Search PubMed⌕ Search

Biomedical subjects

S Lopez

Publications and source records attributed to S Lopez.

At least 109 records · Page 6Linked to original sources
PubMed1985

The nonstructural proteins of Sindbis virus as studied with an antibody specific for the C terminus of the nonstructural readthrough polyprotein.

A dodecapeptide containing the sequence of the C terminus of the nonstructural polyprotein of Sindbis virus has been synthesized and used to immunize rabbits. The antisera obtained precipitated polypeptides from cells infected with the HR strains of Sindbis or with temperature-sensitive mutants ts11 or ts18. Four different polypeptides, having apparent molecular weights of approximately 250,000, 220,000, 155,000, and 72,000, were immunoprecipitated by the antipeptide antiserum. The largest of these polypeptides is sufficiently large to represent a polyprotein translated from the entire nonstructural region of the genome. These data suggest that nsP4 of molecular weight 72,000 is produced by translation of the entire nonstructural region of the genome, which requires readthrough of an opal termination codon immediately upstream of nsP4, followed by post-translational cleavage of this polyprotein. The amounts of nsP4 and its precursors found in infected cells are small relative to the amounts of other nonstructural proteins present, as would be expected if readthrough of a termination codon is required. In addition, the relative amounts of nsP4 and of its precursors differ in HR-infected or ts mutant-infected cells and differ with temperature of infection, suggesting that temperature of infection or ts lesions affect translation and processing of the precursor polyprotein.

Animals↗
PubMed1984

Thoracic outlet syndrome: diagnosis and management with a new surgical technique.

In 71 patients with thoracic outlet syndrome, the signs and symptoms of which (Table 1) were assessed revealing several findings previously not reported in association with this condition, 119 surgical procedures were performed according to a newly-developed technique described in this paper. As compared with a substantial number of unsuccessful early and late outcomes rendered through first-rib resection or scalenectomy, the new technique, scalenotomy, led to excellent results in 100% of all cases (Table 2). No complications were seen and no recurrences were observed during an average follow-up period of one year. An additional finding was that, on use of the new technique, even in the presence of a symptomatic cervical rib or hypoplastic first thoracic rib, resection was not necessary to provide the patients with complete recovery from the syndrome.

Diagnosis, Differential↗
PubMed1983

Changes in the subcellular distribution of insulin receptors in rat liver induced by acute endogenous hyperinsulinemia.

The effects of an acute increase in endogenous plasma insulin on the subcellular distribution of the insulin receptors in rat liver have been examined. Plasma membranes, Golgi fractions, and a total particulate fraction have been prepared in rats (BW, 200 g) various times after the injection of glucose (300 mg), arginine (200 mg), glucagon (75 micrograms), and tolbutamide (10 mg). These fractions have been examined for their ability to bind [125I]insulin after solubilization by Triton X-100. The injection of glucose, which causes a 5-fold elevation in the plasma insulin concentration, results in a 20-25% decrease in insulin binding to plasma membranes and, reciprocally, a 50-70% increase in insulin binding to Golgi fractions; insulin binding to the total particulate fraction is unaffected. These changes achieve maximum at 5-15 min, coinciding with the insulin peak, and undergo complete reversal in 1 h. The enhanced insulin-binding activity in Golgi fractions results almost exclusively from an increase in receptor number. Glucose-induced hyperinsulinemia also results in a 5-fold increase in the insulin content of Golgi fractions at 15 min. Other stimulants of insulin secretion, which elevate insulinemia to the same extent as glucose, also increase insulin binding to Golgi fractions and decrease insulin binding to plasma membranes, with no change in binding activity in the total particulate fraction. It is concluded that an acute increase in the plasma insulin concentration, induced by physiological stimuli, results in a rapid and reversible translocation of the insulin receptors from the surface to the interior of the hepatocyte without affecting their total number.

Acute Disease↗
PubMed1983

[Effects of acute changes in endogenous insulin levels of the blood on the subcellular distribution of insulin receptors in the rat liver].

The effects of acute changes in endogenous insulinemia on the number and subcellular distribution of insulin receptors in rat liver have been studied. After injecting stimulants or inhibitors of insulin secretion, we examined various subcellular fractions from male rats (200 g) for their ability to specifically bind 125I-insulin. Glucose (300 mg) elevated plasma insulin 4 to 6-fold and increased the number of insulin receptors in Golgi fractions by 50%; it decreased the number of receptors in plasma membrane by 20%. These changes were maximal by 5-15 min and reversible in one hour. Arginine (200 mg), glucagon (75 micrograms) and tolbutamide (10 mg), which elevated insulinemia to the same extent as glucose, also increased insulin binding to Golgi fractions. Conversely, somatostatin (40 micrograms) and diazoxide (10 mg), which lowered plasma insulin 3 to 4-fold, decreased insulin binding to Golgi fractions by 20-25%. In all cases, the total number of receptors measured on a crude particulate fraction was not affected. Thus, acute changes in endogenous insulinemia caused a redistribution of insulin receptors in hepatocytes. It is suggested that this redistribution resulted from changes in the internalization rate of the receptors, which itself was a function of the degree of receptor occupancy.

