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Biomedical subjects

D Brown

Publications and source records attributed to D Brown.

At least 1,171 records · Page 65Linked to original sources
PubMedDate not supplied

Response to measles revaccination among Bolivian school-aged children.

The response to measles revaccination was evaluated in 1994 among 202 Bolivian school-aged children whose antibody levels were below 200 miu (milli-international units) by haemagglutination inhibition (HI) in a large-scale serosurvey conducted in Santa Cruz one year earlier. Of the 202 revaccinated children, 164 (82%) had seroconverted between the 1993 serosurvey and the pre-revaccination blood sample. A measles outbreak occurred in Santa Cruz 6 months before the revaccination. Among the seroconvertors, only 6% gave a history of measles, and 15% a history of contact with a case of measles. All 20 children with undetectable HI antibody pre-revaccination, and all 6 children with levels below 100 miu, seroconverted after revaccination. The geometric mean titres by HI at 4 weeks after revaccination were 2018 miu (95% confidence limits [95% CL] 1143, 3564) and 398 miu (95% CL 254, 625) in the 2 groups, respectively. Six of 9 children with pre-revaccination antibody titres of 100-199 miu also seroconverted. No child demonstrated a measles-specific immunoglobulin M response. Among the 29 children who seroconverted and were followed up at one year after revaccination, 15(52%) showed a fourfold or greater decline in antibody levels, which in 8 fell to levels below 200 miu. This study confirmed the observation that revaccination is successful in producing an antibody response in children with low or undetectable pre-revaccination titres, but it also confirmed that vaccine-induced immunity wanes rapidly.

Adolescent↗
PubMedDate not supplied

The influence of protein hormones and conceptus extracts on sheep lymphocyte transformation induced in vitro.

The study describes the effects of crude extracts of the fetal membranes of day 25 sheep conceptuses and of certain purified protein hormones and pregnancy-associated antigen on the mitogen-induced response of sheep peripheral blood lymphocytes (PBL) in vitro. A dose-dependent suppression of the proliferative response of PBL to phytohaemagglutinin, pokeweed mitogen and concanavalin-A was seen when cultures were supplemented with a soluble extract of fetal membranes. Preliminary characterization suggested that the suppressive agent was heat stable and dialysable. These properties distinguished the immunosuppressive component of membrane extracts from ovine pregnancy-associated antigen, which is heat labile and non-dialysable. However, both high and low molecular weight forms of ovine pregnancy associated antigen were also shown to inhibit lymphocyte transformation in vitro. In contrast, ovine luteinizing hormone, prolactin, growth hormone and human placental lactogen were inactive. The findings are consistent with the hypothesis that immunosuppressive substances are present in the gravid uterus during early pregnancy in the sheep.

Animals↗
PubMedDate not supplied

Dental materials: 1995 literature review.

This critical review of the published literature on dental materials for the year 1995 has been compiled by the Dental Materials Panel of the United Kingdom. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, resin composites, dentine bonding, dental amalgam, endodontic materials, casting alloys, investment materials, resin-bonded bridges and ceramo-metallic restorations, all ceramic restorations, denture base and soft lining materials, impression materials, dental implants, orthodontic materials and biomechanics). Three hundred and thirty articles published in 68 titles have been reviewed.

Biomechanical Phenomena↗
PubMedDate not supplied

Vasopressin stimulates formation of coated pits in rat kidney collecting ducts.

The water permeability of collecting ducts is greatly increased by the antidiuretic hormone, vasopressin. This permeability increase is associated with the appearance of intramembrane particle (IMP) clusters on the luminal plasma membranes of principal cells of the collecting duct epithelium. IMP aggregates have also been related to an increase in water permeability of two other vasopressin-sensitive epithelia, the amphibian urinary bladder and the amphibian epidermis, and it has been proposed that these specialized membrane domains might represent specific water-permeable membrane patches, induced by the hormone in their respective epithelia. Using a cytochemical probe for membrane cholesterol, filipin, we show here that the membrane patches in rat kidney are selectively devoid of filipin-sterol complexes and that when identified in thin sections, they have a cytoplasmic bristle coat: both of these features are characteristics of coated pits which, in other systems, are involved in receptor-mediated endocytosis. We also show that vasopressin induces the appearance of coated pits on collecting duct luminal membranes in Brattleboro homozygous rats, which have hereditary diabetes insipidus.

Animals↗
PubMedDate not supplied

Should colon-penetrating small missiles be removed? An experimental study of retrocolic wound tracks.

Small-fragment injury to the colon may occur in approximately 5% of battlefield casualties. The surgical management aims to reduce the risk of retrocolic infection and provide optimal conditions for colonic wound healing. This study aimed to quantify the risk of retrocolic infection. Steel fragments were fired through exteriorized porcine colon and caught in 20% gelatin. The fragments, and resultant tracks, were extracted and subjected to quantitative bacteriological examination to determine the extent of contamination. The median bacterial count for complete tracks was 1.2 x 10(4) CFU/g (interquartile range 1.8 x 10(3) to 2.7 x 10(4)). Counts were highest in the initial 1 cm of the track and reduced along its length. This study does not support wound track excision or missile fragment removal in cases of retrocolic trauma following penetrating colonic injury. Either or both procedures will increase local trauma and are likely to prejudice colonic wound repair.

