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Biomedical subjects

M Prior

Publications and source records attributed to M Prior.

At least 19 recordsLinked to original sources
PubMed2006

Haemodynamic effects of AT1 inhibition and Ca2+-channel blockade in hypertensive patients during isometric stress.

To assess the effects of valsartan and amlodipine on the haemodynamics of forearm circulation in hypertensive patients undergoing isometric stress. A total of 24 patients with essential hypertension were subjected to a double blind-cross-over study. The artery left arm flow (strain gauge plethysmography), distensibility of digital arteries (piezoelectric plethysmography) and blood pressure were measured. District resistance was calculated as the ratio between mean arterial pressure and blood flow. The tests were performed at basal conditions (T0) and after 8 days (T8) of therapy with valsartan (160 mg) or amlodipine (10 mg), at rest and during handgrip (HG); treatments were inverted after 15 days of washout. Valsartan and amlodipine reduced blood pressure after 8 days (P<0.05), handgrip increased systolic and diastolic values and heart rate at T0 and only a slight raising in diastolic values at T8. The recovery time of pressure values was longer in hypertensives treated with amlodipine (P<0.05). The forearm flow increased after HG (at T0 an T8) and increased even further after valsartan (P<0.005). Valsartan increased arteriolar distensibility, expressed by the ratio between time to peak and total time (PT/TT) calculated on the sphygmic wave. Amlodipine did not affect PT/TT ratio, whereas it reduced local resistance (T8 vs T0, P<0.05). The reduction effect of valsartan on resistance was detectable also during handgrip, on the contrary amlodipine did not control the increase. Inhibition of AT1 is able to reduce haemodynamic modifications elicited by isometric stress in hypertensive patients.

Amlodipine↗
PubMed2006

Effects of smoking on cardiopulmonary baroreceptor activation and peripheral vascular resistance.

PATIENTS AND METHODS: We studied 16 healthy smokers and 16 nonsmokers acting as controls. We subjected smokers and nonsmokers to cardiopulmonary baroreceptor stimulation by studying forearm and common carotid haemodynamic and sympathovagal balance. Smokers repeated the tests after smoking one cigarette. Smokers and controls were subjected to passive elevation of the legs and the trunk in a horizontal position with pressure monitoring and measurement of the calibre and flow in the brachial and common carotid arteries using a colourDoppler ultrasound. We calculated forearm resistance and carotid wall tension. We also studied R-R variability, calculating the ratio between low frequency (LF) and high frequency (HF) R-R interval variability. RESULTS: During stimulation diastolic blood pressure values decreased in controls and in smokers at rest. After smoking one cigarette, smokers showed an increase in systolic and diastolic blood pressure as well as in the heart rate during stimulation. Humeral artery increased the calibre during stimulation in both groups; after cigarette smoking the calibre declined throughout the study phases. Forearm resistance decreased in both groups during stimulation at rest, but increased after cigarette smoking. The LF/HF ratio decreased during stimulation in both groups, and it increased at rest after smoking. Carotid diameter did not change in either group, and wall tension increased in smokers after smoking one cigarette. CONCLUSIONS: Smoking one cigarette increases resistance, impairs baroreflex and increases carotid wall tension in mild smokers. These findings may explain the higher rate of a cardiovascular event in smokers.

Adult↗
PubMed2004

Dopamine antagonist modulation of amphetamine response as detected using pharmacological MRI.

