Showing papers in "Chronobiology International in 1989"

The dim light melatonin onset as a marker for circadian phase position.

Abstract: Masking is known to affect a variety of circadian rhythms, making it difficult to use them as reliable markers of circadian phase position. Melatonin may be unique in that it appears to be masked only by (bright) light. Sleep and activity do not appear to influence the melatonin rhythm. By measuring the onset of melatonin production, a clearly demarcated event, we can reliably assess circadian phase position, provided blood is sampled under dim light (the dim light melatonin onset, or DLMO). The DLMO has been useful in assessing the phase-shifting properties of bright light and in phase typing patients with chronobiologic disorders, such as winter depression.

Masking in Humans: The Problem and Some Attempts to Solve IT

Abstract: Different types of masking are discussed together with an account of the masking effect that the sleep-wake cycle exerts upon the circadian rhythms of body temperature and urinary excretion. The relative importance to masking of the several components of differences between sleeping and wakefulness are then assessed.Means to deal with the problem of masking fall into two major categories. These attempt to minimise masking effects by protocols such as constant routines or control days, and mathematical models which separate results obtained in the presence of masking influences into endogenous and exogenous components. (The problem of the extent to which masking influences can render the endogenous component of a rhythm an impure reflection of the internal oscillator is considered also.) These different techniques are compared with respect to their usefulness and assumptions.Finally, a brief speculation is given of the usefulness of masking.

Entrainment of A Free-Running Human with Bright Light?

Abstract: The case of a 40-year-old sighted woman with free-running sleep-wake and melatonin rhythms is presented. The subject was studied for 102 days. During the pre-treatment period, both the sleep-wake and melatonin rhythms had a period of 25.1 hr, similar to the average period of humans living in temporal isolation. Treatment consisted of bright artificial light exposure (2500 lx Vita-Lite) for 2 hr each day upon awakening. Clock time of light exposure was held constant for 6 days and then slowly advanced until the subject was arising at her desired time of day. The subject continued the light treatment at home and was able to live on a 24-hr day for the 30-day follow-up study. While other factors may be operating in this situation, it is possible that the light treatment caused the stabilization of the free-running rhythms, advancement to a normal phase and entrainment to the 24-hr day. We suspect that the tendency to free-run was related to sleep onsets that were abnormally delayed relative to the circadian phase response curve for light. By scheduling a 2-hr pulse of bright light each morning, this tendency to delay would be counteracted by light-induced advances, resulting in normal entrainment.

The pragmatic approach to masking.

Abstract: This paper advocates the use of a pragmatic approach to the problem of masking in real-life situations involving an abrupt change in the timing of sleep, i.e. shiftwork and “jet-lag” situations. Although “pure” chronobiological research has pointed to the importance of taking masking effects into account, the techniques that it has provided for doing so are extremely difficult to apply in real-life situations. The approach advocated here is based on Wever's pioneering work, and involves estimating the normative endogenous and exogenous components of the circadian rhythm in body temperature. These estimates are then used to: (a) simulate the results of shiftwork studies; and (b) to “remove” the exogenous component in “jet-lag” studies to allow analysis of the estimated endogenous component. The simulated curves obtained cross-correlated extremely highly with published night-shift temperature curves, while the “removal” of the exogenous component resulted in very similar findings to those obtained in tempor...

Entrainment of melatonin rhythms in rams by symmetrical light-dark cycles of different period length.

Abstract: The objective of this study was to investigate the entrainment of melatonin rhythms in rams using symmetrical light-dark cycles of different period length. Five groups of six He de France rams were kept in 12L: 12D for 7 weeks and then (i) 12L: 12D, (ii) 11L: 11D, (iii) 10L: 10D, (iv) 13L: 13D and (v) 14L: 14D for a further 3 weeks. Environmental factors other than the light dark cycle were not controlled. The onset and offset of the plasma melatonin rhythm in DD after 3 weeks of the respective light treatments was assessed for 48 hr, immediately after transferring to DD. The duration of secretion in DD was positively related to the length of the previous dark phase. The phase of the melatonin rhythm with respect to the anticipated dark phase suggested entrainment with no change in phase-relationship to the zeitgeber by 12L: 12D and 13L : 13D. Entrainment with a phase-delay or a phase-advance was apparent after 11L: 11D and 14L: 14D, but the individual rhythms were not all synchronized with respect to eac...

