Biomedical subjects

S Bennett

Publications and source records attributed to S Bennett.

At least 37 records · Page 2Linked to original sources

PubMed2001

Clinical features in women with polycystic ovaries: relationships to insulin sensitivity, insulin gene VNTR and birth weight.

OBJECTIVE: Polycystic ovaries are a common ultrasound finding, yet few of these women have many clinical features of polycystic ovary syndrome. Clinical presentation may relate to degree of insulin resistance, common polymorphism at the insulin gene VNTR, and birth weight. We therefore examined the relationship between insulin sensitivity, insulin gene VNTR genotype, birth weight and presence of polycystic ovaries/features of polycystic ovary syndrome in a normal population study. DESIGN AND PATIENTS: In 224 young women recruited as normal volunteers, ovarian morphology was determined by transabdominal ultrasound and features of polycystic ovary syndrome were identified on clinical and biochemical examination. Insulin sensitivity was estimated from fasting glucose and insulin levels using the homeostasis model. Insulin gene VNTR genotypes were determined in women and their parents. MEASUREMENTS AND RESULTS: Thirty-three per cent (74/224) had polycystic ovaries on ultrasound. These women had higher birth weights (P = 0.004), higher insulin sensitivity (P = 0.02) and higher leptin levels for body mass index (P = 0.04) than women with normal ovaries. However among women with polycystic ovaries, increasing severity of clinical phenotype (based on number of features of: menstrual irregularity, acne, hirsutism, serum testosterone > 3 mmol/l and LH > 10 IU/l) was associated with decreasing insulin sensitivity (P < 0.0001) and related to paternally transmitted insulin gene VNTR class III alleles (P = 0.03). CONCLUSION: Women with polycystic ovaries on ultrasound have increased insulin sensitivity and possible leptin resistance, which could predispose to future weight gain. However, in these women the appearance of clinical features of polycystic ovary syndrome is related to insulin resistance and insulin gene VNTR class III alleles.

Adolescent↗

PubMed2001

Traumatic renal artery dissection identified with dynamic helical computed tomography.

Intimal tears in the renal arteries typically result from traumatic mechanisms that produce rapid deceleration. These injuries usually progress to secondary thrombosis of the vessel. When the tear leads to dissection with luminal stenosis, early diagnosis and repair will preserve parenchymal function. Computed tomography has replaced intravenous pyelography as the radiographic study of choice for renal trauma. We present two patients with unilateral delay of renal contrast enhancement during dynamic helical computed tomography scan due to arterial stenosis from intimal dissection confirmed with arteriography. Both vessel injuries were successfully managed with endovascular stent placement. No previous description of this diagnostic strategy is reported in the literature.

Adult↗

PubMed2001

Expression of multiple forms of clusterin during light-induced retinal degeneration.

PURPOSE: Clusterin has been associated with active cell death in several different model systems, including animal models of retinal degeneration. Clusterin is also expressed in normal tissues, a finding that leads to the question of how it could then play a cell death-specific role during tissue regression. To address this paradox, we have examined clusterin expression during light-induced retinal damage in rats. METHODS: Normal albino rats were reared in darkness and then exposed to intense visible light to induce retinal degeneration. Clusterin expression was then examined at various times after light treatment. Standard molecular techniques including Northern analysis, immunohistochemistry, and Western analysis were employed. RESULTS: Northern analysis established that the largest increase in clusterin expression occurs after a decrease in interphotoreceptor retinoid binding protein, IRBP, expression (an indication of a photoreceptor cell dysfunction) and after an increase in heme oxygenase 1, HO-1, expression (an oxidative stress inducible gene), suggesting that induction of clusterin expression is an oxidative stress response. Immuno-histochemical analysis with two different clusterin-specific antibodies, anti(SGP-2) and anti(301), localized distinct forms of clusterin to Müller cells and degenerating photo-receptor cells. Western analysis demonstrated degeneration associated isoforms of clusterin in light treated retina that are not present in normal retina. CONCLUSION: Clusterin over-expression is characteristic of a retinal degeneration phenotype and we propose that clusterin action may be defined by the nature in which it is modified. We hypothesize that alternate processing leads to retinal degeneration-specific forms of the protein (65, 61, and 50 kDa) that are not present in normal retina.

