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Biomedical subjects

A Harrison

Publications and source records attributed to A Harrison.

At least 37 records · Page 2Linked to original sources
PubMed2001

The Tctex1/Tctex2 class of dynein light chains. Dimerization, differential expression, and interaction with the LC8 protein family.

The Tctex1/Tctex2 family of dynein light chains associates with the intermediate chains at the base of the soluble dynein particle. These components are essential for dynein assembly and participate in specific motor-cargo interactions. To further address the role of these light chains in dynein activity, the structural and biochemical properties of several members of this polypeptide class were examined. Gel filtration chromatography and native gel electrophoresis indicate that recombinant Chlamydomonas flagellar Tctex1 exists as a dimer in solution. Furthermore, yeast two-hybrid analysis suggests that this association also occurs in vivo. In contrast, both murine and Chlamydomonas Tctex2 are monomeric. To investigate protein-protein interactions involving these light chains, outer arm dynein from Chlamydomonas flagella was cross-linked using dimethylpimelimidate. Immunoblot analysis of the resulting products revealed the interaction of LC2 (Tctex2) with LC6, which is closely related to the highly conserved LC8 protein found in many enzyme systems, including dynein. Northern dot blot analysis demonstrated that Tctex1/Tctex2 family light chains are differentially expressed both in a tissue-specific and developmentally regulated manner in humans. These data provide further support for the existence of functionally distinct populations of cytoplasmic dynein with differing light chain content.

Amino Acid Sequence↗
PubMed2001

Utility of B-type natriuretic peptide in the diagnosis of congestive heart failure in an urgent-care setting.

OBJECTIVES: The goal of this study was to evaluate the utility of a rapid "bedside" technique for measurement of B-type natriuretic peptide (BNP) in the diagnosis of congestive heart failure (CHF) in an urgent-care setting. BACKGROUND: B-type natriuretic peptide is a protein secreted from the cardiac ventricles in response to pressure overload. One potential application of measurements of BNP in blood is distinguishing dyspnea due to CHF from other causes. METHODS: B-type natriuretic peptide concentrations were measured in a convenience sample of 250 predominantly male (94%) patients presenting to urgent-care and emergency departments of an academic Veteran's Affairs hospital with dyspnea. Results were withheld from clinicians. Two cardiologists retrospectively reviewed clinical data (blinded to BNP measurements) and reached a consensus opinion on the cause of the patient's symptoms. This gold standard was used to evaluate the diagnostic performance of the BNP test. RESULTS: The mean BNP concentration in the blood of patients with CHF (n = 97) was higher than it was in patients without (1,076 +/- 138 pg/ml vs. 38 +/- 4 pg/ml, p < 0.001). At a blood concentration of 80 pg/ml, BNP was an accurate predictor of the presence of CHF (95%); measurements less than this had a high negative predictive value (98%). The overall C-statistic was 0.97. In multivariate analysis, BNP measurements added significant, independent explanatory power to other clinical variables in models predicting which patients had CHF. The availability of BNP measurements could have potentially corrected 29 of the 30 diagnoses missed by urgent-care physicians. CONCLUSIONS: B-type natriuretic peptide blood concentration measurement appears to be a sensitive and specific test to diagnose CHF in urgent-care settings.

Aged↗
PubMed2001

Understanding safe sex: gender narratives of HIV and pregnancy prevention by rural South African school-going youth.

In South Africa's HIV/AIDS epidemic, young people, especially women, are at high risk due to an apparent gap between awareness and practice. In repeated peer group discussions with girls aged 14-15 and boys aged 16-19, we explored influences on safe sex behaviour. Separate male and female safe sex paradigms emerged, with boys less likely to perceive themselves as 'at risk' and more likely to use condoms. Girls had not used condoms, would have preferred to delay sexual relationships and feared pregnancy as well as HIV/AIDS. Both sexes deemed it difficult for girls to initiate condom use, although both sexes viewed condoms favourably. Girls saw condoms as a sign of love and protection, whereas boys tended to use them with casual partners. A lack of decision-making autonomy within relationships further constrained girls' ability to practice safer sex. Involvement of peer participants in review of their own narrative data helped to ensure representation of participants' voices in the findings. Overall, these findings point to the need for programmes to address gender inequalities and emphasise behavioural skills in the years before sexual activity begins.

