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Biomedical subjects

W Smith

Publications and source records attributed to W Smith.

At least 55 records · Page 3Linked to original sources
PubMed2001

The increasing prevalence of myopia: implications for Australia.

Myopia is often regarded as a minor priority in public health research, yet the public health costs of myopia are considerable, both due to the costs of optical correction and from the costs imposed by the morbidity resulting from myopia in terms of associated eye disease (glaucoma, posterior subcapsular cataract), and the visual impairment and blindness that can result from myopia due to myopic retinal degeneration and retinal detachment. There is clear evidence for a high and increasing prevalence of myopia in East Asia, apparently driven by increasing educational pressures and urbanization. Data from the USA, Europe and Australia are consistent with the data from Asia in terms of the role of these risk factors. However, the evidence for an increasing prevalence of myopia is more problematic, due to the lack of adequate longitudinal studies, and the confounding effects of age-related hypermetropization. It is concluded that the prevalence of myopia is probably increasing in Australia, although the changes are of much lower magnitude than n East Asia. Longitudinal studies are, therefore, clearly required to quantify changes in the prevalence of myopia in Australia, for accurate assessment of the public health impacts and to assist with the development of preventive approaches.

Adult↗
PubMed2001

Validation of self-reported hearing loss. The Blue Mountains Hearing Study.

PURPOSE: Large-scale epidemiological studies have often used self-report to estimate prevalence of age-related hearing loss. However, few large population-based studies have validated self-report against measured hearing loss. Our study aimed to assess the performance of a single question and a brief hearing handicap questionnaire in identifying individuals with hearing loss, against the gold standard of pure-tone audiometry. METHODS: We examined 2015 residents, aged 55-99 years, living in the west of Sydney, Australia, who participated in the Blue Mountains Hearing Study during 1997-1999. Audiologists administered a comprehensive questionnaire, including the question: 'Do you feel you have a hearing loss?' The Shortened Hearing Handicap Inventory for Elderly (HHIE-S) was also administered during the hearing examination, which included pure-tone audiometry. The single question and HHIE-S were compared with measured losses at levels >25, >40 and >60 decibels hearing level (dBHL) to indicate mild, moderate and marked hearing impairment, for pure-tone averages (PTA) of responses to 500, 1000, 2000 and 4000 Hz. RESULTS: The single question yielded reasonable sensitivity and specificity for hearing impairment, and was minimally affected by age and gender. HHIE-S scores >8 had lower sensitivity but higher specificity and positive predictive value. The HHIE-S performed slightly better in younger than older subjects and performed better for moderate hearing impairment. CONCLUSIONS: In this older population with a high prevalence of hearing loss (39.4%), both a question about hearing and the HHIE-S appeared sufficiently sensitive and specific to provide reasonable estimates of hearing loss prevalence. Both could be recommended for use in epidemiological studies that aim to assess the magnitude of the burden caused by age-related sensory impairment but cannot measure hearing loss by audiometry.

Aged↗
PubMed2001

Current multimodality management of infectious intracranial aneurysms.

OBJECTIVE: To implement an algorithm for and assess multimodality (medical, endovascular, and microsurgical) treatment of patients with infectious intracranial aneurysms. METHODS: Twenty patients with 27 infectious aneurysms were treated during a 10-year period. Bacterial endocarditis was the most common cause (65%). Most aneurysms presented with rupture (75%), and the middle cerebral artery was the most common location (70%). RESULTS: Five patients were treated endovascularly, with direct coiling for three patients and parent artery occlusion for two patients. Ten patients (15 aneurysms) were treated surgically, with 6 aneurysms being trapped/resected, 2 trapped/bypassed, 4 clipped, and 3 wrapped. Five patients were treated medically. Treatment-associated neurological morbidity was observed for two patients (10%), and two patients died (10%). Good outcomes were observed for 16 patients (80%). CONCLUSION: Factors that guide management decisions for these patients include aneurysm rupture, hematomas with increased intracranial pressure, and the eloquence of brain tissue supplied by the parent artery. Patients with unruptured infectious aneurysms are initially treated medically, with antibiotics and serial angiography. Patients with ruptured aneurysms that are not associated with hematomas and that do not involve eloquent vascular territory are treated endovascularly. Patients with ruptured aneurysms are treated surgically when there is a hematoma or the risk of ischemic complications in eloquent territory. Therefore, endovascular therapy is the first option for patients in stable condition with ruptured aneurysms; surgical therapy is the first option for patients in unstable condition with ruptured aneurysms and the second option for patients in stable condition who experience failure of endovascular therapy. Medically treated patients with enlarging or dynamic unruptured aneurysms also require direct surgical or endovascular intervention. Favorable patient outcomes can be achieved with this multimodality management.

