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M E Baker

Publications and source records attributed to M E Baker.

At least 109 records · Page 6Linked to original sources
PubMed1992

Effect of protease inhibitors and substrates on 3,5,3'-triiodothyronine binding to rat liver nuclear receptors.

The effect of protease inhibitors N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) and N-carbobenzoxy-L-phenylalanine chloromethyl ketone (ZPCK) at concentrations ranging from 1.5 x 10(-6) mol/l to 1.5 x 10(-4) mol/l on the specific binding of 3,5,3'-triiodothyronine (T3) to rat liver nuclear receptors was evaluated. Both TPCK at 1.5 x 10(-5) mol/l (P < 0.001) and ZPCK at 1.5 x 10(-6) mol/l (P < 0.05) showed the inhibition of T3 binding to nuclear receptors. The evaluation of T3 binding data following separation of unbound TPCK from treated nuclear receptors on a Sephadex G-25 column showed that the inhibition of T3 binding was irreversible, since a substantial decrease of the equilibrium association constant (Ka) was found when compared to the mock samples lacking TPCK. In addition, similar inhibitory effect on T3 specific binding to rat liver nuclear receptors was found at 5.0 x 10(-4) mol/l by protease substrates L-tyrosine benzyl ester (P < 0.001), L-tyrosine ethyl ester (P < 0.02), L-tryptophan methyl ester (P < 0.02) and L-tryptophan ethyl ester (P < 0.05). The data suggest that: 1. both protease inhibitors and substrates tested inhibited T3 specific binding to T3 nuclear receptors; 2. this may support the hypothesis that T3 receptors like other receptors encoded by c-erbA gene possess a site that recognize both serine protease inhibitors and substrates in its hormone binding domain.

Amino Acid Chloromethyl Ketones↗
PubMed1991

Genealogy of regulation of human sex and adrenal function, prostaglandin action, snapdragon and petunia flower colors, antibiotics, and nitrogen fixation: functional diversity from two ancestral dehydrogenases.

Metabolism of steroid hormones by dehydrogenases is an important mechanism for regulating steroid hormone action. Analysis of recently reported amino acid sequences of 11 beta-hydroxysteroid dehydrogenase, 17 beta-hydroxysteroid dehydrogenase, and 3 alpha, 20 beta-hydroxysteroid dehydrogenase reveals that they are descended from a common ancestor. Unexpectedly, this superfamily of dehydrogenases has other interesting relatives: 15-hydroxyprostaglandin dehydrogenase, proteins found in nitrogen-fixing bacteria, and enzymes important in the synthesis of antibiotics. The novel lineage of these proteins and the actions of flavonoids in regulating gene transcription in nitrogen-fixing bacteria and mammals provide new insights into the evolution of regulation of gene transcription by intercellular signals in multicellular animals.

Amino Acid Sequence↗
PubMed1991

Evolution of enzymatic regulation of prostaglandin action: novel connections to regulation of human sex and adrenal function, antibiotic synthesis and nitrogen fixation.

The recent determination of the amino acid sequences of enzymes that metabolize prostaglandins and steroids has revealed interesting connections between some of these enzymes. Human placental 15-hydroxyprostaglandin dehydrogenase, which catalyzes the oxidation of the C15 alcohol on prostaglandins E2 and F2 alpha, is homologous to 11 beta-hydroxysteroid, 17 beta-hydroxysteroid, and 3 alpha, 20 beta-hydroxysteroid dehydrogenases. That is, these four enzymes are derived from a common ancestor. Moreover, enzymes important in synthesis of antibiotics and proteins synthesized by soil bacteria that form nitrogen-fixing nodules in alfalfa and soybeans are homologous to 15-hydroxyprostaglandin dehydrogenase. These homologies provide important insights into the origins of intercellular communication that is mediated by prostaglandins, steroids, and fatty acids.

Amino Acid Sequence↗
PubMed1991

Similarity between the amino-terminal portion of mammalian 58-kD sterol carrier protein (SCPx) and Escherichia coli acetyl-CoA acyltransferase: evidence for a gene fusion in SCPx.

A computer analysis of the amino acid sequences of rat and human 58-kD sterol carrier protein and Escherichia coli acetyl-CoA acyltransferase reveals that the two proteins have a segment of about 350 residues with strong sequence similarity. The ALIGN comparison scores for the rat and human sterol carrier proteins and the E. coli enzyme are 8.25 and 8.8 SD, respectively. The catalytically active cysteine of E. coli acetyl-CoA acyltransferase (cysteine 91) aligns with cysteine 93 and cysteine 94 on human and rat 58-kD sterol carrier protein, respectively.

Acetyl-CoA C-Acetyltransferase↗
PubMed1991

Bile duct diverticula and webs: nonspecific cholangiographic features of primary sclerosing cholangitis.

