Ultrastructural studies on the medulla of rabbit pineal gland in the diurnal rhythm.

Presence of numerous capillary vessels was detected, featuring thin unfenestrated endothelium with low number of plasmalemmal and pinocytic vesicles. Visual appraisal demonstrated no differences in number of cellular transport exponents between stages at which maximum and minimum melatonin levels were noted in the serum. Pineal parenchyma consisted of two types of pinealocytes: clear and dark ones. In hour of the peak gland activity the number of dark pinealocytes was doubled. No evident differences were observed between the two time points in the number of clear pinealocytes and of glial cells.

Junctional systems in the pineal gland of the Wistar rat (Ratus ratus). A freeze-fracture and thin section study.

Intercellular junctions between neighbouring pinealocytes, glial cells, glial cells and pinealocytes as well as between nerve endings and parenchymal cells of the pineal gland of Wistar rats were investigated on freeze-fracture replicas and thin sections by transmission electron microscopy. Gap junctions, tight junctions and the annular gap junctions have been revealed. In addition, chemical synapses between nerve endings and pinealocytes have been observed.

Ultrastructural studies on the blood-testes barrier of the rat.

Typical pinocytic vesicles were visible in electron micrographs in both outer and inner cellular layers of rat boundary tissue. FF technique revealed that they formed characteristic ribbons of foveoli. Foveoles less numerous were present in outer lamina for the most part of the investigated material. So we believe that this phenomenon speaks in favor of myoblastic origin of that layer.

Stereological studies on the ultrastructural markers of renal tubular transport during accelerations acting along the +Gz axis.

The study was carried out on rats. Electron micrographs of the kidney obtained under +Gz accelerations were analysed. Using stereological methods the estimation of ultrastructural markers of active transport (mitochondria energy state), and passive transport (intercellular spaces and basal infolded channels) was performed in the proximal and distal tubules. The results obtained indicated that during the actions of accelerations active tubular transport was impaired as reflected by a lowering of mitochondrial energy states (similar to condensed) in the proximal and distal tubules. Widening of intercellular spaces and basal infolded channels was also observed, which suggests fluid stasis and thus impairment of passive transport.

Trial comparison of mitochondrial cristae craters images obtained by the freeze-fracturing and ultrathin sections method.

In two-folded lamina of the mitochondrial cristae occurs in mitochondria of spermatocytes large areas of the inner and outer halves in freeze-fracturing technique morphological observations suggest that in mitochondrial membrane there exist "crater-like' structures with internal diameter of approximately 18 nm. A question has come up why no mention has so far been found in the literature of the appearance of similar structure in mitochondrial cristae in specimens in transmission electron microscope (TEM) observed. Thus comparison of our findings obtained by the freeze-fracturing (FF) method with those achieved by TEM was made.

Ultrastructural markers of renal tubular transport in rats under physiological conditions.

Mitochondria of the proximal and distal tubules which are in different configurational states of epithelial cells and their surface--volume relationship of intercellular spaces and basal infolded channels were evaluated in rats. The evaluation was performed with stereological methods. The studies were carried out on 5 rats under physiological conditions using electron microscopy. Mitochondria within the proximal and distal tubules were found to occur in transitional states close to the orthodox state. However, mitochondria within the proximal tubules were in a higher energy state, closer to the orthodox state when compared with those within the distal tubules. Surface--volume parameters of intercellular spaces and basal infolded channels were unexpectedly higher than the relation to active ion transport as well as indiscernible permeability of the distal tubular basement membrane.

Ultrastructural markers of tubular transport within the rat nephron in experimental diabetes insipidus.

Using stereological methods mitochondrial energy states and intercellular spaces with basal infolded channels were evaluated in proximal and distal tubules in rats. The studies were performed on animals with experimental diabetes insipidus and on control rats by means of electron microscopy. No significant differences were found in mitochondrial energy states and sizes of intercellular spaces with basal infolded channels in the proximal tubules, which indicates undisturbed transport in this nephron segment. However, significant differences of these parameters were found in the distal tubules. In diabetes insipidus mitochondrial energy states approximated the condensed state, while in the control animals they were similar to the orthodox state. Intercellular spaces became significantly narrowed in diabetes insipidus in comparison with these in the controls. These observations suggest that mitochondrial energy states may be considered as ultrastructural markers of active tubular transport, while intercellular spaces with basal infolded channels may reflect ultrastructural counterparts of water transport.

