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Biomedical subjects

A Brown

Publications and source records attributed to A Brown.

At least 487 records · Page 27Linked to original sources
PubMed1984

The interaction of DNA polymerase III and the product of the Escherichia coli mutator gene, mutD.

A comparison of DNA polymerase III core enzyme (McHenry, C. S., and Crow, W. (1979) J. Biol. Chem. 254, 1748-1753) prepared from wild type Escherichia coli and a strain harboring the mutator gene, mutD5 (Degnen, G. E., and Cox, E. C. (1974) J. Bacteriol. 17, 477-487) has revealed several differences in their properties. Among these are alterations in the heat stability, divalent cation requirement, pH optimum, 3'----5'-single strand exonuclease activity, and DNA-dependent conversion of a deoxynucleoside triphosphate to its corresponding monophosphate ("turnover"). The decrease in the 3'-single strand exonuclease and turnover indicate a defect in the editing function of the mutD strain, which is at least in part responsible for the high spontaneous mutation rate in mutD. Transformation of mutD by a hybrid plasmid, pRD3, constructed from an EcoRI restriction fragment of E. coli and pBR322, cures mutD of its abnormally high mutation rate, and simultaneously restores its 3'-exonuclease activity. These observations are consistent with the notion that the mutD gene product is a subunit of DNA polymerase III, and it either contains the catalytic site for the 3'-exonuclease or modulates its activity. From a consideration of the known molecular weights of the subunits in DNA polymerase III core (McHenry C. S., and Crow, W. (1979) J. Biol. Chem. 254, 1748-1753) the molecular weights of the two proteins translated in maxicells transformed with pRD3, and from a comparison of our results with those obtained with the mutator dnaQ (Horiuchi, T., Maki, H., Maruyama, M., and Sekiguchi, M. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 3770-3774) and the work of Cox and Horner (Cox, E. C., and Horner, D. L. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 2295-2299) as well as Echols et al. (Echols, H., Lu, C., and Burgers, P. M. J. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 2189-2192) we tentatively assign the mutD gene product to the epsilon subunit of DNA polymerase III.

Bacterial Proteins↗
PubMed1984

Capillary gas chromatography-mass spectrometry of carbohydrate components of legionellae and other bacteria.

Capillary gas chromatography using fused-silica columns followed by electron impact or chemical ionization mass spectrometry was used to profile and identify neutral and amino sugars present in several legionellae and other bacteria. A modified alditol acetate derivatization method was employed to produce volatile carbohydrate derivatives. Muramic acid, a component of bacterial peptidoglycan, was detected in all legionellae examined. Heptose, a component of bacterial lipopolysaccharide, was identified in Escherichia coli organisms and in several purified Gram-negative bacterial lipopolysaccharides but not in the legionellae examined. Two amino dideoxyhexoses were found to be present in several of the Legionellae examined. The potential of gas chromatography-mass spectrometry for the direct chemical characterization of microorganisms is discussed.

Amino Sugars↗
PubMed1984

Organization of the infraorbital nerve in rat: a quantitative electron microscopic study.

The normal organization of the rat's infraorbital (IO) nerve was studied using conventional electron microscopic (EM) methods. Just caudal to the infraorbital foramen, at the level of the anterior superior alveolar foramen, the nerve was composed of 18-25 fascicles which ranged from 575 to 87,923 micron2 in cross-sectional area. Complete axon counts from thin sections taken at this level demonstrated that the IO nerve contained an average of 19,740 (S.D. = 2054) myelinated and 13,319 (S.D. = 1159) unmyelinated axons. The average diameter (including the myelin sheath) for medullated fibers was 4.42 micron (S.D. = 1.76) and that for unmyelinated axons was 0.60 micron (S.D. = 0.16). The fiber diameter distributions for both myelinated and unmyelinated axons were essentially unimodal.

Animals↗
PubMed1984

Prostaglandin production from homogenates of separated glandular epithelium and stroma from human endometrium.

