PubMed Health⌕ Search

Biomedical subjects

A Burt

Publications and source records attributed to A Burt.

At least 37 records · Page 2Linked to original sources
PubMed1997

Molecular markers reveal differentiation among isolates of Coccidioides immitis from California, Arizona and Texas.

Coccidioides immitis causes coccidioidomycosis, a fungal disease of both immuno-compromised and otherwise healthy people; it is capable of causing large epidemics and the disease is often refractory to chemotherapy. To quantify the magnitude of population differentiation and estimate levels of gene flow in C. immitis, multilocus genotypes were scored for 20-25 clinical isolates from each of Bakersfield (California), Tucson (Arizona), and San Antonio (Texas). The molecular markers used were PCR products with polymorphic restriction endonuclease sites, found and characterized in a previous study of the Tucson population. The data show very highly significant differences in allele frequencies between all three populations, and suggest very low levels of migration between populations. One isolate in the San Antonio sample was an outlier, showing the California-specific allele at all four of the loci distinguishing the two populations, and subsequent inquiries indicated that the infection had indeed been acquired in California. Thus, genetic information can be used to infer the geographical origin of a fungal infection.

Arizona↗
PubMed1996

Molecular markers reveal cryptic sex in the human pathogen Coccidioides immitis.

Coccidioides immitis, cause of a recent epidemic of "Valley fever" in California, is typical of many eukaryotic microbes in that mating and meiosis have yet to be reported, but it is not clear whether sex is truly absent or just cryptic. To find out, we have undertaken a population genetic study using PCR amplification, screening for single-strand conformation polymorphisms, and direct DNA sequencing to find molecular markers with nucleotide-level resolution. Both population genetic and phylogenetic analyses indicate that C. immitis is almost completely recombining. To our knowledge, this study is the first to find molecular evidence for recombination in a fungus for which no sexual stage has yet been described. These results motivate a directed search for mating and meiosis and illustrate the utility of single-strand conformation polymorphism and sequencing with arbitrary primer pairs in molecular population genetics.

Base Sequence↗
PubMed1996

Clinical isolates of Histoplasma capsulatum from Indianapolis, Indiana, have a recombining population structure.

A sample of 30 clinical isolates of Histoplasma capsulatum was analyzed to determine (i) whether genetic exchange is important in the life cycle of this fungus and (ii) whether distinct subpopulations which correlate with disease severity or host immune status exist. Eleven biallelic molecular markers were developed, with the frequency of the least common allele at each molecular locus ranging from 10 to 50%. Every isolate had a different, unique multilocus genotype. Data analysis indicated that frequent recombination occurs within the Indianapolis, Ind., population. There were no associations between isolates from the immunocompromised population or from those with different clinical manifestations of histoplasmosis.

Genes, Fungal↗
PubMed1996

Non-Hodgkin's lymphoma and hepatitis C virus infection.

The hepatitis C virus (HCV) is a recently described and important cause of acute and chronic liver disease. A hallmark of HCV is its propensity to become chronic, some patients with chronic HCV progressing to cirrhosis and hepatocellular carcinoma (HCC). HCV is also lymphotrophic and we report 2 patients with HCV cirrhosis who developed non-Hodgkins lymphoma (NHL). These cases raise the possibility that chronic HCV infection of lymphocytes plays an aetiological role in this malignancy. However screening of a further 63 consecutive patients over the age of 50 years with NHL for HCV antibody by second generation enzyme linked immunoassay (ELISA) failed to identify any patients with evidence of HCV infection. This suggests that HCV is an uncommon contributory factor for the development of non-Hodgkins lymphoma in the United Kingdom.

Aged↗
PubMed1995

Outcomes of hand surgery. British Society for Surgery of the Hand.

The findings are presented of a conference on Outcomes of Hand Surgery organized by the audit committee of British Society for Surgery of the Hand in 1993. Measures of outcome in terms of movement, power, sensibility, pain, activities of daily living, complications and patient satisfaction are considered, and an example of a patient evaluation measure given as an appendix.

Adult↗
PubMed1994

Refractory obsessive compulsive disorder and ECT.

