheirogaleid species are needed to identify the phylogenetic origin of hibernation in primates.     

Nuclear changes and morphology of the epidermis in the hibernating frog

Cytochemical changes of chromatin and DNA in frog epidermal cells were correlated with some morphological features to investigate the skin physiology during hibernation in comparison with the active period. The epidermal cells of hibernating frogs showed less condensed chromatin in all the layers; a greater loss of DNA was found during the transition from the middle to the superficial layer. In the germinative layer, a lesser frequency of hyperdiploid cells and a remarkably low amount of mitoses were detected; this is accompanied by the increase of epidermal thickness and the presence of two layers of cornified cells. The slowing of tissue differentiation and cell renewal kinetics during hibernation can be related to lowered activity of the frog skin. Further, the smaller intercellular spaces as well as the scarcity of puffed ER and vacuoles may be indicative of a lower ion transport in epidermal cells during hibernation.     

Changes in renal morphology and renin secretion in the golden-mantled ground squirrel (Spermophilus lateralis) during activity and hibernation

Summary Chronological changes in renal glomerular morphology and plasma renin activity were investigated during active and hibernating periods in the golden-mantled ground squirrel Spermophilus lateralis. The objective of this study was to determine whether the glomerular endothelium, visceral epithelium (podocytes), basement membrane, mesangial cells, proximal convoluted tubule cells and plasma renin activity exhibit measurable sequential differences between as well as within active and hibernating states at various time points. Limitations in the size of the experimental population prevented an evaluation of changes in these parameters during other important periods such as periodic arousal between hibernation bouts. In this study, glomerular endothelial pore number and epithelial filtration slit number significantly decreased by early hibernation when compared to those during summer activity, and then they increased back toward summer levels by late hibernation. In contrast, podocytic pedicel width along the glomerular basement membrane increased from summer activity to early hibernation, before significantly decreasing again by late hibernation. Mesangial cell and proximal convoluted tubule cell activity appeared increased during hibernation as compared to summer activity, whereas the width of the glomerular basement membrane showed no significant alterations throughout. Plasma renin activity significantly increased during early hibernation and mid-hibernation when compared to summer levels but had decreased by late hibernation toward summer values. The glomerular and plasma renin activity changes observed in this study clearly illustrate the drastic structural and functional adjustments which hibernating species make during torpor and also correlate well with the reported decrease in renal perfusion pressure and urine formation during hibernation. The observed morphological changes during hibernation do not appear to be temperature-dependent, because significant alterations in most of the parameters studied occurred during this period despite the fact that cold-room temperatures were kept constant throughout. The chronological approach to this study and its morphometric evaluation represent a pilot attempt at accurately documenting these changes during two critical states in the hibernator's cycle and may eventually lead to the characterization of these changes during the entire circannual cycle.     

Level of dehydrogenase activity in chipmunks under normal conditions and during chronic external gamma-irradiation

Chipmunks were chronically exposed to gamma-radiation at an average dose rate of 46 pA/kg. Changes in activity of succinate dehydrogenase (EC 1.3.99.1), pyruvate dehydrogenase (EC 1.2, 4.1) and lactate dehydrogenase (EC 1.1.1.27) were detected in the homogenates of the cardiac muscle, liver and brain at different physiological periods (before, during and after hibernation). The changes observed were related to the impairment of coordination between the processes of tissue respiration and glycolysis.     

Seasonal morphological peculiarities of the structure of the adrenal cortex in ground squirrels (Citellus erythrogenys)]

The morphological state of the adrenal cortex was studied in Citellus erythogenus in different periods of their year cycle: May, July, January. The morphological criteria of Selye - Stone (1950) and the ratio between dark and light cells were used for estimation of the morphological state of the adrenal cortex. It was shown that a number of morphological parameters under study had distinct seasonal dynamics. The thickness of the glomerular zone and of all the adrenal cortex was maximal in the period of hibernation. It became thinner in the period of waking up and it was minimal in July. Light cells prevailed in the period of waking up, in July the amount of dark and light cells was approximately equal and in winter dark cells prevailed. The comparison of the character of morphological changes of the glomerular and bundle zones shows that the distinctions are pronounced only during deep winter hibernation.     

Increased oxidative stress and decreased activities of Ca(2+)/Mg(2+)-ATPase and Na(+)/K(+)-ATPase in the red blood cells of the hibernating black bear

During hibernation, animals undergo metabolic changes that result in reduced utilization of glucose and oxygen. Fat is known to be the preferential source of energy for hibernating animals. Malonyldialdehyde (MDA) is an end product of fatty acid oxidation, and is generally used as an index of lipid peroxidation. We report here that peroxidation of lipids is increased in the plasma and in the membranes of red blood cells in black bears during hibernation. The plasma MDA content was about four fold higher during hibernation as compared to that during the active, non-hibernating state (P < 0.0001). Similarly, MDA content of erythrocyte membranes was significantly increased during hibernation (P < 0.025). The activity of Ca(2+)/Mg(2+)-ATPase in the erythrocyte membrane was significantly decreased in the hibernating state as compared to the active state. Na(+)/K(+)-ATPase activity was also decreased, though not significant, during hibernation. These results suggest that during hibernation, the bears are under increased oxidative stress, and have reduced activities of membrane-bound enzymes such as Ca(2+)/Mg(2+)-ATPase and Na(+)/K(+)-ATPase. These changes can be considered part of the adaptive for survival process of metabolic depression.