Search PubMed⌕ Search

Biomedical subjects

M Wilson

Publications and source records attributed to M Wilson.

At least 613 records · Page 34Linked to original sources
PubMed1986

Identity of limulus amoebocyte lysate-active root surface materials from periodontally involved teeth.

A new approach has been developed to circumvent the problems of false positive reactions in the Limulus Amoebocyte Lysate (LAL) assay for lipopolysaccharide (LPS) in root surface materials. These LAL-reactive materials include thrombin, thromboplastin, ribonuclease, ribonucleic acid, lipoteichoic acid and peptidoglycan fragments. In the present study, hot phenol/water extraction of these substances followed by ultracentrifugation of the resulting aqueous phases reduced their concentrations to very low levels. Furthermore, the application of Polymyxin B/Sepharose 4B affinity chromatography to these extracts enabled their intrinsic LAL-activity to be determined. Use of these techniques to assay root surface materials has identified LPS as being the major LAL-reactive material present. The mean LPS yield for the periodontally involved teeth was 4.13 micrograms/tooth, representing 2.82 micrograms/root. In contrast, the mean yield of LPS for the periodontally uninvolved teeth was 3.12 ng/tooth.

Adult↗
PubMed1986

The distribution of bacterial lipopolysaccharide (endotoxin) in relation to periodontally involved root surfaces.

The distribution of lipopolysaccharide (LPS) in periodontally involved root surface associated materials has been investigated using improved methods of identification and quantification. 39% of the LPS could be removed by gently washing in water for 1 min and 60% by brushing for 1 min with a slowly rotating bristle brush. The finding that 99% of the LPS can be removed by comparatively gentle procedures suggests that effective root surface debridement may be achieved by methods other than traditional hand instrumentation.

Chromatography, Affinity↗
PubMed1986

Demonstration of thyrotrophin beta-subunit messenger RNA in rat pituitary cells in primary culture--evidence for regulation by thyrotrophin-releasing hormone and forskolin.

We have reported previously the effect of thyroid status in vivo on pituitary cytoplasmic concentrations of messenger RNA (mRNA) encoding the thyrotrophin (TSH) beta-subunit (Franklyn, Lynam, Docherty et al, 1985). Studies in vitro of the regulation of TSH beta gene transcription have been confined to thyrotrophic tumour cells. We now report the demonstration of TSH beta-subunit mRNA in non-tumorous rat pituitary cells in primary culture. Treatment of cells with thyrotrophin-releasing hormone (TRH) and with forskolin resulted in a marked increase in cellular concentration of TSH beta-mRNA. These results suggest that TRH exerts a direct effect on the pretranslational events involved in TSH synthesis and further that the adenylate cyclase system may be involved in the regulation of synthesis. We have thus described a novel system for the study of TSH beta-subunit gene expression in normal rat pituitary cells in vitro.

Animals↗
PubMed1986

Interpersonal influences in adolescent drug use--the role of older siblings, parents, and peers.

Drawing data from the first year of a longitudinal study of 508 families with focal adolescents aged 11 to 13 years and their older siblings (14 to 18 years), the investigators examined the influence of older siblings' drug-using attitudes and behaviors, in comparison with parental and peer drug-using attitudes and behaviors, on focal adolescents' nonuse and use of substances. Older siblings are frequently a source of drugs and use substances with their young siblings, though peers remain the primary source and the most frequent coursers. For most substances, frequency of use was predicted by older sibling and peer substance use, each after controlling for the other. Parental drug use was found to be minimal in comparison to older siblings and peers. Findings relative to the potentially important role of older siblings in influencing their younger siblings' drug-using behavior are discussed.

Adolescent↗
PubMed1986

In vitro inhibition of lipopolysaccharide-induced bone resorption by polymyxin B.

Lipopolysaccharide (LPS) purified from Haemophilus actinomycetemcomitans stimulates resorption and inhibits collagen synthesis in mouse calvaria bones in vitro. Addition of polymyxin B caused a dose-related inhibition of LPS-stimulated bone resorption and reversal of the inhibition of collagen synthesis. A polymyxin B to LPS ratio of 2:1 prevented bone resorption and restored collagen synthesis to control levels. The activity of polymyxin B was specific for LPS as bone resorption induced by prostaglandin E2 or parathyroid hormone was unaffected at similar concentrations. These results indicate that polymyxin B and its analogues may have potential in the treatment of periodontal disease by reducing bone loss induced by lipopolysaccharides.

Animals↗
PubMed1986

Amoxycillin-resistant streptococci in dental plaque.