Adolescent↗
PubMed2001

The effect of the addition of surface treated chopped and continuous poly (methyl methacrylate) fibres on some properties of acrylic resin.

Poly (methyl methacrylate), the material most commonly used in the construction of dentures, is not without limitations particularly in terms of mechanical strength, such as flexural and fatigue strength. The Dental Practice Board for England statistics show that many dentures fail as a result of fracture. This study investigated the self-reinforcement of acrylic resin through the addition of surface treated poly (methyl methacrylate) fibres in chopped and continuous form. The effect of the addition of fibres on transverse and impact strengths was investigated. The addition of surface treated chopped or continuous fibres to acrylic resin did not improve the transverse or impact strengths. The addition of surface treated poly (methyl methacrylate), in the present form, to acrylic resin cannot be recommended as a method of reinforcement.

Acrylic Resins↗
PubMed2001

An assessment of the ability of dental undergraduates to choose artificial teeth which are appropriate for the age and sex of the denture wearer: a pilot study.

One of the main objectives in selecting and arranging artificial teeth is to produce prostheses which defy detection. With an appropriate degree of clinical experience and expertise it should be a relatively straightforward procedure to select a suitable artificial tooth mould. However, for the relatively inexperienced dental undergraduate it can be a challenging process. The aim of this study was to assess the ability of dental undergraduates to select artificial teeth which are appropriate for the age and sex of the denture wearer. One hundred and fifty dental undergraduates aged 18-35 were asked to complete a questionnaire to assess their attitudes towards artificial tooth selection and asked to correctly identify six artificial tooth arrangements according to age and sex. The results showed that a large percentage of dental undergraduates at Bristol experience difficulty in selecting artificial teeth which are appropriate for the age and sex of the denture wearer. There is a need for improved training and guidance on artificial tooth selection and arrangement.

Adolescent↗
PubMed2001

A tropomyosin-2 mutation suppresses a troponin I myopathy in Drosophila.

A suppressor mutation, D53, of the held-up(2) allele of the Drosophila melanogaster Troponin I (wupA) gene is described. D53, a missense mutation, S185F, of the tropomyosin-2, Tm2, gene fully suppresses all the phenotypic effects of held-up(2), including the destructive hypercontraction of the indirect flight muscles (IFMs), a lack of jumping, the progressive myopathy of the walking muscles, and reductions in larval crawling and feeding behavior. The suppressor restores normal function of the IFMs, but flight ability decreases with age and correlates with an unusual, progressive structural collapse of the myofibrillar lattice starting at the center. The S185F substitution in Tm2 is close to a troponin T binding site on tropomyosin. Models to explain suppression by D53, derived from current knowledge of the vertebrate troponin-tropomyosin complex structure and functions, are discussed. The effects of S185F are compared with those of two mutations in residues 175 and 180 of human alpha-tropomyosin 1 which cause familial hypertrophic cardiomyopathy (HCM).

Amino Acid Sequence↗
PubMed2001

Pseudomyasthenia resulting from a posterior carotid artery wall aneurysm: a novel presentation: case report.

OBJECTIVE AND IMPORTANCE: Painful oculomotor palsy can result from enlargement or rupture of intracranial aneurysms. The IIIrd cranial nerve dysfunction in this setting, whether partial or complete, is usually fixed or progressive and is sometimes reversible with surgery. We report an unusual oculomotor manifestation of a posterior carotid artery wall aneurysm, which mimicked ocular myasthenia gravis. CLINICAL PRESENTATION: A 47-year-old woman developed painless, intermittent, partial IIIrd cranial nerve palsy. She presented with isolated episodic left-sided ptosis, which initially suggested a metabolic or neuromuscular disorder. However, digital subtraction angiography revealed a left posterior carotid artery wall aneurysm, just proximal to the origin of the posterior communicating artery. INTERVENTION: The aneurysm was successfully clipped via a pterional craniotomy. During surgery, the aneurysm was observed to be compressing the oculomotor nerve. The patient's symptoms resolved after the operation. CONCLUSION: The variability of incomplete IIIrd cranial nerve deficits can present a diagnostic challenge, and the approach for patients with isolated IIIrd cranial nerve palsies remains controversial. Although intracranial aneurysms compressing the oculomotor nerve classically produce fixed or progressive IIIrd cranial nerve palsies with pupillary involvement, anatomic variations may result in atypical presentations. With the exception of patients who present with pupil-sparing but otherwise complete IIIrd cranial nerve palsy, clinicians should always consider an intracranial aneurysm when confronted with even subtle dysfunction of the oculomotor nerve.

