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Biomedical subjects

K Brock

Publications and source records attributed to K Brock.

At least 19 recordsLinked to original sources
PubMed2007

Effects of diet and exercise on plasma vitamin D (25(OH)D) levels in Vietnamese immigrant elderly in Sydney, Australia.

Vitamin D deficiency may be associated with osteoporosis and fractures in the elderly. In Australia where there is a sizeable Vietnamese population, research has not yet clarified the roles of diet, exercise and sun exposure in determining vitamin D status. Plasma samples for 25-hydroxy-vitamin D (25(OH)D); dietary intake of vitamin D and calcium; muscle strength and sun exposure were measured and weekly dairy intake, exercise levels and smoking habits were surveyed in free-living elderly of Vietnamese and Australian/British origin. There was marginal vitamin D deficiency (<37 nmol/L 25(OH)D) in 63% of Vietnamese but only in 37% of Australian/British born. Low dairy intake and no vigorous exercise were best predictors of vitamin D deficiency in Vietnamese, taking into account age, gender, dietary intake and sun exposure. Since these migrant elderly may not get adequate sun exposure due to either clothing customs or cultural norms that encourage fair (untanned) skin, it is important to encourage increased exercise and dairy intake.

Age Distribution↗
PubMed2004

Associations with Vitamin D deficiency in "at risk" Australians.

In a study of 185 elderly living in assisted care and 192 frail aged living in the community in the Sydney metropolitan area, nursing home residents were found to be at a 3-fold and hostel dwellers at a 2-fold risk of Vitamin D [25(OH)D] deficiency (<25 nmol/L) compared to self care residents. Middle Eastern people were found to be at 4-fold risk and Vietnamese a 3-fold risk of deficiency compared to their Australian counterparts. In recently arrived Chinese immigrants, Vitamin D deficiency, was found in 28%, and marginal levels (<37 nmol/L) in 60%, compared to the 34 and 76% found in our nursing home population, and 25 and 57% in hostel care residents. Of the Middle Eastern elderly, 58% were deficient and 83% marginal; although only 18% of Vietnamese were deficient, 68% had marginal Vitamin D status. Other factors associated with Vitamin D deficiency were mobility and sun exposure in assisted care, and low dietary Vitamin D and calcium intake, reduced exercise levels and high % body fat levels in the immigrant groups.

Aged↗
PubMed2003

Food, activity and family--environmental vs biochemical predictors of weight gain in children.

OBJECTIVE: To identify whether measures of energy intake and expenditure predict excessive weight gain over time in children and to describe how these measures relate to similar measures in parents. DESIGN: Prospective, descriptive study over 12 months with no intervention. SETTING: University teaching hospital. SUBJECTS: Children aged between 6.0 and 9.0 y. Recruitment was through advertisement. A total of 59 children (30 F), 41 mothers and 29 fathers. In all, 41 (69%) of the children were reviewed at 12 months (20 F). RESULTS: No significant correlations were identified between body mass index (BMI) z-score change in children over 12 months for any dietary variable or for any measures of energy expenditure, including hours of television viewing or percent time spent in low-, moderate- or high-intensity activity. The BMI z-score change over 12 months was significantly correlated with LDL cholesterol and Apo B/ApoA-1 ratio, independent of percent body fat (r=0.45, P=0.01; r=0.37, P=0.03). A significant positive correlation was found for mothers and girls for percent time in moderate to high activity (r=0.44, P=0.03) and between fathers and children for percent time spent in low activity (r=0.43, P=0.005). CONCLUSIONS: The study has been unable to identify environmental predictors that indicate propensity to faster weight gain over time in this cohort of children, but has extended the evidence on lifestyle-influenced biochemical predictors that do. An overall lack of vigorous activity in this age group, and correlations between parental and child activity and inactivity have been identified.

Adult↗
PubMed2001

An investigation of health behavior change in Vietnamese-born individuals living in Sydney, Australia.

