Search PubMed⌕ Search

Biomedical subjects

M Silverman

Publications and source records attributed to M Silverman.

At least 397 records · Page 22Linked to original sources
PubMed1978

Ontogenic development and tissue distribution of renal proximal tubule brush border membrane antigens in the dog.

Using an antibody raised against highly purified dog renal proximal tubule brush border membranes, we have investigated the tissue distribution and ontogenic development of antigens sharing specificity with those in the renal brush border membrane. The antigens have been found in the small intestine, gall bladder, epididymis, pancreas, salivary gland, lacrimal gland, liver and spleen. Examination of embryos at various stages of gestation has revealed that the antigens make their appearance early in organogenesis, and are present in the cytoplasm as well as on the membrane during foetal development. Absorption studies have shown that at least two populations of antigens are present in the kidney: one appears to be kidney-specific and the other is shared by many epithelia. Maltase has been identified as one of the shared antigens.

Animals↗
PubMed1977

Recombinational switch for gene expression.

Flagellar antigens are specified by two genes, H1 and H2. The expression of these genes is regulated such that only one gene activity, or phase, is expressed at a given time. Molecular cloning techniques were used to isolate the segments of Salmonella DNA which contain these genetic loci. Heteroduplex analyses revealed an anomaly in the cloned fragment, that is, and apparent inversion, which was shown to be adjacent to the H2 gene. A correlation was demonstrated between the phase state of the H2 gene and the sequence of the adjacent segment. We propose that an inversion of this region is the phase-determining event in flagellar gene expression in Salmonella.

Antigens, Bacterial↗
PubMed1977

Immunologic characterization of plasma membranes from the renal proximal tubule of the dog.

Plasma membrane fractions from the brush border (BBM) and antiluminal (ALM) surfaces of the dog's renal proximal tubule cell were separated using free-flow electrophoresis. Rabbits immunized with BBM rapidly produced antibody, but rabbits immunized with ALM did not respond. Indirect immunofluorescence and immunoferritin studies showed that the antibody reacts with the brush border of the proximal tubules in the normal kidney of the adult dog. It also reacts with the surface membranes of certain other absorptive and secretory epithelia, such as gall bladder, small intestine, epididymis, and lacrimal gland. The antibody has affinity for the membrane maltase without affecting its catalytic activity, but does not appear to have affinity for the membrane alkaline phosphatase or the high affinity binding site for phlorizin present in the BBM. Polyacrylamide electrophoresis of solubilized BBM showed approximately 37 protein bands and four glycoproteins. We conclude that the proximal tubule cell is immunologically polarized with respect to the distribution of antigenic proteins, and that the BBM is highly antigenic. The antigenic components appear to be high molecular weight glycoproteins present in the glycocalyx.

Alkaline Phosphatase↗
PubMed1977

Sugar uptake into brush border vesicles from normal human kidney.

Uptake studies of simple sugars were performed on a membrane fractions containing osmotically active vesicles prepared from normal human kidney cortex. The uptake of D-glucose was found to be sodium-dependent and phlorizin-sensitive. The specificity of the D-glucose transport mechanism is such that it is shared by alpha-methyl-D-glucoside, D-galactose, and 5-thio-D-glucose, while 2-deoxy-D-glucose, 3-O-methyl-D-glucose, D-mannose, and D-fructose show little, if any, affinity. Measurement of the sodium-dependent component of the initial D-glucose uptake as a function of glucose concentration resulted in a curvilinear Scatchard plot, indicating the possibility of cooperative effects, or alternatively, the existence of two (or more) sodium-dependent D-glucose transporters. In the case of two transporters, we estimate that Km congruent to 0.3 mM and Vmax congruent to 2.5 nmol/min per mg of protein for the "high-affinity transporter," and Km approximately 6 mM and Vmax approximately 8 nmol/min per mg of protein for the "low-affinity transporter." These specificity and kinetic properties strongly suggest that the sodium-dependent D-glucose transport mechanism characterized in our studies is localized to the brush border of the proximal tubule.

Adenosine Triphosphatases↗
PubMed1977

Chemotaxis in Escherichia coli: methylation of che gene products.

The products of three chemotaxis-specific genes in Escherichia coli, cheM, cheD, and cheZ, are methylated. The cheZ gene codes for the synthesis of a 24,000 molecular weight polypeptide that appears in the cytoplasm. cheM codes for the synthesis of a membrane-bound polypeptide with a molecular weight of 61,000. cheD codes for another membrane-bound polypeptide with an apparent molecular weight of 64,000. CheM(-) mutants show chemotaxis toward some attractants (Tar(-) phenotype), while CheD(-) mutants respond to other attractants (Tsr(-) phenotype). The double mutant (CheD(-), CheM(-)) does not respond to any attractant or repellent tested. Therefore, these polypeptides play a central role in chemotaxis. They collect information from two subsets of chemoreceptors and act as the last step in the chemoreceptor pathway and the first step in the general processing of signals for transmission to the flagellar rotor. It is suggested that they may be involved in both an initial process that reflects the instantaneous state of the chemoreceptors and in an integrative, adaptive process. Two other genes, cheX and cheW, are required for the methylation of the cheD and cheM gene products.

