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R Dermietzel

Publications and source records attributed to R Dermietzel.

At least 37 records · Page 2Linked to original sources
PubMed1989

Comparative characterization of the 21-kD and 26-kD gap junction proteins in murine liver and cultured hepatocytes.

Affinity-purified antibodies to mouse liver 26- and 21-kD gap junction proteins have been used to characterize gap junctions in liver and cultured hepatocytes. Both proteins are colocalized in the same gap junction plaques as shown by double immunofluorescence and immunoelectron microscopy. In the lobules of rat liver, the 21-kD immunoreactivity is detected as a gradient of fluorescent spots on apposing plasma membranes, the maximum being in the periportal zone and a faint reaction in the perivenous zone. In contrast, the 26-kD immunoreactivity is evenly distributed in fluorescent spots on apposing plasma membranes throughout the rat liver lobule. Immunoreactive sites with anti-21 kD shown by immunofluorescence are also present in exocrine pancreas, proximal tubules of the kidney, and the epithelium of small intestine. The 21-kD immunoreactivity was not found in thin sections of myocardium and adult brain cortex. Subsequent to partial rat hepatectomy, both the 26- and 21-kD proteins first decrease and after approximately 2 d increase again. By comparison of the 26- and 21-kD immunoreactivity in cultured embryonic mouse hepatocytes, we found (a) the same pattern of immunoreactivity on apposing plasma membranes and colocalization within the same plaque, (b) a similar decrease after 1 d and subsequent increase after 3 d of both proteins, (c) cAMP-dependent in vitro phosphorylation of the 26-kD but not of the 21-kD protein, and (d) complete inhibition of intercellular transfer of Lucifer Yellow in all hepatocytes microinjected with anti-26 kD and, in most cases, partial inhibition of dye transfer after injection of anti-21 kD. Our results indicate that both the 26-kD and the 21-kD proteins are functional gap junction proteins.

Animals↗
PubMed1989

cAMP delays disappearance of gap junctions between pairs of rat hepatocytes in primary culture.

Freshly isolated adult rat hepatocytes were found to be coupled through gap junctions, but coupling decreased abruptly 5-8 h after plating the cells on plastic culture dishes in physiological saline containing insulin and fetal calf serum. Loss of intercellular coupling was associated with disappearance of 27-kDa gap junction protein and of gap junctions seen by electron microscopy or immunocytochemistry. This disappearance of coupling was delayed approximately 8 h by treatment of the cultures with membrane permeant adenosine 3',5'-cyclic monophosphate (cAMP) [but not guanosine 3',5'-cyclic monophosphate (cGMP)] derivatives. Levels of gap junction protein and anatomically identified junctions were also maintained by 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP). Level of mRNA encoding the gap junction protein was maintained longer in cells treated with 8-BrcAMP than in untreated cells, but 8-BrcAMP did not detectably increase the transcription rate. Thus prolongation of coupling must result at least partially from extension of the lifetime of gap junction mRNA, allowing translation of message and assembly of channels for a longer period after plating. Treatment of cells with mRNA or protein synthesis inhibitors (alpha-amanitin and cycloheximide) prolonged coupling to a similar extent as did treatment with 8-BrcAMP. alpha-Amanitin blocked transcription of gap junction mRNA, but levels of cytoplasmic mRNA encoding the 27-kDa gap junction protein were maintained, presumably by block of transcription of an mRNA degrading factor. The factor is probably a protein, since a similar effect on mRNA level was produced in cycloheximide-treated cells. Cells cultured in control medium were also observed to flatten as they became uncoupled, whereas cells cultured for as long as 16 h in elevated 8-BrcAMP remained round and well coupled. The correlation between shape and coupling strength was not obtained after treatment with the microtubule stabilizing agent, taxol, which maintained the spherical shape of the cells but did not delay the disappearance of dye coupling. Nocodazole, which blocks microtubule formation, also maintained the spherical shape of the cells but delayed the disappearance of dye coupling. In addition to gating by covalent modification or other mechanisms, hormones and drugs that alter the intracellular cAMP concentration may affect intercellular communication by changing the lifetime of the mRNA encoding the main gap junction protein, thereby decreasing or increasing its synthesis. In addition, cAMP may act by decreasing removal of junctions from appositional membranes.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Immunochemical and immunocytochemical characterization of a novel monoclonal antibody recognizing a 140 kDa protein in cerebral pericytes of the rat.

