Ultrastructure of the synapses of the initial axonal segment of the pyramidal neuron

Ultrastructure of the proximal part of the axon in the neurons, identified according to a number of morphological signs as pyramidal, has been studied in the layer III of the cat cerebral hemisphere sensomotor cortex. In sections, tangential to the cortical surface, in the initial axonal segment, a submembranous osmophilic layer and fasciculi of microtubules are revealed. On the initial segment spines are found, they contain cysterns resembling by their structure the spine system of the dendritic spines. Axonal terminals revealed along the axonal distribution are in contact both with the axonal trunk and with the spines. Regarding the initial segment, they are presynaptic, contain oval synaptic vesicles and form symmetric axo-axonal synapses only. In transversal sections axonal terminals are detected, arranging on the surface of the initial segment mostly as single ones, in longitudinal sections they are seen as clusters. Analysing the author's data and those from the literature, a conclusion is made that in intact animals the synaptic contacts at the initial segment of the axon are the only form of axo-axonal synapses in the neocortex.     

Individual variability in the structure of the walls of the principal trunks of the subcutaneous veins of the lower extremities of the human fetus

Certain regional peculiarities are noted in the development process of the human principle trunks of the subcutaneous veins during antenatal period. In the fetuses of all ages the wall thickness of the subcutaneous veins is the greatest in the femur, and the middle tunic is better developed in the shin. The vein structure depends on the type of architectonics: at the magistral type (86%) the walls in the large and minor subcutaneous veins are thick with well developed smooth myocytes and connective tissue fibers; at the reticulate type (14%) the walls are thin, their elements are poorly developed. When there is mentioned varicosity of the lower extremity veins in the parents' anamnesis, in fetuses (57%) all the tunics in the venous wall develop more poorly, there is retardation in formation of smooth myocytes and in maturation of collagen fibers. This results in less amount of contractile structures in the middle tunic and optic density of collagen is less manifected.     

Variants of the position of the jugular trunks

Topographo-anatomical position of the jugular trunks has been investigated in 30 human corpses. Certain differences in structure of the left and right jugular trunks are revealed, their peculiarities in persons with different habitus type are noted. The peculiarities mentioned are expedient to take into account in surgical practice, when pathways of lymphatic drenage are cut with prophylactic aims in patients suffering from inflammatory processes in the maxillofacial area.     

Ultrastructure of synapses in the nucleus of the trapezoid body of the bat]

The subsynaptic structure of the synapses in the medial nucleus of the trapezoid body was studied in the bat Myotis oxygnatus. The synaptic endings in the nucleus are represented by large-cup-shaped and small loop-shaped terminations. The cup-shaped terminations are formed of large branches originating from a thick myelinated fibre after loss of myelin from it. Each branch forms a series of contacts alternating with vast enlargements of extracellular space, on the body of the cell and its processes. Large branches are filled with synaptic vesicles, neurofilaments and neurotubules, mitochondria; all these components are distributed rather regularly along the branch diameter. In fine branches of the cup the synaptic vesicles are the main and often the only component. The pattern of the cup branch changes as the distance from the main fibre increases, namely the amount of neurofilaments and neurotubules diminishes up to their disappearance, while the amount and the density of synaptic vesicles increases. The small loop-shaped treminals are different from the cup-shaped ones by the composition of the synaptic vesicles and the structure of the contact zone. In addition to agranular vesicles there are also granular ones. Both types of terminations--cup-shaped and loop-shaped ones -- are found both on the bodies and dendrites. On distal portions of dendrites the terminations are disposed in nests.     

Histochemistry of the placenta of the pig

Summary The distribution of glycogen, RNA, lipid, acid mucopolysaccharides, diastase-resistant PAS-positive material, hydrolytic enzymes, specific and non-specific alkaline phosphatases, and carbohydrate dehydrogenases is described in the foetal and maternal placenta of the pig throughout gestation. The results are compared with the findings in similar and other placental types, and some deductions regarding the functional significance of the enzymes in the structures in which they are observed are made.     

Ultrastructure of the stria vascularis of the auricular labyrinth of the rabbit]

In the composition of the stria vascularis of the rabbit cochlea there are three types of cells: edging, medial and basal cells. The structure of these cells, their disposition and interrelationships within the stria vascularis are described. The nodes of the basal membrane whose ramification covers long mitichondria concentrating at the basement of edging cells are found in the structure of capillaries of the cochlea stria vascularis. It may be supposed that this powerful mitochondrial apparatus refers to the capillary system of the stria vascularis and represents a hypertrophic mitochondrial apparatus of pericytes. The capillaries of the stria vascularis are distributed mainly in longitudinal direction while the capillaries disposed transversely which are likely to be anastomoses were also found.     