Animals↗

PubMed2001

Grasping a better understanding of the intrinsic dynamics of rhythmical and discrete prehension.

In this study, the authors examined the influence of the intrinsic dynamics of discrete and rhythmical prehension. Six adults underwent a scaling procedure in which the movement time was systematically increased so that it corresponded with 6 frequencies: 0.5, 0.75, 1.0, 1.25, 1.5, and 1.75 Hz. In posttests, participants moved at their own preferred pace. No differences were found in the relative time to final hand closure (T[rfc]) between the rhythmical and discrete conditions. The variability of T[rfc] was shown to be less at the preferred step of scaling than during the posttest. With the scaling technique, one can guide participants into more stable movement patterns than they can achieve when the metronome is not present, because, when the metronome is present, their movements become anchored to the external pacing cue. Those findings provide support for the use of a scaling technique to identify the influence of the intrinsic dynamics during rhythmical and discrete movements.

Adult↗

PubMed2001

Information--movement coupling: implications for the organization of research and practice during acquisition of self-paced extrinsic timing skills.

Information--movement coupling is a fundamental concept, integral to theorizing on the coordination of goal-directed activity in ecological psychology. In this paper, we examine the implications of this concept for the design of experimental research and the organization of practice during the acquisition of movement coordination in sport tasks. The task vehicle for our analysis is interceptive actions, in particular self-paced extrinsic timing tasks exemplified by serving in sports such as volleyball. Recent research highlighting the relevance of information--movement coupling for the process of practice in sport is discussed. We conclude that information--movement coupling represents an important principle for the structural organization of research and practice in self-paced extrinsic timing tasks and that further work is required to verify its significance across a range of sport movements.

Female↗

PubMed2001

Research design and statistics in biomechanics and motor control.

Biomechanics and motor control researchers measure how the body moves and interacts with its environment. The aim of this review paper is to consider some key issues in research methods in biomechanics and motor control. The review is organized into four sections: proposing, conducting, analysing and reporting research. In the first of these, we emphasize the importance of defining a worthy research question and of planning the study before its implementation to prevent later difficulties in the analysis and interpretation of data. In the second section, we cover selection of trial sizes and suggest that using three trials or more may be beneficial to provide more 'representative' and valid data. The third section on analysis of data concentrates on effect size statistics, qualitative and numerical trend analysis and cross-correlations. As sample sizes are often small, the use of effect size is recommended to support the results of statistical significance testing. In using cross-correlations, we recommend that scatterplots of one variable against the other, with the identified time lag included, be inspected to confirm that the linear relationship assumption underpinning this statistic is met and, if appropriate, that a linearity transformation be applied. Finally, we consider important information related to the issues above that should be included when reporting research. We recommend reporting checks or corrections for violations of underpinning assumptions, and the effect of these checks or corrections, to assist in advancing knowledge in biomechanics and motor control.

Analysis of Variance↗

PubMed2001

Distribution of the mylohyoid nerve: anatomical variability and clinical implications.

The mylohyoid nerve is a branch of the mandibular division of the trigeminal nerve that provides motor supply to the mylohyoid and digastric muscles. Accessory innervation to the pulps of both anterior and posterior mandibular teeth by the sensory component of this nerve has been proposed to be one possible anatomical variation leading to failure of an inferior alveolar nerve block. The aim of this study was to trace the path of the mylohyoid nerve, from its origin in the infratemporal region to its terminal branches, in six human cadavers. Dissections of sagittally-sectioned heads were performed using both medial and submandibular approaches. The anatomy of the mylohyoid nerve was variable in terms of its level of branching, course through the mylohyoid groove or canal, branch numbers to the mylohyoid and digastric muscles, and terminal branching in the submental region. In all cases the mylohyoid nerve was seen to pass down the medial surface of the ramus behind the sphenomandibular ligament.

Aged↗

PubMed2001

Genetic regulation of acquired immune responses to antigens of Mycobacterium tuberculosis: a study of twins in West Africa.

The role of genetic factors in clinical tuberculosis is increasingly recognized; how such factors regulate the immune response to Mycobacterium tuberculosis in healthy individuals is unclear. In this study of 255 adult twin pairs residing in The Gambia, West Africa, it is apparent that memory T-cell responses to secreted mycobacterial antigens (85-kDa antigen complex, "short-term culture filtrate," and peptides from the ESAT-6 protein), as well as to the 65-kDa heat shock protein, are subject to effective genetic regulation. The delayed hypersensitivity response to intradermal tuberculin also demonstrates significant genetic variance, while quantitative T-cell and antibody responses to the 38-kDa cell membrane protein appear to be determined largely by environmental factors. Such findings have implications for vaccine development.

