Seasonal modulation of the circadian time structure of circulating T and natural killer lymphocyte subsets from healthy subjects.

A seasonal modulation of the circadian time structure of circulating T and natural killer (NK) lymphocyte subtypes was documented in five healthy men aged 24-36 yr. Venous blood was obtained every 4 h for 24 h from each subject in January, March, June, August, and November 1984. Three subjects were also studied in April and/or August and/or November 1983 for the T subsets only. Mononuclear cells were isolated on Ficoll-Paque gradient and aliquots were incubated with OKT3, OKT4, OKT8, or HNK-1 monoclonal antibodies for characterizing all, T, T helper, T suppressor-cytotoxic, and NK lymphocytes, respectively, under an epifluorescence microscope. An effect of both sampling time and study month was statistically validated (P less than 0.01) with both two-way analysis of variance and cosinor for the peripheral counts in total, pan-T, T helper, and NK lymphocytes (cells per cubic millimeter). Seasonal changes affected both the circadian patterns and the 24-h mean values. Thus the double amplitude (total extent of variation) of the circadian rhythm in circulating total, T and T helper lymphocytes varied between 0 in March (P greater than 0.30; no rhythm) and up to 46-68% of the 24-h-mean (M) in November, with acrophases (times of maximum, 0) localized in the first half of the night (P less than 0.001). Maximal values were found at 8:30 h for both T suppressor-cytotoxic and NK lymphocytes; a smaller second peak was also found at 20:30 h, and a 12-h rhythm was validated by cosinor (P less than 0.0001), with no patient change in waveform along the year scale. A circannual rhythm was statistically validated by cosinor for total (0 in November), pan-T (0 in March), T suppressor-cytotoxic (0 in December), and NK lymphocytes (0 in October). A rhythm with a period equal to 6 mo was found for circulating T helper cells with 0 occurring both in April and October. Seasonal variations in the incidence of several immunologically related diseases may correspond to an endogenous circannual time structure.

Circadian rhythm in toxicities and tissue uptake of 1,2-diamminocyclohexane(trans-1)oxalatoplatinum(II) in mice.

Mechanisms involved in the circadian rhythm in murine tolerance for the new platinum analogue, 1,2-diamminocyclohexane(trans-1)oxalatoplatinum(II) (1-OHP) were sought in 404 male C57BL/6 x DBA/2 F1 mice standardized by 12 h light-12 h dark. A potentially lethal dose of 1-OHP (17 mg/kg i.v.) resulted in 76% long-term survival at 15 h after light onset (HALO) (activity span) as compared to 24% after treatment at 7 HALO (rest span) (chi 2 21.3; P less than 0.001). A total of 204 mice received the same dose of 1-OHP at one of three circadian stages (0, 8, or 16 HALO). No renal toxicity was encountered. Bone marrow and jejunal villi constituted the chief targets of 1-OHP toxicity at this dosage and schedule. Hematological tolerance as gauged by leukocyte counts was optimal when the drug was given at 16 HALO (P from analysis of variance, less than 0.001). Jejunal lesions were less severe after 1-OHP dosing at 16 HALO as compared to 8 HALO (P less than 0.001). Total platinum concentrations were determined in 18 tissues 24 h after 1-OHP dosing. The highest levels of platinum were found in the spleen on day 1 as well as on day 5 following 1-OHP treatment. Despite the fact that the highest platinum concentrations in tissues usually corresponded to drug dosing at 8 HALO, no correlation was documented between such variables and tissue toxicity. Tissue pharmacokinetics of 1-OHP contribute only in part if at all to the circadian rhythm in hematological and jejunal toxicity of this drug.

A four-day subrenal capsule assay for testing the effectiveness of anticancer drugs against human tumors.