Ultrastructure of the kidney of the newt

In the newt [Triturus vulgaris (J.)] kidney a zone of single nephrons is distinguished, where there are ten nephrons, connected with the paramesonephral (Müller's) canal, and another zone of the renal mass; in the latter the main part of nephrons is situated, which are connected with the ureter by means of collecting tubules. In these zones of the kidney ultrastructure of epitheliocytes in the proximal and distal parts is different. The renal corpuscles of the epithelial cell in the cervical and in the intermediate parts are similar in both zones. In the zone of the single nephrons a specific peculiarity of epitheliocytes in the proximal and in the distal parts of the canaliculi is presence of numerous secretory granules in their cytoplasm. The canalicular epitheliocytes in the renal mass zone are different in the terminal and in the initial parts of the canaliculi: the former contains more mitochondria, and the area of the basolateral parts of plasmolemma is greater than those in the latter. These results are in accordance with the level of sodium ions transport in these parts of the canaliculus.     

The variances of the distributions of the combinations of the sexes within mammalian litters: Notes to mark the centenary of the problem

It is 100 years since Gini noted that in some samples of litters of mice and rabbits, the variances of the distributions of the combinations of the sexes are sub-binomial. In other words, in contrast with binomial expectation, there are too many litters in which the sexes are equally balanced, and there are too few unisexual litters. In the intervening years, this finding has been replicated in a number of further species, but no explanation has become established. Potential explanations are reviewed here, and it is suggested that the most likely cause is that, at the time of formation of the zygotes, p, the probability that a zygote will be male, varies from one zygote to another within litters, thus constituting an example of Poisson variation. And it is a standard result in probability theory that such variation causes sub-binomial variance.     

Demonstration of the heterogeneity of the mast cell population on the basis of the mucopolysaccharide content.

From the aspect of its mucopolysaccharide content the mast cell population is not homogeneous. The pulmonary and heart muscle mast cells of the rat are alcian blue positive, the mast cells of the thyroid gland, lymph nodes, subcutaneous connective tissue, mesentery and peripheral nerve are safranin positive, whereas among the mast cells of the peritoneal cavity and the thymus there are both alcian blue and saffranin positive forms. The least acid mucopolysaccharides are in the mast cells of the peritoneal fluid, the mesentery and the lungs, whereas the most acid ones are in the mast cells of the lymph nodes, the subcutaneous connective tissue and the thyroid gland. There is a considerable difference between the two last mentioned organs. The mast cells of the subcutaneous connective tissue are end-product cells without amine or precursor turnover, whereas the mast cells of the thyroid gland incorporate and deliver amines, which may participate in the regulation of the host gland.     

The ultrastructure of the sinuatrial ring bundle and of the caudal extension of the sinus node in the right atrium of the rabbit heart

Summary The cells of the sinuatrial ring bundle are smaller than the ordinary myocardial cells; they have a regular outline and a large content of myofibrils exhibiting distinct H-bands and M-lines. Rudimentary T-tubules are found. The cells are connected by frequent nexus junctions, desmosomes and regions of interfibrillar contact, both on the well developed intercalated discs and at the periphery of the cells.The cells in the cauda of the sinus node, which extends alongside the crista terminalis together with the right branch of the sinuatrial ring bundle, are irregularly outlined and have a highly variable diameter (1–10 m). They occur in clusters of closely packed cells. The content of myofibrils is sparse and the fibrils exhibit no M-lines and only weak H-bands. No T-tubules are found. The cells are not connected by intercalated discs and no nexus junctions are found.Both tissues contain unmyelinated nerves and nerve fibres. Varicosities with mitochondria and vesicles are found in close apposition to the muscle cells.     

Characteristics of the structure of the cornea of the reptilian eye]

Submicroscopic structural peculiarities in the cornea are described in some reptiles (grass-snake, lizard, turtle). Certain stages in histogenesis of the grass-snake cornea are presented. Poor differentiation of epithelium and its resemblance to endothelium is demonstrated in the grass-snake cornea. In cytoplasm of cornea cells of lizard and turtle a high content of mitochondria is noted. Great majority of mitochondria compactly arranged in the middle part of cytoplasm provide the appearance of zones. There is a middle zone of mitochondrial arrangement, there are also two zones in cytoplasm (internal-perinuclear and peripheral) without mitochondria but with supporting structures.     

