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Biomedical subjects

R Greenberg

Publications and source records attributed to R Greenberg.

At least 163 records · Page 9Linked to original sources
PubMed1981

Effectiveness of federally required medical laboratory screening in the detection of chemical liver injury.

The increasing concern of industrialized societies over the potential health hazard of synthetic chemicals in the occupational environment has led to government requirements for medical laboratory screening of workers. The specific tests for such screening programs are most often selected on the basis of medical experience which utilized them in symptomatic or hospitalized populations. Required screening tests for hepatic injury including cancer in vinyl chloride workers has been systematically and prospectively studied in an industrial population working with synthetic rubber and plastics. Approximately 1300 employees were studied over a five-year period. A cohort of 969 male employees, for the purposes of analysis, were divided into a "standard" and "nonstandard" population based upon the absence or presence of significant medical disease (including liver disease). A subcohort of 120 individuals was further identified based on availabiliity of liver biopsy. Evaluation of federally required studies included alkaline phosphatase (AP), gamma-glutamyl transpeptidase (GGTP), alanine aminotranserase (ALT, SGPT), aspartic aminotransferase (AST, SGOT) and bilirubin (BR). Also studied were indocyanine green clearance (ICG) and radioisotopic liver spleen scans (L-S scans). The GGTP provided the highest positive predicted value as a screening test for identifying "nonstandard" individuals (individuals with all types of medical disease) followed by ICG, AST, ALT, L-S scan, AP, and BR. In the identification of asymptomatic liver disease the GGTP had the least specificity due to a high false positive rate, while the AP provided the highest specificity. The ICG clearance however, provided the best combination of positive predictive value and sum of specificity and sensitivity. The AP provided additional increase in specificity as a follow-up study. There was no evidence that any of the other federally required tests added any additional benefit and did add significant increase in the false positive rate. These studies support the need for evaluating screening tests as to their sensitivity, specificity and positive predictive value, in asymptomatic individuals, before they are made established requirements.

Adolescent↗
PubMed1980

Isolation and chracterization of m5U-methyltransferase from Escherichia coli.

The tRNA-modifying enzyme, S-adenosylmethionine: tRNA (uridine-5)-methyltransferase, has been purified essentially to homogeneity from an Escherichia coli strain containing an elevated level of this enzyme. A rapid, efficient method has been developed for the purification, consisting of polyethyleneimine precipitation to remove nucleic acids, followed by phosphocellulose and Blue Sepharose affinity chromatography. The enzyme is a single polypeptide chain of molecular weight 42,000. It has a pH optimum of 8.4, a Km of 12.5 microM for S-adenyosyl-L-methionine, and a Km of 1.1 microM for wheat germ tRNAGly1. The ability of the enzyme to methylate a variety of tRNA substrates including prokaryotic, eukaryotic, mitochondrial, and chloroplastic tRNAs has been characterized.

Escherichia coli↗
PubMed1980

Base composition of transfer RNAs from vegetative and developing cells of Dictyostelium discoideum.

In a previous comparison of tRNAs from vegetative and developing cells of Dictyostelium discoideum, displacements of chromatographic peaks were observed for a number of aminoacyl-tRNAs (Palatnik, C.M., Katz, E.R. and Brenner, M. (1977) J. Biol. Chem. 252, 694-703). Since the development peak eluted ahead of the vegetative peak in all but one case, and since levels of amino acid acceptance and tRNA chromatographic profiles were otherwise quite similar, it was suggested that a common change or a very small number of changes in base modification were occurring during development. We have threfore compared tRNAs from both stages with respect particularly to their minor base composition. Of the minor bases which we have analyzed no reproducible differences between the two stages have been detected. Moreover, we have been unable to confirm a recent report (Dingermann, T., Schmidt, W. and Kersten, H. (1977) FEBS Lett. 80, 205-208) that a significant change occurs in the ribothymidine content of tRNA during Dictyostelium discoideum development.

Base Composition↗
PubMed1979

The effects of captopril (SQ 14,225) on bradykinin-induced bronchoconstriction in the anesthetized guinea pig.

The effect of captopril (SQ 14,225) a potent inhibitor of angiotensin converting enzyme (ACE: kininase II) on the bronchoconstrictor response to bradykinin was studied in the anesthetized guinea pig. The i.v. administration of captopril caused a profound long lasting hypotension without affecting pulmonary resistance or dynamic compliance. Similarly, the i.v. administration of bradykinin caused small increases in pulmonary resistance and decreases in dynamic compliance which were not altered by the administration of captopril. However, after beta-receptor blockade with propranolol, bradykinin-induced changes in resistance and compliance were enhanced; additional captopril administration further potentiated the bradykinin effects. The prostaglandin synthetase inhibitor indomethacin antagonized the bradykinin-induced bronchoconstriction in beta-blocked animals and its potentiation by captopril. In the isolated perfused guinea pig lung, bradykinin caused a dose dependent release of a prostaglandin-like substance which was significantly increased by captopril and antagonized by indomethacin. These results suggest that bradykinin causes a prostaglandin-mediated bronchoconstriction. Captopril, a potent inhibitor of ACE, prevents the degradation of bradykinin thus potentiating the bradykinin-induced bronchoconstriction, an effect observed in intact animals only in the absence of pulmonary beta-receptor activation.

Airway Resistance↗
PubMed1979

Human beta-casein.

Human beta-casein occurs in multiphosphorylated forms having the same amino acid composition but with 0-5 phosphate groups/molecule. Sequence analysis was used to determine whether each of the phosphorylated forms is a mixture of species having a certain number of phosphate groups randomly distributed or whether each form contains phosphate groups on specific seryl or threonyl residues. It was found that forms containing 2, 4 and 5 phosphate groups/molecule are homogeneous with respect to their phosphorylation sites. The monophosphorylated form, however, is a mixture of equal amounts of species phosphorylated at residues 9 or 10.

Amino Acid Sequence↗