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Biomedical subjects

G Walter

Publications and source records attributed to G Walter.

At least 235 records · Page 13Linked to original sources
PubMed1981

[Sclerosing mesenteritis: case reports and review of literature (author's transl)].

Sclerosing mesenteritis is a rare, non-systemic disease confined to the mesenteric adipose tissue and typified by a variety of inflammatory pseudo-tumours. Histological investigation uncovers a wide spectrum of pathological changes, with collections of foam cells, fibrosis and for the most part sparse mononuclear inflammatory infiltrates in the mesenteric fat tissue. In the course of several weeks to months the pseudotumours generally resolve without therapeutic measures. The disease entity is discussed on the basis of three clinical cases.

Adipose Tissue↗
PubMed1981

[A study on the transmission (transstadial, transovarial) of Babesia microti, strain "Hannover i", in its tick vector, Ixodes ricinus (author's transl)].

Transstadial, transovarial and combined transstadial-transovarial transmission of Babesia microti in its tick vector, Ixodes ricinus, was studied. The ticks used (larvae, nymphs, females) were part of the progeny of nymphs collected in an area nearby Hanover. Specimens to be infected alimentarily were fed on parasitaemic Golden Hamsters (Mesocricetus auratus). The ability to infect mammalian hosts of a tick stage was examined by feeding it on negative Golden Hamsters. B. microti was found to be transmitted transstadially from the alimentarily infected larva to the following nymphal stage, only. Thus, this nymph is the only stage transmitting the Babesia to mammalian hosts. Transovarial transmission could not be observed.

Animals↗
PubMed1980

Antibodies specific for the carboxy- and amino-terminal regions of simian virus 40 large tumor antigen.

Antibodies specific for the amino- and carboxy-terminal portions of simian virus 40 large tumor (T) antigen were obtained by immunization of rabbits with synthetic peptides corresponding to these regions. The amino-terminal synthetic peptide has the sequence Ac-Met-Asp-Lys-Val-Leu-Asn-Arg-(Tyr). The tyrosine residue was introduced in order to couple the peptide to bovine serum albumin with bis-diazotized benzidine. The carboxy-terminal peptide has the sequence Lys-Pro-Pro-Thr-Pro-Pro-Pro-Glu-Pro-Glu-Thr. It was coupled to bovine serum albumin with glutaraldehyde. The antisera against both peptides reacted with large T antigen. The specificity of the immune reaction was demonstrated by inhibition experiments using excess synthetic peptides. Furthermore, fragments of T antigen encoded by the nondefective adenovirus 2-simian virus 40 hybrid viruses Ad2+ND2 and Ad2+ND4, which contain the carboxy terminus and lack the amino terminus of large T antigen, were precipitated only with antiserum to the carboxy-terminal peptide. Small T antigen was not precipitated with either serum, suggesting that the amino terminus of small T antigen has a conformation different from that of large T antigen or that it is sterically hindered by a host protein. The procedures used here are of general importance for identification and characterization of gene product.

Adenoviruses, Human↗
PubMed1980

[Studies of the ecology of some blood protozoa of wild small mammals in North Germany (author's transl)].

In 1977 and 1978, 696 small mammals of 9 different species were surveyed for protozoal blood parasites. The following parasites were found: Hepatozoon sylvatici in Apodemus flavicollis, H. erhardovae and Trypanosoma evotomys in Clethrionomys glareolus, T. microti and Babesia microti in Microtus agrestis and T. croicidurae in Crocidura russula. H. erhardovae showed regularly high infection-rates (more than 70%) during all the years in 1977 and 1978. H. sylvatici was found only in 5.6% of the yellow-necked mice from March to October. T. microti and T. evotomys were predominately found in the time from July to October. The high infection-rates of the bank vole with B. microti from January to March and July to August indicate a bimodal type of seasonal dynamic. Under natural conditions M. agrestis was the only host for B. microti. Nymphs of the tick Ixodes ricinus were found to be able to transmit B. microti to Syrian golden hamsters (Mesocricetus auratus) in the laboratory.

