The microcirculatory bed of the normal rat thyroid and during hypokinesia based on scanning electron microscopy data on corrosion preparations

In 12 mature white rats with body mass of 180-230 g, that are kept in tight pencil-cases for 10, 30 and 90 days (3 rats make the control), by means of scanning electron microscopy of corrosive preparations reorganizations of three-dimensional spatial organization of the thyroid microcirculatory bed are studied. In intact animals single-layered network of the perifollicular capillaries consists of widely anastomotic blood microvessels and makes 68 +/- 7% of the follicular surface. At hypokinesia (Hk) lasting for 10 days, the perifollicular capillaries are sharply dilated, the capillary network area makes 74 +/- 4%. A large amount of processes appear on the capillary walls. On the 30th day of Hk unequal distribution of capillaries on the follicular surface is noted, that is heterogeneity in organization of the perifollicular capillary networks is manifested. In 90 days of Hk reduction of the capillaries is recorded, rarefied pericapillary network prevails, twistedness of the capillaries is clearly manifested, their complex branching decreases. The capillary network area makes 54 +/- 3% of the follicular area. A large amount of pin-shaped protrusions of the capillary wall appear.     

Changes in cells of the adenohypophysis after its simultaneous implantation with various hypothalamic nuclei

In 55 mature male rabbits and in 65 hypophysis-ectomized inbred male rats (body mass 200-230 g) implantation of the adenohypophysis with supraoptic, paraventricular and arcuate hypothalamic nuclei into the anterior chamber of the eye has been performed. The adenohypophyseal cellular structure has been estimated by means of light and electron microscopy from 12 up to 26 days of implantation. At a direct influence to the implanted adenocytes of the hypophysis substances of the supraoptic and paraventricular nuclei ensure stimulation of their proliferative processes, accompanied with increase of DNA synthesis. Besides, secretory process enhances in some somato-, mammo- and thyreotropocytes. Discovery of such cells as thyreo-, mammo- and corticotropocytes in newly-formed epithelial proliferates is considered as a fact of their possible functional differentiation de novo. Implantation of the adenohypophysis with the arcuate hypothalamic nuclei reveals activation in folliculin stimulating hormone in gonadotropocytes. During the process of secondary differentiation this group of adenocytes makes the greatest part of the cells. Somato-, mammotropocytes inhibit cytodifferentiation.     

Effect of hypokinesia and the combined action of gravitational load and hypokinesia on the structure of the hepatic portal system]

General hypokinesia during 1--6 weeks resulted in dilatation of the interlobular veins. sinusoids and central veins. The sequence of alterations corresponded to terms of hypokinesia. After exposure to "gravitation stress--hypokinesia for 1--6 weeks" stagnation in the portal system of the liver was less than after exposure to hypokinesia alone, but unevenness of lumens in the interlobular veins and sinusoids was more pronounced. The foci of the vessel spasm were determined. The signs of stagnation in the system of the portal vein and unevenness of the width of all the links of the portal bed were most pronounced after combination "hypokinesia for 1--6 weeks-- gravitation stress".     

Structure of the thyroid gland in the rat during hypokinesia and after its elimination

The aim of the investigation is to objectively ascertain and study stages of the processes taking into account the zonal structure of the thyroid gland, that is along the whole distance from the center up to the surface of the lobe. Hypokinesia lasts from 1 to 56 days; rehabilitation begins after 28 days of hypokinesia and lasts 28 days. Morphometric analysis of 8 parameters demonstrating the state of the gland are used. In control animals the structural changes from the center towards the surface of the gland lobe occur gradually, the degree of the changes is different and diversily directed [increasing volumetric part (Vv) of the follicular epithelium, decreasing Vv of the colloid, stable Vv of the vascular component]. When both hypokinesia and rehabilitation develop, all signs change wavily. Natural borders of the waves are defined--5, 16, 28 and 51 days for hypokinesia and 13 and 23 days for readaptation. Different structural components of the gland respond variously to the factors mentioned. Changes of every sign in different zones are also not equal and they can be diversily directed. In the course of rehabilitation for 1 month, there is no return to the normal state.     

