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Biomedical subjects

H Themann

Publications and source records attributed to H Themann.

At least 37 records · Page 2Linked to original sources
PubMed1982

Changes in mouse hepatocytes caused by vincamin. A thin-sectioning and freeze-fracture study.

Mouse liver was examined following a single intraperitoneal application of 25 mg/kg body weight vincamine. The studies were made using the technique of thin-sectioning for electron microscopy as well as the freeze-fracture method. The thin-sectioning technique was useful for observing discrete changes such as an increase in the mitochondria and alterations in the bile canaliculi, e.g. a loss of microvilli and dilatation of the lumen. No other cytoplasmic changes could be observed. It was only with the aid of the freeze-fracture method that alterations in the cell contacts became visible. In contrast to the control animals the tight junctions in the liver tissue of mice treated with vincamin were disorganized and irregularly arranged. The gap junctions showed a very irregular contour as well. The question arises as to the extent to which the freeze-fracture method should be applied in the testing of pharmaceuticals, so as to exclude the possibility of damage to membranes.

Animals↗
PubMed1982

Subsurface cisterns and lamellar bodies in the granule cells of the guinea-pig fascia dentata.

Subsurface cisterns (SSC's) and less frequent lamellar bodies (LB's) were identified in the granule cells of the guinea-pig fascia dentata. Both structures, composed of flattened or collapsed agranular cisterns, are continuous with the regular rough endoplasmic reticulum and occasionally connected with each other forming LB-SSC complexes. The SSC's are apposed to glia, synaptic boutons, and nerve cell processes as well as to neighbouring granule cells appearing here singly and in confronting pairs. The quantitative analysis of the various cisternal appositions compared to the distribution of the tissue components on the granule cell soma shows that the overwhelming majority of SSC's are related to glial cells.

Animals↗
PubMed1982

Effect of silybin on hepatic cell membranes after damage by polycyclic aromatic hydrocarbons (PAH).

Young female NMRI mice were given a single intraperitoneal injection of a PAH mixture containing 3 micrometers benzo(a)pyrene in a suspension of 0.5 ml tricapryline. 3 and 4 days later a number of the mice received injections of 100 mg/kg body weight of Silybin in the tail vein. Thin sections of the animals' livers were studied under the electron microscope using the freeze fracture technique. Following intraperitoneal injection of the PAH suspension, and without treatment with Silybin, marked dilatation of the intercellular space and frequent occurrence of intracytoplasmic vacuoles was observed in addition to pronounced alterations in the hepatocytic nuclei and mitochondria. Following the administration of Silybin these alterations were no longer observed, though 50% of the cell membranes exhibited a marked band-like proliferation of the tight junctions. This observation may be interpreted as supporting the postulated membrane-stabilizing effects of Silybin.

Animals↗
PubMed1982

Electron microscopic studies of the morphology of the corneal stroma in the rabbit cornea using the freeze-fracture technique.

The morphology of the corneal stroma in the rabbit cornea was investigated under the electron microscope using the freeze-fracture technique. The collagen fibrils were closely packed into collagen bundles. In the freeze-fracture replicas the amorphous ground substance could not be demonstrated. At the stroma membranes were shown with crater-shaped depressions on the P-face and corresponding elevations on the E-face. Regarding the topographical relationships between the membranes and other parts of the fibroblasts, it was concluded in this investigation that the crater-shaped structures probably constitute pores in the plasma membrane of fibroblasts.

Animals↗
PubMed1982

Ultrastructural study of cholestasis induced by longterm treatment with estradiol valerate. I. Tight junctional analysis and tracer experiments.

Over a period of 20 weeks estradiol valerate (1.5 mg/kg body weight/week) was administered subcutaneously to male Wistar rats from which the livers were examined at four week intervals employing a freeze-fracture technique and colloidal lanthanum tracer studies. In connection with intrahepatic cholestasis, distinct alterations in the tight junctions were observed, consisting of disorganization, rarification and proliferation. Disruption of the tight junctions was not seen and colloidal lanthanum did not penetrate into the bile canalicular lumen. Holding the view that the term "leakiness" of tight junctions should be defined with reference to the tracer employed, we conclude that in the liver one tight junctional strand is sufficient to prevent the escape of larger bile constituents such as bile acids and that a back diffusion of bile acids over the tight junctional barrier does not play a role in the pathogenesis of the estrogen-induced cholestasis. Interruptions of tight junctions, as described by other authors, are interpreted as a secondary mechanical effect. On the other hand, we consider an increased permeability of the tight junctions to water and small solute molecules as probable; possibly this increased permeability is brought about by alterations in the microfilaments. A model for the pathogenesis of the estrogen-induced intrahepatic cholestasis is proposed.