The subrenal capsule assay may predict to which anticancer drug a given patient's tumor is sensitive and may also be used to screen new anticancer drugs. The present study documents that the use of this model requires a histological assessment of both the exploitability of a subrenal capsule assay and the extent of drug-induced antitumor lesions. Thirty-five tumors from 34 patients with solid tumor were submitted to a subrenal capsule assay in a total of 1130 male B6D2F1 mice. After being biopsied, each tumor was dissected by a pathologist and cut into 50 pieces (1.5 X 1.5 X 1.5 cu mm), and one piece was implanted under the renal capsule of 35 mice; the mean tumor diameter was measured on Day 0. Mice were randomized into groups of 6 to 10 animals each. On Days 1, 2, and 3, mice were treated either with placebo (control group) or with various anticancer agents. On Days 4 or 6, mice were sacrificed, the mean tumor diameter measured, and the tumor-bearing kidney fixed in Bouin's picroformol solution and processed for histological analysis after staining with hematein -eosin. Seven histological parameters were blindly rated in a semiquantitative fashion yielding a compound score ( PAPAN ) which estimated the overall quality of each xenograft between -3 and +11. On Day 4, as opposed to Day 6, mean lymphocytic infiltration was 3-fold lower (p less than 0.01), and the rate of xenografts containing well-preserved cancer cells was 2-fold larger (p less than 0.01) in three different tumor specimens. Twenty-two of 31 (71%) assays were evaluable, as defined by a histological quality control test. In those, drug effects were demonstrable by statistically significant differences among groups in 2 assays (9%) by using the relative variation in tumor size as an index of drug effectiveness and in 12 assays (54%) by PAPAN histological score. This suggests the higher sensitivity of histological scoring over tumor size measurements. Moreover, no correlation between relative variation in tumor size and PAPAN was demonstrable with statistical significance indicating the poor reliability of tumor size measurements as an index of the antitumor effectiveness of cytostatic drugs.

Chemotherapy of advanced ovarian cancer with 4'-O-tetrahydropyranyl doxorubicin and cisplatin: a randomized phase II trial with an evaluation of circadian timing and dose-intensity.

The efficacy and toxicity of the new anthracycline, 4'-0-tetrahydropyranyl doxorubicin (THP) (50 mg/m2 intravenous [IV] bolus) in association with cisplatin (100 mg/m2 IV as a 4-hour infusion) was assessed in 31 patients with advanced ovarian carcinoma. Twenty-eight patients were assessable for toxicity among whom 25 were assessable for response (International Federation of Gynecology and Obstetrics [FIGO] stage IIIa, four patients; IIIb, 15 patients; IV, six patients). Nine patients had received prior treatment. Patients were randomized to receive schedule (sch) A (THP at 6 hours, then cisplatin from 16 to 20 hours) or sch B (THP at 18 hours, then cisplatin from 4 to 8 hours). Sch A was hypothesized as less toxic since THP was best tolerated in the late rest span and cisplatin near the middle of the activity span in experimental studies. The rate of clinical complete response (CR) was 52%, that of partial response (PR) was 12%, and the overall clinical response rate (CR plus PR) was 64% (sch A, 73%; sch B, 57%). Median progression-free survival and survival times were, respectively, 10 and 19 months. Of 12 patients in clinical CR evaluated at second-look laparotomy, four had a pathological CR (33%), and three had microscopic residual disease (MD). The overall rate of pathological CR was 16%. Sch A was associated with less neutropenia (P = .10), thrombocytopenia (P less than .01), anemia (P less than .01), and renal toxicity (P less than .05) than sch B. Of four patients withdrawn for toxicity, three were on sch B (one death). Mean dose intensities (DIs) of THP and cisplatin, respectively, decreased by 30% and 47% over the five initial courses. Such decrease was significantly more pronounced for sch B than for sch A in previously untreated patients (P from 2-way analysis of variance [ANOVA] less than .01). THP-cisplatin is active against advanced ovarian cancer, and its toxicities can be significantly decreased by dosing THP in the early morning and cisplatin in the late afternoon as compared with THP in the evening and cisplatin the next morning.

Biological rhythms in the inflammatory response and in the effects of non-steroidal anti-inflammatory drugs.

