Development of accessory structures of the mechano- and chemoreceptor apparatus of the tongue during rat ontogeny (scanning electron microscopy)]

The dynamics on the formation of different types of mechno- and chemosensitive papillae in the rat tongue has been studied during different periods of postnatal ontogenesis by means of scanning electron microsopy. Asynchronous maturation of these papillae has been demonstrated, they perform certain functions during the early postnatal ontogenesis and reach their functional maturity by the age of 3 weeks when animals go over from suckling to solid food.     

Postnatal development of the cerebellar Purkinje cell shape in guinea pig ontogenesis

In sagittal cerebellum sections, morphometrical study of cerebellum of mature-born animals - guinea pigs - was performed using Nissl's procedure. A change of shape and volume of Purkinje cells and their nuclei in the course of the guinea pig postnatal ontogenesis was studied. It has been shown that both the growth process itself and the rate of formation of the definite form of Purkinje cells and of their nuclei in the course of ontogenesis proceeds non-uniformly. The most intensive growth of vertical and horizontal diameters of Purkinje cells and of their nuclei is observed during the 1st and 4th weeks of postnatal life. Especially rapid is an increase of horizontal diameters of Purkinje cells and of their nuclei, which impairs the ovoid-bear-like shape to the cerebellar Purkinje cells of adult guinea pigs.     

Postnatal development of the shape of cerebellar Purkinje cells in guinea pig ontogenesis

In sagittal cerebellum sections, morphometrical study of cerebellum of mature-born animals—guinea pigs—was performed using Nissl’s procedure. A change of shape and volume of Purkinje cells and their nuclei in the course of the guinea pig postnatal ontogenesis was studied. It has been shown that both the growth process itself and the rate of formation of the definite form of Purkinje cells and of their nuclei in the course of ontogenesis proceeds non-uniformly. The most intensive growth of vertical and horizontal diameters of Purkinje cells and of their nuclei is observed during the 1st and 4th weeks of postnatal life. Especially rapid is an increase of horizontal diameters of Purkinje cells and of their nuclei, which impairs the ovoid-bear-like shape to the cerebellar Purkinje cells of adult guinea pigs.     

Ultrastructure of the hypophysiotropic region of the hypothalamus in early ontogenesis in rats]

The results of electron microscopic studies have shown that the 16--18 days old rat embryos already have in the hypophysiotropic area some structures necessary for the realization of neuroendocrine regulations. In the arcuate nuclei, the neurosecretory cells differentiate which are capable to synthesize specific neurosecretory granules of 800--1,000 A in diameter. In the median eminence, the primary portal capillaries develop with which tanicytes and a few axon terminals make contact. One can see in the tanicytes the signs of active transport and accumulation of electron dense polymorphic material. All these phenomena are strengthen during the subsequent development. Hence, several days are before birth the neurosecretory and glial elements of the embryos show the signs of functional activity which strengthen during ontogenesis and are expressed most distinctly in the adult animals.     

Morphofunctional characteristics of microcirculation in the skin of girls 5-17 years of age

In 261 girls year-to-year morphofunctional transformations of spatial composition of the skin microcirculatory bed have been studied at rest and after a dynamic local load. By means of biomicroscopy main regularities in development of the skin capillary network have been revealed in the nail torus in the postnatal ontogenesis. Formation of the microvessels reactivity during various age periods and maturation of mechanisms of the compensatory-adaptive reactions are connected with formation of the definitive composition of the microcirculatory bed, that in girls corresponds to 11-12 years. Qualitative transformations in the skin capillary network bring certain quantitative changes in the structural microcirculatory parameters--increasing diameter of microvessels and increasing density of functioning capillaries.     

The formation of the microcirculatory bed of the neuromuscular systems of the tongue in human prenatal ontogeny]

A complex of adequate neurohistological and injection methods with use of mathematical analysis of the data obtained has been performed to study prenatal and early postnatal periods of ontogenesis of the microcirculatory bed of the human tongue neuromuscular systems. Certain changes of the degree in organization and structural-functional integration have been revealed; they demonstrate periodicity of the morphological changes of the vasculo-neural complex of the extra- and intrafusal part of the muscular tissue. In the neuromuscular spindles the microvascular network of capillaries is formed, their volumetric part changes in the process of development in greater degree than the microvascular bed of the extrafusal muscular fibers. In formation of the microcirculatory vascular bed of the neuromuscular spindles not only capillaries, getting into them together with nervous fibers, but also microvessels of the surrounding muscle tissue participate. This determines a higher level of the vascularization degree of the intrafusal muscle fibers.     

