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C Banner

Publications and source records attributed to C Banner.

26 records · Page 2Linked to original sources
PubMed1988

Dexamethasone regulates glutamine synthetase expression in rat skeletal muscles.

The regulation of glutamine synthetase expression by dexamethasone was studied in rat skeletal muscles. Daily administration of dexamethasone caused striking enhancement of glutamine synthetase activity in plantaris, soleus, and diaphragm muscles. Northern blot analysis revealed that the dexamethasone-mediated increase of glutamine synthetase activity was associated with dramatically increased levels of glutamine synthetase mRNA. Both glutamine synthetase activity and mRNA levels were significantly elevated in plantaris muscle at 0.5 mg.kg-1.day-1 of dexamethasone, a dose that approximates endogenous corticosteroid levels in animals under severe stress. Quantification of changes in glutamine synthetase mRNA on the basis of total mRNA (by oligo dT hybridization) also revealed a major increase in glutamine synthetase mRNA. Dexamethasone was without effect on beta-tubulin mRNA levels, indicating that glutamine synthetase induction is not part of a global response to glucocorticoids. Dexamethasone treatment resulted in only an approximately 15% increase in glutamine synthetase activity in heart; there was no change in glutamine synthetase mRNA level in this tissue. Thus glucocorticoids regulate glutamine synthetase gene expression in rat skeletal muscles.

Animals↗
PubMed1987

Comparison of human brain and liver glutamate dehydrogenase cDNAS.

In order to investigate suggestions that more than one glutamate dehydrogenase (GDH) gene may be active in humans, seven human brain and seventeen human liver GDH cDNAs were isolated by probing with a 590 base cDNA from the coding region of human brain GDH. No sequence heterogeneity was revealed among any of the cDNAs by an oligonucleotide binding assay, nor did any cDNA appear to encode a hexapeptide contained in a published amino acid sequence of human liver GDH. Homologous regions of three liver and three brain cDNAs had identical sequences over more than 2 kb, including 3' nontranslated regions. This suggests that identical GDH mRNAs are present in human brain and human liver. Although only one gene appears to be expressed, human genomic DNA blots show a pattern of hybridization consistent with the existence of more than one GDH gene.

Amino Acid Sequence↗
PubMed1987

Glutamic acid decarboxylase mRNA in rat brain: regional distribution and effects of intrastriatal kainic acid.

Glutamic acid decarboxylase (GAD) mRNA was quantified in different regions of rat brain using an antisense RNA probe (ribo-probe) prepared from a cloned feline cDNA. In all brain regions studied a single band of GAD mRNA of approximately 3.7 kb was detected. The level of GAD mRNA was highest in the cerebellum, followed by the hypothalamus greater than thalamus greater than striatum greater than hippocampus greater than frontal cortex = parietal cortex greater than or equal to medulla = pons. Since GAD has been previously localized to intrinsic neurons of the striatum, we examined the effects of intrastriatal kainic acid administration on striatal GAD mRNA. The level of GAD mRNA in the kainic acid-lesioned striatum was reduced by 70-75% when compared to the contralateral (unlesioned) striatum. In contrast, the level of glutamine synthetase (an enzyme localized to glia) mRNA was increased approximately 290% in the kainic acid-lesioned striatum. There were no significant differences in GAD mRNA levels between the ipsilateral and contralateral cerebral cortices and hippocampi of rats injected with intrastriatal kainic acid.

Animals↗
PubMed1987

Isolation of a human brain cDNA for glutamate dehydrogenase.

A cDNA has been isolated from a human brain expression library using anti-bovine glutamate dehydrogenase (GDH) antibodies. The cDNA has an open reading frame of 774 nucleotides, which codes for 258 amino acids. The 258-amino-acid sequence is 95% homologous to the carboxy terminus of human liver GDH. This high degree of homology indicates that the cDNA codes for brain GDH. Fourteen differences between the amino acid sequence deduced from this cDNA and the sequence reported for human liver GDH suggest that there may be two active human GDH genes. A cRNA probe synthesized from the cDNA detects a 3.7-kilobase (kb) mRNA from human brain. Rat liver and kidney each contain two GDH mRNAs, 3.5 and 2.8 kb, respectively. The 3.5-kb transcript is prominent in rat brain, whereas the 2.8-kb transcript is barely detectable, a result suggesting that GDH gene expression is differentially controlled in rat brain.

