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Biomedical subjects

J Dixon

Publications and source records attributed to J Dixon.

At least 145 records · Page 8Linked to original sources
PubMed1989

Computer controlled infusion of propofol.

A computer controlled infusion pump was used to deliver propofol to two groups of eight patients undergoing body surface surgery. The patients were premedicated with morphine sulphate i.m. and anaesthesia was supplemented with 66% nitrous oxide in oxygen. Patients in group 1 breathed spontaneously, whereas patients in group 2 underwent artificial ventilation to a normal PaCO2. The computer program was designed to achieve and maintain a blood concentration of propofol 3 micrograms ml-1 as rapidly as possible, basing calculations on a three-compartment pharmacokinetic model. Mean blood propofol concentrations were found to be close to the predicted target from 10 to 120 min in group 1, but were 5-20% higher from 20 min in group 2.

Adult↗
PubMed1989

Liver insulin receptor tyrosine kinase activity in a rat model of type II diabetes mellitus and obesity.

Spontaneous hypertensive-corpulent rats (SHR/N-corpulent), homozygous for the corpulent gene (cp/cp), are obese, hyperinsulinemic and exhibit abnormal glucose tolerance and thus represent a model for type II diabetes and obesity. In view of their overall insulin resistance, we examined liver insulin receptor binding and tyrosine kinase activity from corpulent rats and lean littermates fed purified diets containing 54% sucrose or starch for about 12 wk. Specific 125I-insulin binding to crude liver membranes from female corpulent rats fed either starch or sucrose was reduced to approximately 50% of that seen in lean rats (14 vs. 7%). Affinity of insulin receptors was similar in all groups, suggesting that hyperinsulinemic corpulent rats possess fewer hepatic insulin receptors than do lean rats. Using similar numbers of wheat germ agglutinin-agarose (WGA)-purified insulin receptors with similar affinities for insulin, it was found that basal and insulin-stimulated phosphorylation of the synthetic tyrosine-specific kinase substrate poly(Glu, Tyr)4:1 was similar in lean and obese rats fed sucrose or starch. It is suggested that the contribution of the liver to the insulin resistance in obese SHR/N-cp rats probably lies distal to the insulin receptor tyrosine kinase.

Animals↗
PubMed1989

The limits and potential of community development for personal and social change.

Some health and welfare workers are making claims for community development which are both unrealistic and misleading. By tracing the history and public policy use of community development and by defining its characteristics, much of the mystique which surrounds this intervention is eliminated. Community development is revealed in this paper to have potential in the areas of personal and planned social change. However, community development's contribution to fundamental social change is circumscribed by the nature of government sponsorship and by its very process which emphasizes parochialism and the generation of self reliance.

Australia↗
PubMed1988

Type 1 (insulin-dependent) diabetes in Tasmania: prevalence and apparent regional differences.

The results of a cross-sectional study of Type 1 (insulin-dependent) diabetes in the total population of Tasmania are described. Tasmanians, predominantly of British origin, live in a temperate island situated to the south-east of mainland Australia. For males and females respectively, prevalence in 1984 was 1.1 +/- 0.1 and 0.9 +/- 0.1 per 1,000 at all ages, 0.6 +/- 0.2 and 0.5 +/- 0.2 per 1,000 in subjects aged 0-14 years, rising to 1.2 +/- 0.2 and 1.1 +/- 0.2 per 1,000 in those aged 0-29 years. Prevalence in the 0-19 year age range was 0.8 +/- 0.2 per 1,000 in both sexes. Prevalence fell in both sexes from the third decade of life. A statistically significant excess in prevalence was found in the urban, as compared with the rural, sector of the community. The urban relative risk was greatest in subjects aged 10-19 years. According to reported month of onset (commencement of insulin treatment) there was a suggestion of seasonal trend in the rural, but not in the urban subjects. Longitudinal studies of Type 1 diabetes in Tasmania are now required if these findings are to be confirmed, and their possible aetiological implications explored.

Adolescent↗
PubMed1988

Clonidine premedication for isoflurane-induced hypotension. Sympathoadrenal responses and a computer-controlled assessment of the vapour requirement.

The effect of single-dose clonidine premedication on the vapour requirement for isoflurane-induced hypotension in patients undergoing middle ear or nasal surgery was evaluated in an open, controlled, randomized study. Inspired isoflurane concentration was regulated by a microcomputer-based, self-tuning control program when hypotension was required. Patients given clonidine 0.6 mg by mouth 2 h before operation required a mean inspired isoflurane concentration of 2.0% to induce hypotension (mean intra-arterial pressure 50 mm Hg) compared with 3.01% in the control group (P less than 0.05). Five out of 10 patients in the control group required a supplementary dose of labetalol 5 mg i.v. to achieve satisfactory hypotension, compared with one of 10 patients given clonidine premedication (Fisher's exact probability, 0.07). A mean concentration of 1.4% isoflurane was required to maintain hypotension in the clonidine group, compared with 2.3% in the control group (P less than 0.01). Plasma adrenaline and noradrenaline concentrations did not increase during induced hypotension in each group.