Development of ACTH-containing cells in the hypothalamus and hypophysis in their normal state and in protein deficiency

In cryostate sections of the brain and hypophysis of newborn, 10- and 21-day-old rats, by means of the indirect method immunohistochemical reaction has been performed. As a primary serum rabbit antiserum against ACTH has been used. The ventromedial hypothalamus and adenohypophysis have been studied by means of light and electron microscopy. Relationship of ACTH-containing cells in the adenohypophysis in the process of the postnatal ontogenesis and protein insufficiency remains constant. Unlike the adenohypophysis, in the hypothalamus part of the ACTH-containing cells decreases with age. When the animals develop under conditions of protein insufficiency, changes in the part of the ACTH-positive cells, that are age-dependent, do not coincide with corresponding parameters in the control. In the adenohypophyseal cells the products of diaminobensidine reaction are distributed in cytoplasm of granules with a dense center 100-200 nm in the diameter. The ACTH-containing cells in the hypothalamus are presented as small neurons with an even distribution of the immunohistochemical reaction products in cytoplasm and in large granules 200-280 nm in the diameter. Since in the adenohypophysis and in the hypothalamus various dynamics on contents of ACTH-reactive cells in the postnatal ontogenesis and at protein insufficiency has been revealed, and various localization of the diaminobenzidine reaction products has been demonstrated, a conclusion is made on heterogenous nature of antigenic determinants against ACTH, situating in these structures.     

Formation of immune proteasomes and development of the immune system in mammalian ontogenesis

Current concepts of the structure of immune proteasomes and their role in immune response have been considered. The main attention has been paid to the formation of immune proteasomes in secondary lymphoid and nonlymphoid organs during ontogenesis of mammals. The causes of ineffective formation of immune system in early postnatal development have been discussed.     

Study of Development of Function of Kidneys and Their Regulation on the Background of Pathological Process

By the example of reabsorption of sodium ions in kidney, it is shown that this process, alongside with establishment of the system of osmotic concentration, plays the key role in evolution of renal function. There is shown a similarity of tendencies of changes of the total sodium ion reabsorption in children’s kidney in the process of development and in a series of representatives of various vertebrate classes. An opposite tendency is revealed during the kidney dysfunction produced by chronic renal failure. At all stages of postnatal ontogenesis in healthy children and in adults, kidney maintains the same parameters of the blood serum ion composition and osmolality. A new approach to study evolution of functions is proposed, which is based on a combination of two L.A. Orbeli’s methods—ontogenetic and clinical, by the example of study of renal function and its regulation during development of a pathological process on the background of formation of function in postnatal ontogenesis. When using such approach in children with nocturnal enuresis, significance of autacoids in regulation of urine formation is established. In the case of acute pneumonia in children, a possibility of extrapituitary production of vasopressin-like substances in lungs is shown. In norm, in postnatal ontogenesis of healthy children, in regulation of renal functions and of diuresis system, effects of efferent nerves and hormones (vasopressin) dominate, while significance of autacoids is minimal. But at a dysfunction produced by a pathological process, a change of ratio of activities of these regulatory systems is revealed. The obtained data indicate importance of the clinical and experimental methods proposed by L.A. Orbeli in analysis of evolution of renal functions and study of the nature of regulations. A combination of several methods of evolutionary physiology in one study allows revealing new mechanisms underlying regulation of function and promotes formation of concepts about regularities of evolution of functions.__________Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 3, 2005, pp. 277–284.Original Russian Text Copyright © 2005 by Kuznetsova, Natochin.     

'Neurosecretion' by synaptic terminals in the locust corpus cardiacum: is non-synaptic exocytosis part of the regulated or the constitutive pathway?