The biosynthesis of prostaglandins by isolated epithelial glandular and stromal cells was studied after collagenase digestion of endometrium collected from women at various stages of the menstrual cycle. Homogenates of the separate cell types were incubated for 60 minutes with 2.08 micrograms 1(14)C arachidonic acid and the products separated by thin layer chromatography. Both glandular and stromal homogenates synthesised PGF2 alpha. More PGF2 alpha was synthesised by glandular epithelium separated from both proliferative and secretory endometrium than by stroma. The ratio of PGF2 alpha/PGE2 was greater in glands and stroma isolated from secretory than proliferative endometrium. Small but significant amounts of 6-keto-PGF1 alpha were produced by all cell types. These results suggest that the increased synthesis of PGF2 alpha from secretory endometrium is due, at least in part, to increased activity of cyclo-oxygenase enzyme in the glandular epithelium.

Arachidonic Acid↗
PubMed1984

Influenza A/Philippines/2/82 outbreak in a nursing home: limitations of influenza vaccination in the aged.

The failure of the 1982-1983 influenza vaccine to protect elderly NHCU residents from clinical infection with influenza A/Philippines/2/82 resulted primarily from antigenic drift of the epidemic strain, inasmuch as the attack rates in the vaccinated and nonvaccinated patients were not significantly different. This experience supports the decision to replace A/Bangkok/1/79 with A/Philippines/2/82 virus antigen in the 1983-1984 influenza vaccine.

Adult↗
PubMed1984

Hippocampal field potential: a microcomputer aided comparison of amplitude and integral.

A microcomputer based system is described for the analysis of various aspects of hippocampal field potential response recorded in vitro, either in the dendritic or somatic region. A comparison is made between the average amplitude and the time integral of synaptically evoked population spike at the cell body layer, following various intensities of stimuli delivered to the stratum radiatum. There was a good correlation between the two measures at low and intermediate intensities of stimulation. With stimulus intensities beyond those eliciting the population spike of maximal integral, the amplitude of the population spike further increased while its duration decreased. It is concluded that the integral provides a more accurate estimate of the extent of neuronal firing than the amplitude.

Animals↗
PubMed1984

Glucagon secretion by dispersed alpha cell enriched islets from streptozotocin treated hamsters in perifusion.

Streptozotocin (70 mg/kg) was administered intravenously to female Syrian hamsters. The hamsters received insulin (5U/animal/day). Insulin treatment was withdrawn 3 days before sacrifice in one group, while another group was maintained on insulin until sacrifice. Ten to 14 days following streptozotocin administration the animals were killed, and the pancreatic islets isolated and subsequently dispersed. Islet DNA content was decreased while the glucagon content was elevated by streptozotocin treatment. The glucagon secretory responsiveness of the dispersed alpha cells of control animals was stimulated by glucopenia and decreased by glucose. Alpha cells of streptozotocin hamsters were not only suppressed but were actually stimulated by high glucose concentrations. Treatment with insulin in vivo but not in vitro, resulted in a restoration of the alpha cells responsiveness to glucose suppression. Dispersed alpha cells from control and streptozotocin treated animals were stimulated by arginine. Basal and total glucagon secretion was greatest in dispersed alpha cells from streptozotocin treated animals. We concluded: that the paradoxical response of alpha cells to glucose noted in diabetes is not due to short term insulin deprivation or the lack of morphologic contact with beta cells; that the alpha cells require and insulin stimulated islet metabolite and extra islet materials to respond appropriately to glucose; and that the alpha cells response to arginine is mediated independently of glucose regulation.

Animals↗
PubMed1984

Plasmid transfer into members of the family Legionellaceae.

