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Biomedical subjects

W Smith

Publications and source records attributed to W Smith.

At least 145 records · Page 8Linked to original sources
PubMed1997

Gender, oestrogen, hormone replacement and age-related macular degeneration: results from the Blue Mountains Eye Study.

PURPOSE: To determine whether females have a higher age-specific age-related maculopathy prevalence than males; whether there is an increased risk of age-related macular degeneration (AMD) with early menopause; and whether there is a decreased risk of AMD with use of hormone replacement therapy (HRT). METHODS: Pooled data from three study populations that have used similar AMD diagnostic criteria were used to answer the first hypothesis: the Beaver Dam Eye Study (BDES), the Rotterdam study of the elderly, and the Blue Mountains Eye Study (BMES). The BMES population was used to answer the second and third hypotheses. This population included residents aged 49 or older with 2072 women participating, of whom 1899 postmenopausal women answered questions about menopause, menarche and HRT. AMD was diagnosed from graded retinal photographs using modified international criteria. RESULTS: The overall pooled odds ratio (OR) for association between sex and AMD revealed a significant increase in AMD prevalence among females compared with males, adjusting for 10-year age categories, OR = 1.15 (1.10-1.21), with no significant heterogeneity between studies. A significant decrease in the odds of early AMD with increasing years from menarche to menopause was observed. CONCLUSIONS: The results suggest that females may have a higher risk of AMD. The significant decrease in early AMD with increasing years from menarche to menopause supports the concept that a shorter duration of oestrogen production may increase risk of AMD.

Aged↗
PubMed1997

Relationship between cup-disc ratio and optic disc diameter: the Blue Mountains Eye Study.

PURPOSE: To determine the effects of optic disc size on vertical cup-disc ratio in subjects free of glaucoma and other optic nerve disease. METHODS: Data were collected from 3654 people, 49 years of age of older, living in the Blue Mountains, west of Sydney (NSW, Australia). Examinations performed included subjective refraction and Zeiss colour stereo optic disc photographs. Eye and camera magnification effects were corrected. RESULTS: Mean vertical disc diameter was 1.51 mm (95% confidence interval (CI) 1.504-1.516 mm) and the mean vertical cup-disc ratio was 0.43 (95% CI 0.425-0.435). Both parameters were distributed unimodally. The cup-disc ratio was strongly associated with disc diameter. Controlling for other variables, cup-disc ratio increased 0.270 (95% CI 0.250-0.290) per mm increase in disc diameter. CONCLUSIONS: Vertical optic disc diameter and cup-disc ratio are distributed near normally in older Australians. Optic discs with larger vertical diameters have considerably greater vertical cup-disc ratios.

Anthropometry↗
PubMed1997

Selection bias from sampling frames: telephone directory and electoral roll compared with door-to-door population census: results from the Blue Mountains Eye Study.

Many Australian public health research studies use the telephone directory or the electoral roll as a sampling frame from which to draw study subjects. The sociodemographic, disease-state and risk-factor characteristics of subjects who could be recruited using only the telephone directory or only the electoral roll sampling frames were compared with the characteristics of subjects who would have been missed using only these sampling frames, respectively. In the first phase of the Blue Mountains Eye Study we interviewed and examined 2557 people aged 49 and over living in a defined postcode area, recruited from a door-to-door census. This represented a participation rate of 80.9 per cent and a response rate of 87.9 per cent. The telephone directory was searched for each subject's telephone number and the electoral roll was searched for each subject. Subject characteristics for those who were present in each of these sampling frames were compared with the characteristics of those subjects not included in the sampling frames. The telephone directory listed 2102 (82.2 per cent) of the subjects, and 115 (4.5 per cent) had no telephone connected. The electoral roll contained 2156 (84.3 per cent) of the subjects, and 141 subjects (5.5 per cent) could not be found in either the electoral roll or the telephone directory. Younger subjects, subjects who did not own their own homes and subjects born outside of Australia were significantly less likely to be included in either of these sampling frames. The telephone directory was also more likely to exclude subjects with higher occupational prestige, while the electoral roll was more likely to exclude unmarried persons and males. Researchers using the telephone directory and electoral roll to select subjects for study should be aware of the potential selection bias these sampling frames incur and need to take care when generalising their findings to the wider community.

Aged↗
PubMed1997

Prevalence of asymptomatic retinal emboli in an Australian urban community.