Functional magnetic resonance imaging (fMRI), employing BOLD-contrast, was used to measure changes in regional brain activation following amphetamine administration, either alone or after pre-treatment with the dopamine D1 receptor antagonist SCH23390, or the dopamine D2 receptor antagonist, sulpiride, in anaesthetised rat. After obtaining baseline data, rats (n=8) were given amphetamine (3 g/kg i.v) and volume data sets collected for 90 mins. Acute amphetamine challenge caused widespread increases in BOLD signal intensity in many subcortical structures with rich dopaminergic innervation, with decreases in BOLD contrast observed in the superficial layers of the cortex. Pretreatment with SCH23390 (n=8, 0.5 mg/kg, i.v) substantially attenuated the increases in BOLD activity in response to amphetamine, with lesser effects on the amphetamine-evoked decreases in BOLD signal. In contrast, sulpiride (n=8, 50 mg/kg, i.v) predominantly blocked the decrease in BOLD signal, having a smaller effect on the increases in BOLD signal. In summary, these data are supportive of the notion that different dopamine receptor types are responsible for separate components of the full amphetamine response. Furthermore the utility of BOLD contrast fMRI as a means of characterising the mechanisms of drug action in the whole brain has been demonstrated. Such studies may be of particular use for investigation of localised action and interaction of different dopaminergic agents.

Amphetamine↗
PubMed2004

What kind of visual spatial attention is impaired in neglect?

The distribution of spatial attention across the horizontal meridian of the visual field, as assessed by a simple reaction time (RT) paradigm, is dramatically abnormal in neglect patients. In the contralesional hemifield, RT increases sharply from centre to periphery, while in the ipsilesional hemifield, it decreases paradoxically from centre to mid-periphery. In the present study, we firstly asked whether this abnormal distribution of spatial attention is still present when patients know in advance the location of the impending stimulus, and second whether and to which extent it may be influenced by the concomitant presence of hemianopia. In Experiment 1, the stimuli were presented either predictably (blocks of same-point presentations) or unpredictably (blocks of randomised presentations) to one of several contralesional and ipsilesional field locations. As was the case for control subjects, neglect patients showed an overall RT decrease with same-point presentations. However, their abnormal contralesional RT lengthening and ipsilesional speeding were still present. In Experiment 2, the trials were blocked to same-hemifield presentations. In the ipsilesional field condition, neglect patients with and without hemianopia showed the same distorted distribution of attention favouring mid-periphery over central field locations. Two conclusions can be drawn from these experiments: first, the bulk of the abnormal deployment of spatial attention in neglect patients is related to an impairment of exogenous attention which cannot be compensated for by a spared endogenous control. Second, hemianopia does not affect the paradoxical speeding up of RT typically found in the mid-periphery of the ipsilesional field of neglect patients.

Adolescent↗
PubMed2002

Evaluation of a community intervention programme for preschool behaviour problems.

OBJECTIVES: To evaluate an early intervention project focused on improving child prereading skills and parent behaviour-management skills, for 4-year-old children in the western suburbs of Melbourne (Victoria, Australia). METHODOLOGY: Following screening of a large sample of preschoolers, four groups were constructed: (i) children receiving a phonological skills-based prereading package in their normal preschool programme; (ii) children whose parents attended six sessions of child behaviour management skill training; (iii) children who received both interventions; and (iv) a control group. Pre-, post-, 1 and 2 year follow-up measures were taken to assess effects on child behavioural and learning adjustment. RESULTS AND CONCLUSIONS: This community based intervention resulted in positive effects, despite being of low intensity, in achieving significantly less hyperactive/distractable behaviour in children from the combined intervention group at 2 years postintervention. Anxiety problems were also reduced at the post-treatment phase. The prereading package did not demonstrate any effects on reading skills and was deemed to be insufficiently intensive to affect a population of disadvantaged preschoolers. This universal-type of intervention was well accepted by the community, but there is need for further effort to increase recruitment of families of at-risk children into such programmes.

Child Behavior Disorders↗
PubMed2001

Vascular adhesion molecule-1 and markers of platelet function before and after a treatment with iloprost or a supervised physical exercise program in patients with peripheral arterial disease.

