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Biomedical subjects

L Schmitt

Publications and source records attributed to L Schmitt.

At least 19 recordsLinked to original sources
PubMed2006

Heart rate variability and performance at two different altitudes in well-trained swimmers.

UNLABELLED: The aim of this study was to compare the effects of training at two different altitudes on heart rate variability (HRV) and performance in well-trained swimmers. Eight national-level male swimmers (age = 17.0 +/- 1.8 yrs, weight = 67.0 +/- 6.6 kg, height = 180.4 +/- 7.2 cm, V(O2max) = 60.4 +/- 4.0 ml.min(-1). kg(-1)) trained 17 days at 1200 m altitude (T1200), then, after 6 weeks of moderate training at sea level, reproduced the same training plan at 1850 m (T1850). The training was mainly aerobic with 86 % and 84 % < or = anaerobic threshold for T 1200 and T1850, respectively. Four HRV analysis tests were performed during T1200 and T1850, respectively (pre-test = day 0, test 2 = day 5, test 3 = day 11, post-test = day 17), in supine and standing position. Performance was measured over a 2000-m freestyle test at the altitude of 1200 m. A difference in HRV changes was observed between the two altitudes: during T1200, addition of parasympathetic and sympathetic activity in supine (TP(SU)) (p < 0.05) and standing (TP(ST)) (p < 0.05) position, supine parasympathetic activity (HF(SU)) (p < 0.05), and standing sympathetic activity (LF(ST)) (p < 0.05) were increased and the 2000-m performance was improved (p < 0.05) whereas none of these parameters was changed during T1850. Change in performance was correlated with increase in HF(SU) (r = 0.73; p < 0.05) and tended towards correlation with increase in LF(ST) (r = 0.73; p = 0.06). CONCLUSION: the same training loads induced a positive effect on HRV and performance at 1200 m but not at 1850 m. This may be the consequence of greater stress due to an interaction between greater hypoxic stimulus and the same training loads. These results highlight two opposing effects: aerobic training increases, whereas hypoxia decreases HF(SU), due to the correlation between HRV and changes in performance during altitude training.

Adolescent↗
PubMed2006

Is it more effective for highly trained swimmers to live and train at 1200 m than at 1850 m in terms of performance and haematological benefits?

OBJECTIVES: The effects of living and training have not been compared at different altitudes in well trained subjects. METHODS: Nine international swimmers lived and trained for 13 days similarly at 1200 m (T1200) and 1850 m (T1850). The two altitude training periods were separated by six weeks of sea level training. Before and after each training trip, subjects performed, at an altitude of 1200 m, an incremental exercise test to exhaustion of 5 x 200 m swims and a maximal test over 2000 m. RESULTS: There was no difference in Vo(2)max after each training trip: the before values were 58.5 (5.6) and 60.4 (6.7) ml/kg/min and the after values were 56.2 (5.2) and 57.1 (4.7) ml/kg/min for T1200 and T1850 respectively. The 2000 m performance had improved during T1200 (1476 (34) to 1448 (45) seconds) but not during T1850 (1458 (35) v 1450 (33) seconds). Mean cell volume increased during T1850 (86.6 (2.8) to 88.7 (2.9) microm(3)) but did not change during T1200 (85.6 (2.9) v 85.7 (2.9) microm(3)). The proportion of reticulocytes decreased during T1200 (15.2 (3.8)% to 10.3 (3.4)%) and increased during T1850 (9.3 (1.6)% to 11.9 (3.5)%). CONCLUSIONS: The short term effects of 13 days of training at 1200 m on swimming performance appear to be greater than the same type of training for the same length of time at 1850 m. As mean cell volume and proportion of reticulocytes only increased during training at 1850 m, the benefits of training at this altitude may be delayed and appear later on.

Adaptation, Physiological↗
PubMed2005

Molecular insights into the mechanism of ATP-hydrolysis by the NBD of the ABC-transporter HlyB.

The ABC-transporter HlyB is a central element of the Type I protein secretion machinery, dedicated to export the E. coli toxin HlyA in a single step across the two membranes of the cell envelope. Here, we discuss recent insights into the structure and the mechanism of ATP-hydrolysis by the NBD of HlyB. Combining structural and biochemical data, we have suggested that substrate-assisted catalysis (SAC), but not general base catalysis, is responsible for ATP-hydrolysis in this NBD and might also operate in other NBDs. Finally, the implications and advantages of SAC are discussed in the context of ATP-induced dimerization of the NBDs.