Bacterial Proteins↗
PubMed1977

Interprofessional education of the new health practitioner.

This is a report of a survey of the interprofessional education activities included in 54 physician's assistant and 60 nurse practitioner programs. In a majority of such new health practitioner programs, the importance of interprofessional education as a part of training for team health care delivery has been recognized, and some structured interprofessional activity has been provided. A variety of methods are being used to achieve the objectives of effective team delivery of primary health care, including the mixing of students in both classroom and clinical settings and the inclusion of specific courses on role and professional identity. Seventy percent of physician's assistant students and 38 percent of nurse practitioner students in the programs included in the study have at least one classroom activity shared with another health profession group, most commonly medical students. Only a surprisingly small percentage of programs were involved in any evaluation of their interprofessional activities. In spite of the primary care orientation of new health practitioner programs, less than 40 percent offer clinical experience on a health team in a primary care setting.

District of Columbia↗
PubMed1977

Characterization of lambda Escherichia coli hybrids carrying chemotaxis genes.

Molecular cloning techniques were used to construct hybrid Escherichia coli lambda phage and isolate Col E1 factors that carried the cheB region of the E. coli genome. The products of these genes were examined by using a series of deletions in the phage to stimulate specific polypeptide synthesis in ultraviolet-irradiated cells and by using Col factor to program protein synthesis in minicells. Seven flagellar related polypeptides were synthesized. Three of these with apparent molecular weights of 38,000, 28,000, and 8,000 were associated with the cheB region; three polypeptides 63,000, 61,000, and 60,000 were associated with the region that maps between cheB and cheA. These bands were referred to as the triplet group. We suggest that these polypeptides are the same as the methyl-accepting chemotaxis protein described by Kort et al. (Proc. Natl. Acad. Sci. U.S.A. 72:3939-3943, 1975). Another polypeptide with a molecular weight of 12,000 is associated with the cheA region which also produces at least three gene products. We conclude that the cheA-cheB region in E. coli is complex. Further genetic and biochemical analyses are required to describe all of these products.

Bacterial Proteins↗
PubMed1977

Identification of polypeptides necessary for chemotaxis in Escherichia coli.

Molecular cloning techniques were used to construct Escherichia coli-lambda hybrids that contained many of the genes necessary for flagellar rotation and chemotaxis. The properties of specific hybrids that carried the classical "cheA" and "cheB" loci were examined by genetic complementation and by measuring the capacity of the hybrids to direct the synthesis of specific polypeptides. The results of these tests with lambda hybrids and with a series of deletion mutations derived from the hybrids redefined the "cheA" and "cheB" regions. Six genes were resolved: cheA, cheW, cheX, cheB, cheY, and cheZ. They directed the synthesis of specific polypeptides with the following apparent molecular weights: cheA, 76,000 and 66,000; cheW, 12,000; cheX, 28,000; cheB, 38,000; cheY, 8,000; and cheZ, 24,000. The presence of another gene, cheM, was inferred from the protein synthesis experiments. The cheM gene directed the synthesis of polypeptides with apparent molecular weights of 63,000, 61,000, and 60,000. The synthesis of all of these polypeptides is regulated by the same mechanisms that regulate the synthesis of flagellar-related structural components.

Bacterial Proteins↗
PubMed1977

Genetic analysis of Escherichia coli K-12 region I flagellar mutants.

Flagellar mutants in Escherichia coli region I were obtained by selection for resistance to the flagellotropic phage chi. F' elements carrying this region of the E. coli genome were then constructed. Stable merodiploid strains with a flagellar defect on the exogenate and another on the endogenote were prepared. These merodiploids yielded information on the complementation behavior of mutations in this region. Region I was shown to include at least six cistrons, flaV, flaK, flaL, flaM, flaS, and flaT. Mu-induced and deletion fla mutants were also isolated. By using these mutant strains, the transcriptional order was shown to be flaV-flaK-flaL-flaM-flaS-flaT. The definition of region I fla genes and their transcriptional relationships were confirmed by genetic tests with hybrid A phage carrying fla genes in this region.

Chromosome Mapping↗
PubMed1977

Localization of proteins controlling motility and chemotaxis in Escherichia coli.

Flagellar proteins controlling motility and chemotaxis in Escherichia coli were selectively labeled in vivo with [35S]methionine. This distribution of these proteins in subcellular fractions was examined by sodium dodecyl sulfatepolyacrylamide gel electrophoresis and autoradiography. The motA, motB, cheM, and cheD gene products were found to be confined exclusively to the inner cytoplasmic membrane fraction, whereas the cheY, cheW, and cheA (66,000 daltons) polypeptides appeared only in the soluble cytoplasmic fraction. The cheB, cheX, cheZ, and cheA (76,000 daltons) proteins, however, were distributed in both the cytoplasm and the inner membrane fractions. The hag gene product (flagellin) was the only flagellar protein examined that copurified with the outer lipopolysaccharide membrane. Differences in the intracellular locations of the che and mot gene prodcuts presumably reflect the functional attributes of these components.