It is well known that some signs and symptoms of rheumatoid arthritis (RA) vary within a day and between days, and the morning stiffness observed in RA patients has become one of the diagnostic criteria of the disease. Research carried out in the last 10 years confirmed these clinical observations, and circadian, circaseptan or circannual variations were detected in experimental inflammation and in patients with arthritis diseases. The human data showed also that large interindividual differences can be found in the symptoms of RA. The chronopharmacological studies carried out with the non-steroidal anti-inflammatory drugs (NSAID) revealed circadian and circannual variations in the effectiveness, toxicity and pharmacokinetics of NSAID. A review of the available data suggests that peak and trough values found in different arthritic diseases do not occur at the same hour of the day and that the side effects produced by NSAID are more important after the morning than the evening administration. This information should be used by clinicians to determine when to administer drugs to arthritic patients, to optimize the effectiveness of NSAID and/or to reduce the side effects of these drugs. These new data could also be useful to physicians who would like to individualize NSAID use in patients with different arthritic diseases.

Analysis of circadian and ultradian rhythms of skin surface properties of face and forearm of healthy women.

Biologic rhythms of cells and organisms are well documented and have been extensively studied at the physiologic and molecular levels. For the skin, many circadian changes have been investigated but few systematic studies comparing skin at different body sites have been reported. In this study we investigated facial and forearm skin circadian rhythms in eight healthy Caucasian women. Noninvasive methods were used to assess skin capacitance, sebum excretion, skin temperature, transepidermal water loss, and skin surface pH on fixed sites of the face and the volar forearm during a 48 h span under standardized environmental conditions. Using the cosinor or ANOVA methods, circadian rhythms could be detected for sebum excretion (face), transepidermal water loss (face and forearm), skin temperature (forearm), pH (face), and capacitance (forearm). No circadian rhythmicity was found for the other biophysical parameters. In addition to the 24 h rhythm component, rhythms with periods of 8 h were found for sebum excretion, of 8 and 12 h for transepidermal water loss (face and forearm), and of 12 h for skin temperature (forearm). Our study confirms that rhythms of skin surface parameters are readily measurable and that these rhythms differ between different sites. Furthermore, we demonstrate for the first time that, for transepidermal water loss (face and forearm), sebum excretion, and skin temperature (forearm), in addition to circadian rhythms, ultradian and/or component rhythms can be detected.

Effects of the antiprogesterone steroid RU 486 during midluteal phase in normal women.

UNLABELLED: The antiprogesterone steroid RU 486 (17 beta-hydroxy-11 beta-4-dimethyl-aminophenyl)17 alpha(1-propynyl)estra-4,9-dien-3-one) was given orally to 32 normally cycling women for 4 days, starting on the fourth day of the luteal phase. Uterine bleeding occurred on the third day of RU 486 administration in all 14 women treated with 100 mg/day, in 7 of the 8 women treated with 50 mg, and in 8 of 10 women receiving 25 mg/day. Premature luteal regression induced by RU 486 occurred in 8 women treated with 100 mg/day, in 3 treated with 50 mg, and in 2 receiving 25 mg/day. Plasma LH was measured every 15 min from 0800-1200 h for 5 days in 17 women. Mean LH levels decreased and pulsatile release disappeared in 7 of the 8 women treated with 100 mg, in 2 of 4 receiving 50 mg, and in 1 of 5 treated with 25 mg. RU 486 had no effect when given to 5 women with anovulatory cycles for 4 days starting on day 18 of the cycle. IN CONCLUSION: 1) RU 486, given to normally cycling women at midluteal phase, provokes uterine bleeding. 2) This effect occurs whether or not luteal regression is induced by the compound, indicating that RU 486 acts directly upon the endometrial tissue, very likely at the progesterone receptor level. 3) The drug may impair simultaneously or separately luteal function and gonadotropin secretion in a dose-dependent manner. 4) The lack of antiglucocorticosteroid activity, at the dosage of 100 mg/day, suggests that RU 486 may be useful for fertility control.

