Search PubMed⌕ Search

Biomedical subjects

M Wilson

Publications and source records attributed to M Wilson.

At least 397 records · Page 22Linked to original sources
PubMed1995

Effect of dentine and collagen on the lethal photosensitization of Streptococcus mutans.

Suspensions of the cariogenic bacterium, Streptococcus mutans were treated with either toluidine blue O or aluminium disulphonated phthalocyanine and then exposed to light from a helium-neon or gallium-aluminium-arsenide laser, respectively, after passing through demineralized dentine slices. Bacteria were also embedded in a collagen matrix prior to sensitization and exposure to the laser light. When dentine slices were interposed between the laser light and the bacterial suspension, substantial kills (10(7) CFU) were achieved at energy doses of 876, 1,752, and 3,504 mJ with the helium-neon laser and of 1,188, 2,376, and 4,752 mJ with the gallium-aluminium-arsenide laser. There was no apparent relationship between the extent of killing and the degree of demineralization of the dentine. Prolonging the exposure of the sensitized bacteria to the laser light increased the kill achieved. Substantial numbers (10(8) to 10(10) CFU) of S. mutans were also killed when embedded in a collagen matrix and exposed to 438 and 1,314 mJ of helium-neon laser light and 594 and 1,782 mJ of light from the gallium-aluminium-arsenide laser. These results imply that lethal photosensitization may be effective at killing S. mutans in a carious lesion, even when the organism is embedded in demineralized dentine.

Animals↗
PubMed1995

The potent bone-resorbing mediator of Actinobacillus actinomycetemcomitans is homologous to the molecular chaperone GroEL.

Actinobacillus actinomycetemcomitans is a Gram-negative bacterium implicated in the pathology of localized juvenile periodontitis, a condition involving rapid destruction of alveolar bone. We have established that gentle extraction of this bacterium in saline releases a proteinaceous fraction (which we have termed surface-associated material [SAM] which has potent osteolytic activity in the murine calvarial bone resorption assay. Fractionation of the SAM has now revealed that activity is associated with a 62-kD protein. This bone-resorbing activity can be blocked by a monoclonal antibody (raised to the whole bacterium) that is claimed to recognize a protein homologous to the Escherichia coli molecular chaperone GroEL. Purification of this bone-resorbing protein to homogeneity has been achieved by a combination of anion exchange, gel filtration, and ATP-affinity chromatography and the NH2-terminal sequence shows > 95% homology to E. coli GroEL. This GroEL homologue is found in the SAM of A. actinomycetemcomitans but is not found in the osteolytically active SAM from other Gram-negative or Gram-positive bacteria. The GroEL protein from E. coli, but not from Mycobacterium tuberculosis and Mycobacterium leprae, also showed activity in the bone resorption assay. We believe this to be the first observation that a molecular chaperone has the capacity to stimulate the breakdown of connective tissue.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

Fluoride reduces bone strength in older rats.

In response to recent concerns about the effect of water fluoridation on hip fracture rates, we studied the influence of fluoride intake on bone strength. Four groups of rats were fed a low-fluoride diet ad libitum and received 0, 5, 15, or 50 ppm of fluoride in their drinking water. Animals were euthanized after 3, 6, 12, or 18 months of treatment. Mechanical strength of the right femur was measured by three-point bending. Fluoride content for the left femur was measured, and static histomorphometric measurements were made on a lumbar vertebra. Femoral failure load was not significantly decreased in rats treated for 3 and 6 months, but was decreased as much as 23% in rats treated 12 and 18 months at 50 ppm fluoride. Extrapolation from regression equations predicted that older rats lose 36% of femoral bone strength when bone fluoride content is increased from 0 to 10,000 ppm, while younger rats will lose only 15%. Thus, the decreased strength appeared to be due to the combined effects of fluoride intake and age on bone tissue and was not associated with a decrease in bone density or mineralization defects. There were only small effects of fluoride on bone histomorphometry. Fluoride intake at high levels had no negative effects on bone mineralization. Fluoride intake was associated with slight increases in trabecular bone volume and trabecular thickness, but these effects could not be demonstrated consistently. The mechanism by which large amounts of fluoride affect bone strength more severely in older animals is unknown.

Aging↗
PubMed1995

Mycoplasmas in plaque and saliva of children and their relationship to gingivitis.

