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J Stewart

Publications and source records attributed to J Stewart.

At least 451 records · Page 25Linked to original sources

Cars.

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Automobiles↗

Does a water soluble contrast enema assist in the management of acute large bowel obstruction: a prospective study of 117 cases.

We have performed a prospective study on 117 patients in order to assess the value of a single contrast water soluble enema in acute large bowel obstruction. In 99 cases where the plain films suggested a diagnosis of mechanical obstruction, the Diodone enema confirmed its presence in 52, and relocated its site in 11. There was free flow of contrast to the caecum in the remaining 35, 11 of whom were shown to have idiopathic pseudo-obstruction. The plain films suggested a diagnosis of pseudo-obstruction in 18 patients. The Diodone enema confirmed this diagnosis in 15, but revealed an unsuspected mechanical obstruction in two. The examination failed in two cases. We conclude that the water soluble single contrast enema is of value in the management of large bowel obstruction. It will confirm the diagnosis of mechanical obstruction and prevent unnecessary surgery in patients with pseudo-obstruction.

Acute Disease↗

Dietary obesity and exercise in young rats.

Food intake, body weight, body composition, resting metabolic rate (RMR) and the thermic effect of food (TEF) were measured in young rats, some of which were fed a high energy (HE) diet and some of which were forced to swim daily. In general, high energy feeding as compared to chow feeding, resulted in higher food intake, higher body weight, higher body fat, and a slightly lower TEF. In many cases, however, the specific effects varied with the age and sex of the animals. Animals forced to swim weighed less; were leaner; and had higher RMR and TEF than sedentary animals. The effects of exercise on energy balance were greatest in males, while the effects of the high energy diet on energy balance were greatest in females. All HE-fed rats were switched to lab chow at 104 days of age. Body weights of sedentary HE-fed rats returned to control levels but those of exercised HE-fed rats did not. Both HE-fed groups remained fatter than chow-fed controls, even two months after the diet switch.

Adipose Tissue↗

Reinstatement of heroin and cocaine self-administration behavior in the rat by intracerebral application of morphine in the ventral tegmental area.

In rats trained to self-administer heroin or cocaine intravenously, non-contingent priming injections of heroin or cocaine, respectively, reinstated responding after a period of extinction. In rats similarly trained to self-administer heroin or cocaine intravenously, morphine sulphate was applied centrally to sites in the ventral tegmental area (VTA), the periventricular grey (PVG) and the caudate nucleus following a period of extinction. Self-administration behavior was reinstated by morphine application to sites in the region of the VTA, but not to other sites, in both heroin and cocaine-trained animals. This priming effect of morphine was blocked or attenuated by prior administration of naltrexone, given intraperitoneally. Morphine in the VTA is known to activate mesolimbic dopamine neurons, suggesting that dopamine activity in this system may underlie the priming effects of both opiates and stimulants. Furthermore, the fact that the mesolimbic system is implicated in the positive motivational actions of both drug groups, suggests that morphine reinstates drug-taking behavior in these animals by activating appetitive motivational systems of the brain.

Animals↗

Conditioning and place-specific sensitization of increases in activity induced by morphine in the VTA.

The conditionability of increases in locomotor activity induced by morphine administration into the ventral tegmental area was studied in rats. Morphine produced a clear increase in locomotor activity that was reversed by the opiate receptor blocker, naloxone, and blocked by the neuroleptic, pimozide, suggesting the mediation of this effect by the ascending mesolimbic dopamine system. The increase in locomotor activity showed sensitization with repeated morphine administrations and this sensitization was found to be specific to the environment in which morphine was administered. Conditioning tests also revealed that, in the absence of morphine, increased locomotor activity was elicited by the administration environment. Pimozide blocked the development of the conditioned sensitization. These data demonstrate that a learned association developed between this excitatory action of morphine and the administration environment. These results have important implications for the role of conditioning factors in relapse to drug use and may provide an explanation for conditioning data obtained when morphine is administered systemically.

Animals↗

Development of an in situ microbial mutagenicity test system for airborne workplace mutagens: laboratory evaluation.

A simple on-site Salmonella mutagenicity test system for the detection of airborne mutagens in the workplace is being developed. The system permits entrapment of mutagenic airborne particles and vapors by impinging unfiltered ambient air into trapping medium containing bacterial tester cells. The trapping device consists mainly of a pump, an impinger and a cyclone. The impinging air flow generated by the pump is approximately 3 1/min. New Salmonella typhimurium testers which are resistant to streptomycin (Str) and 8-azaguanine (AG) were derived from the Ames testers TA98 and TA100 and the arabinose-resistant tester SV50, and were used as mutation indicators. Microbial contamination was sufficiently controlled by addition of ampicillin, Str, AG, and cycloheximide to the trapping and plating media. New tester strains retained a high mutagenic sensitivity from their parent strains. Laboratory studies with volatile mutagens (methyl methanesulfonate, ethyl methanesulfonate, and dimethylnitrosamine) showed that the vapor trapping of this system is promising. The study with suspended silica particles coated with a known mutagen (2,4,7-trinitro-9-fluorenone) indicated that the particle trapping of the system is satisfactory. Incorporation of metabolic activation into the trapping medium by confining S9 mix and tester cells in dialysis tubing enabled this system to detect promutagens. This in situ system may be useful for mutagenic monitoring in the workplace.

