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Biomedical subjects

A Potter

Publications and source records attributed to A Potter.

13 recordsLinked to original sources
PubMed1992

Acute nicotinic blockade produces cognitive impairment in normal humans.

Single oral doses of the central and peripheral nicotinic antagonist mecamylamine were administered to healthy young normal males in doses of 5, 10, and 20 mg in a placebo-controlled, double-blind study. The 20 mg dose caused a significant increase in errors in the learning condition of the Repeated Acquisition task, producing a slower acquisition curve. The lower doses produced less errors, but more than in the placebo condition. There was no effect of drug on the performance component (retrieval of previously learned information). On the recognition memory task, dose-related increases in false-alarms during the delay period were seen, with little effect on misses or hits. Reaction time measures suggested a dose-related slowing of RT on several tasks. Behavioral effects were minimal and physiologic measures were consistent with dose-related ganglionic blockade. We interpret these results to indicate that acute blockade of nicotinic receptor function can produce measurable and significant cognitive impairment, even in non-smoking normals.

Adult↗
PubMed1992

Oncogene expression in primary myelodysplasia: correlation with haematological, karyotypic, and clinical progression.

AIMS: To see if the relative expressions of proto-oncogenes that are increased in acute myeloid leukaemia are raised in patients with myelodysplastic syndromes (MDS), and to see if they increase with progression to leukaemia. To note if there is a correlation between morphology, karyotype, and these proto-oncogene expressions and if any one proto-oncogene can predict prognosis. METHOD: Bone marrow from 130 patients was analysed at six monthly intervals over two years for relative mRNA expression of seven oncogenes, karyotype, and morphology. The technique used slot blot hybridisation and densitometric analysis. The results were compared with 14 surgical controls and 30 people with vitamin deficiency anaemia. RESULTS: Six of seven oncogenes showed increased expression which progressed with time, but did not correlate with morphological or karyotypic changes. Expression of four of the seven oncogenes was increased in megaloblastic and iron deficiency anaemia. C-mos showed differences among the five morphological subgroups; it correlated with abnormal location (p = 0.025) and seemed to influence prognosis. CONCLUSION: Increased proto-oncogenes reflect the overall marrow perturbation in MDS. C-mos may reflect persistence of monocyte pathway which confirms marrow stability.

Aged↗
PubMed1991

Secondary in vitro B lymphocyte (antibody) response to microbial antigens: use in appraisal of vaccine immunogenicity and cytokine immunoregulation.

In order to perform preliminary evaluations of subunit vaccine candidates before extensive trials in large food-producing animals, an in vitro B-lymphocyte response assay, based on the principles of an ELISA, was established. The assay was developed in detail for the porcine system using antigens from the Gram-negative bacterium Actinobacillus pleuropneumoniae, but is shown to be applicable to other species and antigens, including viral components. It is further shown that B-cell activity in the assay is dependent on T-helper cells as well as macrophages and/or their secretory products. Thus, in addition to providing a tool for evaluation of T and B memory cell activity, the system also lends itself to dissection of T-B cell collaboration and the regulatory functions of interleukins in secondary (in vitro) antibody responses.

Actinobacillus↗
PubMed1991

Response of cerebral blood volume to changes in arterial carbon dioxide tension in preterm and term infants.

The response of cerebral blood volume (CBVR) to a small induced change in arterial carbon dioxide tension was studied by near-infrared spectroscopy in 17 newborn infants born from 26 wk of gestation to term. All 17 infants were undergoing mechanical ventilation but had apparently normal brains. The CBVR per kPa change in arterial carbon dioxide tension within the range 3.9 to 9.6 kPa was calculated from the change in total cerebral Hb concentration ([TCHb]) using the equation: delta CBV = delta [TCHb] x 0.89/[H] where [H] is the large vessel Hb concentration. A least-squares regression line with 95% confidence limits was derived for CBVR against gestational age. A highly significant linear increase in CBVR was found: mean CBVR from the regression increased from 0.07 mL.100 g-1.kPa-1 at 26 wk to 0.51 mL.100 g-1.kPa-1 at 40 wk.

Arteries↗
PubMed1990

Effects of indomethacin on cerebral haemodynamics in very preterm infants.

