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Biomedical subjects

P White

Publications and source records attributed to P White.

At least 19 recordsLinked to original sources
PubMed1992

Predicting psychiatric admission rates.

OBJECTIVE: To determine the numbers of actual and expected psychiatric admissions for the residents of the district health authorities of England and to develop a model to indicate which social, health status, and service provision factors best explain the variation of the actual from the expected psychiatric admissions; to use this model to predict psychiatric admission for district health authorities as an aid to resource allocation. DESIGN: The actual psychiatric admission for district health authority residents were extracted from data of the 1986 Mental Health Enquiry. Expected admissions were calculated using the age, sex, and marital status structure of each district health authority and the national psychiatric admission rates related to age, sex, and marital status. Standardised psychiatric admission ratios were calculated as the ratios of the numbers of actual to expected psychiatric admissions. A wide range of social, health status, and service provision data were used as the explanatory variables in regression analyses to determine which combination of factors best explained the variation between districts of standardised psychiatric admission ratios. SETTING: The 168,652 psychiatric admissions recorded for the 1986 Mental Health Enquiry, after exclusion of mental handicap and psychogeriatric admissions. RESULTS: The actual number of psychiatric admissions varied from 79% above to 54% below the expected number of admissions from age, sex, and marital status for the districts of England. The most powerful variables to explain this variation were the rate of notification of drug misusers, standardised mortality ratios, and levels of illegitimacy in each district. A complex model was developed which could be used to predict district psychiatric admissions as an aid to resource allocation. A simpler model was also developed (which was less powerful than the more complex model) based on the underprivileged area score. One advantage of this model was that it could be used at the level of electoral wards as well as district health authorities.

Adolescent↗
PubMed1992

The differentiation of Chlamydia species by antigen detection in sputum specimens from patients with community-acquired acute respiratory infections.

An amplified enzyme immunoassay (IDEIA III: Dako Diagnostics Ltd) for detecting genus-specific chlamydia antigen was evaluated prospectively on 286 respiratory specimens from 275 patients presenting with community-acquired pneumonia or persistent chest infection. Nineteen patients had evidence of recent chlamydial infection, having two or more positive sputum or serological markers. Sputa from two other patients were ELISA-positive in the absence of other positive criteria and were regarded as false-positive results. When compared with a direct immunofluorescence test for chlamydial elementary bodies (EBs) using a genus-specific monoclonal antibody, the ELISA gave a positive predictive value of 91% and a negative predictive value of 99%. Non-specific problems with a wide variety of other micro-organisms isolated from the sputa were not encountered. Attempts to differentiate between Chlamydia psittaci, Chlamydia pneumoniae and Chlamydia trachomatis using genus-specific lipopolysaccharide reactive--and species-specific major outer membrane protein--monoclonal antibodies were encouraging and results were substantiated, in most patients, by the species-specific serological assays of the whole-cell-inclusion immunofluorescence or micro-immunofluorescence assays. The study demonstrated that antigen detection techniques offer scope for routine laboratories to diagnose chlamydial respiratory infections rapidly and reliably and may enable differentiation to species level. Although immunofluorescence offers marginally greater sensitivity and specificity when compared with ELISA, the latter is less subjective and less demanding. Sixty-eight per cent of these infections would have remained undiagnosed despite the general availability of ELISA tests.

Adult↗
PubMed1992

Is the pediatric preoperative hematocrit determination necessary?

The usefulness of the preoperative hematocrit determination as a screening test before outpatient pediatric surgical procedures has been questioned. It has been suggested that a careful history and physical examination are of greater importance than routine laboratory tests in determining a child's fitness for surgery. We evaluated the utility of preoperative measurement of hematocrit as a screening test for surgical fitness in healthy children having a variety of elective outpatient surgical procedures.

Adolescent↗
PubMed1992

Improved power control during microwave heating in biological applications.

