Biomedical subjects

R Sharp

Publications and source records attributed to R Sharp.

51 records · Page 3Linked to original sources

PubMed1992

Growth and Survival of Genetically Manipulated Lactobacillus plantarum in Silage.

The growth and persistence of two genetically manipulated forms of Lactobacillus plantarum NCDO (National Collection of Dairy Organisms) 1193 have been monitored in grass silage. Both recombinants contained pSA3, a shuttle vector for gram-positive organisms that encodes erythromycin resistance. In one of the recombinants, pSA3 was integrated onto the chromosome, whereas in the other, a pSA3 derivative designated pM25, which contains a Clostridium thermocellum cellulase gene cloned into pSA3, was maintained as an extrachromosomal element. This extrachromosomal element is a plasmid. Rifampin-resistant mutants were selected for the recombinants and the parent strain. When applied to minisilos at a rate of 10 CFU/g of grass, both the recombinants and the parent strain proliferated to dominate the epiphytic microflora and induced an increase in the decline in pH compared with that of the noninoculated silos. The presence of extra genetic material did not appear to disadvantage the bacterium in comparison with the parent strain. The selective recovery of both strains by using rifampin and erythromycin was confirmed by Southern hybridization. Interestingly, the free plasmid (pM25) appeared more stable in silage than was expected from studies in MRS broth. The plasmid was retained by 85% of the rifampin-resistant L. plantarum colonies isolated from a day 30 silo. These data answer an important question by showing that genetically manipulated recombinants of L. plantarum can proliferate and compete with epiphytic lactic acid bacteria in silage.

Journal Article↗

PubMed1992

Hypertrophic gastropathy resembling Ménétrier's disease in transgenic mice overexpressing transforming growth factor alpha in the stomach.

Transforming growth factor alpha (TGF alpha) is thought to participate in the normal and pathologic processes of numerous tissues, including the gastric mucosa. To explore its role in vivo, transgenic mice were generated overexpressing TGF alpha in the stomach. TGF alpha induced dramatic structural and functional lesions of the glandular stomach that were similar to Ménétrier's disease in humans. Transgenic mice developed severe adenomatous hyperplasia that resulted in a striking nodular thickening or hypertrophy of the gastric mucosa. Secretions obtained from affected stomachs contained no detectable gastric acid, suggesting that parietal cell function had been greatly impaired. These findings demonstrate that overproduction of TGF alpha can stimulate cellular proliferation, suppress acid secretion, and perturb organogenesis of the stomach of transgenic mice. Moreover, TGF alpha may contribute to the pathogenesis of related human hypertrophic gastropathies, such as Ménétrier's disease.

Animals↗

PubMed1990

Transduction of a plasmid containing the bacteriophage D3 cos site in Pseudomonas aeruginosa.

Plasmids harboring the cos sequences of bacteriophage D3 can be transferred, by bacteriophage D3, into Pseudomonas aeruginosa by a mechanism which is insensitive to DNase. Transducing activity was separated from the plaque-forming particles by CsCl equilibrium gradient centrifugation. Restriction endonuclease digestion patterns suggest that the transducing particles contain plasmid concatemers.

Bacteriophages↗

PubMed1989

The effects of a mother's second pregnancy on the firstborn child.

Mothers in the last trimester of the second pregnancy admit to being less active, more tired and moody than previously. Many were more anxious than usual. Their first child frequently showed behavioural changes. Those surveyed were between 1 1/2 and 4 years of age and showed more clinging, sleep disturbance and misbehaviour with tantrums than expected. It is presumed that the mother's pregnancy induces anxiety in her child with consequent behavioural changes.

Anxiety↗

PubMed1986

Diagnostic utility of lymphocyte subset analysis in AIDS case finding.

Abnormalities of lymphocyte subsets, especially low absolute number of helper T cells, are characteristically present in acquired immune deficiency syndrome (AIDS). Similar abnormalities can be found in patients with persistent generalized lymphadenopathy (PGL) or AIDS-related complex (ARC) and, to a lesser degree, in asymptomatic people who have been exposed to human T-lymphotropic virus type III (HTLV-III). Nevertheless, there appears to be a widespread perception that lymphocyte subset analysis may be useful in AIDS case finding within high-risk groups. We evaluated the diagnostic utility of absolute number of helper T cells and ratio of helper to suppressor T cells in 33 patients with AIDS, 43 patients with PGL who had been referred for lymph node biopsy, 90 patients with PGL and 195 male homosexual controls. At conventional cutoff levels the tests did not appear to revise the probability of AIDS upward to any clinically significant degree when the pretest probability of AIDS was low. Lymphocyte subset analysis does not appear to be a cost-effective method of AIDS case finding in identified groups at risk in which the prevalence of AIDS is low.

Acquired Immunodeficiency Syndrome↗

PubMed1986

Image tracking observed with a pupil-centring device.

A brief report is given of some observations made during an extended investigation into the subjective image quality of telescopes. For part of the work, a device was required that would indicate directly to an observer the accuracy of eye position, both laterally and longitudinally, with respect to an artificial pupil. This device is described. During use it was observed that the point image produced by the device approximately tracked the eye rotation. This unanticipated property is explained and a different optical arrangement is suggested in order to exploit and enhance this tracking property. The reason for drawing attention to the technique is not only that there may be similar situations in which such devices may be used but also that the tracking property may have other applications, perhaps in a teaching or clinical context.

