Assessments of flow by transcranial Doppler ultrasound in the middle cerebral artery during exercise in humans.
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This study examined the consistency between three indexes of cerebral blood flow (CBF) obtained by using transcranial Doppler ultrasound in eight human volunteers. Each subject undertook three sessions of graded exercise, consisting of 6 min of rest, 6 min at 20% of maximal oxygen uptake (VO2 max), 6 min at 40% VO2 max, and 6 min of recovery. Values were obtained every 10 ms for the velocity associated with the maximal frequency of the Doppler shift (VP), the intensity-weighted mean velocity (VIWM), and total signal power (P). Beat-by-beat averages for three indexes (P, IWM, provided significantly different results for the percent changes in CBF with exercise. At 20% of VO2 max, P and IWM showed significant (P < 0.05) increases of 8 and 6%, respectively, whereas showed a nonsignificant increase of 3%. At 40% of VO2 max, P and IWM showed significant (P < 0.05) increases of 14 and 8%, respectively, whereas showed a nonsignificant increase of 4%. Our results suggest that the increase in CBF with exercise that has been reported with transcranial Doppler ultrasound needs to be treated with caution, as much of the response could arise as an artifact from the increase in amplitude and frequency of the arterial pressure waveform. (+info)
Differential expression of stress proteins in rat myocardium after free wheel or treadmill run training.
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High-intensity treadmill exercise increases the expression of a cardioprotective, inducible 72-kDa stress protein (SP72) in cardiac muscle. This investigation examined whether voluntary free wheel exercise training would be sufficient to confer a similar response. Male Sprague-Dawley rats were randomly assigned to either treadmill (TM-Tr) or free wheel (FW-Tr) training groups. By the end of the 8-wk training period, TM-Tr animals ran 1 h/day, 5 days/wk up a 10% grade, covering a distance of 8,282 m/wk. FW-Tr rats ran, on average, 5,300 m/wk, with one-third of the animals covering distances similar to those for the TM-Tr group. At the time of death, hearts of trained and caged sedentary control (Sed) animals were divided into left (LV) and right (RV) ventricles. Citrate synthase activity and the relative immunoblot contents of SP72, SP73 (the constitutive isoform of the SP70 family), and a 75-kDa mitochondrial chaperone (SP75) were subsequently determined. LV and RV did not differ on any measure, and SP73, SP75, and citrate synthase were not affected by training. Cardiac SP72 levels were elevated over fourfold in both ventricles of TM-Tr compared with RV of FW-Sed rats. Despite the animals having run a similar total distance, cardiac SP72 content in FW-Tr rats was not different from that in Sed animals. These data indicate that voluntary exercise training is insufficient to elicit an elevation of SP72 in rat heart and suggest that exercise intensity may be a critical factor in evoking the cardioprotective SP72 response. (+info)
Exertional dyspnoea in patients with airway obstruction, with and without CO2 retention.
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BACKGROUND: Dyspnoea is a common and disabling symptom in patients with cardiopulmonary disease. Unfortunately the mechanisms that produce dyspnoea are still poorly understood. The relationship between dyspnoea and the load on the ventilatory muscles, chemical drive, and ventilatory indices was therefore assessed in patients with obstructive pulmonary disease during an incremental exercise test. METHODS: Fifty patients with a wide range of obstructive pulmonary disease (mean forced expiratory volume in one second (FEV1) 66.1 (28.8)% predicted) performed an incremental cycle ergometer test. A subdivision was made between subjects with CO2 retention (delta PaCO2 > or = 0, n = 22) and subjects without CO2 retention (delta PaCO2 < 0, n = 28) during exercise. During the test dyspnoea (Borg score), oesophageal pressures (mechanical load on the ventilatory muscles (time tension index (TTI), blood gas tensions, and minute ventilation were measured. Correlations for changes in mechanical and chemical factors with changes in dyspnoea score were calculated to assess relevant factors. An analysis of covariance was used to examine whether there was a relationship between dyspnoea score and each of these factors and