Structure of spinal cord capillaries in hypokinesia

Changes in spatial interrelations of the spinal cord capillaries and motoneurons and capillary ultrastructure were studied under hypokinesia. Spatial interrelations between the capillaries and neurons were not demonstrated to change under hypokinesia. They were estimated by the following parameters: area of neuronal profile field, number of capillaries, their length, distance from the nerve cell body, capillary bed area and index of capillary-neuronal interrelations. Quantitative investigation revealed capillary stenosis: their diameter was one and a half times less under hypokinesia. Morphologically, capillary stenosis was accompanied by the basal membrane thickening and endothelial cytoplasm vacuolization. There was a direct relation between endothelial villi and the places of the endothelial cells contacts, dilatation of the contact interstices and solidifying of their borders. Changes in the capillaries were followed by reactions in the pericapillary structures, such as: fibrillae were formed, mitochondrii accumulated in the perivascular glial projections, the membrane next to capillary astrocyte projections underwent desmosome-like condensation. Mitochondrial accumulations were also observed in the nerve cell projections and in their cytoplasm sites contacting with the blood vessels.     

Mechanisms of the decrease in human postural stability during prolonged head-down tilt

In 3 identical experiments with head-down bed rest lasting 60, 90, and 120 days and involving 18 volunteers, dynamics of the development of cardiovascular system (C.V.S) deconditioning was studied. A set of radioisotopic research techniques was used. Volumes of hemocirculation, body fluids, and metabolic activity of the bone marrow were investigated. Functions of the central and peripheral hemodynamics were studied. To determine the extent of C.V.S. deconditioning during the baseline period, on days 60, 90, and 120 of hypokinesia and during recovery, an orthostatic test was performed. The degree of gravitational blood shifting in regions (the head, thorax, the abdomen, the lower extremities) was recorded. Critical thresholds of blood shifting in the body were determined. It was established that the blood pooled in the splanchnic region participates in the decrease of central hypovolemia. Because of the insufficient number of observations, this research should be continued. During recovery, the sign of (CVS) deconditioning noted demonstrated a clear tendency to normalization.     

Cardiovascular Function in Humans Using Thigh Cuffs during Seven Days of Simulated Microgravity

Data are summarized on changes in the human cardiovascular system associated with the use of cuffs during seven days of antiorthostatic hypokinesia simulating weightlessness. Eight subjects participated in two series of experiments, of which one was carried out with and the other (the control) without cuffs wrapped snugly around the upper third of the thighs. The parameters of the systemic hemodynamics, the cardiac function, and the hemodynamics of the cervicocephalic region and the lower limbs recorded under control and experimental conditions were analyzed. Without cuffs, changes in the hemodynamics during antiorthostatic hypokinesia were caused by displacement of body fluids in the cranial direction. The subjects responded favorably to the use of cuffs during antiorthostatic hypokinesia: most of their hemodynamic parameters remained at the baseline level, and signs of venous stasis in the cervicocephalic region were alleviated. Although the leg veins were distended in subjects wearing thigh cuffs during antiorthostatic hypokinesia, no pathological changes in the veins were detected during or after the experiment. Cuff usage during antiorthostatic hypokinesia lasting for seven days did not produce a cumulative effect on the cardiovascular system. These results justify the use of thigh cuffs in the initial period of adaptation to simulated or real weightlessness.     

Blood urea content changes in man under hypokinesia

It has been demonstrated that hypokinesia (diminished muscular activity) leads to an increase in blood urea content in man. Against this background the objective of this investigation was to determine blood urea content under hypokinesia (HK) on 17 physically healthy men aged 19-23 yr. They were divided into three groups: the 1st group (5 men) was examined under HK, the 2nd group (4 men) was studied during the background period (BGP) as well as in the readaptation period (RTP), and the 3rd group (8 men) was placed under ordinary conditions and served as control. For the simulation of the hypokinetic effect the men were kept under a rigorous bed rest regime for 16 days. Blood urea, blood creatinine, urine urea, and urine creatinine were measured. The results were processed statistically. The most pronounced increased urea content was observed in the men with an initial low concentration (3.3-4.2 mmole/liter). Variations in the urea concentration were analogous and manifested a reduction during the initial days and an elevation thereafter. Creatinine excretion and clearance were reduced uniformly and significantly during the initial 10 days of HK. It was concluded that diminished muscular activity induced an increase in urea content and a decrease in creatinine clearance in man.     

