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Biomedical subjects

F Mayer

Publications and source records attributed to F Mayer.

At least 199 records · Page 11Linked to original sources
PubMed1982

Analysis of structure-function relationships in citrate lyase isolated from Rhodopseudomonas gelatinosa as revealed by cross-linking and immunoelectron microscopy.

Citrate lyase (EC 4.1.3.6) isolated from Rhodopseudomonas gelatinosa was analyzed using cross-linking experiments and immunoelectron microscopy. Different cross-linking reagents and antibodies directed against citrate lyase and specifically against all three subunit types (L, M and S) were applied. A structure-function model is proposed for citrate lyase from R. gelatinosa: the enzyme occurs in two configurations, 'rings' and 'stars'. The ring contains two identical layers each consisting of three subunits L, with one subunit S as a polar cap sitting on each L, and three subunits M in alternating sequence (18 subunits altogether). In the star, the same 18 subunits are arranged in a different way. Whereas the subunits L are located at the periphery, the subunits M are concentrated in the center of the particle. The subunits S are positioned relative to L as in the ring; however, their location relative to the subunits M is changed. By transition from ring to star, areas on S are brought into contact with areas on M by rotation of structural units, consisting of one L, one M and one S subunit per layer, against each other, with S of one structural unit close to M of the neighbouring structural unit. This transition is assumed to work also in reversed direction. The observation of rings and stars as two distinct molecular forms is proposed to reflect the two states of citrate lyase, the ring being the form where substrate is bound by acyl exchange, and the star being the form where the substrate is consumed by cleavage, i.e. the catalyzed reaction is completed.

Cross-Linking Reagents↗
PubMed1981

Clostridium aceticum (Wieringa), a microorganism producing acetic acid from molecular hydrogen and carbon dioxide.

Spores of Clostridium aceticum (Wieringa) from 1947 have been revived, and a study for a redescription of this microorganism has been carried out. C. aceticum was Gram negative. The cells were rodshaped and peritrichously flagellated. Round spores were formed in terminal position. The DNA contained 33 mol % guanine plus cytosine. The organism was obligately anaerobic and grew either chemolithotrophically with H2 + CO2 or chemoorganotrophically with compounds such as fructose, L-glutamate, L-malate or pyruvate. H2 and CO2 were converted to acetic acid according to the following equation: 2CO2 + 4H2 leads to CH3COOH + 2H2O The optimal temperature for growth was 30 degrees C. The optimal pH for chemolithotrophic growth was 8.3. The doubling times for chemolithotrophic and chemoorganotrophic growth were 25 and 8 h, respectively.

Acetates↗
PubMed1981

Studies on an isolated West Indies population: I. Analysis of HLA genotypes.

The transmission of HLA genes was studied in an isolated population of French origin on the lesser Antilles islands in the West Indies. The study of 74 unrelated individuals, 44 of whom were genotyped, was carried out for the alleles of HLA loci: A, B, C and Bf (proactivator factor of properdin). As a result of the founder effect and the inbreeding process, the HLA haplotypes were noted to be less polymorphic than in a French continental population. Two haplotypes: A2, Cw5, B12, BfS and A3, C-, B14, BfF represent 24% of the observed haplotypes, and only 2% of the reference haplotypes in France. No significant excess or deficit of homozygotes was observed at the A and B loci.

Deafness↗
PubMed1981

Substructure of crystalline peroxisomes in methanol-grown Hansenula polymorpha: evidence for an in vivo crystal of alcohol oxidase.

The substructural organization of completely crystalline peroxisomes present in Hansenula polymorpha cells grown under methanol limitation in a chemostat was investigated by different cytochemical and ultrastructural techniques. Time-dependent cytochemical staining experiments indicated that activities of the two main constituents of these organelles, namely, alcohol oxidase and catalase, were present throughout the crystalline matrix. Catalase was completely removed from isolated peroxisomes by osmotic shock treatment. After such treatment, the ultrastructure of the crystalline matrix of the organelles remained virtually intact. Because alcohol oxidase activity was still present in this matrix, it was concluded that alcohol oxidase protein is the only structural element of the peroxisomal crystalloids. The molecular architecture of the crystalloids was investigated in ultrathin cryosections which permitted recognition of individual molecules in the crystalline matrix. Depending on the plane of sectioning, different crystalline patterns were observed. Tilting experiments indicated that these images were caused by superposition of octameric alcohol oxidase molecules arranged in a tetragonal lattice. A three-dimensional model of the crystalloid is presented. The repeating unit of this structure is composed of four alcohol oxidase molecules. The crystalloid represents an open structure, which may explain the observed free mobility of catalase molecules.

