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Biomedical subjects

C Roy

Publications and source records attributed to C Roy.

At least 235 records · Page 13Linked to original sources
PubMed1985

Sandhoff disease heterozygote detection: a component of population screening for Tay-Sachs disease carriers. I. Statistical methods.

Serum and leukocyte hexosaminidase profiles (total activity and percent heat-labile activity levels) in obligate Sandhoff disease (SHD) heterozygotes differ from those of obligate Tay-Sachs disease (TSD) heterozygotes and noncarrier individuals. We have developed a procedure to identify, with 95% sensitivity, carriers of the allele(s) for SHD among individuals screened in a TSD heterozygote identification program. Using multivariate statistical methods of cluster analysis and discriminant analysis on serum and leukocyte hexosaminidase profiles from 102 potential SHD carriers, a linear discriminant function to classify individuals as SHD carriers or SHD noncarriers was constructed. This function classifies the serum and leukocyte profiles from all 15 obligate SHD heterozygotes studied, as those of SHD carriers. A 95% isodensity ellipse derived from only the serum hexosaminidase profiles of the 15 SHD obligate carriers has been applied to a TSD screened sample of 37,843 Jewish and non-Jewish individuals. A potential recall rate of screened individuals for serum retests and leukocyte assays of 2.01% has been estimated. These statistical methods enhance the TSD heterozygote screening program by permitting one to detect SHD heterozygotes within the screened population.

Genetic Carrier Screening↗
PubMed1984

Regulation by adenosine of the vasopressin-sensitive adenylate cyclase in pig-kidney cells (LLC-PK1L) grown in defined media.

LLC-PK1L cells, a kidney-derived cell line, had sustained growth in a defined medium. When compared to the parent cell line growing with 10% fetal bovine serum, LLC-PK1L cells had about 100-times fewer vasopressin receptors. Upon modifications of the cell culture medium, the vasopressin response of the adenylate cyclase could be increased by more than 10-fold with a parallel increase in vasopressin receptor number. Using cells with high or low receptor densities, the stimulatory and inhibitory effects of N6-L-2-phenylisopropyl-adenosine on the modulation of the adenylate cyclase responsiveness to vasopressin were investigated. When high concentrations of GTP were added, low concentrations of phenylisopropyladenosine inhibited the enzyme, while higher concentrations were found to be stimulatory. The adenylate cyclase activity stimulated by vasopressin could only be inhibited by phenylisopropyladenosine under these conditions in membranes with high receptor density; only the increase in enzyme activity due to high GTP concentration was inhibitable. The analysis of the dependency of the adenylate cyclase activity as a function of the vasopressin concentration showed that, besides reducing the maximum velocity of the system for vasopressin, the addition of phenylisopropyladenosine generated an heterogeneity in the adenylate cyclase response to vasopressin (as judged by a curvilinear Eadie plot). A high-affinity component in the adenylate cyclase response appeared when phenylisopropyladenosine was added. The growth of the cells in a medium containing adenosine deaminase gave results identical to those obtained for control cells. However, growing the cells with both phenylisopropyladenosine and adenosine deaminase abolished the inhibitory effects of the former on the adenylate cyclase and greatly reduced its stimulatory action. Under these conditions, the vasopressin response of the adenylate cyclase was not further regulated by phenylisopropyladenosine. These results indicate a role of adenosine on vasopressin response, especially at low physiological concentrations of the hormone where a high-affinity component of the hormonal response could be demonstrated.

Adenosine↗
PubMed1984

Inhibition by somatostatin of the vasopressin-stimulated adenylate cyclase in a kidney-derived line of cells grown in defined medium.

LLC-PK1L cells, a kidney-derived cell line grown in defined medium, possess a vasopressin-sensitive adenylate cyclase. Somatostatin was able to inhibit the vasopressin-induced increase in adenylate cyclase activity, without affecting the basal enzyme activity. This inhibition was competitive. No effect of somatostatin could be detected on [3H]vasopressin binding suggesting an interaction of somatostatin with the vasopressin-sensitive system distal to the hormone-receptor interaction. At variance with N6-L-2-phenylisopropyladenosine (PIA), GTP did not potentiate the inhibition by somatostatin. The inhibition of the vasopressin stimulation by somatostatin and that by PIA were additive. Changing the composition of the cell growth medium increased the number of vasopressin receptors per cell. Cells with a high number of vasopressin receptors were less sensitive to inhibition by somatostatin. Such results suggested that somatostatin and vasopressin receptors and/or the inhibitory (Ni) and stimulatory (Ns) regulatory transducing components are regulated by different mechanisms.