Variation in meals and sleep-activity patterns in aged subjects; its relevance to circadian rhythm studies.

Abstract: The study was performed upon a sample of aged and non-institutionalized subjects. Information was obtained by questionnaires and diaries on personal factors during a typical week. A random subset was subjected to a more detailed analysis of the composition of their meals. Results showed that increasing age was correlated with: a decreased day-by-day variability in an individual's time of retiring, rising and eating meals; earlier sleep times; increased frequency of daytime naps and nocturnal awakenings; and decreased physical activity. These results occurred both in subjects living alone and in those living with company. Day-by-day differences in the composition of meals tended to decrease with age. When differences between individuals were considered then these tended to increase with age. Some implications of these findings for studies of circadian rhythmicity in aged subjects--in whom the timing of circadian rhythms becomes more erratic and amplitude falls--are discussed.

Transition Between Advance and Delay Responses to Eastbound Transmeridian Flights

Abstract: In response to eastbound transmeridian flights, which result in zeitgeber phase advance shifts, adaptation of the circadian system to the new time zone by phase delays and advances are observed. The delay response to an advance zeitgeber shift has been called an antidromic response. For the shift at which the transition from an advance to an antidromic response occurs, the term critical shift is introduced.For the study of critical shifts, a flight experiment across nine time zones and numerical simulations of a van der Pol equation have been evaluated. The interest is focussed on the determination of a range for critical abrupt shifts. An abrupt shift means that the ensemble of zeitgebers including geophysical zeitgebers and the rest-activity cycle is shifted immediately in the new time zone. The range of critical advance shifts has been estimated to reach from + 7 to + 10 hr. In the literature, results were reported which would imply a much wider range. The discussion of these observations shows that th...

Ultradian rhythms in arousal--the problem of masking.

Abstract: Studies utilizing widely different experimental techniques provided evidence that there are spontaneous ultradian cycles in arousal during the waking state. These comprised of cyclic fluctuations between increased and decreased sleep propensity with a periodicity of about 1.5 hr. Being of relatively low amplitude, these cycles are vulnerable to masking effects by a variety of experimental conditions. Masking can be exerted by varying the tonic level of arousal, by coexisting slow ultradian components which are particularly prominent during the second half of the day, or by some specific experimental conditions. Furthermore, increased sleepiness was shown to enhance the slow ultradian components and suppress the 1.5-hr cycles in EEG indices of arousal on the one hand, and to emphasize the 1.5-hr cycles in motor activity and reaction time performance on the other hand. Much more attention should be paid to the problem of masking of ultradian cycles in arousal. Recognizing the sources and reasons for masking will advance our knowledge of the characteristics of these cycles and their function.

Resetting the annual cycle with timed daily injections of 5-hydroxytryptophan and L-dihydroxyphenylalanine in Syrian hamsters.

Abstract: Daily injections of dihydroxyphenylalanine (DOPA), a precursor for dopamine synthesis, given 12 hr after daily injections of 5-hydroxytryptophan (5-HTP), a serotonin precursor, induced uterine growth and increased serum thyroxine and luteinizing hormone (LH) concentrations in scotosensitive female hamsters maintained on short daylengths. On the other hand, daily injections of DOPA given at the same time as daily injections of 5-HTP reduced uterine weights and serum concentrations of thyroxine and LH in scotorefractory female hamsters. These results indicate that the endogenous mechanism controlling seasonality (scotosensitivity and scotorefractoriness) in the Syrian hamster may be reset by drugs that influence serotonergic and catecholaminergic activity. This seasonal mechanism might involve two circadian systems that undergo seasonal changes in their phase relations.

Masking in Invertebrates

Abstract: Masking effects are a common feature of daily rhythmicity in invertebrates; and, particularly with respect to activity/rest cycles in arthropods and mollusks, there are numerous examples of masking in response to external environmental stimuli. Internal masking, in which endogenous processes modulate circadian patterns, has also been documented in a few species. In general, however, because of the absence of appropriate experimental investigations on masking, the functional significance (in an ecological sense) of masking effects is not understood.

