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Biomedical subjects

D S Jones

Publications and source records attributed to D S Jones.

At least 91 records · Page 5Linked to original sources
PubMed1989

The effect of specific mutations at and around the gag-pol gene junction of Moloney murine leukaemia virus.

By carrying out oligonucleotide-directed mutagenesis, in vitro, on a 3.3 kb XhoI-HindIII fragment from Moloney murine leukaemia virus Mo-MuLV proviral DNA, inserted into the phagemid pTZ19R, nine separate fragments have been prepared in which mutations have been inserted at and around the gag-pol gene junction. Using these mutant fragments Mo-MuLV proviral DNA has been reassembled and cloned into pBR322. Examination of the mutant proviral DNAs in mouse culture cells indicates that a terminator codon at the gag-pol junction is essential for function, but any of the three chain terminator codons gives an active virus. Also the region of secondary structure surrounding the terminator codon must be preserved.

Amino Acid Sequence↗
PubMed1988

Concentrations of oxytocin-neurophysin prohormone mRNA in corpora lutea of sheep during the oestrous cycle and in early pregnancy.

Concentrations of oxytocin in corpora lutea from pregnant and non-pregnant sheep rose during luteinization to peak between days 5 and 9 after oestrus before falling to low levels on days 12 and 14. Concentrations of the 608-base mRNA encoding the oxytocin-neurophysin prohormone, measured by Northern blotting using a cRNA probe, were highest before day 5, and fell to low levels by day 9. The decline in oxytocin during the second half of the oestrus cycle and in pregnancy could therefore be accounted for by reduced luteal concentrations of oxytocin-neurophysin mRNA. The rate of decline in prohormone mRNA concentration between days 3 and 16 followed first order kinetics, suggesting that gene expression ceased early in the cycle. The lag between peak oxytocin-neurophysin mRNA and peak oxytocin concentrations may represent the time taken for post-translational processing of the prohormone.

Animals↗
PubMed1987

On the statistical evaluation of adherence assays.

Parametric (unpaired t-test) and non-parametric (Mann-Whitney U-test) methods have been used in the evaluation of adherence assays on the non-antibiotic antimicrobial agent, Taurolin. In all but one case, where the anti-adherence effect was known to be marginal, both statistical methods gave similar results although there were some minor differences in the levels of significance achieved. The effect of the agent on the deviation of adherence data from normality was quantified by calculation of the skewness coefficient for each data set. A significant anti-adherence effect appears to result in a decrease in the skewness of the adherence assay data. It was concluded that either parametric or non-parametric statistical evaluation of adherence assay data is valid for large numbers of observations. In future studies of this type it is suggested that attention should also be given to the effect of the anti-adherence agent on the deviation of adherence data from normality as denoted by the skewness coefficient.

Adhesiveness↗
PubMed1987

The sporicidal activity and inactivation of chlorhexidine gluconate in aqueous and alcoholic solution.

The sporicidal activity of chlorhexidine gluconate in aqueous and alcoholic solution against spores of Bacillus subtilis was examined over a broad temperature range. Activity was not observed at 20 degrees C even with concentrations as high as 10% chlorhexidine. Temperatures of 37 degrees-70 degrees C in combination with such high concentrations were required for reductions in spore viability. No viable spores were recoverable after 4 h contact at 55 degrees C with 10% aqueous chlorhexidine and none after 3 h contact with the alcoholic solution. Because of the high concentrations necessary for activity and the possibility of sporostasis occurring from inefficient chlorhexidine inactivation, existing inactivation systems were examined and modified to obtain satisfactory results. The spores of other Bacillus species examined (B. cereus, B. megaterium and B. stearothermophilus) proved to be considerably less resistant than those of B. subtilis. Presence of organic matter had little effect on the activity.

Bacillus subtilis↗
PubMed1987

Reduced adherence of micro-organisms to human mucosal epithelial cells following treatment with Taurolin, a novel antimicrobial agent.

Taurolin, a non-antibiotic antimicrobial agent, significantly reduced the adherence of buccal and vaginal strains of Candida albicans blastospores and urine isolates of Escherichia coli and Staphylococcus saprophyticus to epithelial cells. Light microscopy and radio-isotopic counting methods were used to quantify the adherence of the micro-organisms to either uroepithelial or buccal epithelial cells. A maximum reduction in adherence of approximately 65% was obtained. The anti-adherence capacity was time-dependent, requiring a contact time of 30 min to achieve maximum effect. Taurolin at sub-minimum inhibitory concentrations (MIC) significantly reduced the adherence of Candida and E. coli. A concentration slightly higher than the MIC was required for Staph. saprophyticus. Treatment of either epithelial cells or micro-organisms with Taurolin resulted in reduced adherence of microorganisms.

