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Biomedical subjects

B Martin

Publications and source records attributed to B Martin.

At least 343 records · Page 19Linked to original sources
PubMed1986

Beta-elimination of indole from L-tryptophan catalyzed by bacterial tryptophan synthase: a comparison between reactions catalyzed by tryptophanase and tryptophan synthase.

Although tryptophan synthase catalyzes a number of pyridoxal phosphate dependent beta-elimination and beta-replacement reactions that are also catalyzed by tryptophanase, a principal and puzzling difference between the two enzymes lies in the apparent inability of tryptophan synthase to catalyze beta-elimination of indole from L-tryptophan. We now demonstrate for the first time that the beta 2 subunit and the alpha 2 beta 2 complex of tryptophan synthase from Escherichia coli and from Salmonella typhimurium do catalyze a slow beta-elimination reaction with L-tryptophan to produce indole, pyruvate, and ammonia. The rate of the reaction is about 10-fold higher in the presence of the alpha subunit. The rate of indole production is increased about 4-fold when the aminoacrylate produced is converted to S-(hydroxyethyl)-L-cysteine by a coupled beta-replacement reaction with beta-mercaptoethanol. The rate of L-tryptophan cleavage is also increased when the indole produced is removed by extraction with toluene or by condensation with D-glyceraldehyde 3-phosphate to form indole-3-glycerol phosphate in a reaction catalyzed by the alpha subunit of tryptophan synthase. The amount of L-tryptophan cleavage is greatest in the presence of both beta-mercaptoethanol and D-glyceraldehyde 3-phosphate, which cause the removal of both products of cleavage. The cleavage reaction is not due to contaminating tryptophanase since the activity is not inhibited by (3R)-2,3-dihydro-L-tryptophan, a specific inhibitor of tryptophanase, but is inhibited by (3S)-2,3-dihydro-L-tryptophan, a specific inhibitor of tryptophan synthase. The cleavage reaction is also inhibited by D-tryptophan, the product of a slow racemization reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Escherichia coli↗
PubMed1986

Definition of human cytomegalovirus-specific target antigens recognized by cytotoxic T cells generated in vitro by using an autologous lymphocyte system.

We developed an in vitro system for the generation of human cytomegalovirus (CMV)-specific cytotoxic T cells (CTL) that avoids the necessity of constituting a panel of HLA-typed fibroblasts. Autologous donor leucocytes were coated with CMV antigens and were used as both stimulator and target cells. With the use of this system, CMV-specific effector cells were efficiently generated from seropositive but not seronegative donors. These CMV-specific effectors were HLA-restricted and had characteristics of T cells. Maximum lymphoproliferation preceded the appearance of maximum CTL activity by 3 to 4 days, and a close correlation was seen between both activities. Mouse anti-CMV monoclonal antibodies were used in blocking experiments in an attempt to define target antigens recognized by CMV-specific cytotoxic lymphocytes. Monoclonal antibodies directed against an early CMV membrane antigen, against neutralization epitopes, or against nuclear inclusion body protein all specifically inhibited CMV-sensitized effector cell activity but did not affect influenza virus-specific lysis. Monoclonal antibodies directed against a normal cell determinant or against poliovirus did not affect CMV-specific CTL activity. CMV-immune cytotoxic T cells could be consistently and specifically inhibited in their lytic activity by pretreating antigen-coated target cells with monoclonal antibodies directed against CMV-related proteins.

Adolescent↗
PubMed1986

[Does arterial embolization have a role in the treatment of cavernous hemangioma of the liver in adults?].

Embolization of the hepatic artery for cavernous haemangioma is discussed on the basis of 7 cases (3 giant haemangiomas, 4 medium sized or small), all symptomatic. Therapeutic embolization reduced the tumoral mass in 3 cases but had little effect on the symptoms. There was no complication. Arterial embolization is a relatively non-aggressive method, but it does not suppress the lesion. It should therefore be reserved to symptomatic or complicated cases, where reduction of the mass can be expected to result in functional improvement. Such cases are too exceptional for embolization to be performed routinely in adult patients with cavernous haemangioma of the liver.