Near infrared spectroscopy was used to investigate the effects of intravenously administered indomethacin (0.1-0.2 mg/kg) on cerebral haemodynamics and oxygen delivery in 13 very preterm infants treated for patent ductus arteriosus. 7 infants received indomethacin by rapid injection (30 s) and 6 by slow infusion (20-30 min). In all the infants cerebral blood flow, oxygen delivery, blood volume, and the reactivity of blood volume to changes in arterial carbon dioxide tension fell sharply after indomethacin. There were no differences in the effects of rapid and slow infusion. These falls in cerebral oxygen delivery and the disruption of cerebrovascular control might compromise cellular oxygen availability, particularly in regions of the brain where the arterial supply is precarious. Care should be taken to ensure that oxygen delivery is optimum before the administration of indomethacin to preterm infants.

Blood Gas Monitoring, Transcutaneous↗
PubMed1990

Time and temperature dependence of granulocyte damage by leucotoxic supernatants from Pasteurella haemolytica A1.

Bacterial exotoxins may contribute to the pathogenic potential of micro-organisms through interactions with cells of the host defence system as well as by directly damaging host tissue. The present studies were designed to explore mechanisms of interaction between bovine granulocytes and the leucotoxin produced by Pasteurella haemolytica, a major cause of bovine respiratory disease. Leucotoxin-containing supernatant from P. haemolytica A1 caused rapid cell death in isolated bovine granulocytes that was close to half-maximal by 5 min and nearly 90% complete after 30 min at 37 degrees C. Maintaining granulocytes at ice-water temperature markedly attenuated or prevented the toxic effect; furthermore, if exposed to supernatants at ice-water temperature and then washed, most cells remained viable even after rewarming to room temperature. However, even a very brief exposure (about 5 s) at 37 degrees C led to extensive cell death even after immediate cold dilution and washing. Granule enzymes such as arylsulphatase were released far more slowly than cytosol contents. Leucotoxin purified by column chromatography showed temperature dependence and divergence between cytosol and granule marker release similar to those observed with the crude supernatant preparation. These findings indicate that irreversible interaction between P. haemolytica leucotoxin and bovine granulocytes is initiated very rapidly at 37 degrees C but markedly impeded at low temperature, while granule enzyme release follows cytosol marker release over a much longer period. The results suggest either a requirement for target cell metabolic activity to initiate toxin effects or a temperature-dependent receptor conformation, with granule enzyme release following as a secondary consequence of granulocyte death.

Animals↗
PubMed1978

Improved myocardial performance in postoperative cardiac surgical patients with sodium nitroprusside.

Myocardial performance in the immediate postoperative period was studied 49 cardiac surgical patients treated with nitroprusside alone. With a thermodilution catheter positioned in the pulmonary artery, cardiac output was calculated and cardiac index, systemic vascular resistance index, and stroke work index were derived before after treatment with nitroprusside. The drug was a administered to all patients because of elevated systemic vascular resistance index. Based on their mean arterial pressure and cardiac index before treatment, the patients fell into two groups. Group I patients (N = 25) had elevated mean arterial pressure and normal cardiac index. Group II patients (N = 24) had normal mean arterial pressure and subnormal cardiac index. Nitroprusside administration resulted in a significant reduction of systemic vascular resistance index in all patients. In Group I the mean arterial pressure was lowered significantly while cardiac index increased only slightly. In Group II there was no change in arterial pressure, but cardiac index improved significantly. The results not only confirm that nitroprusside is effective in managing postoperative hypertension, but also demonstrate that in patients with postoperative left ventricular failure, the drug can improve cardiac output by reducing systemic vascular resistance without significantly lowering arterial blood pressure.

Adult↗
PubMed1976

Predicting resource utilization in a comprehensive center: an evaluation of three alternative methods.

Three alternative methods for obtaining anticipated resource utilization information for comprehensive mental health centers are proposed. The methods differ on two dimensions, sample selection and statistical technique. Using an admission cohort rather than a discharge cohort and eliminating patients who terminated treatment against medical advice permitted a refined prediction. Although no significant differences were found between the chi-square and multiple-regression techniques, the latter resulted in a substantially greater degree of flexibility.

Humans↗
PubMed1975

Readmission discount factors in program evaluation. An output value analysis of an adult psychiatry program.

The application of output value analysis, a type of benefit/cost analysis, to a psychiatric patient population is reported. A method for discounting the value of the program if a patient was readmitted within a year after discharge was introduced. The application of this discount factor reduces the value produced by the program and thereby reduces both productivity and effectiveness indices. When applied to groups known to differ in readmission rates, such as first admissions and readmissions or voluntary and involuntary admissions, the discount factor can accentuate group differences markedly. When selected diagnostic groups were compared, the discount factor could even reverse the relative standing of the groups.

Brain Damage, Chronic↗