PIP: The antiprogesterone steroid RU 486 (17beta-hydroxy-11beta-4-dimethyl-aminophenyl)17alpha(1-propynyl)estra-4,9-dien-3-one) was given orally to 32 normally cycling women for 4 days, starting on the 4th day of the luteal phase. Uterine bleeding occurred on the 3rd day of RU 486 administration in all 14 women treated with 100 mg/day, in 7 of the 8 women treated with 50 mg and in 8 of 10 women receiving 25 mg/day. Premature luteal regression induced by RU 486 occurred in 8 women treated with 100 mg/day, in 3 treated with 50 mg, and in 2 receiving 25 mg/day. Plasma LH was measured every 15 minutes from 0800-1200 hours for 5 days in 17 women. Mean LH levels decreased and pulsatile release disappeared in 7 of 8 women treated with 100 mg, in 2 of 4 women receiving 50 mg, and in 1 of 5 treated with 25 mg. RU 486 had no effect when given to 5 women with anovulatory cycles for 4 days starting on day 18 of the cycle. The following were conclusions drawn. 1) RU 486, given to normally cycling women at midluteal phase, provokes uterine bleeding. 2) This effect occurs whether or not luteal regression is induced by the compound, indicating that RU 486 acts directly on the endometrial tissue, very likely at the progesterone receptor level. 3) The drug may impair simultaneously or separately luteal function and gonadotropin secretion in a dose-dependent manner. 4) The lack of antiglucocorticosteroid activity, at a dosage of 100 mg/day, suggests that RU 486 may be useful for fertility control.

Timing optimizes sustained-release indomethacin treatment of osteoarthritis.

Chronopharmacologic studies of indomethacin have indicated that time of dosing influences tolerance and effectiveness. A double-blind, crossover chronotherapeutic trial was undertaken in 66 subjects with osteoarthritis of the hip or knee who were treated with an indomethacin sustained-release (ISR) oral preparation once a day. Varying the ISR dosing time resulted in a quadrupling of tolerance and a doubling of analgesic effectiveness. Three dosing times (8 a.m., noon, and 8 p.m.), each tested during 1-wk spans and randomized for sequencing, were compared in each subject. Subjects self-rated pain intensity every other hour before (1 to 2 days) and during each week of treatment. Morning dosing was associated with a 32% incidence of undesirable effects, whereas the comparable rate was 7% for evening dosing. Ninety-five percent of the subjects reported increased drug effectiveness with a change in ISR ingestion time. The time of dosing that resulted in optimal effectiveness differed among subjects. This was explainable by large interindividual differences in the circadian variation of self-rated pain intensity. Evening dosing was most effective in subjects with predominantly nocturnal or morning pain; conversely, morning or noon dosing was most effective in subjects with greater afternoon or evening pain. The differences that resulted from varying the timing of the identical ISR dose in the same subject greatly exceeded those reported for other nonsteroidal anti-inflammatory drugs.

Effects of cyclic (nocturnal) total parenteral nutrition and continuous enteral nutrition on circadian rhythms of blood lipids, lipoproteins and apolipoproteins in humans.

The aim of the present study was to investigate the occurrence and characteristics (acrophase, amplitude) of circadian rhythms of serum total cholesterol, free-fatty acids (FFA), triglycerides, lipoproteins (HDL-, LDL-, and VLDL-cholesterol), apolipoproteins A and B, glucose and total proteins in hospitalized patients fed with 12 h nocturnal total parenteral nutrition (TPN) (from 8 PM to 8 AM) including lipids, patients fed with continuous enteral nutrition over 24 h daily spans, and patients eating 3 meals a day serving as controls. All the subjects were synchronized with diurnal activity and nocturnal rest in the hospital routine. The results showed the following: 1) circadian rhythms of total cholesterol, triglycerides, FFA, HDL-, LDL-cholesterol, apolipoprotein A and total proteins were detected in both TPN patients and controls, rhythms of apolipoprotein B and glucose in TPN patients only; in enteral nutrition patients, rhythms were detected for total proteins, glucose and triglycerides only; 2) a significant shift in triglyceride and FFA acrophases was observed in TPN patients, as compared with controls; 3) 24 h mean of both triglyceride and cholesterol concentrations remained unchanged after one month, in both TPN and enteral nutrition patients. The present approach, by extending results of previous investigations, leads one to conclude that, on both a metabolic and a chronobiological basis, cyclic nocturnal TPN is well-tolerated.

