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Biomedical subjects

C Denis

Publications and source records attributed to C Denis.

At least 19 recordsLinked to original sources
PubMed2006

Evidence of decrease in peak heart rate in acute hypoxia: effect of exercise-induced arterial hypoxemia.

This study focuses on the influence of the arterial oxygen saturation level at exhaustion on peak heart rate under acute moderate hypoxia, in endurance-trained subjects. Nineteen competing male cyclists performed exhaustive ramp exercise (cycle ergometer) under normoxia and normobaric hypoxia (15 % O (2)). After the normoxic trial, the subjects were divided into those demonstrating exercise-induced arterial hypoxemia during exercise (> 5 % decrease in SaO (2) between rest and the end of exercise, n = 10) and those who did not (n = 9). O (2) uptake, heart rate and arterial O (2) saturation (ear-oximeter) levels were measured. Under hypoxia, peak heart rate decreased for both groups (p < 0.001) and to a greater extent for hypoxemic subjects (p < 0.01). Arterial O (2) saturation under hypoxia was lower for the hypoxemic than for the non-hypoxemic subjects (p < 0.001) and it was correlated to the fall in peak heart rate between normoxia and hypoxia for all subjects (p < 0.01; r = 0.65). Hypoxemic subjects presented greater decrease in maximal O (2) uptake than non-hypoxemic ones (19.6 vs. 15.6 %; p < 0.05). The results confirm the greater decrement in arterial O (2) saturation under hypoxia in hypoxemic subjects and demonstrates a more pronounced reduction in peak heart rate in those subjects compared with non-hypoxemic ones. These data confirm the possible influence of arterial oxygenation on the decrease in peak heart rate in acute hypoxia.

Adult↗
PubMed2006

Pharmacological interventions for benzodiazepine mono-dependence management in outpatient settings.

BACKGROUND: The improved safety profile of benzodiazepines compared to barbiturates has contributed to a high rate of prescription since the seventies. Although benzodiazepines are highly effective for some disorders, they are potentially addictive drugs and they can provide reinforcement in some individuals. OBJECTIVES: To evaluate the effectiveness of pharmacological interventions for benzodiazepine mono-dependence. SEARCH STRATEGY: We searched the Cochrane Drugs and Alcohol Group' Register of Trials (October 2004), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2004), MEDLINE (January 1966 to October 2004), EMBASE (January 1988 to October 2004), PsycInfo (1985 to October 2004), CINAHL (1982 to October 2004), Pascal, Toxibase, reference lists of articles. SELECTION CRITERIA: Randomized trials of benzodiazepines dependence management regardless of type, dose (daily and total) and duration of benzodiazepine treatment. DATA COLLECTION AND ANALYSIS: Reviewers independently assessed trials for inclusion, rated their methodological quality and extracted data. MAIN RESULTS: Eight trials involving 458 participants were included. The studies included could not be analysed cumulatively because of heterogeneity of inteventions and participants' characteristics. Results support the policy of gradual rather than abrupt withdrawal of benzodiazepine. Progressive withdrawal (over 10 weeks) appeared preferable if compared to abrupt since the number of drop-outs was less important and the procedure judged more favourable by the participants. Short half-life benzodiazepine, associated with higher drop-out rates, did not have higher withdrawal symptoms scores. Switching from short half-life benzodiazepine to long half-life benzodiazepine before gradual taper withdrawal did not receive much support from this review. The role of propanolol in benzodiazepine withdrawal was unclear; adding tricyclic antidepressant (dothiepin) decreased the intensity of withdrawal symptoms but did not increase the rate of benzodiazepine abstinence at the end of the trial. Buspirone and Progesterone failed to suppress any benzodiazepine symptoms. Carbamazepine might have promise as an adjunctive medication for benzodiazepine withdrawal, particularly in patients receiving benzodiazepines in daily dosages of 20 mg/d or more of diazepam (or equivalents). AUTHORS' CONCLUSIONS: The results of this systematic review point to the potential value of carbamazepine as an effective intervention for benzodiazepine gradual taper discontinuation. Carbamazepine has shown rather modest benefit in reducing withdrawal severity, although it did significantly improve drug-free outcome. Larger controlled studies are needed to confirm these benefits, to assess adverse effects and to identify when its clinical use might be most indicated. Other suggested treatment approaches to benzodiazepine discontinuation management should be explored (antidepressants, benzodiazepine receptors modulator).