A monoclonal antibody that recognizes a 140 kDa peripheral plasma membrane protein in pericytes of nervous tissues of the rat is described. Microvessels of brain cortex and perineurium of peripheral nerves are shown to react positively to this antibody. The antigen is absent in brain regions that lack a blood-brain barrier, i.e., choroid plexuses and area postrema. Antigen expression starts as early as day 18 of embryonic development. By means of immunoelectron microscopy the 140 kDa antigen was detected as clusters along the entire circumference of cerebral pericytes. The same antigenic determinant is also expressed in apical domains of plasma membranes of a variety of transporting epithelia, such as hepatocytes, enterocytes of the small intestine, and epithelial cells of proximal tubules of the kidney. We postulate the 140 kDa protein as being a constituent of the pericytes involved in regulative functions of the blood-brain barrier.

Animals↗
PubMed1988

Gap junction formation in rabbit uterine epithelium in response to embryo recognition.

Gap junction formation was studied in the uterine epithelium of nonpregnant, pregnant, and pseudopregnant rabbits in the periimplantation phase (6, 7, 8 days post coitum/post human gonadotropin injection) using freeze-fracture and immunocytochemistry as well as intracellular Lucifer yellow injection. At implantation (7 days post coitum) the uterine epithelial cells of the implantation chamber become junctionally coupled as evidenced by all three methods used. Gap junction protein (26K) becomes detectable immunocytochemically with a monoclonal antibody at 6 days post coitum in the epithelium surrounding the blastocyst, i.e., in the forming implantation chamber. The same sequence of events, starting with the presence of the gap junction protein before cell-to-cell coupling becomes evident, was observed in the blastocyst-free segments 1 day later. In contrast, uterine epithelium of nonpregnant and pseudopregnant animals in comparable phases shows an extremely low degree of coupling. The presence of the blastocyst is a necessary condition for the induction of gap junctions as demonstrated by unilateral pregnancy produced by tubal ligation. Thus, gap junction formation is one of the first maternal responses to a locally acting signal of the blastocyst.

Animals↗
PubMed1988

Organization of the actin filament cytoskeleton in the intestinal brush border: a quantitative and qualitative immunoelectron microscope study.

In the present study we have used immunogold labeling of ultrathin sections of the intact chicken and human intestinal epithelium to obtain further insight into the molecular structure of the brush-border cytoskeleton. Actin, villin, and fimbrin were found within the entire microvillus filament bundle, from the tip to the basal end of the rootlets, but were virtually absent from the space between the rootlets. This suggests that the bulk of actin in the brush border is kept in a polymerized and cross-linked state and that horizontally deployed actin filaments are virtually absent. About 70% of the label specific for the 110-kD protein that links the microvillus core bundle to the lipid bilayer was found overlying the microvilli. The remaining label was associated with rootlets and the interrootlet space, where some label was regularly observed in association with vesicles. Since the terminal web did not contain any significant amounts of tubulin and microtubules, the present findings would support a recently proposed hypothesis that the 110-kD protein (which displays properties of an actin-activated, myosin-like ATPase) might also be involved in the transport of vesicles through the terminal web. Label specific for myosin and alpha-actinin was confined to the interrootlet space and was absent from the rootlets. About 10-15% of the myosin label and 70-80% of the alpha-actinin label was observed within the circumferential band of actin filaments at the zonula adherens, where myosin and alpha-actinin displayed a clustered, interrupted pattern that resembles the spacing of these proteins observed in other contractile systems. This circular filament ring did not contain villin, fimbrin, or the 110-kD protein. Finally, actin-specific label was observed in close association with the cytoplasmic aspect of the zonula occludens, suggesting that tight junctions are structurally connected to the microfilament system.