Platelet function and levels of vascular adhesion molecule-1 (VCAM-1) were investigated in 24 patients with peripheral arterial disease at Fontaine stage II undergoing a 2 weeks treatment with iloprost (0.5-2 ng/kg/h i.v. infused, 6 h/day) or a 2 weeks supervised physical training, randomly assigned. Patients were studied before (T0) and after (T14) treatments and 10 days later (T24). The adhesion of washed platelets to fibrinogen coated microwells was reduced after treatment both with iloprost (1.9+/-0.4 vs 6.8+/-0.7%; T24 vs T0; M+/-SEM; p<0.05) and physical exercise (3.0+/-1.0 vs 6.7+/-0.7; p<0.05) while adhesion to human plasma coated microwells was reduced only after treatment with iloprost (1.9+/-0.8 vs 5.8+/-0.9; p<0.05). The expression of fibrinogen receptor (glycoprotein IIb/IIIa) on platelets, measured by flow-cytometry was also reduced after iloprost treatment (17.1+/-1.5 vs 31.8+/-4.8 AU; p<0.05) and physical exercise (14.6+/-1.5 vs 34.0+/-3.3; p<0.05). Theurinaryexcretion of platelet thromboxane A2 metabolite 2,3-dinor-thromboxane B2 decreased only in patients treated with iloprost (154.7+/-97.9 vs 256.2+/-106.4 pg mg creatinine(-1); p<0.05). Similarly plasma VCAM-1 was lower in patients who were treated with iloprost (827.7+/-77.4 vs 999.0+/-83.8 ng ml(-1); p<0.05). In conclusion, both iloprost and physical exercise seem to act on reversible phenomena such as the expression of adhesion molecules or ex vivo adhesion, whereas only iloprost reduces thromboxane A2 biosynthesis in vivo. This anti-platelet activity seems to be extended in time and to be associated with an improvement in vascular function.

Aged↗
PubMed2001

Association of a polymorphism of the dopamine transporter gene with externalizing behavior problems and associated temperament traits: a longitudinal study from infancy to the mid-teens.

There have been reports that a variable number of tandem repeats (VNTR) polymorphism situated in the 3' untranslated region of the dopamine transporter gene is associated with attention-deficit hyperactivity disorder. On the basis of these findings, we predicted an association of this polymorphism with hyperactivity, other externalizing behavior problems, and related temperament traits in a general population sample. The association was investigated using children participating in a longitudinal study of childhood temperament and development. DNA was taken from 660 children who had been assessed for temperament from 4-8 months to 15-16 years, and for behavior problems from 3-4 to 15-16 years. No significant associations were found at any age. There are a number of methodological differences from earlier studies that might explain the lack of associations with hyperactivity. It is also possible that the earlier findings are not replicable.

Adolescent↗
PubMed2001

Poisoning with the recreational drug paramethoxyamphetamine ("death").

OBJECTIVE: To describe the clinical features of paramethoxyamphetamine (PMA; "death") poisoning and to compare these with those of people with self-reported "ecstasy" poisoning. DESIGN: Retrospective casenote review. PARTICIPANTS AND SETTING: 22 patients who presented to the Emergency Department of the Royal Adelaide Hospital (RAH), a major metropolitan teaching hospital, between 1 January 1996 and 31 December 1998 with PMA poisoning identified through urine drug screens; and 61 patients with self-reported ecstasy poisoning between 1 September 1997 and 31 December 1998 found through the hospital databases. RESULTS: Patients with PMA poisoning presented with tachycardia (64%), hyperthermia (temperature > 37.5 degrees C; 36%), coma (41%), seizures (32%), arrhythmias (23%), and QRS intervals > or = 100 ms (50%) with greater frequency and often greater severity than those with self-reported ecstasy poisoning. Two patients with PMA poisoning presented with severe hypoglycaemia (blood glucose level, < 1.5 mmol/L) accompanied by hyperkalaemia (K+ concentration, > 7.5 mmol/L). CONCLUSIONS: At our hospital, PMA poisonings accounted for most of the severe reactions among people who believed they had taken ecstasy. Hypoglycaemia and hyperkalaemia may be specific to PMA poisoning. PMA toxicity should be suspected with severe or atypical reactions to "ecstasy", and confirmed by chromatographic urine drug screens.