Effects of endurance exercise on nocturnal hormone concentrations in males.

Abstract: A preliminary study was conducted to evaluate the change in nocturnal concentrations of testosterone, luteinizing hormone, growth hormone, prolactin, thyroxine, and Cortisol following a control day (no exercise) and on a day in which exercise was performed. Exercise consisted of 90 min of cycling at 70% of each subject's maximal oxygen uptake. The exercise occurred from 1630 to 1800 hr on the exercise day while a comparable period of rest took place on the control day. Hormonal concentrations were evaluated at 2-hr intervals for a 12-hr period each night (2000–0800 hr). The subjects slept from 2255 (± 20 min [x ± S.E.M.]) until 0715 (± 15) during each night. All hormone responses were plotted and integrated for the 12-hr period. Analysis indicated that a significant augmentation of the prolactin and thyroxine responses occurred, while concurrently an attenuation of the growth hormone and Cortisol responses were observed. Contrastingly, no significant effects were found for the testosterone and luteinizing...

Circadian changes in stimulus threshold and in the effect of a local anaesthetic drug in human teeth: studies with an electronic pulptester.

Abstract: An electronic pulptester with constant testing current was used to study the stimulus threshold in human teeth of 28 healthy volunteers and the duration of local anaesthesia by articaine plus epinephrine in 55 patients with caries who underwent a filling therapy. In 21 out of the 28 volunteers, significant daily variations in stimulus threshold were detected by cosinor analysis. Acrophases, however, were scattered over the 24-hr scale. In patients, the local anaesthetic effect was studied at four different times of day (0800, 1100, 1400 and 1700 hr). The electronic device allowed one to accurately determine the time to peak effect (Tmax), duration of effect (Emax, time to return to baseline threshold (Tret) and the area under the time-effect curve (AUC) as a measure of the total local anaesthetic effect. Significant diurnal variations in AUC and Emax were found in 36 patients with the 0.8 ml dose, with peak and trough values at 1400 and 1700 hr, respectively. No differences in effect were found with the low dose of 0.4 ml applied to 19 patients either at 1400 or 1700 hr giving evidence for a circadian phase-dependency in the dose-response relationship of a local anaesthetic drug. The results clearly demonstrate that this electronic device is suitable for exact evaluation of circadian changes in local anaesthetic effects. Under drug-free control conditions, however, the low stimulus frequency of 5 Hz of this device obviously does not allow to discriminate between stimuli modified by pain perception and/or alertness.

Meal scheduling modulation of circadian rhythm of phototactic behaviour in cave dwelling fish.

Abstract: Phototactic responses of three groups, each of 16 cave fishes, were observed at 4-hr intervals beginning at 0900, following S days of acclimation inside specially designed aquaria. The latter consisted of two parts, a photic zone and an aphotic zone. The first group of fishes were fed ad libitum, while the second and third group of fishes were fed with minced mutton and/or liver delivered in the photic zone between 0700–1100, and in the aphotic zone between 1900–2100. The percentage of fishes present in the photic zone at a given time was used as a measure of their phototactic responses. Single cosinor analysis of these data has revealed, for the first time, a circadian rhythmicity in the phototactic behaviour of a cavernicolous organism. However, imposition of restricted feeding schedules shifted the peak time of the circadian rhythm in phototactic responses. Meal scheduling may thus be an effective synchronizer for this behavioural rhythm.

Reciprocity versus rhythmicity in spontaneous alternations of nasal airflow.

