Ethical principles and standards for the conduct of human and animal biological rhythm research

Most research papers published in Chronobiology International report the findings of investigations conducted on laboratory animals and human beings. The Journal, its editors and the publication committee endorse the compliance of investigators to the principles of the Declaration of Helsinki of the World Medical Association relating to the conduct of ethical research on human beings and the Guide for the Care and Use of Laboratory Animals of the Institute for Laboratory Animal Research of the National Research Council relating to the conduct of ethical research on laboratory and other animals. Chronobiology International requires that submitted manuscripts reporting the findings of human and animal research conform to the respective policy and mandates of the Declaration of Helsinki and the Guide for the Care and Use of Laboratory Animals. The peer review of manuscripts will thus include judgment of whether or not the involved research methods conform to the standards of good research practice. This article outlines the basic expectations for the methods of human and animal biological rhythm research, both from the perspective of the fundamental criteria necessary for quality chronobiology investigation and from the perspective of humane and ethical research on human beings and animals.

Ethics, standards, and procedures of animal and human chronobiology research

The majority of research papers published in Chronobiology International report the findings of investigations conducted on laboratory animals and human beings. The editors and the readers of the journal expect the authors of submitted manuscripts to have made an important contribution to biological rhythm and related research through the ethical conduct of investigations and unbiased and accurate reporting of findings. Authors of scientific papers are required to disclose any potential conflict of interest. The journal accepts only papers that are original work, no part of which has been submitted for publication elsewhere, except as brief abstracts. The journal and its editors endorse the compliance of investigators to the principles of the Declaration of Helsinki of the World Medical Association, which relate to the conduct of ethical research on human beings, and the Guide for the Care and Use of Laboratory Animals of the Institute for Laboratory Animal Research of the National Research Council, which relate to the conduct of ethical research on laboratory and other animals. The peer review of manuscripts by Chronobiology International thus includes judgment as to whether or not the investigative methods conform to the standards of good research practice. This article updates the ethical policies, standards, and procedures for manuscripts submitted to Chronobiology International that involve human and animal biological rhythm research, both from the perspective of the criteria of quality chronobiology investigation and from the perspective of humane and ethical research on human beings and animals.

Nocturnal excretion of 6-sulphatoxymelatonin in children and adolescents with autistic disorder

BACKGROUND

Many studies in autistic disorder report sleep problems and altered circadian rhythms, suggesting abnormalities in melatonin physiology. Additionally, melatonin, a pineal gland hormone produced from serotonin, is of special interest in autistic disorder given reported alterations in central and peripheral serotonin neurobiology.

METHODS

Nocturnal urinary excretion of 6-sulphatoxymelatonin was measured by radioimmunoassay in groups of children and adolescents with autistic disorder (n = 49) and normal control individuals (n = 88) matched on age, sex, and Tanner stage of puberty.

RESULTS

Nocturnal 6-sulphatoxymelatonin excretion rate was significantly and substantially lower in patients with autism than in normal controls (mean +/- SEM, .75 +/- .11 vs. 1.80 +/- .17 microg/hr, p =.0001), and was significantly negatively correlated with severity of autistic impairments in verbal communication and play (p < .05).

CONCLUSIONS

These findings indicate clearly that nocturnal production of melatonin is reduced in autism. Further research is warranted in order to understand the mechanisms underlying the lower melatonin production, to assess the impact of altered melatonin on the pathophysiology and behavioral expression of autistic disorder, and to determine the utility of melatonin administration in individuals with autism.