Adolescent↗
PubMed2001

MRI studies of the neurotoxic effects of L-2-chloropropionic acid on rat brain.

L-2-Chloropropionic acid (L-CPA) is selectively toxic to rat cerebellar granule cells; necrosis is first observed about 36 hours after administration of L-CPA (750 mg/kg p.o.) becoming more marked by 48 h. Parallel to the onset of cell death an increase in cerebellar water content and sodium concentration has been reported suggesting an oedematous reaction. In this study T(2)-weighted (T(2)WI) and diffusion weighted (DWI) imaging were used to detect the development of neuronal damage in the cerebellum of rats as a result of exposure to L-CPA. T(2)WI and DWI were not able to detect cerebellar abnormalities at 37 h post-dosing except for a slight swelling of the cerebellum. However, at 48 h post-dosing when cerebellar swelling and granule cell necrosis were marked, T(2)WI and DWI hyperintensities were observed in the cerebellum. Therefore, under the conditions of this study, MRI was not able to detect abnormalities in the cerebellum prior to the onset of the clinical signs of neurotoxicity or at the time of early histological changes. T(2)WI also suggested a marked increase in the amount of fluid in the ventricular system of rats 37 and 48 h after dosing; fluid accumulation was observed in all animals studied whether or not necrosis was detected. The occurrence of T(2)WI hyperintensity in the forebrain lead us to discover a new lesion in the habenular nucleus.

Animals↗
PubMed2001

Longitudinal predictors of behavioural adjustment in pre-adolescent children.

OBJECTIVES: Longitudinal data from infancy onwards, from the Australian Temperament Project, a prospective study of the temperament and development of a large and representative sample of Victorian children, were examined to identify predictors of psychological disorder at 11-12 years of age. METHOD: Those children scoring in the at-risk range for psychological disorder according to parents, teachers and self-reports using the Child Behaviour Questionnaire were selected at 11-12 years of age for in-depth assessment and comparison with a group of children with no history of adjustment problems. Analyses of group differences using longitudinal data gathered from infancy to 12 years focused on parent and teacher reports on child temperament and behaviour, and various facets of home and school adjustment. RESULTS: The strongest predictors of adjustment at 12 years were previous behaviour problems, along with some specific temperament factors involving self-regulation capacities and mother's overall rating of child difficulty. Results based on parallel teacher data including peer adjustment, and social and academic competence measures were consistent with parent data. CONCLUSIONS: Our research confirms the persistence of early appearing behaviour problems in a community sample and the longitudinal influence of temperament factors in childhood. The study supports the need for a focus on early intervention and prevention strategies in the child mental health field.

Adolescent↗
PubMed2001

Biochemical risk factors for cardiovascular disease in an aged male population: emerging vascular pathogens.

The progressive increase of deaths and morbidity from cardiovascular disease (CVD) in most developed societies has led to the formulation of preventive strategies and application of several diagnostic guidelines. However, there is emerging evidence that most panels and algorithms are inadequate and require urgent revision and updating. Therefore, the aim of this study was the evaluation of a wide cardiovascular risk profile in elderly male patients with acute myocardial infarction (AMI) or peripheral occlusive disease (POD). The risk profile was assessed by measuring conventional serum lipid and lipoprotein levels and emerging parameters: lipoprotein(a) (Lp[a]), homocysteine (Hcy), and C-reactive protein (CRP). The concentration of triglycerides, Lp(a), Hcy and the total cholesterol/high-density lipoprotein (TC/HDL) ratio were significantly higher in both classes of patients than in a population of matched healthy controls and, similarly, patients with CVD displayed lower plasma values of HDL. No significant differences were observed for TC, low-density lipoprotein (LDL), and CRP. Patients with POD exhibited a marked atherogenic profile, as attested by substantially increased values of Hcy, Lp(a), triglycerides, and TC/HDL ratio. The frequency distributions of Lp(a) and Hcy concentrations were markedly shifted toward upper values in both classes of patients than in controls. In multivariate regression analysis, Lp(a) and Hcy were the best predictors for AMI, whereas Lp(a), Hcy, and the TC/HDL ratio were the best predictors for POD. Taken together, these data suggest that Lp(a) and Hcy excesses might exert a central role in the development of atherosclerotic disease in elderly male patients. Thereby, the inclusion of those tests, along with the TC/HDL ratio and other more conventional analyses in panels for the evaluation of the cardiovascular risk might be profitable in terms of effectual prevention.

