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F Mayer

Publications and source records attributed to F Mayer.

At least 109 records · Page 6Linked to original sources
PubMed1996

Thermobrachium celere gen. nov., sp. nov., a rapidly growing thermophilic, alkalitolerant, and proteolytic obligate anaerobe.

More than 40 isolates of a novel, ubiquitous, proteolytic, moderately alkaliphilic, thermophilic obligate anaerobe were obtained from geothermally and anthropogenically heated environments and mesobiotic environments located on three continents. Whole-cell protein sodium dodecyl sulfate gel electrophoresis revealed that most of these organisms are very similar. Eight of the isolates were characterized in detail; this analysis included 16S ribosomal DNA sequence analysis. The cells of those organisms are (depending on the isolate) 0.5 to 0.8 micron in diameter and 1.5 to 13 microns long, exhibit tumbling motility, and have a positive Gram stain reaction. The temperature range for growth is 43 degrees to 75 degrees C (optimum temperature, 66 degrees C), and the pH range for growth is 5.4 to 9.5 (optimum pH, 8.2); the shortest doubling time is around 10 min. Yeast extract is required for growth, and (depending on the strain) glucose, sucrose, fructose, galactose, and ribose are utilized. The fermentation products from glucose in the presence of yeast extract are CO2, H2, acetate, formate, and ethanol. The G + C content is 30 to 31 mol%. On the basis of these properties, which differentiate these strains from all alkalitolerant thermophiles described previously, and the results of a comparison of the 16S ribosomal DNA sequences of these organisms with previously described sequences, we propose that our isolates be placed in a single species of the new genus Thermobrachium; strain JW/YL-NZ35 is the type strain of the the type species, Thermobrachium celere.

Bacteria, Anaerobic↗
PubMed1996

Influence of Escherichia coli on motility parameters of human spermatozoa in vitro.

The influence of E. coli on human sperm motility was studied in vitro. Semen samples were prepared by a swim-up technique and adjusted to 22 x 10(6) spermatozoa/ml. Samples were then inoculated with different concentrations of a uropathogenic strain of E. coli, serotype 06, with initial sperm/bacteria ratios varying between 10:1 and 10000:1. Motion parameters were analysed by computer-aided motility analysis directly, and 2, 4 and 6 h after inoculation. In a second series of experiments, bacterial replication was inhibited by addition of chloramphenicol. In a third series, the effect of E. coli culture filtrates on sperm motility was investigated. The direct inhibitory effect of E. coli on progressive motility of spermatozoa was found to depend upon the bacterial concentration. A distinct inhibitory effect was observed only at a sperm/bacteria ratio of approximately 1, achieved by growth of E. coli during the experiments. For modality of motion, no distinct changes were observed. When growth of bacteria was prevented by chloramphenicol, no inhibitory effect on sperm motility was detected. Sperm motility was not inhibited by E. coli culture filtrates. Analysis by electron microscopy revealed multiple adhesions of E. coli to spermatozoa, causing variable ultrastructural damage as probable morphological correlates of immobilization.

Bacterial Adhesion↗
PubMed1996

[Feasability of the dose adjustment of continuous infusion administration over 120 hours of 5-fluorouracil associated with cisplatin].

Therapeutic monitoring of 120 hours continuous 5-fluorouracil associated with cisplatin. For 31 patients treated by continuous 5-fluorouracil with cisplatin, a therapeutic monitoring of 5-fluorouracil is performed, based on the 48 first hours area under the curve (AUC) and the total AUC. The 5-fluorouracile taylorization allows to reduce some toxicity's while preserving an efficiency (objective responses 42%). Many patients are considered with potentially low 5-fluorouracile clearance. Dose reductions of 5-fluorouracile are frequent, reach 50% during the third cure and allow the achievement of targeted AUC. The role of cisplatin in this necessary reduction of dose is unknown.

