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Biomedical subjects

H Riedel

Publications and source records attributed to H Riedel.

At least 55 records · Page 3Linked to original sources
PubMed1989

Cytoplasmic domains determine signal specificity, cellular routing characteristics and influence ligand binding of epidermal growth factor and insulin receptors.

The cell surface receptors for insulin and epidermal growth factor (EGF) both employ a tyrosine-specific protein kinase activity to fulfil their distinct biological roles. To identify the structural domains responsible for various receptor activities, we have generated chimeric receptor polypeptides consisting of major EGF and insulin receptor structural domains and examined their biochemical properties and cellular signalling activities. The EGF-insulin receptor hybrids are properly synthesized and transported to the cell surface, where they form binding competent structures that are defined by the origin of their extracellular domains. While their ligand binding affinities are altered, we find that these chimeric receptors are fully functional in transmitting signals across the plasma membrane and into the cell. Thus, EGF receptor and insulin receptor cytoplasmic domain signalling capabilities are independent of their new heterotetrameric or monomeric environments respectively. Furthermore, the cytoplasmic domains carry the structural determinants that define kinase specificity, mitogenic and transforming potential, and receptor routing.

Animals↗
PubMed1989

[The effect of age on the periodontal status of the golden Syrian hamster (morphologic research)].

In 10 male Syrian golden hamsters at the age of 3, 4, 5, 6 or 7 months each the two first lower molars have been evaluated histomorphologically to get an exact statement about the spontaneous illness rate of our used animals. In this connection efforts were made to classify the histopathological lesions into initial, early, established and advanced lesions in accordance with Page and Schroeder (1976). Altogether occurred 4 initial, 64 early and 32 established lesions in 100 examined golden hamster molars. In no case advanced lesions have been stated. Referring to the various age groups a regular periodontal progression was not detectable. Histologically healthy marginal periodontium could not been found in the conventional Syrian golden hamster. Similar examinations have this to consider.

Aging↗
PubMed1988

Ligand activation of overexpressed epidermal growth factor receptors transforms NIH 3T3 mouse fibroblasts.

The cell surface receptor for the mitogenic peptide epidermal growth factor (EGF) is involved in control of normal cell growth and may play a role in the genesis of human neoplasia such as squamous carcinoma and glioblastoma. Soft-agar growth and focus-formation experiments with NIH 3T3 mouse fibroblasts transfected with an expression plasmid demonstrated the ligand-dependent transforming potential of the human EGF receptor without structural alterations. Activation of overexpressed normal receptor alone appears to be sufficient for transformation of NIH 3T3 cells in vitro.

Animals↗
PubMed1988

[Liver morphology and clinical aspects of a case of cholesterol ester storage disease].

Liver specimen morphology and clinical course of a case of cholesterol ester storage disease are presented. In a 16-year-old boy on the first biopsy a massive storage of neutral fats was found light microscopically and of cholesterol ester micropolariscopically. Advanced portal field fibrosis and severe reactive hepatitis indicate the danger of progression up to metaplasia. Typical membrane-surrounded lipid inclusions were found electron microscopically in hepatic cells, stellate cells and also in bile duct epithelium.

Adolescent↗
PubMed1988

[The morphology of skin damage in porphyria cutanea tarda (PCT)].

Skin biopsies (fresh and old blisters) of the back of the hand and lower arm, respectively, obtained from 24 patients with clinically and biochemically established porphyria cutanea tarda have been examined light and electron microscopically, 15 out of them also by immunofluorescence microscopy (occurrence of IgG, IgM and C3). Light microscopically there were subepidermal blisterings and typical corial broadenings of the capillary wall with deposits of diastase-resistant PAS-positive material in and around the walls of the vessels. Electron microscopically, replications of the capillary basement membrane with deposits of amorphous material were observed. IgG and C 3 on the dermoepidermal junction and in the capillaries could be identified by means of the direct immunofluorescence method in a number of cases. The pathogenesis of the lesions of the vessel walls and that of the subepidermal blistering, hitherto interpreted as their consequence, is not yet clarified sufficiently.

Basement Membrane↗
PubMed1987

A chimeric, ligand-binding v-erbB/EGF receptor retains transforming potential.

Comparison of amino acid sequences from human epidermal growth factor (EGF) receptor and avian erythroblastosis virus erbB oncogene product suggests that v-erbB represents a truncated avian EGF receptor gene product. Although both proteins are transmembrane tyrosine kinases, the v-erbB protein lacks most of the extracellular ligand-binding domain and a 32-amino acid cytoplasmic sequence present in the human EGF receptor. To test the validity of the proposed origin of v-erbB and to investigate the functional significance of the deleted extracellular sequences, a chimeric gene encoding the extracellular and the transmembrane domain of the human EGF receptor joined to sequences coding for the cytoplasmic domain of the avian erbB oncogene product was constructed. When expressed in Rat1 fibroblasts, this reconstituted gene product (HER-erbB) was transported to the cell surface and bound EGF. Its autophosphorylation activity was stimulated by interaction with the ligand. Expression of the HER-erbB chimera led to anchorage-independent cell growth in soft agar and EGF-induced focus formation in Rat1 monolayers. Thus, it appears that v-erbB protein sequences in the chimeric receptor retain their transforming activity under the influence of the human extracellular EGF-binding domain.