Reproducibility of the circadian rhythms of serum cortisol and melatonin in healthy subjects: a study of three different 24-h cycles over six weeks

Plasma melatonin and cortisol are characterized by a marked circadian rhythm, but little information is available about the reproducibility and stability of these rhythms over several weeks in the same subjects. This study examined the characteristics of these rhythms in 31 healthy human subjects 20 to 30 years of age. They were synchronized with a diurnal activity from 0800 to 2300 and nocturnal rest. They participated in three 24-hour sessions (S1, S2, and S3): S2 took place two weeks after S1 and S3 4 weeks after S2. Blood samples were taken during each session at 3-hour intervals from 1100 to 2000 and hourly from 2200 to 0800. Comparison of the circadian rhythms between groups used repeated measures 2-way ANOVA, the cosinor method, and Bingham's test. Intraindividual variations were compared by the cosinor method and Bingham's test. The groups did not differ, but a slight difference in the amplitude or acrophase of individual circadian rhythms was observed in 5 of 31 subjects for melatonin and 1 of 31 for cortisol. The circadian means did not differ over the three sessions. These results show that the circadian profile of cortisol and melatonin are highly reproducible over a six-week period, in both individuals and groups. Our study clearly shows that these hormones can be considered to be stable markers of the circadian time structure and therefore useful tools to validate rhythms' synchronisation of human subjects.

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.

Ramadan fasting alters endocrine and neuroendocrine circadian patterns. Meal-time as a synchronizer in humans?

Muslims must refrain from eating, drinking, smoking, and sexual relations from sunrise to sunset during the month of Ramadan. Serum concentrations of melatonin, steroid hormones (cortisol, testosterone), pituitary hormones (prolactin, LH, FSH, GH, TSH) and thyroid hormones (free thyroxin and free triiodothyronine) were documented around the clock at six 4-hourly intervals before Ramadan began and on the twenty-third day of Ramadan (daytime fasting). Time series were analysed with repeated measures ANOVA. Statistically significant differences were found in some variables: the nocturnal peak of melatonin was diminished and may have been delayed; there was a shift in the onset of cortisol and testosterone secretion; the evening peak of prolactin was enhanced, FSH and GH rhythmic patterns were affected little or not at all by Ramadan fasting and only the serum TSH rhythm was blunted over the test time span. These data show that daytime fasting, modifications in sleep schedule and psychological and social habits during Ramadan induce changes in the rhythmic pattern of a number of hormonal variables.

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.

Treatment of Cushing's disease by O,p'DDD. Survey of 62 cases

In a study of nonsurgical therapy of Cushing's disease, 62 patients received O,p'-dichlorodiphenyldichloroethane (O,p'DDD), 16 of whom also received cobalt irradiation of the pituitary. After an initial treatment period averaging eight months, a remission of the disease was obtained in 38 of the 46 patients given O,p'DDD alone and in all patients who received drug combined with radiation. Although 60 per cent of these patients subsequently relapsed, additional courses of drug or radiation therapy were usually effective, and 63 per cent of the entire group of patients have so far been kept under control without adrenalectomy. (Forty patients have been followed for at least two years after the initial course of treatment.). O,p'DDD produced little gastrointestinal discomfort; an increased serum cholesterol was the main side effect. This drug allows long-term medical management of Cushings disease in most cases. Whether the combination of O'p'DDD with pituitary radiation is the best therapy has not been established.

Evidence of prooxidant and antioxidant action of melatonin on human liver cell line HepG2

The aim of this study was to evaluate melatonin cytotoxicity by measuring its effects on various cellular targets. Cell viability, intracellular reduced glutathione (GSH) level, and reactive oxygen species (ROS) production were assessed in the human liver cell line (HepG2), after incubation with increasing melatonin concentrations (0.1-10,000 microM). The incubation times tested were 24, 72, and 96 h for cell viability and intracellular GSH level, and 15 and 45 minutes for ROS production. Cellular target evaluations were possible in living cells by means of a new microplate cytofluorimeter. This technology was suitable for the assessment of cell viability, GSH level, and ROS overproduction with, respectively, neutral red, monochlorobimane (mBCl), and 2',7'-dichlorofluorescin diacetate (DCFH-DA) fluorescent probes. At the lowest melatonin concentrations (0.1-10 microM) and for a relatively short incubation time (24 h), the antioxidant effect of melatonin was revealed by an increased intracellular GSH level, associated to cell viability improvement. In contrast, after longer incubation (96 h), cell viability significantly decreased with these lowest melatonin concentrations (0.1-10 microM). Moreover, high melatonin concentrations (1,000-10,000 microM) induced GSH depletion. This oxidative stress is associated with ROS overproduction from 10 microM after only 15 minutes of incubation. This dual effect is strong evidence that, in vitro, melatonin can be both antioxidant and prooxidant on the human liver cell line, depending on the concentration and incubation time.