Adolescent↗
PubMed2001

Exploring extra-binomial variation in teratology data using continuous mixtures.

Discrete data from animal teratology experiments are known to exhibit extra-binomial variation. For example, we discuss a dominant lethal assay experiment in which male mice are exposed to various levels of radiation and are then mated to females. The response of interest is the number of resorptions out of the number of implantations. Most statistical work on analyzing such data has focused on modeling response rates as a function of dose of a suspected teratogen (radiation in this case) while accounting for the extra-binomial variability when calculating standard errors of the regression coefficients. Sometimes, however, when an unobserved genetic or exposure variable is suspected, the shape of the mixing distribution is of interest. We propose a mixture of beta-binomials (MBB) family of distributions that includes the non-parametric mixture of binomials model of Laird (1978) as a special case. The MBB family can accommodate a mixing distribution with one or more modes, and we develop a bootstrap test for multimodality. We apply the method to data from a dominant lethal teratology experiment.

Animals↗
PubMed2001

Recording and analyzing high-density event-related potentials with infants. Using the Geodesic sensor net.

This article provides an overview of the use of the Geodesic sensor net system for high-density event-related potential (ERP) recording in infants. Some advantages and disadvantages of the system, as applied to infants, are discussed. First, we illustrate that high-density data can be recorded from infants at comparable quality to that observed with conventional (low density) ERP methods. Second, we discuss ways to utilize the greater spatial information available by applying source separation and localization procedures. In particular, we focus on the application of one recent source separation method, Independent Component Analysis (ICA). Finally, we show that source localization can be applied to infant high-density data, although this entails adopting a number of assumptions that remain to be verified. In the future, with improved source separation algorithms, we suggest that single-trial or single-subject analyses may become feasible.

Adult↗
PubMed2001

The role of meaning and familiarity in mental transformations.

Eighty-four participants mentally rotated meaningful and meaningless objects. Within each type of object, half were simple and half were complex; the complexity was the same across the meaningful and meaningless objects. The patterns of errors were examined as a function of the type of stimuli (meaningful vs. meaningless), complexity, and angle of rotation. The data for the meaningful objects showed steeper slopes of rotation for complex objects than that for simple objects. In contrast, the simple and complex meaningless objects showed comparable increases in error rates as a function of angle of rotation. Furthermore, the slopes remained comparable after pretraining that increased familiarity with the objects. The results are discussed in terms of underlying representations of meaningful and meaningless objects and their implications to mental transformations. The data are consistent with a piecemeal rotation of the meaningful stimuli and a holistic rotation of the meaningless stimuli.

Adolescent↗
PubMed2001

The distribution of plantar pressures in American Indians with diabetes mellitus.

The primary purpose of this study was to determine the magnitude and duration of plantar pressures acting on the feet of American Indians with diabetes mellitus. A secondary purpose was to determine whether differences in the range of motion of the ankle and first metatarsophalangeal joints existed between American Indians with and without diabetes. Three groups of American Indian subjects were tested: a control group (n = 20); a group with diabetes but no peripheral neuropathy (n = 24); and a group with diabetes and peripheral neuropathy (n = 21). A floor-mounted pressure sensor platform was used to collect plantar pressure data while subjects walked barefoot. The results indicated that American Indians with diabetes have 1) a pattern of peak plantar pressure similar to patterns previously reported for non-American Indians with diabetes and 2) a reduction in ankle and first metatarsophalangeal joint range of motion in comparison with nondiabetic American Indians.

Adult↗
PubMed2001

Topoisomerase I inhibitors in the treatment of head and neck cancer.

Traditionally, the role of chemotherapy in the treatment of squamous carcinoma of the head and neck has been confined to patients with recurrent or metastatic disease who are deemed incurable with surgery or radiation therapy. Over the past decade, however, the role of chemotherapy has changed dramatically. The use of primary combined chemoradiation to preserve function or to enhance survival in patients with unresectable disease has become a standard approach. As the use of chemotherapy in squamous carcinoma of the head and neck has expanded, investigators have been interested in identifying new active agents. Topoisomerase I inhibitors, a new class of drugs, have been found to be active in a number of solid and hematologic malignancies. Three topoisomerase I inhibitors have been investigated in the treatment of metastatic or recurrent squamous carcinoma of the head and neck: 9-aminocamptothecin (9-AC), topotecan (Hycamtin), and irinotecan (CPT-11, Camptosar). Neither 9-AC nor topotecan has demonstrated clinically significant activity in the treatment of metastatic or recurrent squamous carcinoma of the head and neck. In contrast, irinotecan has demonstrated a modest overall response rate of 21.2% (95% confidence interval [CI] = 9%-38.9%), with a median survival of 214 days and a 1-year survival rate of 30.2%. The response and toxicity appear to be dose dependent. Further investigation of irinotecan in combination with other active agents and radiotherapy is warranted.