Biliary tree diverticula and webs are considered by several authors to be specific cholangiographic features of primary sclerosing cholangitis (PSC). Our experience suggested that these findings can be seen in patients without PSC. The purpose of this study was twofold: to establish whether diverticula and webs are indeed specific for PSC and to assess whether PSC can be accurately diagnosed without reference to diverticula or webs. We retrospectively reviewed 861 consecutive ERCP studies and found 32 cases of webs and/or diverticula. Using accepted cholangiographic, clinical, and histologic criteria, we diagnosed PSC in nine patients and excluded it in 21, with two instances of uncertain diagnoses. Webs and diverticula seen in PSC were cholangiographically indistinguishable from those in the group without PSC. All 21 patients without PSC had other biliary abnormalities, and were grouped by the predominant abnormality or finding believed to be associated with diverticulum or web formation: common duct stones or cholangitis (n = 11 patients), postoperative stricture (n = 4), bile duct stent and balloon dilatation (n = 3), malignant stricture (n = 2), and choledochoduodenostomy (n = 1). To assess cholangiographic diagnosis of PSC in these patients, a blinded reviewer studied the radiographs of the 30 patients with diverticula and/or webs who had confirmed diagnoses. By using established radiologic criteria alone (ignoring diverticula and webs), the correct diagnosis was made in 27, yielding a sensitivity of 89% and specificity of 91%. We conclude that the presence of diverticula and/or webs on a cholangiogram is a nonspecific finding and may be due to inflammation or trauma to the bile duct wall. Further, PSC can be distinguished from other abnormalities on the basis of findings other than diverticula and webs.

Bile Ducts↗
PubMed1990

Evolution of permease diversity and energy-coupling mechanisms with special reference to the bacterial phosphotransferase system.

Different classes of apparently unrelated permeases couple different forms of energy to solute transport. While the energy coupling mechanisms utilized by the different permease classes are clearly distinct, it is proposed, based on structural comparisons, that many of these permeases possess transmembrane, hydrophobic domains which are evolutionarily related. Carriers may have arisen from transmembrane pore-forming proteins, and the protein constituents or domains which are specifically responsible for energy coupling may have had distinct origins. Thus, complex permeases may possess mosaic structures. This suggestion is substantiated by recent findings regarding the evolutionary origins of the bacterial phosphoenolpyruvate-dependent phosphotransferase system (PTS). Mechanistic implications of this proposal are presented.

Biological Evolution↗
PubMed1990

A common ancestor for human placental 17 beta-hydroxysteroid dehydrogenase, Streptomyces coelicolor actIII protein, and Drosophila melanogaster alcohol dehydrogenase.

A computer-based comparison of the amino acid sequences of human placental 17 beta-hydroxysteroid dehydrogenase and Streptomyces coelicolor actIII protein, which is important in the synthesis of the antibiotic actinorhodin, gives an alignment score 12.15 standard deviations higher than that of 1000 comparisons of randomized sequences of these proteins. The probability of getting this score by chance is 3 x 10(-34). Comparison of actIII protein with Drosophila melanogaster alcohol dehydrogenase yields a score of 10.3 standard deviations (P = 3.5 x 10(-25)). Based on these similarities, we propose that 17 beta-hydroxysteroid dehydrogenase, actIII protein, and Drosophila alcohol dehydrogenase are derived from a common ancestor.

17-Hydroxysteroid Dehydrogenases↗
PubMed1990

Primary peritoneal neuroblastoma: computed tomography findings.

Primary peritoneal tumors are rare neoplasms. The computed tomography findings in an adult patient with a primary peritoneal neuroblastoma are described. Discussion of these uncommon neoplasms and this unusual presentation of neuroblastoma forms the basis of this report.

Adult↗
PubMed1990

A common ancestor for Candida tropicalis and dehydrogenases that synthesize antibiotics and steroids.

Candida tropicalis peroxisomes contain a 905-residue trifunctional enzyme with hydratase-dehydrogenase-epimerase activity that is important in fatty acid beta-oxidation. At its amino terminus are two tandem copies of an approximately 280 residue domain of unknown function. We provide evidence that this domain is homologous to oxidoreductases used for metabolizing sugars and synthesizing antibiotics and steroids such as estradiol, androstenedione, corticosterone, and hydrocortisone. The trifunctional enzyme shows no sequence similarity to the bifunctional hydratase-dehydrogenase found in animal peroxisomes and plant glyoxysomes, which are homologs of each other. We suggest that the C. tropicalis trifunctional enzyme and the animal and plant bifunctional enzymes have different ancestors.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1990

Extravasation of nonionic radiologic contrast media: efficacy of conservative treatment.

The authors report four large-volume (greater than 20-mL) extravasations in adults and one intermediate-volume (18-mL) extravasation in an infant of iopamidol, a nonionic contrast medium, that occurred during dynamic enhanced computed tomography. The largest volume that extravasated (in two patients) was 150 mL. Although all five patients initially had swelling, erythema, and/or pain after extravasation, all recovered uneventfully. The authors suggest that emergent surgical drainage of all large-volume extravasations, a procedure that was recently recommended, is unnecessary. Large extravascular collections of nonionic contrast media can be well tolerated and are often resorbed without adverse sequelae.

Aged↗