Development of the neural apparatus of the human pancreas in prenatal ontogeny

In human embryos, prefetuses and fetuses from 6 to 40 weeks of development 82 preparations of the pancreas have been studied; 39 series of slices of the human embryos have been impregnated after Bielschowsky-Boeke. For the first time the nerves grow into the pancreas anlage in embryos of 16 mm long (6 weeks). The main sources supplying the pancreas with the nerves in the period studied are nervus vagus, celiac, hepatic, splenic, right adrenal, superior mesenteric and intermesenteric plexuses. Three stages in formation of the innervational apparatus of the pancreas are distinguished during the intrauterine development. The first stage is characterized by beginning of the nerve growing into the pancreas anlage. For the second stage an increased development of the intraorganic innervational apparatus and appearance of the all main sources of the organ's innervation are specific. The third stage is characterized with an increased differentiation of receptor zones in various parts of the pancreas. The development of the pancreatic innervational apparatus by the time of birth is not completed.     

Sex differences in the development of the thyroid gland in human prenatal ontogeny

A comparative study of the thyroid gland development in the human male and female embryos and prefoetuses was carried out. The development of incretory part of the testicles was shown to occur earlier than the differentiation of follicles in the thyroid gland and the appearance of colloid in it. Sexual differences were noted in the appearance of follicles, connective tissue, nerve fibres in the thyroid gland (earlier in the male foetuses). The processes of organ differentiation in the male foetuses were more active than in the female ones during the whole prenatal period of development. A suggestion is put forward that the sexual hormones of embryonic testicles influence the thyroid gland differentiation.     

Development of the ductule system of the epididymis in the prenatal period of human ontogeny

In 285 human embryos, prefetuses, fetuses and newborns by means of a complex of morphological methods, development of the epididymal canalicular system has been studied. The anlage of the epididymal canalicular system is stated to appear in embryos 13.0-17.0 mm long (the 6th week of development) and is presented as an accumulation of epithelial cells and primary germ cells between reducing glomeruli and mesonephric canaliculi. The canalization process of the cellular accumulations and their transformation into real canaliculi takes place during the first half of the prefetal period (the 8th week of development). Further growth and development of the epididymal canaliculi takes place in the craniocaudal direction and by the end of the prefetal period (the 12th week) the canaliculi of the head are already formed, they have a twisted course; within the limits of the body and tail they are yet poorly differentiated and their course is nearly straight. During the fetal period of ontogenesis, further differentiation of the epididymal parts occurs and structure of their canaliculi becomes more complex. They acquire a twisted course in all the parts of the organ; by the end of the fetal period the form and structure of the epididymal canaliculi resemble those of the definitive organ.     

The development of the thoracic duct lymphangions in the prenatal period of human ontogeny]

This paper concerns structural and functional organization of the human lymphatic system during the prenatal period. For the first time the data is presented on the development of thoracic duct based on the concept of lymphangion as a structural and functional unit of a lymphatic vessel. The formation of the duct is considered in connection with structural changes of its wall and variants of duct roots fusion. The following stages are distinguished in the development of the thoracic duct: valval segment stage, protolymphangion, and lymphangion.     

Development of dendritic spines in the piriform neurons of the cerebellar cortex in human prenatal ontogeny

The submicroscopic investigation on developmental peculiarities of the dendritic spines in the piriform neurons of the cerebellar cortex has been performed during the human prenatal ontogenesis. The process of morphogenesis of the spines of the tertiary dendrites in the piriform neurons is demonstrated to start rather early--on the 24th week of embryogenesis and goes through three successive stages: 1) formation of a long cytoplasmic processes deprived of any membranous specialization; 2) formation of the terminal spinal head, making synapses with parallel fibers of the cerebellar cortex; 3) definitive stage. A suggestion is made that differentiation processes of the spines depend on inductive influence of the parallel fibers of the cerebellar cortex.     