Stereological studies on germ cell mitochondria of rat during spermatogenesis and spermiogenesis.

The following stereological parameters of mitochondria were calculated in rat germ cells during the spermatogenesis: volume density of matrix, outer compartment, outer membrane and inner membrane, surface density of outer membrane and inner membrane. They were the basis to calculate the partition coefficient of matrix and partition coefficient of outer compartment. The matrix volume demonstrated a decreasing in mitochondria of germ cells during spermatogenesis. The relative volume of outer compartment was calculated with the intracristal spaces and revealed increasing from spermatogonia to spermatids. The partition coefficient for the matrix significantly decreased. Our observations suggest that transformation of mitochondrial configuration during spermatogenesis and spermiogenesis is the expression of intensive metabolic processes and activity of membrane transport in germ cells.

Ultrastructural examinations of the zone function of the rat pineal gland in terms of mitochondrial bioenergetics.

Membrane-membrane relations in the pineal gland were analysed. It was found that neighbouring pinealocytes may be in different mitochondrial configurational states. The pinealocytes lying next to the same glial cell and around nerve endings are in one metabolic state. Close to blood vessels this uniformity occurred when the perivascular space was surrounded by one glial cell.

Ultrastructural studies on the boundary tissue of the seminiferous tubules of different mammals.

The aims of our studies were to compare the ultrastructure of the boundary tissue of seminiferous tubules of various mammals (rat, mouse, hamster, guinea pig, rabbit, ram, bull and man). Visual analysis of electron micrographs revealed the similarity of structure of all layers at investigated animals. The boundary tissue consists of 4 layers: 1) amorphous inner lamina, 2) cellular inner lamina, 3) amorphous outer lamina, 4) cellular outer lamina. The outer lamina of boundary tissue of rat, mouse and hamster revealed in histochemical reactions meshes resembling honey-combs. The wall of seminiferous canalicules of bull and ram consists of more bigger and different structure than one at the other laboratory animals. The most different structure of boundary tissue in man was observed. The capillary vessels penetrate in the myofibroblastic layer, when comparted to that found in other mammals on the surface of the wall.

Studies on the structure of the boundary tissue of the white rat seminiferous tubules.

The studies on boundary tissue of the white rat seminiferous tubules with light and electron microscopy were carried out. The wall of the tubules consists of four layers: two cellular and two amorphous ones. In cellular external sheath the characteristic intercellular fissures a network of hexagonal meshes were seen resembling the honey-combs.

Stereological studies of mitochondria during the implantation of mouse blastocytes.

The following stereological parameters of mitochondria were compared in trophoblast of 5 and 6 day blastocysts: volume density of inner membrane (Vim), outer membrane (Vom), matrix (Vmat), outer compartment (Voc), surface density of outer membrane (Som) and inner membrane (Sim). They were the basis to calculate the partition coefficient of matrix (Emm) and the partition coefficient of outer compartment (Eocm). On 6 day after fertilization we found statistically significant volume increase of Vim, Voc, Sim, Som, Eocm and volume decrease of Vom, Vmat and Emm. Mitochondria visual evaluation and stereological analysis made for both groups allow to classify them to metabolic transitional state.

Freeze-fracture studies on mitochondrial membranes of spermatocytes.

Separation of the two-folded lamina of the mitochondrial cristae occurs in mitochondria of spermatocytes and spermatids. Freeze-fracture exposes large areas of the inner and outer halves of the inner membrane. The surface of the outer half of the inner membrane is concave, with small numbers of intramembranous particles (IMPs). Its distinctive feature is the presence of protruding particles surrounding a pit. On the inner half of the inner membrane, there are large numbers of densely-packed, irregularly-distributed IMPs, among which regular pits are seen. Morphometric analysis and reconstructions suggest that these structures are "channels" in the mitochondrial membrane with an internal diameter of approximately 18 nm. It is uncertain whether such mitochondrial structures are confined to the spermatocyte or whether they may also occur in other cells.

