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Biomedical subjects

M L Taylor

Publications and source records attributed to M L Taylor.

At least 109 records · Page 6Linked to original sources
PubMed1977

[Immunology of histoplasmosis: isolation of a polysaccharide-protein complex with immuno-specific activity from Histoplasma capsulatum].

A polysaccharide protein complex (PPC) with a high specificity in immunodiffusion in gel (IDG) was isolated from a Histoplasma capsulatum strain. Although unaffected by proteolytic enzymes (pronase) and heat, the PPC antigen activity was destroyed by beta-glucosidase. These results suggest that the specificity of the PPC antigen might be located in the polysaccharide fraction. Polyacrylamide gel electrophoresis of the PPC antigen gave only one brand detected by Schiff's reagent (PAS).

Animals↗
PubMed1976

Left ventricular performance in coronary artery disease evaluated with systolic time intervals and echocardiography.

Simultaneous determinations of systolic time intervals (preejection period index [PEPI], left ventricular ejection time index [LVETI] and ratio of preejection period to left ventricular ejection time [PEP/LVET]) and echographic measures of left ventricular performance (percent change in minor axis diameter [%delta D], circumferential shortening rate [Vcf] and end-diastolic diameter [Dd]) were obtained in 25 normal subjects and 37 patients with previously documented transmural myocardial infarction. The group with previous infarction demonstrated significant (P less than 0.001) differences from the normal group in each of the noninvasive measures. PEP/LVET and %deltaD were the most sensitive measures of left ventricular dysfunction. Deviation from the normal range in these measures occurred, respectively, in 70 and 65 percent of patients without dyspnea or fatigability (20 patients) and 85 percent of those without angina pectoris (13 patients). Abnormalities in systolic time interval and echocardiographic measures were related to the severity of dyspnea and fatigability but not to that of angina. Neither the presence of phonocardiographically documented third or fourth sound gallops nor an abnormal cardiothoracic ratio by chest roentgenogram reliably detected patients with abnormal left ventricular performance. The range of abnormality in left ventricular performance did not differ between patients with prior anterior or diaphragmatic myocardial infarction. The frequency of abnormal performance was greatest among patients with combined sites of prior infarction. Among 26 patients studied by coronary arteriography, abnormal left ventricular performance as determined by values for PEP/LVET and %deltaD occurred in fewer than 30 percent of those with 70 percent or greater obstruction of one coronary artery and in more than 80 percent of those with two or three vessel involvement. There was a high correlation between systolic time intervals, %delta D and Vcf, the closest correlation occurring between PEP/LVET and %deltaD (r = -0.93). These data document the sensitivity of the noninvasive systolic time intervals and echographic measures and their superiority over current clinical bedside methods in evaluating left ventricular performance in patients with prior myocardial infarction.

Adult↗
PubMed1976

Oxidation of arsenite to arsenate by Alcaligenes faecalis.

Alcaligenes faecalis, resistant to the toxic effects of 0.01 M sodium arsenite, was isolated from raw sewage and shown to be capable of oxidizing arsenite to arsenate. When the organisms were grown in chemically defined medium, this conversion was due to the appearance at stationary phase of an intracellular, oxygen-sensitive, inducible enzyme and/or component of the electron transport system; when the organisms were grown in a nutrient broth-yeast extract medium, the enzyme appeared in the late exponential phase of growth. The presence of 0.02 M arsenite in the culture medium affected neither growth rate nor final cell yield.

2,6-Dichloroindophenol↗
PubMed1976

Purification of properties of dihydroorotase, a zinc-containing metalloenzyme in Clostridium oroticum.

Dihydroorotase +4,5-L-dihydro-orotate amidohydrolase [EC 3.5.2.3]), which catalyzes the reversible cyclization of N-carbamyl-L-aspartate to L-dihydroorotate, has been purified from orotate-grown Clostridium oroticum. The enzyme is homogeneous when subjected to polyacrylamide gel electrophoresis and is stable at pH 7.6 in 0.3 M NaCl containing 10 muM ZnSO4. The enzyme has a molecular weight of approximately 110,000. Sodium dodecyl sulfate gel electrophoresis, using three different buffer systems, indicated the enzyme is composed of two subunits, each having a molecular weight of 55,000. Dihydroorotase is shown by atomic absorption spectroscopy to be a zinc-containing metalloenzyme with 4 g-atoms of zinc per 110,000 g of protein. The pH optima for the conversion of N-carbamyl-L-aspartate to L-dihydroorotate and for L-dihydroorotate to N-carbamyl-L-aspartate are pH 6.0 and 8.2, respectively. The Km values for N-carbamyl-L-aspartate and for L-dihydroorotate are 0.13 and 0.07 mM, respectively. Inhibitor studies indicate that zinc may be involved in the catalytic activity of the enzyme.