Anti-Bacterial Agents↗
PubMed1987

A comparative study of the microbial antiadherence capacities of three antimicrobial agents.

The antimicrobioal agents, taurolidine, chlorhexidine and povidone-iodine were examined for microbial anti-adherence activity. Two adherence systems were investigated using light microscopic and radio-isotopic assay methods: that of an oral isolate of Candida albicans to human buccal epithelial cells and of a urine isolate of Escherichia coli to human uroepithelial cells. Each of the three agents exhibited significant anti-adherence activity which was concentration dependent. The activity was expressed at subminimum inhibitory concentrations of the agents. Treatment of either the microbial or epithelial cells resulted in significant reductions in adhering micro-organisms. Consideration of the data in respect of the skewness coefficient and percentage clear epithelial cells indicated that the agents exhibited a broadly based anti-adherence capacity.

Anti-Bacterial Agents↗
PubMed1986

The nucleotide sequence of Scenedesmus obliquus chloroplast elongator methionine-accepting tRNA.

The chloroplast elongator methionine-accepting tRNA from the green alga Scenedesmus obliquus was purified and and its nucleotide sequence determined. The sequence does not bear close homology to higher-plant chloroplast tRNAMetm species, nor to the chloroplast tRNAMetm species from Euglena gracilis. This tRNA is unique among all tRNAs in having pseudouridine at position 8, and this has implications with regard to the proposed interaction of aminoacyl-tRNA synthetases with their cognate tRNAs at this position. The primary sequence of the tRNA is: pG-C-C-U-G-C-U-psi-A-G-C-U-C-A-G-U-D-Gm- G-C-C-A-G-A-G-C-A-U-C-C-G-psi-psi-U-C-A-U-m2A-C-G-C-G-G-A-A-A- m7G-D-C-A-C-U-A-G-T-psi-C-G-A-A-U-C-U-A-G-U-A-G-C-A-G-G-C-A-C-C-A-OH.

Base Sequence↗
PubMed1986

The nucleotide sequence of a cytoplasmic tRNAPhe from Scenedesmus obliquus and comparison with a tRNATyr species.

The nucleotide sequence of a cytoplasmic tRNAPhe from the eukaryotic green alga Scenedesmus obliquus was determined as: pG-G-C-U-U-G-A-U-A-m2G-C-U-C-A-G-C-D-Gm-G-G-A-G-A-G-C-m22G-p si-psi-A-G-A-Cm-U-G - A-A-m1G-A-psi-C-U-A-C-A-G-m7G-N-m5C-C-C-C-A-G-T-psi-C-G-m1A-U-m5C-Cm-U-G -G-G-U- C A-G-G-C-C-A-C-C-A-OH. The structure has some notable features. Unlike other tRNAPhe species from plant sources, it has an unmodified G as the first residue of the anticodon and m1G rather than a Y derivative as the residue following the anticodon. The sequence m5C(60)-Cm(61) is unique to this tRNA. The sequence of S. obliquus tRNAPhe shows close homology with S. obliquus tRNATyr.

Base Sequence↗
PubMed1986

Glucocorticoid-induced insulin resistance in vitro: inhibition of insulin-stimulated methylaminoisobutyric acid uptake.

We have previously developed an in vitro model for the induction of insulin resistance by glucocorticoids using 3T3-L1 fat cells (Grunfeld, Baird, Van Obberghen and Kahn 1981). In this model, glucocorticoid treatment was shown to decrease insulin binding and inhibit the acute stimulation of deoxyglucose uptake by insulin. We now extend the findings in this model to examine insulin stimulated methylaminoisobutyric acid (MAIB) uptake, an event whose expression requires m-RNA and protein synthesis and takes many hours. As previously seen with insulin stimulation of deoxyglucose uptake, one day of exposure to dexamethasone had little effect on insulin stimulation of MAIB uptake. Significant inhibition of insulin-stimulated MAIB uptake was seen after 2 days of exposure, and 3 days were required for the maximum effect of the glucocorticoid. The half-maximal concentration of dexamethasone required for inhibition was 1.6 nM. Exposure to dexamethasone produced a 57% decrease in the maximal response to insulin and a small but consistant shift in the sensitivity to insulin. As seen with the acute effects of insulin, the major locus of glucocorticoid action in inhibiting insulin stimulated MAIB uptake is also after the binding of insulin to its receptor. These data indicate that the inhibitory effects of glucocorticoids on insulin action in fat cells extend to those effects of insulin which require gene expression and are not merely limited to short-term metabolic actions of insulin.

Adipose Tissue↗