Adenosine Triphosphate↗
PubMed2005

Living high-training low altitude training: effects on mucosal immunity.

Secretory immunoglobulin A (sIgA) is the major immunoglobulin of the mucosal immune system. Whereas the suppressive effect of heavy training on mucosal immunity is well documented, little is known regarding the influence of hypoxia exposure on sIgA during altitude training. This investigation examined the impact of an 18-day Living high-training low (LHTL) training camp on sIgA levels in 11 (six females and five males) elite cross-country skiers. Subjects from the control group (n=5) trained and lived at 1,200 m of altitude, whereas, subjects from the LHTL group (n=6) trained at 1,200 m, but lived at a simulated altitude of 2,500, 3,000 and 3,500 m (3x6-day, 11 h day(-1)) in hypoxic rooms. Saliva samples were collected before, after each 6-day phases and 2 weeks thereafter (POST). Salivary sIgA, protein and cortisol were measured. There was a downward trend in sIgA concentrations over the study, which reached significance in LHTL (P<0.01), but not in control (P=0.08). Salivary IgA concentrations were still lower baseline at POST (P<0.05). Protein concentration increased in LHTL (P<0.05) and was negatively correlated with sIgA concentration after the 3,000 and 3,500 m-phase and at POST (P<0.05 all). Cortisol concentrations were unchanged over the study and no relationship was found between cortisol and sIgA. In summary, data were strongly suggestive of a cumulative negative effect of physical exercise and hypoxia on sIgA levels during LHTL training. Two weeks of active recovery did not allow for proper sIgA recovery. The mechanism underlying this depression of sIgA could be mediated by neural factors.

Adult↗
PubMed2005

A molecular understanding of the catalytic cycle of the nucleotide-binding domain of the ABC transporter HlyB.

The ABC transporter (ATP-binding-cassette transporter) HlyB (haemolysin B) is the central element of a type I secretion machinery, dedicated to the secretion of the toxin HlyA in Escherichia coli. In addition to the ABC transporter, two other indispensable elements are necessary for the secretion of the toxin across two membranes in a single step: the transenvelope protein HlyD and the outer membrane protein TolC. Despite the fact that the hydrolysis of ATP by HlyB fuels secretion of HlyA, the essential features of the underlying transport mechanism remain an enigma. Similar to all other ABC transporters, ranging from bacteria to man, HlyB is composed of two NBDs (nucleotide-binding domains) and two transmembrane domains. Here we summarize our detailed biochemical, biophysical and structural studies aimed at an understanding of the molecular principles of how ATP-hydrolysis is coupled to energy transduction, including the conformational changes occurring during the catalytic cycle, leading to substrate transport. We have obtained individual crystal structures for each single ground state of the catalytic cycle. From these and other biochemical and mutational studies, we shall provide a detailed molecular picture of the steps governing intramolecular communication and the utilization of chemical energy, due to ATP hydrolysis, in relation to resulting structural changes within the NBD. These data will be summarized in a general model to explain how these molecular machines achieve translocation of molecules across biological membranes.

Adenosine Triphosphate↗
PubMed2005

Specificity of VO2MAX and the ventilatory threshold in free swimming and cycle ergometry: comparison between triathletes and swimmers.

OBJECTIVES: To compare maximal heart rate (HRmax), maximal oxygen consumption (VO2MAX), and the ventilatory threshold (VT; %VO2MAX) during cycle ergometry and free swimming between swimmers and triathletes. METHODS: Nine swimmers and ten triathletes completed an incremental swimming and cycling test to exhaustion. Whole body metabolic responses were determined in each test. RESULTS: The swimmers exhibited a significantly higher VO2MAX in swimming than in cycling (58.4 (5.6) v 51.3 (5.1) ml/kg/min), whereas the opposite was found in the triathletes (53.0 (6.7) v 68.2 (6.8) ml/kg/min). HRmax was significantly different in the maximal cycling and swimming tests for the triathletes (188.6 (7.5) v 174.8 (9.0) beats/min). In the maximal swimming test, HRmax was significantly higher in the swimmers than in the triathletes (174.8 (9.0) v 184.6 (9.7) beats/min). No significant differences were found for VT measured in swimming and cycling in the triathletes and swimmers. CONCLUSION: This study confirms that the exercise testing mode affects the VO2MAX value, and that swimmers have very specific training adaptations even compared with triathletes. This may be a function of acute physiological responses combined with the specialist training status of the different athletes influencing maximal cardiac output or oxygen extraction. In contrast, the different training regimens do not seem to influence the VT, as this variable did not differ between the two testing modes in either group.