Development of the hemomicrocirculatory bed of the human gonads during the prenatal period of ontogeny

The formation of the organospecific hemomicrocirculatory bed of the ovaries and testes has been studied by a complex of light, transmissive and scanning electron microscopy in 3--9-month-old human fetuses. The change of the diffusive protocapillary bed is secured by: 1) reduction of some protocapillaries; 2) appearance of secondary capillaries from the growth buds of the preceeding microvessels; 3) formation of arteriolar and venular links of the hemomicrocirculatory bed from the protocapillaries at the expense of differentiation of the developing paravasal connective tissue into cellular elements of the muscular and adventitial tunics. The secondary blood capillaries of the human gonads are predominantly formed intraendothelially. During the prenatal ontogenesis presence of the secondary blood capillaries of somatic uninterrupted type is specific for the human gonads.     

Somatic genomic variations in early human prenatal development

Only 25 to 30% of conceptions result in a live birth. There is mounting evidence that the cause for this low fecundity is an extremely high incidence of chromosomal rearrangements occurring in the cleavage stage embryo. In this review, we gather all recent evidence for an extraordinary degree of mosaicisms in early embryogenesis. The presence of the rearrangements seen in the cleavage stage embryos can explain the origins of the placental mosaicisms seen during chorion villi sampling as well as the chromosomal anomalies seen in early miscarriages. Whereas these rearrangements often lead to implantation failure and early miscarriages, natural selection of the fittest cells in the embryo is the likely mechanism leading to healthy fetuses.     

Changes in the form and ultrastructure of the smooth-muscle cells in the human aorta in prenatal ontogeny]

The shape of smooth muscle cells (SMC) was analysed using the phase contrast microscopy of cell suspensions obtained by alcohol-alkali dissociation, as well as the semithin sections prepared in perpendicular planes. The phenotype of SMC was analysed using transmission electron microscopy. The shape of SMC changes from preferentially round to preferentially spindle-like and stellate one during development. The differentiation of SMC is accompanied with the increase in the contractile apparatus content and in the decrease in the content of synthetic organelles.     

Pathology of amniogenesis in the early prenatal period of human development

Morphological and, in a number of cases, cytogenetical investigation has been performed in 420 intact embryonal sacs and in embryos 7-8-week-old, obtained at spontaneous abortions (272) and at tubal pregnancy (148). Among these cases 202 (48.1%) intact empty embryonal sacs, 75 (17.9%) embryos with panorganodysplasia, 25 (6%) embryos with isolated developmental defects and 118 (28%) phenotypically normal embryos have been revealed. Pathology of amniogenesis such as aplasia or hypoplasia of the amniotic cavity is noted in 136 (32.4%) cases. Among 75 embryos with panorganodysplasia anomalies such as hypoplasia of the amniotic cavity in combination with a partial extra-amniotic++ position of the embryos in exocelom (10.7%), aplasia (5.3%) or hypoplasia (17.3%) amniotic peduncle is present in 43 (57.3%) observations. Out of 40 such cases at spontaneous abortions, cytogenetically investigated, in 27 (67.5%) chromosomal disorders (tetraploidy, triploidy, autosomal trisomy and monosomy) are revealed. Aplasia and hypoplasia of the amniotic cavity are considered as pathology of histogenesis at the tissue stage of the early human ontogenesis, that most evidently occurs as a result of asplasia, destruction or anomaly of embryoblast during the first phase of gastrulation on the 7th-11th day of the intrauterine development.     

Localization of glutamate in the human retina during early prenatal development

In this study we have localized glutamate (GLU) in fetal (14–25 weeks gestation, Wg) human retinas by immunohistochemistry. At 14 Wg, GLU-immunoreactivity (IR) was localized only in the central part of retina, showing a prominently labelled nerve fiber layero A few ganglion cells and displaced amacrine cells were very weakly labelled. At 17 Wg, GLU was localized conspicuously in many ganglion cells, displaced amacrine cells, some amacrine cells and the prospective photoreceptor cell bodies in the neuroepithelial layero With progressive development at 20 and 25 Wg, the IR for GLU was found additionally in the Müller cell endfeet, some bipolar cells as well as in the horizontal cells that were aligned in a row along the outer border of the inner nuclear layer of the central retinao The photoreceptor cell bodies in the outer nuclear layer were also prominently immunopositive for GLU. The developmental distribution of GLU in the human retina tends to indicate that it plays an important role in the differentiation and maturation of retinal neurons.     

