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Biomedical subjects

F Mayer

Publications and source records attributed to F Mayer.

At least 181 records · Page 10Linked to original sources
PubMed1987

Reeducative treatment of female genuine stress incontinence.

Three-months re-education treatment of genuine stress incontinence was given to 26 female outpatients: 22 patients completed the treatment programme and 4 interrupted it for various reasons. The aims of the treatment were both to correct compensatory habits that patients used to conceal or reduce leakage accidents and to give specific education and strengthening of pelvic floor muscles. All patients who completed the three-months treatment definitely improved and 7 were cured. Accordingly a marked reduction or absence of weekly incontinence episodes as well as a reduction of the daily frequency of micturition was observed. On vaginal palpation a clear-cut improvement of pubococcygeous muscle contractility was detectable. Urethral closure pressure profilometry showed significant improvement of functional urethral profile length at rest and of maximal urethral closure present both at rest and during maximal voluntary contraction of the pelvic floor muscles. Micturition cystourethrography, repeated in 15 patients at the end of the treatment, showed a clear-cut improvement of bladder neck suspension defects in all but 2 patients. Follow-up assessments showed that the clinical effects were long-lasting. Possible mechanisms of this re-educative technique are discussed.

Adult↗
PubMed1986

Avidin as a probe of the conformational changes induced in pyruvate carboxylase by acetyl-CoA and pyruvate.

Sheep liver pyruvate carboxylase was mixed with avidin at a molar ratio of 1:1 in the presence of various combinations of the components of the assay systems required for either the acetyl-CoA-dependent or the acetyl-CoA-independent activity and negatively stained samples were examined by electron microscopy. Significant numbers of chain-like polymers of enzyme-avidin complexes were evident only when acetyl-CoA or high levels of pyruvate were present in the media. Similar results were also obtained for chicken liver pyruvate carboxylase despite this enzyme's almost complete lack of acetyl-CoA-independent activity. Thus, although acetyl-CoA and high concentrations of pyruvate may induce pyruvate carboxylase to adopt a 'tight' tetrahedron-like conformation which can interact with avidin to form chains, this structural change alone does not result in an enzymic form that is maximally active. This suggests that the allosteric activation of pyruvate carboxylase by acetyl-CoA is attributable, at least in part to more subtle conformational changes; especially in the case of the chicken enzyme.

Acetyl Coenzyme A↗
PubMed1986

Immunocytochemical localization of component C of the methylreductase system in Methanococcus voltae and Methanobacterium thermoautotrophicum.

Antibodies were raised against homogeneous preparations of component C of the methylreductase system from Methanococcus voltae and Methanobacterium thermoautotrophicum. Cells of these organisms were fixed with paraformaldehyde and/or glutaraldehyde, sectioned, and labeled with antibodies and colloidal gold-labeled protein A. In M. voltae the gold particles were predominantly located in the vicinity of the cytoplasmic membrane. In rare cases a similar result was obtained also with M. thermoautotrophicum. However, in all but a few of the ultrathin sections of this bacterium, the label was randomly distributed in the cell interior. If one assumes a reliable fixation of all cell components, these results would suggest that the two distantly related methanogens studied have distinctive patterns for the localization of component C. The results with M. voltae are in agreement with recent findings that the methylreductase system is involved in the generation of a proton-motive force at the membrane.

Journal Article↗
PubMed1986

Macromolecular organization of F1-ATPase isolated from Clostridium thermoaceticum as revealed by electron microscopy.

Membrane vesicles and the F1-ATPase from Clostridium thermoaceticum were examined by electron microscopy. F1-ATPase particles projecting from the vesicles have a diameter of 10 to 12 nm. The F1-ATPase has an alpha 3 beta 3 gamma delta structure. The alpha and beta subunits are most likely arranged in an alternating sequence around a central protein mass consisting of the gamma and delta subunits.

Clostridium↗
PubMed1985

Immunoelectron microscopic localization of the restriction endonuclease EcoRI in Escherichia coli BS 5.