Actinin↗
PubMed1987

Major loss of the 28-kD protein of gap junction in proliferating hepatocytes.

There is a reduction in the 28-kD gap junction protein detectable by immunofluorescence in livers of partially hepatectomized rats and in cultured hepatocytes stimulated to proliferate. By the coordinate use of antibodies directed to the hepatic junction protein (HJP28) and the use of a monoclonal antibody that recognizes bromodeoxyuridine (BrdU) incorporated into DNA, we have been able to study the relationship between detectable gap junction protein and cell division. Hepatocytes that label with BrdU in the regenerating liver and in cell culture show a significant reduction of HJP28. Cells that do not synthesize DNA, on the other hand, show normal levels and distribution of immunoreactive gap junction protein. We postulate that the quantitative changes in gap junction expression might play an important role in the control of proliferation in the liver.

Animals↗
PubMed1987

Simultaneous light and electron microscopic observation of immunolabeled liver 27 KD gap junction protein on ultra-thin cryosections.

We report on immunolabeling of gap junction protein in rat liver. Simultaneous light and electron microscopic immunolabeling of ultra-thin frozen sections was performed to confirm that the antigenic targets of polyclonal antibodies and a monoclonal 27 KD antibody (12/1 C5) are the gap junctions. Our results clearly demonstrate that the immunoreactive sites determined by indirect immunofluorescence correspond to immunogold-labeled gap junctions identified in the same section according to electron microscopic criteria. Our results also support the concept that the 27 KD protein is a major constituent of gap junctions.

Animals↗
PubMed1986

Reduced number of gap junctions in rat hepatocarcinomas detected by monoclonal antibody.

A new rat monoclonal antibody was characterized which recognized the 26K protein in gap junctions of mouse, rat and human liver as shown by immunoblot, indirect immunofluorescence, and immunogold electron microscopy. This monoclonal antibody was used to investigate the abundance of gap junctions in chemically induced rat hepatocarcinomas. In comparison with livers of control animals we found in hepatocarcinomas an average decrease of 71% in the number of gap junctional immunofluorescent spots. A corresponding decrease of the total amount of the 26 K protein was detected by quantitative immunoblot. Changes in the proliferative state as well as in intercellular adhesion of hepatocarcinoma cells in contrast to normal hepatocytes might have contributed to cause this decrease of gap junctions in tumor tissue. Possibly the partial loss of gap junctions provided a selective advantage for those preneoplastic liver cells which developed into rapidly proliferating tumor cells.

Animals↗
PubMed1986

Carbonic anhydrase in the sarcoplasmic reticulum of rabbit skeletal muscle.

Sarcoplasmic reticulum vesicles and mitochondria were prepared from red and white skeletal muscles of the rabbit. The preparations were characterized in terms of their specific activities of citrate synthase, basal (Mg2+-dependent) and Ca2+-dependent ATPase (the latter two in the presence of NaN3 and ouabain), and their specific carbonic anhydrase activities were determined. Skeletal muscle mitochondria had high specific activities of citrate synthase (700-1200 mu. mg protein-1) and low carbonic anhydrase activities (0.1-0.4 u. ml mg protein-1). The latter are likely to be due to a contamination of the preparations with sarcoplasmic reticulum (s.r.) Preparations of s.r. vesicles showed negligible activities of citrate synthase and the expected differing patterns of basal and Ca2+-dependent ATPase in red and white muscles. Specific carbonic anhydrase activities in s.r. from both muscle types were high (2-4 u. ml mg protein-1). The highest carbonic anhydrase activity, 11 u. ml mg protein-1, was found in s.r. from rabbit m. masseter. The inhibition constant of s.r. carbonic anhydrase towards acetazolamide was 4-6 X 10(-8) M and similar but not identical to that of cytosolic carbonic anhydrase II. It appears possible that the carbonic anhydrase II-like enzyme previously found by us in muscle homogenates (Siffert & Gros, 1982) originates from the s.r. Histochemical studies using the dansylsuphonamide method described previously (Dermietzel, Leibstein, Siffert, Zamboglou & Gros, 1985) showed an intracellular pattern of carbonic anhydrase staining compatible with the presence of the enzyme in s.r.: spots homogeneously distributed across the fibre cross-sections in transversely sectioned fibres and thin, longitudinally oriented, bands in longitudinally sectioned fibres. It is estimated that s.r. carbonic anhydrase accelerates CO2 hydration within the s.r. approximately 1000-fold. Thus, CO2 and HCO3- react fast enough to provide a rapid source and sink for protons leaving and entering the s.r. in exchange for Ca2+.