Animals↗
PubMed1982

Ultrastructural study of cholestasis induced by longterm treatment with estradiol valerate. II. Gap junctional analysis.

Treatment of male Wistar rats with estradiol valerate induced alterations in hepatic gap junctions as visualized by the freeze-fracture technique. The alterations involved the spacing, and regularity of packing of the membrane particles of the P face (PF) and complementary pits on the E face (EF), as well as internalization and changes in the number, size and shape of the junctional domains. In approximately 20% of the PF's of the lateral membrane of treated animals the nonjunctional IMPs were aggregated, while the bile canalicular membrane was never involved, maintaining its random distribution of particles. It is proposed that the changes in junctional area and the more general arrangement of the junctional particles may indicate a decrease in coupling between hepatocytes. The invaginations of gap junctions may represent a means for removing gap junctional membrane from the surface or may be an expression of a higher turnover of gap junctions. We assume that the alterations observed here are due to the specific effects of estrogen. This study addresses in detail a number of possible sites of activity and modes of action for estrogen.

Animals↗
PubMed1982

Freeze-fracture elucidation of hepatocyte membrane alterations following beta-pyridylcarbinol application.

The effect of beta-pyridylcarbinol on mice was investigated in long-term studies (21 days, daily dose of 0.1 mg) making use of thin-sectioning and freeze-fracture techniques. Thin sectioning merely revealed only subtle pathological changes including dilatation of the intercellular space and foundation of hepatocytic vacuoles. Only upon investigation using freeze-fracture was it possible to demonstrate more profound alterations, primarily involving the cell contacts, i.e. the gap and tight junctions. The organized structure of the tight junctions appeared dissipated. The meshwork was disorganized in some cases and reduced in size. Large, proliferative tight junctional maculae were frequently observed on the plasmalemma. In some cases the gap junctions had lost their round to oval shape and had increased in size to form large plaques protruding at numerous points. Moreover, even the bile canaliculi, which presented no pathological alterations on ultrathin section, exhibited damage as seen in freeze-fracture preparations. The lumen was uneven in contour and processes were visible extending into the adjacent cytoplasm. The present investigation shows that hepatocytic damage primarily affecting the membranes was first made evident using freeze-fracture technique. The issue is addressed as to the extent to which freeze-fracture technique should be employed in routine investigations of pharmaceuticals.

Animals↗
PubMed1982

[The effect of (+)-cyanidanol-3 on toxic fatty infiltration of liver parenchyma (author's transl)].

Polychlorinated biphenyls, pentachlorophenol, d-galactosamine or alcohol are well known substances which produce toxic liver damage in animal experiments. Of special significance is the toxic fatty infiltration in the live parenchyma of these models. The effects following (+)-Cyanidanol-3 (Catergen)--application after liver damage was studied by qualitative and quantitative electron microscopy. (+)-Cyanidanol-3 reduces the volume density of intracytoplasmatic fat following intoxication significantly to normal values.

Animals↗
PubMed1982

Cytochalasin B affects the gap and tight junctions of mouse hepatocytes in vivo.

This study investigates the effect of cytochalasin B at a dosage of 0.2 mg per mouse per day for a period of 7 days in an in vivo experiment on mouse liver. Using thin-sectioning and freeze-fracture technique both quantitative and qualitative analysis was made of membranes and cell contacts (gap and tight junctions). Significant alterations of both membranes and junctions were observed. The intercellular space showed vacuolar dilatation in some cases and there were vacuoles observed within the cytoplasm. The microvillar bile canaliculi were dilated. However, no colloidal tracer was observed within the lumen following lanthanum perfusion. With the aid of the freeze-fracture method it was possible to demonstrate that the strands of the tight junctions were highly disorganized. In some cases reduction and in other cases proliferation of tight junctions was observed. Large, proliferative plaques of tight junctions were found both in contact with the tight junctions of the bile canaliculus and ending freely on the plasmalemma. The gap junctions appeared enlarged as well. Their average size increased from 0.42 micron 2 to 0.90 micron 2 (p less than 0.005). The enlargement was also accompanied by an increase in the proportion of the plasma membrane occupied by the junctions: 3.42% in control animals, 10.25% in the livers of mice treated with cytochalasin B. Frequently evaginated and internalized gap junctions were seen in the experimental group. In view of the fact that cytochalasin B, in addition to other effects, also has an effect on the microfilament system of the cell, it may be supposed that microfilaments play a role in maintenance of the orderly structure or in the formation of tight and gap junctions. This remains hypothetical, however, and additional studies are necessary in order to conclusively clarify this issue.

