Search PubMed⌕ Search

Biomedical subjects

W Pfaller

Publications and source records attributed to W Pfaller.

At least 73 records · Page 4Linked to original sources
PubMed1982

[Comparative analysis of tetracycline, doxycycline and minocycline on chromosomal and plasmid tetracycline-resistant and -sensitive strains of Staphylococcus aureus using MIC, microcalorimetric effect and ultrastructural alterations].

A staphylococcus aureus strain of a patient with plasmidical tetracyclinresistance has first been cured from the plasmid and after that selected in nutritive broth by increasing the concentrations of tetracyclin. By this way we found three variants of the same strain: a tetracyclin-sensitive and two tetracyclin-resistant: an R-plasmid-mediated and the other as a result of mutation. These three variants have been tested against tetracyclin, minocyclin and doxycyclin on an agarmedium. Under influence of these three substances a microcalorimetrical investigation of the strains has taken place. We then tested the strains with the electronic microscope for alterations in the ultra-structure by the three substances. Following results have been obtained: 1. The sensitive strains were inhibited in the same extent by all of the three substances. Plasmidical resistant strains were only resistant against tetracyclin but not against minocyclin and even less against doxycyclin. 2. The microcalorimetrical tests confirmed the conclusions from the cultural test. 3. Alterations in ultra-structure were only found under tetracyclin-influence by strains in division. Comparing the three tetracyclines we did not find any significant difference in quality. 4. With all of the three investigation-methods we proved that R-plasmid-mediated tetracyclin-resistance of staphylococci is not effective for minocyclin and even less for doxycyclin.

Calorimetry↗
PubMed1980

Glycogen deposition in distal tubular cells during HgCl2 induced acute renal failure.

An unusual cytoplasmic accumulation of glycogen within the distal tubular epithelium of the kidney was produced by subcutaneouse administration of a single dose of HgCl2 (4 mg/kg body weight), used to induce acute renal failure. Since the plasma immune-reactive insulin was increased while plasma and urine glucose levels remained normal, it was concluded that activation of glycogen synthase might have lead to this effect. Furthermore, the accumulated glycogen was considered to contribute to the protection of distal tubular cells against HgCl2-induced injury, since oxidative energy metabolism was severely depressed after HgCl2 administration.

Acute Kidney Injury↗
PubMed1979

A concept for stereological investigation of rat kidney.

An attempt is presented to adapt sampling procedures for stereological investigation of rat kidney. The proposed experimental design considers the zonal construction, in particular the structural and osmotic features of this organ. Every zone is treated as an own entity inregard to sample collection. In order to uncover possibly existing preferential orientation of structures the application of two mutually perpendicular section planes is recommended. Furthermore a method is described to determine absolute volumes and surface of structural components.

Animals↗
PubMed1978

Preparation of resin embedded unicellular organisms without the use of fixatives and dehydration media.

A method is presented for processing single cells for conventional ultrathin sectioning without the use of fixatives and dehydration media. The cells were fixed by a physical method--spray freezing--which provides extremely high cooling rates, needs no pretreatment with cryoprotective agents and is therefore assumed to maintain the in vivo morphology of the cell. Hitherto cells prepared in this way have been investigated exclusively by freeze etching. To combine the advantages of this method with those of conventional ultrathin sectioning we have processed spray frozen cells with widely varying water contents (spermatozoa and lymphocytes) by freeze drying at 188 K and vacuum embedding. When compared to conventional chemical fixation the differences found in ultrastructural preservation of spermatozoa using this kind of preparation were confined to the arrangement of spermhead membranes and middlepiece structures. Lymphocyte structure was much closer to that known from chemical preparation, the only differences being a denser cytoplasm, denser mitochondrial matrices and thicker plasma membranes. These differences are probably due to the absence of eluating and dissolving effects present in conventional chemical preparations. The ultrastructural preservation of spray frozen cells is not different after freeze etching or after freeze-drying and vacuum embedding. This indicates clearly that drying and resin embedding does not produce artefacts and that structural preservation is therefore limited by the quality of cryofixation. Therefore this method is considered a contribution to the problem of preservation of the in vivo assembly of cellular substructure. Furthermore it seems to be a potential basis for preparation of soluble or diffusible substances or cellular compounds which would be influenced by fixatives and dehydrating agents.

Animals↗
PubMed1976

A critical reevaluation of the structure of the rat uriniferous tubule as revealed by scanning electron microscopy.

The fine structure of luminal surface of clearly identified portions of uriniferous tubules has been studied by scanning electron microscopy to elucidate some controversies concerning the topography of certain surface formations. The results show a characteristic pattern of the luminal surface in the region of Henle's loop, which was assumed by previous authors, to belong to the collecting tubule. Furthermore it is demonstrated that no cilia are present within the terminal portion of the collecting tubules.

Animals↗
PubMed1976

A comparison of the ultrastructure of spray-frozen and freeze-etched or freeze-dried bull and boar spermatozoa with that after chemical fixation.

The ultrastructure of bull and boar spermatozoa was investigated following different cryopreparation methods and chemical fixation. Spray-freezing was used for cryofixation in both freeze-etching and freeze-drying studies. Freeze-etching of boar spermatozoa revealed that the arrangement of the postnuclear striations differed from that in the bull. Freeze-drying gave excellent results for structural preservation, which were equal to those of chemical fixation. Some structural details not visible in chemically fixed cells were detected in freeze-dried and vacuum-embedded bull and boar spermatozoa, e.g. the arrangement of the lamellar nuclear contents, known from freeze-fractures, and a fine lamellar structure of the acrosomal contents. Cryofixation by spray-freezing combined with freeze-drying makes any contact of the cells with fixatives, buffer solutions and dehydration media unnecessary, and potentially provides all the advantages of ultrathin sectioning required for histochemical studies.

Acrosome↗
PubMed1976

Molecular specificity of tubular amino acid reabsorption.

The specificity of tubular reabsorption of L-arginine and L-methionine was investigated by continuous microperfusion of single proximal convolutions of the rat kidney. The following observations were made: 1) L-arginine reabsorption form the tubular lumen is saturable and can be inhibited by cycloleucine and some L-arginine derivatives with the following structure: -OOC -- CH (N+H3) -- (CH2)x -- N+H (R1) -- R2 The optimal value of x is 3 to 4. The methylene group adjacent to the nitrogen can be replaced by an oxygen atom. The radicals R1 and R2 have to permit ionization of the vicinal nitrogen. L-cysteine, L-homoserine, and diaminodicarboxylic acids do not inhibit L-arginine reabsorption. 2) L-methionine reabsorption is mainly a saturable process (Vmax = 2.5 x 10-(11) mol/cm/sec; Km = 6.1 mM). Passive diffusion does not play an important role (permeability coefficient = 2.45 x 10(-7) cm2/sec. 3) D-methionine also uses this saturable system for reabsorption. However, the affinity in this case is much smaller (Km = 23 mM). 4) L-phenylalanine, L-iso-leucine, L-ethionine, and cycloleucine seem to share this mechanism with L-methionine. In addition, the autoradiographic method was employed to determine on which side of the tubular cell competition of L-arginine and L-lysine for reabsorption occurs. Good evidence was obtained that the specific receptor for these two amino acids is located at the luminal membrane.

Animals↗