Adolescent↗

PubMed2001

Maximal expression of membrane-bound nitrate reductase in Paracoccus is induced by nitrate via a third FNR-like regulator named NarR.

Respiratory reduction of nitrate to nitrite is the first key step in the denitrification process that leads to nitrate loss from soils. In Paracoccus pantotrophus, the enzyme system that catalyzes this reaction is encoded by the narKGHJI gene cluster. Expression of this cluster is maximal under anaerobic conditions in the presence of nitrate. Upstream from narK is narR, a gene encoding a member of the FNR family of transcriptional activators. narR is transcribed divergently from the other nar genes. Mutational analysis reveals that NarR is required for maximal expression of the membrane-bound nitrate reductase genes and narK but has no other regulatory function related to denitrification. NarR is shown to require nitrate and/or nitrite is order to activate gene expression. The N-terminal region of the protein lacks the cysteine residues that are required for formation of an oxygen-sensitive iron-sulfur cluster in some other members of the FNR family. Also, NarR lacks a crucial residue involved in interactions of this family of regulators with the sigma(70) subunit of RNA polymerase, indicating that a different mechanism is used to promote transcription. narR is also found in Paracoccus denitrificans, indicating that this species contains at least three FNR homologues.

Amino Acid Sequence↗

PubMed2001

Homeless women and children's access to health care: a paradox.

Homeless women and children who reside in shelters experience many health-related problems. The aim of the qualitative study reported here was to (a) explore how shelter staffs manage health problems among their residents and assist them in accessing health services, and (b) identify clinical strategies for community health nurses working with this population. Findings demonstrate a paradox whereby homeless shelter staffs try to gain access to care for their residents through a system that is designed to keep them out. In addition, findings indicate a need for increased community health nursing services in homeless shelters. Strategies for resolving this paradox include providing assessment, policy development, and assurance of health care for homeless women and children.

Adult↗

PubMed2001

The effects of induced hypogonadism on arterial stiffness, body composition, and metabolic parameters in males with prostate cancer.

Sex hormones appear to play a pivotal role in determining cardiovascular risk. Androgen deprivation therapy for males with prostate cancer results in a hypogonadal state that may have important, but as yet undetermined, effects on the vasculature. We studied the effects of androgen deprivation therapy on large artery stiffness in 22 prostate cancer patients (mean age, 67 +/- 8 yr) over a 6-month period. Arterial stiffness was assessed using pulse-wave analysis, a technique that measures peripheral arterial pressure waveforms and generates corresponding central aortic waveforms. This allows determination of the augmentation of central pressure resulting from wave reflection and the augmentation index, a measure of large artery stiffness. Body compositional changes were assessed using bioelectrical impedance analysis. Fasting lipids, glucose, insulin, testosterone, and estradiol were measured. After a 3-month treatment period, the augmentation index increased from 24 +/- 6% (mean +/- SD) at baseline to 29 +/- 9% (P = 0.003) despite no change in peripheral blood pressure. Timing of wave reflection was reduced from 137 +/- 7 to 129 +/- 10 msec (P = 0.003). Fat mass increased from 20.2 +/- 9.4 to 21.9 +/- 9.6 kg (P = 0.008), whereas lean body mass decreased from 63.2 +/- 6.8 to 61.5 +/- 6.0 kg (P = 0.016). There were no changes in lipids or glucose during treatment. Median serum insulin rose from 11.8 (range, 5.6-49.1) to 15.1 (range, 7.3-83.2) mU/liter at 1 month (P = 0.021) and to 19.3 (range, 0-85.0 mU/liter by 3 months (P = 0.020). There was a correlation between the changes in fat mass and insulin concentration over the 3-month period (r = 0.56; P = 0.013). In a subgroup of patients whose treatment was discontinued after 3 months, the augmentation index decreased from 31 +/- 7% at 3 months to 29 +/- 5% by 6 months, in contrast to patients receiving continuing treatment in whom the augmentation index remained elevated at 6 months compared with baseline (P = 0.043). These data indicate that induced hypogonadism in males with prostate cancer results in a rise in the augmentation of central arterial pressure, suggesting large artery stiffening. Adverse body compositional changes associated with rising insulin concentrations suggest reduced insulin sensitivity. These adverse hemodynamic and metabolic effects may increase cardiovascular risk in this patient group.