Abstract: Active anterior rhinomanometry was used to observe nasal airflow in five men and four women (ages 18–30). Measurements were obtained for each nasal passage every 5 min throughout an uninterrupted 8-hr session. Facial skin temperature from the left and right side of the face was recorded simultaneously from thermocouples. Observations were made during the months of May and June; subjects were allowed to maintain their routine diurnally active schedules prior to observation. Airflow in the two passages showed a significant negative correlation (i.e. Was reciprocal) in 44% of subjects (N= 9). Autocorrelation and spectral analysis of the airflow data found evidence of periodicity in 39% of individual nostrils and 56% of subjects. Mean estimated period was 4.5 ± 1.0 hr (range 3.5–6.0 hr). Only 22% of subjects showed statistical evidence of periodicity in both nostrils (i.e. a “nasal cycle”). Left- and right-side facial skin temperatures changed in parallel rather than reciprocally, but showed evidence of perio...

Circadian Rhythms in Hot Flashes in Natural and Surgically-Induced Menopause

Abstract: The aim of this study was to investigate circadian and ultradian variations in menopausal hot flash. The number of hot flashes per 2-hr period was collected from 25 diurnally-active, perimenopausal women for 1 week in January or February of each year for 3 consecutive years. Fourteen women were experiencing natural menopause (NM) (mean age 51.9 years) and 11 were experiencing surgically-induced menopause (SIM) (mean age 52.0 years). The difference in the number of hot flashes between the two types of menopause at each clock time was not statistically significant; neither was the mean number of hot flashes per 24 hr different between the two groups (Student's t-test). Data when normalized for each woman and placed end-to-end revealed by cosinor analysis circadian rhythmicity in the SIM group (P = 0.02) but not in the NM group. A 12-hr periodicity was detected in both groups (P less than 0.001 for both). An 8-hr rhythm was detected only for the NM group (P = 0.04). Both groups combined exhibited statistically significant rhythmicities with periods of 24 hr (P = 0.003), 12 hr (P less than 0.001) and 8 hr (P = 0.005). Regardless of the type of menopause, the women could be separated into two groups based on the temporal pattern of hot flashes during the day. One group was defined by the occurrence of peak frequency of flashes during the morning (0400-0959), while the second group was defined by the occurrence of the peak in the evening (1600-2159).(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian hematologic time structure in the elderly.

Abstract: Twenty-three clinically healthy, diurnally active elderly subjects, 71 ± 5 years of age were studied over a 24-hr span (six samples). Complete blood counts and differential counts were done (Ortho ELT-8, Wright stained smears). The circadian rhythm parameters of the hematologic variables in the elderly subjects were compared with reference values obtained from a larger group of clinically healthy young adult and adult subjects studied independently. The data were analyzed by cosinor and the Bingham test. Circadian rhythms in the number of circulating formed elements in the peripheral blood persist in the aged. In comparison with the young adult, the elderly subjects show differences in the timing (phase advance) of the circadian rhythms in circulating neutrophil leukocytes and lymphocytes, a decrease in the circadian amplitude of circulating platelets, a decrease in circadian rhythm adjusted mean (mesor) in the red cell count, and in the neutrophil band forms.

Adaptation to shift work--experimental approaches with reduced masking effects.

Abstract: Chronobiological characteristics of night and shift work, features of the adaptive process to be expected are briefly considered in the first part of the paper. Demands for experimental routines to imitate these situations and the need for routines reducing masking effects are discussed. Experiments meeting these demands are reviewed. Practical considerations are derived. Interindividual differences of the circadian system are taken into account.

Ultradian, circadian and seasonal variations of plasma progesterone and LH concentrations during the luteal phase.

Abstract: The circadian variations in plasma progesterone (P) and LH concentrations were investigated in six women, aged 23–40 years. All were studied in the mid-luteal phase (7 ± 2 days after LH mid-cycle surge). Experiments were conducted in autumn and in spring. Blood samples were obtained every 15 min for 24 hr. Plasma P and LH concentrations were measured by RIA. Each subject's time-series was analysed using three methods; visual inspection (chronogram), spectral analysis to estimate component periods of rhythms (τ) and cosinor analysis to quantify the rhythms parameters.Marked temporal variations in plasma P concentration were observed in each subject. The maximal variations over a 24-hr period, ranged between 13–58.5 mmol/1.Differences related to sampling time were statistically validated by ANOVA (p <0.00001). Significant harmonic periods were detected by spectral analysis but differed among subjects. In all subjects but one, a circadian rhythm was detected. The acrophase location was similar (about 0700 hr...

