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Biomedical subjects

C Coker

Publications and source records attributed to C Coker.

30 records · Page 2Linked to original sources
PubMed1996

Glucose metabolism and catecholamine responses during physical exercise in non-insulin-dependent diabetes.

Blood glucose, lactate, insulin, C-peptide, norepinephrine and epinephrine concentrations were determined in non-insulin-dependent diabetic patients and in healthy controls before, during and after moderate exercise, to evaluate the effects of physical exercise on glucoregulation. Ten diabetic and ten healthy control females bicycled 14 minutes at 60% of their maximal heart rates. In the diabetic patients, there were no significant changes in blood glucose levels post-exercise, while in controls the 60 minute post-exercise levels were higher than those measured in mid-exercise (p < 0.05). Lactate concentrations increased with exercise in both groups in a similar manner, with highest values at the end of exercise. No significant changes in insulin and C-peptide levels were induced with exercise in either group. Norepinephrine and epinephrine concentrations increased 2.5-3 fold with exercise in both groups (p < 0.05 for all values) but in the diabetics an earlier and prolonged catecholamine response was observed. We propose that catecholamines prevent hypoglycaemia during exercise when changes in insulin and C-peptide do not occur. In diabetic patients with good metabolic control, the glucoregulatory response to exercise is not worse than in anthropometrically similar controls with similar levels of fitness.

Blood Glucose↗
PubMed1995

Lymphocyte subpopulations in children with vitamin D deficient rickets.

Recent studies have shown 1,25(OH)2D3-mediated modulation of the immune system. We examined lymphocyte subpopulations of 16 children with nutritional rickets. Most of the patients suffered more frequent infection episodes than the control group of 15 healthy children and low serum levels of 25OHD and 1,25(OH)2D, such as 38.2 +/- 8.6 ng/mL and 15.7 +/- 2.6 pg/mL respectively. This decrease correlated with a significant decrease in total T lymphocytes and an increase in B lymphocytes expressing surface IgA, IgM, IgG molecules. These results suggest that vitamin D plays an important role in the impaired functions of T lymphocytes which may lead to frequent infection episodes in nutritional rickets.

Child, Preschool↗
PubMed1992

Transcription analysis and nucleotide sequence of tox promoter/operator mutants of corynebacteriophage beta.

The production of diphtheria toxin (DT) by Corynebacterium diphtheriae C7 (beta) is transcriptionally regulated by the iron-dependent diphtheria toxin repressor, DtxR. Transcription of the tox gene was studied in wild-type C. diphtheriae C7 (beta) and in lysogens carrying mutants of beta that determine insensitivity to inhibition of DT production by iron. Under low iron conditions in all strains, tox-specific mRNA appeared and DT production began during late-log phase, and they increased to maximal levels at stationary phase. Under high iron conditions, tox-specific mRNA and DT production were strongly repressed in C7 (beta) but only partially repressed in C7 (beta tox-202) and C7 (beta tox-201). Under high and low iron conditions, DT production and tox-specific mRNA levels were greater in C7 (beta tox-201) and C7 (beta tox-202) than in wild-type C7 (beta). Addition of iron or rifampicin to low iron cultures of C. diphtheriae C7 (beta) repressed tox-mRNA production promptly and with a similar time course. In contrast, repression of tox-mRNA synthesis in C. diphtheriae C7 (beta tox-201) occurred promptly after addition of rifampicin but more slowly after addition of iron. Nucleotide sequence analysis revealed single G to A mutations at positions -47 and -48, within the preferred '-10' sequence of the tox promoter, in beta tox-201 and beta tox-202, respectively. The single nucleotide substitutions in the tox-201 and tox-202 regulatory alleles, therefore, have pleiotropic effects, causing increased activity of the promoter and partial resistance of the operator to iron-dependent repression.

Bacterial Proteins↗
PubMed1992

Optimizing staff scheduling by Monte-Carlo simulation.

