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Biomedical subjects

G Reuter

Publications and source records attributed to G Reuter.

At least 109 records · Page 6Linked to original sources
PubMed1992

Electrically evoked motile responses of mammalian type I vestibular hair cells.

Vestibular hair cells, type I and II, with membrane potentials around -64 mV were prepared from guinea pig ampullar cristae and maculae. In type I cells, current injection, application of voltage steps during membrane patch-clamping, or extracellular alternating current (ac) fields evoked fast length changes of 50 nm to 500 nm of the cell "neck." Mechanical responses were determined by computerized video techniques with contrast-enhanced digital image subtraction (DIS) and interpeak pixel counts (IPPC) or by double photodiode measurements. These techniques allowed spatial resolutions of 300 nm, 120 nm, and 50 nm, respectively. In contrast to measurements of high-frequency movements of auditory outer hair cells (OHCs), the mechanical responses of type I VHCs were restricted to low frequencies below 85 Hz. In addition to recently reported slow motility of VHCs, the present results suggest that fast mechanical VHC responses could significantly influence macular and cupular mechanics. Isometric and isotonic variants are discussed. The observed frequency maxima gap between VHCs and OHCs is suggested to contribute to a clear separation of the auditory and the vestibular sensory modality.

Animals↗
PubMed1992

[Mucociliary activity of free transplanted respiratory epithelium].

The function of free grafted respiratory epithelium was investigated in inbred rats. In nine of ten animals it could be shown that the respiratory epithelium not only regenerated as an epithelial surface lining but also regained mucociliary activity. The grafted epithelium was able to secrete mucus, which was equal in protein fragmentation to the secretion of normal nasal mucosa. The grafted respiratory epithelium showed normal ciliary function which could be demonstrated by recording the ciliary beat pattern present and by subsequent histological examination. Morphologically, a regular structure of ciliae (9 + 2) was found on the upper pole of the regenerated ciliated cells.

Animals↗
PubMed1991

Cellular differentiation after free grafting of respiratory epithelia.

Since there have been few investigations on the free grafting of respiratory epithelia, the aim of our present experiments was to establish whether it was possible to carry out such grafting in an animal model. Purebred strains of Lewis blood group rats were used to avoid host-versus-graft rejections of mucous membrane transferred from a donor to a recipient animal. Respiratory epithelia from the nasal septum were transplanted to the rectus abdominis muscle. Muscle and epithelial layers were then removed 4 months later. Using light and electron microscopy the function of the grafted ciliated epithelia--i.e. of the ciliated and goblet cells--could be demonstrated. These findings showed that respiratory epithelia heal when grafted onto a recipient site which has an adequate blood supply but do not lose their initial differentiation or functions. The results obtained in this experiment are important clinically for reconstruction of the respiratory tracts.

Abdominal Muscles↗
PubMed1991

Panagrellus redivivus: failure to find evidence for the occurrence and biosynthesis of sialic acids.

The occurrence of sialic acids in the free-living nematode Panagrellus redivivus was studied by periodate oxidation/[3H]sodium borohydride reduction of about 10(7) nematodes. In parallel, the capability of sialic acid biosynthesis was examined by metabolic labeling of the same number of nematodes with N-[3H]acetylmannosamine. In both experiments, radioactivity was incorporated into the nematodes. Mild acid hydrolysis, however, did not release radioactively labeled sialic acids or derivatives as tested by radio thin-layer chromatography, suggesting that P. redivivus does not contain or synthesize sialic acids.

Animals↗
PubMed1990

[Detection of verotoxin-producing E. coli (VTEC) in healthy cattle and swine with the DNA-DNA colony hybridization method].

With the DNA-DNA colony hybridization technique using specific gene probes for Verotoxin 1 (VT 1) and Verotoxin 2 (VT 2) 2100 E. coli strains from healthy animals were tested. Ten out of 82 milk cows (21.2%), 20 out of 212 beef cattle (9.4%) and five out of 75 pigs (6.7%) were found to carry genes for VT 1, VT 2 or both toxins, respectively. Among these strains the biotypes 5 and 6 were predominant. Some of the serotyped isolates have been described to be pathogenic for humans, like O157:H7, 082:H8, 0116, 0113, 0126 and 091, respectively. The unexpected high incidence of VTEC positive healthy animals possibly indicates a health hazard for human beings. Further investigations on the incidence of VTEC in food are necessary.

