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Biomedical subjects

G D Smith

Publications and source records attributed to G D Smith.

At least 127 records · Page 7Linked to original sources
PubMed2000

Fourier analysis of sinusoidally driven thalamocortical relay neurons and a minimal integrate-and-fire-or-burst model.

We performed intracellular recordings of relay neurons from the lateral geniculate nucleus of a cat thalamic slice preparation. We measured responses during both tonic and burst firing modes to sinusoidal current injection and performed Fourier analysis on these responses. For comparison, we constructed a minimal "integrate-and-fire-or-burst" (IFB) neuron model that reproduces salient features of the relay cell responses. The IFB model is constrained to quantitatively fit our Fourier analysis of experimental relay neuron responses, including: the temporal tuning of the response in both tonic and burst modes, including a finding of low-pass and sometimes broadband behavior of tonic firing and band-pass characteristics during bursting, and the generally greater linearity of tonic compared with burst responses at low frequencies. In tonic mode, both experimental and theoretical responses display a frequency-dependent transition from massively superharmonic spiking to phase-locked superharmonic spiking near 3 Hz, followed by phase-locked subharmonic spiking at higher frequencies. Subharmonic and superharmonic burst responses also were observed experimentally. Characterizing the response properties of the "tuned" IFB model leads to insights regarding the observed stimulus dependence of burst versus tonic response mode in relay neurons. Furthermore the simplicity of the IFB model makes it a candidate for large scale network simulations of thalamic functioning.

Animals↗
PubMed2000

Comparison of risk factors for stroke incidence and stroke mortality in 20 years of follow-up in men and women in the Renfrew/Paisley Study in Scotland.

BACKGROUND AND PURPOSE: The aim of this study was to relate risk factors in middle-aged men and women to stroke incidence (defined by having a hospital discharge with a main diagnosis of stroke) and compare this with the associations between risk factors and stroke mortality. METHODS: In the early to mid-1970s, when they were 45 to 64 years of age, 7052 men and 8354 women from the Renfrew/Paisley prospective cohort study in Scotland were screened. Risk factors measured included blood pressure, blood cholesterol and glucose, respiratory function, cardiothoracic ratio, smoking habit, height, body mass index, preexisting coronary heart disease, and diabetes. These were related to stroke incidence over 20 years of follow-up. RESULTS: Diastolic and systolic blood pressure, smoking, cardiothoracic ratio, preexisting coronary heart disease, and diabetes were positively related to stroke incidence for men and women, whereas adjusted FEV(1) (forced expiratory volume in 1 second) and height were negatively related. Cholesterol was not related to stroke. Glucose for nondiabetic subjects had a U-shaped relationship with stroke. Body mass index was not clearly related to stroke, although participants with the highest body mass index had the highest stroke rate. Former smokers had similar stroke rates to never-smokers. Tests between the associations of risk factors and stroke incidence revealed these were not statistically different from the associations with stroke mortality. CONCLUSIONS: The risk factors had a similar effect on stroke incidence as on stroke mortality. Epidemiological studies with information on stroke mortality are likely to give results applicable to stroke incidence.

Blood Glucose↗
PubMed2000

Influence of socioeconomic circumstances in early and later life on stroke risk among men in a Scottish cohort study.