Angiography, Digital Subtraction↗
PubMed2001

Reline materials--handle with care? An investigation into the effect of varying the powder/liquid ratio on some properties of auto-polymerising acrylic resin materials.

INTRODUCTION: The fit of the denture base to the alveolar ridge progressively declines with alveolar ridge resorption. Once a denture becomes ill-fitting there are two main treatment options: to construct a new denture or to restore the fit of the existing denture. A denture may be relined as a laboratory procedure or at the chairside in the dental clinic. The chairside reline technique involves the direct application of auto-polymerising acrylic resin materials to the prepared denture base and the material is allowed to polymerise in the patient's mouth. The reline materials are generally supplied as a powder and a liquid. Clinicians and laboratory dental staff do not always follow manufacturers' recommended guidelines and the tendency can be simply to add varying quantities of powder and liquid until the desired consistency is achieved. This method however may have deleterious effects on the properties of the resultant material. MATERIALS AND METHOD: The aim of the study was to investigate the effect of varying the powder/liquid ratio on some properties of three auto-polymerising acrylic resin reline materials. The properties investigated were the flow characteristics in terms of the manipulation and setting time and the hardness. Four powder and liquid ratios were chosen. RESULTS AND CONCLUSIONS: For all the materials studied, a clinically useful lengthening of the manipulation time can be achieved by increasing the amount of liquid added to the powder. However, this is perhaps offset by the fact that it is associated with a corresponding increase in the setting time and resultant increase in clinical chairside time. There were significant differences in surface hardness when the powder/liquid ratio was altered.

Acrylic Resins↗
PubMed2001

Human perception of haptic information in minimal access surgery tools for use in simulation.

This paper describes research on human perception of haptic information in minimal access surgery (MAS) instruments, for use in a MAS simulator. Understanding the thresholds of human perception is important in determining which haptic information must be provided for realistic feedback and which information can be ignored without compromising the immersive quality of the simulator. Initially this research has determined the limits of perception for non-continuous change of force amplitude and frequency in a scissors-grasping position.

Computer Simulation↗
PubMed2000

Syndrome packets and health worker training improve sexually transmitted disease case management in rural South Africa: randomized controlled trial.

BACKGROUND: Sexually transmitted diseases (STD) are important co-factors in HIV transmission. We studied the impact of health worker training and STD syndrome packets (containing recommended drugs, condoms, partner notification cards and information leaflets) on the quality of STD case management in primary care clinics in rural South Africa. METHODS: A randomized controlled trial of five matched pairs of clinics compared the intervention with routine syndromic management. Outcomes were measured by simulated patients using standardized scripts, and included the proportion given recommended drugs; correctly case managed (given recommended drugs plus condoms and partner cards); adequately counselled; reporting good staff attitude; and consulted in privacy. RESULTS: At baseline, the quality of STD case management was similarly poor in both groups. Only 36 and 46% of simulated patients visiting intervention and control clinics, respectively, were given recommended drugs. After the intervention, intervention clinics provided better case management than controls: 88 versus 50% (P < 0.01) received recommended drugs; 83 versus 12% (P < 0.005) were correctly case managed; 68 versus 46% (P = 0.06) were adequately counselled; 84 versus 58% experienced good staff attitude (P = 0.07); and 92 versus 86% (P = 0.4) were consulted privately. A syndrome packet cost US$1.50; the incremental cost was US$6.80. The total intervention cost equalled 0.3% of annual district health expenditure. INTERPRETATION: A simple and affordable health service intervention achieved substantial improvements in STD case management. Although this is a critical component of STD control and can reduce HIV transmission, community-level interventions to influence health-seeking behaviour are also needed.