Amidohydrolases↗
PubMed1976

Left ventricular performance in coronary artery disease by systolic time intervals and echocardiography.

Determinations of systolic time intervals and echocardiographic measures of left ventricular performance were made in twenty-five normal subjects and 37 patients who had convalesced from a previous transmural myocardial infarction. On group analysis the patients with previous myocardial infarction demonstrated significant differences from the normals in each of the noninvasive measures. Among the noninvasive measures the PEP/LVET and deltaD% proved to be the most sensitive indicators of left ventricular dysfunction. Deviations from the normal range in PEP/LVET and deltaD% occurred in 65% to 70% of patients asymptomatic for dyspnea and fatigability (20 patients) and in 85% of patients asymptomatic for angina pectoris (13 patients). Neither the presence of phonocardiographically documented S3 or S4 or the finding of an abnormal C/T ratio on standard chest x-ray reliably detected patients with abnormal left ventricular performance. Among 26 patients studied by coronary arteriography, abnormal left ventricular performance by PEP/LVET and deltaD% occurred in less than 30% of those with obstruction (70% or greater) of one coronary artery and in over 80% of those with obstruction of two or three major arteries. A close correlation existed between the level of left ventricular performance measured by the PEP/LVET and the deltaD% (r = 0.93). These studies document the high degree of sensitivity of the noninvasive measures and demonstrate their superiority over clinical methods for detecting abnormal left ventricular performance in patients with previous myocardial infarction.

Echocardiography↗
PubMed1974

Biosynthetic dihydroorotate dehydrogenase from Lactobacillus bulgaricus: partial characterization of the enzyme.

Some of the catalytic properties of the biosynthetic dihydroorotate dehydrogenase purified from an anaerobic bacterium, Lactobacillus bulgaricus, are described. Studies with p-hydroxymercuribenzoate, N-ethylmaleimide, and mercuric chloride showed that sulfhydryl groups are necessary for transfer of electrons from dihydroorotate to a variety of electron acceptors. Protection studies with substrates for the enzyme indicated that free sulfhydryl groups at or near the active center are required for catalytic activity. Evidence is presented for the production of superoxide free radicals during reaction of the enzyme with molecular oxygen. Inhibitor studies with Tiron indicated that reduction of cytochrome c by the enzyme may involve the superoxide free radical as an intermediate. Orotate, one of the substrates for the enzyme, has been found to be a competitive inhibitor for the dihydroorotate site. The K(i) for orotate as estimated by several techniques is 0.1 mM. The K(m) for dihydroorotate with ferricyanide as the electron acceptor is estimated to be 0.5 mM.

Anaerobiosis↗
PubMed1971

Biosynthetic dihydroorotate dehydrogenase from Lactobacillus bulgaricus.

This paper describes the first detailed study on a dihydroorotate dehydrogenase involved in pyrimidine biosynthesis. In most organisms the enzyme is membrane-bound; however, a soluble dihydroorotate dehydrogenase was produced in relatively high levels when the anaerobe, Lactobacillus bulgaricus, was released from repression. The enzyme was purified 213-fold over derepressed levels with a 39% recovery of enzyme units. The enzyme showed only one minor protein contaminant when analyzed by polyacrylamide electrophoresis. It was characterized as a flavoprotein containing only flavine mononucleotide as the prosthetic group. Molecular weight estimations by gel filtration gave a value of approximately 55,000, which is one-half that of the degradative enzyme described by others. During aerobic oxidation of dihydroorotate, the rates of oxygen consumption, orotate formation, and hydrogen peroxide formation were equal, as would be expected in a flavoprotein-catalyzed reaction. The enzymatic activity with ferricyanide as acceptor was optimum around pH 7.7. The stimulation of enzymatic activity over a wide pH range by ammonium sulfate was attributed to an effect on the maximum velocity of the reaction. As analyzed by polyacrylamide electrophoresis, inactivation of the enzyme by visible light resulted in the appearance of a second protein band with lowered specific activity. The purified enzyme used redox dyes, oxygen, or cytochrome c as electron acceptors but was not active with pyridine nucleotides. Flavine adenine dinucleotide has been implicated at the active site for pyridine nucleotide reduction in the degradative enzyme. The biosynthetic enzyme lacks this flavine and the associated activity.