Gingivitis is common in children but its etiology is not well understood. Results of earlier studies have suggested that mycoplasmas may have a role in the disease. In this study two plaque samples and one stimulated saliva sample were taken from each of a group of sixty (60) 5 to 9 year-old children and cultured selectively for mycoplasmas. Subjects had been selected on the basis of gingival status buccal to the most posterior tooth in an upper quadrant, 20 each having scores 0, 1, or 2 at this site using the Löe and Silness index. Plaque samples were taken from the adjacent tooth surface and from a second posterior site where the adjacent gingiva was free of signs of inflammation. Mycoplasmas were cultured from 54 saliva samples and from 57 plaque samples. Isolation frequency and numbers of mycoplasmas in relation to total anaerobic counts were consistently related to gingivitis scores in both plaque and saliva samples, with higher frequencies and proportions with increasing levels of gingival inflammation at the selected site. In plaque samples this finding held good for both comparisons between groups of subjects and for those between test and control sites within subjects. Findings would appear to confirm the suggestions of earlier studies that mycoplasmas in the oral cavity are associated with gingivitis in children.

Chi-Square Distribution↗
PubMed1995

Seroprevalence of cysticercosis in an Orthodox Jewish community.

Neurocysticercosis cases were identified in 1991 in an Orthodox Jewish community. Transmission was linked to tapeworm-infected immigrant housekeepers from countries where Taenia solium is endemic. To evaluate the extent of and risks for locally acquired cysticercosis, a seroprevalence survey was conducted in 9% of the households in this community. Cysticercosis antibodies were detected in 23 (1.3%) of 1,789 persons from 612 families. All 23 seropositive persons were asymptomatic, and no intracerebral lesions were found for the 21 seropositive persons who underwent brain imaging. Seropositivity was associated with female sex (relative risk [RR] = 2.45, P = 0.049), hiring a domestic worker for child care duties (RR = 3.79, P = 0.05), and with employees from Central America (RR = 2.70, P = 0.0001). Exposure to T. solium in this community is unexpectedly high. Widespread employment of domestic workers from endemic regions and high employee turnover contributes to exposure risk.

Adolescent↗
PubMed1995

Health assessment: a study of registered nurses' knowledge and skill level.

In Australia, there is a paucity of published studies which investigate the role of health assessment in nursing practice. The purpose of the following study was to establish whether registered nurses perceived health assessment to be a central component of their nursing practice. A pre- and post-test design was used to evaluate if any changes were evident in perceived nursing knowledge and skill level following an educational program. The target population was all registered nurses enrolled in a health assessment subject offered in a post-registration Bachelor of Nursing course. A paired, two-tailed t-test showed statistically significant changes in the registered nurses' attitudes towards health assessment. In addition, statistically significant changes were demonstrated in the group's perceived comfortableness with health assessment knowledge and skill level. The results of this project have been used to guide and shape nursing curricula in the area of teaching health assessment.

Clinical Competence↗
PubMed1995

Analysis of immunological alterations associated with testicular prostheses.

PURPOSE: Recipients of silicone gel filled testicular prostheses were evaluated for the possible immunological abnormalities of human adjuvant disease. MATERIALS AND METHODS: Medical record audits were performed for 48 recipients of a silicone gel filled testicular prosthesis. Seven patients consented to a detailed health profile questionnaire, physical examination and serological testing. RESULTS: Retrospective chart analyses and physical examinations were unremarkable. Serological results and questionnaire responses varied. One patient with signs and symptoms suggestive of human adjuvant disease underwent prosthesis removal but adjacent tissues had no evidence of silicosis. Long-term followup was poor. CONCLUSIONS: Immunological alterations were present in 71.4% of examined recipients but they may have been coincidental. Careful followup of recipients of a silicone gel filled testicular prosthesis is needed.

Adolescent↗
PubMed1995

Biological activities of lipopolysaccharides from oral bacteria and their relevance to the pathogenesis of chronic periodontitis.