Cornea↗

PubMed1985

Gastrointestinal tuberculosis. The great mimic still at large.

Gastrointestinal tuberculosis has declined markedly in frequency since the introduction of antituberculous therapy. As a result, the diagnosis is often delayed in North American patients. Segmental colonic disease, especially in the absence of pulmonary tuberculosis, is often difficult to differentiate from Crohn's disease or a neoplasm. We describe a case of colonic tuberculosis mimicking carcinoma of the hepatic flexure of the colon.

Barium Sulfate↗

PubMed1983

Leg muscle pH following sprint running.

In an effort to compare the disturbances in leg muscle pH during sprint running, muscle biopsies were obtained from the gastrocnemius and vastus lateralis muscles of six healthy men (three endurance-trained and three nonendurance-trained) before and after a treadmill sprint run (TSR) to fatigue (54-105 s) at roughly 125% of their aerobic capacities. Following the TSR, repeated blood samples were taken from a hand vein and later analyzed for pH, PCO2, and lactic acid (HLa). The muscle specimens were analyzed in duplicate for pH and HLa. Resting-muscle pH was 7.03 +/- 0.02 (means +/- SE) and 7.04 +/- 0.01 for the gastrocnemius and vastus lateralis muscles, respectively. At the termination of the TSR, the pH in these muscles was 6.88 +/- 0.05 and 6.86 +/- 0.03, respectively. After a 400-m timed run on the track, the pH in the gastrocnemius of four of the subjects averaged 6.63 +/- 0.03, while blood pH and HLa were 7.10 +/- 0.03 and 12.3 mM, respectively. Although no differences in pH and HLa were observed between the vastus lateralis and gastrocnemius muscles at the end of the treadmill trial, it is speculated that the lesser disturbance in acid-base balance seen in endurance performers may have been due to a lesser production of metabolites in their running musculature when compared to nonendurance performers.

Adult↗

PubMed1979

Effects of calcium, lanthanum, and bicarbonate ion on epinephrine modification of insulin release in vitro.

The role of calcium flux in mediating epinephrine modification of insulin release was investigated by using lanthanum, an inhibitor of calcium flux, in the in vitro perifusion system. Lanthanum inhibits insulin secretion stimulated by glucose and by acetylcholine to basal levels. Epinephrine and lanthanum have additive effects in inhibiting insulin secretion to glucose stimulation. The effect of epinephrine prestimulation on insulin secretion to subsequent glucose challenge varies markedly, depending on the presence or absence of bicarbonate ion: epinephrine priming is reversed in the absence of bicarbonate, and effect possibly related to reduced calcium uptake. In the presence of bicarbonate, lanthanum blocks the priming effect of epinephrine on insulin secretion. The data further support the postulated role of calcium in adrenergic effects on beta cell function.

Animals↗

PubMed1976

Interactions of acetylcholine and epinephrine on the dynamics of insulin release in vitro.

An in vitro system for perifusion of rat pancreatic islets has been utilized to define the effects of epinephrine on acetylcholine-induced insulin release over varying concentrations of the two agents. Perifusion of islets with epinephrine before challenge with acetycholine produced marked enhancement of both phases of cholinergically induced insulin release; enhancement of the first phase being more marked with increase in acetylcholine concentration and the converse being observed with the second phase. Perifusion of islets with epinephrine during stimulation with acetylcholine produced inhibition of insulin release, an effect dependent upon the concentration of epinephrine and of acetylcholine. There was an order of difference in the acetycholine concentration needed to overcome significant epinephrine-mediated inhibition of the first phase of insulin release (5 X 10(-4) mug/ml) and that needed to overcome inhibition of the second phase (5 X 10(-3) mug/ml). Comparison of the effects of various concentrations of epinephrine on glucose- and acetyl-choline-induced insulin release revealed that epinephrine was a less potent inhibitor of the first phase of acetylcholine-induced insulin release than of the first phase of glucose-induced insulin release. These data provide some insight into the potential interactions between cholinergic and adrenergic autonomic systems in modifying insulin release.

Acetylcholine↗

PubMed1974

Cholinergic modification of glucose-induced biphasic insulin release in vitro.

An in vitro system for perifusion of rat pancreatic islets has been utilized to define the effects of cholinergic agents on the dynamics of insulin release. In the absence of glucose the effects of either acetylcholine or acetyl-beta-methylcholine were minimal at concentrations up to 10(-5) mM. In the presence of low glucose concentration (2.4 mM), both of the muscarinic agents produced dose-dependent biphasic insulin release. Under these conditions significant insulin release was observed over both phases at concentrations of the muscarinic agents as low as 10(-8) mM. Further, the dose response curves relating muscarinic concentration to the total amount of insulin released in each of the two phases showed lack of parallelism between the curves. Nicotinic acid in concentrations up to 10(-5) mM had no effect on insulin release in the presence of 2.4 mM glucose. When the glucose concentration was increased to 16.4 mM, the effects of the muscarinic agents were significantly less than those observed in the presence of 2.4 mM glucose. This held true whether the effect was defined as absolute increment due to the muscarinic agent or as percentage of enhancement. Atropine inhibited insulin release induced by both acetylcholine and by 16.4 mM glucose. These data indicate that cholinergic stimulation can play a significant role in modifying insulin release patterns.

Acetylcholine↗

PubMed1974