Intermitochondrial Contacts in the Mitochondriome of Cardiomyocytes under Normal Conditions,in Response to Physiological Stress,and in Pathology

Intermitochondrial contacts are universal and indispensable structures participating in the formation of mitochondriome in cardiomyocytes of invertebrate and vertebrate animals; they participate in the maintenance of the energy pool required for rhythmic contractions of the heart. At the ultrastructural level, a direct relationship is demonstrated between the functional load on the heart and the number of intermitochondrial contacts in the cardiomyocytes of swifts and rats: there was a twofold increase in the number of these contacts associated in actively flying adult birds as compared with chicks; a similar effect was observed in response to pressure overload associated with aortal stenosis; hypokinesia and hypoxia led to a twofold or even threefold decrease in their number.     

Morphological characteristics of the structures delimiting the residual cavity of the hypophysis in rats after electrocoagulation of the median eminence of the hypothalamus]

By means of light and electron microscopy it has been shown that the remnant cavity of the hypophysis of intact and sham-operated rats on the side of the intermedial lobe is restricted with a continuous layer of epithelial cells with a well pronounced basal membrane. On the side of the frontal lobe the covering epithelium has peculiar "fenestra" through which adenocytes have free contacts with the remnant cavity. After electrocoagulation of the rostral area of the medial eminence, especially in remote postoperative terms, the remnant cavity enlarges up to gigantic size, contains a great amount of colloid, erythrocytes, fragments of cells of the anterior lobe of the hypophysis and secretory granules. The anterior epithelium is lacking on considerable areas and hence adenocytes are disposed in the cavity directly. All their organoids are preserved though a little changed, the cytomembrane is absent. On the apical surface of the posterior epithelium there appear large cytoplasmic protrusions which having separated enter the remnant cavity. The main provider of the "raw material" for colloid is likely to be the anterior lobe of hypophysis.     

Histologic changes in tissue components of the hyperplastic thyroid gland during its involution in the rat

Male Fischer rats were fed a low-iodine diet containing thiouracil for 21 days to produce hyperplastic thyroid glands, and then fed a high-iodine diet for various time intervals, from 5 hr to 180 days, in order to study the morphological changes that occur during involution. Thyroids were fixed by perfusion fixation and embedded in Epon. Sections were examined by light microscopy. Initially at 0 days of involution (at the time of the change to the high-iodine diet), follicular lumens were very narrow and capillary lumens were very wide. The capsule was thick and infiltrated with mononuclear leukocytes. No obvious changes occurred for 1 day after the change in diet, but shortly thereafter capillary lumens began to narrow. By 4 days, most capillary lumens were close to normal size; capillaries formed a more or less normal bed except that many were embedded in a relatively thick or wide interfollicular matrix. This matrix was largely gone by 21 days. Between 1 and 21 days, follicular lumens dilated progressively as colloid accumulated. The density of staining of the accumulated colloid varied from follicle to follicle, and this variation was also observed in older controls. Inflammatory cells gradually disappeared from the capsule and most were gone by 15 days. Starting at approximately 15 days and continuing to 180 days, one or more disintegrating cells were found in some lumen profiles. Colloid goiters were not observed in these rats even after several months of involution. Some lumens were rather large, however, and small fractions of the follicles, both small and large, were bounded by flat cells and resembled "cold" follicles morphologically.     

Development of hypophysis and differentiation of its secretory cells at the early postembryonic development of silver carp Hypophthalmichthys molitrix (cyprinidae)

Silver carp Hypophthalmichthys molitrix hatches from the envelope at phase 19 a day after fecundation (water temperature 26–28°C) with body length 5.2 mm. The formation of hypophysis begins 7–8 h after hatching of the embryo. The first chromophilic cells (acidophiles in adenohypophysis) appear at the age of 9 days; the first basophilic cells (thyrotropocytes) at the age of 17–20 days, when juveniles are at stage III. The gonadotropic function is formed in the ontogenesis of silver carp at the age of 40–45 days, i.e., almost a month after the appearance of elementary sexual cells in the gonads. The differentiation of gonadotropocytes in mesoadenohypophysis to two functionally active types of cells (central and peripheral) is also completed by this time.     

