Circadian rhythms of body temperature and motor activity in rodents their relationships with the light-dark cycle.

In rodents, the alternation of light and dark is the main synchronizer of circadian rhythms. The entrainment abilities of the LD cycle could be estimated by experimental modifications of the photoperiod and by following the subsequent temporal distribution of a circadian rhythm. The rate of reentrainment of a rhythm is determined by the nature of the studied variable, by the direction (advance or delay) and the magnitude (or value) of the phase shift. In rodents, core body temperature and motor activity are known to be well synchronized with each other under L:D 12:12 and under constant conditions (LL or DD). There are clear evidences that the circadian pattern of motor activity is generated by two oscillators, one from dusk signal and the other from dawn signal. Whether the circadian rhythms of body temperature and motor activity are generated by a common circadian mechanism or controlled by separate ones still remains unknown. The purpose of this review is to summarize the results obtained on the circadian rhythms of body temperature and motor activity throughout the daily cycle in order to clarify the relationships between these two functions.

Is melatonin circadian rhythm a physiological feature associated with healthy longevity? A study of long-living subjects and their progeny.

The study investigates the circadian rhythm (CR) of urinary 6-sulphatoxy-melatonin (aMT6s) in long-living (longevous) subjects and their progeny. The aim is to detect whether or not the melatonin CR is a physiological feature associated with healthy longevity. The aMT6s CR was investigated in 10 longevous subjects, 8 of their children and 9 of their grandchildren, all in good health. Control data were obtained respectively from 13 adult subjects and 9 young subjects, in good health, but characterized by a negative family history for longevity. All the subjects were born and living in the same city. The study was performed in the summer of 1996. The aMT6s CR was found to persist in longevous subjects, being characterized by a lower mesor and amplitude. The aMT6s CR was found not to show properties consistently different in children and grandchildren as compared respectively to their adult and young controls. Because of its preservation in longevous subjects, it can be argued that the melatonin CR is a physiological feature associated with healthy longevity. Because of the comparability of aMT6s CR in children and grandchildren, with respect to their controls without a positive family history of longevity, it can be argued that the melatonin CR is not a marker that can be used for an earlier identification of the candidates for longevity.

Body temperature and locomotor activity as marker rhythms of aging of the circadian system in rodents.

Most biological functions present rhythmic variations. These rhythms are distinguished by their period and concern all the levels of biological life. Circadian rhythms follow a periodicity close to 24-h, they allow individuals to survive via adaptation to the periodic variations of environment. Throughout the aging process, modifications in circadian rhythms of endocrinological, metabolical and behavioural fields have been found in many animal species. This review updates the body of knowledge on aging-related alterations of the circadian rhythms of body temperature and locomotor activity: modifications in circadian profiles, modifications in the period of free-running rhythms, internal desynchronisations and modifications in entrainment ability of these rhythms.

[Melatonin and aging]. / Mélatonine et vieillissement.

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.

Disruption of the circadian patterns of serum cortisol in breast and ovarian cancer patients: relationships with tumour marker antigens.

Few data are available on the circadian rhythmicity in cancer patients. Since monitoring the disease usually implies the follow-up of blood concentrations of a number of biological variables, it would be of value to examine the profile of the circadian variations of serum cortisol and tumour marker antigens. This we did in 33 cancer patients (13 breast cancer patients and 20 ovarian cancer patients). The profiles of serum cortisol were documented, since this hormone is considered as a strong marker of circadian rhythms. This study shows that 8 out of 13 breast cancer patients and 15 out of 20 ovarian cancer patients had deeply altered cortisol circadian patterns. The modifications were either high levels along the 24 h scale and/or erratic peaks and troughs and/or flattened profiles. Within 24 h, variations of tumour marker antigens as large as 70% were observed but no typical individual circadian patterns could be found. No relationship between cortisol subgroups and concentration of tumour marker antigens at 8 h could be observed (Kolmogorov-Smirnov's test). The question thus arises as to the origin of these alterations, and whether they are related to a cause or a consequence of the disease, and their possible incidence upon therapeutic designs.

Acute exposure to 50 Hz magnetic field does not affect hematologic or immunologic functions in healthy young men: a circadian study.

