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Biomedical subjects

Y Touitou

Publications and source records attributed to Y Touitou.

180 records · Page 10Linked to original sources
PubMedDate not supplied

Modifications of circadian and circannual rhythms with aging.

Whereas biological rhythms are now fairly well documented in young healthy adults, reports in elderly are relatively few for obvious reasons, including the difficulty of setting groups matched in age, sociological and professional background, medical history, and not in need of specific medication. Aging may modify one or several parameters characterizing biological rhythms. The modifications are different from one function to the next, and great care should be given not to mistake changes attributable to the aging process with those resulting from physical and physiological impairment caused by passed environmental aggressions and diseases. Nevertheless, the increasing number of subjects reaching the age of 65 or older, thanks to medical progress, makes necessary establishing time-qualified references values in the aged, as this kind of investigation should lead to an improvement of the conditions and quality of life of elderly subjects.

Aging↗
PubMedDate not supplied

Study of circadian melatonin secretion pattern at different stages of Parkinson's disease.

To explore changes in melatonin secretion patterns and biologic rhythms in Parkinson's disease patients with or without levodopa-related motor complications (LDRMCs), the authors investigated, in an observational study, circadian rhythms of central temperature, motor activity, plasma cortisol, and melatonin in three groups: de novo untreated patients (group I), patients treated with levodopa + dopamine agonist and without LDRMCs (group II), and patients treated with levodopa + dopamine agonist and with LDRMCs (group III). There were no differences among the three groups for the rhythm of temperature, motor activity, or plasma cortisol. There was a significant (p < 0.05) phase advance in plasma melatonin secretion in patients receiving a dopaminergic treatment compared with untreated patients. The daytime area under the curve (AUC) was increased significantly in group III, and the nighttime AUC-to-daytime AUC ratio of melatonin secretion decreased significantly in group III, suggesting that the nychthemeral pattern of melatonin secretion was changed in patients with LDRMCs. Comparison of the three groups suggests a slight but insignificant phase advance and amplitude decrease of circadian melatonin secretion related to both evolution and treatment of Parkinson's disease. Despite the lack of a global desynchronization in other circadian biologic rhythms, the circadian secretion pattern of melatonin is modified in patients with LDRMCs.

Aged↗
PubMedDate not supplied

Cancer-associated alteration of circadian rhythms in carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) in humans.

A circadian rhythm of serum concentrations of two tumor markers (CEA and AFP) was demonstrated in individuals not suffering from cancer. These rhythms exhibited a diurnal peak with a nocturnal dip. They disappeared in cancer groups. However, in some cancer subjects, a circadian activity was still detectable, but with quite different characteristics (time of peak, amplitude) of rhythms when compared to controls. The importance of such findings is discussed with regard to the circadian kinetics of cancer cells, to time scheduled cancer treatments and to the detection of cancer.

Carcinoembryonic Antigen↗
PubMedDate not supplied

CA-125 ovarian cancer associated antigen in cancer and pregnancy: interpretation of enzyme immunoassay and immunoradiometric assay.

Serum CA-125 concentrations were determined using both immunoradiometric assay (IRMA) and enzyme immunoassay (EIA) in 67 patients with various diseases including cancer and in 100 pregnant women with respect to the stage of pregnancy. Correlation of values obtained by the two methods was good except for the first and second trimester of pregnancy. However, IRMA concentrations were 80-200% higher than those obtained by EIA, the larger differences being observed in the critical range of 35-100 U/mL. Therefore, the alternate use of the two methods should be avoided and the cutoff levels should be redefined for each procedure.

Adult↗
PubMedDate not supplied

Internal desynchronization of circadian rhythms and tolerance of shift work.

Fifteen male subjects including 12 shift workers (oil refinery operators) volunteered to document circadian rhythms in sleep-wake, grip strength of both hands, peak expiratory flow, heart rate, self-rated drowsiness, fatigue and attention. Each of these variables was measured 4 to 6 times/day for 2 to 3 weeks. In addition, both axillary temperature (with a shielded probe) and wrist activity were almost continuously recorded at 15 min intervals during the same time span. Individual time series were analyzed according to several statistical methods (power spectrum, cosinor, chi 2, etc.), in order to estimate the prominent circadian period tau and to evaluate both individual and subgroup differences with regard to tolerance of shift work, age, duration of shift work. The present study confirms for continuously recorded temperature and wrist activity, grip strength of both hands, heart rate and peak expiratory flow that intolerance of shift work is frequently associated with an internal desynchronization. However, this conclusion cannot be extended to circadian rhythms in self-rated drowsiness, fatigue and attention. The internal desynchronization among several circadian rhythms supports the hypothesis that these latter are driven by several oscillators, with presumable differences between right and left hemispheres as suggested by unequal values of tau in rhythms of both hand grip strength. Since an internal desynchronization can be observed in tolerant shift workers having no complaint, it is likely that symptoms of intolerance are related to the subject's sensitivity to internal desynchronization rather than to the desynchronization itself.

Adult↗
PubMedDate not supplied

Clinical chronopharmacology of ACTH 1-17. I. Effects on plasma cortisol and urinary 17-hydroxycorticosteroids.

