Search PubMed⌕ Search

Biomedical subjects

R King

Publications and source records attributed to R King.

At least 19 recordsLinked to original sources
PubMed1995

Limited sequence diversity of the HIV type 1 protease gene from clinical isolates and in vitro susceptibility to HIV protease inhibitors.

Proviral DNAs from 3 laboratory strains and 21 clinical isolates of HIV-1 were extracted from infected cells after proteinase K digestion and the protease gene was PCR amplified and sequenced directly by the Sanger method. In vitro susceptibilities of the virus isolates to protease inhibitors were determined by the ACTG/DoD consensus assay. Four different HIV protease inhibitors were tested including P9941, a C2 symmetrical diol (Du Pont-Merck); A80987, an asymmetric mono-ol (Abbott); XM323, a cyclic urea (Du Pont-Merck); and Ro31-8959, an asymmetric hydroxyethylene isostere (Roche). Maximum sequence variation was 10% at both the nucleic and amino acid levels. Purine-purine substitutions were most common. Five noncontiguous regions were conserved across all isolates and corresponded to amino acids 1-9 (amino terminal), 21-32 (catalytic site), 47-56 ("flap" region), 78-88 (substrate-binding region), and 94-99 (carboxy terminal). All clinical isolates demonstrated in vitro susceptibility to the protease inhibitors. There was no significant difference between the susceptibility of the reference strains and the clinical isolates. These data suggest that the variable regions of protease do not contain sites that are important for interactions with the inhibitors tested.

Amino Acid Sequence↗
PubMed1995

Couple communication, sexual coercion and HIV risk reduction in Kigali, Rwanda.

OBJECTIVE: To describe sexual interaction and HIV-related communication in Rwandan couples and to examine their relationship to HIV testing and condom use. STUDY DESIGN: Cross-sectional survey of a longitudinal cohort. METHODS: In 1988, women recruited for an epidemiological study of HIV, and interested male partners, received confidential HIV testing and counseling. Two years after enrollment, 876 women reporting one steady partner in the past year completed a questionnaire addressing sexual and HIV-related communication, sexual motivation and violence in the partnership. RESULTS: Men control sexual decision making, and coercive sex and violence between partners is not uncommon. HIV-positive women were more likely to report coercive sex and less likely to have discussed their test results with their partner. Women with HIV-positive partners were more likely to report being physically abused. Condom use was more common if the man had been previously tested, and if women reported discussing or negotiating condom use. HIV-negative women with untested or seronegative partners were the least likely to use condoms or to discuss or attempt to negotiate condom use. CONCLUSIONS: Participation of the male partner is crucial for successful HIV risk reduction in couples. HIV testing and counseling of couples has beneficial long term effects on condom use and HIV-related communication. Couple communication is associated with condom use, but only when the discussion is specific (sexually transmitted disease risks and using condoms). Seronegative women with untested partners are at increased risk for HIV as they are the least likely to discuss or attempt to negotiate condom use.

Coercion↗
PubMed1994

Secretion of eukaryotic growth hormones in Escherichia coli is influenced by the sequence of the mature proteins.

We report the construction of secretion plasmids expressing the fusion proteins, OmpA::pGH (pSpGH.01) and OmpA::hGH (phGH.01), and compare the secretion of mature porcine growth hormone (pGH) and human growth hormone (hGH) employing Escherichia coli. E. coli [phGH.01] secreted 10-15 micrograms hGH/ml/A600 cells into the periplasmic space, representing 30% of total periplasmic proteins. E. coli [pSpGH.01], however, secreted 30-fold less mature pGH. On the basis that both pSpGH.01 and phGH.01 are stably maintained in E. coli and in vitro transcription/translation data showed equivalent expression of OmpA::pGH and OmpA::hGH precursors, we attribute the higher secretion of hGH to the translocation-competent OmpA::hGH protein configuration. Two OmpA::GHF (growth hormone fusion) precursors, OmpA::GHF.02 and OmpA::GHF.03, both with hGH helix 3/helix 4 together instead of the pGH equivalent, secreted mature proteins as efficiently as OmpA::hGH. We propose that hGH helices 3 and 4 in these OmpA::GHF precursors play a major role in the folding of the precursor to a translocation-competent state, mimicking the translocation-competent nature of the OmpA::hGH precursor.

