Claude Jeandel

Effects of physical and sporting activities on balance control in elderly people.

OBJECTIVE: Balance disorders increase with aging and raise the risk of accidental falls in the elderly. It has been suggested that the practice of physical and sporting activities (PSA) efficiently counteracts these age related disorders, reducing the risk of falling significantly. METHODS: This study, principally based on a period during which the subjects were engaged in PSA, included 65 healthy subjects, aged over 60, who were living at home. Three series of posturographic tests (static, dynamic with a single and fast upward tilt, and dynamic with slow sinusoidal oscillations) analysing the centre of foot pressure displacements or electromyographic responses were conducted to determine the effects of PSA practice on balance control. RESULTS: The major variables of postural control were best in subjects who had always practised PSA (AA group). Those who did not take part in PSA at all (II group) had the worst postural performances, whatever the test. Subjects having lately begun PSA practice (IA group) had good postural performances, close to those of the AA group, whereas the subjects who had stopped the practice of PSA at an early age (AI group) did not perform as well. Overall, the postural control in the group studied decreased in the order AA > IA > AI > II. CONCLUSIONS: The period during which PSA are practised seems to be of major importance, having a positive bearing on postural control. It seems that recent periods of practice have greater beneficial effects on the subjects postural stability than PSA practice only at an early age. These data are compatible with the fact that PSA are extremely useful for elderly people even if it has not been a lifelong habit.

Influence of visual control, conduction, and central integration on static and dynamic balance in healthy older adults

Aging is associated with decreased balance abilities, resulting in an increased risk of fall. In order to appreciate the visual, somatosensory, and central signals involved in balance control, sophisticated methods of posturography assessment have been developed, using static and dynamic tests, eventually associated with electromyographic measurements. We applied such methods to a population of healthy older adults in order to appreciate the respective importance of each of these sensorial inputs in aging individuals. Posture control parameters were recorded on a force-measuring platform in 41 healthy young (age 28.5 +/- 5.9 years) and 50 older (age 69.8 +/- 5.9 years) adults, using a static test and two dynamic tests performed by all individuals first with eyes open, then with eyes closed. The distance covered by the center of foot pressure, sway area, and anteroposterior oscillations were significantly higher, with eyes open or closed, in older people than in young subjects. Significant differences were noted in dynamic tests with longer latency responses in the group of old people. Dynamic recordings in a sinusoidal test had a more regular pattern when performed eyes open in both groups and evidenced significantly greater instability in old people. These data suggest that vision remains important in maintaining postural control while conduction and central integration become less efficient with age.

Beneficial effect of proprioceptive physical activities on balance control in elderly human subjects.

Age and lack of physical activities may both be responsible for poor balance control. Conversely, physical activities may modulate postural control in elderly individuals. We examined which type of exercise might prove most beneficial to retain or regain proper balance. Nineteen healthy subjects, aged over 60, regularly practicing proprioceptive (group I) or bioenergetic (group II) physical activities and 21 controls only walking on a regular basis, were studied. All were submitted to a dynamic posturographic test and to a test evaluating lower limbs muscular strength. Control individuals displayed the poorest balance and muscular performance. Group I subjects had the best postural control with average muscular strength. In group II, muscular strength was significantly increased, but balance control was of poor quality. Proprioceptive exercise therefore appears to have the best impact on balance control.

Subcellular localization of cytochrome P450, and activities of several enzymes responsible for drug metabolism in the human brain

We studied the subcellular distribution of cytochrome P450 and related monooxygenase activities in six regions of human brains removed at autopsy. The content of total cytochrome P450 was found to be at least nine times higher in the mitochondrial fraction than in the microsomes in all the regions studied. However, cytochrome P450-dependent enzymatic activities which are representative of different isoforms metabolizing exogenous molecules exhibited a microsomal prevalence, a situation previously observed in rat brain. The other drug-metabolizing enzymes catalysing functionalization and conjugation reactions, presented the following characteristics in human brain: (i) a low activity of NADPH-cytochrome P450 reductase, which also catalyses the reduction of some xenobiotics; (ii) a high specific activity of the membrane-bound epoxide hydrolase; (iii) among the enzymes catalysing conjugation reactions, 1-naphthol-UDP-glucuronosyltransferase activity was barely or not detectable, whereas the mean glutathione-S-transferase activity was 15 times higher than the activity measured in rat brain. The presence of several drug-metabolizing enzyme activities in human brain microvessels, and particularly the high activity of epoxide hydrolase, suggests a participation of these enzymes in the metabolic blood-brain barrier.

Blood activity of Cu/Zn superoxide dismutase, glutathione peroxidase and catalase in Alzheimer's disease : a case-control study

Cu/Zn superoxide dismutase (Cu/Zn SOD), glutathione peroxidase (GPx) and catalase, which are the three main enzymes involved in cellular protection against damage due to oxygen-derived free radicals have been assayed in plasma and erythrocytes obtained from subjects with dementia of the Alzheimer type (DAT) and from controls. Blood samples were obtained from 25 patients with DAT and from age-matched subjects without diagnoses of neurological disease (non-DAT), as well as from younger individuals (reference group). Using appropriate statistical procedures, the three enzyme activities measured in blood of the elderly were decreased if compared to the younger reference group. Moreover, a significant increase in erythrocyte Cu/Zn SOD and catalase activities of DAT patients was observed compared to the non-DAT group. These results are discussed taking the free radical theory of aging into consideration.

Malondialdehyde adducts to, and fragmentation of, apolipoprotein B from human plasma

Many recent in vitro experiments support the hypothesis that oxidatively modified low density lipoproteins (LDLs) could participate in atherogenesis. Oxidation of LDLs, especially derivatization by aldehydes originating from peroxidation of fatty acids and fragmentation of apolipoprotein (apo) B-100 which is their major apolipoprotein, probably occurs extravascularly and the presence of oxidized LDLs in the circulation is not well documented. Using electrophoresis and immunodetection techniques, we studied the structure of apo B and the presence of adducts of malondialdehyde (MDA) to this protein in LDLs from plasma of a limited population of five healthy subjects and nine patients with severe atherosclerosis. In the patient-derived LDLs, apo B appeared extensively fragmented, much more so than in those from the healthy subjects, although LDLs were isolated in all cases in the presence of antioxidants, protease inhibitors and antibiotics. Additionally, in all healthy subjects, we found a minor fragment of apo B-100, apo B-74, whereas the complementary peptide, apo B-26, was not detected; thus the presence of this minor form cannot be related to cleavage of apo B-100, either by proteolysis or by oxidation. We also present evidence that MDA adducts are present in circulating apo B and most of its fragments not only in atheromatous patients, but also in healthy subjects. Our results are consistent with the existence of oxidized LDLs in the human circulation. However, the role of non-oxidative phenomena in the structural modifications affecting apo B which are reported here cannot be excluded.

Age-related variations of enzymatic defenses against free radicals and peroxides

Superoxide dismutase, glutathione peroxidase and catalase are the three main enzymatic systems of defense of the organism against free radicals and peroxides. A survey of the literature shows that no general tendency of evolution of these systems in aging emerges, even if some recent studies in humans demonstrate the existence of a concomitant decrease in most of the antioxidant enzymes in blood of the elderly. The study of the antioxidant systems and their interrelations in the elderly represents a large field of future investigations.