BACKGROUND AND PURPOSE: Because no population-based estimates are available for asymptomatic retinal emboli, we aimed to assess prevalence and associations of this sign in a defined older Australian urban population. METHODS: A total of 3654 persons aged 49 years or older, representing 82% of residents in an urban area west of Sydney, underwent a detailed eye examination that included medical history, stereo retinal photography, and fasting blood tests including lipids. Retinal emboli were diagnosed clinically and from photographic grading and classified as cholesterol, platelet-fibrin, or calcific in type. RESULTS: Asymptomatic retinal emboli were found in 51 participants (1.4%; 95% confidence interval [CI], 1.0% to 1.8%). The prevalence was 0.8% in persons aged < 60 years, 1.4% for those aged 60 to 69 years, 2.1% for those aged 70 to 79 years, and 1.5% for those aged 80 years or older. Men had a significantly higher prevalence (2.2%) of retinal emboli than women (0.8%, P < .001) after adjustment for age (odds ratio [OR], 2.7; 95% CI, 1.5 to 4.8). Forty-one emboli (80%) were cholesterol type, 7 (14%) were platelet-fibrin, and 3 (6%) were calcific. Significant associations were found after age-sex adjustment, with hypertension (OR, 2.2; 95% CI, 1.2 to 3.8), a combined history of vascular disease (OR, 2.4; 95% CI, 1.3 to 4.4), past vascular surgery (OR, 3.5; 95% CI, 1.4 to 8.5), and current (OR, 2.2; 95% CI, 1.1 to 4.2) or any (OR, 2.6; 95% CI, 1.2 to 4.3), smoking history. These associations persisted after multivariate analysis. There were no significant associations with diabetes, obesity, or fasting blood test findings. CONCLUSIONS: This study provides accurate prevalence rates for asymptomatic retinal emboli in the elderly and confirms associations with hypertension, smoking, and vascular disease.

Age Factors↗
PubMed1997

Behavioural and cardiovascular responses of rats to euthanasia using carbon dioxide gas.

Our results showed more rapid falls in pulse rate and blood pressure in rats euthanized in a chamber precharged with carbon dioxide (CO2), when compared with rats euthanized more slowly, but death still took over 5 min in the former group. There was no behavioural evidence of pain or distress in either group during euthanasia. Initial ataxia and dyspnoea was punctuated by a lag before death, thus separating euthanasia into three clearly defined phases. All visual signs of death preceded complete vascular collapse by about 1 min in both groups, so we recommend that gas flow be maintained for at least 1 min after apparent death.

Administration, Inhalation↗
PubMed1997

Intravascular stent and endovascular coil placement for a ruptured fusiform aneurysm of the basilar artery. Case report and review of the literature.

The authors demonstrate the technical feasibility of using intravascular stents in conjunction with electrolytically detachable coils (Guglielmi detachable coils [GDCs]) for treatment of fusiform, broad-based, acutely ruptured intracranial aneurysms and review the literature on endovascular approaches to ruptured aneurysms and cerebral stent placement. A 77-year-old man presented with an acute subarachnoid hemorrhage of the posterior fossa. A fusiform aneurysm with a broad-based neck measuring 12 mm and involving the distal vertebral artery (VA) and proximal third of the basilar artery (BA) was demonstrated on cerebral angiography. The aneurysm was judged to be inoperable. Six days later a repeated hemorrhage occurred. A 15-mm-long intravascular stent was placed across the base of the aneurysm in the BA and expanded to 4 mm to act as a bridging scaffold to create a neck. A microcatheter was then guided through the interstices of the stent into the body and dome of the aneurysm, and GDCs were deposited for occlusion. The arteriogram obtained after stent placement demonstrated occlusion of the main dome and body of the aneurysm. The coils were stably positioned and held in place by the stent across the distal VA and BA fusiform aneurysm. Excellent blood flow to the distal BA and posterior cerebral artery was maintained through the stent. There were no new brainstem ischemic events attributable to the procedure. No rebleeding from the aneurysm had occurred by the 10.5-month follow-up evaluation, and the patient has experienced significant neurological improvement. Certain types of intracranial fusiform aneurysms may now be treated by combining intravascular stent and GDC placement for aneurysm occlusion via an endovascular approach. This is the first known clinical application of this novel approach in a ruptured cerebral aneurysm.

Acute Disease↗
PubMed1997

The influence of age and intraocular pressure on the optic cup in a normal population.