Nerve fibres form conventional synaptic junctions with gland cells in the corpus cardiacum of the locust, Schistocerca gregaria. They contain synaptic vesicles whose contents are normally electron-lucent, but which react positively to cytochemical tests for amines (eg, incubation in the false transmitter 5-OHDA). Secretory granules are also present in the terminals and such inclusions are known to contain neuropeptides. The granules undergo non-synaptic exocytosis and this process has been visualized by the application of tannic acid. Granule exocytosis gives clear signs of being part of a regulated secretory pathway: it is elevated in vivo by flight--a natural stimulus known to activate the gland (this effect is blocked by prior injection of trehalose); its incidence is closely correlated with a postsynaptic response, suggesting a role for the materials discharged in short-term signalling; and when induced in vitro by high K+, it is Ca(2+)-dependent. However, a low level of exocytosis was encountered under all the conditions employed, suggesting the existence of a constitutive component. It is postulated that the regulated and constitutive patterns of discharge of neuropeptides are related to the roles of these materials as neurotransmitters/modulators and neurotrophic substances, respectively.     

Formation of immune proteasomes and development of immune system in ontogenesis of mammals

Current concepts of the structure of immune proteasomes and their role in immune response have been considered. The main attention has been paid to the formation of immune proteasomes in secondary lymphoid and nonlymphoid organs during ontogenesis of mammals. The causes of ineffective formation of immune system in early postnatal development have been discussed.     

Demonstration of specific secretory granules for human chorionic gonadotropin in placenta

Existence of secretory granules and exocytosis during secretion of human chorionic gonadotropin (hCG) in human placenta has been a point of controversy. Using two methods, the highly sensitive avidin-biotin complex (ABC) method and the protein A-gold technique, for immunochemical identification of beta-hCG on electron microscopic sections, we have examined placentas at 8-10 weeks gestation and at term for the presence of secretory granules. First-trimester placentas demonstrated plentiful syncytiotrophoblast cytoplasmic granules, some undergoing exocytosis, when stained using specific beta-hCG antiserum in the ABC and protein A-gold methods. Term placentas did not show positive reaction product. The data demonstrate that the classic secretory granule-exocytosis pathway mediates placental hCG secretion. However, clear morphological differences exist between placenta granules and hormone secretory granules observed in pituitary, consistent with known functional differences between these organs. This methodology will be useful for further studies of the secretory pathways for placental peptides.     

Characteristics of autogenic motor stimulation in rat pups

Studies have been made on the organization of the spontaneous motor activity during first 2 weeks of postnatal life of rats Rattus norvegicus (var albin.) by means of prolonged EMG recording from the gastrocnemius muscle and by computer analysis. Complexes of prolonged activity with a period of about 1 min, intracomplex periodicity of short pulses with a frequency 1/sec and periodicity of separate short bursts arranged into series with intervals between them of approximately 8-12 sec were observed. It was found that the main rhythm of these forms of excitation remains relatively unchanged during postnatal ontogenesis. The number of periods filled by series of short bursts decreases in postnatal development of animals, whereas the number of periods of a complete rest lasting for 1 1/2 and more minutes increases. These findings were compared with the development of sleep--wakefulness cycle in early postnatal ontogenesis.     

Effect of sympathectomy on the heart pump function in rats during postnatal ontogenesis

The influence of guanetidine sympathectomy (30 mg/kg) on the heart pump function in rats during 3 weeks in postnatal ontogenesis has been investigated. Sympathectomy restrains age-dependent establishment of stroke volume, cardiac output and heart rate. The adaptation effects of regular physical training do not develop in the animals with sympathectomy, i.e. heart rate does not decrease and stroke volume does not increase. The initial stage of adaptation of the sympathectomized animals to physical training is accompanied by decrease in stroke volume and remarkable increase in heart rate which indicates the reduction of contractile activity in the myocardium.     