OBJECTIVE: The purpose of this study was to look at rates of acculturation among Vietnamese immigrants, with particular emphasis on health behaviors. DESIGN: A volunteer sample was surveyed. SETTING/PARTICIPANTS: The participants were drawn from inner and western Sydney, Australia. Participants were asked for their perception of their English fluency as a measure of likely exposure to health promotion advertising and their food, social, exercise, drinking, and smoking habits. RESULTS: It was found that the longer the Vietnamese immigrants participants had lived in Australia, the less likely they were to smoke; in fact, the smoking rate of this population is as low as that of the Australian population as a whole. However the immigrants did not change their low rate of alcohol consumption. In addition, the Vietnamese who had lived longer in Australia significantly increased their daily exercise and started to eat more take-away foods. CONCLUSIONS: With respect to health promotion, these changes are mixed: smoking has decreased, but half the group had begun eating take-away foods; this factor, if combined with a lack of exercise, is likely to lead to obesity.

Acculturation↗
PubMed1999

Smoking and lipid cardiovascular risk factors in Vietnamese refugees in Australia.

BACKGROUND: The effects of smoking and sex on lipid risk factors for cardiovascular disease were examined among Vietnamese people newly arrived in Australia. METHODS: Immigrants recruited through Refugee Screening had anthropometric data recorded and blood collected to measure total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and triglyceride (TG) by Reflotron; apolipoprotein A-1 (apo A-1) and apolipoprotein B-100 (apo B) by immunoturbidimetric analyses (Turbitimer); and lipoprotein (a) (LP (a)) by ELISA. A questionnaire determined behavioral variables known to influence cardiovascular risk and Statview, Minitab, and SPSS were employed for data analysis. RESULTS: Lipoprotein profiles of men (n = 242) and women (n = 159) were compared. Crude TC and apo B were similar; HDL, apo A-1, and LP (a) were higher in women, TG was higher in men. After adjustment (age, BMI, WHR, years of smoking, and drinks per week), only apo A-1 and LP (a), were higher in women. "At risk" levels of TC or apo B did not differ by gender; risk of low apo A-1 was higher among men. Smokers had a significant risk (crude and adjusted) of low HDL, low apo A-1, and high LP (a). The sex difference in HDL was removed by a single adjustment for smoking; male smokers had higher LP (a) than male nonsmokers. CONCLUSION: Male and female Vietnamese immigrants had similar adjusted lipid profiles. Smoking had a marked detrimental effect on lipids.

Adult↗
PubMed1999

Leptin and total cholesterol are predictors of weight gain in pre-pubertal children.

OBJECTIVE: The aim of this study was to identify specifically which biochemical indices predict excessive weight gain over time in a cohort of pre-pubertal children. SUBJECTS: Fifty nine healthy pre-pubertal children (age: 6.3-9.8y). MEASUREMENTS: Children were defined anthropometrically and biochemically at baseline. Height and weight measurements were then repeated after six (n=52) and 12 months (n=37). RESULTS: Weight change after six months (defined by a change in body mass index (BMI) z-score from baseline) demonstrated no correlation with fasting plasma levels of leptin, insulin, insulin:glucose (IG) ratio, cholesterol, triglyceride or high density lipoprotein (HDL) cholesterol. However, after 12 months there was a significant negative correlation between BMI z-score change and initial plasma leptin (r=-0.35, P=0.048) and this relationship strengthened when adjusted for body fat (from bio-electrical impedance; r=-0.46, P=0.009). In addition, there was a significant positive relationship between plasma total cholesterol and BMI z score change (r=0.38, P=0.03) and this relationship remained unchanged when adjusted for body fat. No relationship was observed between weight change after 12 months and plasma levels of insulin, IG ratio, HDL cholesterol or triglyceride. CONCLUSION: Plasma leptin and total cholesterol were found to be predictive of weight gain over 12 months in a cohort of pre-pubertal children. These two potential predictors can be readily measured in clinical practice and these findings may represent a method of defining the 'at risk of obesity' state in childhood.