The plasmids RP4 and pPH1JI::Mu::Tn5 were transferred with moderate frequency from Escherichia coli to Legionella pneumophila (strain Bloomington 2) and Fluoribacter (Legionella) bozemanae (strain WIGA). The frequency of transfer to Tatlockia (Legionella) micdadei (strain Tatlock) was much lower. In these transconjugant strains the plasmids were maintained following at least 10 nonselective passages. However, the introduced plasmids could not be transferred from these strains to several other strains of Legionella or Tatlockia with a detectable frequency, yet they could be transferred to a restriction-modification deficient (rm-) E. coli strain with moderate frequency. This suggests not only that the expression of transfer genes may be repressed but that the legionellae are poorer recipients than are the rm- E. coli.

Bacteria↗
PubMed1984

Capillary gas chromatographic analysis of carbohydrates of Legionella pneumophila and other members of the family Legionellaceae.

Legionella pneumophila, the causative agent of Legionnaires disease, and related organisms have previously been characterized primarily by conventional bacteriological methods, DNA-DNA hybridization, antigenic analysis, and fatty acid analysis. By capillary gas chromatographic analysis for carbohydrates, we have shown that muramic acid and glucosamine, characteristic markers of bacterial cell walls, were present in samples of L. pneumophila and a group of legionella-like organisms. Some bacterial samples contained two unusual isomeric aminodideoxyhexoses (X1 and X2). L. pneumophila was characterized by the absence of fucose and the presence of the peak X1. Tatlockia micdadei (Legionella micdadei) was distinguishable by the presence of large amounts of rhamnose and fucose and by the absence of X1 and X2. Fluoribacter strains were much more variable in their carbohydrate composition. These data suggest that, in addition to other reported techniques, carbohydrate profiling by capillary gas chromatography can be a valuable diagnostic method in reference microbiology laboratories for differentiating members of the family Legionellaceae.

Carbohydrates↗
PubMed1984

Identification of immunologically cross-reactive proteins of Sindbis virus: evidence for unique conformation of E1 glycoprotein from infected cells.

Hyperimmune antisera to purified Sindbis (SIN) or Semliki Forest (SF) virus were used to identify alphavirus-specific and cross-reactive proteins in virions and infected cells. The hyperimmune sera participated in homologous and cross-cytolysis of alphavirus-infected cells, and the use of monospecific antisera to SIN structural proteins suggested that E1 and E2 could serve as target proteins in cytolysis. Proteins from purified virions or infected cells were extracted with Nonidet P-40, denatured by procedures for sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose solid supports, and reacted with hyperimmune sera and 125I-labeled protein A (immunoblotting on denatured proteins). Alternatively, native proteins extracted by mild Nonidet P-40 treatment were precipitated with hyperimmune sera before denaturation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After immunoblotting, homologous antiserum reacted with the virus structural proteins E1, E2, capsid extracted from purified virions, and the counterparts of these proteins extracted from infected cells. In addition, PE2 and a 92,000-molecular-weight protein from infected cells reacted with homologous antiserum. These proteins were also immunoprecipitated with homologous antiserum. After immunoblotting, the Sindbis capsid protein was shown to be cross-reactive whether derived from purified virions or from infected cells; no cross-reactivity was observed with PE2 or E2 from either source, and the E1 glycoprotein was shown to be cross-reactive only when obtained from virions. However, the E1 glycoprotein could be cross-immunoprecipitated from infected cells (as well as from disrupted virions), and, in addition, capsid and a 92,000-molecular-weight protein were cross-immunoprecipitated from infected cells. These results suggest that a native conformation of the cell-associated E1 glycoproteins may be required for immunological cross-reactivity (immune precipitation), whereas virion but not cell-associated E1 retains immunological cross-reactivity after denaturation (immunoblot technique). The findings extend our previously published evidence which suggested that alphavirus maturation is accompanied by a change in immunological cross-reactivity with respect to E1.

Animals↗
PubMed1984

Segmental dilatation of the ileum.

One of the rarer causes of intestinal obstruction in the neonatal period is segmental dilatation of the ileum. The case histories, radiological and histological details of four patients are presented together with a short review of the literature.

Dilatation, Pathologic↗
PubMed1984

The effect of dietary protein on cystine excretion in patients with cystinuria.