Some epidemiological studies report a relationship between magnetic field exposure and such human diseases as leukemia and immune system disturbances. The few published studies on animals do not demonstrate field exposure-related alterations in hematologic and immune systems. The data presented here are part of a broader study designed to investigate the possible effects of acute exposure to a 50 Hz linearly polarized magnetic field (10 microT) on hematologic and immunologic functions. Thirty-two young men (20-30 years old) were divided into two groups (control group i.e., sham-exposed. 16 subjects; exposed group, 16 subjects). All subjects participated in two 24 h experiments to evaluate the effects of both continuous and intermittent (1 h "off" and 1 h with the field switched "on" and "off" every 15 s) exposure to linearly polarized magnetic fields. The subjects were exposed to the magnetic field (generated by three Helmholtz coils per bed) from 23:00 to 08:00 while lying down. Blood samples were collected during each session at 3 h intervals from 11:00 to 20:00 and hourly from 22:00 to 08:00. No significant differences were observed between sham-exposed (control) and exposed men for hemoglobin concentration, hematocrit, red blood cells, platelets, total leukocytes, monocytes, lymphocytes, eosinophils, or neutrophils. Immunologic variables [CD3, CD4, CD8, natural killer (NK) cells and B cells] were unaltered. To our knowledge, this study is the first to document the effects of a 50 Hz magnetic field on the circadian rhythm of human hematologic and immune functions, and it suggests that acute exposure to either a continuous or an intermittent 50 Hz linearly polarized magnetic field of 10 microT, at least under the conditions of our experiment, does not affect either these function or their circadian rhythms in healthy young men.

An alternate pathway to androstenedione synthesis by human adrenals: evidence of a balance in 11 beta-hydroxylase and 17,20-lyase activities leading to androstenedione.

Until now, dehydroepiandrosterone and 17-hydroxyprogesterone were thought to be the main precursors for the synthesis of androstenedione by the human adrenal cortex. However, secretion of androstenedione and 11-deoxycortisol are increased when 11 beta-hydroxylase activity is impaired, e.g. by metyrapone test or by congenital adrenal hyperplasia resulting from 11 beta-hydroxylase deficiency. The present study with human adrenals shows that 11-deoxycortisol, the precursor of cortisol synthesis, is also a precursor of androstenedione in humans. Our data show that androstenedione synthesis is inversely related to the synthesis of cortisol and cortisone. This new pathway is thus triggered by a lower activity of 11 beta-hydroxylase that is responsible for the last step of cortisol. Indeed, when the activity of this enzyme is impaired, 11-deoxycortisol follows the pathway that leads to androstenedione synthesis in the adrenals. These data, together with the increase in ACTH secretion, may explain the increased androstenedione plasma levels observed in patients with congenital adrenal hyperplasia caused by 11 beta-hydroxylase deficiency and in patients given inhibitors of 11 beta-hydroxylase for therapeutic purposes.

In vitro glucocorticosteroid and mineralocorticosteroid biosynthesis in Conn's adenoma tissues.

The in vitro metabolism of [1,2-3H] deoxycorticosterone (DOC), [1,2-3H] 18-hydroxy-11-deoxycorticosterone (18-OHDOC) and [1,2-3H] 11-deoxycortisol (S) was studied in adrenal adenoma homogenates from patients with primary hyperaldosteronism. Tumor tissues actively converted deoxycorticosterone and 18-hydroxy-11-deoxycorticosterone to 18-hydroxycorticosterone and aldosterone. Yields of cortisol and cortisone were also large showing that the tissues did not lack the zona fasciculata-like 11 beta-hydroxylation ability.

The in vitro effect of metyrapone on steroid synthesis in mice adrenals at different circadian stages.

The circadian rhythm of the in vitro biosynthesis of cortisol and cortisone in mice adrenals has been documented in the absence and presence of 0.1 mumol metyrapone, an inhibitor of steroid 11 beta-monooxygenase. After 3 weeks of synchronization with 12 h light:12 h darkness, adrenalectomy was performed at eight circadian stages: 0, 4, 9, 10, 13, 16, 21, and 22 h after light onset (HALO). Because it has been shown that mice adrenals could convert exogenous 11-deoxycortisol, the synthesis of 11-oxysteroids (cortisol+cortisone) in adrenal homogenates was studied from tritiated precursor. The pattern of steroid synthesis showed a maximum around the end (10 HALO) and a minimum at the beginning of the resting period (0 HALO); the variation was approximately 10%. A similar pattern was observed in the presence of a approximately 50% inhibiting dose of metyrapone. On the other hand, the percent inhibition of 11-oxysteroids synthesis was greater at the beginning of the resting period (0 HALO) and minimum around the end of the activity span (21 HALO), with an overall variation of 20%. However, the variations were statistically insignificant (unpaired t test).

Concurrent adrenocortical carcinoma and Conn's adenoma in a man with primary hyperaldosteronism. In vivo and in vitro studies.