Anthropometry↗
PubMed1997

Long-term stroke risk in children with sickle cell disease screened with transcranial Doppler.

Stroke is an important complication of sickle cell disease. Stroke prediction is clinically important because it offers the possibility of primary prevention. In 1992, transcranial Doppler (TCD) evidence of elevated intracranial internal carotid or middle cerebral artery velocity was demonstrated to be associated strongly with an increased risk of ischemic stroke. This study extends the original study and includes 125 more children, longer follow-up, and intracranial hemorrhage in the stroke-risk model. Elevated time averaged mean maximum blood flow velocity, especially when velocity is 200 cm/sec or greater by TCD, was associated strongly with stroke risk. The cases not predicted by TCD point to the need for more information on the optimal timing of TCD surveillance for stroke risk.

Adolescent↗
PubMed1997

Mnemonic search, but not arithmetic transformation, is associated with psychophysiological inhibition.

The possibility that mnemonic search and arithmetic transformation induce transient heart rate (HR) slowing was studied. Transient HR slowing was assumed to result from the inhibition of premature responding during information processing. Twenty young men performed a 2-step reaction time task. Two precues were followed by a choice cue: 2 additional precues and 1 final choice cue. Choice cues were varied to compare spatial and perceptual-motor processing with mnemonic or arithmetic processing. Cardiac interbeat interval and impedance cardiograph measures were taken beat by beat. The preparation for the respond cue was associated with HR slowing followed by HR speeding associated with response initiation. Mnemonic search induced a transient HR slowing before the speeding initiated by the motor response. Arithmetic transformation did not, but processing of the arithmetic series decreased cue-induced transient HR slowing. Mnemonic search may be associated with a psychophysiological inhibition analagous to that observed in perceptual-motor tasks during response selection.

Adolescent↗
PubMed1997

Impact of level III verification on trauma admissions and transfer: comparisons of two rural hospitals.

PURPOSE: To study the impact of Level III verification and other changes in rural hospitals on trauma delivery and to examine factors affecting transfer to a Level I trauma center. SETTING: Two rural Kentucky hospitals and a Level I trauma center. METHOD OF REVIEW: Concurrent review of all trauma patients in 1988 and re-review of the same parameters in 1995. FINDINGS: In 1988, both hospitals had similar management practices in trauma care. A significant number of patients were transferred for (a) patient choice, (b) serious and/or multiple trauma, (c) specialty care in non-life threatening situations, and (d) to exclude a potentially serious problem seen on radiologic evaluation (usually questionable cervical spine or widened mediastinum). Both hospitals had major changes in trauma delivery. One hospital received Level III verification, and the other had changes that lessened the general surgeon's involvement with initial evaluation and treatment. A re-review in 1995 disclosed major changes at both institutions. Transfers to exclude radiologic abnormalities had virtually disappeared. The Level III status had increased the surgical involvement in that hospital; there was actually an increase in patients transferred to the Level I hospital and an increase in patient acuity. More operations were performed locally, and the care was more efficiently delivered. The other hospital had a large increase in transfers and decreased admissions locally as general surgical involvement decreased. CONCLUSIONS: The factors related to patient transfer for trauma care are complex and require careful elucidation to improve care. The development of a Level III trauma service appeared to increase the number of seriously injured patients treated in the rural hospital and the efficiency of the care delivered.

Concurrent Review↗
PubMed1997

Prediction of length of hospital stay following stroke.

The aim of this study was to investigate the potential of using an assessment of initial physical disability post stroke to predict length of hospital stay (LOS). A series of 106 patients with a primary diagnosis of stroke, admitted consecutively to St Vincent's Hospital Rehabilitation Unit over a 2-year period, was assessed at 2 weeks post stroke using the Mobility Scale for Acute Stroke (MSAS). This scale assesses the level of assistance required for a patient to perform five mobility tasks: bridging, sitting from supine, sitting, sitting to standing, and walking. A model utilizing MSAS data explained 69% of the variation in LOS. The results of this study may assist in developing resource utilization models in stroke rehabilitation.