Adult↗
PubMed1986

A two-year double-blind crossover trial of the prophylactic effect of methylene blue in manic-depressive psychosis.

A 2-year prophylactic trial was carried out in 31 bipolar manic-depressive subjects, comparing 300 mg/day methylene blue on a double-blind crossover basis with 15 mg/day. All patients were also maintained on lithium. Seventeen patients completed the 2-year trial. During the year the patients were treated with methylene blue at 300 mg/day, they were significantly less depressed than during the year on 15 mg/day. No significant difference in the severity of manic symptoms was shown. The trial had obvious limitations, e.g., a small number of subjects, a relatively large number of dropouts, relatively simple rating scales, doubts about blindness, and uncertainty as to whether or not 15 mg methylene blue per day could be considered a placebo. However, the results suggest that methylene blue may be a useful addition to lithium in the long-term treatment of manic-depressive psychosis and warrants further investigation.

Bipolar Disorder↗
PubMed1986

Apoprotein D in a healthy, male population and in male myocardial infarction patients and their male, first-degree relatives.

This report examines the correlation of serum apoprotein D with other lipoprotein lipids and apoproteins in a healthy, male population and compares the levels of high density lipoprotein apoprotein D of this control population with 2 samples composed of male, acute myocardial infarction patients and their healthy, male, first-degree relatives. Highly significant correlations were observed with very low density lipoprotein lipids (negative), high density lipoprotein lipids (positive) and serum triglycerides (negative). Serum and low density lipoprotein apoprotein B was not correlated with serum apoprotein D, whereas apoprotein A-I from serum and high density lipoproteins was strongly correlated with apoprotein D. A significant reduction in high density lipoprotein apoprotein D was observed in male, myocardial infarction patients. Their male, first-degree relatives also had lower apoprotein D levels, but the difference was not significant.

Adult↗
PubMed1986

Reduced levels of histidine and urocanic acid in suction blister fluids from patients with psoriasis.

Metabolites of histidine were determined by high performance liquid chromatography in suction blister fluids from lesions and normal appearing skin of patients with psoriasis and from healthy subjects. There was a significant decrease in the levels of histidine and urocanic acid in the samples obtained from patients with psoriasis as compared to healthy subjects. Virtually only the E-isomer of urocanic acid was detected.

Adult↗
PubMed1986

Purification and partial characterization of human intracellular B cell growth factor.

In the present report a protocol for the purification of an intracellular protein, exhibiting BCGF activity has been described. This protein is obtained from lectin stimulated human peripheral blood mononuclear cells and has been previously shown to be present only in the cytosolic extract of normal human T-lymphocytes. The isoelectric point (pI) of the purified protein is 6.3, as determined by both sucrose gradient isoelectric focusing and chromatofocusing. The molecular weight of the chromatofocused protein, determined by SDS-PAGE, is 60 kD. Thirty-three percent of the BCGF activity contained in the initial crude extract is recovered as a homogenously purified protein, with an estimated specific activity of 10(5) U/mg.

B-Lymphocytes↗
PubMed1986

Antibiotic disposition in experimental pneumonic pasteurellosis: gentamicin and tylosin.

The effects of severe respiratory disease on the disposition of antibiotics were evaluated using two drugs chosen because of their widely differing solubility characteristics. The experiments were carried out in series, using five calves for each drug. The drugs were given to seven week old calves before and after induction of pneumonia by bilateral intrapulmonary administration of 3 mL of 5 X 10(7) colony forming units of Pasteurella haemolytica. Following inoculation, the calves developed clinical signs of pneumonia and were given gentamicin (5 mg/kg) or tylosin (10 mg/kg) 48, 60 and 72 hours after Pasteurella administration. There was a statistically significant decrease in distribution rate but not elimination rate of gentamicin. For tylosin, there was a significant increase in elimination rate. These results indicate the kinetics of tylosin but not gentamicin are sufficiently altered as to support a need for increased frequency of administration with severe respiratory disease in calves.

