Phase-Synchronization of Daily Motor Activities Can Reveal Differential Circadian Patterns

A patient diagnosed with seasonal affective disorder (SAD) carried out prospective ratings of depression weekly for nearly a decade. A winter peak of depression and benzodiazepine intake was documented. However, over the years, the depressive episodes shifted toward spring in an apparent free-running circannual rhythm (periodogram peaks at 53 and 55 weeks). This patient may have an underlying seasonal propensity to depression no longer precisely entrained to environmental cues. (Chronobiology International, 18(2), 309–313, 2001)     

Circannual Rhythm of Insulin Release and Hypoglycemic Effect of Tolbutamide Stimulus in Healthy Man

Four healthy non obese young volunteers were observed for a 24-hr period, every other month, over the course of one year. Tolbutamide was injected i.v. each day of the experiment every four hours. Tolbutamide-induced insulin secretion (T.I.I.S.) was evaluated by planimetrically measuring insulin areas above basal levels. Tolbutamide-induced hypoglycemic effect was evaluated by measuring the blood glucose difference between the Sth and 25th minute after the drug injection (δG 5′-25′). The macroscopic evaluation of T.I.I.S. and δG 5′-2S′(mean chronograms) permitted the detection of the existence of a circannual variation of both variables. In particular the maximum level of the blood glucose drop (δG 5-25) was registered in February.

Subsequently the quantification of the rhythm of T.I.I.S. was obtained by fitting a sine curve, according to the Cosinor method. The highest insulin release was confirmed in winter.

As previously documented, the existence of a statistically significant circadian rhythm of T.I.I.S. was confirmed in the morning, i.e. the same period of the day in which insulin-induced hypoglycemia occurs.     

Circannual Variation in the Incidence of Uterine Cervix Cancer

The impact of uterine cervix cancer (UCC) can be greatly reduced by regular vaginal examination and other preventive measures. With this aim, UCC screening programs had been developed and applied for several years in Mexico and elsewhere. One point still to be considered in such preventive programs is the possible circannual pattern in the morbidity or mortality of UCC. With the aim of identifying a possible circannual pattern of variation in the incidence of UCC, we analyzed the monthly totals of positive detected cases of UCC in the state of Nuevo León (Mexico) between 1978 and 1987. For eliminating bias due to the seasonal variation in the number of preventive check-ups, data were first expressed in percentage of tests done in the same month. The least-squares fit of a 1 -year cosine curve to the data reveals a statistically significant circannual pattern (p = 0.013), with a maximum of relative incidence detected in February. Results indicate UCC incidence higher than the yearly average during the winter, with secondary peaks in August and November. This pattern of variation is similar if one considers separately for analysis the relative incidence of type III, IV, or V UCC (relating to cases suggesting, highly suggesting, or concluding a malignant alteration, respectively). For evaluating the cost-effectiveness of the UCC screening campaign providing these data, the monthly totals of screening check-ups done over the same period were also analyzed. Results reveal a statistically significant circannual rhythm (p > 0.001), with a maximum detected in June. This timing seems to be related to the incidence of most common diseases in Mexico, such as giardiasis and salmonellosis, but not to the UCC morbidity rates. Health educational and screening campaigns for prevention of UCC and other major conditions should be timed during the year according to morbidity and mortality statistics, for which a circannual pattern of variation is documented herein.     

SEASONAL VARIATION IN THE EFFECT OF A FIXED DOSE OF HEPARIN ON ACTIVATED CLOTTING TIME IN PATIENTS PREPARED FOR OPEN-HEART SURGERY *

We investigated the effect of an injected bolus of 5 mg kg^- heparin at one circadian stage (08:30 to 11:00) on blood coagulation during different months of the year. Activated clotting times (ACTs) were assessed before and 5 min after heparin dosing to ensure extracorporeal circulation during open-heart surgery. The ACT data of 1083 presumably day-active Turkish patients (816 men and 267 women, mostly older than 46 years) who underwent coronary bypass surgery between 08:30 and 11:00 in the years from 1994 to 1997 were analyzed for annual rhythmicity. The ACT values obtained just before and 5 min after heparinization were subjected to cosinor analysis using a 365.25-day period to assess seasonality in basal ACT level and heparin effect. A small-amplitude annual rhythm with a wintertime peak was documented in the morning ACT in the group of 1083 patients. Rhythms of similar magnitude and staging were also detected in heparin effect on ACT in the 1083 patients and in subgroups categorized by gender. Circannual rhythmicity in the heparin effect on ACT was also documented in the elderly (≥ 45 years old), but not young (18-45 years old) patients. The annual mean effect of heparin on the ACT was statistically significantly greater in younger than older patients. The relatively low-amplitude circannual rhythm in heparin effect on ACT (∼10% of the annual mean) is not viewed as being meaningful in patient preparation for bypass surgery for the 5 mg kg^-1 level of heparin dosing. (Chronobiology International, 18(5), 865-873, 2001)     

Circannual Growth Rhythm in a Brown Alga,Pterygophora californica

A circannual rhythm was found in the kelp Pterygophora californica which forms a new blade with a free running period of 7 ? 8 months under constant conditions. Individual plants exposed to cycles of daylength with T = 12, 6, or 3 months performed 1, 2, or 4 growth cycles, respectively, in one calendar year showing the entrainment of the endogenous circannual rhythm. The annual growth cycle also followed a phase shift of the annual cycle of daylength (T = 12 months) by 3 or 6 months.     