Animals↗
PubMed1981

Quantitative analysis of intramembranous particles in the membranous system of rat liver cells at different stages of development and aging.

The density of intramembranous protein particles was studied by freeze-fracture. Particle density on the fracture faces of the plasmalemma and the rough endoplasmic reticulum (RER), as well as the outer and inner membranes of the nucleus and the mitochondria in rat hepatocytes were quantified. Comparison among different age groups sampled days postcoitum (dpc), days postpartum (dpp), and months postpartum (mpp) showed age-related changes in particle density in each membrane system. With the exception of the RER, particle densities increased after the 16th dpc, reached a maximum at birth, and then decreased with increasing age. Simultaneously, the number of nuclear pores shows a positive correlation with the particle density of the nuclear membranes. The particle density on the membranes of the RER shows a maximum on the 16th dpc and on the 6th dpp. Thereafter, the density of the RER decreases slightly. In all membrane systems, the density of the particles on the external fracture faces is more variable than density of the particles on the protoplasmic fracture faces.

Aging↗
PubMed1981

Tissue connections in a transplantable virus-producing sebaceous adenoma of the mouse.

In this study a transplantable sebaceous adenoma is presented, which maintained its histological structure with similarities to normal sebaceous glands over a long series of transplantations. From the periphery toward the center a basal lamina, an outer layer of undifferenciated stem cells, loosely connected secreting tissue, a tightly packed zone of close cell attachment, and finally a central sebaceous zone can be distinguished. Special reference is made to the belt-like region around the zone of cell lysis and sebum accumulation, which forms a barrier to the surrounding tissue by means of numerous cell adhesions in the form of desmosomes. Relatively few virus particles of the retrovirus group, particularly type A particles, were found in any of the examined tumors.

Adenoma↗
PubMed1981

Electron-microscopic morphology of virus replication in cells of the murine Borstel-leukemia X 429.

Intraperitoneal injections of cell-free filtrates of Borstel-leukemia X 429 (immature-cell myeloid leukemia induced by 200 rad whole-body X-irradiation) were given to 330 1-week-old NMRI mice of both sexes. Leukemia developed in 21% after injection of cell-free filtrates from leukemic spleens and in 20% after injection of cell-free filtrates from leukemic lymph nodes. The mean time lapse from injection to the appearance of the leukemia was 12.8 months. The virus replication in the newly formed leukemic cells, was studied by electron microscopy. Special attention was given to the relation between A-particles and mature type-C viruses. The leukemia cells contain intracytoplasmic and intracisternal A-particles consisting of two concentric spherical shells with an external diameter of 70 nm. A-particles present mainly as closed "virus fields" in the vicinity of the cell nucleus, frequently in the Golgi area. The intracisternal A-particles appear inside the lumen of expanded vesicles of the cytoplasma. Typ-C viruses develop on the cytoplasmic membrane and/or on the outer cell membrane by condensation of crescent-shaped electron-dense zones. All layers of the later mature virus are recognisable in these early morphological stages. After the virus has been detached from the cell it collapses, and the outer membrane appears wrinkled. No spatial correlation between the storage sites of the A-particles and the sites of formation of mature type-C viruses are demonstrable.

Animals↗
PubMed1981

Paracrystalline inclusions in lysosomes of mouse kidney tubule cells induced by vinblastine and vincristine.

Following the simultaneous administration of vinblastine and vincristine, crystalline and paracrystalline structures were observed in the lysosomes of kidney tubule cells of mice. These structures appeared as hexagonal elements with an average diameter of 22 nm, with filaments about 5,5 nm thick located at each angle of the hexagons. They were formed following the aggregation and fusion of several mitochondria, probably from the mitochondrial cristae. In addition, highly osmiophilic, membrane-bound lysosomes were observed, which in cross-section exhibited regular arrays of straight membrane plates with a periodicity of about 10 nm. The extent to which, or even whether, these are associated with the above-mentioned paracrystalline inclusions could not be clearly established.

Animals↗