Animals↗
PubMed1985

Use of fluorinated tyrosine phosphates to probe the substrate specificity of the low molecular weight phosphatase activity of calcineurin.

Calcineurin, a calmodulin-activated protein phosphatase, is known to dephosphorylate certain low molecular weight phosphate esters. The low molecular weight phosphatase activity of calcineurin has been studied by utilizing tyrosine phosphate derivatives. Kinetic studies suggest that the substrate specificity is dependent upon the electronic nature of the substrate in contrast to results obtained with alkaline phosphatase from Escherichia coli. Comparison of calcineurin and acid-catalyzed hydrolyses indicates a 1:1 correlation between the rate constants for the two processes. This correlation and other model studies have been utilized to provide insight into the chemical mechanism of calcineurin. Possible chemical mechanisms for calcineurin are discussed.

Alkaline Phosphatase↗
PubMed1985

Characterization of a mutation conferring radiation sensitivity, ior, located close to the gene coding for deoxycytidine deaminase in Escherichia coli.

The isolation and characterization of a new mutation conferring radiation sensitivity in Escherichia coli is described. This mutation is located close to the gene coding for deoxycytidine deaminase, in the chromosomal region of the gat operon. It is very sensitive to gamma rays and exhibits a decrease in recombination ability. The expression of radiation sensitivity seems to result from the additive effect of the dcd mutation and another mutation of unknown function.

Cytidine Deaminase↗
PubMed1985

The hexB mismatch repair gene of Streptococcus pneumoniae: characterisation, cloning and identification of the product.

A second gene involved in mismatch repair in Streptococcus pneumoniae, the hexB gene, has been characterised. The gene was cloned into a multicopy plasmid vector. The cloned hexB gene is expressed as judged by its ability to complement a chromosomal hexB- allele. Its direction of transcription and its functional limits were defined. Comparison of the proteins encoded by recombinant plasmids and by restriction fragments allowed us to identify an Mr 83,000 protein as the probable product of the hexB gene. We offer evidence that this gene together with the hexA gene is essential for repair of transition as well as frameshift mismatches.

Alleles↗
PubMed1985

Abnormal cerebrospinal fluid protein indices in schizophrenia.

Determinations of albumin and immunoglobulin G (IgG) were performed in paired cerebrospinal fluid (CSF) and serum samples from 24 subjects with schizophrenia. These determinations allowed calculation of two indices, one that is an indicator of integrity of the blood-brain barrier and the other a measure of selective IgG production within the central nervous system (CNS). In comparison with previously determined reference values, 7 of 24 (29%) subjects showed increased blood-brain barrier permeability, and 8 of 24 (33%) demonstrated elevated endogenous CNS IgG production. One of these eight also demonstrated oligoclonal banding on high-resolution protein electrophoresis of the CSF.

Adolescent↗
PubMed1985

Alpha-fetoprotein expression in intra- and extraembryonic fluids of developing chick embryo.

The ontogeny of alpha-fetoprotein (AFP) has been studied in the chicken (from 7 days of incubation until 2 days after hatching) using (1) the two-dimensional immunoelectrophoresis technique, (2) the polyacrylamide gel electrophoresis, and (3) the high resolution two-dimensional polyacrylamide gel electrophoresis. The molecular weight of AFP was estimated at 71,000. AFP was seen as a heterogeneous population composed of four isoforms which slightly differ by their isoelectric points. Up to the 18th day of development, qualitative changes in AFP heterogeneity do not occur. Only traces of the two alkaline isoforms were observed in plasma of 2 days post-hatching chickens. AFP has been identified in allantoic and cerebrospinal fluids but is not present in amniotic fluid. At 7 days of embryonic age, all the plasma AFP species are present in cerebrospinal fluid.

Allantois↗