Circadian changes in psychologic effects of ethanol.

Six healthy human males (aged 22 to 26 years) synchronized with diurnal activity from 0700 hours to midnight and nocturnal rest, volunteered to document changes in psychologic variables resulting from ethylalcohol ingestion (ethanol 0.67 g/kg of body weight). For each subject four separate tests were performed at least 1 week apart at 0700, 1100, 1900, and 2300 hours in randomized order, with measurements taken before and 15, 30, 60, 90, 120, 140 minutes postingestion and thereafter at 4-hour intervals during a 24- to 36-hour period. Subjects fasted for 12 hours preceding ethanol ingestion time and for 8 hours thereafter. Self-rated inebreity (visual analogue scale) was greatest after ingestion at 2300 hours and lowest after ingestion at 1100 hours. Both speed to perform random number addition and eye-hand skill tests were slowest after ingestion at 2300 hours. However, changes observed for self-rated physical vigor, tempo, hand-grip strength, and systolic blood pressure did not appear to be ethanol ingestion time dependent. Validated ethanol ingestion time-dependent effects including those of oral temperature were not related to changes in the drug pharmacokinetics.

Circadian changes of drug disposition in man.

Circadian (approximately equal to 24 hours) and other endogenous biological rhythms, detectable at all levels of organisation, constitute a temporal structure in all animal species, including man. Circadian, circannual, and other rhythmic changes in biological susceptibility and response of organisms to a large variety of physical and chemical agents, including medications and foods, are rather common phenomena. A better understanding of periodic and thus predictable changes in drug effects can be attained through consideration of three complementary concepts: the chronopharmacokinetics of a drug (rhythmic changes in its pharmacokinetics), the chronesthesy (rhythmic changes in susceptibility of target biosystems to the drug), and the chronergy (the drug-integrated overall effects). The chronopharmacokinetics of many drugs have been evaluated in man including sodium salicylate, aspirin, indomethacin, paracetamol (acetaminophen), phenacetin, amidopyrine, theophylline, digitalis, propranolol, clorazepate, hexobarbitone (hexobarbital), lithium, phenytoin (diphenylhydantoin), nortriptyline, ethanol, erythromycin, ampicillin, sulfasymazine, sulphanilamide, cisplatin (cis-diammine dichloroplatinum), d-xylose, ferrous sulphate, potassium chloride, hydrocortisone and prednisolone, among others. The roles presumably played by circadian rhythms in drug metabolising liver enzymes and kidney function are summarized, and the practical implications of chronopharmacokinetics, aiming both to improve in a quantitative manner the metabolic fate of a drug and its effectiveness, are discussed.

Circadian changes in the pharmacokinetics of oral ketoprofen.