Ambulatory Care↗
PubMed2006

Psychotherapeutic interventions for cannabis abuse and/or dependence in outpatient settings.

BACKGROUND: Cannabis use disorder is the most common illicit substance use disorder in general population. Despite that, only a minority seek assistance from a health professional, but the demand for treatment is now increasing internationally. Trials of treatment have been published but to our knowledge, there is no published systematic review . OBJECTIVES: To evaluate the efficacy of psychosocial interventions for cannabis abuse or dependence. SEARCH STRATEGY: We searched the Cochrane Central Register of Trials (CENTRAL) The Cochrane Library Issue 3, 2004; MEDLINE (January 1966 to August 2004), PsycInfo (1985 to October 2004), CINAHL (1982 to October 2004), Toxibase (until September 2004) and reference lists of articles. We also contacted researchers in the field. SELECTION CRITERIA: All randomized controlled studies examining a psychotherapeutic intervention for cannabis dependence or abuse in comparison with a delayed-treatment control group or combinations of psychotherapeutic interventions. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial quality and extracted data MAIN RESULTS: Six trials involving 1297 people were included. Five studies took place in the United States, one in Australia. Studies were not pooled in meta-analysis because of heterogeneity. The six included studies suggested that counseling approaches might have beneficial effects for the treatment of cannabis dependence. Group and individual sessions of cognitive behavioral therapy (CBT) had both efficacy for the treatment of cannabis dependence and associated problems, CBT produced better outcomes than a brief intervention when CBT was delivered in individual sessions. Two studies suggested that adding voucher-based incentives may enhance treatment when used in combination with other effective psychotherapeutic interventions. Abstinence rates were relatively small overall but favored the individual CBT 9-session (or more) condition. All included trials reported a statistically significant reductions in frequency of cannabis use and dependence symptoms. But other measures of problems related to cannabis use were not consistently different. AUTHORS' CONCLUSIONS: The included studies were too heterogenous and could not allow to draw up a clear conclusion. The studies comparing different therapeutic modalities raise important questions about the duration, intensity and type of treatment. The generalizability of findings is also unknown because the studies have been conducted in a limited number of localities with fairly homogenous samples of treatment seekers. However, the low abstinence rate indicated that cannabis dependence is not easily treated by psychotherapies in outpatient settings.

Ambulatory Care↗
PubMed2006

Comparison of muscle mechanical and histochemical properties between young and elderly subjects.

We examined age-related human muscle fiber changes and their relation with maximal power scaled to muscle volume (specific power). Fiber type distribution and cross sectional area (CSA) were determined from m. vastus lateralis in 7 young (YS; 29.6 +/- 5 years) and 7 elderly subjects (ES; 74.3 +/- 3 years). Muscle volume and mean CSA of the thigh were anthropometrically measured. Muscle power was assessed by a series of accelerations on a cycle ergometer. Specific power was 35 % lower in ES than YS. Area ratios of IIa/I and IIx/I fibers were lower in ES than YS. By including single fiber power data from the literature to the present results, the decline in the specific power between YS and ES was 34 %, when data of both IIa and IIx fibers were considered. The decrease of the specific power with age on the whole muscle would be compatible with the age-induced changes in the muscle histochemical characteristics.

Adult↗
PubMed2006

Effects of training on lactate kinetics parameters and their influence on short high-intensity exercise performance.