On the nature of the horny scales of the pangolin

The pangolin scale is a horny derivative of the epidermis. It is complex in structure and is divisible into three distinct regions. The dorsal plate forms approximately one-sixth of the scale thickness. It is composed of flattened solid keratinized cells without basophilic nuclear remnants. This region tends to fray easily. The dorsal plate contains bound phospholipids and sulphydryl groups but is weak in disulphide bonds.
The bulk of the scale is made up of the intermediate plate formed of less flattened cells without basophilic nuclei. This region is rich in disulphide bonds but contains no appreciable bound phospholipids or sulphydryl groups.
The ventral plate is only a few cells thick and is rich in bound phospholipids, which also occur in the underlying scale bed epidermis.
These three regions of the scale are formed from separate epidermal germinal areas which do not develop a granular layer. Keratohyalin granules are, however, formed in the epidermis between the scales.
It is suggested on the basis of histological structure and dishribution of chemical constituents that pangolin scales are probably homologous with primate nails.
Evidence against the views that they are homologous with reptilian scales or are derived from compressed hairs is presented.     

Topography of the contours of the inner surface of the wall of the left ventricle of the heart in systole

Chosen at random 38 diastolic preparations of human hearts from persons having not any cardiac pathology, as demonstrate the postmortem examination, have been investigated. The left ventricle casts have been made during the first 24 hours after death according to a strictly fixed technique by means of filling the cardiac chambers with polymere mass--protacryl--under a physiological pressure of the diastolic filling. The trabecules are arranged as a spiral from the apex of the ventricle up to the atrioventricular fibrous ring, with approaching the apex the spiral step increases and the trabecules straighten. The left ventricle cast is devided into some planes, the envelopes and the trabecularity lines are measured. Average values of the shift in the trabecularity lines I, II, III and in the cross sections B, C, D, E are defined in relation to the plane A and in every case in relation to the previous plane Cn-1. The data obtained are presented in tables and diagrams. The greatest shift demonstrate the trabecularity lines I running predominantly along the posterior wall of the left ventricle in the planes B and which are situated nearer to the atrioventricular ring projection. Owing to the presence of the spiral-shaped course of the trabecules, it is possible to suppose that it influences the blood stream twisting clockwise in the left ventricle during the diastole phase. This indicates the necessity to work out some new constructions of artificial cardiac valves, securing the twisted blood stream. The condition mentioned should be taken into consideration while making prostheses of the cardiac valves.     

Light microscopy of the medial wall of the cerebral cortex of the lizard Psammodromus algirus

The telencephalic medial wall of the lizard Psammodromus algirus was studied using Golgi and conventional light microscopic techniques. The area is formed by two different cytological fields—medial cortex and dorsomedial cortex. These two cortices possess three layers dorsoventrally: a superficial plexiform layer, a cellular layer, and a deep plexiform layer. The alveus, a deep fiber system, runs adjacent to the ependyma. Four classes of neurons are found in the cellular layer of the medial cortex on the basis of soma shape, dendritic pattern, and position in the layer: horizontal, double pyramidal, and candelabra cells. Solitary cells are present in the superficial and deep plexiform layers of the medial cortex. Those of the superficial plexiform layer are stellate cells. Horizontal and vertical cells are found in the deep plexiform layer. Double pyramidal cells are the most frequently impregnated in the cellular layer of the dorsomedial cortex. In addition, candelabra cells are present at the lateral end of the layer. Two cell types are found in the deep plexiform layer of the dorsomedial cortex: solitary pyramidal cells and, among the fibers of the alveus, horizontal cells. Ependymal tanycytes line the ventricular surface, and protoplasmic astrocytes are found in the plexiform layers of both medial and dorsomedial cortices.     

Innervation of the anococcygeus muscle of the rat

Summary The innervation of the anococcygeus muscle of the rat was investigated with regard to the histochemical features of nerve fibers within the muscle and to the location of the postganglionic autonomic neurons which are the source of these fibers. Acetylcholinesterase-positive fibers and catecholaminergic fibers are abundant in the anococcygeus as well as the related retractor penis muscle. Neuronal somata, either between muscle bundles of the anococcygeus or in the connective tissue sheath, are also acetylcholinesterase-positive. Nerve fibers and a minority of the ganglion cells in the anococcygeus and retractor penis muscles are immunoreactive for vasoactive intestinal polypeptide. Injection of the retrogradely transported dye Fluorogold into the anococcygeus muscle filled neurons in the abdominopelvic sympathetic chain, pelvic plexus and a small number of neurons in the inferior mesenteric ganglion. In the pelvic plexus, some neurons were located in the major pelvic ganglion but most were found along the main penile nerve and its branches to the anococcygeus muscle. Immunocytochemistry of these identified neurons indicates that about one half of them are positive for vasoactive intestinal polypeptice. These results raise the possibility that both acetylcholine and vasoactive intestinal polypeptide are important neurotransmitters in autonomic nerves to the anococcygeus muscle.     