PURPOSE: To determine the effects of age and intraocular pressure (IOP) on optic cup and neural rim size, and cup-disc ratio in a well defined population free from apparent glaucoma and other optic nerve disease. METHODS: Data were collected on 3654 people, 49 years or older, living in the Blue Mountains, west of Sydney. Examination included subjective refraction and Zeiss colour stereo (Carl Zeiss, Oberkochen, Germany) optic disc photographs. Magnification effects of the eye and camera were corrected. After excluding subjects with optic nerve diseases, data from 6579 normal phakic eyes of 3358 subject (91.9% of those examined) were used. RESULTS: Adjusted for optic disc size and IOP, cup diameter increased 0.01 mm, cup-disc ratio increased 0.01, and neural rim width decreased 0.01 mm for every decade of age increase. Adjusted for age and optic disc size, cup diameter increased 0.01 mm, cup-disc ratio increased 0.04, and neural rim width decreased 0.07 mm for every 10 mmHg increase in IOP. The IOP-related increase in cup-disc ratio amounted to 9.5% of the mean per 10 mmHg, while the age related increase was 1.9% of the mean. CONCLUSIONS: These data support the hypothesis that there is an age-related loss of tissue from the neuroretinal rim. However the mean change between the ages of 50 and 90 years is very small. The association between increasing IOP and smaller neural rim width could suggest a causal relationship. However, it is also plausible that IOP and optic cup size are both determined by other unmeasured factors.

Aged↗
PubMed1996

Tetanus immunity in an older Australian population.

OBJECTIVE: To evaluate the effectiveness in older Australians of the current tetanus vaccination program. DESIGN: A cross-sectional survey of tetanus immunity (enzyme immunoassay of serum samples) in an older population in New South Wales. Self-reported history of tetanus vaccination was compared with serologically measured immunity. PARTICIPANTS: 430 randomly selected adults, 49 years of age and older, from the Blue Mountains Eye Study population. RESULTS: Fifty-two per cent (95% confidence interval [CI], 47%-57%) of adults 49 years of age and older had protective levels of tetanus antitoxin ( > 0.15 IU/mL). There was a significant decline in the prevalence of immunity with increasing age (chi 2 for linear trend, P = 0.036), and women were less likely to be immune regardless of their age (Mantel-Haenszel weighted odds ratio, 0.65; CI, 0.43-0.92). Thirty-five per cent (95% CI, 31%-40%) of all participants reported that they had been vaccinated in the preceding 10 years. Although self-reported tetanus vaccination history was associated with tetanus immunity, it was neither sensitive nor specific as a test for immunity. CONCLUSIONS: About half the adults 49 years of age and older in the Blue Mountains area of New South Wales do not have protective levels of tetanus antitoxin because of inadequate vaccination coverage in this age group. Vaccination history is not a reliable indicator of tetanus immunity and a system is needed for accurate recording of adult vaccination.

Adult↗
PubMed1996

Prevalence and associations of retinal vein occlusion in Australia. The Blue Mountains Eye Study.

OBJECTIVE: To determine the prevalence and associations of retinal vein occlusion (RVO) in a defined older Australian population. DESIGN: Participants (N = 3654; age, > or = 49 years), representing 88% of the permanent residents from an area west of Sydney, Australia, underwent a detailed eye examination, including stereophotography (Zeiss). The diagnosis of RVO was made clinically and from photographic grading. RESULTS: Signs of RVO were found in 59 participants (1.6%; 95% confidence interval, 1.3-1.9). The prevalence for each age-specific participant was as follows: 0.7%, younger than 60 years; 1.2%, 60 to 69 years; 2.1%, 70 to 79 years; and 4.6%, 80 years or older. There was no significant sex difference in prevalence. Branch RVO was observed in 41 subjects (69.5%); of this number, 10 subjects had branch RVO outside the vascular arcade or in the nasal fundus and 3 subjects developed new vessels. Hemispheric RVO was found in 3 subjects (5.1%), and central RVO was observed in 15 (25%); RVO was bilateral in 3 subjects (5.1%). Visual acuity was affected most in the people with central RVO, with a visual acuity of 20/200 or less in 60% compared with 14% among the people with branch RVO. Retinal vein occlusion was the fifth most frequent cause of unilateral blindness in this population. Significant associations with RVO were found with glaucoma, hypertension, stroke, and angina. CONCLUSIONS: This study emphasizes RVO as an important cause of unilateral visual loss in an older population. The proportion of the 3 vein occlusion sites shows some differences from those of clinic-based reports and suggests a likely selection bias in previous clinic studies.

Aged↗
PubMed1996

Smoking and age-related maculopathy. The Blue Mountains Eye Study.