Adult↗
PubMed1995

Membrane insertion of the bacterial signal transduction protein ToxR and requirements of transcription activation studied by modular replacement of different protein substructures.

The Vibrio cholerae protein ToxR is an integral membrane protein that acts as a transcription activator in response to environmental signals; it controls expression of toxin genes ctxA and ctxB, along with a variety of other genes related to pathogenicity. Here it is shown that: (i) ToxR has a modular architecture and that activation of transcription starting at the ctx promoter depends strictly on dimerization of the periplasmic ToxR domain; (ii) the transmembrane (TM) region of ToxR is sufficient as a topogenic signal but not for stable membrane anchoring of the protein; (iii) the TM region has no special function in signal transduction and (iv) a proline residue located within the TM region minimizes background transcription activation, most plausibly by reducing TM-TM interaction. Possible applications of ToxR as a technical tool for analysing protein-protein interactions between pairs of arbitrary TM domains are discussed.

ATP-Binding Cassette Transporters↗
PubMed1995

The F0 complex of the Escherichia coli ATP synthase. Investigation by electron spectroscopic imaging and immunoelectron microscopy.

Cholate-solubilized F0 complexes of the ATP synthase (F0F1) from Escherichia coli were studied by application of conventional transmission electron microscopy and electron spectroscopic imaging (ESI) of negatively stained samples. Using the ESI mode, the structural organization of the F0 complex (diameter of 7.5 +/- 0.5 nm) could be observed in more detail and defined projections could be distinguished. Projection A appears as a deltoid-like structure with bilateral symmetry. Projection B has an overall trapezoidal shape with some similarity in shape to the letter W. Applying the ESI mode to the ac complex dissolved in cholate-containing buffer, an elongated structure consisting of two intensity maxima could be observed. Simulations with models of the F0 and the ac complex revealed that the projections observed can be obtained by tilting and rotating a model in which subunit a and the two copies of subunit b are located outside the subunit c oligomer. This view of structural organization was supported by results obtained with F0 complexes decorated with monoclonal antibodies against subunits a, b or c.

Antibodies, Monoclonal↗
PubMed1995

Analysis of a 24-kilodalton protein associated with the polyhydroxyalkanoic acid granules in Alcaligenes eutrophus.

A 5.0-kbp genomic EcoRI restriction fragment which complemented a third subclass of polyhydroxyalkanoic acid (PHA)-leaky mutants of A. eutrophus that accumulated PHA at a lower rate than the wild type was cloned from Alcaligenes eutrophus H16. A 687-bp phaPAe gene on this fragment encoded a 24-kDa protein (M(r) = 23,963), which was referred to as the GA24 protein. The GA24 protein was solubilized from the granules and purified to electrophoretic homogeneity, and antibodies against the GA24 protein were obtained. The GA24 protein bound to the surface of PHA granules, as revealed by immunoelectron microscopy of whole cells and of artificial PHA granules. The GA24 protein contributed approximately 5% (wt/wt) of the total cellular protein, and it was the predominant protein present in the granules. It was synthesized only in cells accumulating PHA and only in amounts that could be bound to the granules; no soluble GA24 protein was detected. Tn5::mob-induced phaPAe mutants which were unable to synthesize intact GA24 protein formed only one large PHA granule per cell. The amino acid sequence of the GA24 protein revealed two closely related stretches consisting exclusively of nonhydrophilic amino acids at the C-terminal region, which are presumably involved in the binding of GA24 to the granules, as was recently proposed for a similar protein in Rhodococcus ruber. The GA24 protein seems to be a representative of phasins, which are a new class of protein that form a layer at the surface of PHA granules, like oleosins, which form a layer at the surface of triacylglycerol inclusions in oilseed plants.

Alcaligenes↗
PubMed1995

Identification of the region of a 14-kilodalton protein of Rhodococcus ruber that is responsible for the binding of this phasin to polyhydroxyalkanoic acid granules.