Animals↗
PubMed1990

Dependence of position-effect variegation in Drosophila on dose of a gene encoding an unusual zinc-finger protein.

Position-effect variegation is the inactivation in some cells of a gene translocated next to heterochromatin, the region of the chromosome that is permanently condensed. The number of copies of the Drosophila gene Suvar(3)7 is a dose-limiting factor in this phenomenon, and seems from its sequence that it encodes a protein with five widely spaced zinc-fingers. This novel arrangement of zinc-fingers could help in packaging the chromatin fibre into heterochromatin, and also reflect a novel method of controlling the expression from DNA domains.

Amino Acid Sequence↗
PubMed1990

Active radial and transverse motile responses of outer hair cells in the organ of Corti.

In isolated outer hair cells (OHCs) electrically induced movements of high frequencies have been described. The experiments, however, gave no information whether fast OHC motility exists in situ. In the present report, we developed a technique to prepare viable half turn explants from the guinea-pig cochlea which could be kept as organ culture. Several video imaging methods and pixel-by-pixel, digital-image subtractions allowed simultaneous observations and quantitative measurements at video rates of 688 x 512 localizations of investigated segments of the organ of Corti (OC). When living cochlea explants were exposed to an electrical a.c. field, the OHCs in the OC followed this field by shortenings and elongations of their cell bodies and by radial movements of their cuticular plates (CP). This was accompanied by radial displacements of the hair bundles. In the apical turns video stroboscopy allowed recording of in situ movements of OHCs up to auditory frequencies. In all experiments motile responses were most prominent in the three rows of the OHCs. No or less pronounced passive motile responses could be observed at the tunnel of Corti (TC) and in the inner hair cells (IHCs). Mechanical decoupling of OHCs and IHCs at the TC resulted in a loss of IHC movements, whereas OHCs were uneffected. Motility was detectable in the presence of physiological salt solutions (300 mOsm/l) and in iso-osmolar mannitol or sorbitol solutions. The electrically induced motile responses were not suppressed in the presence of dinitrophenol or cytochalasin B. Thus, the present report shows active transverse and radial motile responses of OHCs in the OC, which are electro-mechanical in situ processes. The results indicate how outer hair cell electromotility may influence hearing when it occurs within the mechanical framework of the OC.

Animals↗
PubMed1990

Detection and characterization of fecal verotoxin-producing Escherichia coli from healthy cattle.

Verotoxin-producing Escherichia coli isolates from feces of healthy cattle were identified by DNA hybridization with verotoxin 1- and verotoxin 2-specific gene probes. Among 259 animals investigated, 28 (10.8%) were found to carry verotoxin-producing E. coli strains. Characterization of the verotoxin-producing isolates revealed a heterogeneous population in terms of serotype and toxin type. Nearly 40% of the strains belonged to serogroups known to be pathogenic for humans, i.e., O22, O39, O82, O91, O113, O116, O126, and O136. Two isolates from different bulls were identified as serotype O157:H7. Results obtained in this study indicate that cattle may be an important source of verotoxigenic E. coli involved in human disease.

Animals↗
PubMed1990

[Definitive abdominal wall closure following palliative intervention for omphalocele and laparoschisis].

From 1975-1989 26 children underwent a definitive abdominal wall closure for palliative surgical treatment of omphalocele and gastroschisis in the Paediatric Surgical Clinic in Klinikum Berlin-Buch. The linear closure by mattress sutures by the method of Dick was not possible. Very good functional and cosmetic results were achieved with flap-plastic method of Brenner and overlapping it with autogenous corium-transplant. The favourable time for this operation is from the second to the third year of life.

Amnion↗
PubMed1989

[The surveillance of plant hygiene in the slaughtering process].

Basing on inspections of slaughterhouses it was tried to judge the effectiveness of the hygiene supervision implemented by the legislation. The organization of the control, the technological process including abattoir constructions and operations, the general hygienic aspects with special regard to cleaning and disinfection were registered. It is clearly demonstrated by grave examples (eg. wrong organization, insufficient employment of staff, incomplete knowledge, illegal practices) that nowadays in spite of a few exceptions, the supervision of hygiene in abattoirs is fragmentary. Paying attention to the conceptions of EEC committees dealing already with systematic controls, it would be well done to establish already known systems at once in the plants. According to the meat hygiene regulations exclusively official veterinarians are competent for this field of activities. These have to take the actual scientific knowledge into consideration.