Animals↗
PubMedDate not supplied

Control of virtual environments for young people with learning difficulties.

PURPOSE: The objective of this research is to identify the requirements for the selection or development of usable virtual environment (VE) interface devices for young people with learning disabilities. METHOD: A user-centred design methodology was employed, to produce a design specification for usable VE interface devices. Details of the users' cognitive, physical and perceptual abilities were obtained through observation and normative assessment tests. CONCLUSIONS: A review of computer interface technology, including virtual reality and assistive devices, was conducted. As there were no devices identified that met all the requirements of the design specification, it was concluded that there is a need for the design and development of new concepts. Future research will involve concept and prototype development and user-based evaluation of the prototypes.

Adolescent↗
PubMedDate not supplied

How tutors assist adults with learning disabilities to use virtual environments.

PURPOSE: To describe strategies used by tutors teaching adults with learning disabilities to use desktop virtual environments and to investigate their effectiveness by examining changes over time in tutor and learner behaviour. METHOD: Twenty adults with learning disabilities spent 12 sessions with one of four non-disabled tutors learning to use desktop virtual environments designed to teach independent living skills. Sessions were recorded on videotape, categories of behaviour were described and tapes analysed for frequency of tutor behaviours and goals achieved by learners. RESULTS: Tutor strategies were described in terms of whether they aimed to help the learner master the interaction devices or to navigate and achieve goals in the virtual environments and how directive they were. There were some differences between tutors but this did not relate to whether tutors were experienced users themselves of the environments or were initially unfamiliar with them. Goal achievement was maintained at a constant level while help with the interaction devices and specific information about the environment decreased over repeated sessions. Rates of non-specific information did not change. CONCLUSIONS: Pretraining with the interaction devices would free both tutor and learner to concentrate on achieving goals in the environments. Much of the specific help given by the tutor could be incorporated into the software.

Adult↗
PubMedDate not supplied

Patterns of referral for children with speech disorders.

This paper presents information about a sample of 200 children aged 3-6 years in four Health Authorities. They were referred routinely for speech therapy. Age of referral, distribution within the family, sex and sources of referral are indicated and discussed.

Birth Order↗
PubMedDate not supplied

CHARGE association looking at the future--the voice of a family support group.

CHARGE association is a non-random collection of congenital anomalies. The condition is becoming more widely known to medical and educational professionals. The number of children diagnosed is increasing, probably because of the greater awareness of this condition. This paper considers some of the long-term management problems which are often deferred in the early months, when acute life threatening problems take priority. Questionnaires were sent to parents via the CHARGE Association Family Support Group, UK. Thirty-nine were returned and incomplete information was sought by personal contact or telephone. The majority of children were known professionally to one or both authors and information was therefore checked from medical and educational notes. There is still widespread misunderstanding about the impact of multiple disability, especially when this includes multi-sensory impairment, on the early development of the child. Therefore, the information collected from the study has been from an educational and medical perspective, thereby aiding the understanding of these complex problems. At the parents request, information was gathered about certain teratogens, of which Lindane, an organophosphate, is highlighted.

Abnormalities, Multiple↗
PubMedDate not supplied

Differential actin isoform reorganization in the contracting A7r5 cell.

In the present study, we investigated the reorganization of alpha- and beta-actin in the contracting A7r5 smooth muscle cell. The remodeling of these actin variants was markedly different in response to increasing concentrations of phorbol 12, 13-dibutyrate (PDBu). At the lowest concentrations (< or =10(-7) mol/L), cells showed an approximately 70% loss in alpha-actin stress fibers with robust transport of this isoform to podosomes. By comparison, beta-actin remained in stress fibers in cells stimulated at low concentrations (< or =10(-7) mol/L) of PDBu. However, at high concentrations (> or =10(-6)mol/L) approximately 50% of cells showed transport of beta-actin to podosomes. Consistent with these findings, staining with phalloidin indicated a significant decrease in the whole-cell content of F-actin with PDBu treatment. However, staining with DNase I indicated no change in the cellular content of G-actin, suggesting reduced access of phalloidin to tightly packed actin in the podosome core. Inhibition of protein kinase C (staurosporine, bisindolymaleimide) blocked PDBu-induced (5 x 10(-8) mol/L) loss in alpha-actin stress fibers or reversed podosome formation with re-establishment of alpha-actin stress fibers. By comparison, these inhibitors caused partial loss of beta-actin stress fibers. The results support our earlier conclusion of independent remodeling of alpha- and beta-actin cytoskeletal structure and suggest that the regulation of these structures is different.

Actins↗