This investigation was undertaken to study the prevalence of amoxycillin-resistant oral streptococci in normal healthy patients and patients with a cardiac condition, susceptible to infective endocarditis. Samples of supragingival dental plaque were collected from two test groups, children with congenital heart disease and adults with a history of rheumatic fever, and two control groups comprising normal healthy children and normal healthy adults. Bacteria from these samples were grown on a medium selective for oral streptococci, as well as on the same medium containing known concentrations of amoxycillin. The results indicate that a high percentage of rheumatic heart patients and children with congenital heart disease harboured amoxycillin-resistant oral streptococci. The level of amoxycillin resistance in the plaque of adults with rheumatic heart disease was significantly greater than in that of normal adults. In view of the high percentage of patients at risk harbouring amoxycillin-resistant streptococci, it is important that the individual clinical situation be monitored. Perhaps antibiotic sensitivity tests should be performed to select an appropriate antibiotic for prophylaxis of infective endocarditis.

Adolescent↗
PubMed1985

The effect of light on the spread of signals through the rod network of the salamander retina.

Adjacent rods in the amphibian retina are electrically coupled to each other by gap junctions. By injecting current pulses into one rod and recording the voltage change produced in nearby rods, we have studied the extent to which signals spread between rods in the presence and absence of illumination. Light has little effect on the steady potentials produced in nearby rods by the injection of a hyperpolarizing current, but does affect the propagation of transient signals through the rod network. The responses to injection of depolarizing current are increased by light. These effects of light were mimicked by hyperpolarizing the rod network (non-uniformly) by injecting continuous current (on top of which current pulses were superimposed to monitor signal spread). This suggests that the effects of light are due solely to the rod hyperpolarization produced by light. The effects of light are not completely predicted from computer simulations based on a previous characterization of the properties of isolated rods; these experiments thus reveal an inadequacy in the description of the rod membrane currents in that model. Light-induced hyperpolarization of cones has no effect on signal spread between rods. The functional significance of these results is discussed.

Ambystoma↗
PubMed1985

Ontogeny of human T and B lymphocytes during stressed and normal gestation: phenotypic analysis of umbilical cord lymphocytes from term and preterm infants.

Cord blood lymphocytes from premature and stressed term infants were phenotyped and contrasted with T and B lymphocytes from healthy newborns at term. Cytofluorometric analysis shows that in the early third trimester, 80-85% of fetal T cells belong to the T4+ inducer population, and 10% to the T8+ suppressor/cytotoxic subset. As gestation progresses, the T4:T8 ratio shifts toward adult values and there is an increase in expression of the mature antigen, T12. The B-cell-differentiation antigens B1, B2, and B4 do not appear to change during gestation in healthy infants. Antenatal stress which threatens fetal survival, however, leads to circulating cells of both lineages which are phenotypically less mature than expected for gestational age. Most notably, in response to severe antenatal hypoxic stress, cells expressing the very early B-cell markers B2 and B4 increase and exceed the numbers of more mature B1+ cells in cord blood.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1985

The penetration of detergents into adult and infant eyes: possible hazards of additives to ophthalmic preparations.

In studies of surfactant penetration into the eye, radiolabelled detergent was found to penetrate the rabbit cornea, to accumulate readily in ocular tissues and to be released slowly. Repeated applications led to increasing binding of the detergent. Permeability, ocular and systemic uptake and retention were all greater in juvenile than in adult rabbits. Preliminary tests of the effects of surfactants on ocular cells in vitro using concentrations found in vivo, suggest that some low-level effects might occur, particularly in juveniles.

Age Factors↗
PubMed1985

Extra intestinal influences on exhaled breath hydrogen measurements during the investigation of gastrointestinal disease.

During the clinical investigation of patients with gastrointestinal disease by exhaled breath hydrogen measurement, the occurrence of inexplicable variations in recorded hydrogen values led to a search for extra intestinal factors which were capable of adversely influencing breath hydrogen concentration and impairing the diagnostic accuracy of the test. Serial breath samples were collected from normal subjects under a variety of conditions which might occur during routine clinical study, including, hyperventilation, exercise, cigarette smoking, and carbohydrate ingestion. Breath hydrogen concentrations were consistently reduced by hyperventilation (p less than 0.01) and exercise (p less than 0.05). Cigarette smoking, in contrast, caused a marked rise in measured breath hydrogen (p less than 0.01), as did oral carbohydrate (p less than 0.05). Prior bactericidal mouthwash abolished this carbohydrate associated rise, suggesting that the hydrogen was the result of fermentation by oropharyngeal bacteria. Because, in all instances, the changes in breath hydrogen were of sufficient magnitude to interfere with data interpretation, it is recommended that these factors are eliminated, whenever possible, from conditions of study.

Bacteria, Anaerobic↗