The purpose of the present study was to relate the training-induced alterations in lactate kinetics parameters to the concomitant changes in time to exhaustion (T(lim)) at a work rate corresponding to maximal oxygen uptake (Pa(peak)). Eight subjects performed before and after training i) an incremental exercise up to exhaustion to determine Pa(peak), ii) a 5-min 90 % Pa(peak) exercise followed by a 90-min passive recovery to determine an individual blood lactate recovery curve fitted to the bi-exponential time function: La(t) = La(0) + A1(1 - e -gamma1 x t) + A2(1 - e -gamma2 x t), and iii) a time to exhaustion at Pa peak to determine T lim. A biopsy of the vastus lateralis muscle was made before and after training. The training programme consisted in pedalling on a cycle ergometer 2 h a day, 6 days a week, for 4 weeks. Training-induced increases (p < 0.05) in Pa(peak), muscle capillary density, citrate synthase activity, gamma2 that denotes the lactate removal ability (from 0.0547 +/- 0.0038 to 0.0822 +/- 0.0071 min (-1)) and T(lim) (from 299 +/- 23 to 486 +/- 63 s), decreases (p < 0.05) in activities of lactate dehydrogenase (LDH) and muscle type of LDH, the phosphofructokinase/citrate synthase activities ratio and the estimated net amount of lactate released (NALR) during exercise recovery (from 66.5 +/- 8.6 to 47.2 +/- 11.1 mmol) were also observed. The improvement of T (lim) with training was related to the increase in gamma2 (r = 0.74, p = 0.0367) and to the decrease in NALR (r = 0.77, p = 0.0250). These results suggest that the post-training greater ability to remove lactate from the organism and reduced muscle lactate accumulation during exercise account for the concomitant improvement of the time to exhaustion during high-intensity exercise performed at the same relative work rate.

Adult↗
PubMed2006

Heat resistance of coliform species isolated from cooked ham, snail flesh, and 'bouchées à la reine'.

AIMS: In this study, the heat resistance of coliform species isolated from cooked ham and ready-made meals was determined. METHODS AND RESULTS: Thirteen coliform strains belonging to 12 different species were studied using laboratory medium in order to determine delta (first decimal reduction time) and z(T) values (temperature increase leading to a 10-fold reduction of delta) using the Weibull model. For seven strains, delta-values were determined at temperatures ranging from 55 to 60 degrees C, with, delta values between 0.52 and 2.98 min, at 59 degrees C. For the other six strains, lower temperature values were determined with delta-values ranging from 0.47 to 1.64 min at 54 degrees C. z(T) values calculated for the 13 strains were 3.1 to 7.5 degrees C. For eight strains, plotting of the log of survivors was not linear but rather showed shoulders or shoulders and tails. CONCLUSIONS: Coliform species were sensitive to heat treatment with a decimal reduction time under 2 min at 60 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: The better knowledge of coliform heat resistance by determining thermal resistance parameters with confidence intervals will be useful for evaluating the efficiency of industrial thermal processes.

Animals↗
PubMed2006

Effect of endurance training on muscle microvascular filtration capacity and vascular bed morphometry in the elderly.

AIM: Exercise training is a strong stimulus for vascular remodelling and could restore age-induced vascular alterations. The purpose of the study was to test the hypothesis that an increase in vascular bed filtration capacity would corroborate microvascular adaptation with training. METHODS: We quantified (1) microvascularization from vastus lateralis muscle biopsy to measure the capillary to fibre interface (LC/PF) and (2) the microvascular filtration capacity (K(f)) in lower limbs through a venous congestion plethysmography procedure. Twelve healthy older subjects (74 +/- 4 years) were submitted to a 14-week training programme during which lower-limbs were trained for endurance exercise. RESULTS: The training programme induced a significant increase in the aerobic exercise capacity of lower limbs (+11% V(O2peak); P < 0.05; +28% Citrate Synthase Activity; P < 0.01). K(f) was largely increased (4.3 +/- 0.9 10(-3) mL min(-1) mmHg(-1) 100 mL(-1) post-training vs. 2.4 +/- 0.8 pre-training, mean +/- SD; P < 0.05) and microvascularization developed as shown by the rise in LC/PF (0.29 +/- 0.06 post- vs. 0.23 +/- 0.06 pre-training; P < 0.05). Furthermore, K(f) and LC/PF were correlated (r = 0.65, P < 0.05). CONCLUSION: These results demonstrated the microvascular adaptation to endurance training in the elderly. The increase in K(f) with endurance training was probably related to a greater surface of exchange with an increased microvessel/fibre interface area. We conclude that measurement of the microvascular filtration rate reflects the change in the muscle exchange area and is influenced by exercise training.

Aged↗
PubMed2005

A high blood lactate induced by heavy exercise does not affect the increase in submaximal VO2 with hyperoxia.