Age Factors↗
PubMed2001

Redundancy gain in the stop-signal paradigm: implications for the locus of coactivation in simple reaction time.

The authors carried out 2 experiments designed to cast light on the locus of redundancy gain in simple visual reaction time by using a stop-signal paradigm. In Experiment 1, the authors found that single visual stimuli were more easily inhibited than double visual stimuli by an acoustic stop signal. This result is in keeping with the idea that redundancy gain occurs prior to the ballistic stage of the stop-signal task. In Experiment 2, the authors found that the response to an acoustic go signal was more easily inhibited by a double than by a single visual stop signal. This result provides conclusive evidence for a redundancy gain in the stop process--in a process that does not involve a motor response but rather its inhibition.

Adult↗
PubMed2000

A longitudinal study of the role of childhood temperament in the later development of eating concerns.

OBJECTIVE: This study examined the relationship between childhood temperament and the later development of eating and body concerns in early adolescent children. METHOD: The Australian Temperament Project has followed a cohort of children from birth, assessing temperament factors such as Negative Emotionality, Persistence, Approach/Withdrawal, and Activity. Using a longitudinal design, the study reports on the relationship between temperament measured from infancy onward and eating and body concerns at 12-13 years of age. Participants (597 girls, 631 boys) completed the Eating Disorders Inventory subscales Drive For Thinness, Body Dissatisfaction, and Bulimia, and an estimate of their current size. Parents described their child's temperament and body size. RESULTS: High Negative Emotionality and low Persistence were the factors most associated with risk status over time, particularly in girls. DISCUSSION: While it is unlikely that temperamental characteristics per se lead to disordered eating, it is argued that in combination with other risk factors, certain temperamental characteristics may increase vulnerability.

Adolescent↗
PubMed2000

Prevalence and characteristics of escape rhythms after radiofrequency ablation of the atrioventricular junction: results from the registry for AV junction ablation and pacing in atrial fibrillation. Ablate and Pace Trial Investigators.

BACKGROUND: Radiofrequency ablation of the atrioventricular junction is a well-established procedure for the management of atrial fibrillation refractory to medical therapy. However, there are few data available on the prevalence and characteristics of the escape rhythms that are present after the procedure. METHODS: The Ablate and Pace Trial was a prospective, multicenter registry of atrioventricular junction ablation and pacing in atrial fibrillation. Ablation of the atrioventricular junction was accomplished with radiofrequency energy with standard techniques. Before discharge from the hospital, patients underwent a systematic analysis of the rate and morphologic features of the escape rhythm, if any, that was present when the pacing rate was gradually decreased. RESULTS: There were 156 patients from 16 centers who underwent attempted radiofrequency ablation of the atrioventricular junction. The procedure was successful in 155 (99%) of 156 patients. An escape rhythm was present in 104 patients (67%) after radiofrequency ablation. The escape rate ranged from 11 to 65 beats/min (mean 39 +/- 10 beats/min). Only 49 patients (31%) had an escape rate >/=40 beats/min. Of the 104 patients with an escape rhythm, 53 patients (51%) had a QRS that was unchanged from baseline. There was no correlation between the number of radiofrequency applications and the presence of an escape rhythm. CONCLUSION: The majority of patients who undergo radiofrequency catheter ablation of the atrioventricular junction are pacemaker dependent after the procedure, as defined by lack of an escape rhythm or the presence of an escape rhythm that is <40 beats/min.

Adult↗