Human aging and melatonin. Clinical relevance

Melatonin is a hormone produced mainly by the pineal gland and secreted primarily at night, when it reaches levels 10 times higher than those present in the daytime. The highest melatonin levels are found in children younger than 4 yr; thereafter melatonin levels begin to decline with age. As a chronobiotic, melatonin acts on sleep by phase-advancing or delaying the sleep--wake cycle so that sleep onset occurs earlier or later than usual. Beneficial effects of melatonin have been observed in delayed and advanced sleep phase syndromes. These effects depend on the time that the hormone is administered. Melatonin is also used for jet lag and has been tried in shift workers and night workers to re-entrain their desynchronized rhythms. Melatonin also has free radical-scavenging properties that have primarily been observed in vitro at pharmacological concentrations.

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.

Patterns of plasma melatonin with ageing and mental condition: stability of nyctohemeral rhythms and differences in seasonal variations

Effects of ageing and mental condition on the nyctohemeral and seasonal rhythms of plasma melatonin in human subjects were investigated. Four groups of subjects were formed for a transverse study: 7 healthy young men (24 years), 6 elderly women, 6 elderly men and 6 elderly patients (2 men and 4 women) suffering from senile dementia (70-80 years). The subjects were synchronized. Blood samples were taken every 4 h during 24 h in January, March, June and October. In comparison to young men, the plasma levels of melatonin were markedly decreased (by about one half) in elderly subjects without any difference according to sex or mental condition. Nyctohemeral rhythms of the hormone were validated in all groups and at all sampling sessions. The nyctohemeral acrophases were remarkably stable (around 03.00 h) whatever the season, age or sex. A seasonal variation was found in all groups (except elderly women) with differences between young and elderly subjects: plasma melatonin levels were significantly lower in January than in June in young men, whereas in elderly subjects they were significantly lower in October than in January/March. No significant difference was observed in mesor, amplitude or acrophase of nyctohemeral and seasonal rhythms of plasma melatonin in patients with senile dementia when compared with healthy elderly subjects. The stability of the nyctohemeral peak time whatever the age group or season as opposed to the differences in the seasonal pattern of plasma melatonin according to the age groups raises the problems of both outdoor photoperiod and ageing in ruling the secretion of melatonin in man.

Circadian and circannual rhythms in plasma hormones and other variables of five healthy young human males

Every other month (plasma) and every month (urine) circadian rhythms were documented during the course of 14 months. Annual changes were validated in the 24 h mean of: plasma FSH (annual crest time: February), LH (March), thyroxine (September), cortisol (February), renin activity (April), testosterone (October), urinary 17-hydroxycorticosteroids (March), aldosterone (March), potassium (May) as well as sexual activity (September) [self-recorded daily]. Plasma prolactin did not show an annual variation. In addition, annual changes in the circadian acrophase (crest time location in the 24 h scale) occurred for some of the documented variables: plasma thyroxine, cortisol, renin activity, testosterone, urinary aldosterone and potassium.

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.

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.