DOCS is a computer program which generates the staff schedule. An accounting framework is combined with an optimization technique that searches for a schedule in which all accounts are simultaneously in balance. The search is accomplished using a Monte-Carlo process which shuffles staff within the schedule. The shuffling is biased according to each staffer's account balance: the staffer who owes the most is most likely to be scheduled.

Algorithms↗
PubMed1991

Two novel virulence loci, mxiA and mxiB, in Shigella flexneri 2a facilitate excretion of invasion plasmid antigens.

A bank of over 4,200 lacZ protein fusions in Shigella flexneri 2a was screened for fusions to temperature-regulated promoters. One mutant, BS260, was completely noninvasive on HeLa cells and mapped to a region on the 220-kb virulence plasmid in which we had previously localized several avirulent temperature-regulated operon fusions (A.E. Hromockyj and A.T. Maurelli, Infect. Immun. 57:2963-2970, 1989). The phenotype of BS260 was similar to that of the previously identified mxi (membrane expression of invasion plasmid antigens) mutants, since it made wild-type intracellular levels of the invasion plasmid antigens (Ipa) but was deficient in the surface expression of IpaB and IpaC. Six kilobases of DNA upstream of the BS260 fusion end joint were cloned, but no temperature-regulated promoter was found, whereas the fusion end joint clone of the noninvasive mxi operon fusion mutant BS226 contained a temperature-regulated promoter. The locus defined by BS260 was designated mxiA, and that defined by BS226 was designated mxiB. Closer analysis of the mxiA and mxiB phenotypes by a cell-free enzyme-linked immunosorbent assay revealed that the mutants failed to excrete IpaB and IpaC into the culture medium, whereas wild-type cells actively released these antigens. Excretion of the ipa polypeptides from wild-type bacteria was confirmed by Western blot analysis of culture supernatants. Protease protection experiments revealed that wild-type S. flexneri 2a actually had much lower levels of surface-exposed IpaB and IpaC relative to those in the total antigen pool. In addition, examination of cellular fractions showed that, although there was no IpaB or IpaC in the outer membrane of BS260 and BS226, the antigens did accumulate in the cytoplasmic membrane. A 76-kDa temperature-regulated polypeptide in wild-type S. flexneri was identified as the putative mxiA gene product. These results strongly suggest that IpaB and IpaC represent truly excreted proteins of S. flexneri and that the mxiA and mxiB loci on the plasmid code for accessory proteins required to facilitate their export through the bacterial outer membrane. These data also suggest that mxiA is part of an operon that specifies additional mxi genes. The products of this operon may constitute a unique multicomponent protein secretion apparatus involved in the transport of Shigella virulence determinants.

Animals↗
PubMed1990

Palliative intubation of malignant oesophageal strictures.

A 6-year experience (1981-1987) of palliative intubation of irresectable malignant oesophageal strictures is reported in 110 patients with a mean age of 70.3 (range 41-90) years. Pulsion intubation was performed on 71 patients, 11 (15.5%) of whom died, and traction intubation on 39 with 6 (15.4%) deaths. Seven deaths resulted from instrumental perforation, but six other patients survived perforation and left the hospital in satisfactory condition. Mean in-patient stay was 8 (range 1-26) days. Non-fatal tube-related complications were more common in pulsion intubation, but was found to be highly effective in relieving dysphagia, with shortened hospital stay (mean 6 days) and acceptable morbidity and mortality rates. These results indicate the trend towards, and the increased safety of, pulsion intubation.

Aged↗
PubMed1989

Cloning, nucleotide sequence, and hybridization studies of the type IIb heat-labile enterotoxin gene of Escherichia coli.