Chronic periodontitis is a major cause of tooth loss in adults and is a consequence of the colonisation of the subgingival region by organisms such as Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum. Lipopolysaccharide (LPS) is a constituent of the cell walls of all of these bacteria and is found in large quantities on the surfaces of periodontally-diseased teeth. LPS from oral bacteria has a marked effect on most types of cell found in the periodontal tissues including macrophages, lymphocytes, fibroblasts and osteoblasts. Fibroblasts and macrophages respond to oral LPS by secreting a range of cytokines, and other effector molecules, with inflammatory, immunomodulatory and tissue-destroying capabilities. Lymphocytes are stimulated by LPS to produce a wide range of antibodies with different specificities, hence exacerbating the inflammatory response. By its actions on bone cells, LPS can stimulate bone resorption and inhibit bone formation resulting in erosion of the tooth-supporting alveolar bone. There is, therefore, considerable evidence implicating LPS in the pathogenesis of chronic periodontitis. However, the possible involvement of other biologically-active bacterial components must not be overlooked.

Alveolar Bone Loss↗
PubMed1995

Electrogenic Na-Ca exchange clears Ca2+ loads from retinal amacrine cells in culture.

Calcium influx into cultured retinal amacrine cells is followed by a small, slow, inward current that we show here results from the operation of electrogenic Na-Ca exchange. The activity of the exchanger is shown to correlate with the magnitude of the Ca2+ load and to depend on both the Ca2+ and Na+ gradients. Li+ is unable to substitute for Na+ and in the absence of Na+, slow tail currents are almost entirely suppressed. A rapid change in [K+]o does not affect the activity of the exchanger, suggesting that only Na+ and Ca2+ are transported. The ratio of charge entering as Ca2+ current to the charge entering as exchange current is highly variable between cells. We suggest that variability results from a variable fraction of Ca2+ load, we estimate typically 40%, being removed by a process other than Na-Ca exchange. This process is likely to involve internal buffering or sequestration since inhibition of the plasmalemmal Ca(2+)-ATPase does not increase the fraction of Ca2+ expelled by the exchanger. Ca2+ loading performed in the absence of Na+o generates smaller exchange charge the longer the delay in returning Na+o to the neuron. About 30% of exchange charge is lost for a delay of 1 sec.

Animals↗
PubMed1995

In-vitro antibacterial effects of extracts of Nigerian tooth-cleaning sticks on periodontopathic bacteria.

Aqueous extracts from 8 plants used for tooth-cleaning in Nigeria were tested for their ability to inhibit the growth of five periodontopathic bacteria, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Eikenella corrodens and Campylobacter rectus. Extracts of all the plants except that of Massularia acuminata exhibited varying growth inhibitory potentials on the microorganisms. Extract of Terminalia glaucescens showed the widest spectrum of activity, inhibiting the growth of all the tested bacteria except P. gingivalis. These findings corroborate other studies that the plants possess antiplaque properties and suggest that they may be useful tools in preventive dentistry in poor developing countries. However, the bioavailability of the active ingredients of the plants and their long term effects in vivo need to be investigated.

Bacteria↗
PubMed1994

Purification, characterization and analysis of rolipram inhibition of a human type-IVA cyclic AMP-specific phosphodiesterase expressed in yeast.

Analyses were done on a human type-IV cyclic AMP (cAMP) phosphodiesterase (hPDE-IVA-h6.1) expressed in an engineered strain of Saccharomyces cerevisiae. This strain (YMS6) expressed soluble PDE activity, together with an insoluble activity which was not released by re-homogenization, treatment with high-ionic-strength solutions or with the detergent Triton X-100. Pellet and soluble PDE activities were typical of type-IV PDE. They were cAMP-specific, insensitive to the addition of either cGMP (1 microM) or Ca2+/calmodulin, and inhibited by rolipram. Thermostability studies showed both activities to decay as single exponentials, indicating the presence of homogeneous PDE protein species in each fraction. Pellet PDE activity was more thermostable than the soluble enzyme. Mg2+ and Mn2+ dose-dependently increased PDE activity and reversed the inactivating effect of EDTA.h6.1 was engineered to express a C-terminal five-histidine motif (h6.1his5). This allowed purification of the PDE to apparent homogeneity in a simple two-step process involving a rolipram affinity column and a Ni2(+)-chelate column. A single monomeric protein of subunit molecular mass approximately 73 kDa and native molecular mass approximately 74 kDa resulted after a approximately 53000-fold purification. This exhibited a Km for cAMP of 8 microM, a true Vmax. of 0.8 mumol of cAMP hydrolysed/min per mg of PDE protein, a kcat. of 3702 s-1, and a value of the specificity constant kcat/Km of 4.6 x 10(8) M-1.s-1, the last implying a diffusion controlled reaction. Rolipram (Ki 0.4 soluble; 0.7 microM pellet) and 3-isobutyl-1-methylxanthine (Ki 15 soluble; 19 microM pellet) served as simple competitive inhibitors for both soluble and pellet forms of h6.1, respectively.