Alcohol Oxidoreductases↗
PubMed1981

[Skin necroses in cryoglobulinemia].

The dermatological symptoms of cryoglobulinemia and the simple demonstration of cryoproteins by cooling of serum and plasma respectively is described in a patient.

Aged↗
PubMed1980

Characterization and comparison of the DNAs of the three closely related bacteriophages gd, ge and gf with the genome DNA of the hydrogen-oxidizing host strain Pseudomonas pseudoflava GA3.

The double-stranded (ds)DNAs of the three closely related temperate Pseudomonas pseudoflava bacteriophages gd, ge and gf were studied biochemically and biophysically. The GC content of the DNA was 67.4 +/- 0.5% and differed only slightly from that of the host P. pseudoflava. By electron microscopic length measurements a mol. wt. of 26.1 X 10(6) to 26.7 X 10(6) was calculated for the three bacteriophage DNAs. Homogeneity of the bacteriophage DNAs was further demonstrated by specific cleavage with restriction endonucleases WcoRI and HindIII. It was concluded that the three homo-immune bacteriophages are identical. The genome size of the host P. pseudoflava GA3 was 3.7 X 10(9) as calculated from optical renaturation rate measurement with Xanthomonas pelargonii reference DNA. The bacteriophage gd genome thus amounts to 0.7% of the chromosome of this bacterial host.

Bacteriophages↗
PubMed1980

On the structure of crystalline ribulosebisphosphate carboxylase from Alcaligenes eutrophus.

Ribulosebisphosphate carboxylase from the hydrogen bacterium Alcaligenes eutrophus having a molecular weight of 534000 and consisting of eight large and eight small subunits has been crystallized by microdialysis using inorganic as well as organic precipitating agents. Crystals have tetragonal space group P42212, a = b = 11.27 nm, c = 20.14 nm, and contain one quarter molecule per asymmetric unit. X-rays are diffracted to 0.35-nm resolution on still photographs. Light optical diffractions of electron micrographs of thin sectioned crystals displayed patterns which could be interpreted on the basis of the unit cell determined by X-rays. Packing considerations are in accord with our earlier proposal regarding the subunit arrangement of this enzyme which differs from that reported for tobacco ribulosebisphosphate carboxylase.

Alcaligenes↗
PubMed1980

Further electron microscope studies on pyruvate carboxylase.

Using negative staining and electron microscopic tilting techniques in conjunction with modelling experiments, the fine structure of chicken, sheep and rat pyruvate carboxylases has been studied. The overall configuration appears to be a tetrahedron-like structure consisting of two pairs of subunits in two different planes orthogonal to each other with the opposing pairs of subunits interacting with each other on their convex surfaces. The predominant form of the enzyme particles mounted and stained in the presence of acetyl-coenzyme A consisted of a compact, triangular outline enclosing three readily visible intensity maxima. When samples were mounted in the absence of acetyl-coenzyme A the molecules were more 'open' predominantly rhomboid structures. From tilting experiments it is concluded that the rhomboid images found in the absence of acetyl-coenzyme A represent partly or wholly flattened forms of the tetrahedron-like molecule. A feature of the enzyme when mounted in the absence of acetyl-coenzyme A was the existence of a 'cleft' along the longitudinal midline of each subunit, suggesting that the subunits may consist of two distinct domains.

Acetyl Coenzyme A↗
PubMed1979

[Electron microscopic studies of the insertion of pili in the newly isolated hydrogen-oxidizing bacterium 2K1].

Cells of the hydrogen-oxidizing bacterium 2K1 exhibited numerous pili of varying length, with a diameter of 7--8 nm as measured from negatively stained samples. At the basis of each pilus, a cell wall differentiation was observed appearing, in face-on-view, as a ring-like structure made up of subunits, and in side-on view as a hollow cylinder penetrating through the cell wall. It is assumed that these ring-like structures are in direct relation with the presence of the pili. As the number of ring-like structures per cell was higher than the number of pili per cell, rings without associated pili might either be sites of polymerizing pili, or "dead" pilus channel complexes out of function due to pilus break-down.

Bacteria↗
PubMed1979

Structural analysis of four strains of Paracoccus denitrificans.