Purified restriction endonuclease EcoRI isolated from Escherichia coli BS 5 was used for the production of enzyme-specific IgG antibodies in rabbits. For enzyme localization experiments, paraformaldehyde-glutaraldehyde-fixed cells were embedded and polymerized by a low-temperature procedure using Lowicryl K4M. The immuno electron microscopic protein A-gold technique and an immuno-gold method revealed that 70% of the enzyme-specific labeling were located in the cell envelope whereas 30% were found in the cytoplasm. In metal-shadowed preparations, no indications for the presence of the enzyme could be found on the cell surface; however, on the surface of cell protoplasts enzyme specific labeling could be detected. The results indicate the presence of the major amount of EcoRI in the periplasmic space of the cell where it might be loosely bound or even freely diffusible.

DNA Restriction Enzymes↗
PubMed1985

National survey of undergraduate dermatologic medical education.

A survey of dermatology department or section chairmen was conducted to investigate the extent of undergraduate dermatologic training in US medical schools. The median number of required hours of dermatologic training was 14, which represents 0.24% of the overall medical school curriculum time. Required dermatologic training time varied greatly among schools, but most such training occurred in the fourth year of school. Students in 53% of the schools that responded to the survey were not involved in either clinical or basic dermatologic investigative activities.

Curriculum↗
PubMed1984

Immunocytochemical localization of carbon monoxide oxidase in Pseudomonas carboxydovorans. The enzyme is attached to the inner aspect of the cytoplasmic membrane.

The localization of carbon monoxide oxidase (CO oxidase), the key enzyme in CO metabolism of Pseudomonas carboxydovorans, was examined using modified immunoferritin and protein A-gold techniques. Cell extracts were incubated with specific immunoglobulin G antibodies raised against CO oxidase, followed by treatment with ferritin-conjugated goat-anti-rabbit immunoglobulin G antibodies (pre-embedding labeling). Electron microscopic examination of ultrathin sections showed cytoplasmic membranes and inside-out vesicles labeled at the inner aspect, whereas the outer sides of protoplasts and membrane vesicles remained completely unlabeled. The highly sensitive protein A-gold method has been modified to allow labeling of CO oxidase with good ultrastructural preservation of the bacterial cell. Glutaraldehyde-fixed cells of P. carboxydovorans were osmificated and embedded in glycol methacrylate. Etched ultrathin sections were treated with sodium metaperiodate and incubated with the specific antibodies against CO oxidase. These antibodies were then allowed to react with protein A-gold complexes (postembedding labeling). Exponentially grown cells showed 87% of CO oxidase associated with the cytoplasmic membrane and 13% of the enzyme in the cytoplasm. The results indicate that CO oxidase is attached in vivo to the inner aspect of the cytoplasmic membrane and suggest interaction of the enzyme with a membrane-bound electron acceptor. The ratio of enzyme associated with the cytoplasmic membrane decreased to 50% in the stationary growth phase.

Aldehyde Oxidoreductases↗
PubMed1984

Electron microscopic studies on liver 5-aminolaevulinate synthase.

The structure of chick embryo liver 5-aminolaevulinate synthase has been examined by electron microscopic studies using negative staining. From the different projections of the enzyme particles observed in electron micrographs, a model for the enzyme molecule has been proposed. In this model, an enzyme molecule consists of two curved and identical subunits associated in opposite polarities. From the dimensions of an enzyme molecule subunit measured from electron micrographs, the relative molecular mass of each subunit is estimated to be 70 000.

5-Aminolevulinate Synthetase↗
PubMed1984

[ANA-negative, anti-Ro-antibody positive subacute cutaneous lupus erythematosus].

A female patient presented with the typical clinical and histological features of disseminated lupus erythematosus (LE). Direct immunofluorescence, as well as antinuclear antibodies were negative, but antibodies directed against the cytoplasmic Ro-antigen were found. The Ro-antigen is regarded as highly specific for SLE and Sjögren's syndrome. Clinical features and diagnosis of this distinct LE subset ("ANA negative, anti-Ro-positive LE"), as well as the sensitivity and specificity of the substrate in ANA determinations are discussed.