Animals↗
PubMed1986

[Therapeutic and pathogenetic aspects of porphyria cutanea tarda].

Seventy-three patients with porphyria cutanea tarda (PCT) were treated with chloroquine phosphate, which was administered in doses of 250 mg twice a week for more than 1 year on average. Of these patient, 49% did not have any associated ("inducing") factors. After treatment, serum transaminases and gamma-glutamyltransferase (gamma-GT) always returned to normal values. However, gamma-GT did not reach the normal range in the group without associated factors ("idiopathic group"). Of the 66 patients studied, 25 achieved an approximately physiological distribution of the pattern of urinary porphyrin fractions. Control biopsies were performed in 66 patients. Of them, 48 patients showed an improvement in liver damage. A statistically significant correlation was observed between a lasting increase in urinary prophyrin content and unchanged pathological liver morphology. A pathogenesis concept for PCT is discussed as a disease between inheritance (genetic enzyme defect) and environment ("inducing factors"). Even in the "idiopathic group" the improvement of pathological liver changes after therapeutic removal of the pathological prophyrin content in the liver cells shows that porphyrins could also cause liver damage.

Alcoholism↗
PubMed1985

Different membrane anchors allow the Semliki Forest virus spike subunit E2 to reach the cell surface.

The Semliki Forest virus spike subunit E2, a membrane-spanning protein, was transported to the plasma membrane in BHK cells after its carboxy terminus, including the intramembranous and cytoplasmic portions, was replaced by respective fragments of either the vesicular stomatitis virus glycoprotein or the fowl plague virus hemagglutinin. The hybrid proteins were constructed by cDNA fusion. Upon a transient expression they could be localized at the cell surface by immunofluorescence with specific antibodies directed against any of the protein fragments.

Antigens, Surface↗
PubMed1984

Cell surface expression of fusogenic vesicular stomatitis virus G protein from cloned cDNA.

Vesicular stomatitis virus (VSV) enters the host cell by the receptor-mediated endocytotic pathway. This brings the virus particle into acidic vesicles inside the cell where infection occurs through a fusion event between the viral and the host vesicle membrane. In this work we have shown that the VSV glycoprotein (G) carries the fusion activity of this virus. The G protein was expressed on the surface of baby hamster kidney 21 cells from cloned cDNA which had been engineered into an expression vector and introduced into cell nuclei with the aid of a glass microneedle. A short (60 s) treatment with acid (pH less than or equal to 6.0) medium induced fusion of cells having G protein on their surface. For efficient G protein expression and cell-cell fusion we had to trim the 5' end of the G cDNA and to use as promoter the long terminal repeat of the mouse Moloney sarcoma virus.

Animals↗
PubMed1983

Numerosity estimation with successive presentation: item organization.

Previous studies have shown that, with simultaneous presentation, highly organized patterns were overestimated in number compared with random patterns. In an exploratory attempt to apply Das et al.'s model of simultaneous and successive cognitive processes to perception, 62 Ss were asked to estimate the number of items presented visually one at a time. A rate of one item per second was used, and Ss were required to read each item aloud in order to prevent counting. When the stimuli were digits, no difference was found in the estimates for sets of stimuli containing high information vs those containing low information. When words were used as stimuli, estimates were significantly lower for words in sentences than for the same words in random order.

Discrimination Learning↗
PubMed1983

[Paracrystalline needle-shaped cytoplasmic liver cell inclusions in chronic hepatic porphyria--light and electron microscopic examination of liver biopsy specimens].

Paracrystalline needle-shaped cytoplasmic liver cell inclusions could be identified by light and electron microscopic examinations of 19 liver biopsy specimens in chronic hepatic porphyria. Light microscopically, they occurred in 6 cases, electron microscopically they were found in 13 ones. In the electron microscope these inclusions displayed tubular substructures with enhanced contrast of the membranes. They are specific for chronic hepatic porphyria; their light microscopic identification is of diagnostic value. Membranous material occurring in cisternae of the endoplasmic reticulum and adjacent to pigments and inclusions has not been described so far and is discussed with regard to its origin. Alterations of mitochondria and endoplasmic reticulum, observed in all cases, point to a general liver cell damage in chronic hepatic porphyria. Up to the present, the chemical structure and pathogenesis of the inclusions are still unknown.

Adult↗