Adolescent↗
PubMed2003

[Depressive symptoms in Alzheimer's disease: preliminary results of the REAL.FR study].

UNLABELLED: The Alzheimer's disease (AD) is today regarded as a degenerative pathology with a serious and common complication: occurrence of mental and behavioral disturbances. Among this neuropsychiatrics symptoms, the depressive symptoms occupy a significant place by their frequency and their consequences on the caregiver's burden. The prevalence of such disorders is very variously appreciated in the literature. OBJECTIVE: To assess with precision depressive symptoms in a population with Alzheimer's disease rated on neuropsychiatric inventory NPI. METHOD: Cross-sectional study of patients with AD presenting at the consultation of psycho-geriatic, geriatric or neurologic services in 16 french university hospitals. The frequency of the depression was evaluated with the NPI on a population of 578 subjects with AD. We studied the association existing between these symptoms and the antecedents of depression and we studied the gravity of these disorders according to the cognitive status. RESULTS: Caregivers describe less one depressive symptom for approximately 40% of the subjects included in the study n = 229. The average score of gravity is close to 4 and is thus clinically significant. More the stage of dementia is severe more the number of subjects presenting a clinically significant score is important. Scores of depression evolve parallel to the stage of dementia. The antecedents of depression are a risk factor for depressive symptoms in the AD p < 0.001. DISCUSSION: These results confirm those of primary studies. In our study, more than the prevalence of depressive symptoms it seems that is the severity of the disorder which is associated with the dementia severity. The continuation of this work will allow a prospective evaluation of depressive symptoms in the AD.

Aged↗
PubMed2003

Quality assessment of anticoagulation dose management: comparative evaluation of measures of time-in-therapeutic range.

BACKGROUND: The results of clinical trials often hinge on the quality of oral anticoagulation management, yet the quality of such management is frequently not mentioned or measured. Time-in-therapeutic range (TTR) is one measure of quality of anticoagulation dose management, but various methodologies exist for measuring TTR. OBJECTIVE: This study was initiated to compare three commonly used methodologies for measuring TTR to see how they compare within the same cohort of patients. PATIENTS/METHODS: Three common methodologies of calculating time-in-therapeutic range were analyzed retrospectively in a cohort of patients over six two-month intervals. Additional analysis was performed for three and six-month intervals. The methodologies included fraction of INRs in range; cross-section of the files; and linear interpolation. RESULTS: Fraction of the INRs in range and cross-section of the files methodologies gave similar results, while linear interpolation yielded significantly shorter time-in-range for the two-month, three-month, and six-month intervals measured. The advantages and disadvantages of each methodology are discussed. CONCLUSIONS: The decision of which method to use should be based on clinic size, information desired, and clinic resources for ease of applying either of the methods in clinical practice. Each of these methodologies has their limitations and the question remains as to which method best reflects the quality of anticoagulation management. Regardless of these limitations, investigators are urged to employ at least one method of measuring the quality of oral anticoagulation management so as to better assess the validity of the clinical outcomes.

Adult↗
PubMed2002

[Self-poisoning with Datura stramonium. 3 case reports].

BACKGROUND: Datura stramonium is a hallucinogenic plant that causes serious poisoning. Due to its easy availability and strong anticholinergic properties, substance users and teens may use Datura stramonium as a drug. Consumption of any part of the plant can result in severe toxicity. CASE REPORTS: 3 cases of acute self-poisoning by ingestion of Datura stramonium are reported. The patients presented with a typical anticholinergic syndrome: agitation, confusion, hallucinations and combative behaviour; all of them had mydriasis, but dry mouth and tachycardia were less common. All these 3 subjects had a good prognosis but have required hospitalisation because of severe psychiatric derangement with agitated behaviour. The patients were favourably managed with only symptomatic treatment. DISCUSSION: This article reviews the clinical syndrome associated with the toxicity. The severity of hallucinations and confusion, associated with pupillary dilation, flushing, dry mouth, and tachycardia, are related with Datura intoxication. Symptomatic treatment is efficient. CONCLUSION: Primary care physicians might be informed about the abuse of Datura stramonium, often associated with substance misuse, and the need to educate risk-patients.