Adipose Tissue↗

PubMed2000

Antibacterial mesh sling: a prospective outcome analysis.

OBJECTIVES: To prospectively assess the outcome results of the Gore-Tex antibacterial mesh sling in women with pelvic prolapse and stress incontinence. METHODS: Between July 1997 and November 1998, 30 women with stress incontinence and vaginal prolapse underwent vaginal reconstruction with the antibacterial mesh sling. All patients had documented stress incontinence by preoperative urodynamic evaluation. Postoperatively, we conducted an outcome analysis on the basis of the results from a self-reported satisfaction questionnaire, a detailed pelvic examination, a cough stress test, and the Q-tip test. Urodynamic studies were performed on patients with persistent stress incontinence or urge symptoms. Cystoscopy was performed on patients suspected of having urethral erosion. RESULTS: Complete follow-up was available for all 30 patients. Of the group, 12 (40.0%) of 30 underwent implantation of the antibacterial mesh sling alone and 18 (60.0%) underwent additional prolapse repair. The mean follow-up was 18 months (range 9 to 24); mean age was 58 years (range 29 to 87). Stress incontinence was cured in 28 (93.3%) of 30 patients. De novo urge incontinence developed in 1 (5.2%) of 18 patients; urge symptoms persisted in 5 (41.7%) of 12 patients. The postoperative mean Valsalva Q-tip angle was 15 degrees (range 0 degrees to 25 degrees ). The incidence of urethral obstruction and erosion was zero. The mean postoperative pain score was 3 of 10 (range 0 to 6), and the mean satisfaction score was 9 of 10 (range 7 to 10). The mean time to discharge was 21 hours (range 6 to 29). All 30 women (100%) were willing to undergo surgery again. CONCLUSIONS: The safety profile of the Gore-Tex antibacterial mesh is better than that of the conventional Gore-Tex sling. When meticulous surgical technique is used, excellent short-term results can be achieved in the correction of female stress incontinence.

Adult↗

PubMed2000

The response of providers to capitation payment: a case-study from Thailand.

Those designing payment systems for health care in low and middle income countries are increasingly looking to capitation payment, in order to avoid the cost inflation experienced with fee-for-service payment. However, there is virtually no documentation of the experience of introducing capitation payment, or of its effects. This paper draws on several research studies to explore responses by health care providers at both the market and facility level to the introduction of capitation payment, in the context of a new compulsory insurance scheme for workers in Thailand. The paper ends by identifying lessons for both Thailand itself and for other countries.

Capitation Fee↗

PubMed2000

Synthesis and evaluation of C-9 modified N-acetylneuraminic acid derivatives as substrates for N-acetylneuraminic acid aldolase.

Several C-9 modified N-acetylneuraminic acid derivatives have been synthesised and evaluated as substrates of N-acetylneuraminic acid aldolase. Simple C-9 acyl or ether modified derivatives of N-acetylneuraminic acid were found to be accepted as substrates by the enzyme, albeit being transformed more slowly than Neu5Ac itself. 1H NMR spectroscopy was used to evaluate the extent of the enzyme catalysed transformation of these compounds. Interestingly, the chain-extended Neu5Ac derivative 16 is not a substrate for N-acetylneuraminate lyase and behaves as an inhibitor of the enzyme.

Bacterial Proteins↗

PubMed2000

Implicit learning differences: a question of developmental level?

A. S. Reber's (1992) proposition that the implicit learning system should demonstrate invariance of intellectual level (IQ) was examined by comparing 20 children with intellectual disability (mean mental age [MA] = approximately 5.8 years) with 20 intellectually gifted children (mean MA = approximately 12.4 years) of similar chronological age (CA; approximately 9.5 years). Implicit learning was assessed using a task involving covariation of 2 incidental cues. Explicit learning was assessed using a task of similar logical structure. Contrary to the IQ-invariance proposition, implicit learning as well as explicit learning varied with intellectual level. A secondary aim was to distinguish the contributions of CA, IQ, and MA to implicit learning. This was done by combining the samples of children in the present study with 2 samples of younger and older children of average ability from a study by M. Maybery, M. Taylor, and A. O'Brien-Malone (1995). Analyses showed that MA is critical to implicit learning.

