Demonstration of an intercellular substance in mouse cerebral cortex

Summary Specimens of mouse cerebral cortex were preserved by freezing and drying and treated in vacuo with osmium tetroxide vapors. In the neuropil of the molecular layer dense, osmiophilic laminae, presumably plasma membranes of immediately adjacent cell processes, were found to be separated by an intercellular space, which appeared relatively electron lucent in unstained sections. In sections stained with uranyl acetate an intercellular substance was demonstrated, the visualized density of which was reduced when staining was accomplished at low pH. These reactions suggest the presence of a non-lipid, anionic intercellular substance which may contain acid mucopolysaccharide.This work was supported by U.S.P.H.S. Research Grants NB 05175, NB 07044 and Career Development Award 1K3 NB 4929.     

Electron microscopic investigation of water occlusions in intercellular spaces in the inner cortex of lucerne nodules.

It is unclear to what extent oxygen diffusion pathways through the cortex of the nitrogen-fixing zone of indeterminate nodules are liquid filled and whether a blockage of these pathways is involved in varying nodule oxygen permeability to control nitrogenase activity. We examined the proportion of water-filled intercellular spaces of lucerne (Medicago sativa L.) nodules with cryo-scanning electron microscopy. This technique allows for direct observation of water accumulation. Thirty percent of all intercellular spaces in the inner cortex of lucerne nodules were liquid filled. Decreasing the nodule oxygen permeability by detopping of the plant or by increasing the rhizospheric oxygen partial pressure to 80 kPa had no statistically significant effect on the water distribution in the intercellular spaces. Therefore, the hypothesis of a continuous aqueous diffusion barrier in the inner cortex could not be supported. The abundance of glycoproteins in intercellular spaces of the inner cortex was investigated with immunoelectron microscopy. No alteration due to detopping or after increase of the rhizospheric oxygen partial pressure was observed. Therefore, our results do not support the hypothesis of a short-term regulation of oxygen permeability by blockage of diffusion pathways through morphological changes in the cortex region of the nitrogen-fixing zone of lucerne nodules.     

Electron microscopic cytochemical and morphometric study of the cerebral cortex synapses in postmortem autolysis

Brain tissue staining with phosphotungstic acid was performed to assay neurofilament accumulations in synapses in the molecular layer of the rat cerebral cortex at different intervals after the animals' death. It was found that autolysis began in the dense projections of presynaptic grid. Within 30 min autolysis developed in mature and very young (immature) synapses. By the 90th min autolysis in asymmetric synapses was considerably enhanced. 6 hours later autolysis involved mature and indefinite synapses.     

Electron microscopic and radioautographic data on the synthesis of RNA and chromatin structure in cells of the rat cerebral cortex

The intensity of RNA synthesis in cells of the rat brain hemispheres (neurons, astrocytes, oligodendrogliocytes, microgliocytes) was studied by electron microscopic radioautography, and the data obtained were compared with dispersed to condensed chromatin area ratio. The correlation was found between the level of RNA synthesis and dispersed chromatin area. High chromatin dispersity in neuron and intensive NA synthesis in the extranucleolar part of the nucleus made it possible to assume the existence of depression of an especially large genome part and the variability of the proteins produced by this cell.     

Electron microscopic evidence of an immobilized living cell system

Whole cells of Rhodopseudomonas capsulata were immobilized by entrapment in Ca²⁺ alginate gel. The cell growth inside the matrix was observed by transmission electron microscopy. Colonies enlarged upon incubation, giving some evidence of an immobilized living cell system. This observation was correlated by measurements of bacteriochlorophyll, nitrogen, and protein content.     