Amino Acid Sequence↗
PubMed1987

Glucocorticoid receptor-mediated induction of glutamine synthetase in skeletal muscle cells in vitro.

We studied the regulation by glucocorticoids of glutamine synthetase in L6 muscle cells in culture. Glutamine synthetase activity was strikingly enhanced by dexamethasone. The dexamethasone-mediated induction of glutamine synthetase activity was blocked by RU38486 [11 beta-(4-dimethylaminophenyl)17 beta-hydroxy-17 alpha-(prop-1-ynyl)estra-4,9-dien-3-one], a glucocorticoid antagonist, indicating the involvement of intracellular glucocorticoid receptors in the induction process. RU38486 alone was without effect. Northern blot analysis revealed that dexamethasone-mediated enhancement of glutamine synthetase activity involves increased levels of glutamine synthetase mRNA. Increased enzyme activity was specific for glucocorticoids; other steroid hormones were essentially without effect. The induction of glutamine synthetase was selective, in that glutaminase activity was not induced by dexamethasone treatment of L6 cells. Thus, glucocorticoids regulate the expression of glutamine synthetase mRNA in cultured muscle cells via interaction with intracellular receptors. Such regulation may be relevant to control of glutamine production by muscle.

Animals↗
PubMed1984

Genes for alkaline protease and neutral protease from Bacillus amyloliquefaciens contain a large open reading frame between the regions coding for signal sequence and mature protein.

The genes for alkaline protease (apr[BamP]) and neutral protease (npr[BamP]) from Bacillus amyloliquefaciens have been isolated and expressed in Bacillus subtilis. The DNA sequences of apr[BamP] and npr[BamP] revealed, in each case, the presence of a large open reading frame. The inferred amino acid sequence of either gene contained a signal sequence and an additional polypeptide sequence ('pro' sequence) preceding the mature protein. Based on DNA sequence, the start point of translation has been identified as amino acid residue - 107 for apr[BamP] and -221 for npr[BamP]. To demonstrate that the start point of translation of apr[BamP] in vivo is probably at codon -107, codon -103 (AAA) was changed to an ochre (TAA) by site-directed mutagenesis. Alkaline protease was produced from this ochre mutant derivative of apr[BamP] only when the host strain was Su+. The presence of a pro sequence may be common to all of the secreted proteases from bacilli.

Amino Acid Sequence↗
PubMedDate not supplied

Influence of physical and chemical characteristics of diesel fuels and exhaust emissions on biological effects of particle extracts: a multivariate statistical analysis of ten diesel fuels.

The emission of diesel exhaust particulates is associated with potentially severe biological effects, e.g., cancer. The aim of the present study was to apply multivariate statistical methods to identify factors that affect the biological potency of these exhausts. Ten diesel fuels were analyzed regarding physical and chemical characteristics. Particulate exhaust emissions were sampled after combustion of these fuels on two makes of heavy duty diesel engines. Particle extracts were chemically analyzed and tested for mutagenicity in the Ames test. Also, the potency of the extracts to competitively inhibit the binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to the Ah receptor was assessed. Relationships between fuel characteristics and biological effects of the extracts were studied, using partial least squares regression (PLS). The most influential chemical fuel parameters included the contents of sulfur, certain polycyclic aromatic compounds (PAC), and naphthenes. Density and flash point were positively correlated with genotoxic potency. Cetane number and upper distillation curve points were negatively correlated with both mutagenicity and Ah receptor affinity. Between 61% and 70% of the biological response data could be explained by the measured chemical and physical factors of the fuels. By PLS modeling of extract data versus the biological response data, 66% of the genotoxicity could be explained, by 41% of the chemical variation. The most important variables, associated with both mutagenicity and Ah receptor affinity, included 1-nitropyrene, particle bound nitrate, indeno[1,2,3-cd]pyrene, and emitted mass of particles. S9-requiring mutagenicity was highly correlated with certain PAC, whereas S9-independent mutagenicity was better correlated with nitrates and 1-nitropyrene. The emission of sulfates also showed a correlation both with the emission of particles and with the biological effects. The results indicate that fuels with biologically less hazardous potentials should have high cetane number and contain less PAC and sulfur. The results also indicate that engine factors affect the formation and emission of nitrated PAC.

Automobiles↗