The hormonal indices of the reactivity of the central links in the hypothalamo-hypophyseal-adrenocortical system of rats during postnatal ontogeny]

Radioimmunological assay has been made of the amount of ACTH in the adenohypophysis and blood plasma in adult male rats as well as in 1, 3, 5, 7, and 20 days old rat puppies 30 minutes after a surgical stress, i. e. cutting the skin at the back of the body. Reliable increase of ACTH level was originally observed in 7-day puppies, whereas in younger animals surgical stress resulted in the decrease of ACTH in the blood. Changes in vasopressin content of the blood and hypophysis exhibit significant variations, but on the whole mainly the decrease was observed in younger animals together with the increase from the 5-7th day of postnatal development of rats. Accumulation of vasopressin was noted in the median eminence after surgical stress in younger animals. The data obtained suggest that the early period of development of the hypothalamo-hypophyseal-adrenocortical system is characterized rather by paradoxal reaction than by non-reactivity, which may be associated with poor neurohormonal transport in the outer zone of the median eminence.     

Intermitochondrial contacts in a system of cardiomyocyte mitochondriome in a normal state, under physiological stress, and in pathology

Intermitochondrial contacts are universal and indispensable structures participating in the formation of mitochondriome in cardiomyocytes of invertebrate and vertebrate animals; they participate in the maintenance of the energy pool required for rhythmic contractions of the heart. At the ultrastructural level, a direct relationship is demonstrated between the functional load on the heart and the number of intermitochondrial contacts in cardiomyocytes of swifts and rats: there was a twofold increase in the number of these contacts associated in actively flying adult birds as compared with chicks; a similar effect was observed in response to pressure overload associated with aortal stenosis; hypokinesia and hypoxia led to a twofold or even threefold decrease in their number.     

Vascularization of the testes of the white rat in the high altitude conditions of the Pamir and Antarctica

By means of histometric and morphometric methods vascularization of the white rat testes has been studied at adaptation to living conditions in the Alpian Pamir (at the altitude of 4,000 m) and in the Antarctic Continent (at the altitude of 3,488 m). The leading factor in development of the parenchymatous rearrangements of the testes are certain disturbances of the microcirculatory link in the intraorganic bed. Different degree in manifestation of the morphological signs of the circulatory disturbances are revealed: plethora, interstitial tissue edema, degenerative changes in the spermatogenic epithelium cells and hence decreasing activity of spermatogenesis. The disturbances noted are essentially various in different stages of adaptation to the altitude. In contrast to the Pamir series of the experiment, in the group of the animals adapting to the living conditions of "Vostok" station, dilatation of the capillary lumens and signs of moderate plethora accompanying them remain up to the end of the observations.     

Bone tissue changes in rats during prolonged restriction of motor activity

The objective of this investigation was to measure the effect of prolonged restriction of motor activity (hypokinesia) of rats on the mass, density, mineral composition, reconstruction parameters and elemental composition of their bone tissue. The studies were done during 90 days of hypokinesia (HK) on 90 male Wistar rats equally divided into two groups: (1) vivarium control rats (VCR) and (2) hypokinetic rats (HKR). For the simulation of the hypokinetic effect the HKR group was kept for 90 days in small individual cages made of wood that restricted the movements of rats in all directions without hindering food and water intakes. During the prehypokinetic period of 15 days and during the hypokinetic period of 90 days bone mass, bone density, bone calcium and phosphorus concentrations, bone reconstruction parameters and elemental composition of bones were determined. During the same periods food intake and body weight losses were also measured. In the HKR group signs of osteoporosis in the spongy structures of the tubular bones were observed; they also showed significant decrease in rat femur weight, and in cross section of the rat femur, and in mineral concentrations of the femoral head when compared with the VCR group. The HKR group also show a significant decrease in food intake and body weight when compared with the VCR group. The corresponding parameters did not change significantly in the VCR group when compared with the baseline control values. It was concluded that prolonged exposure to HK induced osteoporosis and structural changes in bones. This apparently occurred due to inhibition of bone tissue formation in the HKR group.     

Energy metabolism in muscle tissue during hypokinesia of various durations

The state of energy metabolism in skeletal muscles and myocardium of albino rats was studied under long hypokinesia. It is established that on the 30th-70th days of hypokinesia endogenic fatty acids, whose oxidation promotes the uncoupling of oxidative phosphorylation and inhibition of the creatine phosphokinase reaction, are the main substrate of energy metabolism. In blood there occurs hyperlipemia and a decrease in the glucose content. A further immobilization results in predominance of succinate-dependent respiration, in blood there occurs a certain decrease in lipemia, normalization of the glucose level and an increase in the urea content.     

