Search PubMed⌕ Search

Biomedical subjects

B Williams

Publications and source records attributed to B Williams.

At least 361 records · Page 20Linked to original sources
PubMed1991

Indicators of sexual maturation and regression in the female cat flea, Ctenocephalides felis.

Differences in the salivary glands, mesenteron epithelium and reproductive organs of female cat fleas, Ctenocephalides felis Bouché (Siphonaptera: Pulicidae), are related to the degree of reproductive maturation or regression. Contrary to previous ideas, blue bodies in the ovarioles are degenerate oocyte nuclei and their presence denotes failure of ripening oocytes to reach full maturity. A distinction between true corpora lutea and pseudo-corpora lutea is established, the presence of the former indicates successful oviposition, and of the latter, failure to complete maturation of eggs. Accurate indicators of sexual maturation and reproductive success are of potential value in assessing relative suitability of various hosts for a given flea species and therefore in assessing the degree of host specificity among fleas.

Animals↗
PubMed1991

Cerebral haemorrhage and berry aneurysm: evidence from a family for a pattern of autosomal dominant inheritance.

Although families with several members suffering a cerebral haemorrhage have been reported previously, a family history of this stroke sub-type has not yet been firmly established as a risk factor for the disease. A family in whom cerebral haemorrhage has been clearly documented in five members, spanning three generations, is reported. In three a berry aneurysm was detected. There was no evidence of hypertension among any of the five cases. A sixth member of the family probably died of a cerebral haemorrhage but no necropsy was performed. By using established incidence rates for cerebral haemorrhage in the population, the probability of five such unrelated events arising in any family of similar size and longevity was calculated to be 4.9 x 10(-10). This family strengthens the case that an underlying genetic susceptibility does exist for a proportion of patients who have a cerebral haemorrhage. This susceptibility appears to be consequent upon berry aneurysm formation. The distribution of cases within this family is consistent with an autosomal dominant pattern of inheritance.

Adult↗
PubMed1991

Hindbrain migration after decompression for hindbrain hernia: a quantitative assessment using MRI.

Pre- and post-operative assessments are presented in 17 adult patients who have been treated with craniovertebral decompression for hindbrain herniation, 11 of whom had syringomyelia. Objective improvement in the size of the syrinx was seen in all 11 cases; contrary to expectation the hindbrain more frequently moved downwards than upwards after decompression of the tonsils and creation of an artificial cisterna magna. A method is reported for the quantitative assessment of hindbrain migration using magnetic resonance imaging (MRI). The degree of 'slump', further downward displacement of the hindbrain, was compared with the clinical outcome and the MRI appearances. Slump was more common than expected, although the severity was not usually great enough to produce symptoms. Slump was less marked where the artificial cisterna magna was generous (p less than 0.02). This quantitative method may be useful in assessing patients with unexplained post-operative symptoms and in comparing different surgical techniques.

Adolescent↗
PubMed1991

Using utilization review information to improve hospital efficiency.

Hospitals are currently under great pressure to improve the efficiency of internal operations without sacrificing quality of care. In the rush to do this, they often overlook an extremely useful source of information that already exists--data routinely collected as part of the utilization review (UR) process. This article describes a system using UR data for management purposes that was developed in a large urban teaching hospital. The components described are: (1) data collected systematically by trained reviewers applying the Appropriateness Evaluation Protocol; (2) software for data collection using inexpensive, highly portable computers; and (3) formats for reporting UR findings to hospital administrators and physicians. Information derived from UR in the study hospital is discussed, as well as factors to be considered in adapting some or all of the system's components in other hospitals.

Data Collection↗
PubMed1991

Cell lineage in the cerebral cortex.

We have studied cell lineage in the rat cerebral cortex using retroviral mediated gene transfer. By this method, a marker gene is inserted into dividing precursor cells such that their fate can be followed. We have applied this technique to two types of experiment. First, virus was used to label precursor cells of the cerebral cortex in situ during the period of neurogenesis. Second, cortical precursor cells were grown in dissociated cell culture, and virus was used to follow their development over the culture period. These experiments showed that the majority of precursor cells generate a single cell type--neurones, astrocytes, or oligodendrocytes. Moreover, this is true both in vivo and in dissociated cell culture. The only exception is a bipotential cell, which can generate both neurons and oligodendrocytes. These data suggest that the ventricular zone--the germinal layer of the embryonic cortex--is a mosaic of precursor cells of different restricted potentials. Although precursor cells are restricted in terms of the cell types they generate, they seem not to be restricted in either the cortical laminae or cytoarchitectonic areas to which they can contribute. Both neuronal and grey matter astrocyte precursors contribute cells to multiple layers of both infra- and supragranular laminae. Moreover, in the hippocampal formation, neuronal precursors can contribute cells to more than one hippocampal field.

Animals↗
PubMed1991

Misconduct and fraud in research: social and legislative issues symposium of the Society of University Surgeons.

The symposium was concluded with a question and answer period, which served to clarify and further emphasize the aforementioned issues. Many concerns of coauthorship responsibilities, due process, and potential sanctions were discussed. Moral and ethical issues reflecting the extent of punishment, reporting of misconduct to hospitals and specialty boards, and the almost assured litigation and counter-litigation were approached with considerable apprehension and concern. Misconduct in science will clearly be monitored more closely than in the past. Increasing coauthorship responsibility, conscientious senior investigator supervision, and institutional cooperation will provide the framework to discourage dishonesty in science and encourage proper educational development of both young and established investigators in a milieu of scientific integrity.