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.     

The lipid peroxidation system in the retina and brain of rats during early postnatal ontogeny

The content of the lipid peroxidation products in the rat retina and brain tissues during the early postnatal period (20-45 day of life) was estimated. It was shown during this period the content of conjugated dienes was decreased: the content of malondialdehyde and Schiff bases was without changes in the rat retina. At the same time the content of the conjugated dienes and Schiff bases in the brain tissue was proportionally increased. The activity of glutathioneperoxidase and glutathionereductase was decreased in the retina and not changed in brain. In the same period of the life the content of alpha-tocopherol in the retina was increased. We observed also the enhance of the rate of the induced lipid peroxidation in brain and retina of older animals.     

Maturation of the human hypothalamo-hypophyseal neurosecretory system in prenatal ontogeny. A light-optical and electron microscopic study

The hypothalamic-hypophysial neurosecretory system (HHNS) was studied in the human foetuses from the age of 8 weeks till birth. The hypothalamus of 8 weeks old foetuses is weakly differentiated, no individual cell groups, so-called nuclei, are identified. The supraoptic (SON) and paraventricular (PVN) nuclei are identified from the age of 12 weeks on. The size of cell nuclei increases with the age. The Homori-positive granules were first found in some SON and PVN cell and in neurohypophysis in the 18 weeks old foetuses. It was shown under the electron microscope that the neurohypophysis of 8 weeks old foetuses consisted mainly of pituicytes with axons among the cytoplasmic processes of the latter. After the age of 10 weeks, the area of parenchyma of the neurohypophysis occupied by axons increased and typical elementary neurosecretory granules appeared in them. The data obtained are discussed with respect to the participation of HHNS in the regulation of water metabolism in the human foetuses.     

Formation of primary microvessels in the early stages of prenatal human morphogenesis

By means of light and electron microscopy, the most general mechanisms of formation and development of primary blood microvessels in functionally different organs (adenohypophysis, thyroid, thymus, liver, spleen, small and large intestine) have been studied in human embryos 4-8 weeks of age. Ultrastructure of cells in the extra- and intraorganic mesenchyme is described; to the latter belongs the leading role in organization the pathways of the prevascular microcirculation. The primary microvessels are formed as a result of canalization of the intercellular clefts, lining with mesenchymal cells, that gradually transfer into primordial endotheliocytes. Basing on ultrastructural analysis, certain stages of differentiation of protocapillary endotheliocytes have been defined and described in different organs. The change of the prevascular microcirculation into the intraorganic protocapillary bed (the primary blood bed) is an essential and necessary stage of the organogenesis.     

Adrenal glucocorticoid function and its regulation in human prenatal ontogeny and in the 1st week of life

A comparison of cortisol and ACTH level determination in 82 human fetal sera obtained in the 11th-34th week of the intrauterine development and 50 sera from infants 1-7 days of age has revealed several stages of pituitary-adrenal system (PAS) maturation. PAS is immature in the first trimester of embryogenesis when cortisol concentration in the human fetal blood is low. The functional relations between pituitary and adrenal glands begin to establish in the middle of prenatal developmental period. A prominent response to delivery stress indicates that by delivery PAS reaches a certain stage of maturation. The feedback between ACTH and cortisol secretions in the blood of infants 1-7 days of age demonstrates that the refractory period of PAS is absent in the neonates during the first week of their life.     

Effect of neonatal androgenization on the septal neurons of the brain in female rats in early postnatal ontogeny

Newborn female rats were androgenized, and the reaction of neurons of brain septum on excessive quantity of exogenous androgens, introduced during so-called "crucial" period of formation of centers of gonadotropic regulation of sexual cycles, has been studied in 3, 5, 7, 10, 20, 30, and 60 days old animals. Morphometry of brain septum cell nuclei revealed that most neuron nuclei shrink after androgenization. Monoamine content was significantly increased in septum nuclei of experimental animals. Neonatal androgenization led to the increased capacity of septal complex neurons to bind 3H-estradiol and to the decreased 3H-testosterone binding. The data obtained suggest that the brain septum neurons of female rats depend on sex steroids, particularly during "crucial" period of development.