BACKGROUND AND PURPOSE: The purpose of the study was to investigate stroke risk by socioeconomic measures. METHODS: The analysis was based on a large cohort study of 5765 working men, from 27 workplaces in Scotland, who were screened between 1970 and 1973. Stroke was defined as having a hospital admission with a main diagnosis of stroke or dying of stroke in the 25-year follow-up period. RESULTS: There were 416 men who had a stroke. Men with manual occupations when screened, on first entering the workforce, men with manual occupations, and men whose fathers had manual occupations had significantly higher rates of stroke than men in the nonmanual categories. Men who left full-time education at age 16 years or under also had significantly higher rates of stroke. Men living in more deprived areas had higher rates of stroke, but the rates were not statistically significant. The most marked difference was in relation to father's social class, and although adjusting for risk factors for stroke attenuated the relative rates, men whose fathers were in manual social classes had higher relative rates of stroke than men whose fathers were in nonmanual classes (adjusted relative rate for father's social class III manual was 1.37 [95% CI 1.03 to 1.81] and for father's social class IV or V was 1.46 [1.09 to 1.96]). Men who were upwardly mobile (father's social class manual, own social class nonmanual) had a rate of stroke similar to that of stable manual men. CONCLUSIONS: Poorer socioeconomic circumstance was associated with greater stroke risk, with adverse early-life circumstances of particular importance.

Cohort Studies↗
PubMed2000

Learning to live with complexity: ethnicity, socioeconomic position, and health in Britain and the United States.

The relation between ethnicity, socioeconomic position, and health is complex, has changed over time, and differs between countries. In the United States there is a long tradition of treating ethnic group membership simply as a socioeconomic measure, and differentials in health status between African Americans and groups of European origin have been considered purely socioeconomic. A contrary position sees the differences as either "cultural" or due to inherent "racial" differences. Although conventional socioeconomic indicators statistically explain much of the health difference between African Americans and Americans of European origin, they do not tell the full story. Incommensurate measures of socioeconomic position across ethnic groups clearly contribute to this difference. Additional factors, such as the extent of racism, are also likely to be important. The interaction of ethnicity, social position, and health in Britain is similarly complex. Studies that inadequately account for socioeconomic circumstances when examining ethnic-group differences in health can reify ethnicity (and its supposed correlates); however, the reductionist attribution of all ethnic differences in health to socioeconomic factors is untenable. The only productive way forward is through studies that recognize the contingency of the relations between socioeconomic position, ethnicity, and particular health outcomes.

Censuses↗
PubMed2000

The contribution of risk factors to stroke differentials, by socioeconomic position in adulthood: the Renfrew/Paisley Study.

OBJECTIVES: This study investigated stroke differentials by socioeconomic position in adulthood. METHODS: The relation of risk of stroke to deprivation category and social class was assessed among 6955 men and 7992 women who were aged 45 to 64 years and had been screened in 1972 to 1976. RESULTS: A total of 594 men and 677 women had a hospital admission for stroke or died from stroke. There were large differences in stroke by deprivation category or social class. Adjustment for risk factors (smoking, blood pressure, height, respiratory function, body mass index, cholesterol, diabetes, and preexisting heart disease) attenuated these differences. CONCLUSIONS: Risk factors for stroke can explain some of the socioeconomic differences in stroke risk. Women living in the most deprived areas seem particularly at risk of stroke.

Diabetes Complications↗
PubMed2000

The effects of dietary supplementation on growth and adult mortality: a re-analysis and follow-up of a pre-war study.

The aim of this study was to re-analyse a diet supplementation study conducted in the 1930s and investigate the effects of food supplementation on children's growth and later adult mortality. A non-randomised controlled trial was carried out in eight of the sixteen centres participating in the Carnegie Survey of Diet and Health in pre-war Britain (1937-39). Food supplements were given for 12 months either at school or as food parcels sent to the family home. 545 children aged 2-14 received food supplements and 494 children of a similar age acted as their controls. The children came from 465 families. The increase in childhood height and its components-leg length and trunk length-over 12 months follow-up were measured. Mortality from all causes over 60 years follow-up to 1998 was also assessed. There were important differences between fed and control children at baseline. Supplemented children came from larger families with poorer diets and most were examined, on average, 12 days later than control children. After adjustment for baseline imbalances those receiving supplements increased in height by 3.7 mm (95% CI 1.9-5.5) more than the controls. After adjustment, most of the difference in growth appeared to arise as a result of increases in leg length. After adjustment for confounding factors measured in childhood, no significant effect of childhood food supplements on adult mortality was seen. The age-adjusted hazard ratio for all cause mortality was higher in the supplemented compared to control subjects: 1.13 95% CI (0.77-1.64). We found that provision of childhood food supplements led to increased growth amongst supplemented children. The increases in height in this study were mainly as a result of increases in leg length and are similar to those found in a more recent randomised trial in South Wales. Whilst other analyses suggest that childhood height is important in predicting adult mortality patterns, we found no significant effect of childhood food supplements on adult mortality patterns in this study, although the study lacked statistical power to detect small but, nevertheless, important differences in mortality. Larger randomised trials with long term follow-up would be required to investigate the impact of childhood food supplementation on adult health.

