Deoxyribonucleic Acid Base Compositions of Selected Mycoplasmas and L-Phase Variants

Deoxyribonucleic acid base compositions were determined for 25 Mycoplasma strains and 6 L-phase variant strains. Values obtained correlated well with the results of other investigators.     

Regulation of the meta Cleavage Pathway for Benzoate Oxidation by Pseudomonas putida

Catechol or 2-hydroxymuconic semialdehyde cannot participate as functional inducers of the meta pathway for benzoate metabolism in Pseudomonas putida. Induction of the first two enzymes of the pathway must be mediated by benzoate, or its analogues, as primary substrate.     

The `neurotoxicity'' of l-2,4-diaminobutyric acid

The neurolathyrogen l-2,4-diaminobutyric acid is concentrated by liver, and liver damage can yield neurotoxicity; thus the neurotoxicity caused by this compound may be due to liver damage followed by secondary brain damage. 1. The intraperitoneal administration of toxic doses of l-2,4-diaminobutyric acid to rats resulted in hyperirritability, tremors and convulsions in 12-20hr. and increased the concentration of ammonia of blood and brain slightly and the concentration of glutamine of brain two- to three-fold. By contrast, toxic doses of l-homoarginine, l-lysine, l-leucine and ammonium acetate caused dyspnoea, extreme prostration, and in some cases coma in 15-30min., and increased the concentration of ammonia of blood significantly and the concentration of glutamine of brain slightly. These results indicate that l-2,4-diaminobutyric acid caused a chronic ammonia toxicity, whereas the other amino acids and ammonium acetate resulted in an acute ammonia toxicity. 2. Liver slices from l-2,4-diaminobutyric acid-treated animals and normal liver slices preincubated with l-2,4-diaminobutyric acid utilized ammonia and formed urea at a lower rate than control slices from normal rats. 3. l-2,4-Diaminobutyric acid inhibited competitively ornithine carbamoyltransferase of rat liver homogenates, thus demonstrating that this reaction is a primary site of toxicity for this neurolathyrogen. Although we were unable to show marked elevations of blood ammonia concentration after treatment with l-2,4-diaminobutyric acid, these results are interpreted to mean that ammonia utilization (urea synthesis) in liver is inhibited by l-2,4-diaminobutyric acid and that at least part of the neurotoxicity is due to a prolonged slight increase in body ammonia concentration.     

Microbiological Assay for Organic Compounds in Seawater. II: Distribution of Adenine, Uracil, and Threonine

Biochemically deficient strains of Serratia marinorubra have been isolated with specific requirements for adenine, uracil, and threonine. Standard curves for dose to growth response have been obtained showing a linear sensitivity from 0.5 to 4.0 mg of adenine per liter of seawater, 0.1 to 2.0 mg of uracil per liter of seawater, and 0.5 to 10 mg of threonine per liter of seawater. These mutants have been used to test for the presence of their required metabolites in natural seawater samples from the Gulf of Mexico and adjacent bays. Of the three compounds under investigation, adenine was found in 10 samples, uracil in 2 samples, and threonine in none. The possible significance of these findings to the marine environment is discussed.     

Novel redistribution of myosin-containing filaments in cultured keratinocytes identified by a human monoclonal autoantibody

