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R Dermietzel

Publications and source records attributed to R Dermietzel.

At least 127 records · Page 7Linked to original sources
PubMed1977

In vivo and in vitro formation of the junctional complex in choroid epithelium. A freeze-etching study.

The junctional complex of choroid epithelial cells was studied during in vivo formation, disaggregation after trypsin treatment, and in vitro reaggregation. The in vivo formation begins with the occurrence of amorphous patches of particles followed by the formation of small particulate rows and polygonal-ordered particle assemblies. Further arrangement of the zonula occludens continues with the confluence of particles and smooth contoured ridges. At the 9th day stage a fully developed zonula occludens has developed. In a subsequent step nexus become integrated within the tight junction formation. Disaggregation after trypsination results in fragmentation of the zonulae occludentes. Parts of the disassembling aggregates become incorporated in vacuoles indicating an endocytotic mode of "digestion". The in vitro reconstruction of the zonula occludens proceeds from remnants of the former zonula occludens. On the 3rd to 4th day of cultivation mature tight junctions are visible. In vitro integrations of nexus were observed during a later phase. On the 7th day, cultivated choroid epithelial cells reveal well differentiated junctional complexes consisting of continuous zonulae occludentes and integrated gap junctions.

Animals↗
PubMed1977

[Permeability of dialysis membranes for hepatitis-B virus: on the prophylaxis of hepatitis in a haemodialysis centre (author's transl)].

Dialysis fluids of two hepatitis-Bs (HBs) antigen-positive dialysis patients were tested for hepatitis-B virus. Total dialysate volume of 5.5 litres each - as obtained on haemodialysis with the Redy-recirculation system - was concentrated by ultrafiltration and trap and rate-zonal ultracentrifugation, followed by fractionation, and purified. Electron-microscopic evidence of permeability of an intact dialysis membrane for hepatitis-B was obtained. Concentration of hepatitis-B virus was at least 10(3) to 10(4) particles per total volume. Because of the potential infectiousness of the dialysis apparatus by effective heat sterilisation after every dialysis is essential.

Adolescent↗
PubMed1977

Hepatocarcinogenesis by thioacetamide: correlations of histological and biochemical changes, and possible role of cell injury.

Hepatocarcinogenesis in rats produced by prolonged feeding of thioacetamide appears as a progressive phenomenon in which morphological changes are associated with important biochemical modifications. It seems most likely that changes in the permeability of cell membrane induced by the carcinogen are responsible for increased intracellular accumulation of Ca2+, and for the ensuring of cell injury produced by Ca2+ overloading of the mitochondria. This calcification of the mitochondria may play a role in the neoplastic transformation of the cell, especially as far as it concerns metabolic behavior and the genetic specification of the permeability characteristics of the transformed cell membrane. The increased synthesis of acid glycosaminoglycans suggests their involvement in calcium-mediated control of tumor development and growth.

Acetamides↗
PubMed1977

[Morphological alteration and desintegration of dane particles after exposure with "Gigasept". A first methological attempt for the evaluation of the virucidal efficacy of a chemical disinfectant against hepatitisvirus B ( author's transl)].

A test system based on morphological alterations and desintegration of hepatitis virus B (HBV) is presented for the approximative evaluation of the virucidal efficacy of a chemical disinfectant. Dane particles, supposed to be the infectious entity of HBV, were partially purified by a trap and a rate zonal ultracentrifugation from serum samples of a patient with chronic hepatitis undergoing an immune suppressive treatment because of leukemia. "Gigasept" on the basis of succine dialdehyd and formaldehyd served as disinfectant for this investigation. In one experiment partially purified Dane particles were exposed to the action of a 5% solution of "Gigasept" on electron microscopic grids. Morphological alterations resulting in derounding, break up of the outer membrane, spiral uncoiling as well as asymmetric enlargement of the space between the outer membrane and the core of the HBV was observed after 2 mins. After 15 mins, the HBV were diffusely stained with loss of the characteristic substructure and became polygonal. The decrease of the number of the particles was proportional to the length of the contact time with the disinfectant. In a second series equal volumes of a 5% solution of "Gigasept" and of a HBV containing serum were in contact for 2 hours, with consecutive purification and morphological characterization of the HBV. The sedimentation of the HBs antigenicity differed from the control. A part of the Dane particles was diffusely stained and lost its substructure. Moreover empty particles in the range of the HBc antigen were found. Another part of Dane particles, however, was morphologically unchanged. The relation of intact and non intact particles could possibly serve as parameter for the HBV virucidy.-Thermo inactivation (3 mins, +98 degrees C) of the HBV in a serum was undertaken for comparison.