Adult↗
PubMed2001

Deleted in Malignant Brain Tumors 1 is a versatile mucin-like molecule likely to play a differential role in digestive tract cancer.

Deleted in Malignant Brain Tumors 1 (DMBT1) has been proposed as a candidate tumor suppressor gene for brain, lung, and digestive tract cancer. In particular, alterations of the gene and/or a loss of expression have been observed in gastric, colorectal, and esophageal carcinomas. Initial evidence has accumulated that DMBT1 may represent a multifunctional protein. Because the consequences of a loss of DMBT1 function may be different depending on its original function in a particular tissue, we wondered if it is appropriate to assume a uniform role for DMBT1 in digestive tract carcinomas. We hypothesized that a systematic characterization of DMBT1 in the human alimentary tract would be useful to improve the understanding of this molecule and its role in digestive tract carcinomas. Our data indicate that the expression pattern and subcellular distribution of DMBT1 in the human alimentary tract is reminiscent of epithelial mucins. Bovine gallbladder mucin is identified as the DMBT1 homologue in cattle. An elaborate alternative splicing may generate a great variety of DMBT1 isoforms. Monolayered epithelia display transcripts of 6 kb and larger, and generally show a lumenal secretion of DMBT1 indicating a role in mucosal protection. The esophagus is the only tissue displaying an additional smaller transcript of approximately 5 kb. The stratified squamous epithelium of the esophagus is the only epithelium showing a constitutive targeting of DMBT1 to the extracellular matrix (ECM) suggestive of a role in epithelial differentiation. Squamous cell carcinomas of the esophagus show an early loss of DMBT1 expression. In contrast, adenocarcinomas of the esophagus commonly maintain higher DMBT1 expression levels. However, presumably subsequent to a transition from the lumenal secretion to a targeting to the ECM, a loss of DMBT1 expression also takes place in adenocarcinomas. Regarding DMBT1 as a mucin-like molecule is a new perspective that is instructive for its functions and its role in cancer. We conclude that DMBT1 is likely to play a differential role in the genesis of digestive tract carcinomas. However, although DMBT1 originally has divergent functions in monolayered and multilayered epithelia, carcinogenesis possibly converges in a common pathway that requires an inactivation of its functions in the ECM.

Adenocarcinoma↗
PubMed2001

Effects of acute progesterone administration in healthy postmenopausal women and normally-cycling women.

The goal of this study was to investigate the behavioral and subjective effects of single doses of progesterone (intramuscular) in post-menopausal women and in women with normal menstrual cycles. Although certain metabolites of progesterone (e.g., allopregnanolone) are known to bind to GABA(A) receptors and produce sedative-like effects in laboratory animals, few studies have examined the acute effects of these neurosteroids in humans. Postmenopausal women (N=10) received progesterone (25, 50, 100 mg im) or placebo at weekly intervals, and women with normal menstrual cycles (N=8) received progesterone (100 mg im) or placebo once a month during the early follicular phase. Dependent measures included plasma levels of progesterone and allopregnanolone, self-report measures of mood and subjective effects and psychomotor performance. Plasma concentrations of progesterone and allopregnanolone increased in a time and dose-dependent manner, with relatively little variability. The concentrations were similar in both groups, although the ratio of allopregnanolone to progesterone was higher in cycling women at certain time points. Contrary to expectations, progesterone produced only modest behavioral or subjective effects. In the cycling women, it produced mild sedative-like effects (i.e., decreases in ratings of Vigor and Friendliness). In the post-menopausal women, only the highest dose (100 mg) slightly increased ratings of feeling "sluggish". These results suggest that progesterone and its metabolites, at concentrations well beyond those attained during the normal menstrual cycle, produce only marginal sedative-like effects. These findings suggest that brief (i.e., several hours) increases in plasma levels of allopregnanolone do not have direct effects on mood.

Affect↗
PubMed2001

Disability and quality of life in Charcot-Marie-Tooth disease type 1.