Daily Increments of Light Hours Near Vernal Equinox Synchronize Circannual Testicular Cycle of Tropical Spotted Munia

In some long-lived organisms, particularly in tropical birds and migrants that spend part of the year close to the equator, endogenous circannual rhythms have been demonstrated in seasonal events like reproduction, molt, and migration. These, like the circadian rhythms, are expressed only in constant conditions of illumination with a periodicity deviating from 1 yr. If birds followed this periodicity, they would soon be out of phase with the annual calendar and perish and, therefore, they would need to be synchronized. However, almost nothing is known as to how synchronization is achieved in birds. Herein, with the help of a suitable model, viz., the tropical spotted munia and long-term experiments conducted in series over a 5-yr period, we provide direct evidence for the first time indicating that the segment of annual photocycle with maximal rate of increase prior to vernal equinox (approximately between mid-February and mid-March) synchronizes the circannual reproductive cycle with the monsoon period of ample food supply through a phase delay. Data also indicate, contrary to the prevalent view, that birds in the tropics can perceive minor changes in day-length, that birds respond to progressive changes in day-length as distinct from responding to fixed photoperiods of particular durations, and that birds can actually distinguish the quality of the environmental signal, viz., vernal equinox from early spring, or increasing days of spring from decreasing days of autumn. The underlying mechanisms, although yet to be identified, appear to involve a gonado-inhibitory rather than the conventional gonado-stimulatory response to increasing day-length. The photoperiodic responses of spotted munia are distinctly different from that of any “long-day” birds described thus far and do not conform to the prevalent “circadian coincidence” hypothesis of photoperiodism.     

Moulting cycles in European quail (Coturnix coturnix coturnix) under constant photoperiodic conditions

Abstract

Male and female European quails (Coturnix coturnix coturnix) were studied whilst being maintained in LD 12:12, at 20° C, for four years from birth. The birds exhibited the following phases: end of the first phase of the post‐juvenile moult, fattening and a period of nocturnal activity. Then sexual development is observed up to complete maturation at the age of four months. The second part of post juvenile moulting occurs towards the age of 5 to 6 months. During the following 6 months an important phase of reproduction is observed, thus completing their first year of life. The same sequence is repeated during the following years: a moult which lasts for 6 months in two (sometimes three) partial phases separated by episodes of reproduction; then an important period of reproduction (6 months) without moulting. The birds are capable of reproducing at all times except during moulting. The sequence of moulting begins each year in the same months as those for natural French populations. It thus seems that the annual periodicity and the organisation itself of the phenomenon of moulting is controlled in European quail by an endogenous circannual rhythm. In contrast, the natural cyclic expression of sexuality appears to be dependent on abiotic environmental and social factors.     

Endogenous gonadal,LH and molt rhythms in tropical stonechats: effect of pair bond on period,amplitude, and pattern of circannual cycles

To investigate the effects of reproduction and associated stimuli on the circannual cycles of African stonechats Saxicola torquata axillaris birds were held for 29 months in aviaries under a constant equatorial (12.25 h) photoperiod, either singly (10 females and 10 males) or in 10 male/female pairs. The birds of all 3 groups went through circannual cycles in gonadal size, plasma LH and molt, but groups differed with regard to actual reproductive performance. During the second cycle, only one of the singly-held females laid eggs and incubated. In constrast, in the paired females egg-laying and incubation occurred in all but one bird. About 50% of the clutches from paired females contained fertilized eggs confirming the expectation of behavioral differences between the paired and unpaired birds. However, despite differences in reproductive performance there were no differences in either circannual period or duration of reproductive phases. Moreover, there was no correlation between number of broods produced per season and circannual parameters of the paired females. Therefore, the temporal course and, particularly, the period during which reproduction is possible is rigidly determined by an endogenous program that is not influenced by reproductive performance. A rigid program of this kind may be advantageous in the tropics because it prevents prolongation of the breeding season in years with favourable conditions which in turn could jeopardize optimal timing of breeding in the following year and thus reduce lifetime reproductive success.     

Spore classification in the genera Bangia and Porphyra

Prior to the presentation by Drew (1956) of a system of classification for spores involved in the life histories of members of the Bangiophyceae, there was no uniform scheme. With the increased attention given to field and culture studies, particularly within the Bangiaceae, it is essential that a more comprehensive terminology be developed that considers experimental data on spore production. Drew's definition of Type II spores is re-examined and a system of classification based on cell fate and cell function as defined by studies on the photobiology of the Bangiaceae is proposed.