whether this relationship was different between the subgroups with and without CO2 retention. Multiple regression analysis was used to assess the independent effect of each parameter on dyspnoea sensation. Furthermore, the amplitude of pleural pressure swing ((Pi + Pe)act) generated at maximal work load (Ptot, an indication of the load on all respiratory muscles) was calculated. Analysis of covariance was used to assess whether there was a relationship between tidal volume (VT) and Ptot and whether this relationship was different between the groups (slopes are an expression of the length-tension inappropriateness, LTI). RESULTS: In the total group and the group without CO2 retention a significant correlation between dyspnoea and the increase in the inspiratory time tension index (TTIi) was present. In the group with CO2 retention a significant correlation was seen between dyspnoea and delta PaCO2. The factors delta PaO2, delta VE%MVV and delta (VT/Ti) showed a correlation with a p value of < or = 0.10 both in the total group and in those without CO2 retention. In an analysis of covariance the relationship between dyspnoea score and delta PaCO2 appeared to be significantly different between the two subgroups, being more pronounced in the group with CO2 retention. No other relationships with change in dyspnoea score were found. There was no significant relationship between VT and Ptot in the total group nor in the two subgroups, indicating some length-tension inappropriateness in both groups. CONCLUSIONS: In patients with distinctive pulmonary disease who are normocapnic or hypocapnic the mechanical load (delta TTIi) and length-tension inappropriateness (LTI) on ventilatory muscles seem to be the main determinant of exertional dyspnoea. As soon as hypercapnia occurs, this seems to override all other inputs for dyspnoea. (+info)
Decreased insulin-stimulated GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats.
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It was recently found that the effect of an exercise-induced increase in muscle GLUT-4 on insulin-stimulated glucose transport is masked by a decreased responsiveness to insulin in glycogen-supercompensated muscle. We evaluated the role of hexosamines in this decrease in insulin responsiveness and found that UDP-N-acetyl hexosamine concentrations were not higher in glycogen-supercompensated muscles than in control muscles with a low glycogen content. We determined whether the smaller increase in glucose transport is due to translocation of fewer GLUT-4 to the cell surface with the 2-N-4-(1-azi-2,2,2-trifluroethyl)-benzoyl-1, 3-bis(D-mannose-4-yloxy)-2-propylamine (ATB-[2-3H]BMPA) photolabeling technique. The insulin-induced increase in GLUT-4 at the cell surface was no greater in glycogen-supercompensated exercised muscle than in muscles of sedentary controls and only 50% as great as in exercised muscles with a low glycogen content. We conclude that the decreased insulin responsiveness of glucose transport in glycogen-supercompensated muscle is not due to increased accumulation of hexosamine biosynthetic pathway end products and that the smaller increase in glucose transport is mediated by translocation of fewer GLUT-4 to the cell surface. (+info)
Ambulatory blood pressure in schoolchildren.
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OBJECTIVE: To define the range and variability of ambulatory blood pressure in normal schoolchildren. DESIGN: Prospective study. METHODS: Resting blood pressure of 1121 schoolchildren from Newcastle upon Tyne was recorded. An ambulatory blood pressure device, which uses both auscultatory (Korotkoff) and oscillometric methods of blood pressure measurement, was then put in place for 24 hours. RESULTS: The day was divided into three time periods: school, home, and night time. Normal centiles for blood pressure for each of these time periods were obtained and many daytime readings were outside reported normal resting levels. The normal variation of blood pressure was quantified by comparing each of these time periods with the resting readings. Resting systolic blood pressure did not predict 24 hour mean systolic blood pressure. CONCLUSIONS: The availability of normal ambulatory blood pressure data on the level and variation of blood pressure in children may facilitate the early identification of hypertension in this age group. (+info)
Risk factors for neck and upper limb disorders: results from 24 years of follow up.