This is a report of a rare and unusual case of adrenal pathology. A patient presented with clinical and biological signs of primary aldosteronism and computed body tomography scan led to our suspecting the presence of a left adrenocortical carcinoma. The in vitro studies performed on the resected tumour showed very low synthesis of mineralocorticoids and glucocorticoids. The patient could not be reexamined until 15 months later, when he still suffered hypertension; another tomography scan revealed a mass on the right adrenal gland. The studies performed on this second tumour confirmed the diagnosis of Conn's adenoma: active in vitro biosynthesis of 18-hydroxy-corticosterone and aldosterone from exogenous tritiated precursors.

Evidence for a new biologic pathway of androstenedione synthesis from 11-deoxycortisol.

17-Hydroxyprogesterone is a well-known precursor of androstenedione in adrenal biosynthesis. This study using sheep adrenal incubations demonstrates that 11-deoxycortisol, the precursor of cortisol synthesis, also can be a precursor of androstenedione. Indeed, our data show that androstenedione synthesis is negatively correlated to the synthesis of cortisol and cortisone. This fact allowed us to infer that this new pathway is closely related to the activity of the 11 beta-hydroxylase that is responsible for the synthesis of cortisol. Indeed, when the activity of this enzyme is impaired, 11-deoxycortisol follows the pathway that leads to androstenedione synthesis in the adrenals. This pathway could explain, at least in part, the marked increase of androstenedione observed in congenital adrenal hyperplasia due to 11 beta-hydroxylase deficiency.

Cortisol and cortisone production in rat and mouse adrenal incubations.

The presence of 17 alpha-hydroxylase in rodent adrenals is debated. The presence in blood of mice of 11-deoxycortisol together with the absence of cortisol is well known. We demonstrated here the in vitro synthesis of 17 alpha-hydroxyprogesterone and cortisol from [3H]progesterone in rat and mouse adrenals. We have shown that these syntheses represented 45 and 28% of those of 11-deoxycorticosterone and corticosterone, respectively, from progesterone. These data clearly suggest the presence of a 17 alpha-hydroxylase activity in vitro in these rodents adrenals. In addition, a noticeable synthesis of cortisol (0.87-1.57% per mg tissue, i.e. 52-64% per incubation flask) from 11-deoxycortisol was also observed and was inhibited by 0.1-0.3 mumol of Metyrapone and SKF 12185. These results allow to underline that the adrenals of rat and mouse, two species commonly used in laboratory experiments, may be used for in vitro investigations on cortisol metabolism from exogenous radioactive precursors.

Effect of shift work on the night-time secretory patterns of melatonin, prolactin, cortisol and testosterone.

In a study of the internal desynchronization of circadian rhythms in 12 shift workers, 4 of them, aged 25-34 years, agreed to be sampled every 2 h during their night shift (0000 hours to 0800 hours). They were oil refinery operators with a fast rotating shift system (every 3-4 days). We found marked changes in the secretory profiles of melatonin, prolactin and testosterone. Melatonin had higher peak-values resulting in a four-times higher amplitude than in controls. With respect to prolactin and testosterone, peak and trough times were erratic and the serum concentrations were significantly decreased in shift workers. Serum cortisol presented a decreased rhythm amplitude together with higher concentrations at 0000 hours in shift workers. This study clearly shows that fast rotating shift-work modifies peak or trough values and rhythm amplitudes of melatonin, prolactin, testosterone and cortisol without any apparent phase shift of these hormones. Whether the large rhythm amplitude of melatonin may be considered as a marker of tolerance to shift work, as reported for body temperature and hand grip strength, since it would help the subjects to maintain their internal synchronization, needs further investigation.

Urinary neopterin in pulmonary sarcoidosis. Relationship to clinical and biologic assessment of the disease.

