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Biomedical subjects

M Orlowski

Publications and source records attributed to M Orlowski.

At least 109 records · Page 6Linked to original sources
PubMed1980

Cyclic adenosine 3',5'-monophosphate and germination of sporangiospores from the fungus Mucor.

Cyclic adenosine 3',5'-monophosphate (cAMP) metabolism was examined in germinating sporangiospores of Mucor genevensis and Mucor mucedo. Exogenous cAMP prevented normal hyphal development from sporangiospores. Internal pools of cAMP fluctuated profoundly during development. Spherical growth of the spores was characterized by large pools of cAMP whereas germ tube emergence and hyphal elongation were characterized by small pools of cAMP. These observations suggest a possible role for cAMP in sporangiospore germination. Adenylate cyclase activities fluctuated significantly during germination with maximum values attained during spherical growth. In contrast, cAMP phosphodiesterase activities remained constant throughout germination. Internal cAMP levels may therefore be regulated by adjustment of adenylate cyclase activities. The binding of cAMP by soluble cell proteins was measured. cAMP-binding activity changed greatly during germination. Dormant and spherically growing spores possessed the highest activities. Developing hyphae contained the lowest activities. Use of the photoaffinity label, 8-azido-[32P]cAMP, in conjunction with sodium dodecyl sulfate-polyacrylamide-gel electrophoresis allowed the identification of a small population of morphogenetic-stage-specific proteins which bind cAMP and may be of regulatory significance to development.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Cation-sensitive neutral endopeptidase: isolation and specificity of the bovine pituitary enzyme.

A highly purified preparation of a cation-sensitive neutral endopeptidase was obtained from bovine pituitaries. The enzyme constitutes almost 0.1% of the protein in bovine pituitary homogenates. Polyacrylamide gel electrophoresis of the enzyme showed a single protein band, and in gel filtration experiments on calibrated Sepharose 6B columns the enzyme eluted slightly ahead of thyroglobulin, suggesting an apparent molecular weight of about 700,000. Polyacrylamide gel electrophoresis in SDS-containing buffers indicated the presence of three major components with molecular weights ranging from about 24,000 to 28,000. The enzyme hydrolyzes bonds between hydrophobic and small neutral amino acids in both model synthetic substrates and biologically active peptides such as substance P, LH-RH, and bradykinin. Peptide bonds in which the carbonyl group is contributed by a glutamyl or arginyl residue are also hydrolyzed, especially if they are preceded in the sequence by hydrophobic amino acids. Leupeptin exclusively inhibited enzymatic activity toward the arginine-containing substrates. This observation, together with the high molecular weight and broad specificity of the enzyme, raised the possibility that the isolated enzyme represents a proteolytic complex composed of units with distinctly different activities. Preliminary attempts to dissociate the enzyme into catalytic units of lower molecular weight were not successful and led to loss of activity.

Animals↗
PubMed1980

Cyclic adenosine 3',5'-monophosphate binding protein in developing myxospores of Myxococcus xanthus.

The interaction of cyclic adenosine 3',5'-monophosphate (cAMP) with specific protein molecules was examined in the high-speed supernatant fraction of extracts made at stages throughout glycerol-induced myxospore development in Myxococcus xanthus. Experiments using 8-azido[32P]cAMP, a photoaffinity analogue of cAMP, and SDS - polyacrylamide gel electrophoresis showed that the nucleotide interacts with only a single protein band of 12 500 molecular weight. Both the identiy and amount of this protein remained constant throughout development. The binding protein was specific for cAMP; other nucleotides did not compete with cAMP for binding sites. A Scatchard analysis showed evidence of only a single class of binding sites with a high affinity for cAMP.

Binding Sites↗
PubMed1979

Changing pattern of cyclic AMP-binding proteins during germination of Mucor racemosus sporangiospores.

Interation of cyclic AMP with a profoundly changing pattern of specific binding proteins was shown during aerobic germination of sporangiospores from the fungus Mucor racemosus. 32P-labeled 8-azido-cycli AMP, an analogue of cyclic AMP that forms a covalent linkage with the binding proteins under u.v. light, was used as the ligand. Binding proteins carrying this photoaffinity label were separated by polyacrylamide-gel electrophoresis and identified by radioautography. Equibiltrium dissociation constants (Kd) and binding-response curves in the presence of competing nucleotides were identical for both 8-azido-cyclic [32P]AMP and cyclic [3H]AMP. A quantitative binding assay with both 8-azido-cyclic [32P]AMP and cyclic [3H]AMP over the time course of sporangiospore germination indicated a parallel relationship between cyclic AMP-binding capacity and the intracellular concentrations of cyclic AMP reported in a previous study [Paznokas & Sypherd (1975) J. Bacteriol. 124, 134--139]. Both of these parameters attained transient high values at a time of development when addition of exogenous cyclic AMP prevents hyphal-germ-tube emergence. The measured Kd values did not change during sport germination.