The authors review their experience with electroconvulsive therapy (ECT) in 32 patients meeting DSM-IIIR criteria for obsessive compulsive disorder. All patients had received extensive behavioral and cognitive therapy and pharmacotherapy prior to the initiation of ECT without apparent benefit. Following ECT, most subjects showed considerable improvement in obsessive compulsive symptoms and remained improved up to 1 year after therapy. Some patients also showed short-term improvements on several measures of depression. The change in obsessive compulsive symptoms, however, appeared to be independent of changes in measures of depression.

Depressive Disorder↗
PubMed1992

Sources of variance in protein heterozygosity: the importance of the species-protein interaction.

We report on a detailed survey of protein heterozygosity in Canadian freshwater fish and mammals. A simple one-way analysis showed substantial variance among species. However, a two-way analysis of species and proteins showed that there was little if any variance among species or among proteins, but a very large species-protein interaction. We could not remove this interaction by analysing taxa separately by constructing completely balanced datasets, by eliminating study bias or by excluding monomorphic proteins, and we could not decompose the interaction by classifying enzymes according to their form and function. We conclude that most of the variance in protein heterozygosity is attributable to species-protein interaction. This casts some doubt on the interpretation of comparative studies of mean heterozygosity among species or among proteins. Our result seems inconsistent with the neutral theory of protein variation but not with the differential action of natural selection.

Analysis of Variance↗
PubMed1992

'Concealed ovulation' and sexual signals in primates.

The absence of conspicuous sexual signals in some primates, particularly humans and vervets, has been interpreted as evidence that females of these species are 'concealing' ovulation from males. This conclusion is unjustified: the null hypothesis of no adaptation, that the absence of conspicuous sexual signals has resulted from the absence of selective pressures maintaining such adaptations, is both more parsimonious and better fits the facts. The related suggestion that there has been adaptation among females to conceal ovulation from their own consciousness is also unjustified. What, then, maintains sexual signals in those species that do have them? Many proposed hypotheses for the function of sexual signals do not account for their most puzzling feature: their conspicuousness. According to current theory on the evolution of communication, two explanations seem most plausible: conspicuous sexual signals function to communicate to distant receivers and/or to convince reluctant receivers. There is some empirical support for both hypotheses, but not overwhelming support for either.

Adaptation, Physiological↗
PubMed1991

Role of the visual input in recovery of function following unilateral vestibular lesion in the goldfish. I. Short-term behavioural changes.

Vestibular compensation, i.e. the partial or complete recovery of function following lesion of a labyrinth, has been suggested to be based on a multisensory substitution process involving vestibular, visual and somatosensory information. Teleost fish would seem ideal subjects for testing this proposal, because equilibrium orientation in the intact animal is largely under the bimodal control of the vestibular and visual systems. The role of the visual input in the compensation of behavioural deficits elicited by hemilabyrinthectomy (HL) was studied in goldfish maintained over the first two postoperative hours under different lighting conditions. HL caused severe postural and locomotory symptoms, which were the same or similar under all lighting conditions. The rate at which the various deficits disappeared, however, was dependent not only on the presence of light but also on its direction of incidence. Animals maintained under overhead illumination reached the criterion of successful compensation (completion of 5-min continuous and unimpaired swimming) within 10 min, whilst under unilateral illumination (90 degrees to the vertical) the time to criterion was significantly increased; animals exposed to illumination from below or infra-red illumination showed little or no signs of compensation up to 2 h after HL. It is concluded (1) that the immediately postoperative stage of vestibular compensation in the goldfish represents an integral part of the recovery process, within which all observable deficits can be compensated with remarkable rapidity; and (2) that the visual input is both necessary and sufficient for the compensation of the immediately postoperative deficits. We term this early stage of recovery the 'acute' phase and consider it to be based on a visual substitution process, whereby the missing labyrinthine input to the (partially) deafferented vestibular neurons is functionally replaced by visual afferents.

Animals↗
PubMed1991

Role of the visual input in recovery of function following unilateral vestibular lesion in the goldfish. II. Long-term behavioural changes.