The function of the polyhydroxyalkanoic acid (PHA) granule-associated GA14 protein of Rhodococcus ruber was investigated in Escherichia coli XL1-Blue, which coexpressed this protein with the polyhydroxybutyric acid (PHB) biosynthesis operon of Alcaligenes eutrophus. The GA14 protein had no influence on the biosynthesis rate of PHB in E. coli XL1-Blue(pSKCO7), but this recombinant E. coli strain formed smaller PHB granules than were formed by an E. coli strain that expressed only the PHB operon. Immunoelectron microscopy with GA14-specific antibodies demonstrated the binding of GA14 protein to these mini granules. In a previous study, two hydrophobic domains close to the C terminus of the GA14 protein were analyzed, and a working hypothesis that suggested an anchoring of the GA14 protein in the phospholipid monolayer surrounding the PHA granule core by these hydrophobic domains was developed (U. Pieper-Fürst, M. H. Madkour, F. Mayer, and A. Steinbüchel, J. Bacteriol. 176:4328-4337, 1994). This hypothesis was confirmed by the construction of C-terminally truncated variants of the GA14 protein lacking the second or both hydrophobic domains and by the demonstration of their inability to bind to PHB granules. Further confirmation of the hypothesis was obtained by the construction of a fusion protein composed of the acetaldehyde dehydrogenase II of A. eutrophus and the C terminus of the GA14 protein containing both hydrophobic domains and by its affinity to native and artificial PHB granules.

Acyltransferases↗
PubMed1995

Considerations on the structure and biochemistry of bacterial polyhydroxyalkanoic acid inclusions.

Some mathematical calculations were done that provided information about the structure and biochemistry of polyhydroxyalkanoic acid (PHA) granules and about the amounts of the different constituents that contribute to the PHA granules. The data obtained from these calculations are compared with data from the literature, which show that PHA granules consist not only of the polyester but also of phospholipids and proteins. The latter are referred to as granule-associated proteins, and they are always located at the surface of the PHA granules. A concept is proposed that distinguishes four classes of structurally and functionally different granule-associated proteins: (i) class I comprises the PHA synthases, which catalyze the formation of ester linkages between the constituents; (ii) class II comprises the PHA depolymerases, which are responsible for the intracellular degradation of PHA, (iii) class III comprises a new type of protein, which is referred to as phasins and which has most probably a function analogous to that of oleosins in oilseed plants, and (iv) class IV comprises all other proteins, which have been found to be associated with the granules but do not belong to classes I-III. Particular emphasis is placed on the phasins, which constitute a significant fraction of the total cellular protein. Phasins are assumed to form a close protein layer at the surface of the granules, providing the interface between the hydrophilic cytoplasm and the much more hydrophobic core of the PHA inclusion.

Acyltransferases↗
PubMed1995

Structural and immunological studies on the soluble formate dehydrogenase from Alcaligenes eutrophus.

During growth with formate as the sole energy source the autotrophic bacterium Alcaligenes eutrophus synthesizes a cytoplasmic formate dehydrogenase. The enzyme is a molybdo-iron-sulfur-flavo protein and the major NADH-producing system under these growth conditions, although it was estimated to constitute only 0.65% of the soluble cell protein. An electron microscopic analysis of the purified enzyme revealed that the particle is made up of four nonidentical submasses, corroborating previous structural data. The NH2-terminal amino acid sequences of the enzyme subunits exhibited significant similarities to those of only one other heteromeric formate dehydrogenase, the enzyme from the methane-utilizing bacterium Methylosinus trichosporium. Metal analyses yielded 21.5 g-atom iron, 2.18 g-atom nickel, 0.76 g-atom molybdenum, and 0.59 g-atom zinc per mol of enzyme. Initial electron paramagnetic resonance spectroscopic studies showed at least three distinct signals which appeared upon reduction of the enzyme with NADH or formate. The corresponding spin systems could be attributed to iron-sulfur centers of the enzyme. Comparative immunostaining and activity-staining experiments using cell extracts from various bacteria established immunological similarities between the soluble formate dehydrogenase of A. eutrophus and the soluble enzymes from all tested facultative autotrophs as well as from M. trichosporium.