Few studies evidenced an enhancement in oxygen uptake (VO2) during submaximal exercise in hyperoxia. This O2 "overconsumption" seems to increase above the lactate threshold. The aim of this study was to determine whether the hyperoxia-induced enhancement in VO2 may be related to a higher metabolism of lactate. Nine healthy males (aged 23.1 years, mean VO2 max= 53.8 ml min-1 kg-1) were randomized to two series of exercise in either normoxia or hyperoxia corresponding to an inspired O2 fraction (FIO2) of 30%. Each series consisted of 6 min cycling at 50% VO2 max (Moderate1), 5 min cycling at 95%VO2 max (Near Max) and then 6 min at 50% VO2 max (Moderate2). In both series Near Max was performed in normoxia. VO2 was significantly greater under hyperoxia than in normoxia during Moderate1 (2192 +/- 189 vs. 2025 +/- 172 ml min-1) and during Moderate2 (2352 +/- 173 vs. 2180+ /- 193 ml min-1). However, the effect of the high FIO2 was not significantly different on VO2Moderate2 (+172+/-137 ml min-1 with [La] approximately 6 mmol l-1) compared to VO2Moderate1 (+166 +/- 133 ml min-1 with [La] approximately 2.4 mmol l-1). [La] at the onset of Moderate2 was not different between normoxia and hyperoxia (10.1 +/- 2.2 vs. 10.9 +/- 1.6 mmol l-1). The results show that VO2 is significantly increased during moderate exercise in hyperoxia. But this O2 overconsumption was not modified by a high [La] induced by a prior heavy exercise. It could be concluded that lactate accumulation is not directly responsible for the increase in O2 overconsumption with intensity during exercise in hyperoxia.

Adaptation, Physiological↗
PubMed2003

Enhancement of microvessel tortuosity in the vastus lateralis muscle of old men in response to endurance training.

Muscle microvascularization is usually quantified in transverse sections, in absolute terms (capillaries around fibres, CAF, or capillary-to-fibre ratio, C/F) or as CAF related to fibre area (CAF/area, CAFA). The capillary-to-fibre perimeter exchange ratio (CFPE) has been introduced in order to assess the role of the capillary-to-fibre interface in resistance to O(2) diffusion. The ratio between the length of capillaries in contact with fibres and fibre perimeter (LC/PF) has also been used as an index for capillary tortuosity. The possibility of change in capillary tortuosity with endurance training was not considered in previous studies. Consequently, this study investigated the effect of 14 weeks of endurance training on muscle microvascularization, including microvessel tortuosity, in 11 elderly men (8th decade). Microvessels were analysed using the CD31 antibody. Together with the significant increase in peak oxygen exchange and citrate synthase activity, there was a significant increase in C/F. While CFPE and CAFA remained unchanged, an important finding was the clear increase in LC/PF (56%; P < 0.001) for a same sarcomere length. We also found a strong correlation between oxidative enzyme activity and LC/PF both before and after training. These results indicate that endurance training induces significant remodelling in the microvessel network in elderly men and that an increase in the degree of microvessel tortuosity would be an important mechanism of adaptation to endurance training.

Aged↗
PubMed2002

Effects of moderate hyperoxia on oxygen consumption during submaximal and maximal exercise.

The present study examined the effect of hyperoxia on oxygen uptake (VO(2)) and on maximal oxygen uptake (VO(2max)) during incremental exercise (IE) and constant work rate exercise (CWRE). Ten subjects performed IE on a bicycle ergometer under normoxic and hyperoxic conditions (30% oxygen). They also performed four 12-min bouts of CWRE at 40, 55, 70 and 85% of normoxic VO(2max) (ex1, ex2, ex3 and ex4, respectively) in normoxia and in hyperoxia. VO(2max) was significantly improved by 15.0 (15.2)% under hyperoxia, while performance (maximum workload, W(max)) was improved by only +4.5 (3.0)%. During IE, the slope of the linear regression relating VO(2) to work rate was significantly steeper in hyperoxia than in normoxia [10.80 (0.88) vs 10.06 (0.66) ml x min(-1) x W(-1)]. During CWRE, we found a higher VO(2) at ex1, ex2, ex3 and ex4, and a higher VO(2) slow component at ex4 under hyperoxia. We have shown that breathing hyperoxic gas increases VO(2max), but to an extent that is difficult to explain by an increase in oxygen supply alone. Changes in metabolic response, fibre type recruitment and VO(2) of non-exercising tissue could explain the additional VO(2) for a given submaximal work rate under hyperoxia.