Adenylyl Cyclases↗
PubMed1984

The 5S RNA binding protein from yeast (Saccharomyces cerevisiae) ribosomes. An RNA binding sequence in the carboxyl-terminal region.

The carboxyl-terminal half (CN2 fragment) of the yeast 5S RNA binding protein (YL3) retains an ability to form homogeneous ribonucleoprotein complexes with RNA although the N-terminal half (CN1) appears to confer specificity for the 5S RNA molecule [Nazar, R.N., Yaguchi, M., Willick, G.E., Rollin, C.F. and Roy, C. (1979) Eur. J. Biochem. 102, 573-582]. The nucleic acid binding site in this fragment was more clearly delineated by cleaving the CN2 fragment with a variety of enzymatic and chemical reagents and further examining the ability of the products to form RNA-peptide complexes. Hot acetic acid treatment produced a 47-residue subfragment (CN2-A1) which originated from the C terminus and continued to form stable ribonucleopeptide complexes. The amino acid sequence of this subfragment was determined to be: -Pro-Ala-Phe-Lys-Pro-Thr-Glu-Lys50-Phe-Thr-Lys-Glu-Gln-Tyr-Ala-Ala -Glu60-Ser-Ly s -Lys-Tyr-Arg-Gln-Thr-Lys-Leu-Ser70-Lys-Gln-Gln-Arg-Ala-Ala-Arg-Val -Ala-Ala80-Ly s -Ile-Ala-Ala-Leu-Ala-Gly-Gln-Gln-COOH, with 12 of the 16 basic residues in the CN2 fragment being present in this binding site. The amino acid sequence of the CN2-A1 fragment bears a limited homology in both amino acid and charge distribution with histone 2B from mammals and with one of the 5S RNA binding proteins (EL25) from Escherichia coli. The results suggest that many protein binding sites for nucleic acids may share common structural features and further support the notion that the single large eukaryotic 5S RNA protein may have evolved through a fusion of genes for the multiple 5S RNA binding proteins in prokaryotes.

Amino Acid Sequence↗
PubMed1984

Fluid composition of basolateral space of kidney cells in culture and its modification by intracellular cAMP.

LLC-PK1 kidney cells, like other epithelial cells, form domes due to Na+ and water movements from the apical to the basolateral side of the epithelium when cultured on a nonpermeable support. The composition of the fluid trapped under these domes can therefore be considered to reflect the nature of the fluid reabsorbed through the epithelium. Collecting the basolateral fluid by micropuncture and analyzing it by electron microprobe revealed that it was isosmotic with the external medium and that the concentrations of Na+, Cl-, Ca2+, Mg2+, and phosphate were nearly the same in both. In contrast, the K+ concentration was found to be 40% lower under the domes than in the bath. Changing the osmolality of the apical medium showed that the epithelium was leaky for water, although it maintained an ionic gradient for at least 20 min. Fifteen minutes after addition of dibutyryl adenosine 3',5'-cyclic monophosphate or 3-isobutyl-1-methylxanthine (5 X 10(-4) M) to the external medium, the phosphate concentration in the basolateral fluid was increased. This rise peaked at 1 h and diminished thereafter. The significance of these observations is discussed in regard to transepithelial permeability and to the transport properties of LLC-PK1 cells.

1-Methyl-3-isobutylxanthine↗
PubMed1983

A fungal cellulase shows sequence homology with the active site of hen egg-white lysozyme.

The N-terminal amino acid sequence of an endo-beta-1,4-glucanase from the cellulase complex of the white-rot fungus Schizophyllum commune has been determined. The sequence from Glu-33 to Tyr-51 was homologous with the active site sequences of various hen egg-white type lysozymes, including lysozyme catalytic residues (Glu-35, Asp-52) and substrate binding residue Asn-44. The homology offers evidence for a lysozyme-type mechanism in enzymic hydrolysis of cellulose.

Agaricales↗
PubMed1983

Plasmid-determined beta-lactamases identified in a group of 204 ampicillin-resistant Enterobacteriaceae.

Information is presented on the plasmid-determined beta-lactamases identified in 204 strains of ampicillin-resistant Enterobacteriaceae. The type most frequently identified was TEM-1 (in 85.3% of the strains), followed by SHV-1 (14.70%). Two types of plasmid-determined beta-lactamase were identified in 20 strains; in 18 of them one of the two was TEM-1 and in 13, SHV-1 (the TEM-1 + SHV-1 combination was observed in 12 strains). In the 41 Klebsiella strains the most frequently identified enzyme was SHV-1 (in 28 of the strains) and the proportion of strains with two plasmid-determined beta-lactamases was higher than in the other species studied.

Ampicillin↗