Neopterin is a metabolite of guanosine-triphosphate, released in vitro by macrophages under the control of gamma-interferon and described as a marker of T cell activation in vivo. We have compared the urinary neopterin/creatinine ratio (mumol/mol) in patients with pulmonary sarcoidosis (n = 66), interstitial lung diseases other than sarcoidosis (nonsarcoid ILD, n = 35), and 45 normal control subjects. For the sarcoid population as a whole, urinary neopterin was higher (496 +/- 52 mumol/mol [mean +/- SEM]) than in control subjects (126 +/- 5 mumol/mol) (p less than 0.001). In patients with nonsarcoid ILD, urinary neopterin was frequently higher in granulomatous and/or lymphoproliferative diseases (hypersensitivity pneumonitis, tuberculosis, primitive Sjögren's syndrome, and malignant lymphomas) (781 +/- 193 mumol/mol, n = 10) but remained normal in other types of nonsarcoid ILD [( 163 +/- 14 mumol/mol, n = 25]: histiocytosis X, idiopathic pulmonary fibrosis, lung collagen-vascular diseases, diffuse neoplasms, pneumoconiosis; p less than 0.001 compared with sarcoidosis). We have also evaluated the relationship between urinary neopterin and the clinical or biologic markers currently used to assess sarcoidosis: alveolar lymphocytosis in lavage fluid (ALY), 67-gallium scan semiquantitative index (67Ga), or serum angiotensin-converting enzyme (SACE). Sarcoid patients with the highest urinary neopterin were those in whom mean values of these markers were the highest (p less than 0.05, all comparisons). Patients with positive markers (i.e., either clinical expression of sarcoidosis-ALY greater than 30%-67Ga greater than 20-SACE greater than 60 U/ml) had significantly higher urinary neopterin levels than did other sarcoid patients (p less than 0.05, all comparisons).

Evidence of 11 beta-hydroxylase deficiency in a patient with cortical adrenal adenoma.

We explored a 61 year old woman with mild hirsutism. An adrenal tumor was found in the left adrenal, which was held responsible for the androgen secretion. The in vitro incubation of the tumor tissue showed an impaired 11 beta-hydroxylation of 11-deoxycortisol. This is a rare and unusual case of adrenal pathology showing that a deficiency in 11 beta-hydroxylase activity does not rule out the presence of an adrenocortical adenoma.

Circadian and seasonal variations of electrolytes in aging humans.

The circadian and seasonal variations of a set of routinely determined variables (chloride, sodium, potassium, calcium, inorganic phosphorus, magnesium, creatinine, urea and urate) were documented in young men (mean age +/- SD: 24.0 +/- 3.9 yr) and in healthy elderly men (75.3 +/- 6.6) and women (78.2 +/- 9.1). The same urinary variables, except magnesium, were studied in young men. The circadian variability of serum variables was between 2 and 11% except for serum inorganic phosphorus (12-22% according to the group). By contrast, urinary chloride, sodium and potassium revealed large peak-trough differences (55-75%) and the variability of urinary creatinine, urate and urea was also not negligible (20-30%). ANOVA validated seasonal variations for most of the plasma variables and for urinary calcium, phosphorus and uric acid. No age or sex difference in either 24 h means or amplitudes could be observed. These data are of interest for the concept of reference values, for the diagnosis of certain bone and renal disease as well as for chronooptimization in treatment of potential electrolytes deficiency states.

Lack of effect in vivo of clofibrate on adrenal steroid secretion.

Clofibrate inhibits the synthesis of adrenal steroids when administered in vitro. In the present study the effect in vivo of clofibrate on adrenal steroid secretion has been investigated. Basal levels of plasma progesterone, corticosterone, aldosterone, 17-hydroxyprogesterone, 11-deoxycortisol, cortisol, dehydroepiandrosterone sulphate and dehydroepiandrosterone, and their response to ACTH 1 mg im, were not reduced by chronic administration of clofibrate 2 g per day p.o. for 8 to 34 days to 6 hyperlipidaemic men.

Activity of melatonin and other pineal indoles on the in vitro synthesis of cortisol, cortisone, and adrenal androgens.

The in vitro effects of 13 indole compounds on the synthesis of glucocorticoids and of adrenal androgens in sheep adrenal glands has been studied from 11-deoxycortisol as a precursor. This work demonstrates the activating effect of some indole compounds on 11 beta-hydroxylase and 17,20-desmolase and the inhibitory effect of most of them on 11 beta-hydroxysteroid dehydrogenase. Three categories could be distinguished: 1) compounds without any effect (5-hydroxytryptophan, 5-hydroxytryptamine); 2) compounds moderately increasing (10-30% as compared with controls) cortisol yields (tryptamine, melatonin, 6-hydroxymelatonin, 5-methoxytryptophol, indomethacin); and 3) compounds markedly increasing (80-100%) cortisol yields (5-methoxyindole acetic acid, 5-hydroxyindole acetic acid, 2-methylindole, 5-hydroxytryptophol, N-acetyl-5-hydroxytryptamine). In fact, since most of the studied indoles reduced 11 beta-hydroxysteroid dehydrogenase activity, the actual activation of cortisol synthesis was four to five times less. Lastly, all the studied compounds, but melatonin, increased the activity of 17,20 desmolase as seen from 11 beta-hydroxyandrostenedione and 11-ketoandrostenedione yields. The possible in vivo effects of the indoles for therapeutic use needs further studying.