Adult↗
PubMed1984

Pyruvate carboxylase from Aspergillus nidulans. Effects of regulatory modifiers on the structure of the enzyme.

A method is described for purification of pyruvate carboxylase from Aspergillus nidulans by affinity chromatography on monomeric avidin-Sepharose. The purified enzyme is homogeneous as judged by electrophoretic and immunochemical analysis. The sub-unit Mr determined by electrophoresis in the presence of sodium dodecyl sulphate is 133000 +/- 5000. Electron microscopic analysis of purified A. nidulans pyruvate carboxylase after negative staining with uranyl acetate reveals the presence of molecules showing rhomboid and triangular projections as well as a projection showing two intensity maxima. A cleft running along the longitudinal axis of the sub-unit is observed in the rhomboid and triangular projections. Interconversion between all three projections can be obtained in a tilt series. Significantly better preservation of molecular structure is obtained if A. nidulans pyruvate carboxylase is prepared for electron microscopy in the presence of acetyl-CoA, 2-oxoglutarate or as the enzyme-avidin complex. L-Aspartate has no significant effect when added alone but markedly decreases the enhanced preservation given by acetyl-CoA. No marked alterations in molecular dimensions are caused by any of these additions. L-Aspartate, but not 2-oxoglutarate, enhances the rate of inactivation observed on incubation of A. nidulans pyruvate carboxylase at 4 degrees C in the presence of 0.5 M KCl. Addition of L-aspartate in low concentrations enhances the effectiveness of inhibition by 2-oxoglutarate by causing a decrease in the value of [I]0.5 without affecting the Hill coefficient h or the extent of activity observed at saturating 2-oxoglutarate concentrations. Conversely addition of low concentrations of 2-oxoglutarate decreases the concentration of L-aspartate required to give 50% inhibition but also causes a fall in h and an absolute increase in the extent of activity observed in the presence of saturating L-aspartate concentrations. The data are consistent with the proposal that A. nidulans pyruvate carboxylase is a tetrameric molecule in which the four sub-units are located at the corners of a tetrahedron. Metabolites which regulate the activity of the enzyme do not cause major alterations in this molecular structure but may alter its stability.(ABSTRACT TRUNCATED AT 400 WORDS)

Aspartic Acid↗
PubMed1983

[Cellular and humoral immune phenomena in psoriatic arthritis].

The function of cellular immunity factors (lymphocyte transformation and phagocytosis by polymorphonuclear leucocytes [PMN] and monocytes in connection with the concentration of intracellular ATP) and humoral immunity factors (serum concentration of immunoglobulin and complement factors C'3 and C'4) was investigated in 16 controls, 21 patients with psoriatic arthritis and 19 with psoriasis vulgaris. The results were compared with the clinical and anamnestic data of the patients. PMN phagocytosis of zymosan opsonized with rabbit standard serum was decreased in psoriasis vulgaris in comparison with the controls. Also, monocyte phagocytosis of non-opsonized zymosan was decreased in psoriatic arthritis, as compared with psoriasis vulgaris. Furthermore, in PMNs intracellular ATP was elevated in psoriatic arthritis as compared with the controls, but decreased in comparison with patients with psoriasis vulgaris. The intracellular ATP in monocytes was decreased in psoriasis vulgaris as compared with the controls. Humoral immunological findings: serum IgG concentration was higher in psoriatic arthritis than in controls and in psoriasis vulgaris. Elevated C'3 and decreased C'4 serum concentrations in psoriatic arthritis indicate an activation of the complement system.

Adenosine Triphosphate↗
PubMed1983

An electron microscopic approach to the quaternary structure of mitochondrial F1-ATPase.

