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B A Bryan

Publications and source records attributed to B A Bryan.

16 recordsLinked to original sources
PubMed2005

The Rho family of small GTPases: crucial regulators of skeletal myogenesis.

The Rho family of small GTPases is involved in a diverse array of cellular processes, including regulation of the actin cytoskeleton, cell polarity, microtubule dynamics, membrane transport pathways and transcription factor activity. Recent findings have implicated the Rho proteins as key regulators of the skeletal myogenic program; however, much controversy presently exists as to the precise role of these proteins in this process. This review examines the present controversial findings pertaining to the Rho family's regulation of skeletal myogenesis and extrapolates from both other differentiation systems and recently published data the possible mechanisms by which these proteins function in the myogenic cascade.

Animals↗
PubMed2003

Evidence for control of nitrogen metabolism by a START-dependent mechanism in Saccharomyces cerevisiae.

It is generally thought that cell growth and metabolism regulate cell division and not vice versa. Here, we examined Saccharomyces cerevisiae cells growing under conditions of continuous culture in a chemostat. We found that loss of G1 cyclins, or inactivation of the cyclin-dependent kinase Cdc28p, reduced the activity of glutamate synthase (Glt1p), a key enzyme in nitrogen assimilation. We also present evidence indicating that the G1 cyclin-dependent control of Glt1p may involve Jem1p, a DnaJ-type chaperone. Our results suggest that completion of START may be linked to nitrogen metabolism.

Base Sequence↗
PubMed1986

Variation in composition and yield of exopolysaccharides produced by Klebsiella sp. strain K32 and Acinetobacter calcoaceticus BD4.

The exopolysaccharides produced by Klebsiella sp. strain K32 and Acinetobacter calcoaceticus BD4 under different growth conditions have been analyzed for sugar composition. The first use of ion chromatography for the quantitative determination of microbial exopolysaccharide composition is reported. Klebsiella sp. strain K32 produced a polymer composed of rhamnose, galactose, and mannose early in its fermentation. The composition of the polymer varied markedly depending on the growth stage of the organism. Klebsiella sp. strain K32 grown in a fermentor produced a polymer which was rich in mannose during early exponential growth in a complex medium, but in the late stationary phase it did not contain detectable levels of mannose. The rhamnose present in the polymer increased from 12 to 55% over the course of growth, whereas galactose decreased from 63 to 45%. A. calcoaceticus BD4 produced a polymer containing rhamnose, glucose, mannose throughout its growth and stationary phase. Klebsiella sp. strain K32 and A. calcoaceticus BD4 were grown on various carbon sources in shake flasks. The polymer yield and composition from both organisms were found to vary with the carbon source. The exopolysaccharide with the highest mannose composition was obtained by using rhamnose as a carbon source for both organisms. These and other data suggest that regulatory changes caused by growth on different substrates result in either the production of a different distribution of polymers or a change in exopolysaccharide structure.

Acinetobacter↗
PubMed1985

Inability of Pseudomonas stutzeri denitrification mutants with the phenotype of Pseudomonas aeruginosa to grow in nitrous oxide.

Pseudomonas aeruginosa PAO1 reduced nitrous oxide to dinitrogen but did not grow anaerobically in nitrous oxide. Two transposon insertion Nos- mutants of Pseudomonas stutzeri exhibited the P. aeruginosa phenotype. Growth yield studies demonstrated that nitrous oxide produced in vivo was productively respired, but nitrous oxide supplied exogenously was not. The defect may be in electron transport or in nitrous oxide uptake.

Kinetics↗
PubMed1984

Increase of natural N enrichment of soybean nodules with mean nodule mass.

The (15)N abundance of soybean (Glycine max L. Merrill var Harosoy) nodules is usually greater than it is for other tissues or for atmospheric N(2). Results of experiments in which nodules were separated by size show that the magnitude of the (15)N enrichment is correlated with nodule mass. The results support the hypothesis that (15)N enrichment of nodules results from differential N isotopic fractionation for synthesis of nodule tissue versus synthesis of compounds for export from the nodule. The physiological significance of this hypothesis is that it requires that a substantial fraction of the N for nodule tissue synthesis in (15)N-enriched nodules be N recently fixed within the same nodule.