Summary A time-dependent redistribution of microfilaments was observed in cultured human keratinocytes using a human monoclonal autoantibody specific for myosin. Immunofluorescent staining revealed that 5 days after plating keratinocytes in either 0.1 mM or 2.0 mM Ca⁺⁺, myosin was distributed uniformly throughout the cytoplasm. At day 6, parallel arrays of myosin-containing microfilaments were prominent in the cell peripheries. At day 7 the microfilaments formed circumferential rings. The distribution of the microfilaments was disrupted by cytochalasin but not by colchicine, indicating that this novel distribution of myosin was not dependent on colchicine-sensitive vimentin intermediate filaments. The time-dependent redistribution of myosin was not influenced by cell population density, cell shape or cell cycle phase, except for mitotic cells in which myosin was distributed diffusely through the cytoplasm. If, as suggested by Kolega (9), microfilaments align parallel to the direction of applied tension, the redistribution of myosin-containing microfilaments in cultured keratinocytes may reflect the increased tension between cells resulting from increasing strength of cell-cell junctions over time. In sectioned human skin, myosin was localized in the peripheral cytoplasm of stratified epidermal cells. Tensions arising from the numerous desmosomal junctions between cellsin vivo could account for this distribution of myosin. Supported by grant NS-23537 (V. A. L.) from the National Institutes of Health, Bethesda, MD, and by the Mayo Foundation. C. L. W. is recipient of the Kermit E. Osserman and Blanche McClure Fellowship, 1987, National Myasthenia Gravis Foundation.     

Production and characterization of a compound inhibitory to Vibrio parahaemolyticus from Proteus vulgaris

The production and characteristics of a compound in Proteus vulgaris G cultures which was capable of inhibiting Vibrio parahaemolyticus and other food-borne pathogens was investigated. Production was influenced by medium composition, pH and temperature but not by the extent of aeration. The compound was most inhibitory at the optimum temperature for growth of V. parahaemolyticus. The inhibitor was most stable at pH 7·0 and inhibition occurred even after heating at 70°C for 30 min and after autoclaving. Ultrafiltration showed that the inhibitor had a molecular weight less than 1000. Thin layer chromatography of filtrates and subsequent peptidase digestion indicated that it was at least in part a peptide. The inhibitor purified by Sephadex G-15 gel filtration had a calculated molecular weight of 731 and contained only six amino acids.     

Caffeine inhibition of cytokinesis: Ultrastructure of cell plate formation/degradation

Summary Caffeine is a potent inhibitor of cell plate formation in dividing plant cells. Previous studies living cells reveal that the drug always permits the cell plate to arise and grow normally until about 80% complete, but then causes it to break down. In the present investigation we examine this formation/degradation cycle at the ultrastructure level. Our results show that during the formation phase the caffeine treated plate is indistinguishable from untreated controls. Phragmoplast microtubules arise and align in the interzone, Golgi vesicles are produced and aggregate in a line that defines the young cell plate, and considerable fusion of these vesicles occurs to form islands of plate material. However, under the influence of caffeine these islands do not fuse to form the enlarged lamellar expanses characteristic of maturing cell plates. Instead, the partially fused material reverts to small vesicles which appear to become resorbed by the cellular membrane systems. The resorption process continues leaving no evidence of the previously developing plate, although occasionally we observe a stub of fused vesicles attached to the parent wall. Following cell plate disintegration the reformed nuclei move close together and occupy the central region of the cell. These observations focus attention on the consolidation phase of cell plate formation as the one being maximally affected by caffeine.Dedicated to the memory of Professor Oswald Kiermayer     

Mutation analysis of the cystic fibrosis transmembrane regulator gene in native American populations of the southwest

We report DNA and clinical analyses of cystic fibrosis (CF) in two previously unstudied, genetically isolated populations: Pueblo and Navajo Native Americans. Direct mutation analysis of six mutations of the CFTR gene--namely, delta F508, G542X, G551D, R553X, N1303K, and W1282X--was performed on PCR-amplified genomic DNA extracted from blood samples. Haplotype analyses with marker/enzyme pairs XV2c/TaqI and KM19/PstI were performed as well. Of the 12 affected individuals studied, no delta F508 mutation was detected; only one G542X mutation was found. None of the other mutations was detected. All affected individuals have either an AA, AC, or CC haplotype, except for the one carrying the G542X mutation, who has the haplotype AB. Clinically, six of the affected individuals examined exhibit growth deficiency, and five (all from the Zuni Pueblo) have a severe CF phenotype. Four of the six Zunis with CF are also microcephalic, a finding not previously noted in CF patients. Our DNA data have serious implications for risk assessment of CF carrier status for these people.