Adolescent↗
PubMed2000

A school and community outbreak of tuberculosis in Auckland.

AIM: To describe a school and community outbreak of tuberculosis in South Auckland in 1997/8. METHODS: Cases were diagnosed according to national guidelines at Middlemore, Green Lane and Starship Hospitals. Public health follow-up was conducted by Auckland Healthcare. RESULTS: Twelve cases were diagnosed during the outbreak. Nine cases were from the same South Auckland secondary school; six reported no association outside school. Three cases were in younger children who had close household contact with two of the school cases. Nine cases (including eight from the school) had identical Mycobacterium tuberculosis isolates on restriction fragment length polymorphism testing. No microbiological culture was obtained from the three remaining cases. Contact investigation detected five of the cases. Chemoprophylaxis was prescribed for twenty-six school students, two adult staff, and nine household contacts. CONCLUSION: This is the first published account of a tuberculosis outbreak in a New Zealand school setting for decades. Recognition of the outbreak was delayed. DNA fingerprinting played a valuable role in the investigation. The source case may have been a school student. The social impact of the outbreak and preventability with routine adolescent BCG vaccination are discussed.

Adolescent↗
PubMed2000

The molecular anatomy of dynein.

Recent molecular, genetic and functional studies have led to an unparalleled growth in our understanding of dynein and the roles played by the various polypeptides of these massive macromolecular assemblies. Dyneins are highly complex 1-2MDa complexes that function as molecular motor and move the cargo to which they are attached towards the minus-end of a microtubule. Dynein motor function is a property of the heavy chains, whereas the intermediate chains are involved in attachment to the appropriate cargo. In order for useful work to be obtained, motor and cargo-binding activities must be tightly controlled. Current data suggest that this is the role played by certain accessory light-chain proteins. The LC8 is highly conserved and found in many enzyme systems. This protein is essential in multicellular organisms. The dynein light chains Tctex1 and Tctex2 have been implicated in the non-Mendelian transmission of variant forms of mouse chromosome 17.

Animals↗
PubMed2000

Stress distribution associated with loaded ceramic onlay restorations with different designs of marginal preparation. An FEA study.

The design of marginal finish of an inlay or onlay could influence the prognosis of the restoration since this area is subjected to various mechanical or chemical actions during function. This study was carried out to determine the tensile stresses which develop at the marginal area when subjected to vertical and horizontal loads. Onlay restorations with three different types of marginal finish, i. e. shoulder, chamfer and bevel, were modelled in three dimensions using the finite element method, and were then subjected to vertical and horizontal load at three different sites. The results show that horizontal forces acting on the restoration generate the highest tensile stresses whilst the vertical forces generate high tensile stresses at the margins of the chamfer and bevel designs.

Bicuspid↗
PubMed2000

Assessment of plaque prevention on dentures using an experimental cleanser.

STATEMENT OF PROBLEM: Adequate plaque control is essential for the maintenance of a healthy oral mucosa. Denture cleansers are a popular method used by denture wearers for cleaning. The clinical effectiveness of a new cleanser in tablet form has not been tested in vivo. Methods used for the in vivo assessment of denture cleanser effectiveness are often not standardized. PURPOSE: The aims of this in vivo study were to develop a new method for assessing plaque levels on dentures by using digital imaging and to use this methodology, together with a validated visual scoring method, to evaluate plaque buildup on dentures. MATERIAL AND METHODS: Thirty-five subjects were randomized to 1 of 2 treatment groups: (1) dentures soaked in a new cleanser, or (2) dentures soaked in water. The treatment period lasted 14 days. Plaque was assessed at baseline and on days 2 and 14 by using digital image analysis and a visual scoring technique. Results were analyzed with ANOVA at the 95% confidence interval. RESULTS: The new cleanser showed a statistically significant reduction in mean visual plaque of 51% at day 2 (P = 0.0002) and 42% (P = 0.0014) at day 14 compared with water. Similar results were seen with digital imaging. CONCLUSION: The new denture cleanser proved to be effective at preventing plaque accumulation on dentures. The analysis of digital images gave similar results as the visual scoring method.

Adhesives↗