Two out of eleven newly isolated strains of Paracoccus denitrificans were investigated by light and electron microscopic methods and compared with two strains of P. denitrificans already kept in culture collections. Samples were taken from different growth phases revealing short rods and nearly spherical cells in the exponential growth phase, and an increasing ratio of nearly spherical cells in the stationary growth phase. Cell division followed the binary fission mode; higher cell aggregates were not observed. Fine structural analysis revealed extracellular surface material stainable with Ruthenium red, a gram-negative cell wall and different storage material inclusions. Structural properties and variations within the four strains under investigation are discussed and compared with those of related bacteria.

Cell Division↗
PubMed1978

Further studies on the quaternary structure of D-ribulose-1, 5-bisphosphate carboxylase from Alcaligenes eutrophus.

Homogeneous D-ribulose-1,5-bisphosphate carboxylase, isolated from the hydrogen bacterium Alcaligenes eutrophus, has been studied by analytical ultracentrifugation. Sedimentation equilibrium experiments showed the enzyme to have a molecular weight M c =0 r =534000. The sedimentation coefficient was S0(20); w = 14.1S. The two types of subunits constituting the ribulosebisphosphate carboxylase were separated by gel filtration in the presence of sodium dodecylsulphate and the amino acid compositions of the isolated large and small subunits were determined. Rabbit antibodies were developed against the ribulosebisphosphate carboxylase and its isolated subunits. The specific reactivity of the respective antibodies with their homologous antigens was proven by double immunodiffusion and quantitative immunoprecipitation analyses. Antibodies elicited against the whole enzyme also reacted with both the isolated large and small subunits as did the subunit-specific antibodies with the whole enzyme. There was no immunological correspondence between the large and the small subunits. The specific inhibition of the enzyme activity by antibodies directed against sites on the large subunit suggests that the catalytic function resides in the large subunit. Electron microscopic examination of antibody . carboxylase complexes formed upon mixing of the specific immunoglobulins G with the enzyme was used to verify the arrangement of the large and small subunits in our recently proposed structural model of the enzyme molecule. The results confirmed that the large subunits are located in the central two layers of the four-layered enzyme molecule, whereas the two outer layers consist of small subunits. The observations are discussed with respect to an alternative model for the quaternary structure of ribulosebisphosphate carboxylase from tobacco.

Alcaligenes↗
PubMed1978

Isolation of lipopolysaccharides and the effect of polymyxin B on the outer membrane of Corynebacterium autotrophicum.

Lipopolysaccharides (LPS) from Corynebacterium autotrophicum were isolated and analyzed. Autotrophically grown cells contained 2--5 mg of partly purified LPS per g dry weight of lyophilized cells. Serological cross reaction with Lipid A antigen of Salmonella minnesota confirmed the presence of LPS in C. autotrophicum. Electron microscopy of negatively stained Polymyxin B-treated cells showed formation of blebs on the Outer Membrane indicating an interaction of Polymyxin B specifically with LPS. Up to now, no Gram-positive organisms are known which contain any LPS. Thus, C. autotrophicum, though giving opposite results when the Gram-staining reaction was applied by several authors, has to be classified into the group of Gram-negative bacteria.

Cell Wall↗
PubMed1978

Isolation and characterization of polysheaths, phage tail-like defective bacteriophages of Alcaligenes eutrophus H 16.

Polysheaths were spontaneously formed inside cells of the hydrogen bacterium Alcaligenes eutrophus H 16. These particles are long tube-like structures of 24 nm diam. belonging to the phage tail-like defective bacteriophages (Lotz, 1976). In mid log-phase fermenter-grown cells, polysheaths were observed in about 20% of all cells sectioned. Evidence is provided for an inhibition of cell fission by polysheaths. Polysheaths were isolated by differential centrifugation and precipitation techniques using PEG and antibodies. The morphology of polysheaths was investigated electron microscopically by negative staining, ultrathin sectioning and metal shadowing. A surface lattice of the polysheath was derived from light optical diffraction data. The particles were also characterized by their biochemical and biophysical features: mol. wt. of the subunit determined by SDS-gel electrophoresis (58 000), amino acid composition, isoelectric point (4.4), u.v. absorbance spectrum indicating the absence of nucleic acid, buoyant density (1.258), and stability against denaturants and proteolytic enzymes.

Alcaligenes↗
PubMed1978

[Classical and modified intramedullary nailing in osteomyelitis pseudoarthroses].

13 cases of osteomyelitic pseudarthroses following injury were treated by the authors, by means of intramedullary nailing. 5 of these patients already cured are introduced in detail in the article. Intramedullary nailing in the classic manner and its modification, using bolts as well, were performed alike. The authors have a favourable impression after these series. No septic complication occured. Intramedullary nailing is a good method in the management of this serious sequel to fracture treatment.

Bone Nails↗