Morphofunctional and histochemical characteristics of the hindlimb muscles of the Rana temporaria in ontogeny

Mixed muscles of adult frogs respond to the increase in external potassium and to Ach by polyphasic contracture which is due to asynchronous activity of various groups of muscle fibers (fast phasic, intermediate and tonic ones). In the developing in vivo hindlimb muscles, the predominance of phasic contractile response and relatively weak tonic one were noted. In contrast to definitive muscles, in which maximum potassium and acetylcholine contractures are identical, growing muscles produce weak contractile reaction to Ach. Ach sensitivity of the developing muscles (as revealed by the contracture) is lower than in the definitive ones. Histochemical (studies on the lipid content and the activity of succinate dehydrogenase) and morphometric (the ratio of muscle fibers of different types at different stages of development, comparison of their diameters, relative size of tonic bundle, etc.) studies indicate that the development of morphological substrate for tonic contractions (tonic and intermediate muscle fibers) takes place at a lower rate as compared to the development of the substrate for phasic contractions. However, histochemically tonic fibers may be revealed already at the stage of myotubes.     

Morphofunctional characteristics of spinal cord neurons in the early stages of cultivation

A study of the ultrastructural peculiarities of the spinal cord neural cells in 14 day old chick embryos at the early stages of cultivation has shown that adaptation processes are completed within the first days of explant cultivation. Further cultivation leads to the differentiation of neurons and to the recovery of their capacity of bioelectrical activity.     

Prolactin-secreting neurons in the dorsolateral hypothalamus in Sprague-Dawley rats

By means of immunocytochemical techniques ovine prolactin like immunoreactivity (oPRL-LIR) has been demonstrated in the perikarya located around fornix in the dorso-lateral part of the rat hypothalamus. No PRL-LIR was observed in the arcuate n. perikarya. Immunoreactive fibers were present in the hypothalamus, medial thalamus, accumbens and amygdaloid nuclei.     

Morphofunctional characteristics of the recovery processes in the resected thyroid of rats

Histological, electron microscopy and radiometry methods were used to study the time-course of the recovery of the morphological and functional parameters of the rat thyroid after resecting 2/3 of the organ. The signs of thyrocyte regeneration, namely hypertrophy of the cells and ultrastructures, proliferation and formation of new follicles were most pronounced on the 5th day. The increase in the number of C cells, their hypertrophy and proliferation permit attaining the high calcitonin level in the blood serum, reaching a maximum on the 15th experimental day.     

Morphofunctional characteristics of adrenal reactivity in rats of different ages

Ultrastructural peculiarities of the cortical and medullary substance of the adrenals have been studied in mature (8-month-old) and old (26-month-old) intact white male rats and in rats of the same age groups in 3 h after electrical stimulation of the hypothalamic ventromedial nuclei. By means of certain biochemical methods contents of hormones (corticosterone, adrenaline and noradrenaline) have been estimated, as well as that of cholesterin and ascorbic acid in blood and adrenal tissues. After the hypothalamus is stimulated in the mature rats, certain peculiarities in the adrenals reactivity are revealed; they demonstrate positive ultrastructural and functional correlation of secretory cells in the cortex and medulla and are characterized with hypertrophy of the nuclei, increased amount of polyribosomes, hypertrophied Golgi complex and canaliculi of the endoplasmic reticulum and increased contents of corticosteroids and catecholamines in blood. In the old rats after stimulation of the hypothalamus, certain unequal ultrastructural and functional peculiarities are revealed. They demonstrate both disturbance of the hypothalamic regulation of the adrenal function at ageing and decreased adaptive possibilities of the adrenal secretory cells at the subcellular level.     

Morphofunctional characteristics of the endosteum

Basing on the literature data analysis, modern notions concerning endosteum structure, its connections with the bone and bone marrow are presented. Participation of the endosteum in processes of osteogenesis and resorption, as well as its changes with ageing are discussed.     

Ultrastructural characteristics of vasopressin-containing neurons in the paraventricular nucleus of the hypothalamus

Summary Vasopressin-containing neurons, identified by immunocytochemistry, are located predominantly in the posterior magnocellular division of the paraventricular nucleus of the rat hypothalamus. By electron microscopy, the immunoreaction product is seen within the cell bodies and neuronal processes. In the perikarya and dendritic processes, the immunoreactive material is associated primarily with neurosecretory granules. Axonal processes, identified by their content of microtubules and accumulation of neurosecretory granules, show the immunoreaction product in association with both of these organelles. Afferent axo-dendritic, axo-somatic and putative axo-axonic synapses with immunostained vasopressinergic neurons can be identified. The presynaptic profiles do not contain immunoreactive material. This study contributes to the ultrastructural characterization of vasopressinergic neurons in the paraventricular nucleus and of their afferent synaptic input.Supported by NIH Grants HD-12956 and 2SO7RR05403     

