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Biomedical subjects

H Voelz

Publications and source records attributed to H Voelz.

At least 19 recordsLinked to original sources
PubMed1985

Bacterial endosymbionts of Acanthamoeba sp.

Gimenez staining of presumably axenic Acanthamoeba sp., strain HN-3, showed rod-shaped cytoplasmic inclusions. Electron microscopy of thin sections of the amebae showed these to be bacilli which measured 1.3 to 3.3 microns by 0.22 to 0.33 micron. Their cell envelopes were those typical of gram-negative bacteria, surrounded by an electron-translucent area that stains with ruthenium red, suggesting the presence of a capsule. The bacilli grew and reproduced in the cytoplasm of both trophozoites and cysts of Acanthamoeba sp. There was no evidence of a surrounding phagosomal or phagolysosomal membrane. They were retained by the ameba both during encystment and excystment. All attempts to isolate the endosymbionts in embryonated eggs and/or standard bacteriological media failed; and they persisted within the amebae for 1 to 6 mo despite temperature shocking or constant treatment of cultures with penicillin, streptomycin, chloramphenicol, tetracycline, erythromycin, polymyxin B, ampicillin, isoniazid, rifampicin, or gentamycin at concentrations of 10(-5) to 10(-3) M.

Amoeba↗
PubMed1984

Phospholipase activity in human tumors: localization by cytochemical staining.

Phospholipase activity was localized for the first time by cytochemical staining at the plasma membrane of malignant cells in gastric adenocarcinomas by electron microscopy. This activity was not found in benign cells of the same tumor, e.g., in components of the connective tissue underlying the glandular epithelium, or in cells beyond the margin of the same tumor. Neither benign nor malignant cells of colorectal tumors, nor those in malignant melanoma, had any phospholipase activity that could be demonstrated by the method.

Adenocarcinoma↗
PubMed1978

Site of ATPase activity in Myxococcus xanthus: lipid requirement for enzyme activity. Dedicated to Professor Dr. W. Schwartz on his 80th birthday.

Treatment of cells with lysophosphatidylcholine, lysozyme, and phospholipase D removed most of their phospholipids and reduced ATPase activity to near zero. Addition of a microdispersion of phospholipids restored enzyme activity to various degrees. Phosphatidylcholine was most effective in reconstitution experiments, less effective were phosphatidylethanolamine and phosphatidylserine. Lipid analyses of cell fractions were possible through separation of cell wall and cell membrane in a sucrose gradient after differentiated treatment of glutaraldehyde fixed cells with lysophosphatidylcholine, lysozyme, and pronase. Phosphatidylcholine was almost exclusively a component of the cell membrane, whereas phosphatidylethanolamine was that of the wall. It is concluded that lipids are necessary for in vivo function of a Mg-dependent ATPase, and that membrane-associated phosphatidylcholine may serve as a matrix for the enzyme. Lipid extracts made from cells or cell fractions contained plasmologens, not previously reported to occur in Gram-negative, aerobic bacteria.

Adenosine Triphosphatases↗
PubMed1972

Reversion of ribosomal helix formation in Escherichia coli.

After transfer into fresh medium, Escherichia coli cells containing ribosomal helices resume growth without a lag period. The helices disappear within 15 min after transfer, the number of 70S ribosomes decreases, and a steady-state ribosomal profile appears within one cell generation time. Subunits isolated from the helices support in vitro protein synthesis, but efficiency is optimal only when supplemented with an undetermined factor that is contained in the S-100 fraction of log-phase cells. The data suggest a possible role of helices as ribosomal reserve units.

Bacterial Proteins↗
PubMed1971

Ribosomal helices: formation in Escherichia coli during acidic growth.

Ribosomal helices are formed in 100% of Escherichia coli cells during extended growth in a medium of low buffering capacity. During this time, the pH of the medium gradually decreases from 7.0 to about 5.0. Transfer of cells into preconditioned or acidified medium does not result in helix formation unless acidification is gradual and during active growth. Concomitant with helix formation is a decrease of all major biosynthetic activities and cessation of cell motility. The larger polyribosomes become converted into an inactive helical form and sediment in sucrose gradients with the wall-membrane complex.

Buffers↗
PubMed1969

Induction of helical arrays of ribosomes by vinblastine sulfate in Escherichia coli.

Physiological concentrations of vinblastine sulfate elicited ribosomal helices in large numbers in growing cultures of the osmotically sensitive mutant sud 24 and, after treatment with ethylenediaminetetraacetate, also in the K-12 strain. The helices were usually seen at the division plane and were often connected to the membrane. This method of induction of ribosomal helices offers a unique system for studying in vivo structure and function of the translational apparatus in relation to other cell components.

Cell Division↗
PubMed1969

Structural changes in Stigmatella aurantiaca during myxospore induction.

Suspension cultures of Stigmatella aurantiaca (Chondromyces aurantiacus) were induced to form myxospores by addition of glycerol to the growing culture. The cells were fixed at various stages during conversion, thin sections were prepared, and changes in fine structure were studied. Vegetative cells are quite similar in their ultrastructure to Myxococcus xanthus. During transformation into myxospores, three important cytological changes were observed. Granules of storage material, probably polysaccharide and polyphosphate, accumulated; a 200 to 300-mum thick capsule was laid down, and the outer triple layer of the cell wall became locally folded. These cell wall folds were often densely packed and lay in pockets formed by the cytoplasmic membrane. We have suggested the possibility that the cell may store in these folds wall material which has become superfluous by the decrease in surface area during conversion.

Bacteria↗
PubMed1969

Fine structure of fruiting bodies of Stigmatella aurantiaca (Myxobacterales).

The fruiting body of Stigmatella aurantiaca consists of a thick stalk supporting a number of individual cysts. The stalk is made of discontinuous tubules, of dimensions known for vegetative cells, which are oriented parallel to the longitudinal axis of the stalk. The red-brown cysts contain numerous, randomly oriented myxospores which are surrounded by thick, fibrous capsules. Their cell walls are wavy or ruffled and exhibit fewer budlike infoldings than reported for myxospores induced in liquid. We suggest that the extended time period available for metabolic and regulatory adjustments by the cell during morphogenesis within cysts accounts for the presence of considerably fewer deep cell wall infoldings than in glycerol-induced myxospores.

Bacteria↗
PubMed1968

Cytochemistry of phosphatases in Myxococcus xanthus.

An Mg(2+)-dependent and a K(+)-stimulated adenosine triphosphatase were localized by cytochemistry at or near both surfaces of the cytoplasmic membrane of Myxococcus xanthus. An alkaline and an acid phosphatase resided at the external surface of the membrane or in the periplasm. All enzymes could be extracted from partially fixed cells with Mg(2+)-deficient buffers. Suboptimal external phosphate elicited dissociation of adenosine triphosphatase from the membrane but not that of the unspecific phosphatases. The dissociated enzymes migrated into the cytoplasm where they were associated mainly with cytoplasmic aggregates.

Acid Phosphatase↗