Air Pollutants, Occupational↗

Detection of sister-chromatid exchanges in human peripheral lymphocytes induced by ethylene dibromide vapor.

A method using sister-chromatid exchanges (SCEs) for genotoxic testing of gaseous compounds is described. Human peripheral lymphocyte cultures previously stimulated with phytohemagglutinin were placed in sterile dialysis tubing and then put in an enclosed flask containing additional culture media. Air, with or without ethylene dibromide (EDB), was bubbled through the flask for up to 8 h. The cultures were harvested 75 h after culture initiation, and second-division cells were scored for induction of SCEs according to established procedures. The SCE frequency was approximately doubled in cultures treated with EDB. A similar experiment with air alone resulted in only slight increases in SCEs. The results indicate that this system is potentially useful for detecting genotoxicity of gases and vapors and may be useful for the detection of genotoxic agents in occupational settings.

Cells, Cultured↗

Reverse doming of the anterior mitral leaflet with severe aortic regurgitation.

The normal anatomic relation of the anterior mitral leaflet to the left ventricular outflow tract suggests that significant aortic regurgitation should have a predictable hemodynamic effect on the motion and configuration of the leaflet, an effect that should be seen by two-dimensional echocardiography. Previous reports have identified an abnormality of mitral opening in the short-axis view that was quite specific but not sensitive. This study was undertaken to evaluate mitral valve motion and configuration in aortic insufficiency using two-dimensional echocardiography. A characteristic pattern of anterior leaflet motion was found in patients with moderately severe and severe aortic regurgitation. This pattern, termed "reverse doming," was seen in the apical and long-axis views in 19 of 22 such patients. The previously described "diastolic indentation" in the short-axis view was found in 16 of these 22 patients. Only 2 of 16 patients with lesser degrees of insufficiency had reverse doming. The sign was not seen in normal subjects nor in 16 patients with cardiomyopathy. For each of the few false positive and false negative findings, there is a seemingly logical hemodynamic explanation. It is concluded that reverse doming of the anterior mitral leaflet appears to be a sensitive and specific sign for moderately severe and severe aortic regurgitation.

Aortic Valve Insufficiency↗

The penetration of latamoxef disodium (moxalactam) into the subcutaneous fat and skeletal muscle of ischaemic lower limbs with atherosclerotic disease.

After pre-operative administration of 1 g, latamoxef disodium (moxalactam) levels were measured in peripheral venous blood, skeletal muscle and subcutaneous fat sampled from 29 patients during either arterial reconstruction or amputation undertaken for arterial occlusive disease. Tissue samples were taken from both proximal and distal levels in the amputated limbs. Levels of latamoxef disodium were above the minimum inhibitory concentration required for most commonly encountered Gram-positive and Gram-negative organisms. No patients developed toxicity or superficial wound infection but there was one vascular graft infection by Candida albicans. It has been shown that latamoxef disodium penetrates rapidly into the subcutaneous fat and skeletal muscle of relatively ischaemic limbs, achieving levels inhibitory to many common pathogens.

Adipose Tissue↗

Effect of number of receptors for gonadotropin-releasing hormone on the release of luteinizing hormone.

The relationship between number of receptors for gonadotropin-releasing hormone (GnRH) and the ability of the anterior pituitary gland to release luteinizing hormone (LH) was examined in ovariectomized ewes. A GnRH antagonist was used to regulate the number of available receptors. The dose of GnRH antagonist required to saturate approximately 50 and 90% of GnRH receptors in ovariectomized ewes was determined. Thirty min after intracarotid infusion of GnRH antagonist, ewes were killed and the number of unsaturated (i.e., those available for binding) pituitary GnRH receptors was quantified. Infusion of 10 and 150 micrograms GnRH antagonist over a 5-min period reduced binding of the labeled ligand to approximately 50 and 12% of controls, respectively. The effect of reducing the number of GnRH receptors on release of LH after varying doses of the GnRH agonist, D-Ala6-GnRH-Pro9-ethylamide (D-Ala6-GnRH) was then evaluated. One of four doses of D-Ala6-GnRH (0.125, 2.5, 50 and 400 micrograms) was given i.v. to 48 ovariectomized ewes whose GnRH receptors had not been changed or were reduced to approximately 50 or 12% of control ewes. In ewes with a 50% reduction in GnRH receptors, total release of LH (area under response curve) was lower than that obtained for controls (P less than 0.01) at the 0.125-micrograms dose of D-Ala (6.1 +/- 0.7 cm2 vs. 13.5 +/- 0.7 cm2) but was not different at the 2.5-, 50- or 400-micrograms doses of D-Ala6-GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