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Biomedical subjects

J M Webster

Publications and source records attributed to J M Webster.

At least 37 records · Page 2Linked to original sources
PubMed1995

Adenosine effects upon insulin action on lipolysis and glucose transport in human adipocytes.

The dose response effect of a new adenosine analogue, GR79236 (N-[1S trans-2-hydroxycyclopentyl] adenosine) upon insulin sensitivity was examined in human adipocytes. The influence of adenosine upon insulin sensitivity for suppression of lipolysis and stimulation of glucose transport was examined. Removal of adenosine by use of adenosine deaminase stimulated lipolysis to the same extent as did 10(-9) M noradrenaline. GR79236 brought about dose dependent inhibition of lipolysis with half-maximal effect at 11.3 +/- 7.8 x 10(-9) M. When lipolysis was stimulated by noradrenaline alone the subsequent inhibition of lipolysis brought about by GR79236 was significantly greater than that of insulin. To examine adenosine effects on the insulin signalling pathway separately from those on lipolysis, the insulin sensitivity of glucose transport was examined. Removal of adenosine brought about a small but significant increase in the concentration of insulin required for half-maximal stimulation of glucose transport. Adenosine agonists offer promise as new agents for the modulation of metabolism in diabetes and other states of insulin resistance.

3-O-Methylglucose↗
PubMed1995

Holographic imaging of human brain preparations--a step toward virtual medicine.

BACKGROUND: Holography is the only technique that can record the full tri-dimensional quality of an object, and allow the observer to easily see this as an image that is truly 3-D. The pulsed laser can capture even a moving object's three dimensional form as a hologram because of its short wavelength. METHODS: Using a modification of the Klinger processing sequence, formalin-fixed human brains were subjected to periods of freezing and thawing. This assisted the visual demarcation between white and gray matter during neuroanatomical dissection. Holographic methodology with the Lumonic HLS2 pulsed ruby laser was employed to create three dimensional images from brain preparations. RESULTS: Master holograms of the human brain preparations demonstrating the various pathways such as vision, cortico-spinal, etc. are made using the ruby laser at wavelength 694.3 nanometers. From this master an infinite number of holograms can be copied. CONCLUSION: By providing immediate three dimensional information, holograms uniquely facilitate the spontaneous understanding of human neuroanatomical relationships which cannot be as efficiently learned with photographs or diagrams. This points the way toward future educational and biomedical applications of this emerging technology.

Brain↗
PubMed1995

Antimicrobial metabolites from a bacterial symbiont.

Two types of antibiotics, namely, indoles and dithiolopyrrolones, have been isolated and identified from Xenorhabdus bovienii A2. Compounds 1 and 2 showed strong activity against Cryptococcus neoformans, compounds 3 and 4 showed strong activity against Botrytis cinerea, and compounds 1, 3, and 4 showed significant activity against Phytophthora infestants (2 was not tested). In addition, two lower homologues of xenorhabdins 5 and 6, namely, 6-(N-3'-methylbutanamido)-4,5-dihydro-1,2-dithiolo[4,3-b]pyr rol-5- one [7] and 6-(N-butanamido)[4,5-dihydro-1,2-dithiolo[4,3-b]pyrrol-5-one [8], have been isolated and characterized for the first time.

Animals↗
PubMed1995

Identification of two pigments and a hydroxystilbene antibiotic from Photorhabdus luminescens.

Two yellow pigments were isolated for the first time from the entomopathogenic bacterium Photorhabdus luminescens in liquid culture and were identified as the anthraquinone derivatives 3,8-dimethoxy-1-hydroxy-9,10-anthraquinone (minor) and 1,3-dimethoxy-8-hydroxy-9,10-anthraquinone (major). A known antibiotic, 3,5-dihydroxy-4-isopropylstilbene, was also detected and for the first time showed strong fungicidal activity against several fungi of medical and agricultural importance.

Anthraquinones↗
PubMed1994

Stability and Activities of Antibiotics Produced during Infection of the Insect Galleria mellonella by Two Isolates of Xenorhabdus nematophilus.

Xenorhabdus nematophilus subsp. dutki, an entomopathogenic bacterium, is vectored by steinernematid nematodes into insects, where it produces broad-spectrum antibiotics. The use of the nematode-bacterium complex against soil-dwelling pest insects could introduce antibiotics into the soil via the dead insect fragments during the emergence phase of the nematodes. Studies on the stability and activities of these antibiotics produced in the insect Galleria mellonella may contribute to assessing the possible impact of antibiotics on soil bacteria. Two isolates of X. nematophilus subsp. dutki (isolates GI and SFU) produced xenocoumacins 1 and 2 in cadavers of G. mellonella larvae in a 1:1 ratio. Total xenocoumacin 1 and 2 production was 800 ng/200 mg (wet weight) of insect tissue for the GI isolate. Antibiotic activity of water extracts from insects that had been infected with X. nematophilus was stable at 60 degrees C for 1 h and after repeated freeze-thaw cycles. The antibiotic titer of extracts held at 27 degrees C declined by day 10. The spectrum of bacterial species killed by antibiotics produced in insect cadavers varied with the isolate of X. nematophilus. Levels of antibiotic activity were greater in vivo than in tryptic soy broth, which may represent a nutrient effect. The bacterial isolate, culture condition, and presence of nematodes influenced the total antibiotic production in vivo. However, the levels of activity were not correlated with bacterial levels in the different growth environments. Insect cadavers with antibiotic activity transiently lowered the numbers of the bacteria in the soil, the extent of decline varying with the strain of X. nematophilus and the time of sampling.