Features of the angioarchitectonics of the papillary muscles and the chordae tendineae of the human heart

In persons of mature, elderly and old age vascularization of the papillary muscles and tendinous chordae in the right and left cardiac ventricles has been studied depending on peculiarities of their structure and sources of their blood supply using injection, macro-microscopical, roentgenoangiographic methods, and silver nitrate impregnation. Certain data concerning the distribution zones in the papillary muscles of the coronary artery branches at various types of the cardiac blood supply are presented. Angioarchitectonics of the papillary muscles are described along their whole extention--in the basal area, in the middle part and at the apex. Architectonic peculiarities of the blood vessels in the muscular-tendinous part of the papillary muscles and in some tendinous chordae are described.     

Ultrastructure of the respiratory epithelium in the lungs of the tortoise,Testudo graeca

The respiratory epithelium in the lungs of the tortoise (Testudo graeca) has been studied by electron microscopy. The epithelium consists of a mosaic of two different cell types (here called "pneumonocytes"). Type I pneumonocytes are roughly squamous and possess attenuated flanges of cytoplasm which extend over the septal capillaries. Localized cytoplasmic expansions are often present near the periphery of these flanges. Most of the organelles are concentrated in the perinuclear region; the most prominent of these are the mitochondria and osmiophilic inclusions. In contrast, type II pneumonocytes are cuboidal and are richly endowed with organelles including large Golgi complexes, extensive endoplasmic reticulum and numerous inclusion bodies. The morphological evidence suggests that type I pneumonocytes are involved in the secretion of osmiophilic material (presumed to be pulmonary surfactant) and in maintaining the integrity of the air-blood barrier. Type II pneumonocytes appear to be concerned solely with the production of surfactant.     

Spectral characteristics of the EEG of the visual and motor cortices in the rabbit during stimulation of the reticular formation of the brain

Study of amplitude-frequency characteristics of dominating spectral maxima in the delta, theta and alpha-ranges of the rabbit visual and motor neocortical areas has shown that an increase of the midbrain reticular formation stimulation frequency from 60 to 1000 imp/s leads to an increase in both area of dominating rhythms frequencies in the theta and alpha-ranges, and to a decrease of the alpha-rhythm amplitude. The theta-rhythm amplitude in the visual area declines while in the motor area a slight increase is observed and then a decrease. Characteristics of the dominating frequency component in the delta-range are determined by three types of oscillations with different types of dependence on frequency of reticular formation stimulation. The most significant differences between areas are manifest in the spectrum amplitude characteristics. Qualitatively similar changes are also seen in correlation of power of spectral ranges in both areas but quantitatively they are more expressed in the motor area.     

Ultrastructural organization of the surface of the cingulate cortex of the cerebrum in rats

In the cingulate cortex of rats the marginal glia is predominantly presented as fibrillar astrocytes, their bodies are situated immediately at the surface. Numerous axons, dendrites, synapses and myelinated fibers are often arranged near the very surface and are separated from it with only 1-2 thin processes of glial cells. Along the whole cortical surface one can see a limiting membrane--a layer of non-cellular substance, situating at the distance of 60-100 mcm from plasmalemmas of the marginal astrocytes. Using ruthenium red, it is possible to reveal the glycocalix layer on the surface of the limiting membrane, as well as cords of the electron opaque substance, that connect it with plasmolemma of the superficial astrocytes. Three types of the cingulate cortex surface are described in rats: superficial areas to which cells of the pia mater membrane adjoin; areas where cells of the pia mater membrane are situated at various distance from the cortical surface and areas of close adjoining of the right and left hemispheres of the cerebrum. Sometimes the cleft between the hemispheres is completely reduced, and narrow lamellar-like cells of the pia mater membrane are tightly inserted between the limiting membranes of both hemispheres or adjoin the blood vessel, situating between the hemispheres. At the surface numerous gap and desmosome-like junctions are observed. This is especially important at the border where the media are separated. At injection of neurotoxin 6-hydroxydopamine certain ultrastructural rearrangements are noted in cytoplasm of the marginal astrocytes, changes in the number and extension of intercellular junctions.(ABSTRACT TRUNCATED AT 250 WORDS)