Adolescent↗
PubMed2000

The influence of gender, social circumstances and smoking on survival: the Renfrew and Paisley study.

The present study aimed to compare survival to age 75 between men and women, by social circumstances and smoking behaviour. A 20 year follow up was carried out of a large representative cohort of Scottish men and women in the Renfrew and Paisley study, and was combined with Scottish mortality statistics. 6831 men and 7993 women aged 45-64 y at time of examination (between 1972 and 1976) were considered. Combining the estimates from the Renfrew and Paisley study with those from Scottish mortality statistics for men and women younger than 45 y of age, it was calculated that 28% of the male smokers and 44% of the male never smokers in disadvantaged social circumstances will have survived to age 75 y, compared with 46% and 56% of the female smokers and never smokers respectively. In more privileged social circumstances, 41% of the male smokers and 62% of the male never smokers will have survived to age 75 y, compared with 56% and 70% of the female smokers and never smokers respectively. The difference between male smokers in low social classes and female never smokers in high social classes is 42% in absolute terms (28% vs 70%), which gives an indication of the combined influence of gender, social circumstances and smoking on survival. These results show that gender, social circumstances and smoking are important determinants of mortality which have led to substantial differences in survival. The influence of additional factors related to mortality could usefully be compared to these to put their effects into perspective.

Adolescent↗
PubMed2000

How accurately are height, weight and leg length reported by the elderly, and how closely are they related to measurements recorded in childhood?

BACKGROUND: This paper examines (1) the accuracy of self-reported height, leg length and weight in a group of subjects aged 56-78; (2) whether recent measurement of height and weight influences the accuracy of self-reporting and (3) associations between childhood and adult height, leg length and BMI measured in old age. METHODS: All 3182 surviving members of the Boyd Orr cohort were sent postal questionnaires in 1997-1998 and a sub-sample (294) was also clinically examined. RESULTS: Self-reported height was overestimated and body mass index (BMI), based on reported height and weight, underestimated. The mean difference between self-report and measured values were for height: 2.1 cm in males and 1.7 cm in females; for BMI the difference was -1.3 kg/m(2) in males and -1.2 kg/m(2) in females. Shorter individuals and older subjects tended to over-report their height more than others. The overweight under-reported their weight to a greater extent. Recent measurement appeared to decrease over-reporting of height but not weight. Correlations between self-report and measured height and BMI were generally over 0.90, but weaker for leg length (r = 0.70 in males and 0.71 in females). Adult height and leg length were quite closely related to their relative values in childhood (correlation coefficients ranged from 0.66 to 0.84), but associations between adult and childhood BMI were weak (r = 0.19 in males and 0.21 in females). CONCLUSIONS: Self-reported measures of height and weight may be used in studies of the elderly although systematic reporting errors may bias effect estimates. As overweight individuals tend to under-report and the short and underweight tend to over-report, studies investigating associations of disease with height and weight using self-reported measures will underestimate effects. The weak associations between childhood and adult BMI indicate that associations between childhood adiposity and adult cardiovascular disease found in this cohort may reflect the specific effect of childhood overweight, rather than its persistence into adulthood. This suggests that avoidance of adiposity may be as important in childhood as in adulthood.