Several investigations which have taken treatment time into account have shown that the pharmacokinetic parameters, the therapeutic efficacy and even the toxicity of a large number of products may vary according to the administration schedule. The present study was carried out in order to evaluate any circadian changes in pharmacokinetic parameters of ketoprofen, a new non-steroidal anti-inflammatory drug (NSAID). This randomised crossover study consisted of a single oral dose of ketoprofen 100mg administered to 8 healthy male volunteers, mean age 27.2 years, at 07.00 hours, 13.00 hours, 19.00 hours or 01.00 hours in 4 study periods during the first 3 months of the year. The order of administration was randomised, with each subject acting as his own control. A total of 14 blood and 4 urine samples were taken over a 12-hour period. The peak plasma concentration was twice as high after drug administration at 07.00 hours (13.4 +/- 1 mg/L) than after other administration times (13.00 hours: 6.9 +/- 1; 19.00 hours: 7.2 +/- 0.7; 01.00 hours: 6.3 +/- 0.5 mg/L) [p less than 0.001]. The time to reach peak concentration was much longer after drug administration at 01.00 hours (135 +/- 16.7 min) than at 07.00 (73.1 +/- 14.1 min), 13.00 (75 +/- 16.5 min) or 19.00 hours (82.5 +/- 12.7 min) [p less than 0.05]. The lag time was significantly longer at 01.00 hours than at 13.00 hours (p less than 0.01). The absorption rate constant after treatment at 01.00 hours was less than at the other times of administration (p less than 0.05). The bodyweight-corrected area under the curve (AUC0-12) was greater after 07.00 hours than after 13.00 (p less than 0.01) or 19.00 hours (p less than 0.05) and greater after 01.00 hours than after 13.00 hours (p less than 0.05). The elimination half-life was significantly longer after administration at 01.00 hours than after 19.00 hours (p less than 0.05), while the total clearance was lowest at 07.00 hours. Cosinor analysis demonstrated statistically significant circadian rhythms for all pharmacokinetic parameters described above. The amount of ketoprofen eliminated in the urine was delayed, and was significantly greater after the administration at 01.00 hours than 07.00 hours or 19.00 hours (p less than 0.01). The relationship between absorption, diffusion and/or elimination mechanisms of the drug are discussed.

Circannual and circadian rhythms in the concentration of corticosterone in the plasma of the edible frog (Rana esculenta L.).

For a period of 21 months between May 1974 and September 1976, circadian variations in the plasma concentration of corticosterone were studied by competitive protein-binding techniques in mature male and female edible frogs living in their natural environment. Blood samples were taken from 8 to 12 frogs six times daily and conventional and cosinor methods were used for statistical analysis. Circadian rhythms were not detected during February and March (time of hibernation). Circannual rhythms were detected in three parameters of the circadian rhythm. The mean concentration of corticosterone over a 24 h period (24 h mean) reached a peak on 1 May (between 15 April and 15 May; 95% limits of confidence); the annual mean value of the 24 h means was 1.97 +/- 0.25 (S.E.M.) microgram/100 ml, with an amplitude of 0.66 microgram/100 ml (0.53--0.79 microgram/100 ml; 95% limits of confidence). Circadian variations in the concentration of corticosterone were largest in May (peak of reproductive activity). The times at which the peak concentration of corticosterone occurred showed circannual variations: peak values were detected around 24.00 h in May, 19.00 h in July and 08.00 h in November. Both circadian and circannual variations have therefore been demonstrated in an endocrine function of an amphibian in its natural habitat.

Seasonal rhythms of plasma gonadotrophins: their persistence in elderly men and women.

Circannual changes of immunoreactive LH and FSH were documented on a circadian basis in January, March, June and October in four groups of subjects: seven young men, six elderly men, six elderly women and six men and women suffering from senile dementia. The sampling was serially dependent only for the young men and the core subgroups of elderly men and elderly women. A circadian rhythm for FSH was not detected in any group of subjects during any of the sampling sessions, whereas a circadian rhythm for LH was detected twice (June and October) in young men, once (October) in elderly demented patients, and not at all in the groups of elderly men and women. Both 24-h and yearly mean levels of gonadotrophins were higher in elderly subjects (two-to 25-fold according to the hormone, sex and season) than in young men. Circannual rhythms of plasma LH with large amplitudes were validated by the cosinor method, with an acrophase located in April or May. A circannual rhythm of plasma FSH was validated only in young men, with an acrophase in October. The persistence of a circannual rhythm of plasma LH with large amplitude in elderly subjects, associated with high mean levels of the hormone, especially in elderly women, suggests that this bioperiodicity of the pituitary gland is independent of gonadal function.

Differences in the seasonal rhythmicity of plasma prolactin in elderly human subjects: detection in women but not in men.