Adult↗
PubMed2002

Molecular adaptations of neuromuscular disease-associated proteins in response to eccentric exercise in human skeletal muscle.

The molecular events by which eccentric muscle contractions induce muscle damage and remodelling remain largely unknown. We assessed whether eccentric exercise modulates the expression of proteinases (calpains 1, 2 and 3, proteasome, cathepsin B+L), muscle structural proteins (alpha-sarcoglycan and desmin), and the expression of the heat shock proteins Hsp27 and alphaB-crystallin. Vastus lateralis muscle biopsies from twelve healthy male volunteers were obtained before, immediately after, and 1 and 14 days after a 30 min downhill treadmill running exercise. Eccentric exercise induced muscle damage as evidenced by the analysis of muscle pain and weakness, creatine kinase serum activity, myoglobinaemia and ultrastructural analysis of muscle biopsies. The calpain 3 mRNA level was decreased immediately after exercise whereas calpain 2 mRNA level was increased at day 1. Both mRNA levels returned to control values by day 14. By contrast, cathepsin B+L and proteasome enzyme activities were increased at day 14. The alpha-sarcoglycan protein level was decreased immediately after exercise and at day 1, whereas the desmin level peaked at day 14. alphaB-crystallin and Hsp27 protein levels were increased at days 1 and 14. Our results suggest that the differential expression of calpain 2 and 3 mRNA levels may be important in the process of exercise-induced muscle damage, whereas expression of alpha-sarcoglycan, desmin, alphaB-crystallin and Hsp27 may be essentially involved in the subsequent remodelling of myofibrillar structure. This remodelling response may limit the extent of muscle damage upon a subsequent mechanical stress.

Actins↗
PubMed2002

Time to exhaustion at VO(2)max is related to the lactate exchange and removal abilities.

The aim of the present study was to investigate the relationships between lactate exchange and removal abilities and the capacity to prolong exercise, as assessed by the time to exhaustion (Tlim) at a work rate corresponding to VO(2)max (Pa max ). The individual blood lactate recovery curves obtained for 13 untrained subjects after 5 min 90 % Pa max exercise were fitted to the biexponential time function: La(t) = La(0) + A(1) (1-e (-gamma(1) x t) + A(2) (1-e (-gamma(2) x t), where t is time into the recovery, La(0) is the arterialized lactate concentration measured at the end of the exercise, gamma(1) and gamma(2) are velocity constants denoting the lactate exchange and removal abilities, respectively. Tlim was positively related to gamma(1) and gamma(2) (r = 0.60, p < 0.05 and r = 0.56, p < 0.05, respectively) but was negatively related to La(0) (r = 0.75, p < 0.01). gamma()1 was positively related to the capillary density (r = 0.69, p < 0.01) and to the number of capillaries per type I fiber area (r = 0.62, p < 0.05). It was concluded that 1) high lactate exchange and removal abilities would allow continuing a high-intensity exercise for a longer duration, and 2) a high capillary density may explain the associated high lactate exchange ability.

Adult↗
PubMed2002

Serum pentosidine as an indicator of Alzheimer's disease.

Pentosidine, an advanced glycation end product (AGE), was assayed by HPLC in serum proteins from patients with Alzheimer type dementia (AD), patients with diabetes mellitus (D), and healthy (C) age-matched old subjects (mean age from each group = 84 years). Serum pentosidine was significantly different between the three groups despite similar renal function (serum creatinine < 160 micromol/L). In all groups of patients, pentosidine was independent of glycated hemoglobin (HbA1C) and the early glycation marker fructosamine and appeared to be an independent marker, mainly bound to serum albumin. Pentosidine could be an important factor useful for the diagnosis of Alzheimer's disease.

Aged↗
PubMed2002

[Rupture of ascending aortic aneurysm revealing Takayasu's arteritis].