Previous behavioural studies in our laboratory have demonstrated that the visual input is both necessary and sufficient for the acquisition of the acutely compensated state following hemilabyrinthectomy (HL) in the goldfish. Here we examine the role of the visual input in the maintenance of the compensated state. Exposure of acutely compensated animals to illumination from below (IFB) or infra-red illumination (IRI) elicited a decompensation: whereas IRI was no longer effective 4 days after HL, the susceptibility to IFB disappeared slowly over a number of weeks. Exposure of acutely compensated animals to unilateral illumination (UI) induced a highly asymmetrical dorsal light response 1 day after HL: tilt towards the ipsilateral side was extreme, whilst tilt towards the contralateral side was similar to preoperative values. This pronounced side difference decreased rapidly over the next 3 days and then more slowly over the following weeks and months. The findings show (1) that the maintenance of the acutely compensated state is temporarily dependent not only on the presence of light but also on its direction of incidence; and (2) that the visual-vestibular integration governing posture and locomotion is strongly biased in favour of the visual input to the lesioned side during the early postoperative period and subsequently returns to near preoperative values. The present results are compatible with the hypothesis that acute vestibular compensation in the goldfish is based on a visual substitution process. The latter is not permanent, however, the chronic course of compensation being characterized by a progressive decrease in reliance on visual cues. The observed changes in visual-vestibular integration with time are assumed to reflect modifications in inter- and/or extra-vestibular commissural systems by which the intact labyrinth gradually strengthens its control over the deafferented nuclear complex.

Animals↗
PubMed1989

In vitro differentiation of fat-storing cells parallels marked increase of collagen synthesis and secretion.

Fat-storing cells were isolated and purified from livers of normal adult rats and maintained in primary culture. By light and electron microscopy it was established that they underwent phenotypic changes into cells with the ultrastructural characteristics of myofibroblasts, between the third and sixth day in culture. These morphological changes were accompanied by a 2-fold increase of L-[3H]proline incorporation into secretory proteins and an 11-fold increase into secreted collagenase-sensitive proteins. In contrast, incorporation into cell layer-associated proteins and into cell layer-associated collagenase-sensitive proteins was not significantly elevated. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in combination with fluorography, demonstrated that the main collagen type secreted by the myofibroblast-like cells was collagen type I. Collagen types III and IV, and fibronectin were present in lesser amounts. The similarity between the well known in vivo alterations of fat-storing cells under pathological conditions and the spontaneous in vitro differentiation described in this study, makes primary cultures of fat-storing cells a valuable tool for studying their role in chronic liver disease.

Adipose Tissue↗
PubMed1988

Early mobilisation of patients with cervical cord injury using the halo brace device.

The halo brace device for cervical spine stabilisation has been in use predominantly in North America since 1959. It has not yet found widespread use for the management of the spinal cord injured in the UK. At the Yorkshire Regional Spinal Injuries Unit we have used the device over 2 years on 20 patients with complete and incomplete traumatic cervical spinal cord injuries, and compared our results with those for the previous 20 patients with similar injuries treated with skull calipers and bed rest. Patients using a halo brace device begin more active rehabilitation earlier as they are mobilised on average 5 weeks earlier than those whose traction is administered via skull calipers. Halo brace patients begin weekend leave usually within 7 weeks of their injury compared to 14 weeks post-injury for caliper treated patients and were discharged on average 2 months earlier than the comparison group. We believe that earlier mobilisation, weekend leave and discharge for halo brace patients in the absence of any neurological deterioration afford significant physical, psychological and management benefits.

Bed Rest↗
PubMed1988

Quadriplegic care: an assessment of the impact of the carer.

Thirty-three voluntary carers living with dependent quadriplegics completed a questionnaire survey which recorded their views on the assistance they received. Disruption to sex life, wheelchair restrictions, personality change in the quadriplegic person, and problems with bladder care were the features they most disliked. We have introduced a self-help group. Respite care would assist them with the valuable service they provide at considerable personal cost.

Activities of Daily Living↗
PubMed1987

Cultured epithelium as a skin substitute.

Twenty-five burn patients with full or partial thickness skin loss received cultured epithelium (CE), allografts or autografts as part of their treatment. Overall, a 30 per cent graft 'take' was achieved irrespective of whether the CE was autograft or allograft, fresh or frozen. In the case of deep dermal burns this figure improved to 50 per cent. The surviving grafts merged with split thickness skin grafts (SSG) and advancing wound edges. When full thickness skin loss was grafted, only a patchy take could be achieved and the surviving islands of CE tended not to spread across the wound. No rejection of CE allograft was recorded either clinically or histologically up to 6 months. The technical problems and clinical implications are discussed.

Adult↗