The diagnosis of breast pre-cancer by the chronobra- i. background review

Abstract: Les auteurs, apres avoir presente les elements de l'epidemiologie du cancer du sein, a savoir sa plus grande probabilite chez les femmes ayant eu une premiere grossesse tardive, mettent en evidence l'association existant entre le developpement tumoral, l'augmentation du metabolisme qui en resulte et par consequent l'accroissement de la temperature locale. Ici, ils etudient les variations de la temperature mammaire en relation avec le cycle menstruel et presente un dispositif permettant d'enregistrer ces variations thermiques en ambulatoire

Chronotoxicity of sodium valproate and its mechanisms in mice: dose-concentration-response relationship.

Abstract: A significant circadian rhythm of acute toxicity was demonstrated in mice with intraperitoneal (i.p.) injection of sodium valproate (VPA). The role of pharmacokinetics on the rhythms of the toxicity and electroshock seizure (ES) threshold was investigated. ICR male mice, housed under a light-dark (12:12) cycle, were injected intraperitoneally 1200 mg/kg for the acute toxicity study and 300 mg/kg for the anticonvulsant effect study. In the acute toxicity, the highest mortality was found when VPA was injected at 1700 and the lowest at 0900 or 0100. The time course of mean plasma and brain VPA concentrations after an injection of VPA was not different between mice injected at 1700 and mice injected at 0100. In the anticonvulsant effect, no significant circadian rhythm was demonstrated for both the ES threshold and the plasma VPA concentrations after i.p. injection, although a significant rhythm has been reported for them after oral administration. The results suggest that the circadian rhythm in the mortality after an i.p. injection of VPA may be due to the rhythm in the sensitivity of the central nervous system to the drug and that the mechanism underlying the rhythm of VPA acute toxicity is different from that of the anticonvulsant action of VPA. The route and the time of drug administration are essentially important to study the anticonvulsant effect and acute toxicity of VPA in mice.

Is "masking" an appropriate term?

Abstract: Discussion about the complexity of the synchronized state in a relatively simple organism: Neurospora. In this organism, an endogenous circadian clock controls the vegetative spore formation pulses of higher light intensities and higher temperatures act on the clock mechanism

Daily Modifications of 3h-Naloxone Binding Sites in the Rat Brain: A Quantitative Autoradiographic Study

Abstract: The endogenous opioid peptides, the opiate receptors and several related behaviours, like opioid-mediated analgesia, show daily variations in different animal species including rats. The attempt to correlate the daily rhythm of opiate receptors in the central nervous system (CNS) to opiate related rhythmic phenomena requires an experimental approach with a high anatomical resolution, as the opioid distribution is very heterogeneous. In this paper we present the study of daily variations of 3H-naloxone binding sites in the different regions of the adult male rat brain, performed by means of quantitative autoradiography. Five rats are sacrificed at each investigated time of the day (0200, 0600, 1000, 1400, 1800 and 2200). The ligant is 3H-naloxone (4 nM), the quantification is performed by means of densitometric procedures (image analyzer Tesak VDC 501, computer Digital PDP 11, 3H-microscale). The statistical analysis is performed according to the single Cosinor method and the one-way analysis of variance followed by the multiple range test of Duncan. We analysed 33 different regions of the rat CNS, and the daily variations of opiate receptors are regionally selective. A circadian rhythm is found in the anterior cingulate cortex, hippocampal cortex, periventricular, medial, ventral, reticular and posterior nuclei of the thalamus, rhomboid, gelatinosus and rheuniens nuclei, lateral hypothalamus, locus coeruleus, grey substance of the pons, reticular formation of medulla oblongata, inferior olivary complex, medial part of the nucleus of the solitary tract and nucleus of the spinal tract of the trigeminal nerve. An ultradian rhythm is found in the medial and lateral preoptic areas, in the medial hypothalamus, in the medial and in the lateral nuclei of habenula. No significant variations during 24 hr according to the Cosinor analysis are found in the dorsal and lateral cerebral cortex, striatum, globus pallidus, bed nucleus of the stria terminalis, septal nuclei, lateral nucleus of the thalamus, cochlear nuclei, nucleus of the solitary tract, lateral and caudal parts, dorsal motor nucleus of the vagal nerve, XII and IX nerve nuclei. The amplitude of the daily variations observed ranges from 10 to 40%. Our results demonstrate the high anatomical selectivity of the daily modifications of 3H-naloxone binding sites in the rat CNS. They also indicate that quantitative autoradiography is a suitable and sensitive technique for these studies.