Animals↗
PubMed1994

Community prevalence of hepatitis C viraemia: a polymerase chain reaction study.

In order to estimate the prevalence of HCV carriage in an inner city health district, we undertook a polymerase chain reaction (PCR) based survey of sera collected from 1,0002 patients attending general practitioners for reasons unrelated to liver disease. The series comprised 305 sample selected sera patients sample from sera 995 patients previously screened by C100 antigen-based anti-HCV tests. Overall, 7 patients were positive for HCV RNA. Four cases had anti-C100 antibodies to HCV, 2 were strictly negative but had high-normal/borderline optical densities by ELISA assay, while one was completely anti-HCV negative. All but one had normal liver function tests. Only 3/7 PCR positive cases had any serum marker for hepatitis B (HBV) exposure (2 HBsAg positive, 1 IgM anti-HBc positive). The minimum point prevalence of HCV carriage in this community is 0.7%, approximating the HBsAg carriage in the same population (1%). HCV carriage in this inner city population is considerably higher than would be predicted by blood donor surveys. A positive anti-HCV anti-body (anti-C100) test is poorly predictive (approximately 10%) of HCV RNA carriage in a general practice based population in which measurement of "surrogate" (HBV related) HCV markers would have detected only 3/7 cases of presumed chronic HCV carriage.

Adult↗
PubMed1994

The mouse pink-eyed dilution gene: association with hypopigmentation in Prader-Willi and Angelman syndromes and with human OCA2.

Mutations at the mouse pink-eyed dilution locus, p, cause hypopigmentation. We have cloned the mouse p gene cDNA and the cDNA of its human counterpart, P. The region of mouse chromosome 7 containing the p locus is syntenic with human chromosome 15q11-q13, a region associated with Prader-Willi syndrome (PWS) and Angelman syndrome (AS), both of which involve profound imprinting effects. PWS patients lack sequences of paternal origin from 15q, whereas AS patients lack a maternal copy of an essential region from 15q. However, the critical regions for these syndromes are much smaller than the chromosomal region commonly deleted that often includes the P gene. Hypopigmentation in PWS and AS patients is correlated with deletions of one copy of the human P gene that is highly homologous with its mouse counterpart. A subset of PWS and AS patients also have OCA2. These patients lack one copy of the P gene in the context of a PWS or AS deletion, with a mutation in the remaining chromosomal homologue of the P gene. Mutations in both homologues of the P gene of OCA2 patients who do not have PWS or AS have also been detected.

Albinism, Oculocutaneous↗
PubMed1993

Interferon-alpha therapy with and without interferon-alpha priming in patients with chronic hepatitis B infection.

To determine whether a priming course of lymphoblastoid interferon-alpha (IFN-alpha) enhances the efficacy of subsequent IFN-alpha therapy in the treatment of chronic hepatitis B, a randomized trial was conducted to compare IFN-alpha priming (IFN-alpha for one month; no treatment for one month) followed by IFN-alpha therapy for three months, with IFN-alpha therapy (10 MU thrice-weekly) given for three months. Thirty-seven patients seropositive for more than six months for HBsAg, HBeAg and HBV DNA, and with histological evidence of active liver inflammation, were recruited. Eight patients (40%) treated with a priming course of IFN-alpha responded to subsequent IFN-alpha therapy for three months with loss of HBV DNA and HBe seroconversion. This compared with five patients (29%), treated only with IFN-alpha therapy for three months, who lost HBV DNA and HBeAg (but only two [12%] developed anti-HBe). IFN-alpha was well tolerated, with only three patients withdrawing from the study because of 'flu'-like symptoms or inconvenience in the early phase. The better response, although not significant, may suggest a place for a short priming course of IFN-alpha in addition to the current IFN-alpha treatment regimen.

Adult↗
PubMed1992

Effect of temperature and medium composition on mycelial growth of Streptomyces tendae in submerged culture.