Alcaligenes↗
PubMed1995

System identification of the low-dose kinetics of p-aminohippuric acid.

The renal clearance of p-aminohippuric acid, due to tubular secretion in addition to glomerular filtration, can only be determined by kinetic experiments. Maximal information can be gained from observed temporal marker concentration profiles by fitting dynamic mathematical models of the processes involved, such as absorption, distribution, and elimination, to the kinetic data. Thereby the values of the system constants, such as fractional elimination or fractional distribution rates, and their accuracy measures are determined by methods which are based firstly on measured time-dependent data elicited in an individual test object by perturbing inputs and secondly, on mathematical formulations of prior knowledge of the underlying physiological system. Such methods of model adaptation are called system identification. In this context a computer-based method of system identification and error estimation for the system constants of two-compartment models matched a dynamic concentration profiles of p-aminohippuric acid is presented. The method is used of single-injection experiments to demonstrate that such a technique is able to correctly estimate the clearance of p-aminohippuric acid if sufficiently long experimental protocols are chosen, and to ascertain the sufficient length of a protocol for an individual subject. The renal clearance of p-aminohippuric acid is known to exhibit concentration-dependence generally, but to achieve its maximal value when low doses are applied. The present study deals with the low-dose kinetics of p-aminohippuric acid.

Adult↗
PubMed1995

Spongiotic pericytoma: a benign neoplasm deriving from the perisinusoidal (Ito) cells in rat liver.

Spongiosis hepatis has been known for some time to develop frequently in livers of rats and fish treated with hepatocarcinogens and was considered to derive from the perisinusoidal (Ito) cells (PSC). Using rat liver treated with N-nitrosomorpholine at different dose levels, we studied the cellular composition and origin as well as the proliferation kinetics of spongiosis hepatis by immunohistochemical demonstration of desmin, vimentin, and alpha-smooth-muscle actin, and by autoradiographic determination of [3H]-thymidine incorporation, respectively. The vast majority of the cells forming spongiosis hepatis were positive for desmin and vimentin but negative for alpha-smooth-muscle actin, confirming the cellular origin of spongiosis hepatis from PSC. In addition, immunohistochemical demonstration of desmin and vimentin revealed that spongiosis hepatis is an integral part of larger lesions consisting of focal PSC aggregates. These aggregates show a significantly increased incorporation of [3H]-thymidine compared with PSC in the extrafocal tissue and in the liver tissue of untreated control animals. In stop experiments, this increased labeling index was maintained many months after withdrawal of the carcinogen, in line with the earlier observation of a progressive behavior of spongiosis hepatis. We conclude that PSC may give rise to proliferative lesions appearing as PSC aggregates associated with more or less pronounced spongiosis hepatis. The persistence, the proliferative activity, and the slow expansive growth of these lesions suggest a benign neoplastic behavior. We therefore propose to classify these lesions as spongiotic pericytoma. Malignant tumors possibly originating from spongiotic pericytoma should consequently by classified as perisinusoidal (Ito) cell sarcomas.

Animals↗
PubMed1994

The molecular structure of the Na(+)-translocating F1F0-ATPase of Acetobacterium woodii, as revealed by electron microscopy, resembles that of H(+)-translocating ATPases.

The Na(+)-translocating F1F0-ATPase of Acetobacterium woodii was examined by electron microscopy. After reconstitution into proteoliposomes, knobs typical for the F1 domain were visible on the outside of the membrane. The F1-part of the isolated enzyme showed a hexagonal symmetry suggesting an alpha 3 beta 3 structure, and the F1F0 complex had molecular dimensions very similar to those of H(+)-translocating ATPases of E. coli, chloroplasts, and mitochondria.