Affinity Labels↗
PubMed1979

gamma-Glutamyl DOPA and gamma-glutamyl dopamine: effect on plasma glucose levels.

gamma-Glutamyl-L-3,4-dihydroxyphenylalanine (gamma-glutamyl DOPA) and gamma-glutamyldopamine (gamma-glutamyl DA) are kidney specific prodrugs. Their effect on plasma glucose levels in the rat was compared to that of L-DOPA and dopamine (DA) after a 30 min intravenous infusion. L-DOPA and DA induced hyperglycemia after 15 min of druginfusion. A more marked and protracted elevation of plasma glucose was observed after infusion of gamma-glutamyl DA. By gamma-glutamyl DOPA had no effect on plasma glucose levels in spite of the high accumulation of DA in the pancreas after this prodrug. Of the various dopamine produrgs studied only gamma-glutamyl DOPA was not hyperglycemic in doses that are known to increase renal plasma flow in the rat. A simplified new procedure for the synthesis of gamma-glutamyl DA is described.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1979

Degradation of luteinizing hormone-releasing hormone (LHRH) by brain prolyl endopeptidase with release of des-glycinamide LHRH and glycinamide.

A highly purified preparation of rabbit brain prolyl endopeptidase cleaved the decapeptide luteinizing hormone-releasing hormone (LHRH) at the ProGly . NH2 bond leading to the release within 1-3 h incubation at 37 degrees C of des-glycinamide LHRH and glycinamide. Evidence for this site of cleavage was obtained by the detection of glycinamide or glycine and groups by a microdanyslation procedure, and by separation of the breakdown products by high performance liquid chromatography (HPLC) on a revers phase C-18 column. Incubation led to the appearance of two new peaks as detected by HPLC one of which was collected and shown to have the composition consistent with des-glycinamide LHRH. The other peak ran in the position identical to that of authentic glycinamide. Results suggest that prolyl endopeptidase could play a role in the inactivation of LHRH in vivo.

Animals↗
PubMed1978

Regulation of translation rate during morphogenesis in the fungus Mucor.

The present study was undertaken in order to elucidate the molecular mechanisms responsible for regulating changes in the specific rate of protein synthesis during the yeast-to-hyphae morphogenesis in the fungus, Mucor racemosus. The distribution of ribosomes between active polysomes and monosomes and inactive subunits was determined by means of pulse-labeling and density gradient fractionation techniques. The percentage of ribosomes active in protein synthesis was observed to decrease throughout the morphological transition. The rate of amino acid addition to nascent polypeptide chains was calculated and the transit time of messenger RNA translation was measured. The results showed a significant increase in the velocity of ribosome movement along the message which was continuously adjusted throughout hyphal development.

Fungal Proteins↗
PubMed1978

Synthesis of ophthalmic acid in liver and kidney in vivo.

The synthesis of ophthalmic acid, an analogue of glutathione, was studied in vivo in mouse liver and kidney after administration of either L-alpha-aminobutyrate or L-gamma-glutamyl-L-alpha-aminobutyrate as precursor. L-alpha-aminobutyrate accumulated to a much greater extent, and induced a much greater synthesis of ophthalmic acid in the liver than in the kidney. In contrast, L-gamma-glutamyl-L-alpha-aminobutyrate initiated a large and more rapid synthesis of ophthalmic acid in the kidney than in the liver. Experiments with L-gamma-[G(-14)C]glutamyl-L-alpha-aminobutyrate showed that, although part of the dipeptide is degraded to its constituent amino acids, a significant proportion is directly incorporated into kidney ophthalmic acid. In contrast L-gamma-glutamyl-L-alpha-aminobutyrate serves poorly as a direct precursor of liver ophthalmic acid. The present results show that kidney gamma-glutamyl tripeptide synthesis can proceed directly from an exogenous gamma-glutamyl dipeptide precursor.

Aminobutyrates↗