Aged↗
PubMed2000

Improving the environment of mice by using synthetic gauze pads.

We conducted a study to evaluate the use of synthetic gauze pads for improving the environment of mice. To evaluate differences in clinical and pathology parameters, we used two treatment groups of mice, which were housed with or without gauze pads. The mice were assigned to the study at 5 to 7 weeks of age, and the study lasted 1 year. The mice were housed individually in stainless-steel ventilated cages with wire-mesh floors. Clinical observations, body weights, and food consumption were recorded frequently during the study. A complete necropsy, with histopathologic evaluation of tissues and collection of blood for clinical pathology, was performed at completion of the study. The mice with gauze pads preferred to rest on them. In addition, these mice showed a statistically significant reduction in food consumption, but their body weights and weight gains did not differ from those of animals without gauze pads. Synthetic gauze pads provide an improved environment for mice housed in cages with wire floors and may produce reduced food consumption. Gauze pads in the cages of mice do not seem to influence body weight gain, clinical signs, clinical pathology, or morphologic pathology.

Animal Welfare↗
PubMed1999

Involvement of the compatible solutes trehalose and sucrose in the response to salt stress of a cyanobacterial Scytonema species isolated from desert soils.

The response to moderate salt stress of a Scytonema species isolated from a soil crust in the arid region of central Australia was studied. An increase in intracellular trehalose and sucrose concentrations was detected by NMR and HPLC analysis following salt stress, maximal amounts being produced by exposure to 150 mM NaCl after 48 h. When the organism was subsequently returned to normal growth conditions, the cellular concentrations of these solutes decreased. The biosynthesis of trehalose and sucrose was studied and found, in both cases, to involve both sugar phosphate synthase and phosphatase enzymes. The combined synthase activities and the individual phosphatase activities in cell extracts were increased by salt stress. Trehalose phosphorylase was the only catabolic enzyme detected for trehalose; neither trehalase nor phosphotrehalase activities could be detected. This is the first report of trehalose phosphorylase activity in cyanobacteria. Both trehalose and sucrose phosphorylase activities increased in salt-stressed cells, whereas the activity of invertase did not change.

Chromatography, High Pressure Liquid↗
PubMed1999

Childhood socioeconomic position and adult cardiovascular mortality: the Boyd Orr Cohort.

The relation between childhood socioeconomic position and adult cardiovascular mortality is examined in 3,750 individuals whose families took part in the Carnegie survey of family diet and health in England and Scotland between 1937 and 1939. The trend in coronary heart disease mortality across social position groups was not statistically significant at conventional levels (p = 0.12), while a strong linear trend was seen for stroke mortality (p = 0.01). Adjustment for the Townsend deprivation index of area of residence during adult life did not materially alter these findings, indicating that the effects of socioeconomic influences upon particular cardiovascular diseases differ according to the age at which they are experienced.

Age of Onset↗
PubMed1999

Ecological study of social fragmentation, poverty, and suicide.

OBJECTIVES: To investigate the association between suicide and area based measures of deprivation and social fragmentation. DESIGN: Ecological study. SETTING: 633 parliamentary constituencies of Great Britain as defined in 1991. MAIN OUTCOME MEASURES: Age and sex specific mortality rates for suicide and all other causes for 1981-92. RESULTS: Mortality from suicide and all other causes increased with increasing Townsend deprivation score, social fragmentation score, and abstention from voting in all age and sex groups. Suicide mortality was most strongly related to social fragmentation, whereas deaths from other causes were more closely associated with Townsend score. Constituencies with absolute increases in social fragmentation and Townsend scores between 1981 and 1991 tended to have greater increases in suicide rates over the same period. The relation between change in social fragmentation and suicide was largely independent of Townsend score, whereas the association with Townsend score was generally reduced after adjustment for social fragmentation. CONCLUSIONS: Suicide rates are more strongly associated with measures of social fragmentation than with poverty at a constituency level.

Adult↗