Adenosine Triphosphatases↗
PubMed1994

Purification and characterization of the poly(hydroxyalkanoic acid) synthase from Chromatium vinosum and localization of the enzyme at the surface of poly(hydroxyalkanoic acid) granules.

A recombinant strain of Escherichia coli, which overexpressed phaC and phaE from Chromatium vinosum, was used to isolate poly(3-hydroxyalkanoic acid) synthase. The isolation was performed by a two-step procedure including chromatography on DEAE-Sephacel and Procion Blue H-ERD. The poly(3-hydroxyalkanoic acid) synthase consisted of two different kinds of subunit (PhaC, M(r) 39,500 and PhaE, M(r) 40.500). PhaC was separated from the poly(3-hydroxyalkanoic acid) synthase complex by chromatography on phenyl-Sepharose: PhaE was enriched by solubilization of protein inclusion bodies. The stoichiometry of PhaC and PhaE in the enzyme complex was not determined. The poly(3-hydroxyalkanoic acid) synthase (PhaEC) exhibited a native relative molecular mass of M(r) 400,000 and most probably consists of ten subunits. The Km value of the enzyme for D(-)-3-hydroxybutyryl-CoA was 0.063 mM. The enzyme synthesized poly(3-hydroxybutyric acid) in vitro from D(-)-3-hydroxybutyryl-CoA or, together with propionyl-CoA transferase in a coupled enzyme reaction, synthesized the same product from acetyl-CoA plus D(-)-3-hydroxybutyric acid. Antibodies were raised against both subunits of the poly(3-hydroxyalkanoic acid) synthase. By immunoelectron microscopy, the poly(3-hydroxyalkanoic acid) synthase was localized within the cytoplasm in cells of C. vinosum grown under non-storage conditions. In cells grown under poly(3-hydroxybutyric acid) storage conditions, the enzyme was observed to be located at the surface of the poly(3-hydroxybutyric acid) granules. Immunoblots with anti-PhaC, anti-PhaE IgG and crude extract proteins indicated that poly(3-hydroxyalkanoic acid) synthases with partial sequence similarities are widespread among purple sulphur bacteria.

Acyltransferases↗
PubMed1994

Stability and activity of hydrogenases of Methanobacterium thermoautotrophicum and Alcaligenes eutrophus in reversed micellar systems.

In water-in-oil microemulsion the membrane-associated F420-hydrogenase of Methanobacterium thermoautotrophicum (strain Marburg) and the membrane-bound hydrogenase of Alcaligenes eutrophus H 16 (MBH) showed prolonged activity at elevated temperatures (measured as hydrogen production) as compared to aqueous buffer solution. The temperature optimum of the reactions was about 15 degrees C higher than in aqueous buffer solution. Activity of the almost completely inactivated F420-hydrogenase could be partially recovered by transfer into microemulsion.

Alcaligenes↗
PubMed1994

Normal values of isokinetic maximum strength, the strength/velocity curve, and the angle at peak torque of all degrees of freedom in the shoulder.

Many acute and chronic complaints in the shoulder joint are due to a reduced active stabilization capacity. Procedures to measure isokinetic strength are used to objectify the muscle deficits and imbalances of various muscle groups. In this study, standard values and reference ranges were determined for peak torque (PT), strength/velocity curve, and range of motion (ROM) at peak torque in the shoulder in 19 untrained women and 32 men. Differentiation was made by the individual degrees of freedom of the shoulder joint and the various types of work (concentric, isometric, eccentric). Moreover, the influence of height, body weight, and body mass index on isokinetic maximum strength development was investigated. It was found that it is necessary to distinguish between the various movements and types of work in development of peak torque. A decrease in maximum strength is observed in the sequence extension, adduction/flexion, abduction/internal rotation, external rotation. The maximum strength of men was determined to be higher than that in women. ROM shows a wide fluctuation and does not possess high validity. Height, as well as body weight and body mass index have only slight influence on the isokinetic maximum strength in the shoulder of untrained men and women.

Adult↗