1-Methyl-3-isobutylxanthine↗
PubMed1994

A novel nonpeptide HIV-1 protease inhibitor: elucidation of the binding mode and its application in the design of related analogs.

HIV-1 protease has been identified as a significant target enzyme in AIDS research. While numerous peptide-derived inhibitors have been described, the identification of a nonpeptide inhibitor remains an important goal. Using an HIV-1 protease mass screening technique, 4-hydroxy-3-(3-phenoxypropyl)-2H-1-benzopyran-2-one (1) was identified as a nonpeptide competitive inhibitor of the enzyme. Employing a Monte Carlo-based docking procedure, the coumarin was docked in the active site of the enzyme, revealing a binding mode that was later confirmed by the X-ray crystal analysis. Several analogs were prepared to test the binding interactions and improve the overall binding affinity. The most active compound in the study was 4,7-dihydroxy-3-[4-(2-methoxyphenyl)butyl]-2H-1-benzopyran-2-one (31).

4-Hydroxycoumarins↗
PubMed1994

The survival story of a child with Ondine's curse in Northland.

The case of a six year old European male with congenital central hypoventilation is reported to illustrate that survival and positive developmental outcome is possible in a remote town in the Northland. Initial and ongoing problems include persistent ventilatory requirement, medical, developmental and psychosocial issues. Positive parental attitude, meticulous care to activities of daily living, medical and psychosocial surveillance and continuing support contribute to the success in management. Various treatment options are also discussed. Primary failure of respiratory regulation, also known as congenital central hypoventilation or Ondine's curse, has been infrequently reported in children. Survival and positive developmental outcome is possible but requires intensive support and positive parental attitude, as well as parental education and ongoing medical and psychosocial surveillance. We report this case to illustrate that this could be achieved even in a remote country town.

Child↗
PubMed1994

The generalist health care workforce: issues and goals.

The generalist health care workforce in the United States is best characterized as those practitioners who deliver primary care services. These include most family physicians, general internists, general pediatricians, nurse practitioners, osteopathic family physicians, and physician assistants. Based on a variety of factors, including health care needs, managed care/HMO hiring practices, international comparisons, and health care costs, the case for increasing the amount and proportion of generalist providers is compelling. Projections strongly suggest a worsening shortfall of generalists if no change is made. Changing the career choices of medical students to promote generalism, even significantly, will take 20 years or more to have a meaningful impact. Therefore, retraining specialist physicians in oversupply to practice as generalists is an important option to consider. To best meet the nation's health care needs, three issues need to be addressed in the context of health care reform: the creation of a "system" of generalist care that integrates into a coherent and collaborative framework the scopes of practice of the various generalist disciplines; the pursuit of a workable short-term model to convert specialist physicians into generalist physicians, led jointly by family medicine, general internal medicine, and general pediatrics, and a significant change in the medical education process to produce an ample supply of well-trained generalists.

Delivery of Health Care↗
PubMed1994

Preparing generalist physicians: the organizational and policy context.

A combination of financial, regulatory, and professional factors have led to a gradual but pronounced decline in generalist training and practice in the United States. This trend is likely to undergo dramatic reversal, however, as reflected by the diverse range of health care reform proposals incorporating incentives to promote generalist education and primary care practice. Considerable consensus has been reached by a number of professional organizations and public policy groups regarding the broad details of reform of generalist physician training, but key areas of controversy remain with important implications for academic medical centers. In addition, the generalist professional organizations, particularly those of family practice, general internal medicine, and general pediatrics, are being challenged to reconcile historic differences in the definitions and training of generalist competence. In this, the cell for "retraining subspecialists" with both offer an opportunity and entail a risk. Finally, academic medical centers will need new organizational structures that can combine the distinctive intellectual traditions and the expertise of the generalist medical disciplines to develop new approaches to the education and practice of primary care.

Academic Medical Centers↗