The three-dimensional structure of F1-ATPase from beef heart mitochondria was investigated by electron microscopic techniques. The presence of high concentrations of nucleotides is essential for preservation of the quaternary structure. When investigated under such conditions, monodisperse F1-ATPase could not be distinguished from the membrane-bound enzyme. At low resolution, the particle shape resembles an oblate ellipsoid of revolution with an axial ratio of about 2:1. From several lines of evidence (including field micrographs at higher magnifications, Markham rotational analysis, and tilting experiments), two conclusions may be drawn concerning the three-dimensional fine structure of F1-ATPase. 1. At the periphery of the molecule, six globular protein masses are orientated in a way similar to the chair conformation of cyclohexane. This array is interpreted to be made up of an alternating sequence of alpha and beta subunits. 2. Part of the central space is occupied by a seventh protein mass, protrusions of which are likely to be in contact with some of the outer subunits. A gamma subunit is supposed to be constituent part of this central protein mass. As a consequence, this model favours a stoichiometry of alpha 3 beta 3 gamma for the large subunits of beef heart F1-ATPase.

Animals↗
PubMed1982

Formyltetrahydrofolate synthase from Clostridium thermoaceticum. An electron microscopic study and specific interaction of the enzyme with ATP and ADP.

Formyltetrahydrofolate synthetase (EC 6.3.4.3) from Clostridium thermoaceticum is a 240 000-molecular-weight, tetrameric enzyme composed of identical subunits. When negatively stained with uranyl acetate or sodium phosphotungstate the enzyme appears as two distinct projections when viewed in the electron microscope. One of these, resembling the letter "H", exhibits four flexible arms, while the other, called a "twin", has a compact projection. The twin projection appears to represent the native enzyme in solution. It consists of two outstanding intensity maxima separated by a narrow bridge of dense stain, with each of these intensity maxima being divided into the two submaxima by a second bridge of stain running perpendicular to the first one. The outstanding intensity maxima represent dimers, whereas the submaxima represent a single subunit. The volume calculated from the electron microscopy projections for the dimer is 157 nm3, which corresponds to a Mr of 127 000 or 254 000 for the tetrameric enzyme. The H projections reflect enzyme particles artificially flattened and "opened" during the drying of the negatively stained enzyme. The four arms of the H each represent a subunit. The appearance of H projections is prevented by either using a deep-stain procedure, which offers a mechanical preservation of the native enzyme structure, or by the binding of ATP, ADP or adenosine 5'-[beta, gamma-methylene]triphosphate. These nucleotides, when binding to the enzyme, cause a conformational change. This was observed by ultraviolet and visible circular dichroism and absorption spectrometry with the native enzyme and an enzyme labeled with fluorescein mercuric acetate attached to a sulfhydryl group of each subunit.

Adenosine Diphosphate↗
PubMed1982

Purification of L-glutamate-dependent citrate lyase from Clostridium sphenoides and electron microscopic analysis of citrate lyase isolated from Rhodopseudomonas gelatinosa, Streptococcus diacetilactis and C. sphenoides.

Citrate lyase from Clostridium sphenoides was purified 72-fold with a yield of 11%. In contrast to citrate lyase from other sources the activity of this enzyme was strictly dependent on the presence of L-glutamate. The purified enzyme was only stable in the presence of 150 mM L-glutamate or 7 mM L-glutamate plus glycerol, sucrose or bovine serum albumin. Changes of the L-glutamate pool and of enzyme activity in growing cells of C. sphenoides indicated that citrate lyase activity in this organism was regulated by the intracellular L-glutamate concentration. Citrate lyase isolated from C. sphenoides, Rhodopseudomonas gelatinosa and Streptococcus diacetilactis was investigated by electron microscopy using the negative staining technique. Three different projections of enzyme molecules were observed: 'star' form, 'ring' form and 'triangle' form. In samples from R. gelatinosa and S. diacetilactis, star and ring forms occurred in a ratio of about 1:9. Using the enzyme from S. diacetilactis it was demonstrated that this ratio could be altered in favour of the star form by the addition of citrate or tricarballylate. The triangle form was observed in less than 1% of all evaluated molecules and may represent a transition form. In lyase samples from C. sphenoides there existed a correlation between enzyme activity and the proportion of stars and rings at varying concentrations of L-glutamate.

Bacteria↗