Animals↗
PubMed1980

Comparison of human rotaviruses isolated in Mexico City and in Santiago, Chile, by electrophoretic migration of their double-stranded ribonucleic acid genome segments.

During the period October to December 1979, rotaviruses were obtained from infants and young children hospitalized with acute gastroenteritis in Mexico City and were compared by analysis of the migration of their double-stranded ribonucleic acid (RNA) genome segments in gel electrophoresis. Comparison of the results of this analysis and of those of similar studies carried out in 1977 and 1978 showed that the two rotavirus electropherotypes designated 2s and 21 have been continuously present and that the proportion in which these two types have been found in hospitalized patients has varied greatly year to year. The RNAs from rotaviruses 2s and 21 differed in the electrophoretic migraton of at least eight genome segments. However, RNAs from virus assigned to the same electrophoreotypes were not necessarily identical: on the basis of small but significant differences in the migration of segment 7, 8, or 9, isolates of types 2s and 21 could be assigned to two and three different subtypes, respectively. Human rotaviruses obtained in a distant geographical region, Santiago, Chile, in July 1979 had RNA electrophoretic patterns similar to that of electropherotype 21 but different from it in the migration of one or two of the larger RNA segments.

Child, Preschool↗
PubMed1979

Women physicians in medical academia. A national statistical survey.

We determined the representation of women physicians on US medical school faculties by enumeration from school catalogues according to professorial rank, title series, and department affilitation. We also compiled similar data for top-level administrative posts, using periodic chronological comparisons from 1955 through 1977 and 1978. Despite a burgeoning population of women medical students, we found a pattern of underuse of women physicians characterized by limited upward mobility on the faculty (professor: median, 3.0%; range, 0% to 18.2%; assistant professor; median, 7.3%; range, 0% to 28.7%). There were no women in chief executive positions.

Administrative Personnel↗
PubMed1975

Disruption of normal forelimb regeneration in adult Notophthalmus viridescens by sublethal concentrations of trypan blue.

The effects of the vital dye trypan blue (TpB) on the regeneration of amputated newt forelimbs were examined. Administration of the dye (10 mug/g body weight) via IP injection during the early wound healing and dedifferentiation phases of regeneration inhibited the normal regenerative response. The accumulation phases of regeneration are similarly halted but only by greater concentrations of TpB (50 mug/g body weight) while redifferentiation and morphogenesis are only affected by still greater concentrations of the dye (100 mug/g body weight). In addition to abolishing the regenerative response, low levels of TpB were also capable of inducing skeletal abnormalities in the regenerates as might be expected from previous reports on the teratogenicity of the dye. The in vitro action of newt hyaluronidase (as well as purified testicular hyaluronidase) on hyaluronate was diminished by TpB, with virtually complete inhibition observed at initial reaction mixture concentrations of 100 mug/ml. The results of this study suggest that TpB acts to disrupt the normal regenerative response by preventing dedifferentiation and remodeling, perhaps by inhibition of various necessary lytic enzyme functions or by interference with normal intercellular communications.

Animals↗
PubMedDate not supplied

Diagnostic and prognostic significance of beta 2-microglobulin during HIV infection.

The serum levels of beta 2-microglobulin (beta 2-m) were determined in 80 intravenous drug addicts (IVDA) with acquired immunodeficiency syndrome (AIDS), in 128 HIV-positive IVDA with persistent generalized lymphadenopathy (PGL) and in 44 HIV-seronegative IVDA. Seventy-two out of 80 (90%) AIDS patients had elevated serum beta 2-m levels and high levels of beta 2-m were also found in 105 of 128 (82%) HIV-infected subjects without AIDS. The mean beta 2-m level was significantly higher in HIV-infected patients with PGL than in HIV-negative IVDA. Nine out of 64 (14%) PGL patients developed AIDS in a period of 24-54 months. In these patients the mean beta 2-m level (5.16 +/- 2.37 mg/l), obtained from sera stored at the first observation, was significantly higher than in the other PGL patients (3.40 +/- 1.03 mg/l); in particular, 5 out of 7 PGL patients with beta 2-m levels greater than 5.0 mg/l showed an advanced disease.

Acquired Immunodeficiency Syndrome↗