Core formation and the acquisition of fusion competence are linked during secretory granule maturation in Tetrahymena

The formation of dense core secretory granules is a multistage process beginning in the trans Golgi network and continuing during a period of granule maturation. Direct interactions between proteins in the membrane and those in the forming dense core may be important for sorting during this process, as well as for organizing membrane proteins in mature granules. We have isolated two mutants in dense core granule formation in the ciliate Tetrahymena thermophila, an organism in which this pathway is genetically accessible. The mutants lie in two distinct genes but have similar phenotypes, marked by accumulation of a set of granule cargo markers in intracellular vesicles resembling immature secretory granules. Sorting to these vesicles appears specific, since they do not contain detectable levels of an extraneous secretory marker. The mutants were initially identified on the basis of aberrant proprotein processing, but also showed defects in the docking of the immature granules. These defects, in core assembly and docking, were similarly conditional with respect to growth conditions, and therefore are likely to be tightly linked. In starved cells, the processing defect was less severe, and the immature granules could dock but still did not undergo stimulated exocytosis. We identified a lumenal protein that localizes to the docking-competent end of wildtype granules, but which is delocalized in the mutants. Our results suggest that dense cores have functionally distinct domains that may be important for organizing membrane proteins involved in docking and fusion.     

Long-term disorders in the rat behaviour induced with introduction of the tumour necrosis factor in early postnatal ontogenesis

Anti-inflammatory cytokin the tumour necrosis factor alpha (TNFalpha) is one of the main mediators of neuroimmune interactions. The TNFalpha production increase in the cells of neural and immune systems occurs in infectious diseases, injuries, ischemia, hypoxia. In this study, the TNFalpha revealed its role in formation of behaviour in early postnatal ontogenesis. The rats with the TNFalpha administered during their 3 weeks of life differed from the control those by a change in the orienting behaviour and enhanced anxiety. The role of the anti-inflammatory cytokins in the brain during different stages of ontogenesis is discussed.     

Rab27 effector granuphilin promotes the plasma membrane targeting of insulin granules via interaction with syntaxin 1a

Secretory vesicle exocytosis is a highly regulated process involving vesicle targeting, priming, and membrane fusion. Rabs and SNAREs play a central role in executing these processes. We have shown recently that Rab27a and its effector, granuphilin, are involved in the exocytosis of insulin-containing secretory granules through a direct interaction with the plasma membrane syntaxin 1a in pancreatic beta cells. Here, we demonstrate that fluorescence-labeled insulin granules are peripherally accumulated in cells overexpressing granuphilin. The peripheral location of granules is well overlapped with both localizations of granuphilin and syntaxin 1a. The plasma membrane targeting of secretory granules is promoted by wild-type granuphilin but not by granuphilin mutants that are defective in binding to either Rab27a or syntaxin 1a. Granuphilin directly binds to the H3 domain of syntaxin 1a containing its SNARE motif. Moreover, introduction of the H3 domain into beta cells induces a dissociation of the native granuphilin-syntaxin complex and a marked reduction of newly docked granules. These results indicate that granuphilin plays a role in tethering insulin granules to the plasma membrane by an interaction with both Rab27a and syntaxin 1a. The complex formation of these three proteins may contribute to the specificity of the targeting process during the exocytosis of insulin granules.     

Mechanism of secretory granule exocytosis: can granule enlargement precede pore formation?

Secretory granules have been observed to swell during the process of exocytosis. Swelling is an indication of osmotic stress. The probable role of osmotic pressure in facilitating membrane fusion makes it necessary to determine whether granule membrane 'swelling' can occur prior to its fusion with the plasma membrane (pore formation) in the process of exocytosis. By subjecting adjacent thin and semi-thin sections of an activated granule to ultrastructural examination for membrane enlargement, and to metachromatic staining for verification of pore formation it is concluded that the perigranular membrane can indeed enlarge prior to pore formation. However, the degree of membrane enlargement can far exceed the limit of 2-3% stretching allowed under normal osmotic stress for a membrane bilayer. Such an extensive membrane enlargement, which takes place in the mechanism of exocytosis, cannot be achieved without being accompanied by the insertion of additional membrane.     

Structure of the thymus gland of the rat in the prenatal and early postnatal periods of development after exposure to tetracycline during the period of fetogenesis

Structure of the thymus in Wistar rats has been studied during antenatal and early postnatal periods of ontogenesis by means of histological, morphometric and electron microscopic methods. Theraputic doses of tetracycline hydrochloride have been administered during fetogenesis (15-20 days of pregnancy). An accelerated formation of the thymic structures, cellular blasttransformation in the thymic cortex and movement of lymphocytes from the cortex into medulla and increased secretory activity of epithelioreticulocytes have been revealed. The data obtained are considered as a display of the organ's immune response to tetracycline administration.