Effect of prolonged hypokinesia on the growth and skeletal musculature in the rat

Hypokinesia lasting for 1-5.5 months does not produce any muscular atrophy, but results in ceasing their growth and the growth of the animal. In the muscles, besides the soleus muscle, not any essential structural changes occur. The changes in the soleus muscle are manifested as a focal sclerosis and formation of new muscle fibers. They are considered as a result of a disturbed hemodynamics in it, that occurs during the first days of hypokinesia. During the readaptation period the animals and their muscles begin to grow again. A suggestion is expressed that one of the pathogenic causes making the growth stop is the stress that decreases the somatotrophic function of the hypophysis.     

Blood flow in diethylstilbestrol-induced anterior pituitary gland hyperplasia

Anterior pituitary hyperplasia was developed in female Fisher 344 rats by subcutaneously implanted slow-release diethylstilbestrol (DES) capsules. Blood flow was measured in two separate areas of the adenohypophysis using hydrogen clearance method at 6, 9, 10, and 13 weeks after the implantation. Blood flow progressively decreased while the DES capsules were in place (normal values in ml/g/min, mean +/- SD: 0.93 +/- .12 laterally and 1.15 +/- .11 medially, decreasing to 0.25 +/- .07 and 0.24 +/- .07, respectively, by 13 weeks). Histology confirmed nodular hyperplasia, development of large vascular lakes, and hemorrhages within the adenohypophysis. Total adenohypophysial blood flow was calculated as a product of mean blood flow as measured per unit weight and the weight of the gland. This figure progressively increased from 12.7 +/- 2 to 22.2 +/- 8 microliter/min by 13 weeks. All these changes were significant at the P less than 0.001 level. These blood flow measurements suggest that the hyperplastic adenohypophysis outgrows its blood supply which is additionally compromised by "useless" pooling of blood in the vascular lakes. However, there is an overall increase in the amount of blood flowing through the hyperplastic gland which may be explained by newly formed supplying vessels.     

First postpartum estrus and pregnancy in the female collared peccary (Tayassu tajacu) from the amazon

The onset of sexual cycle postpartum was described in the collared peccary (Tayassu tajacu). Serum progesterone and 17beta-estradiol profiles, vaginal smears and external genitalia were analyzed in 20 animals housed with their piglets during the first postpartum month. The appearance of external genitalia showed no variation in any of the females: a shallow, reddish vulva, and vaginal mucus were constant features throughout the study. Based on hormonal profiles and vaginal smear cell patterns, 16 (80%) of the 20 peccaries showed signs of estrus and were considered cycling. The remaining four females (20%) did no show signs of estrus confirmed by low levels of progesterone (0.9+/-0.4 ng/mL) during the first postpartum month. In the cycling peccaries, a serum 17beta-estradiol peak (53.4+/-8.1 pg/mL) was observed on Day 7+/-1 postpartum, along with a linear increase in progesterone concentration from 3 (4.3+/-2.6 ng/mL) to 11 (30.8+/-4.9 ng/mL) days after this estradiol peak. Proportions of the different cells of the vaginal epithelium also changed in these females: superficial plus intermediate cells amounted to 76% of the cell total between Days 6 and 9 postpartum, corresponding to the estradiol peak. Nine (56%) of the 16 cycling females mated, indicated by the presence of sperm cells in their vaginal smears, and 6 (67%) became pregnant, reaching term. Non-pregnant cycling females (n=10) showed a steady decrease in serum progesterone concentration from 11 to 23 days after the estradiol peak, when basal levels were attained and a new estradiol peak registered, indicating the resumption of cyclicity in these females. The time interval between the two estradiol peaks was 23.5+/-2.1 days in these females. In pregnant females, progesterone concentrations continued to rise to levels of 60 ng/mL (n=6) 23 days after mating. These findings indicate that the lactating collared peccary female can become cycling and fertile during the early postpartum period, and that a predominance of superficial plus intermediate vaginal cells can be taken as the first sign of estrus.