Bacterial Proteins↗
PubMed1977

Synthesis of mot and che gene products of Escherichia coli programmed by hybrid ColE1 plasmids in minicells.

Hybrid Escherichia coli ColE1 plasmids carrying the genes for motility (mot) and chemotaxis (che) were transferred to a minicell-producing strain. The mot and che genes on the hybrid plasmid directed protein synthesis in minicells. Polypeptides synthesized in minicells were identical to the products of the motA, motB, cheA, cheW, cheM, cheX, cheB, cheY, and cheZ genes previously identified by using hybrid lambda and ultraviolet-irradiated host cells (Silverman and Simon, J. Bacteriol. 130:1317-1325, 1977), thus confirming these gene product assignments. The products of some che genes (cheA and cheM) appeared as more than one band on polyacrylamide gel electrophoresis, but analysis of partial peptide digests of these polypeptides suggested that the multiple forms were coded for by a single gene. Measurement of the physical length of the hybrid plasmids allowed an estimate of the amount of coding capacity of the cloned deoxyribonucleic acid, which was devoted to the synthesis of the mot and che gene products. These estimates were also consistent with the hypothesis that the multiple polypeptides corresponding to cheA and cheM were the products of single genes.

Bacterial Proteins↗
PubMed1977

Diagnosis of acute bacterial pneumonia in Nigerian children. Value of needle aspiration of lung of countercurrent immunoelectrophoresis.

Eighty-eight Nigerian children with untreated, severe, acute pneumonia were investigated by standard bacteriological techniques (blood culture and culture of pharyngeal secretions) and by needle aspiration of the consolidated lung. Countercurrent immunoelectrophoresis (CIE) against grouped pneumococcal and Haemophilus influenzae type b antisera was carried out on serum samples from 45 patients. The aetiology of pneumonia was shown by examination of the needle aspirate in 70/88 patients (79%), by CIE in 9/45 patients (20%), and by blood culture in 4/36 patients (11%). Overall, a bacterial cause for pneumonia was shown in 73/88 patients (83%). The results of pharyngeal culture were misleading when compared with cultures of needle aspirates. The prediction of aetiology from the radiological appearance was alos inaccurate, even for labor pneumonia. Needle aspiration of the lung, with a low (5%) and minor complication rate, merits wider application in the diagnosis of acute pulmonary infections in children. Tradiational bacteriological techniques (blood culture and pharyngeal culture) are of very limited value. The place of CIE in the investigation of childhood pneumonia still needs thorough evaluation.

Acute Disease↗
PubMed1977

Bacterial flagella.

Explore the source record for details and available documents.

Antigens, Bacterial↗
PubMed1977

Sugar interaction with the antiluminal surface of the proximal tubule in dog kidney.

The pulse-injection multiple-indicator-dilution technique in vivo has been used to investigate bidirectional sugar interaction with the antiluminal surface of the nephron in dog kidney. Simultaneous renal vein and urine outflow curves were obtained for radiolabeled sugars known to interact with the antiluminal surface. The following sugars were tested relative to T-1824 albumin (plasma reference) and creatinine (extracellular reference) under conditions of high-dose phlorizin preloading (75-225 mg/kg): D-glucose, D-xylose, D-fucose, D-mannose, D-galactose, L-arabinose, myoinositol, and D-fructose. The results indicate that as the plasma concentration of phlorizin increases there is, first, a partial inhibition of sugar interaction at the antiluminal membrane so that only unidirectional uptake of sugar from blood to tubular cell is observed, followed by complete inhibition of sugar interaction at the peritubular face of the antiluminal membrane, resulting in superposition of sugar and creatinine curves in the renal vein effluent. Two possible interpretations exist. i) Phlorizin exerts its inhibitory action successively at the cytoplasmic and then at the peritubular face of the antiluminal membrane. Moreover, since all of the sugar substrates are inhibited by phlorizin, the data suggest that the sugar-membrane interaction takes place at a common site at the level of the proximal tubule. ii) Alternatively, the action of phlorizin could result from a metabolic inhibitory effect affecting multiple sugar transport systems at the antiluminal membrane.

Animals↗
PubMed1977

The epidemiology of drug promotion.

A survey was conducted on the promotion of 28 prescription drugs in the form of 40 different products marketed in the United States and Latin America by 23 multinational pharmaceutical companies. Striking differences were found in the manner in which the identical drug, marketed by the identical company or its foreign affiliate, was described to physicians in the United States and to physicians in Latin America. In the United States, the listed indications were usually few in number, while the contraindications, warnings, and potential adverse reactions were given in extensive detail. In Latin America, the listed indications were far more numerous, while the hazards were usually minimized, glossed over, or totally ignored. The differences were not simply between the United States on the one hand and all the Latin American countries on the other. There were substantial differences within Latin America, with the same global company telling one story in Mexico, another in Central America, a third in Ecuador and Colombia, and yet another in Brazil. The companies have sought to defend these practices by contending that they are not breaking any Latin American laws. In some countries, however, such promotion is in clear violation of the law. The corporate ethics and social responsibilities concerned here call for examination and action.

Adrenal Cortex Hormones↗