Activities of Daily Living↗
PubMed1996

Body mass index and body fat distribution in newly-arrived Vietnamese refugees in Sydney, Australia.

Body mass index (BMI), body fat distribution and some behavioural variables were examined in an ethnic Vietnamese population newly arrived in Australia. The age range was 23 to 74 years for males (n = 246, mean = 38.8) and 24 to 66 for females (n = 165, mean = 36.4). Mean BMI was 20.62 +/- 2.65 (male) and 21.25 +/- 3.16 (female). Waist-to-hip ratio (WHR) was 0.844 (males) v 0.802 (females), p < 0.0001: waist was 73.7 cm (males) v 71.7 cm (females), (p = 0.007). Male smoking was 69%, female, 1%; the BMI of male non-smokers was higher than that of smokers 21.22 v 20.35 (p = 0.0017). Exercise patterns, diet or alcohol intake did not appear to affect BMI. The mean BMI of this refugee Vietnamese population is low by comparison with the Australian population. Vietnamese females although of lower mean BMI, have higher WHR than Australian females.

Adipose Tissue↗
PubMed1995

Plasma cholesterol and other cardiac risk factors in adolescent girls.

The aim was to examine the effects of smoking, physical activity, and body mass on total cholesterol and high density lipoprotein cholesterol (HDL-C) in adolescent schoolgirls in Sydney, Australia. Body mass index (BMI) and waist to hip ratio (WHR) were determined in 144 girls aged 15 to 18 years. Total cholesterol (TC) and HDL-C were estimated on fingerprick blood and behavioural variables assessed by questionnaire. Prevalence of overweight (> 90th centile for BMI) was less in Australian adolescents than reported from the USA. Smokers had lower total cholesterol than non-smokers; this was partly explained by a lower HDL-C in the smokers. Physical activity was associated with a less atherogenic TC/HDL-C ratio. Girls with BMI > 90th centile had higher mean TC/HDL-C and apoprotein B than the group as a whole but those > 90th centile for WHR did not.

Adolescent↗
PubMed1993

How are tonic and phasic cardiovascular changes related to central motor command?

We examined the influence of central motor command on heart rate, respiration, and peripheral vascular activity. Central command was enhanced or reduced using tendon vibration. Muscle tension was held constant permitting the examination of variation in central command. Experiment 1 demonstrated in 13 college-aged males an enhancement of heart rate and vascular responses to an isometric, extensor contraction when vibration of the flexor tendon was added. Experiment 2 asked whether changes in central command interacted with phasic cardiovascular changes such as stimulus-linked anticipatory cardiac deceleration. Twenty college-aged males performed either an isometric flexor or extensor contraction with or without flexor tendon vibration. As expected, vibration enhanced cardiovascular change with extensor contraction more than with flexor contraction. Relative to control contractions, however, the flexor change was not an absolute decrease in cardiovascular change. More importantly, tendon vibration failed to alter phasic cardiovascular changes. Force and central commands for force induce cardiovascular change, but this change seems independent of phasic changes induced by the anticipation and processing of environmental stimuli.

Adolescent↗
PubMed1992

On the synchrony of stopping motor responses and delaying heartbeats.

Recent evidence suggests that inhibition of a motor response may occur as late as the final stages of response execution. Response production involves central commands for autonomic support as well as motoric action. Autonomically controlled responses were used in conjunction with electromyographic and performance indices to examine the timing and flexibility of inhibition. Twenty young male Ss performed a choice reaction time task with stimuli timed according to when they occurred in relation to the R wave of the electrocardiogram. Stop signals, presented on 30% of the trials, induced inhibition. The performance and physiological results generally supported the horse-race model of inhibition. Inhibition was observed as late as during response execution. A short-latency, phasic lengthening of interbeat interval was suggested to reflect the midbrain coordination of the countermanding of response execution.