Effects of age, sex and mental condition on the circadian and circannual rhythmicity of plasma prolactin in human subjects were investigated. Circannual changes were recorded on a circadian basis in January, March, June and October in four groups of subjects: seven young men, six elderly men, six elderly women and six senile demented patients (two men and four women). Blood samples were drawn every 4 h over a 24-h period at the four sampling sessions. Circadian rhythms of the hormone were validated in all groups and at all sampling sessions except twice in elderly demented subjects. The 24-h mean levels of prolactin in plasma were approximately the same in young and elderly subjects. The circadian acrophases were most often located in the vicinity of 02.00-04.00 h. The circannual rhythmicity of the hormone showed a sex difference; the rhythm was not validated in either young or elderly men but was detected in the groups of elderly women and elderly demented patients (mainly women). The acrophases were located in May. This paper strongly suggests a sex difference in the circannual rhythmicity of plasma prolactin levels in elderly subjects.

The genetic background of circadian and ultradian rhythm patterns of 17-hydroxycorticosteroids: a cross-twin study.

Circadian and ultradian rhythms in urinary excretion of 17-hydroxycorticosteroids were documented individually during an 8-day span in two pairs of young male twins. Studies were performed once at the age of 6 years for dizygotic twins and twice at the ages of 4.3 and 10.3 years for monozygotic twins. Four different methods were used for time-series analyses: chronograms (raw data), best-fitting curves resulting from cosinor analyses, power spectra and correlations of time-qualified data. Estimates of rhythm parameters (prominent periods, acrophases, etc.) as well as shapes of curves were closer in mono- than in dizygotic twins. Both similarities and small differences in rhythm characteristics of monozygotic twins were detected at both ages considered.

Hypothalamo-pituitary regulation of thyrotrophin secretion in chronically catheterized Brattleboro rats.

Plasma TSH rhythms were measured in Brattleboro (DI) and control Long-Evans (LE) rats with an intracardiac catheter allowing repeated sampling in conscious unstressed animals. The TSH response to thyrotrophin-releasing hormone (TRH; 500 ng/100 g body weight) was also determined. Finally, hypothalamic and pancreatic TRH concentrations and TRH-degrading activity (TRH-DA) were measured by specific radioimmunoassay. Long-Evans rats had a 24-h rhythm with a major modulatory 8-h component. In DI rats, only the 24-h rhythm was detected. The mean 24-h rhythm-adjusted mean TSH level was higher in DI than in LE rats (1.38 +/- 0.05 and 1.14 +/- 0.06 micrograms/l respectively, P less than 0.01). The peak TSH response to TRH was significantly increased in DI rats while the pituitary concentration of TSH was also higher (0.93 +/- 0.09 vs 0.39 +/- 0.06 micrograms/mg wet weight in LE, P less than 0.001). Hypothalamic TRH and TRH-DA were similar in both strains. The response to propylthiouracil-induced hypothyroidism was identical in both strains. We conclude that DI rats have a normal pituitary sensitivity to tri-iodothyronine but a central dysfunction in the pituitary environment leading to some alterations of TSH secretion.

Adrenocortical hormones, ageing and mental condition: seasonal and circadian rhythms of plasma 18-hydroxy-11-deoxycorticosterone, total and free cortisol and urinary corticosteroids.