OBJECTIVES: Charcot-Marie-Tooth disease type I (CMT1) is a hereditary sensorimotor neuropathy causing variable degrees of handicap. The risk for relevant disability in respect to genetic counselling is unknown. An attempt was made to define it. METHODS: Disability and ambulation of 50 patients with CMT1 were scored by the Hauser ambulation index score and the Rankin scale. Rankin score 2 was subdivided into 2a (independent without relevant slowness) and 2b (independent, though at the cost of excessive time consumption). The sickness impact profile was assessed and compared with patients 6 months after stroke who were without mental deficit. To define at which degree sickness and disability become relevant for genetic counselling, the patients were asked whether they would refrain from childbearing if the children were at risk of inheriting a disease that caused as much disability as they experienced themselves. RESULTS: Subdivision of Rankin score 2 was reliable and improved validity. High disability significantly predicted an attitude against childbearing (stepwise logistic regression) only with this subdivision. Thirty six per cent of the patients voted against childbearing. The cut off for relevant disability in respect to childbearing was a Rankin score higher than 2a, which was present in 44% of the patients. Psychosocial impact was comparable with patients with stroke and similar disability. Depression was present in 18% of the patients. CONCLUSION: Subdivision of Rankin score 2 is recommended for the assessment of longstanding disability in neuromuscular disorders. Disability becomes relevant for the attitude towards childbearing as soon as everyday activities become markedly slow (Rankin score 2b). Relevant disability occurred in 44% of the patients. Emotional stress in CMT is similar to that of patients with stroke and comparable disability.

Adolescent↗
PubMed2001

Peritraumatic dissociation, acute stress, and early posttraumatic stress disorder in victims of general crime.

OBJECTIVE: To compare the relation between peritraumatic dissociation and acute stress and the early development of posttraumatic stress disorder (PTSD) in victims of general crime. METHOD: A total of 48 subjects were assessed within 24 hours of the trauma, using the Peritraumatic Dissociative Experiences Questionnaire Self-Report Version (PDEQ-SRV). They were followed longitudinally to assess acute stress (2 weeks after the assault,) using the Standford Acute Stress Reaction Questionnaire (SASRQ), and posttraumatic stress (at 5 weeks), using the Clinician-Administered PTSD Scale (CAPS) and the Impact of Event Scale (IES). RESULTS: Among PTSD subjects mean PDEQ scores were significantly higher (mean 3, SD 0.9) than in those without PTSD (mean 2.3, SD 0.7) (t = 2.78, df 46, P = 0.007). Among PTSD subjects, mean SASRQ scores were significantly higher (mean 97.9, SD 29.2) than in those without PTSD (mean 54.8, SD 28.2) (t = 4.9, df 46, P = 0.00007). CONCLUSIONS: High levels of peritraumatic dissociation and acute stress following violent assault are risk factors for early PTSD. Identifying acute reexperiencing can help the clinician identify subjects at highest risk.

Acute Disease↗
PubMed2001

[Victims of general crimes. Prospective and longitudinal assessment of psychological injuries].

OBJECTIVE: The aim of this study was to assess the relations between acute psychological injury, particularly peritraumatic dissociation, and early development of posttraumatic stress disorder in victims of violence. METHODS: Thirty-five subjects were prospectively assessed in an emergency department, within 24 hours of the trauma, for acute dissociative experiences with the Peritraumatic Dissociative Experiences Questionnaire (PDEQ). All of them were followed longitudinally to assess post traumatic stress disorder (PTSD) 5 weeks after with the Clinician-administered PTSD scale (CAPS) and the Impact of event scale (IES). RESULTS: Of the 35 victims 10 (28%) were diagnosed with a posttraumatic stress disorder at 5 weeks. Among PTSD subjects mean PDEQ scores were significantly higher (3+/-1.1) than in those without PTSD (2.3+/-0.7) (t=2.24, df=33, p=0.029). The PTSD subjects reported more "out of body experience" (p=0.015) and more "sense of body distorsion" (p=0.03) than non PTSD subjects. CONCLUSION: High levels of peritraumatic dissociation following violent assault are risk factors for early posttraumatic stress disorder. Psychological assessment of acute traumatic dissociative experiences must be included in emergency departments.

Adolescent↗