Adolescent↗
PubMed1991

Forearm, chest, and skin vascular changes during simple performance tasks.

Momentary changes in vascular variables were examined in four experiments which all induced preparation for an expected stimulus. Response requirements were minimized to permit examination of changes during stimulus presentation unconfounded with overt movement. The hypothesis examined was that vascular changes serve to maximize tissue perfusion at the time of anticipated action. Impedance plethysmographic measures of the chest and forearm were scored both for transit times and amplitude/slope indices. Similar indices were derived from photo-plethysmographic signals from the nail-bed of the thumb. The results suggested that preparatory vascular changes could be divided into an initial expectancy phase started at least 2 or 3 seconds prior to the anticipated events and a specific preparatory phase occurring just prior to and during stimulus presentation. Transit time shortening and maintained vasoconstriction characterized the initial expectancy phase when a finger movement, but not an effortful grip, was the anticipated response. Transit time lengthening and vasodilation generally characterized the specific preparation phase, but are disrupted when a signal inhibiting the response is likely to occur. Decelerative heart rate changes were positively related to the slope of the systolic rise in the chest impedance measure, suggesting that both cardiac and vascular changes may act together. Overall, the results were moderately supportive of the view that the heart and vasculature act together to maximize tissue perfusion at the time of anticipated action.

Adolescent↗
PubMed1991

Weak sensory stimuli induce a phase sensitive bradycardia.

We attempted to demonstrate that significant perceptual stimuli would induce different degrees of heart rate deceleration depending on when (phase) in the cardiac cycle they occurred. Relative to previous work, we concurrently examined a number of factors that might alter the amplitude of such a cardiac cycle time effect. Stimulus intensity and presence or absence of a speeded response were manipulated. Liminal stimuli and a perceptual rather than motor set were expected to maximize any cardiac cycle time effect. Respiratory phase, length of average interbeat interval, and number of trials were also investigated. Twenty-four college aged, male volunteers were randomly separated into equal groups receiving instructions either to judge which of two weak visual stimuli occurred or to execute a speeded, discriminative response to the stimuli. Discriminative stimuli were presented at either 0, 150, 250, 350, or 500 ms after the R-wave of the electrocardiogram. Stimuli were presented with an intensity that had yielded either 63% or 90% correct detections in a prior psychophysical assessment. A phase dependent deceleration occurred after both intensities of stimuli. Poststimulus deceleration was greater for stimuli in early to mid cycle as suggested by earlier work. As expected, this result was clear when the stimuli were presented during the expiratory phase of respiration. Neither perceptual/motor set nor stimulus intensity altered the phase sensitive deceleration. Thus, phase sensitive deceleration was confirmed using demanding sensory stimuli and an improved representational technique.

Adolescent↗
PubMed1991

Response inhibition initiates cardiac deceleration: evidence from a sensory-motor compatibility paradigm.

Two experiments tested the hypothesis that response selection processes alter the timing of the shift between anticipatory cardiac deceleration and acceleratory recovery. Experiment 1 compared changes in cardiac interbeat interval induced by the manipulation of sensory-motor compatibility in a four choice reaction time task. A direct spatial mapping between a linear array of light-emitting diodes (LEDs) was compared to randomly assigned, indirect (non-compatible) mappings. Experiment 2 repeated these two tasks and added a two choice condition with direct spatial mapping, a task frequently employed to examine heart rate deceleration. Fifteen college aged males participated in Experiment 1; 18 college aged males participated in Experiment 2. In both experiments anticipatory cardiac deceleration either reached a plateau or shifted to acceleration by the interbeat interval in which the stimulus occurred. In contrast to previous reports, a secondary deceleration, rather than cardiac acceleration, often followed the stimulus. The secondary deceleration was greater with non-compatible mapping, slow response speeds, and short intertrial intervals. The findings suggested that the motoric inhibition required during response selection induces a phasic cardiac deceleration.

Adolescent↗