Adolescent↗
PubMed1988

Induction and maintenance of propofol anaesthesia. A manual infusion scheme.

A simple, manually controlled infusion scheme for continuous administration of propofol was derived by simulation of a computer algorithm designed to achieve a predetermined blood concentration of propofol within 2 minutes and to maintain a constant blood level for the duration of surgery. The manual infusion scheme for a target blood propofol concentration of 3 micrograms/ml, consisted of a loading dose of 1 mg/kg followed immediately by an infusion of 10 mg/kg/hour for 10 minutes, 8 mg/kg/hour for the next 10 minutes and 6 mg/kg/hour thereafter. An overall mean blood propofol concentration of 3.67 micrograms/ml was achieved within 2 minutes and maintained stable for the subsequent 80-90 minutes of surgery. The decrease of systolic and diastolic arterial pressures at induction was much less than that previously described after larger induction doses of propofol and there was a negligible haemodynamic response to laryngoscopy and intubation or to the subsequent surgery. The quality of induction and maintenance of anaesthesia was satisfactory in every patient.

Adult↗
PubMed1987

Localization of neuropeptide Y mRNA in neurons of human cerebral cortex by means of in situ hybridization with a complementary RNA probe.

The distribution of mRNA encoding neuropeptide Y (NPY) in neurons of the normal human cerebral cortex in surgical biopsy specimens and postmortem brain was studied by in situ hybridization techniques. A 32P-labeled complementary RNA (cRNA) probe was used on cryostat sections of 13 formaldehyde-fixed cortical biopsy specimens. Hybridization to NPY mRNA was found in all samples: after autoradiography, discrete deposits of silver granules were observed on neuronal cell bodies abundantly distributed in the deep layers of the cortex, particularly laminae IV and VI, and on smaller cell bodies in the white matter. The localization of the neurons hybridized for NPY mRNA was comparable to that of NPY-immunoreactive cells as shown in sections from the same tissue blocks immunostained by using NPY antibodies. The specificity of the in situ hybridization technique was confirmed by blot hybridization analysis of electrophoretically fractionated RNA. This study clearly demonstrated the consistent localization of NPY gene transcription and expression in normal mature human cortical neurons.

Antibodies↗
PubMed1987

Multiple treatment interference in the alternating treatments design as a function of the intercomponent interval length.

In experimental designs requiring the administration of more than one treatment to the same subject(s), the effect of one treatment may be influenced by the effect of another treatment (Campbell & Stanley, 1963), a phenomenon known as multiple treatment interference. We conducted two studies in which multiple treatment interference in an alternating treatments design was shown to be a function of the length of the intercomponent interval (ICI) separating treatment conditions. In the first study, we evaluated the effects of four different treatments on the mouthing of a severely retarded boy. Under a 1-min ICI no consistent differential responding to treatment was obtained. Differential responding emerged when the ICI was increased from 1 min to 120 min, thus suggesting multiple treatment interference in the lack of differential responding under a 1-min changeover interval. Functional control of the nondifferential and differential responding as a function of the ICI length was replicated in a reversal phase. In the second study, we compared two treatment procedures for the disruptive noncompliant behavior of a moderately retarded boy. Multiple treatment interference (i.e., the lack of differential responding) occurred with the 1-min intercomponent interval. An increase to a 120-min ICI again resulted in differential responding. A replication of multiple treatment interference by a reversal to a short interval phase was not achieved in the second subject. Results of this study support much of the basic literature on discrimination and multiple treatment interference.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavior Therapy↗
PubMed1986

Hepatitis B surface antigen polypeptide micelles from antigen expressed in Saccharomyces cerevisiae.

Hepatitis B micelles containing the p25 component of hepatitis B surface antigen (HBsAg) have been produced by Triton X-100 solubilization followed by ultracentrifugation in linear sucrose gradients. The product was found to resemble micelle forms prepared from plasma-derived HBsAg with the surface being composed of discrete globular and stranded sub-units. The degree of immunochemical relatedness of the micellular preparation was compared to the native 22-nm HBsAg particle present in either plasma or yeast cell extracts. The yeast micelle preparation competed for anti-HBs in a similar manner as intact HBsAg of plasma origin. Enhanced immunogenicity may be expected for micelles containing a recombinant HBsAg protein as has previously been shown for the plasma-derived antigen.

Centrifugation, Density Gradient↗