To investigate the influence of culture conditions on growth of filamentous bacteria in submerged culture, S. tendae was cultivated at various temperatures and in various media. For this purpose, a temperature-controlled growth chamber was constructed, which allows the cultivation of filamentous bacteria and fungi oxygen saturated medium. To observe the development of mycelia emerging from spores, this growth chamber was mounted on a microscope stage and series of images were analyzed by an image processing system. Growth kinetics obtained in liquid culture were identical to those determined on solid media. Specific growth rate and apical extension rates of individual hyphae seemed to be higher than those observed on solid media, due to a better supply of medium in submerged culture. A two-fold increase in specific growth rate, mean apical extension rate and branching rate was observed when the temperature was increased from 27 degrees C to 37 degrees C, therefore, the length of the hyphal growth unit was not changed. Growth in synthetic media used here was considerably slower compared with complex medium. A decrease in glucose concentration from 40.0 g l-1 to 1.0 g l-1 resulted in an increase in branching rate and specific growth rate, while apical extension rate of individual hyphae was unchanged.

Bacteriological Techniques↗
PubMed1992

Nutritional control of nikkomycin and juglomycin production by Streptomyces tendae in continuous culture.

Continuous cultures with Streptomyces tendae revealed some interesting facts. In a continuous culture running for more than 2500 h the production of either nikkomycines or juglomycins could be selected by varying the feed composition. Decreasing the phosphate supply in the feed broth from the initial concentration of 2.5 mM to 1.0 mM enhanced the productivity of nikkomycins and decreased the productivity of juglomycins. When switching back to the initial conditions of the experiment after 2000 h nearly the same production behaviour as at the beginning of the fermentation could be observed. This indicated a stable behaviour of the population with regard to nikkomycin productivity. The long continuous fermentation showed the ability of S. tendae Tü 901/8c to produce nikkomycin at a high level for at least 1500 h. In a second continuous culture it was shown that the productivity of the nikkomycins and juglomycins decreased and increased, respectively, with increasing dilution rate. Comparing batch cultures with continuous fermentations, higher juglomycin productivity was found in the latter. These facts indicate that the strain responds to complex interacting physiological controls, by producing either nikkomycins or juglomycins in a higher amount.

Aminoglycosides↗
PubMed1992

Production and characterization of recombinant insulin-like growth factor-I (IGF-I) and potent analogues of IGF-I, with Gly or Arg substituted for Glu3, following their expression in Escherichia coli as fusion proteins.

The development of an efficient expression system for insulin-like growth factor-I (IGF-I) in Escherichia coli as a fusion protein is described. The fusion protein consists of an N-terminal extension made up of the first 46 amino acids of methionyl porcine GH ([Met1]-pGH) followed by the dipeptide Val-Asn. The latter two residues provide a unique hydroxylamine-sensitive link between [Met1]-pGH(1-46) and the N-terminal Gly of IGF-I. Downstream processing of the fusion proteins involved isolation of inclusion bodies, cleavage at the Asn-Gly bond, refolding of the reduced IGF-I peptide and purification to homogeneity. This expression system was also used to produce two variants of IGF-I in which Glu3 was substituted by either Gly or Arg to give [Gly3]-IGF-I and [Arg3]-IGF-I respectively. Production of milligram quantities of IGF-I peptide was readily achieved. The purity of the IGF-I, [Gly3]-IGF-I and [Arg3]-IGF-I was established by high-performance liquid chromatography and N-terminal sequence analysis. [Gly3]-IGF-I and [Arg3]-IGF-I were more potent than IGF-I in biological assays measuring stimulation of protein synthesis and DNA synthesis or inhibition of protein breakdown in rat L6 myoblasts. Both analogues bound very poorly to bovine IGF-binding protein-2 and slightly less well than IGF-I to the type-1 receptor on rat L6 myoblasts. We conclude that reduced binding to IGF-binding proteins rather than increased receptor binding is the likely explanation for the greater biological potency of the analogues compared with IGF-I.

Amino Acid Sequence↗