Glucose-sensing neurons of the hypothalamus

Specialized subgroups of hypothalamic neurons exhibit specific excitatory or inhibitory electrical responses to changes in extracellular levels of glucose. Glucose-excited neurons were traditionally assumed to employ a 'beta-cell' glucose-sensing strategy, where glucose elevates cytosolic ATP, which closes KATP channels containing Kir6.2 subunits, causing depolarization and increased excitability. Recent findings indicate that although elements of this canonical model are functional in some hypothalamic cells, this pathway is not universally essential for excitation of glucose-sensing neurons by glucose. Thus glucose-induced excitation of arcuate nucleus neurons was recently reported in mice lacking Kir6.2, and no significant increases in cytosolic ATP levels could be detected in hypothalamic neurons after changes in extracellular glucose. Possible alternative glucose-sensing strategies include electrogenic glucose entry, glucose-induced release of glial lactate, and extracellular glucose receptors. Glucose-induced electrical inhibition is much less understood than excitation, and has been proposed to involve reduction in the depolarizing activity of the Na+/K+ pump, or activation of a hyperpolarizing Cl- current. Investigations of neurotransmitter identities of glucose-sensing neurons are beginning to provide detailed information about their physiological roles. In the mouse lateral hypothalamus, orexin/hypocretin neurons (which promote wakefulness, locomotor activity and foraging) are glucose-inhibited, whereas melanin-concentrating hormone neurons (which promote sleep and energy conservation) are glucose-excited. In the hypothalamic arcuate nucleus, excitatory actions of glucose on anorexigenic POMC neurons in mice have been reported, while the appetite-promoting NPY neurons may be directly inhibited by glucose. These results stress the fundamental importance of hypothalamic glucose-sensing neurons in orchestrating sleep-wake cycles, energy expenditure and feeding behaviour.     

胃动素受体激动剂红霉素对大鼠下丘脑葡萄糖反应神经元的作用

目的:通过观察胃动素受体激动剂红霉素对大鼠下丘脑中葡萄糖反应神经元电活动的影响,探讨中枢胃动素对摄食活动调控的机制.方法:应用细胞外记录神经元单位放电的方法,记录麻醉大鼠LHA及VMH的神经元电活动.左颈总动脉注射0.56 mol/L葡萄糖溶液0.2 ml鉴别GSNs及GRNs;侧脑室注射红霉素4 μg,观察其对葡萄糖反应神经元及非葡萄糖反应神经元自发放电频率的影响;侧脑室注射GM-109(胃动素受体拮抗剂)与红霉素的混合剂(1:50的比例配制),观察上述效应是否可重复出现.结果:在LHA,红霉素对GSNs有明显的兴奋作用,与其对该核团NGSNs的作用相比较,差别有统计学意义(P＜0.05);在VMH,红霉素对GRNs有明显的抑制作用,与其对该核团NGRNs的作用相比较,差别有统计学意义(P＜0.01).对红霉素有反应的神经元在给予GM-109和红霉素的混合剂后,神经元的放电频率无明显变化.结论:胃动素受体激动剂红霉素可兴奋LHA-GSNs同时抑制VMH-GRNs,这一途径可能是中枢胃动素促进摄食活动的神经调节机制之一.     

SOCS-3 expression in leptin-sensitive neurons of the hypothalamus of fed and fasted rats

Treatment of rodents with exogenous leptin increases SOCS-3 mRNA levels in the arcuate nucleus (ARC) and dorsomedial nucleus (DMN) of the hypothalamus. To determine if SOCS-3 gene activity in the hypothalamus could be influenced by changes in physiological levels of circulating leptin, we performed in situ hybridization (ISH) and immunostaining for SOCS-3 expression in fed vs. fasted (48 h) rats. The ARC and DMN were the only regions of the diencephalon that showed SOCS-3 ISH and the autoradiographic ISH signal for SOCS-3 mRNA was visibly less in the ARC and DMN of fasted rats. The ISH signal for SOCS-3 mRNA was decreased 70% in the ARC and 90% in the DMN (to background levels) when animals were fasted (P<0.01), consistent with decreased immunostaining for SOCS-3 protein observed in the fasted rats. Double fluorescence ISH (FISH) analyses showed colocalization of SOCS-3 mRNA with mRNAs for NPY and POMC in the ARC. These findings are consistent with increased leptin signaling to the NPY and POMC neurons in the ARC by physiological levels of circulating leptin during normal feeding. Therefore, changes in SOCS-3 mRNA levels in the ARC and DMN can be viewed as an indicator of relative physiological leptin signaling to the hypothalamus and also identify cells responding directly to leptin signaling through its cognate receptor.     

Histamine-immunoreactive neurons in the hypothalamus of cats

The localization of histaminergic neurons in the cat brain was determined immunohistochemically with an antibody against histamine. We found that histamine-immunoreactive neurons are observed exclusively in the posterior hypothalamus of colchicine treated cats. The larger group of neurons was found in the ventrolateral part of the posterior hypothalamus, including the tuberomammillary nucleus. Histamine-positive neurons were also observed in the supramammillary area and adjacent posterior hypothalamic area, as well as in the peri- and premammillary regions. In addition, numerous histamine immunoreactive fibers were detected, not only in the posterior hypothalamus, but also in other brain areas, such as the preoptic area of the anterior hypothalamus.     