Antineoplastic Agents↗
PubMed2001

Characterisation of a gene cluster involved in bacterial degradation of the cyanobacterial toxin microcystin LR.

A novel pathway for degradation of the cyanobacterial heptapeptide hepatotoxin microcystin LR was identified in a newly isolated Sphingomonas sp. (Bourne et al. 1996 Appl. Environ. Microbiol. 62: 4086-4094). We now report the cloning and molecular characterisation of four genes from this Sphingomonas sp. that exist on a 5.8-kb genomic fragment and encode the three hydrolytic enzymes involved in this pathway together with a putative oligopeptide transporter. The heterologously expressed degradation pathway proteins are enzymatically active. Microcystinase (MlrA), the first enzyme in the degradative pathway, is a 336-residue endopeptidase, which displays only low sequence identity with a hypothetical protein from Methanobacterium thermoautotrophicum. Inhibition of microcystinase by EDTA and 1,10-phenanthroline suggests that it is a metalloenzyme. The most likely residues that could potentially chelate an active-site transition metal ion are in the sequence HXXHXE, which would be unique for a metalloproteinase. Situated immediately downstream of mlrA with the same direction of transcription is a gene mlrD, whose conceptual translation (MlrD, 442 residues) shows significant sequence identity and similar potential transmembrane spanning regions to the PTR2 family of oligopeptide transporters. A gene mlrB is situated downstream of the mlrA and mlrD genes, but transcribed in the opposite direction. The gene encodes the enzyme MlrB (402 residues) which cleaves linear microcystin LR to a tetrapeptide degradation product. This enzyme belongs to the "penicillin-binding enzyme" family of active site serine hydrolases. The final gene in the cluster mlrC, is located upstream of the mlrA gene and is transcribed in the opposite direction. It codes for MlrC (507 residues) which mediates further peptidolytic degradation of the tetrapeptide. This protein shows significant sequence identity to a hypothetical protein from Streptomyces coelicolor. It is suspected to be a metallopeptidase based on inhibition by metal chelators. It is postulated on the basis of comparison with other microorganisms that the genes in this cluster may all be involved in cell wall peptidoglycan cycling and subsequently act fortuitously in hydrolysis of microcystin LR.

Amino Acid Sequence↗
PubMed2000

Acute hemodynamic and clinical effects of levosimendan in patients with severe heart failure. Study Investigators.

BACKGROUND: We determined the short-term hemodynamic and clinical effects of levosimendan, a novel calcium-sensitizing agent, in patients with decompensated heart failure. METHODS AND RESULTS: One hundred forty-six patients with New York Heart Association functional class III or IV heart failure (mean left ventricular ejection fraction 21+/-1%) who had a pulmonary capillary wedge pressure >/=15 mm Hg and a cardiac index </=2.5 L x min(-1) x m(-2) were enrolled in a multicenter, double-blind, placebo-controlled study and randomized 2:1 to intravenous infusion of levosimendan or placebo. Drug infusions were uptitrated over 4 hours from an initial infusion rate of 0.1 microg x kg(-1) x min(-1) to a maximum rate of 0.4 microg x kg(-1) x min(-1) and maintained at the maximal tolerated infusion rate for an additional 2 hours. Levosimendan caused dose-dependent increases in stroke volume and cardiac index beginning with the lowest infusion rate and achieving maximal increases in stroke volume and cardiac index of 28% and 39%, respectively. Heart rate increased modestly (8%) at the maximal infusion rate and was not increased at the 2 lowest infusion rates. Levosimendan caused dose-dependent decreases in pulmonary capillary wedge, right atrial, pulmonary arterial, and mean arterial pressures. Levosimendan appeared to improve dyspnea and fatigue, as assessed by the patient and physician, and was not associated with a significant increase in adverse events. CONCLUSIONS: Levosimendan caused rapid dose-dependent improvement in hemodynamic function in patients with decompensated heart failure. These hemodynamic effects appeared to be accompanied by symptom improvement and were not associated with a significant increase in the number of adverse events. Levosimendan may be of value in the short-term management of patients with decompensated heart failure.

Cardiotonic Agents↗
PubMed2000

Dietary sodium intake and cataract: the Blue Mountains Eye Study.