Acrylates↗
PubMed1966

Two functionally different dihydroorotic dehydrogenases in bacteria.

Taylor, W. H. (Portland State College, Portland, Ore.), M. L. Taylor, and D. F. Eames. Two functionally different dihydroorotic dehydrogenases in bacteria. J. Bacteriol. 91:2251-2256. 1966.-We have investigated the relationship between the two kinds of dihydroorotic dehydrogenases produced by bacteria. A pseudomonad, capable of growth on a salts medium with glucose, aspartate, glycerol, or orotate as the carbon source, was isolated from lake bank mud. A particle-bound dihydroorotic dehydrogenase, similar to the biosynthetic enzyme in Escherichia coli, was formed by the pseudomonad when the carbon source was orotate, glucose, glycerol, or aspartate. A soluble, degradative nicotinamide adenine dinucleotide phosphate-linked dihydroorotic dehydrogenase, as well as the particle-bound biosynthetic enzyme, was formed when the pseudomonad was cultivated on orotate. The biosynthetic enzyme links to oxygen or ferricyanide, but not to pyridine nucleotides. Zymobacterium oroticum, when cultivated on glucose, contained only the biosynthetic type of dihydroorotic dehydrogenase. The presence of two functionally different dihydroorotic dehydrogenases in the pseudomonad was suggested on the basis of the following observations: (i) the two enzyme activities were separated by centrifugation; (ii) the pyridine nucleotide-linked activity was formed only when orotate was present in the growth medium; and (iii) the biosynthetic enzyme was stable to storage at -20 C for 4 months, whereas the degradative enzyme activity was destroyed by storage under these conditions.

Aspartic Acid↗
PubMedDate not supplied

Relationship between pathogenesis and immune regulation mechanisms in histoplasmosis: a hypothetical approach.

The cellular immune response may be the principal mechanism of defense against infection with Histoplasma capsulatum. Subsequently, regulation of cell-mediated immunity could be fundamental to the outcome of disease. Suppressive phenomena-present in the host before infection or brought about by fungal components-would explain the various courses of infection. The fact that high titers of antibodies are associated with a poor cellular response suggests that antibodies may have a role as "regulatory molecules" in histoplasmosis. Antibodies may modulate the expression of the cellular response either by direct inhibition or by activation of the suppressor cell population, thereby interfering with the infectious process.

Animals↗
PubMedDate not supplied

Efficiency of crude and purified fungal antigens in serodiagnosis to discriminate mycotic from other respiratory diseases.

Mycotic immunodiagnosis was performed in 186 hospitalized patients with different respiratory diseases, mostly considered as tuberculosis and others with a doubtful diagnosis. Crude histoplasmin, coccidioidin, paracoccidioidin, blastomycin, candidin, aspergillin, and sporotrichin, as well as purified polysaccharide-protein complexes (PPC) of Histoplasma capsulatum, Coccidioides immitis, and Paracoccidioides brasiliensis were used as antigens. Immune tests used included skin test (ST), gel immunodiffusion (ID), counterimmunoelectrophoresis (CIE), complement fixation (CF), and ELISA. A possible association with candidosis was observed in 17% of patients with tuberculosis and diabetes; one presumptive paracoccidioidomycosis, one confirmed aspergillosis, and six cases of active histoplasmosis were determined. Candidin ST showed 29% of positive reactions with an increased frequency in patients between 31 and 55 years of age. CF test showed the highest positivity percentages with crude antigens, specially for Candida antigen (26.3%) and histoplasmin (18.2%). Cross reactions were evident with crude antigens but decreased when PPC's were used in ELISA.

Adolescent↗
PubMedDate not supplied

Retrospective serological study of histoplasmosis in Mexico.

Mycotic immunodiagnosis was performed in 325 patients with clinical evidence of systemic mycoses, over a 5-year period, from different hospitals of Mexico City. Results showed 168 individuals that presented one positive serological test to Histoplasma capsulatum antigens. From these, only 27 patients were serologically positive to two or more tests, such as tube precipitin, immunodiffusion, complement fixation, and ELISA, and developed signs and symptoms of a histoplasmosis clinically classified as primary pulmonary. Four of them presented an underlying disease including one positive HIV patient. Twenty-two came from endemic histoplasmosis zones of the country and most of them acquired the disease in caves or uninhabited houses. The diagnosis of histoplasmosis should be based on reliable laboratory data which could raise more significant information of its incidence in Mexico.

Adolescent↗