Differences between young and elderly subjects in seasonal and circadian variations of total plasma proteins and blood volume as reflected by hemoglobin, hematocrit, and erythrocyte counts

Circadian and seasonal rhythms in total plasma proteins were documented in healthy young men (around 24 years old), and in elderly subjects (both sexes), including senile-dementia patients in their eighties. The concentration of plasma proteins within a given group changed predictably (7-13%), depending on the hour of sampling and the season. Concentrations decreased noticeably around 04:00 h, then peaked around 08:00 h (shortly after waking). The 24-h mean concentrations of total plasma proteins were lower in the elderly groups than in the young men. But the seasonal variations of the 24-h mean values were strikingly larger in the elderly groups (7-8 g/L) than in the young men (2-5 g/L). Moreover, the circadian profiles of plasma proteins differed from the profiles of hematocrit, hemoglobin, and erythrocyte counts. Evidently, circadian variations of blood volume may not be the only element accounting for the variations of plasma protein concentrations. We suggest that the rhythms in plasma protein concentrations be taken into account when reference values are set. Circadian and seasonal variations in plasma proteins may also significantly affect the transport and binding of drugs, especially in the aged.

Day and nighttime excretion of 6-sulphatoxymelatonin in adolescents and young adults with autistic disorder

BACKGROUND

Several reports indicate that nocturnal production of melatonin is reduced in autism. Our objective was to examine whether melatonin production is decreased during the whole 24-h cycle, whether the melatonin circadian rhythm is inverted, and whether the reduction in melatonin production is related to the severity of autistic behavioral impairments.

METHOD

Day and nighttime urinary excretion of 6-sulphatoxymelatonin (6-SM) was examined during a 24-h period in post-pubertal individuals with autism (N=43) and typically developing controls (N=26) matched for age, sex and pubertal stage.

RESULTS

Low 6-SM excretion (mean ± SEM) was observed in autism, both at daytime (0.16 ± 0.03 vs. 0.36 ± 0.05 μg/h, p<0.01), nighttime (0.52 ± 0.07 vs. 1.14 ± 0.23 μg/h, p<0.05), and during 24h (8.26 ± 1.27 vs. 18.00 ± 3.43 μg/24-h collection, p<0.001). Intra-individual nighttime-daytime differences (delta values) in 6-SM excretion were smaller in individuals with autism than in controls (0.36 ± 0.07 vs. 0.79 ± 0.23 μg/h, p<0.05). Nocturnal excretion of 6-SM was negatively correlated with autism severity in the overall level of verbal language (Spearman ρ=-0.30, p<0.05), imitative social play (Spearman ρ=-0.42, p<0.05), and repetitive use of objects (Spearman ρ=-0.36, p<0.05).

CONCLUSION

A deficit in melatonin production is present both at daytime and at nighttime in individuals with autism, particularly in the most severely affected individuals. These results highlight interest in potential therapeutic uses of melatonin in autistic disorder, especially in individuals with severe autistic impairment and/or low urinary 6-SM excretion.

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 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.

Age-related changes in both circadian and seasonal rhythms of rectal temperature with special reference to senile dementia of Alzheimer type

The biological rhythms of rectal temperature were documented in young (circadian variations) and elderly (circadian and seasonal variations) human subjects either in apparent good health or suffering from senile dementia of Alzheimer type (SDAT). All the subjects were synchronized. Data obtained showed a decrease of the body core temperature rhythm amplitude in the healthy elderly for each documented season but not in patients with SDAT. Seasonal variations in these rhythms were observed in these elderly groups of persons.

Chronobiological aspects of food intake and metabolism and their relevance on energy balance and weight regulation

Overweight and obesity are the result of a chronic positive energy balance, and therefore the only effective therapies are a diet which, on the long term, provides lower calories than the daily expended energy and exercise. Because nearly every physiological and biochemical function of the body shows circadian variations it can be suggested that also different chronobiological aspects of food intake, like time of day, meal frequency and regularity, and also circadian desynchronizations like in shift work may affect energy metabolism and weight regulation. The aim of this review is therefore to summarize and discuss studies that have addressed these issues in the past and to also provide an overview about circadian variations of selected aspects of metabolism, gut physiology and also factors that may influence overall energy regulation. The results show that a chronic desynchronization of the circadian system like in shift work and also sleep deprivation can favour the development of obesity. Also, regarding energy balance, a higher meal frequency and regular eating pattern seem to be more advantageous than taking the meals irregularly and seldom. Additional studies are required to conclude whether time of day-dependent food intake significantly influences weight regulation in humans.