Association Learning↗

PubMed2000

The effects of growth hormone and IGF-1 deficiency on cerebrovascular and brain ageing.

Research studies clearly indicate that age-related changes in cellular and tissue function are linked to decreases in the anabolic hormones, growth hormone and insulin-like growth factor (IGF)-1. Although there has been extensive research on the effects of these hormones on bone and muscle mass, their effect on cerebrovascular and brain ageing has received little attention. We have also observed that in response to moderate calorie restriction (a treatment that increases mean and maximal lifespan by 30-40%), age-related decreases in growth hormone secretion are ameliorated (despite a decline in plasma levels of IGF-1) suggesting that some of the effects of calorie restriction are mediated by modifying the regulation of the growth hormone/IGF-1 axis. Recently, we have observed that microvascular density on the surface of the brain decreases with age and that these vascular changes are ameliorated by moderate calorie restriction. Analysis of cerebral blood flow paralleled the changes in vasculature in both groups. Administration of growth hormone for 28 d was also found to increase microvascular density in aged animals and further analysis indicated that the cerebral vasculature is an important paracrine source of IGF-1 for the brain. In subsequent studies, administration of GHRH (to increase endogenous release of growth hormone) or direct administration of IGF-I was shown to reverse the age-related decline in spatial working and reference memory. Similarly, antagonism of IGF-1 action in the brains of young animals impaired both learning and reference memory. Investigation of the mechanisms of action of IGF-1 suggested that this hormone regulates age-related alterations in NMDA receptor subtypes (e.g. NMDAR2A and R2B). The beneficial role of growth hormone and IGF-1 in ameliorating vascular and brain ageing are counterbalanced by their well-recognised roles in age-related pathogenesis. Although research in this area is still evolving, our results suggest that decreases in growth hormone and IGF-1 with age have both beneficial and deleterious effects. Furthermore, part of the actions of moderate calorie restriction on tissue function and lifespan may be mediated through alterations in the growth hormone/IGF-1 axis.

Aging↗

PubMed2000

Effects of cricket ball colour and illuminance levels on catching behaviour in professional cricketers.

In recent years there have been many alterations to equipment and technology in professional cricket, including the introduction of white balls during day-night matches. In the present study simulated slip-catching performance and movement initiation time were examined in professional cricketers when ball colour and illuminance levels differed. Five male professional cricketers (mean age: 27.3 +/- 1.4 years) volunteered to catch a total of 60 cricket balls, 20 (10 red and 10 white) under each of three illuminance levels (571, 1143 and 1714 lux). Balls were projected from a ball machine at 20 m s(-1) (45 mph) over a distance of 8.4 m, to the subject's dominant side. Catching performance was measured using an established catching scale. Movement initiation times for each hand were also calculated for each trial using a motion-analysis system. Data were submitted to separate two-way (ball colour [2] x illuminance level [3]) repeated measures analysis of variance. No significant effects were obtained for ball colour or illuminance levels for either catching performance or movement initiation time. Neither ball colour nor light level (within the range tested) affected slip-catching performance and movement initiation times in professional cricketers. Therefore it was concluded that the changes made to ball colour and light conditions in professional cricket were not detrimental to catching performance.

Adult↗

PubMed2000

Theory and practice in sport psychology and motor behaviour needs to be constrained by integrative modelling of brain and behaviour.

Because of advances in technology, the non-invasive study of the human brain has enhanced the knowledge base within the neurosciences, resulting in an increased impact on the psychological study of human behaviour. We argue that application of this knowledge base should be considered in theoretical modelling within sport psychology and motor behaviour alongside existing ideas. We propose that interventions founded on current theoretical and empirical understanding in both psychology and the neurosciences may ultimately lead to greater benefits for athletes during practice and performance. As vehicles for exploring the arguments of a greater integration of psychology and neurosciences research, imagery and perception-action within the sport psychology and motor behaviour domains will serve as exemplars. Current neuroscience evidence will be discussed in relation to theoretical developments; the implications for sport scientists will be considered.

Behavior↗