OBJECTIVE: To assess the associations between stage of age-related maculopathy (ARM) and current, past, and passive smoking. METHODS: A cross-sectional study of 3654 subjects from a defined geographic area west of Sydney, Australia, identified subjects with late age-related macular degeneration (AMD) and early ARM by ocular examination and detailed grading of retinal photographs. Interviewer-administered questionnaires provided data about smoking history for subjects and spouses. Logistic regression, adjusting for age and sex, and 2-way analysis of variance were used to assess associations. RESULTS: Current tobacco smoking was significantly associated with late AMD (odds ratio [OR], 3.92), including neovascular AMD (OR, 3.20) and geographic atrophy (OR, 4.54), and early ARM (OR, 1.75). Having ever smoked was significantly associated with late AMD (OR, 1.83) but not early ARM. Passive smoking was associated with increased but insignificant odds for late AMD. The risk was slightly higher among women compared with men for most exposure categories. CONCLUSIONS: These findings provide convincing evidence that smoking may be causally associated with ARM. The strongest risk was found for current smokers, suggesting potential benefits of targeting education to older people who are current smokers and have signs of early ARM.

Aged↗
PubMed1996

Distribution of alpha 1A, alpha 1B and alpha 1E voltage-dependent calcium channel subunits in the human hippocampus and parahippocampal gyrus.

The distribution of voltage-dependent calcium channel subunits in the central nervous system may provide information about the function of these channels. The present study examined the distribution of three alpha-1 subunits, alpha 1A, alpha 1B and alpha 1E, in the normal human hippocampal formation and parahippocampal gyrus using the techniques of in situ hybridization and immunocytochemistry. All three subunit mRNAs appeared to be similarly localized, with high levels of expression in the dentate granule and CA pyramidal layer. At the protein level, alpha 1A, alpha 1B and alpha 1E subunits were differentially localized. In general, alpha 1A-immunoreactivity was most intense in cell bodies and dendritic processes, including dentate granule cells, CA3 pyramidal cells and entorhinal cortex pre-alpha and pri-alpha cells. The alpha 1B antibody exhibited relatively weak staining of cell bodies but stronger staining of neuropil, especially in certain regions of high synaptic density such as the polymorphic layer of the dentate gyrus and the stratum lucidum and radiatum of the CA regions. The alpha 1E staining pattern shared features in common with both alpha 1A and alpha 1B, with strong immunoreactivity in dentate granule, CA3 pyramidal and entorhinal cortex pri-alpha cells, as well as staining of the CA3 stratum lucidum. These findings suggest regions in which particular subunits may be involved in synaptic communication. For example, comparison of alpha 1B and alpha 1E staining in the CA3 stratum lucidum with calbindin-immuno-reactivity suggested that these two calcium channels subunits may be localized presynaptically in mossy fibre terminals and therefore may be involved in neurotransmitter release from these terminals.

Aged↗
PubMed1996

Alcohol intake and age-related maculopathy.

PURPOSE: To assess associations between alcohol intake and age-related maculopathy. METHODS: A population-based study of 3,654 subjects identified cases of late age-related macular degeneration, early age-related maculopathy, and any large drusen (larger than 125 microns) by examination and grading of retinal photographs. Interviewer-administered questionnaires provided data on alcohol intake. RESULTS: Neither total alcohol intake nor intake of beer specifically was significantly associated with age-related maculopathy, although a significant positive association was found between consumption of spirits and early age-related maculopathy. CONCLUSIONS: These findings provide little evidence that alcohol is causally associated with age-related maculopathy.

Aged↗
PubMed1996

Molecular dynamics simulations of valinomycin and its potassium complex in homogeneous solvents.

Molecular dynamics simulations of kalinomycin (VM) and its potassium complex in water and in a Lennard Jones solvent are reported. In agreement with experimental evidence the structure of K(+)-VM in nonpolar solution is similar to the solid state structure whereas the structure of uncomplexed VM is not. In water uncomplexed VM retains the Lac and HyV faces (which are lost in nonpolar solution) and shows some similarity with the solid-state structure obtained by crystallization from dimethyl sulfoxide (DMSO). However, also in agreement with spectroscopic data a dynamic equilibrium between a set of conformers is established in both solvents. Our model reproduces the experimental dipole moment (3.6 D) of VM in nonpolar solution. We also observed the spontaneous decomplexation of K(+)-VM in water, with the ion passing through the HyV face in preference to the Lac face. Water attack was observed through both faces. The time scale for all conformational transitions is of the order of 100 ps, with structural changes associated with the (de)-complexation reaction controlled by the ring dihedrals in the vicinity of the L-lactic acid residues. Global structural functions, radial distribution functions, and VM ring dihedral analysis are presented, along with an analysis of the decomplexation event.

Algorithms↗