Aldehydes↗
PubMed1976

Liver tumors induced by 4-dimethylaminoazobenzene: experimental basis for a chemical carcinogenesis concept.

In animals fed 4-dimethylaminoazobenzene there are modifications in the distribution of extra- and intracellular cations in liver. The correlation between the cell ionic permeability changes and the induction of cholangiocarcinoma or hepatoma is analyzed at the light of the histological and biochemical findings. A new concept of chemical carcinogenesis is stated in which the increase of passive Ca2+-influx produces mitochondria damage associated with permanent modifications of the structural and functional characteristics of the cell membranes as well as of the genetic mechanisms controlling cell division.

Adenoma, Bile Duct↗
PubMed1976

On the role of tumor cell surface in the accumulation of radioisotopes.

The effects of electrical charge and structural modifications of the ascites tumor cell surface on the uptake of several radiocompounds have been investigated. Changes in its electrical surface charge provoke variations in the radioactivity incorporation which appear to be selective for chelated or ionic radioisotopes. The release of a part of the cell "coat" by EDTA affects profoundly the incorporation of radioisotopes in a process which seems to be related to cell membrane permeability changes. The relationships between cell surface changes and radiocompounds accumulation are discussed.

Animals↗
PubMed1975

Junctions in the central nervous system of the cat. V. The junctional complex of the pia-arachnoid membrane.

The leptomeningeal tissue of the choroid plexuses and of the brain surfaces have been studied by means of the freeze-etching technique. The pia-arachnoid membrane and the subdural neurothel represent the morphological barrier between the extracerebral tissue and the cerebrospinal compartment. The freeze-etch findings indicate that the arachnoid and neurothelial cells are coupled by extensive zonulae occludentes which seem to represent the structural basis of the barrier mechanism provided by these cell layers. Furthermore, it became evident that gap junctions of considerable structural heterogeneity occur on the pial and arachnoid cells of the interstitial choroidal compartment and of the free brain surfaces. The structural heterogeneity of the nexuses is taken as an indication of the plasticity of the leptomeningeal tissue. The different morphological characteristics of the nexal formations are discussed with respect to their probable functional meaning.

Animals↗
PubMed1975

Junctions in the central nervous system of the cat. IV. Interendothelial junctions of cerebral blood vessels from selected areas of the brain.

Interendothelial membrane contacts in different segments of brain blood vessels were investigated by the freeze-etching technique. The study demonstrated that the endothelial cells of the pre- and postcapillary segments were coupled by elaborate zonulae occludentes. These tight junction formations encompassed gap junctions of different sizes and distribution. The globules of the pre- and postcapillary tight junctions revealed a great fragility which led to an atypical distribution of the sealing elements. In the "typical" brain capillaries the endothelial cells were connected by continuous tight junctions. In contrast to the structural continuity of these formations the fenestrated segments of capillaries in the choroid plexus and area postrema demonstrated discontinuous fasciae occludentes. They were composed of rows of individual particles which should be regarded primarily as focal in nature.

Blood-Brain Barrier↗
PubMed1975

A complex junctional system in endothelial and connective tissue cells of the choroid plexus.

Endothelial and connective tissue cells of the choroid plexus have been studied by the freeze-etching technique. The endothelial cells of pre- and postcapillary segments are coupled by a complex junctional system consisting of a combination of tight and gap junctions. Connective tissue cells revealed the same intercellular contacts. Furthermore two different types of gap junctions occurring in membranes of the connective tissue cells are described.

Animals↗