The heating performance of prototype variable power control units attached to two domestic microwave ovens, 500 W and 700 W, was investigated. The units employed the phase control method where rated voltage was obtained by switching AC supply at a particular angular position on the sinusoidal voltage. In order to create experimental conditions employed in a previous study, Sydney tap water (50 mL) was heated at a 10% power level in the 500 W oven. Water boiled at 10 min in both experiments. However, the precision and control of the heating was greatly improved with addition of the control unit. A disinfecting solution (50 mL) and a tissue fixative (10 mL) were included for experiments with the 700 W oven. A power level of only 1% was sufficient to maintain the temperature of the fixative at low temperatures (30-40 degrees C) where many biological reactions occur. The present results indicate that microwave heating power can be controlled by the variable power control method. This will make temperature control possible through the provision of an electronic feedback loop which links a thermocouple with the power control unit.

Heating↗
PubMed1992

Calcium channel blockers.

Calcium channel blockers are widely used in the treatment of ischemic heart disease, hypertension, and supraventricular tachycardia. The prototype agents, verapamil, nifedipine, and diltiazem, represent three classes of calcium channel blockers, each of which has different pharmacologic effects. Nifedipine and the other dihydropyridines primarily are vasodilators and have no clinical effects on cardiac conduction or contractility. Diltiazem and verapamil also are vasodilators, but they possess, to varying degrees, negative inotropic, chronotropic, and dromotropic effects. Side effects of these drugs are relatively rare and usually not serious, with the exception of potential conduction disturbances and heart failure in patients with underlying cardiac disease. To assess patients taking these medications and provide the necessary teaching, the nurse needs an understanding of the pharmacologic properties, clinical indications, and potential adverse effects of the various drugs.

Calcium Channel Blockers↗
PubMed1992

Beta-agonists and surfactant in eustachian tube function.

The presence of surface tension lowering substances (surfactants) is demonstrable in the Eustachian tube (ET) and the middle ear, both in animals and in humans. In the lungs, beta-adrenoceptor agonists stimulate the secretion of surfactant; and it has been suggested that beta-agonists have a similar effect both in the ET and the middle ear, because opening of the ET is facilitated by the non-selective beta-agonist, isoprenaline in the rat, and by the beta 2-agonist, terbutaline, in humans. Two studies are described: In one, children with otitis media with effusion took terbutaline or placebo twice a day for two weeks and no significant differences were found between the effects of the two treatments; in the other study, it was shown that surfactant markedly facilitated the opening of the Eustachian tube. Lung surfactant prepared from pigs and instilled as a single dose into the middle ear of healthy rats reduced the air pressure necessary to open the Eustachian tube by as much as 15-20% for as long as the experiments lasted (i.e., around one hour). Thus, possibilities of facilitating the opening of the Eustachian tube do in fact exist.

Adrenergic beta-Agonists↗
PubMed1991

Cigarette advertising policy and coverage of smoking and health in British women's magazines.

A survey of cigarette advertising and coverage of health aspects of smoking in 86 British magazines with a large female readership was done in 1989. The findings were compared with the results of a 1985 survey which had led to the introduction of new voluntary restrictions in 1986 on cigarette advertising in magazines. Although there was a decrease in the proportion of magazines accepting cigarette advertising (64% to 42%), the new restrictions failed to cover the most popular magazines, so that an estimated collective readership of 7 million women aged 15-24 years were still exposed to cigarette advertising. Revenue from cigarette advertising by women's magazines increased by 10% in real terms between 1985 and 1988. There was a small decrease in the coverage given to health aspects of smoking; a third of magazines were willing to use pictures of people smoking in their editorial pages. The findings show that the voluntary restrictions introduced in the UK in 1986 have had a small effect on cigarette advertising and have failed to achieve their aim of protecting young women.

Adolescent↗
PubMed1991

Surface tension of secretions from eustachian tube and middle ear.

The surface tension of secretions from the pharyngeal orifice of the eustachian tube in eight rabbits was analyzed with a modified maximum-bubble pressure method. Measurements were made before, during, and after intravenous injections of isoprenaline (10 micrograms/kg). Surface tension was found to be 57.6 +/- 0.9 (mean +/- SEM) mN/m before injections, and was not significantly changed by isoprenaline. The surface tension in middle-ear secretions from children with secretory otitis media was also determined, the serous type of secretion measuring 62.0 +/- 1.4 mN/m (n = 8), and the mucoid type 70.7 +/- 2.6 mN/m (n = 9). In another ten humans, measurements of tears were performed, and the surface tension was found to be 59.9 +/- 2.2 mN/m. This bubble technique promises to be useful for the evaluation of surface tension when the available sample volume is very small.