Journal Article↗
PubMed1993

The impact of metformin therapy on hepatic glucose production and skeletal muscle glycogen synthase activity in overweight type II diabetic patients.

The effect of metformin therapy on glucose metabolism was examined in eight overweight newly presenting untreated type II diabetic patients (five males, three females). Patients were treated for 12 weeks with either metformin (850 mg x 3) or matching placebo using a double-blind crossover study design; patients were studied at presentation and at the end of each treatment period. Insulin action was assessed by measuring activation of skeletal muscle glycogen synthase (GS) before and during a 4-hour hyperinsulinemic euglycemic clamp (100 mU.kg-1 x h-1). Metformin therapy was associated with a significant decrease in fasting blood glucose (6.8 +/- 0.6 v 8.3 +/- 0.9 mmol.L-1, P < .01) and glycosylated hemoglobin ([HbA1] 7.7% +/- 0.4% v 8.5% +/- 0.5%, P < .01) levels. Fasting hepatic glucose production (HGP) was also significantly decreased following metformin therapy (1.98 +/- 0.13 v 2.41 +/- 0.20 mg.kg-1 x min-1, P < .02), whereas fasting insulin and C-peptide concentrations remained unaltered. The decrease in basal HGP correlated closely with the decrease in fasting blood glucose concentration (r = .92, P < .001). Insulin-stimulated glucose uptake was assessed using the hyperinsulinemic euglycemic clamp technique and was increased post-metformin (3.8 +/- 0.6 v 3.1 +/- 0.7 mg.kg-1 x min-1, P < .05). This was primarily the result of increased nonoxidative glucose metabolism (1.1 +/- 0.6 v 0.4 +/- 0.6 mg.kg-1 x min-1, P < .05); oxidative glucose metabolism did not change. Metformin had no measurable effect on insulin activation of skeletal muscle GS, the rate-limiting enzyme controlling muscle glucose storage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Docking of dogs.

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Animal Welfare↗
PubMed1992

Docking of dogs.

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Animals↗
PubMed1988

Unusual sequences, homologous to 5S RNA, in ribosomal DNA repeats of the nematode Meloidogyne arenaria.

There are sequences homologous to 5S ribosomal RNA in the ribosomal DNA (rDNA) repeats of the plant-parasitic nematode Meloidogyne arenaria. This is surprising, because in all other higher eukaryotes studied to date, the genes for 5S RNA are unlinked to and distinct from a tandem rDNA repeat containing the genes for 18S, 5.8S, and 28S ribosomal RNA. Previously, only prokaryotes and certain "lower eukaryotes" (protozoa and fungi) had been found to have both the larger rRNAs and 5S rRNA represented within a single DNA repeat. This has raised questions on the organization of these repeats in the earliest cell (progenote), and on subsequent evolutionary relationships between pro- and eukaryotes. Evidence is presented for rearrangements and deletions within Meloidogyne rDNA. The unusual life cycles (different levels of ploidy, reproduction by meiotic and mitotic parthenogenesis) of members of this genus might allow rapid fixation of any variants with introduced 5S RNA sequences. The 5S RNA sequences in Meloidogyne rDNA may not be expressed, but their presence raises important questions as to the evolutionary origins and stability of repeat gene families.

Animals↗
PubMed1984

Factors influencing the success of in vitro fertilization for alleviating human infertility.

The program for in vitro fertilization at Bourn Hall began in October 1980. Various types of infertility have been treated during this time using the natural menstrual cycle or stimulation of follicular growth with antiestrogens and gonadotrophins. Follicular growth and maturation are assayed by urinary estrogens and LH, monitored regularly during the later follicular stage. Many patients had an endogenous LH surge; others needed an injection of HCG to induce ovulation. All oocytes were recovered by laparoscopy. Wide variations occurred in the time interval between the start of the LH surge and oocyte recovery and between oocyte recovery and insemination. Embryos taken between the one- and the eight-cell stage were replaced into their mother, no standard procedure being adopted for all patients. The results of all treatments including patient's responses during the follicular and luteal phases, oocyte recovery, fertilization, cleavage, replacement, implantation, abortion, and birth and the effect of factors such as replacing two or more embryos, maternal age, and previous obstetric history are described in detail. The incidence of implantation after embryo replacement improved from 16.5% initially to 30% currently. More than 118 babies have been born, and many pregnancies are continuing.

Abortion, Spontaneous↗
PubMed1982

Conductivity studies of suspension systems in different states of aggregation.

The electrical conductivity effects of dispersed, coagulated, and flocculated systems were investigated using sulfamerazine powder, an insoluble, hydrophobic drug to prepare the suspension systems. For the dispersed systems, a peak in conductivity was observed at a drug concentration between 5 and 15%. The critical coagulating concentration was defined as the concentration of drug at which a maximum in specific conductance was observed. At this concentration, a maximum number of charged particles were in the system. Coagulated suspensions showed higher conductance values than the dispersed systems at equivalent concentrations; however, the critical coagulating concentration value appeared to be the same. For flocculated suspensions there was an increase in conductance with drug concentration with no perceptible peak conductance value.

Chemistry, Pharmaceutical↗