Acetazolamide↗
PubMed1985

Mapping of different neuropeptides in the lower brainstem of the rat: with special reference to the ventral surface.

A neuropeptide map of beta-endorphin-, vasoactive intestinal peptide-, substance P-, and somatostatin-like reactive neurons and nerve fibers was made by means of immunohistochemistry. Indirect immunofluorescence was carried out in parallel to peroxidase-antiperoxidase reaction using a modified fixation technique. Special interest was directed to the superficial ventral regions of the medulla oblongata where regulative centers for respiration and circulation have been localized. The atlas presented offers a reliable tool for a precise neuromorphological localization of these neuropeptides in pharmacophysiological experiments.

Animals↗
PubMed1979

[On the infectiousness of HBs-antigen-positive medical personnel (author's transl)].

Electronmicroscopic study of 29 HBs-antigen-positive personnel of a large hospital demonstrated virus material in the blood in all instances. In nine cases Dane particles, which are the infectious principle of the hepatitis B virus, were also seen. Dane-particle-positive personnel in a hospital could well be a risk to the patients if the carrier status or infectiousness of the person is not known.

Carrier State↗
PubMed1978

High risk groups for hepatitis B virus infection in a university hospital staff as determined by detection of HB antigens, antibodies, and Dane particles.

The prevalence of HBsAg and anti-HBs has been determined by solid-phase radioimmunoassay in 1815 university hospital employees and compared with the results obtained by investigating 131 metal workers and 86 laboratory technicians. Hospital personnel and here especially dialysis staff members and laboratory workers is at higher risk to acquire a hepatitis B virus infection than population compartments without contact to patients or blood. Electronmicroscopic studies revealed that a considerable number of the blood samples of HBsAg-positive staff members contained Dane-particles. These employees have to be considered infectious and possibly present a hazard to the patients they take care of.

Adolescent↗
PubMed1978

The oligodendrocytic junctional complex.

The junctional complex of oligodendrocytes was studied by means of different electron microscopical techniques. This complex is composed of the following junctional membrane formations: 1) tight junctional domains in the oligodendrocytic membrane near the some of the cells, 2) fasciae occludentes or focal tight junctions on the outer oligodendrocytic loop of myelin and on the outermost myelin membrane, 3) gap junctions of considerable size variations, either on membranes near the soma or on peripheral oligodendrocytic processes, and 4) non-paranodal transverse bands. The different types of oligodendrocytic junctions are discussed in terms of their functional implications.

Animals↗
PubMed1978

The microvascular pattern and perivascular linings of the area postrema. A combined freeze-etching and ultrathin section study.

The microvasculature and perivascular linings of the area postrema (A.P.) were studied electron microscopically with the ultrathin section and freeze-etching techniques. Special attention was given to the intercellular contacts of the different cellular entities. Two types of microvascular segments were identified. The endothelium of these vascular segments reveals fenestrations and a high pinocytotic activity. There are no significant differences in the frequency and distribution of the endothelial "openings" between both types of capillaries. The endothelium of the blood vessels, however, is joined by different types of tight junctions. Focal tight junctions occur between pericytes and the endothelium, and between leptomeningeal cellular elements in the perivascular space. The cell membrane of the perivascular glia shows intramembrane particles which are either distributed at random or organized in the form of membrane-associated orthogonal particle complexes (MOPC, Dermietzel, 1974). The significance of these findings is discussed with respect to the modified blood-brain barrier mechanism in the A.P.

Animals↗