The circannual rhythms of plasma 18-hydroxy-11-deoxycorticosterone (18-OH-DOC), total and free cortisol have been documented on a circadian basis in January, March, June and October in seven young men (24 years old), six elderly men, six elderly women and six elderly demented subjects, both men and women, in their eighties. Blood samples were drawn every 4 h over a 24-h period at each sampling session and urine samples were collected at 4-h intervals only from the young men. A circadian rhythm of 17-hydroxy-corticosteroids (17-OH-CS), 17-ketosteroids (17-KS), urinary free cortisol and 18-OH-DOC was defined for each of the four seasons with stable acrophases throughout the year and the same excretory profiles. A circannual rhythm was validated in young men for 17-OH-CS, urinary free cortisol and 18-OH-DOC but not for 17-KS. A circadian rhythm of plasma free cortisol, the active form of the hormone, plasma total cortisol and plasma 18-OH-DOC was validated in all groups and at all the seasons at which samples were taken. The secretory profiles of 18-OH-DOC, free and total cortisol were very similar, with no differences attributable to age, sex or mental condition except for the levels of plasma free cortisol and 18-OH-DOC which were higher and lower respectively in the elderly subjects. Whereas a circannual rhythm of plasma 18-OH-DOC was validated for all groups, a circannual rhythm of both free and total cortisol in the plasma was validated in young men but not in any group of elderly subjects. This loss of the circannual rhythmicity of cortisol in the elderly may reflect the decrease with age of the capacity to adapt to seasonal external factors.

Adrenal circadian system in young and elderly human subjects: a comparative study.

Circadian changes in plasma 18-hydroxy-11-deoxycorticosterone (18-OH-DOC), total and unbound cortisol were studied in four groups: seven healthy young men, six elderly men, six elderly women and six elderly demented patients of both sexes. The daily activities of the subjects were synchronous; blood samples were taken every 4 h and 4 hourly urine samples were collected only from the young men. A circadian rhythm was defined for plasma 18-OH-DOC, total and unbound cortisol in all groups; the secretory patterns of these steroids were parallel, as were the profiles of urinary 18-OH-DOC and unconjugated cortisol. When compared with respect to sex, the 24-h mean level of total cortisol was higher in women; that of unbound cortisol was higher in the three groups of elderly patients than in the young men. No major changes in plasma steroids were observed between elderly demented patients (mainly women) and healthy elderly women. The phasing of total and unbound cortisol showed no major modifications with age, sex or senile dementia. Acrophases of 18-OH-DOC were earlier in elderly patients than in young men. Amplitudes were not modified with sex in elderly patients but were always lower in the demented patients. A circadian rhythm was defined for 18-OH-DOC, unconjugated cortisol, 17-hydroxycorticosteroids (17-OH-CS) and 17-ketosteroids in the urine of the young men. The acrophases of 18-OH-DOC and unbound cortisol were close, as were those of 17-OH-CS and 17-ketosteroids. The lag was short between the acrophases of 18-OH-DOC in plasma and urine and between those of plasma unbound cortisol and urinary unconjugated cortisol; it was much larger between the acrophases of plasma total cortisol and 17-OH-CS. Thus, the process of ageing, and the possible alterations in the central nervous system which are often seen in normal ageing, induced no major modifications in the temporal organization of adrenocortical function, even in subjects who were very advanced in age.

Age- and mental health-related circadian rhythms of plasma levels of melatonin, prolactin, luteinizing hormone and follicle-stimulating hormone in man.

Circadian changes in plasma levels of melatonin, prolactin, LH and FSH were studied in four groups: seven healthy young men, six elderly men, six elderly women and six elderly demented patients (two men and four women). The daily activities of the subjects were synchronous and blood samples were taken every 4 h. The 24-h mean concentrations of prolactin in plasma were the same in all groups, whereas those of LH and FSh were twice as high in the elderly as in the young men and eight and 23 times higher respectively in the elderly women. The 24-h mean plasma levels of melatonin in the elderly were half those in the young, but were not influenced by the sex or mental condition of the subjects. A statistically significant circadian rhythm for melatonin was defined in the four groups, for prolactin in all groups except the elderly men and for LH only in the demented patients and in the young men. No circadian rhythm could be detected for FSH in any of the four groups. The acrophases of melatonin and prolactin ranged between 02.30 and 04.00 h, those of LH (when a rhythm was validated) clustered around 01.00 h. The circadian rhythms of plasma levels of melatonin, prolactin and LH are not modified in old age nor in dementia. A positive correlation has been demonstrated in young men between melatonin and LH and between melatonin and prolactin, but no such correlation could be found in the elderly.