Animal Population Groups↗
PubMed1979

Functional and metabolic features of an isolated perfused guinea pig heart performing pressure-volume work.

Cardiac performance and some parameters of glycolytic and oxidative metabolism were analyzed in isolated perfused guinea pig hearts performing pressure-volume work. Perfusion medium was an oxygenated Krebs-Henseleit bicarbonate buffer (pH 7.4) which contained glucose and physiological concentrations of pyruvate and insulin. The pressure-flow relationship in the coronary vascular bed indicated autoregulation of coronary flow. Left ventricular function was influenced by aortic pressure (Pa) and venous filling pressure (Pv) in accordance with the Frank-Starling principle, i.e. stroke work increased as a function of Pa or Pv to a certain maximum and then decreased. Myocardial oxygen consumption (MVO2), on the other hand, was linearly correlated with Pa and Pv, respectively, over the entire pressure range. Efficiency of the left ventricle, therefore, increased to an optimum (16%) and decreased at higher pressures. Myocardial contents of glycogen, ATP and creatine phosphate were not markedly influenced by a change in Pa or Pv. L-Noradrenaline (0.08 micrometer, NA) stimulated stroke work and MVO2 at a all Pv tested; efficiencies reached physiologic values (21%) at high volume loads. The increased MVO2 was associated with an acceleration of pyruvate decarboxylation and lactate release up to 10- and 15-fold, respectively, at elevated but physiological NA concentrations (0.2 micrometer). Our results demonstrate that the isolated perfused working guinea pig heart compares favourably with the non-failing Starling heart-lung preparation and hearts in situ, as far as coronary function, left ventricular performance and oxidative metabolism are concerned.

Animals↗
PubMed1979

Structural relationship between the 100,000- and 17,000- molecular-weight T antigens of simian virus 40 (SV40) as deduced by comparison with the SV40-specific proteins coded by the nondefective adenovirus type 2-SV40 hybrid viruses.

The two-dimensional peptide maps of the methionine-containing tryptic peptides of the 100,000-molecular-weight (100K) and 17K T antigens of simian virus 40 (SV40) have been compared. The two proteins share nine methionine-containing tryptic peptides in common. The 17K T antigen has two peptides not found in the 100K T antigen, and the 100K T antigen has 14 unique peptides. The peptide maps of the 100 K and 17K T antigens were also compared with those of the SV40-specific proteins found in cells infected by the nondefective adenovirus type 2-SV40 hybrid viruses, which we have previously shown are encoded by defined sequences within the early region of SV40 (K. Mann, T. Hunter, G. Walter, and H.K. Linke, J. Virol. 24:151-169, 1977). This comparison shows that the 100K and 17K T antigens share common N-terminal sequences coded for between 0.65 and 0.59 map units on the SV40 genome. Furthermore, none of the sequences in the 17K T antigen arises from the region between 0.54 and 0.18 map units. We deduce that the sequences unique to the 17K T antigen originate between 0.59 and 0.54 map units. This type of structural relationship between the 100K and 17K T antigens fits well with the proposed model (L.V. Crawford, C.N. Cole, A. E. Smith, E. Paucha, P. Tegtmeyer, K. Rundell, and P. Berg, Proc. Natl. Acad. Sci. U.S.A. 75:117-121, 1978) for the expression of the early region of SV40.

Adenoviridae↗
PubMed1979

Communication and reasoning skills of deaf and hearing signers.

Six tests of intellectual performance were administered to 25 deaf and 21 hearing adult signers. The two groups were not significantly different on tests of Lip Reading and Reception of Signed English but the hearing subjects were superior on tests of non-verbal reasoning and perceptual speed. The hearing were greatly superior on a test of verbal reasoning.

Adult↗
PubMed1979

Separation of protoporphyrins and related compounds by reversed-phase liquid chromatography.