Type IIb heat-labile enterotoxin (LT-IIb) is produced by Escherichia coli 41. Restriction fragments of total cell DNA from strain 41 were cloned into a cosmid vector, and one cosmid clone that encoded LT-IIb was identified. The genes for LT-IIb were subcloned into a variety of plasmids, expressed in minicells, sequenced, and compared with the structural genes for other members of the Vibrio cholerae-E. coli enterotoxin family. The A subunits of these toxins all have similar ADP-ribosyltransferase activity. The A genes of LT-IIa and LT-IIb exhibited 71% DNA sequence homology with each other and 55 to 57% homology with the A genes of cholera toxin (CT) and the type I enterotoxins of E. coli (LTh-I and LTp-I). The A subunits of the heat-labile enterotoxins also have limited homology with other ADP-ribosylating toxins, including pertussis toxin, diphtheria toxin, and Pseudomonas aeruginosa exotoxin A. The B subunits of LT-IIa and LT-IIb differ from each other and from type I enterotoxins in their carbohydrate-binding specificities. The B genes of LT-IIa and LT-IIb were 66% homologous, but neither had significant homology with the B genes of CT, LTh-I, and LTp-I. The A subunit genes for the type I and type II enterotoxins represent distinct branches of an evolutionary tree, and the divergence between the A subunit genes of LT-IIa and LT-IIb is greater than that between CT and LT-I. In contrast, it has not yet been possible to demonstrate an evolutionary relationship between the B subunits of type I and type II heat-labile enterotoxins. Hybridization studies with DNA from independently isolated LT-II producing strains of E. coli also suggested that additional variants of LT-II exist.

Amino Acid Sequence↗
PubMed1973

Choice of higher density signalled shock over lower density unsignalled shock.

Unsignalled, inescapable shocks were presented to four albino rats in Experiment 1. By pressing a lever subjects could change the condition to signalled shock for 3-min periods after which unsignalled shock was automatically reinstated. All subjects changed from unsignalled to signalled shock when shock density was the same or when the density of signalled shock was two times greater than unsignalled shock. When the density of signalled shock was four times that of unsignalled shock, three subjects changed to the higher density schedule. One subject changed to a density of signalled shock eight times that of unsignalled shock. The second study showed that the two shock schedules most similar in Experiment 1 were discriminably different because subjects chose lower over higher shock densities when both densities were unsignalled. An analysis stressing safe (signal absent) and unsafe (signal present) periods was discussed.

Journal Article↗
PubMedDate not supplied

Evaluation of montelukast in 8 to 14 year old children with mild persistent asthma and compared with inhaled corticosteroids.

OBJECTIVES: To determine the clinical effectiveness, tolerability and reliability of montelukast and to compare this drug with inhaled corticosteroids. METHODS: We performed a randomized, 14-week, 2-period, prospective parallel group study. After a 2-week run-in period, patients received treatment for 12 weeks. Sixty-three clinically stable outpatients aged 8 to 14 years with a history of mild persistent asthma for at least 1 year and a forced expiratory volume in one second (FEV1) greater than 80 % of the predicted value were evaluated. RESULTS: Montelukast produced improvement in airway obstruction, daily symptom scores, total daily as-needed beta-agonist use, nocturnal awakenings, percentage of days and percentage of patients with asthma exacerbations, and urinary leukotriene E4 levels. These beneficial effects were similar to those produced by inhaled corticosteroids. There were no significant adverse effects requiring treatment discontinuation. CONCLUSIONS: Montelukast may be a well-tolerated and effective therapeutic option in 8 to 14-year-old patients with mild persistent asthma.

Acetates↗
PubMedDate not supplied

Comparison of growth, serum prealbumin, transferrin, IgG and amino acids of term infants fed breast mild or formula.

This study was designed to compare growth parameters, biochemical indices of protein metabolism and serum amino acid patterns in newborn infants fed either human milk (n: 22) or formula with protein and amino acid concentrations similar to human milk (n: 19) during the first two months of life. Growth parameters were normal and similar in all infants. Serum levels of transferrin and IgG were not significantly different, whereas prealbumin concentrations were found to be significantly higher in infants fed formula compared to those fed human milk. In the formula group, glutamic acid and cystine levels were significantly lower while phenylalanine and proline were significantly higher compared to the breastfed group. It was observed that feeding a formula with an amino acid pattern similar to that of human milk does not necessarily give rise to identical patterns of amino acids or indices of protein metabolism.

Amino Acids↗