Ultrastructural studies on the mitochondria of the pinealocyte under conditions of persistent lighting--L24.

Rat pinealocytes were found to contain mitochondria in three configurational states and they were calculated at 11.00 a.m. and 11.00 p.m. Their proportions were found to change in 24 hours. Analysis of these results indicated the existence of correlation between pinealocyte bioenergetics and melatonin biosynthesis and its lack in relation to serotonin. Cell groupings with mitochondria in the same configurational state were observed, which suggest the existence of functionally differentiated zones within the pineal gland.

Morphometry of mitochondrial changes in mouse trophoblast cells at early implantation.

The blastocysts of a mouse in an experimentally delayed implantation are known to have a low consumption of oxygen, but when implantation is initiated their oxygen consumption increases within 4 h. Our stereological analyses of the mitochondria have demonstrated that these changes are associated with an increase in volume density of the mitochondrial matrix and a decrease of surface density of the inner membranes. Thus, at this early stage of blastocyst implantation, the mitochondria of the activated blastocysts change to an orthodox state.

Stereologic studies on mitochondrial configuration in the rat pinealocytes.

Stereologic studies were performed on rat pinealocytes. In the morphometric analysis the following parameters were taken into consideration: the volume density of the outer and inner membranes, surface areas of the outer and inner membranes, inner membrane to outer membrane surface area ratio, volumes of the outer and inner compartments, and partition coefficients of these compartments. Visual analysis demonstrated three mitochondrial configurational states. Based on the mitochondrial criteria, the existence of three pinealocyte types may be demonstrated. The authors believe that these are the cells in three different functional states.

Ultrastructural studies on the pinealocyte mitochondria during the daytime and at night.

Rat pinealocytes were found to contain mitochondria in three configurational states and they were calculated during their maximum (11:00) and minimum (23:00) serotonin content under various conditions of lighting (LD 12:12 and D 24). Their proportions were found to change in the circadian rhythm. Analysis of these results indicated the existence of correlation between pinealocyte bioenergetics and melatonin biosynthesis and its lack in relation to serotonin. Cell groupings with mitochondria in the same configurational state were observed, which suggests the existence of functionally differentiated zones within the pineal gland. In this context, the biochemically demonstrated circadian rhythm in the pineal gland secretion results from the synchronization at the organ level arising from the resultant function of individual pinealocytes.

Ultrastructural studies on diurnal variations in mitochondria in various regions of the hepatic lobule.

Stereologic studies on diurnal variations in ultrastructural manifestations of hepatic mitochondrial function in various regions of the hepatic lobules were performed. The experiments were performed on Wistar rats in May when the liver shows the maximal content of glycogen. The materials for the studies were taken at 8 am. and 10 p.m. The stereologic examinations were done according to the method of Weibel et al. The results obtained may suggest a conversion of the orthodox hepatic mitochondria to the transitional state, that is during the glycogen minimum in the rats in May. In the morning, when the glycogen deposits increased, the pericentral mitochondria are in the orthodox state. In the evening glycogen consumption due to glycogenolysis was accompanied by conversion of the mitochondria from the orthodox state to the transitional ones, which may suggest their increased metabolic activity.

Ultrastructural markers of tubular transport in experimental diabetes insipidus.

Stereological analysis of changes in tubular transport markers in diabetes insipidus has been undertaken. Intracellular spaces and basal infolded channels were considered as the markers of water transport, while mitochondrial metabolic steady states were considered as the active transport markers. Transmission electron microscopic observations revealed morphometric differences in the surface area and volume of intercellular space and basal infolded channels in the distal tubules. Stereological markers of mitochondrial metabolic states demonstrated significant differences in the distal tubules between diabetes insipidus and control groups. In diabetes insipidus the volume and surface area of intercellular spaces and basal infolded channels in the distal tubules were decreased and the mitochondrial energy state was lowered.