We describe the separation of protoporphyrin and related porphyrins by reversed-phase "high-performance" liquid chromatography, with fluorometric detection. We used the method to demonstrate that acid hydrolysis of the dimethyl ester of protoporphyrin IX is complete in 2 to 3 h and is followed by the acid-catalyzed conversion of protoporphyrin IX to a chemical species that chromatographic evidence indicates to be hematoporphyrin IX. In addition, the method was used to evaluate the purity of a commercial preparation of protoporphyrin IX and was also demonstrated to have the sensitivity and specificity needed for measuring the protoporphyrin IX content of whole-blood.

Chromatography, High Pressure Liquid↗
PubMed1978

Cell surface glycosyltransferases--do they exist?

The presence of glycosyltransferases on surfaces of mammalian cells has been reported by many investigators and a biological role for these enzymes in cell adhesion and cell recognition has been postulated. Critical analysis, however, showed 2 major complications regarding the assay for cell surface glycosyltransferases: 1) hydrolysis of the nucleotide sugar by cell surface enzymes and subsequent intracellular use of the free sugar and 2) loss of cell integrity if trypsinized or EDTA-treated cells were used in suspension assays. We have assayed intact, viable cells in monolayer for cell surface glycosyltransferases using conditions under which intracellular utilization of free sugars generated by hydrolysis of the nucleotide sugar was prevented. Our data demonstrate that the presence of galactosyltransferases on the surface of a variety of cells, including established (normal and virally transformed) as well as nonestablished cells, is unlikely. No evidence for the existence of cell surface fucosyl- and sialytransferases could be obtained, but our data do not exclude the possibility that low levels of these enzymes are present.

Cell Line↗
PubMed1978

A comparative study of hearing-impaired and normal-hearing young adults--verbal and nonverbal abilities.

This report describes the results of a study comparing three groups of hearing-impaired young adults with a group of normal-hearing young adults on various measures of perceptual and memory abilities. Twelve paper-and-pencil tests representing intellectual capacity, closure, association, nonverbal short-term memory, and verbal short-term memory were used as dependent variables. Results show that there was no difference between the four groups of subjects except for tests requiring some verbal facility.

Adult↗
PubMed1978

Fructose, a substrate for energy-yielding metabolism in the heart?

Effects of fructose and glucose on cardiac function and 14CO2 production from radioactive hexoses were studied in isolated working guinea pig hearts perfused at constant filling pressure via the left atrium. When hearts were perfused without exogenous substrates external work declined, indicating exhaustion of endogenous energy sources. It was possible to restore left ventricular function with concentrations of glucose in the physiological range; in order to achieve a similar restoration with fructose as the only exogenous substrate concentrations higher than 40mM were necessary. 14CO2 necessary. 14CO2 production from [U-14C]glucose was half-maximal at about 2mM glucose. On the other hand, 14CO2 production from [U-14C]fructose did not show saturation kinetics and, at concentrations around 2mM, was less than 5% of the rates observed with [U-14C]glucose. Moreover, fructose oxidation was suppressed in the presence of 5mM glucose. The data suggest that fructose cannot serve as a major substrate in the heart under in vivo conditions.

Animals↗
PubMed1977

Phosphohydrolases on the cell surface of BHK cells: loss during long term culture.

Low passage BHK 21/13 cells contain two cell surface enzymes, a nucleotide pyrophosphatase and a monophosphoester hydrolase, which together hydrolyze exogenous UDP-galactose to free galactose. During serial passage, BHK cells successively lose both enzymes. Concomitant with the loss of these enzymatic activities, changes in cell morphology, as well as in the serum requirement for the initiation of DNA synthesis, were observed. Clonal sublines of BHK cells were isolated, which differed qualitatively in their ability to hydrolyze UDP-galactose. Clonal BHK sublines, which exhibited both enzymatic activities on their cell surface, resembled low passage BHK cells in morphology and serum requirement for the initiation of DNA synthesis. Sublines not containing these enzymes resembled BHK cells of high passage cultures. The ability of intact BHK cells to hydrolyze exogenous nucleotide sugars may serve as an indicator for the progression of BHK cells from a normal to a more transformed state.

Adenosine↗