Ultrastructural features of somatostatin-containing neurons of the hypothalamus of rats with protein insufficiency

The electron microscopic investigation was performed to analyze somatostatin-contained nerve terminals in the median eminence of 21 days old malnourished rats' hypothalamus. In nerve terminals of malnourished animals in compared with controls ones there was found the increased density of granular vesicles (11.62 +/- 0.40 and 8.56 +/- 0.39 in 1 micron2, respectively) and decreased density of electron lucent vesicles with 120-160 nm diameter (1.66 +/- 0.18 and 3.43 +/- 0.26 in 1 micro2, respectively). The revealed increase in density of granular vesicles in axon terminals with positive immunohistochemical reaction to somatostatin in malnourished rats was explained by slow somatostatin release.     

Vibrissectomy in rats in early ontogeny leads to disordered functional properties of the cortical projection neurons

Vibrissae trimming during the first 20 days of postnatal life caused alternations of the properties of the receptive fields of single neurons in the barrel-field cortex in rats. The following changes were found in the deafferented cortex: (i) an extension of the receptive fields of single neurons as judged from an increase in the number of vibrissae with short-latency excitatory responses to stimulation and (ii) a depression of the inhibitory receptive field tuning mechanisms.     

Participation of neuronal NO-synthase in regulation of hypothalamus vasopressinergic neurons of rat pups at early stages of postnatal ontogeny

To reveal character of interaction of catecholamines (CA) and NO in regulation of development and of the functional state of vasopressinergic (VP-ergic) neurons of supraoptic (SON) and paraventricular (PVN) nuclei, the female rats were injected intraperitoneally with the inhibitor of CA synthesis α-methyl-p-tyrosine, daily, from the 13th to the 20th days of pregnancy. Rat pups born by the females administered with saline at the same period of pregnancy as well as intact pups and adult rats were used as control. Expression of neuronal NO-synthase (nNOS) in neurons of SON and PVN of rat pups at early stages of postnatal development was found to be significantly higher than the definitive level, which allows suggesting participation of NO in development of hypothalamic VP-ergic neurons. The revealed differences of periods of the maximal nNOS expression in the SON and PVN neurons have permitted suggesting development of SON to be completed earlier than that of PVN. The pups exposed to stress at the last third of embryonic development had a long-lasting effect on the state of VP-ergic neurons of the pups after birth. The nNOS expression in neurons does not change, which suggests that NO is not involved in regulation of VP-ergic neurons after exposure to stress at early stages of ontogenesis. A decrease of CA level in the brain at the last third of embryogenesis led to a long preserved decrease of the functional activity of VP-ergic neurons. The nNOS expression in VP-ergic neurons of SON and PVN rose substantially under effect of a compensatory enhancement of tyrosine hydroxylase (TH) expression in neurons of SON and of an increase of the level of CA-ergic innervation of PVN. Thus, we have shown that a decrease of CA level in the embryonic brain leads to an increase of nNOS expression of hypothalamic VP-ergic neurons of rat pups after birth and that the character of NO action on function of VP-ergic neurons does not differ from that of adult animals as soon as at early stages of ontogenesis.     

Morphofunctional characteristics of the thyroid gland in intact and partially sympathectomized rats of different age groups

The morphological and functional age-dependent changes have been studied in the thyroid gland of infantile (1-month-old), immature (2- and 3-month-old) and sexually mature (6-month-old) male rats. The decrease in thyroid functional activity with ageing was proved. Chemical sympathectomy (guanethidine at a dose of 15 mg/kg intramuscularly for 14 days after birth) was accompanied not only by morphological reconstruction of the thyroid tissue, but also (especially in 1-month-old rats) by a delay in transport-organic phase of iodine metabolism and a decline in thyroid hormone serum level. Later on, the compensatory hormonogenesis reinforcement occurs as a result of partial adrenergic innervation recovery.     

Morphofunctional characteristics of neurosecretory cells of the supraoptic nucleus of rats with parathyroprival hypocalcemia]

Humori-positive neurosecretory cells of the supraoptic nucleus of the hypothalamus have been investigated during various time of parathyroprival hypocalcemia after extirpation of the parathyroid glands. Contents of total and ionized calcium, phosphorus in blood serum have been estimated. Volume of nuclei and nucleoli has been measured. In 5 days functional activity of the supraoptic nucleus increases (lightly stained cells predominate, volume of the nuclei and nucleoli increases). In subsequent 15-30 days its activity decreases (increase in amount of dark-stained cells, nucleolar volume decreases). In 60 days there is a tendency to restoration of neurosecretion.     

Morphofunctional state of the stomach in rats with hyposalivation

Hypoptyalism and deficiency of physiologically active saliva substances induced by it cause some essential changes in the morphofunctional state of the stomach mucosa, ultrastructure of the gastrin-producing cells and gastrin quantity in blood that testifies to the disturbance of the neurohumoral stomach regulation.