Journal Article↗
PubMed1983

Variable expression of the nitrogen isotope effect associated with denitrification of nitrite.

The overall isotopic fractionation factor observed for denitrification of NO-2 by resting cultures and cell-free extracts of Pseudomonas stutzeri varied widely with the concentration of NO-2 and reductant. The observed isotope effect (beta obs) increased linearly with velocity when the concentration of nitrite was varied and decreased with velocity when reductant concentration was varied. At any given ratio of velocity to maximum velocity, beta obs was approximately the same in intact cells and cell free extracts. These results indicate the following: (a) neither uptake (whole cells) nor enzyme-substrate association (cell-free extracts) is the sole cause of saturation of the overall rate as [NO-2] is increased; (b) a reductive step lies beyond the initial step and at or before the first unidirectional step; and (c) in intact cells, uptake of NO-2 by the cell and egress of NO-2 from it are very rapid compared to reduction at all concentrations of NO-2. A corollary of the last conclusion is that variation of beta obs in intact cells is due entirely to variation in the relative rates of intracellular steps of the denitrification process. The linear relation between beta obs and velocity imposes constraints on any proposed mechanism of denitrification.

Isotope Labeling↗
PubMed1983

Site of natural N enrichment of soybean nodules.

Soybean (Glycine max L. Merrill) nodules are usually more enriched in (15)N than other tissues. We show that both bacteroids and nodule cortex are considerably more enriched in (15)N than nodule cytosol, with bacteroids being slightly more enriched than the cortex. Hence, (15)N enrichment occurs in cells of both plant and bacterial origin.

Journal Article↗
PubMed1983

Relationship between N(2)-Fixing Efficiency and Natural N Enrichment of Soybean Nodules.

Non-nodular tissue of soybean (Glycine max L. Merrill) plants grown hydroponically in the absence of added N have a (15)N abundance close to that of atmospheric N(2). In contrast, nodules are usually enriched in (15)N. In this paper, we report measurements of the (15)N abundance of foliar tissue and nodules of soybeans inoculated with 11 variably efficient strains of Rhizobum japonicum and grown hydroponically with no added N. The efficiency of the 11 symbioses varied over a wide range as judged by a 16-fold difference in N content. The degree of (15)N enrichment of nodules was closely correlated with N(2)-fixing efficiency (milligrams N fixed per milligram N in the nodules).These results confirm prior preliminary data based on six variably efficient R. japonicum strains. The strong correlation between (N)N enrichment of soybean nodules and N(2)-fixing efficiency is consistent with the hypothesis that new nodule tissue is synthesized from a pool of recently fixed N within the same nodule.

Journal Article↗
PubMed1982

N abundance of nodules as an indicator of N metabolism in n(2)-fixing plants.

This paper expands upon previous reports of (15)N elevation in nodules (compared to other tissues) of N(2)-fixing plants. N(2)-Fixing nodules of Glycine max (soybeans), Vigna unguiculata (cowpea), Phaseolus vulgaris (common bean), Phaseolus coccineus (scarlet runner bean), Prosopis glandulosa (mesquite), and Olneya tesota (desert ironwood) were enriched in (15)N. Nodules of Vicia faba (fava beans), Arachis hypogaea (peanut), Trifolium pratense (red clover), Pisum sativum (pea), Lathyrus sativus (grass pea), Medicago sativa (alfalfa), and Lupinus mutabilis (South American lupine) were not; nor were the nodules of nine species of N(2)-fixing nonlegumes. The nitrogen of ineffective nodules of soybeans and cowpeas was not enriched in (15)N. Thus, (15)N elevation in nodules of these plants depends on active N(2)-fixation. Results obtained so far on the generality of (15)N enrichment in N(2)-fixing nodules suggest that only the nodules of plants which actively fix N(2) and which transport allantoin or allantoic acid exhibit (15)N enrichment.

Journal Article↗
PubMed1976

Denitrification.

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Air Pollution↗