Adult↗
PubMed1990

Influence of acoustic deprivation on recovery of hair cells after acoustic trauma.

The purpose of this study was to investigate how the recovery of the cochlea, after acoustic trauma, might be influenced by acoustic stimulation or deprivation. In anaesthetized adult chinchillas, both ears were simultaneously exposed to a traumatizing acoustic stimulus (2 kHz tone, at 117 dB SPL for 15 min). Probe microphones positioned in both bullae were used to ensure identical exposure to the two ears; this was important because the experiment relies on within-animal controls. Cochlear action potential thresholds across frequency (CAP audiograms) were used to verify the similarity of threshold shifts to the two ears. Immediately following, a unilateral ossiculectomy was performed which resulted in one cochlea being acoustically deprived during the recovery period, whilst the other was not. In groups of animals with recovery periods of 1, 3, 6, and 12 weeks, both the acoustically deprived and the normally stimulated cochleas were examined with scanning electron microscopy. To quantify hair cell damage, we used a damage scale based on stereociliar integrity; for each cochlea, a standard region 5.5-8.5 mm from the apex was studied in detail. We found that after acoustic trauma, hair cell damage to the cochlea which is deprived of sound during the recovery period, is significantly greater compared with that in the normally stimulated, contra-lateral cochlea. Our results suggest that mechanical activation of the inner ear acts to inhibit long-term degenerative processes, or influence repair of partially damaged hair cells.

Action Potentials↗
PubMed1990

Uncertainties in pharmacokinetic modeling for perchloroethylene. I. Comparison of model structure, parameters, and predictions for low-dose metabolism rates for models derived by different authors.

In recent years physiologically based pharmacokinetic models have come to play an increasingly important role in risk assessment for carcinogens. The hope is that they can help open the black box between external exposure and carcinogenic effects to experimental observations, and improve both high-dose to low-dose and interspecies projections of risk. However, to date, there have been only relatively preliminary efforts to assess the uncertainties in current modeling results. In this paper we compare the physiologically based pharmacokinetic models (and model predictions of risk-related overall metabolism) that have been produced by seven different sets of authors for perchloroethylene (tetrachloroethylene). The most striking conclusion from the data is that most of the differences in risk-related model predictions are attributable to the choice of the data sets used for calibrating the metabolic parameters. Second, it is clear that the bottom-line differences among the model predictions are appreciable. Overall, the ratios of low-dose human to bioassay rodent metabolism spanned a 30-fold range for the six available human/rat comparisons, and the seven predicted ratios of low-dose human to bioassay mouse metabolism spanned a 13-fold range. (The greater range for the rat/human comparison is attributable to a structural assumption by one author group of competing linear and saturable pathways, and their conclusion that the dangerous saturable pathway constitutes a minor fraction of metabolism in rats.) It is clear that there are a number of opportunities for modelers to make different choices of model structure, interpretive assumptions, and calibrating data in the process of constructing pharmacokinetic models for use in estimating "delivered" or "biologically effective" dose for carcinogenesis risk assessments. We believe that in presenting the results of such modeling studies, it is important for researchers to explore the results of alternative, reasonably likely approaches for interpreting the available data--and either show that any conclusions they make are relatively insensitive to particular interpretive choices, or to acknowledge the differences in conclusions that would result from plausible alternative views of the world.

Animals↗
PubMed1990

Characterization of 11 beta-hydroxysteroid dehydrogenase gene expression: identification of multiple unique forms of messenger ribonucleic acid in the rat kidney.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11-HSD) appears to be involved in mediating aldosterone specificity of otherwise nonselective type I receptors in mineralocorticoid target tissues. In the present study gene expression of 11-HSD was characterized in various tissues of the rat by use of a complementary DNA probe coding for the rat liver 11-HSD. In the liver, lung, testis, colon, heart, hippocampus, and kidney papilla a single message was observed of length approximately 1700 nucleotides (nt). In the kidney cortex/medulla, however, messenger RNA (mRNA) species were observed at 1900 nt, 1600 nt and 1500 nt, and deadenylation studies showed that the renal 1900 nt species was heterogeneous. Northern blot analysis of 11-HSD mRNA showed low levels of expression in the kidney of the neonate and much higher levels in liver and lung with expression increasing markedly in all three tissues over development. In mature rats, a low salt diet significantly elevated 11-HSD mRNA in the liver but not in other tissues. We interpret these data as evidence for the existence of a family of 11-HSD genes, and consistent with the possibility that the hepatic species may modulate occupancy of type II (classical) glucocorticoid rather than type I receptors.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

Morbidity associated with childhood systemic lupus erythematosus.