Electron microscopic evidence for the reversible transformation ofEuonymus plastids

Contradictory concepts on whether the differentiation of plastids is monotropically directed or reversibly transformable with one another have been argued for a long time. In the present report, the evidence to support the latter concept, i.e. the reversible transformation, will be presented. The seasonal yellowing and regreening ofEuonymus leaves were observed by means of electron microscopic study. In the yellowing of chloroplasts during winter, plastoglobules appeared in the plastid stroma and increased in number according to the disintegration of lamellae; then the degenerated chloroplasts (chromoplasts) were filled up with these plastoglobules. In the next spring, however, regreening of the yellowed leaves took place; the lamellae were regenerated in the chromoplasts to again restore the normal chloroplast structure. Infolding of the inner membrane was never observed in these regreening plastids. The number of plastoglobules in the plastids decreased as the lamellae regenerated, and the chlorophyll content increased. These observations suggest that the plastoglobules in chromoplasts (plastids in yellowed leaves) are made of material of the disintegrating lamellae and are re-used as the source of supply for the reformation of lamellae in the spring reversal.     

Electron microscopic evidence for a muscle layer in the wall of the terminal hepatic venule in the rat

Summary Electron microscopically smooth muscle cells could be detected in the walls of the terminal hepatic venules of the rat liver. These muscle cells are double layered in the following venous channels, the intercalated veins. It is supposed that these smooth muscle cells play an important role as outlet sphincters of the liver sinusoids. Furthermore, fenestrations could be found in the endothelial lining of terminal hepatic venules.Dedicated to Prof. Dr. Drs. h.c. W. Bargmann on his 70th birthday.Supported by a grant of the Deutsche Forschungsgemeinschaft.     

Further evidence for the existence of an intrinsic bicarbonate-stimulated Mg2+-ATPase in brush border membranes isolated from rat kidney cortex

Summary The aim of this study was to provide further evidence for the existence of a nonmitochondrial bicarbonate-stimulated Mg²⁺-ATPase in brush border membranes derived from rat kidney cortex. A plasma membrane fraction rich in brush border microvilli and a mitochondrial fraction were isolated by differential centrifugation. Both fractions contain a Mg²⁺-ATPase activity which can be stimulated by bicarbonate. The two Mg²⁺-ATPases are stimulated likewise by chloride, bicarbonate, and sulfite or inhibited by oligomycin and aurovertin, though to different degrees. In contrast to these similarities, only the Mg²⁺-ATPase activity of the mitochondrial fraction is inhibited by atractyloside, a substance which blocks an adenine nucleotide translocator in the inner mitochondrial membrane. On the other hand, filipin, an antibiotic that complexes with cholesterol in the membranes inhibits exclusively the Mg²⁺-ATPase of the cholesterol-rich brush border membranes. Furthermore it could be demonstrated by the use of bromotetramisole, an inhibitor of alkaline phosphatase activity, that the Mg²⁺-ATPase activity in the membrane fraction is not due to the presence of the highly active alkaline phosphatase in these membranes. These results support the assumption that an intrinsic bicarbonate-stimulated Mg²⁺-ATPase is present in rat kidney brush border membranes.     

Immunocytochemical evidence for the presence of an albumin-like substance in the rat pineal gland

Summary Two rabbits and two guinea pigs were immunized with arginine vasotocin (AVT) conjugated to bovine albumin with glutaraldehyde. Only one preparation of antiserum (anti-G 7) was of value. Anti-G 7 immunochemically defined the same rat pineal cells previously reported as presumptive AVT cells. However, absorption of anti-G 7 with bovine albumin inhibited the staining of the pineal cells demonstrating that they contained an albumin-like substance. Positive immunochemical staining of the rat pars nervosa suggested that anti-G 7 contained antibodies able to react with arginine vasopressin (AVP). Loss of a positive reaction in the posterior lobe on absorption of anti-G 7 with AVT or AVP confirmed this. However, the addition of AVT to anti-G 7 failed to inhibit the immunochemical staining of the pineal cells. This study reports the presence of an albumin-like substance in pineal cells previously described as presumptive AVT cells, and discusses possible explanations for the inability of anti-G 7 to recognize immunocytochemically the native AVT molecule. Confirmation of AVT in the pineal gland by immunocytochemistry must await the availability of more specific antisera.     