A population-based cross-sectional study (n = 2,873) was conducted near Sydney, Australia, from January 1992 to January 1994 to assess the relation between dietary sodium intake and risk of cataract. Photographs of subjects' lenses were graded for cortical, nuclear, and posterior subcapsular cataracts. Dietary sodium intake was assessed with a food frequency questionnaire. The study found that higher sodium intakes were associated with greater risk of posterior subcapsular cataract (p for trend = 0.006). The adjusted relative risk was 2.0 (95% confidence interval: 1.2, 3.4) for subjects in the highest versus the lowest quintile of sodium intake. These findings suggest that a high-salt diet may increase the risk of posterior subcapsular cataract.

Aged↗
PubMed2000

Dietary fat and fish intake and age-related maculopathy.

OBJECTIVE: To assess whether dietary intake of fat or fish is associated with age-related maculopathy (ARM) prevalence. DESIGN: Cross-sectional, urban population-based study. PARTICIPANTS: People (N = 3654) aged 49 years or older. MAIN OUTCOME MEASURES: Subjects with ARM were identified from masked grading of retinal photographs. A 145-itemself-administered, semiquantitative food frequency questionnaire was completed adequately by 88.8% of participants and was used to assess intakes of dietary fat and fish. RESULTS: A higher frequency of fish consumption was associated with decreased odds of late ARM (odds ratio for frequency of consumption more than once per week compared with less than once per month, 0.5). Subjects with higher energy-adjusted intakes of cholesterol were significantly more likely to have late ARM, with an increased risk for late ARM for the highest compared with the lowest quintile of intake (odds ratio, 2.7). CONCLUSION: The amount and type of dietary fat intake may be associated with ARM.

Aged↗
PubMed2000

Diet and cataract: the Blue Mountains Eye Study.

PURPOSE: To investigate relationships between a wide range of macro- and micronutrients, including antioxidant vitamins, and the three main types of cataract in older people. DESIGN: Population-based cross-sectional study. PARTICIPANTS: Two thousand nine hundred people aged 49 to 97 years living in an urban community near Sydney, Australia. TESTING: Food frequency questionnaires and lens photography. MAIN OUTCOME MEASURE: Lens photographs were graded for presence and severity of cortical, nuclear, and posterior subcapsular cataracts. RESULTS: Higher intakes of protein, vitamin A, niacin, thiamin, and riboflavin were associated with reduced prevalence of nuclear cataract. After adjusting for multiple known cataract risk factors, the odds ratios for those in the highest intake quintile groups compared to those in the lowest intake quintiles were 0.5 (95% confidence interval [CI], 0.3-0.8) for protein, 0.5 (95% CI, 0.3-0.9) for vitamin A, 0.6 (95% CI, 0.4-0.9) for niacin, 0.6 (95% CI, 0.4-0.9) for thiamin, and 0.5 (95% CI, 0.3-0.9) for riboflavin. Intake of polyunsaturated fats was associated with reduced prevalence of cortical cataract. No nutrients were associated with posterior subcapsular cataract. CONCLUSIONS: The nucleus of the lens is particularly sensitive to nutrient deficiencies. Protein, vitamin A, niacin, thiamin, and riboflavin protected against nuclear cataract in this study.

Aged↗
PubMed2000

Risk factors and significance of finding asymptomatic retinal emboli.

PURPOSE: To assess the prevalence rates for asymptomatic retinal emboli among both younger and older individuals, with single and multiple potential risk factors, in order to alert clinicians to the probability of finding retinal emboli in patients with varying characteristics. METHODS: In all, 3654 people aged 49-97 attending the Blue Mountains Eye Study had a detailed eye examination which included retinal photographs of the central and peripheral retinal fields. Retinal emboli were identified during masked photographic grading and definite cases were adjudicated. RESULTS: Retinal emboli were found in 51 subjects (1.4% of the population); these included 1.1% of people aged 49-69 years (middle-aged subjects) and 2.0% of people aged more than 70 years (older subjects). Risk factors identified were male sex, increasing age, hypertension, current smoking, history of any vascular event (angina, myocardial infarct, stroke) or history of vascular surgery. Among middle-aged subjects, current smoking and history of hypertension or a vascular event were significantly associated with emboli (odds ratios (OR) 2.3-3.1), while in older subjects, history of vascular surgery was related (OR 4.7). The highest prevalence of emboli (5.5%) was found in people who reported a history of hypertension and also smoked (OR 6.0). Among hypertensive men who smoked, emboli were present in 7.6%. CONCLUSIONS: This study indicates that although asymptomatic retinal emboli are relatively infrequent in the general older population, these lesions are surprisingly common in people (particularly men) with multiple risk factors. Ophthalmologists could routinely screen for emboli and consider alerting the patients' general practitioners to review vascular risk factors.

Aged↗