Seven patients with homozygous cystinuria were studied on a metabolic ward to determine the effect of dietary manipulation on urinary cystine excretion. Isocaloric diets were calculated based on body weight and activity. Balance studies were performed for 5 days on a low protein diet (9.4 +/- 1.0% total calories) with equal amounts of animal and plant protein sources and an additional 5 days on a high protein (27 +/- 3.0% of total calories) with 70% animal protein. A significant (p less than 0.01) decrease in the excretion of 1/2-cystine, histidine, 3-methylhistidine, 1-methylhistidine, lysine, and ornithine plus arginine occurred on the low protein diet. The mean excretion of 1/2-cystine on the high protein diet was 6.13 +/- 1.48 mMoles per 24 hours which decreased to 4.89 +/- 1.06 mMoles per 24 hours on the low protein diet (p less than 0.001). Thirty seven percent of urine collections during the study were less than 2 liters/24 hours despite the fact that patients were encouraged to drink enough fluid to make 3 liters of urine/24 hours. For patients whose customary diet is high in animal protein, a more vegetarian diet may significantly reduce urinary cystine excretion. Cystine excretion in patients with cystinuria may be significantly different from day to day if animal protein consumption is variable.

Adolescent↗
PubMed1984

Acute isoniazid intoxication: reversal of CNS symptoms with large doses of pyridoxine.

Acute toxicity from ingestion of isoniazid (INH) is manifested by coma and seizures unresponsive to conventional therapy. Though small doses of pyridoxine can reverse the seizure activity of acute isoniazid toxicity, large doses of pyridoxine (B6) are needed to completely reverse the symptoms. A case report is presented demonstrating the need for large doses of pyridoxine to reverse the symptoms of isoniazid intoxication and the literature of isoniazid toxicity in the pediatric age group is reviewed.

Adolescent↗
PubMed1984

Role of local secretory and motility changes in the pathogenesis of experimental duodenal ulcer.

Changes in gastric acid and pepsin secretions do not fully account for the duodenal ulcerogenic effect of cysteamine or propionitrile in the rat. We investigated the role of pancreatic and biliary secretions as well as motility changes in the duodenum. Bypass of bile to the jejunum and/or ablation of pancreatic secretion or drainage of these secretions through chronic duodenal fistula aggravated the cysteamine-induced duodenal ulcers. Biliary bypass to the proximal duodenum, on the other hand, decreased the incidence and intensity of experimental duodenal ulcers. An increased and dopamine-sensitive myoelectric activity caused by cysteamine or propionitrile was recorded in the proximal duodenum, indicating a state of hypermotility. Indeed, a decreased quantity of bilirubin was recovered through the chronic fistula in the proximal duodenum, suggesting an impaired delivery of bile to the ulcer area after cysteamine administration. Thus, duodenal hypermotility probably prevents the proper mix and neutralization of gastric acid and duodenal (mucosal, biliary and pancreatic) secretions, predisposing to ulceration in the proximal duodenum.

Animals↗
PubMed1984

Antibodies against osteosarcoma and colon cancer.

Two monoclonal antibodies with anti-human tumour reactivity were produced by murine hybridomas. One, 791T/36, is an IgG2b which was raised against a cultured human osteogenic sarcoma cell line, 791T. This antibody reacts with a high proportion of osteogenic sarcomas, and also with other tumour types. It has been used successfully as a tumour localising antibody in vivo and a targeting agent in vitro. The other antibody, C14/1/46, was raised against a human colonic adenoma. An IgM antibody, it reacts with most colorectal carcinoma cells but only with a small subpopulation of cells within the normal mucosa. It has been shown to recognise a difucosylated Type-2 blood-group chain, which has raised expression in colorectal carcinoma tissue.

Animals↗
PubMed1983

Petrol sniffing lead encephalopathy.

A patient is described with organic lead poisoning due to petrol inhalation. There was marked improvement clinically and electroencephalographically after chelation therapy, which was associated with a fall in red cell lead levels.

Adult↗