Electron microscopy study of microcirculation in the rat cerebral cortex after total neutron irradiation

It was established that the ultrastructure of blood capillaries of the brain changes during the first six hours following whole-body neutron irradiation of rats (10 Gy) which was indicative of the capillary wall swelling, the increase in the microcirculatory bed permeability, and pericapillary edema development. Those processes seemed to be reversible since during this period no severe destructive changes were detected in the microvessel wall.     

Electron microscopic and histochemical study of the localization of adenylate cylase and acetylcholinesterase in the synapses of the rat cerebral cortex and basal ganglia]

Synapses of the brain cortex and basal ganglia of the rat were studied by means of electron histochemical reactions to adenylate cyclase and acetylcholinesterase. Three types of synapses, viz. cholinergic, adrenergic and mixed, were identified. Typification was carried out on the basis of presynaptic terminal vesicle characteristics and localization of the mentioned enzymes of the synapse receptor area.     

Immunohistochemical evidence for the existence of rat cytosolic sialidase in rat skeletal muscles

 Histochemical evidence is required to demonstrate the presence of biochemically defined cytosolic sialidase. To meet this requirement, we examined the immunohistochemical localization of the enzyme in rat skeletal muscles. Sections of chemically fixed tissues were incubated with a polyclonal antibody raised against a synthetic peptide which corresponded to a part of the enzyme protein. After incubation with the primary antibody, cryosections for fluorescence microscopy and resin sections for electron microscopy were incubated with a fluorochrome- and colloidal gold-labeled secondary antibody, respectively. Immunofluorescence was diffusely distributed in the muscle fibers and was also found in the perimysium and blood vessels. Many immunogold particles were scattered over the sarcoplasm, myofibrils, nucleoplasm, and matrix of mitochondria. The immunogold particles were also found in the equivalent compartments of axons, Schwann cells, and cells of endomysium and blood vessels. The specificity of the primary antibody was elucidated by immunoblotting and an immunoprecipitation test. These findings clearly indicate that this type of sialidase is essentially located in the cytosolic compartment. Consequently, the name, cytosolic sialidase, will be appropriate for this enzyme. Additionally it is indicated that this enzyme is also present in cells other than skeletal muscle fibers. Accepted: 29 January 1997     

Electron microscopic autoradiography for demonstration of pineal serotonin in rat

Summary The fine localization of rat pineal serotonin has been studied by means of electron microscopic autoradiography. Two hours after the intravenous injection of tritium labelled 5-hydroxytryptophan, the location of large number of silver tangled threads is seen in the sympathetic nerve terminals. There is also a less specific accumulation of the silver grains in the pinealocytes, some appearing in the cytoplasmic organelles and some in the nucleus.In quantitative terms, 43% of the total count of silver grains were in the nerve endings whereas pinealocytes, which comprise a much larger volume of the section, contain a proportionally much smaller number of silver particles (53%). Furthermore the perivascular spaces, which comprise a larger percentage in volume of the section than the nerve endings has nevertheless only about 4% of the grains counted.Although the precise localization of the silver grains is obscure, the reaction of the granulated vesicles in the nerve terminals to the double fixation used, is similar to that shown by the extremely dense material in vesicles of platelets, which was demonstrated to contain serotonin. The results therefore suggest that the silver grains appearing in the nerve terminals two hours after the administration of 5-hydroxytryptophan are in the serotonin binding site in the axon terminals, containing the granulated vesicles.     

Further evidence for the existence of intralobular nerves in the rat liver

Summary In a recent study (Skaaring and Bierring, 1976) we found cholinesterase positive nerve-like structures in the lobules of rat liver, and scanning electron microscopy revealed cords having a distribution pattern similar to that of the cholinesterase-positive structures. To obtain further evidence for an intralobular nerve supply the methods of cobalt and Procion Yellow nerve staining (Stretton and Kravitz, 1968; Iles and Mulloney, 1971; Pitman, Tweedle and Cohen, 1972) were adapted, iontophoretic introduction of the dyes being attempted through cut axonal ends in the surface of small excised blocks of rat liver.