Search PubMed⌕ Search

Biomedical subjects

W Weis

Publications and source records attributed to W Weis.

At least 19 recordsLinked to original sources
PubMed2001

Regeneration of mature Norway spruce stands: early effects of selective cutting and clear cutting on seepage water quality and soil fertility.

The cutting of trees influences element turnover in the forest ecosystem. The reduction of plant uptake, as well as an increased mineralization and nitrification due to higher soil temperature and soil moisture, can lead to considerable losses of nutrients from the main rooting zone. This may result in a reduced soil fertility and a decrease in drinking water quality due to high nitrate concentrations in the seepage water. In Bavaria (Germany) selective cutting is preferred to clear cutting when initiating the regeneration of Norway spruce stands with European beech. This paper summarizes the early effects of both forest management practices on soil fertility and seepage water quality for three different sites. Shown are the concentrations of nitrogen and base cations in the seepage water as well as the water and ion fluxes during the first year after tree cut. Nutrient inputs decreased on thinned plots and even more at clear-cuts. Nitrate concentrations in the seepage water are hardly affected by moderate thinning; however, on clear-cuts, the nitrate concentration increases significantly, and base cations are lost from the upper mineral soil. This effect is less obvious at sites where a dense ground vegetation, which is able to take up excess nitrogen, exists.

Anions↗
PubMed1999

Chemosensitivity testing of oral cancer cells treated with a p185neu-specific agent.

The amplification and overexpression of the erbB-2 oncogene and its involvement in tumorigenesis makes this receptor an appropriate target for specific agents directed towards tumor cells. The purpose of this study was to evaluate the in vitro effect of the bacterially produced recombinant immunotoxin scFv(FRP5)-ETA on the protein synthesis and adenosine triphosphate (ATP) reduction in oral squamous cell carcinoma (OSCC) cells. This agent recognizes the erbB-2 receptor and inhibits protein synthesis in receptor-overexpressing cells. OSCC cells were selected for this study, and amplification and expression levels of the erbB-2 receptor were determined. Cell suspensions were cultured for 6 d with various concentrations of scFv(FRP5)-ETA (1-1000 ng/ml). A431 and MDA-MB468 cell lines were used as controls. Chemosensibility of tumor cells was measured by [3H]leucine incorporation assay and by an ATP luminescence assay. In OSCC cells with amplification and overexpression of erbB-2 inhibition, up to 92% of protein synthesis and 90% of ATP reduction was observed when cells were exposed to 1,000 ng/ml immunotoxin. In OSCC cells showing a deletion of erbB-2 and in erbB-2-negative MDA-MB468 cells, protein synthesis was inhibited by 22% and 8%, respectively. These results indicate that the effectiveness of a recombinant immunotoxin targeting erbB-2 receptors in OSCC cells depends on the level of erbB-2 amplification and expression, that it is highly specific for tumor cells expressing these receptors, and that a dose-dependency can be observed.

ADP Ribose Transferases↗
PubMed1993

[The role of the neurosurgeon in histopathologic diagnosis].

Neurosurgical practice has proved that the establishment of a correct neurohistopathologic diagnosis is sometimes difficult. Inconsistency of diagnoses resulting from unbiased examinations of several neuropathologists is not uncommon. The authors-neurosurgeons-have performed 300 fast neurohistopathologic examinations by means of smear technique. Correct diagnosis was stated in more than 90% of cases. Bioptic examination may represent a contribution in cases where postoperative irradiation is indicated, namely under diagnostically controversial circumstances. The authors re-evaluate the possibilities of utilization of smear technique for the purpose of histopathologic diagnostics performed directly by neurosurgeons. (Tab. 7, Ref. 5.).

Biopsy↗
PubMed1991

Platelet activating factor as a proinflammatory mediator in acetic-induced colitis in the rat.

Platelet activating factor (PAF) induces neutrophilia and produces a variety of gastrointestinal lesions. The role of PAF as a proinflammatory mediator was examined by measuring the production of PAF and the efficacy of the PAF antagonists WEB 2086 and Ro 24-0238 in acetic acid (HOAc)-induced colitis. PAF levels within the colonic mucosa, as measured by radioimmunoassay, increased from 259 +/- 119 ng/mg in control tissue, to 616 +/- 266 ng/mg in HOAc inflamed tissue. The accumulation of neutrophils within the mucosa was decreased by 53 +/- 10% by pretreatment with 3 mg/kg WEB 2086, and by 43 +/- 11% by 3 mg/kg Ro 24-0238. PAF-induced neutrophilia had no effect on the severity of HOAc-induced colitis, therefore, PAF my be involved in sustaining the chronic inflammation of colitis.

Acetates↗
PubMed1988

Structure of the influenza virus haemagglutinin complexed with its receptor, sialic acid.

The three-dimensional structures of influenza virus haemagglutinins complexed with cell receptor analogues show sialic acids bound to a pocket of conserved amino acids surrounded by antibody-binding sites. Sialic acid fills the conserved pocket, demonstrating that it is the influenza virus receptor. The proximity of the antibody-binding sites suggests that antibodies neutralize virus infectivity by preventing virus-to-cell binding. The structures suggest approaches to the design of anti-viral drugs that could block attachment of viruses to cells.

Antibodies↗
PubMed1988

Conformational aspects of the acid-induced fusion mechanism of influenza virus hemagglutinin. Circular dichroism and fluorescence studies.