Abattoirs↗
PubMed1989

Detection of an insensitive ornithine-carbamoyltransferase in strains of Pseudomonas syringae pv. phaseolicola with different phytotoxin-generating capacities.

Independently of their capacity to produce phytotoxins, strains of Pseudomonas syringae pv. phaseolicola contain two ornithine carbamoyltransferases (OCT, EC 2.1.3.3) which differ in resistance to phaseolotoxin and Orn-P(O) (NH2)-NH-SO3 H (PNSOrn). At 18 degrees C, the optimal temperature for product formation, the balance of the two types of OCT was shifted in favour of the insensitive type in phaseolotoxin producing strains, and in favour of the sensitive one in strains with little or no toxin production. The results suggest a causal relationship between the existence of an insensitive enzyme and the synthesis of toxins.

Drug Resistance↗
PubMed1989

Inhibition of ornithine carbamoyltransferase from Pseudomonas syringae pv. syringae W50 by phaseolotoxin.

In contrast to the producer of phaseolotoxin and Orn-P(O)(NH2)-NH-SO3H (PNSOrn), Pseudomonas syringae pv. phaseolicola, which possesses a sensitive and an insensitive type of ornithine carbamoyltransferase (OCT, E.C. 2.1.3.3.), in Pseudomonas syringae pv. syringae W50, an organism which produce neither phaseolotoxin nor PNSOrn, only one type of OCT could be detected. This enzyme is highly sensitive to phaseolotoxin. This result supports our hypothesis that the existence of an insensitive ornithine carbamoyltransferase is an important prerequisite for the synthesis of phaseolotoxin in P. syringae pv. phaseolicola and that this enzyme does not occur generally in P. syringae spec.

Drug Resistance↗
PubMed1989

Microbial synthesis of metabolites with antihypertensive activity: aspects of fermentation derived inhibitors of angiotensin-converting enzyme (ACE).

In this review the microbial angiotensin-converting enzyme inhibitors are described. Especially from the microbiological point of view the characteristics of these metabolites are given, e.g. occurrence, fermentation physiology and specificity. Besides these data, the structure, assays and some isolation problems are summarised. Apart from ACE inhibition the different biological activities of these secondary metabolites are discussed.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1989

A detailed study of the periodate oxidation of sialic acids in glycoproteins.

Periodate oxidation of terminal N-acetyl- and N-glycoloylneuraminic acid residues in the mucins from edible bird nest substance and pig submandibular gland, respectively, can be carried out under conditions which exclusively give rise to the formation of the C-7 analogues of these sialic acids. In contrast, the C-8 compounds can be obtained in a maximum yield of about 40%. Under identical conditions, N-glycoloylneuraminic acid is oxidized about 1.5 times faster than the N-acetylated derivative. After release of the sialic acids by acid hydrolysis, the characterization of the oxidation products was carried out by TLC, by GLC and GLC-MS of the corresponding pertrimethylsilyl derivatives, and by 500-MHz 1H-NMR spectroscopy. In addition, molar response factors for GLC analysis and extinction coefficients in the orcinol/Fe3+/HCl assay were determined.

Animals↗
PubMed1989

The genetics of position-effect variegation modifying loci in Drosophila melanogaster.

The dose dependent effects of position-effect variegation (PEV) modifying genes were studied in chromosome arms 2L, 2R and 3R. Four groups of PEV modifying genes can be distinguished: haplo-abnormal suppressor and enhancer loci with or without a triplo-effect. Using duplications four triplo-abnormal suppressor and four triplo-abnormal enhancer functions were localized. In two cases we proved that these functions correspond to a converse haplo-abnormal one. Altogether 43 modifier loci were identified. Most of these loci proved not to display significant triplo-effects (35). The group of haplo-abnormal loci with a triplo-effect may represent genes which play an important role in heterochromatin packaging.

Animals↗
PubMed1989

[A rare cause of rectal hemorrhage].

Report of a patient who discharged water and doughy stools since birth. At the age of 2 yrs. 10 mo. he had terry stools, a perforation of the sigmoid was caused by an ulcer, the perforation was oversewn. Further discharge of liquid stools. Rectoscopy, endoradiography, rectal biopsy with identification of gastric mucosa. 99mTc-pertechnetate was accumulated in the rectal mucosa. At the age of 4 years, demucosation and pull-through was done. A cleft vertebral body and a finger-shaped diverticulum were found and interpreted as sigmoid duplication. This is the only such case observed by us in 32 years.

Child, Preschool↗