Biomedical Research↗
PubMed1990

Reversal of the multidrug resistance phenotype with cremophor EL, a common vehicle for water-insoluble vitamins and drugs.

A polyethoxylated castor oil, Cremophor EL, which is used as a vehicle for p.o. and i.v. administration of water-insoluble compounds in humans, can reverse the multidrug resistance (MDR) phenotype at doses which are likely to be readily achievable clinically. Using flow cytofluorometric analysis of daunorubicin (DNR) uptake as a measure of the expression of the MDR phenotype, Cremophor EL (1:10(3] in the growth medium increased intracellular DNR in an MDR cell line, R100 cells, to levels similar to that observed in the drug-sensitive parental cells, CCRF-CEM. A similar Cremophor EL-induced increase in DNR uptake was also observed in an unrelated MDR cell line derived from K562 cells. Cremophor EL (less than or equal to 3:10(4] did not inhibit the growth of CCRF-CEM cells or its vinblastine-resistant derivative, R100 cells, but would significantly increase the sensitivity of R100 cells to both vinblastine and DNR. Also Cremophor EL did not increase the sensitivity of normal bone marrow progenitor cells cultured in vitro to high concentrations of vinblastine. Cremophor EL may prove to be a relatively pharmacologically inactive addition to chemotherapeutic protocols which may be able to reverse the MDR phenotype in tumors and also help to prevent the selection of MDR cell variants from within a tumor cell population during chemotherapy.

Animals↗
PubMed1990

Constitutional and somatic deletions of two different regions of maternal chromosome 11 in Wilms tumor.

Loss of heterozygosity for 11p markers and preferential loss of maternal alleles have been described in Wilms tumor. In this report we describe the molecular characterization of the constitutional and somatic 11p rearrangements in a del(11p13) WAGR patient with Wilms tumor. Both rearrangements led to loss of maternal alleles for two different regions of 11p, namely, 11p13 and 11p14----p15. This result clearly suggests that Knudson's hypothesis of two hits at the same locus does not necessarily apply to Wilms tumor. Moreover, the loss of 11p15 maternal alleles in the tumor is not incompatible with maternal inheritance of predisposition at 11p13. The putative roles of these two loci are discussed.

Alleles↗
PubMed1990

Post-traumatic syringomyelia, an update.

Post-traumatic and post-arachnoiditic syringomyelia is described in 31 patients from the Midland Centre for Neurosurgery and Neurology (MCNN). It is suggested that the mechanisms may be similar in the two groups and that treatment is best directed to disabling the likely filling mechanisms by opening up the cerebrospinal fluid (CSF) pathways and deliberately leaving the dura open to create an artificial meningocele. It is suggested that drainage on its own is inappropriate but that when drainage of the syrinx is chosen as an ancillary technique then syringopleural drainage may be the procedure of choice.

Adolescent↗
PubMed1990

The initial effects on workload and outcome of a public education campaign on early diagnosis and treatment of malignant melanoma in Leicestershire.

We report our experience of the initial effects of a publicity campaign directed at early presentation of malignant melanoma in Leicestershire. The campaign resulted in a dramatic increase in workload and, at the pigmented lesion clinic, the numbers of new patients rose from 12.3 to 54.5 per clinic. There was a large rise in the number of new melanomas presenting in Leicestershire: from 1.02 per week before the campaign to 1.88 per week in the immediate post-publicity period. This was statistically significant (P less than 0.001). Although there was also an apparently encouraging rise in the percentage of thinner 'good prognosis' tumours, it was not possible to isolate this statistically from a pre-existing trend.

Dermatology↗
PubMed1990

Monitoring tsetse fly populations. I. The intrinsic variability of trap catches of Glossina pallidipes at Nguruman, Kenya.

During 1986 the tsetse fly Glossina pallidipes Austen was monitored daily at Nguruman, southwestern Kenya, using three unbaited biconical traps. This was done to investigate the nature and causes of daily variation in trap catches. The variability of the observed catches was compared to a model which includes the trapping probability and the stochastic variation in the sex-ratio. By comparing the catches of male and female flies we are able to establish the sampling distribution of the trap catches. In addition to seasonal changes in the trap catches, day-to-day variations are observed and these are considered greater than the variation arising from the stochastic nature of the sampling process. Recommendations are made in relation to sampling tsetse fly populations.

Animals↗
PubMed1990

Monitoring tsetse fly populations. II. The effect of climate on trap catches of Glossina pallidipes.

In Part I it was shown that the sampling distribution of trap catches of tsetse flies, Glossina pallidipes Austen, at Nguruman, Kenya, using unbaited biconical traps follows a Poisson distribution. In this paper we examine the effect of humidity and temperature on day-to-day and seasonal variations in the trap catches. It is shown that the seasonal variation is significantly correlated with maximum daily temperature, the catches increasing with temperature when the maximum temperature is below 34 degrees C and decreasing with temperature when it is above 34 degrees C. The correlation between trap catches and relative humidity is not as good as the correlation with the maximum temperature, and the two together do not improve the fit to the trap catches. The day-to-day variation is significantly greater than the intrinsic variation due to the stochastic nature of the sampling process and for some traps it is correlated with temperature and humidity. An autoregressive model gives a half-life for the decay of departures from the mean of about 1 day and it is suggested that this indicates the movement of flies in response to animal movement or to climatic factors other than temperature or humidity. After removing the temperature dependent part of the seasonal variation and the autoregressive component of the data, the male and female catches are still significantly correlated.

Animals↗
PubMed1990

Cerebral abscess.

Explore the source record for details and available documents.

Adolescent↗