Circular dichroism and tryptophan fluorescence spectroscopy have been used to investigate the structures of the influenza virus membrane glycoprotein hemagglutinin, acid-treated hemagglutinin, and fragments of hemagglutinin derived by proteolysis. The conformational change in hemagglutinin which occurs at the pH of membrane fusion (pH 5-6) was associated with a significant change of the environment of tyrosine residues, a change in the environment of tryptophan residues, but no changes in secondary structure. Tryptic digestion of the hemagglutinin in its low pH conformation which releases one of the subunit polypeptides (HA1) caused minimal changes in tyrosine and tryptophan environments but a small secondary structural change in HA1. The secondary structure of the remainder of the molecule (HA2) was very similar to that predicted from the known x-ray crystallographic structure of the native molecule. However, fluorescence spectroscopy indicated a tertiary change in structure in the coiled coil of alpha-helices which form the fibrous central stem of the molecule. These results are consistent with a conformational change required for membrane fusion which involves a decrease of HA1/HA1, HA1/HA2 interactions and changes in tertiary structure not accompanied by changes in secondary structure.

Circular Dichroism↗
PubMed1988

Studies on the structure of the influenza virus haemagglutinin at the pH of membrane fusion.

At the pH required to trigger the membrane fusion activity of the influenza virus haemagglutinin (HA) the soluble ectodomain of the molecule, BHA, which is released from virus by bromelain digestion, aggregates into rosettes. Analyses of soluble proteolytic fragments derived from the rosettes indicated that aggregation is mediated by association of the conserved hydrophobic amino-terminal region of BHA2, the smaller glycopolypeptide component of each BHA subunit. Further analyses of the structure of the soluble fragments and of HA in its low pH conformation by electron microscopy, spectroscopy and in crosslinking experiments showed that, although the membrane distal globular domains lose their trimer structure at the pH of fusion, the central fibrous stem of the molecule remains trimeric and assumes a more stable conformation. The increase in length of BHA2 at low pH observed microscopically appears to result from movement of the amino-terminal region to the membrane proximal end of the molecule and in virus incubated at low pH the amino terminus may insert into the virus membrane. The consequences of these possibilities for the mechanism of membrane fusion are discussed.

Bromelains↗
PubMed1984

[The effect of dietary lipids on microsomal electron transport proteins in the rat].

Feeding a fat-free diet for 3 weeks decreases the activity of ascorbate:ferricytochrome b5 oxidoreductase and increases NADH:monodehydroascorbate oxidoreductase in rat liver microsomes. Contrary to Vmax, the apparent Km for monodehydroascorbate of the first enzyme was not depressed. The activity of ascorbate:ferricytochrome b5 oxidoreductase is increased by incubation with microsomal lipid extract, thus showing that the loss of activity results from dietary-induced changes of microsomal fatty acid composition.

Animals↗
PubMed1983

Reduction of alloxan by microsomal electron transport proteins.

Alloxan behaves as a substrate for NADH:ferricytochrome b5 oxidoreductase (EC 1.6.2.2). The apparent Km for alloxan was 10 mM in liver microsomes and 20 mM with the enzyme prepared by lysosomal digestion. The apparent Km for NADH was the same with microsomes and the isolated enzyme (30 microM). The maximum turnover rate was calculated as 426 moles electrons/min X mole enzyme. Cytochrome b5 was shown to reduce alloxan nonenzymatically.

Alloxan↗
PubMed1983

Reinvestigation of the diabetogenic effect of dehydroascorbic acid.

To investigate the diabetogenic effect of pure dehydroascorbic acid, male Wister- and Sprague-Dawley rats received i.v. injections of the substance. No hyperglycemia and no decreased glucose tolerance were found. I.v. administration of the hydrolysis products of dehydroascorbic acid and of a solution containing monodehydroascorbate likewise did not increase blood glucose values. It is concluded that in previously performed experiments not dehydroascorbic acid itself but one or several impurities might have produced hyperglycemia in the rat. The electron transfer proteins tested (ascorbate:ferricytochrome b5 oxidoreductase, cytochrome b5, NADH:ferricytochrome b5 oxidoreductase, NADH:monodehydroascorbate oxidoreductase), which might participate in the reduction of dehydroascorbic acid, could not be induced in liver microsomes from Wistar rats by the injection of dehydroascorbic acid, its hydrolysis products, or monodehydroascorbate.

Animals↗
PubMed1980

[Influence of monodehydroascorbate on the acyl-CoA-desaturase system of rat liver microsomes (author's transl)].

The microsomal NADH- as well as the ascorbate-dependent fatty acid desaturation are diminished by monodehydroascorbate. This effect can be neutralized by borate. Borate forms an adduct with didehydroascorbate and thus prevents the formation of monodehydroascorbate. The ascorbate-dependent oleate formation is increased significantly by the same reaction (p less than 0.01). The NADH-dependent reaction is diminished by parallel reactions of the desaturase system and L-ascorbate: ferricytochrome b5 oxidoreductase at ferrocytochrome b5. In the case of the ascorbate-dependent reaction the diminished oleate formation is caused by the more positive oxidation state of cytochrome b5 in presence of monodehydroascorbate.

Animals↗
PubMed1978

Participation of L-ascorbate:ferricytochrome b5 oxidoreductase in ascorbate-dependent fatty acid desaturation of rat liver microsomes.

The microsomal enzyme ascorbate-cytochrome b5 reductase participates in the ascorbate-dependent fatty acid desaturation. Three pieces of evidence are given for this statement: 1) Comparison of the rate of ascorbate-dependent oleate formation with the rate of reduction of cytochrome b5 in microsomes and in the isolated detergent form shows that only the enzymatic reduction of cytochrome b5 is fast enough to support oleate formation; 2) added enriched ascorbate-cytochrome b5 reductase increases the rate of return of stearoyl-CoA oxidised cytochrome b5 back to the reduced state; 3) addition of enriched ascorbate-cytochrome b5 reductase increases the rate of ascorbate-dependent oleate formation in rat liver microsomes.

Animals↗