The aim of the investigation was to study the effects of ACTH 1-17 on both plasma cortisol and urinary 17-OHCS in health adult young males with regard to the time (clock hours) at which this polypeptide was injected. Eight healthy adults (males from 18-30 years) volunteered for the study. They were synchronized with a diurnal activity from 0700 to 0000 and a nocturnal rest. Each week, during 6 consecutive weeks (January 19 to February 25, 1980), a 3-day test was performed on Saturday, Sunday and Monday. On Sundays 3 control-tests and 3 ACTH-tests were programmed during which either saline or 100 micrograms ACTH 1-17 were injected i.m. at respectively 0700, 1400 and 2100. During each 3 day-test (72 h) the urinary excretion of 17-OHCS was determined every 4 h at fixed clock hours. In addition, on Sundays, venous blood was sampled prior to control or ACTH injections at respectively 0700, 1400, and 2100 and 20, 40, 60, 90, 120, 150 and 180 min thereafter. Plasma cortisol (radioimmunoassay) was determined in samples thus collected. Both conventional and cosinor methods were used for statistical analyses. A strong and statistically significant rise of plasma cortisol was observed after all of the ACTH 1-17 injections. The obtained mean response curves were observed after all of the ACTH 1-17 injections. The obtained mean response curves were similar in form and parallel. The highest plasma cortisol curve corresponded to ACTH injected at 0700, the lowest to ACTH injected at 2100. The curve corresponding to ACTH injected at 1400 went in-between. The 24-h urinary excretion of 17-OHCS after ACTH 1-17 was approximately 4 times greater than the control value when injected at 0700, approximately 3 times greater than control when injected at 1400 and only twice greater than control when injected at 2100. In terms of changes in plasma cortisol and 17-OHCS the greatest best benefit of ACTH 1-17 is achieved when this polypeptide is injected at 0700, rather than at 1400 or 2100 in diurnally active subjects.

17-Hydroxycorticosteroids↗
PubMedDate not supplied

Clinical chronopharmacology of ACTH 1-17. II. Effects on plasma testosterone, plasma aldosterone, plasma and urinary electrolytes (K, Na, Ca and Mg).

The aim of the investigation was to study the effects of ACTH 1-17 on plasma testosterone, plasma aldosterone as well as on both plasma and urinary electrolytes (K, Na, Mg and Ca) in healthy young adult males with regard to the time (clock hours) at which this polypeptide was injected. Eight healthy adults (males from 28 to 30 years) volunteered for the study. The were synchronized with a diurnal activity from 0700 to midnight and a nocturnal rest. Each week, during 6 consecutive weeks (January 19 to February 25, 1980) a 3-day test was performed on Saturday, Sunday and Monday. On Sundays 3 control-tests and the 3 ACTH-tests were programmed during which either saline or 100 microgram ACTH 1-17 were injected i.m. at respectively 0700, 1400 and 2100. During each 3 day-test period (72 h) the urinary excretion of K, Na, Mg and Ca was determined every 4 h at fixed clock hours. In addition, on Sundays, venous blood was sampled prior to control or ACTH injections at respectively 0700, 1400 and 2100 and 20, 40, 60, 90, 120, 150 and 180 min thereafter. Plasma testosterone, aldosterone (radioimmunoassays) K, Na (flame photometry), Mg and Ca (photocolorimetric methods) were determined in the collected samples. Both conventional and cosinor methods were used for statistical analyses. The injection of ACTH at 0700 was followed by a clear and statistically significant rise of plasma testosterone. No change with regard to control occurred when ACTH was injected at either 1400 or at 2100. A statistically significant rise of plasma aldosterone was observed after each of the ACTH injections. However, the highest plasma aldosterone level was reached when ACTH was administered at 1400 and the lowest level at 2100. ACTH-induced changes in plasma electrolytes were either nil (for Na and Ca) or small (for K and Mg). A more or less important increase of urinary K occurred after the ACTH injection at each of the 3 considered times. The highest values of excreted K occurred after the injection of ACTH at 0700, without shift of the acrophase. In contrast, injections of ACTH at 1400 and 2100 induced a dramatic alteration of the K rhythms. ACTH induced an important fall in the Na urinary excretion. This fall was the greatest when ACTH was injected at 1400. Na rhythm alterations also occurred, particularly after ACTH injections at 2100. However, this effect was less pronounced after ACTH injection at 0700 than at other considered time points. The urinary amount of excreted Ca did not seem to be affected by ACTH. Rhythm alterations occurred after ACTH injections at 1400 and 2100. Peaks of plasma testosterone, plasma aldosterone as well as plasma cortisol (reported in a previous paper) resulting from ACTH stimulation coincided in time with the acrophase of the physiological circadian rhythm in plasma levels of these hormones...

Adolescent↗
PubMedDate not supplied

[Circadian and circannual rhythms in results of functional tests in endocrinology].

Basic aspects of the temporal organization of endocrine circadian systems are summarized. Emphasis is given to the concept of chronesthesy (rythmic changes in the susceptibility of target biosystems) and that of chronokinetics (rhythmic changes in the metabolic fate of hormones and other agents). These complementary concepts are needed for the understanding of circadian and/or circannual changes in results of a test. The following substances used either for stimulation or suppression tests were investigated: metyrapone, ACTH, corticosteroids (e.g. dexamethasone), TRH, HCG, glucose, insulin. The subject's synchronization, the time (clock hour in the 24 hours scale, month in the yearly scale) appears to be at least as important as conventional factors such as subject's sex, age, nutritional state when performing a test and interpreting the results.

Adaptation, Physiological↗
PubMedDate not supplied

[Melatonin and aging].

Melatonin is a hormone secreted mainly by the pineal gland but also by the retina. It is synthesized from tryptophan and its characteristic circadian rhythm is ruled by light through the control of two limiting enzymic activities N-acetyl-transferase and hydroxyindole-O-methyl-transferase. In man--as in all studied species--its maximum plasma concentration is at night. Therefore it is considered as a signal transducing information on solar light within the organism thus providing the temporal framework upon which metabolic pathways are organized. Since its circulating levels decrease with ageing the question arises as to the origin and/or the consequences of this decrease, as well as the possible beneficial effects which could result from its administration in ageing humans.

Aging↗