A complete analysis of the outcome of childhood onset systemic lupus erythematosus (SLE) requires determination of survival statistics and consideration of disease and treatment morbidity. The course of 32 patients with SLE diagnosed at or prior to age 16 and followed from 1979-1988 was analyzed with emphasis on the morbidity of pediatric SLE. Clinical characteristics were similar to those in previous studies. Five year survival, calculated by life-table analysis, was 85.3%, comparable to recent studies. Treatment consisted of corticosteroids (32 patients), antimalarials (14), cyclophosphamide (9) or azathioprine (2). Eighty-four percent of patients experienced a noninfectious drug related complication. A major infection contributed in all 5 patients who died. Higher total corticosteroid dose was associated with more severe infections. Eighty-eight percent of patients were left with chronic organ dysfunction. Survival in childhood onset SLE has improved, but morbidity remains a significant problem from organ dysfunction and complications of therapy. Our study is the first to address the issue of morbidity in childhood SLE.

Adolescent↗
PubMed1990

Allele loss from chromosome 17 in ovarian cancer.

In a number of human cancers genes capable of suppressing tumorigenicity have been identified and in some instances cloned. Successful isolation of such tumour suppressor genes has depended upon either the mapping of a locus which confers susceptibility to a specific tumour, or the finding of specific allele loss in the tumour cells of heterozygous individuals. In ovarian cancer it is known that a small proportion (approximately 5%) of tumours are due to inheritance (Lynch et al., 1989). However, as yet the locus responsible has not been mapped. The only incidence of allele loss in ovarian tumours reported is on the short arm of chromosome 11 using a c-Ha-ras I probe to detect an RFLP (Lee et al., 1989), and on 3p and 6 in a small number of cases (Ehlen & Dubeau (1990)). We describe here the results of analysis of 19 tumours for allele loss using a probe for a hypervariable locus on the long arm of chromosome 17. Approximately 77% (10/13) of tumours from informative patients showed complete or partial allele loss at this locus. Using a probe for the short arm of chromosome 17, 31% (4 of 13 informative patients) demonstrated allele loss at this position. These results suggest that possible involvement of more than one chromosomal locus in the development of ovarian cancer.

Alleles↗
PubMed1989

Ethnic differences in consultation rates in urban general practice.

OBJECTIVE: To determine the patterns of consultations with the general practitioner among different ethnic groups and the outcome of these consultations. DESIGN: Retrospective analysis of data from one urban group general practice collected during 1979-81 as part of a research project in seven practices. SETTING: Group general practice in the London borough of Brent with a list size of 10,877 patients in July 1980. SUBJECTS: Patients registered with the practice during the 23 months to April 1981 who accounted for 67,197 consultations. MAIN OUTCOME MEASURES: Ethnic state, sex and social class distribution, and diagnosis of patients consulting and frequency of consultations analysed as standardised consultation ratios and standardised patient consultation ratios. RESULTS: Compared with other ethnic groups male Asians (that is, including those born in Britain and those originating from the Indian subcontinent and east Africa) had a substantially increased standardised patient consultation ratio. Consultation rates for mental disorders--in particular, anxiety and depression--were reduced in all groups of immigrant descent. West Indians consulted more frequently for hypertension and asthma, and their children less frequently with otitis media. Asians consulted more frequently with upper respiratory tract infections and non-specific symptoms. Native British patients were more likely to leave the surgery with a follow up appointment, prescription, or certificate. CONCLUSION: Notwithstanding the limitations of this study, ethnic differences in consultation rates were apparent. These differences require further investigation if the needs of minority ethnic groups are not to be overlooked.

Asia↗