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OBJECTIVES: To investigate associations between different potential risk factors, related and not related to work, and disorders of the neck and upper extremities occurring up to 24 years later. METHODS: The study comprised 252 women and 232 men, Swedish citizens, 42-59 years of age and in a broad range of occupations. Information about potential risk factors was available from a former study conducted in 1969. Data on disorders of the neck, shoulder, and hand-wrist disorders were obtained retrospectively for the period 1970-93. RESULTS: Risk factors were found to differ between the sexes. Among women over-time work, high mental workload, and unsatisfactory leisure time were associated with disorders in the neck-shoulder region. Interaction was found between high mental workload and unsatisfactory leisure time. Neck symptoms earlier in life were associated with recurrent disorders. Hand and wrist disorders were associated mainly with physical demands at work. Among men blue collar work and a simultaneous presence of high mental workload and additional domestic workload predicted disorders in the neck-shoulder region. CONCLUSIONS: Factors related and not related to work were associated with disorders of the neck, shoulders, and hands and wrist up to 24 years later in life. These included factors related to working hours which previously have not been noted in this context. Interactions between risk factors both related and not related to work were commonly found. (+info)
Effects of physical training and its cessation on the hemostatic system of obese children.
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BACKGROUND: Physical training can improve hemostatic function in adults, thereby reducing heart disease risk, but no information is available in children on whether physical training can enhance hemostatic function. OBJECTIVE: The purpose of this investigation was to examine the effects of a physical training program on hemostatic variables in a biethnic group of obese children. DESIGN: Children were randomly assigned to 2 groups. Group 1 participated in physical training for 4 mo and then ceased physical training for 4 mo, whereas group 2 did no physical training for the first 4 mo and then participated in physical training for 4 mo. Plasma hemostatic variables [fibrinogen, plasminogen activator inhibitor 1 (PAI-1), and D-dimer) were measured at months 0, 4, and 8. RESULTS: Analyses of variance revealed no significant group-by-time interactions for the hemostatic variables. When data from both groups were combined there was a significant decrease in D-dimer after 4 mo of physical training (P < 0.05). Factors explaining individual differences in responsiveness to the physical training revealed that individuals with greater percentage fat before physical training showed greater reductions in fibrinogen and D-dimer, and that blacks showed greater reductions in D-dimer than whites (P < 0.05). Stepwise multiple linear regression showed that only higher prephysical training concentrations of fibrinogen, PAI-1, and D-dimer explained significant proportions of the variation in changes in these variables. CONCLUSIONS: In obese children, 4-mo periods of physical training did not lead to significant changes in hemostatic variables. Children with greater adiposity and concentrations of hemostatic factors before physical training showed greater reductions in hemostatic variables after physical training than did children with lesser values. (+info)
Colorectal cancer: molecules and populations.
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The epidemiology and molecular biology of colorectal cancer are reviewed with a view to understanding their interrelationship. Risk factors for colorectal neoplasia include a positive family history, meat consumption, smoking, and alcohol consumption. Important inverse associations exist with vegetables, nonsteroidal anti-inflammatory drugs (NSAIDs), hormone replacement therapy, and physical activity. There are several molecular pathways to colorectal cancer, especially the APC (adenomatous polyposis coli)-beta-catenin-Tcf (T-cell factor; a transcriptional activator) pathway and the pathway involving abnormalities of DNA mismatch repair. These are important, both in inherited syndromes (familial adenomatous polyposis [FAP] and hereditary nonpolyposis colorectal cancer [HNPCC], respectively) and in sporadic cancers. Other less well defined pathways exist. Expression of key genes in any of these pathways may be lost by inherited or acquired mutation or by hypermethylation. The roles of several of the environmental exposures in the molecular pathways either are established (e.g., inhibition of cyclooxygenase-2 by NSAIDs) or are suggested (e.g., meat and tobacco smoke as sources of specific blood-borne carcinogens; vegetables as a source of folate, antioxidants, and inducers of detoxifying enzymes). The roles of other factors (e.g., physical activity) remain obscure even when the epidemiology is quite consistent. There is also evidence that some metabolic pathways, e.g., those involving folate and heterocyclic amines, may be modified by polymorphisms in relevant genes, e.g., MTHFR (methylenetetrahydrofolate reductase) and NAT1 (N-acetyltransferase 1) and NAT2. There is at least some evidence that the general host metabolic state can provide a milieu that enhances or reduces the likelihood of cancer progression. Understanding the roles of environmental exposures and host susceptibilities in molecular pathways has implications for screening, treatment, surveillance, and prevention. (+info)