Takayasu's disease is rare in Western countries. It is most often revealed by stenosing lesions, aneurysmal attacks being less frequent, generally multifocal, and associated with stenoses. An isolated aneurysmal attack of the ascending aorta is exceptional. It is a deleterious factor in the disease process, and one of the causes of death in this disease. We report a case of isolated aneurysm of the ascending aorta extending to the aortic arch, undergoing emergency surgery at the rupture phase, revealing Takayasu's arteritis. Classically, isolated, asymptomatic, small aneurysms without lesions of other branches are slow to evolve with prolonged corticosteroid therapy. Our observation was contrary to these data, with rapid growth in a major inflammatory context, and rupture. It would seem important to rapidly diagnose and treat Takayasu's disease aneurysms of the ascending aorta, given their progressive potential. In a young female the signs of parietal thickening of the aneurysm must provoke diagnosis and treatment rapidly.

Aneurysm, Ruptured↗
PubMed2001

Blood lactate exchange and removal abilities after relative high-intensity exercise: effects of training in normoxia and hypoxia.

The effects of 4 weeks of endurance training in conditions of normoxia or hypoxia on muscle characteristics and blood lactate responses after a 5-min constant-load exercise (CLE) at 90% of the power corresponding to the maximal oxygen uptake were examined at sea-level in 13 sedentary subjects. Five subjects trained in normobaric hypoxia (HT group, fraction of oxygen in inspired gas = 13.2%), and eight subjects trained in normoxia at the same relative work rates (NT group). The blood lactate recovery curves from the CLE were fitted to a biexponential time function: La(t) = La(0) + A1(1 - e- gamma 1.t) + A2(1 - e- gamma 2.t), where the velocity constants gamma 1 and gamma 2 denote the lactate exchange and removal abilities, respectively, A1 and A2 are concentration parameters that describe the amplitudes of concentration variations in the space represented by the arterial blood, La(t) is the lactate concentration at time t, and La(0) is the lactate concentration at the beginning of recovery from CLE. Before training, the two groups displayed the same muscle characteristics, blood lactate kinetics after CLE, and gamma 1 and gamma 2 values. Training modified their muscle characteristics, blood lactate kinetics and the parameters of the fits in the same direction, and proportions among the HT and the NT subjects. Endurance training increased significantly the capillary density (by 31%), citrate synthase activity (by 48%) and H isozyme proportion of lactate dehydrogenase (by 24%), and gamma 1 (by 68%) and gamma 2 (by 47%) values. It was concluded that (1) endurance training improves the lactate exchange and removal abilities estimated during recovery from exercises performed at the same relative work rate, and (2) training in normobaric hypoxia results in similar effects on lactate exchange and removal abilities to training in normoxia performed at the same relative work rates. These results, which were obtained non-invasively in vivo in humans during recovery from CLE, are comparable to those obtained in vitro or by invasive methods during exercise and subsequent recovery.

Adult↗
PubMed2001

Validation of a new ergometer adapted to all types of manual wheelchair.

Research concerning the physiological and biomechanical parameters of wheelchair propulsion requires the use of an accurate and reproducible protocol. Although some research comparing different ergometers has been conducted, it is not easy to fulfil the requirements of the realistic simulation of propulsion together with the careful analysis of metabolic and biomechanical parameters of performance. The VP100H ergometer has been validated for this purpose by comparing the values of power output (W) and force exerted to accelerate the wheels (F) with the same measures obtained using a two-dimensional force transducer (platform). The reproducibility of the power was verified during a test re-test procedure. Ten sportsmen performed an incremental exercise. Maximal aerobic power (Waer,max), maximum oxygen uptake (VO2max), maximum heart rate (fcmax), % Waer,max/%VO2max relationship (aV) and %Waer,max/%fcmax relationship (aH) were calculated. Results indicated no significant differences (P > 0.05) in VP100H versus platform measurements for F and W. Errors of measured Fand W ranged from 0.89% to 7.56% and from 0.41% to 6.74%, respectively, depending upon the trunk muscles that participate in the propulsion. This corresponded to a maximum error of 4.9 W for W. No significant differences (P > 0.05) were observed during the test re-test procedure for Waer,max, VO2max, fcmax, aH and aV. The coefficient of variation of these values ranged from 1.4 to 9.5, and the correlation coefficient from 0.68 to 0.98. We conclude that the VP100H is valid for measuring W, and F, and that these values are reproducible (when tested 10 days later).

Adult↗