Season-Of-Birth and Acute Leukemia of Infancy

Abstract: Because of its short and clearly delineated latency period, acute leukemia of infancy is particularly suited to etiologic analysis. From 1950 to mid-1985,31 infants with acute leukemia (< 1 year of age) were registered at the University of Texas, M.D. Anderson Cancer Center at Houston. The medical records of these infants were reviewed for demographic and birth information. Of the 31 infants, 14 (45%) were Hispanic. The sex ratio was 3:1 male/female) for white infants and 5:9 for Hispanic infants. Of the white infants, half had acute lymphocytic leukemia, compared with all but one of the Hispanic infants. There was a significant excess of winter births among the infants diagnosed with acute leukemia (P< 0.05). The significant association between season-of-birth and the occurrence of leukemia cases is suggestive of periodicity of an environmental etiologic agent, perhaps acting in concert with endogenous rhythmicities in susceptibility to that agent. This finding is deserving of further study.

Lithium chloride scn injection alters the circadian rhythm of food intake

Abstract: Effect of lithium injections through chronically implanted cannulae into the bilateral suprachiasmatic nuclei (SCN) on the circadian rhythm of food intake was investigated in the rat. It was observed that the circadian rhythm was disrupted by injections of lithium at the beginning of the light as well as the dark phase of the LD cycle. In either case the percentage of the food consumed during the 12-hr light period increased while that during the dark period decreased without any significant change in the total daily intake. Disruptions in the circadian rhythm of food intake failed to show any dose-response relation. Injections of saline into the SCN or lithium into the nearby SCN area did not produce a disruption of the circadian rhythm of food intake.

The detection of peaks in luteinizing hormone secretion.

Abstract: Fluctations in luteinizing hormone are believed to consist of irregularly spaced sharp increases separated by periods of exponential decay A simple method is presented for analysing such fluctuations when the data consist of uniformly sampled observations of hormone Specific allowance for the exponential decay in the absence of pulses is made via a time series model before assessing the number and extent of pulses All calculations are done using MINITAB regression programs The results have been compared with those obtained by three established models and are in general agreement

The diagnosis of breast pre-cancer by the chronobra--II. The breast pre-cancer test.

Abstract: Contemporary screening programmes for early breast cancer based on X-rays (mammography) are very expensive and have two serious limitations in their potential to control the disease. First, soft-tissue radiology imaging is poor at resolving a tumour in the youngest third of cancer patients because of breast density; second, by the time size of a tumour enables a diagnosis to be made, there are already hundreds of thousands of malignant cells; depending on the particular biology of the tumour they may have disseminated.For effective control of the disease there must be some understanding of breast cancer biology so that appropriate pre-cancer therapeutic strategies can be implemented. There is persuasive evidence from the growth kinetics of excised tumours; the prognosis of the breast cancer process; the protection afforded by an early first pregnancy; the age-related sensitivity to diagnostic X-rays; and, the age-correlated presence of oestrogen receptors in tumours, that the genesis of cancer is usually ...

Circannual incidence of Giardia lamblia.

Abstract: A circannual rhythm of Giardia lamblia positive stools was found by examination of records from three clinical laboratories in central Arkansas for the period 1980-1986. Cosinor analysis of monthly Giardia incidence based on stool specimen records from approximately 12,000 patients over the 7-year period revealed a circannual rhythm (P< 0.001) on the basis of percent positive patients/month, with a computive acrophase occurring in late summer and minimum values in the winter. Patients involved in the study were primarily from the central Arkansas metropolitan areas, southern delta regions and northern mountainous regions of the state. Analysis of the data on the basis of total positive Giardia patients/month also revealed a circannual rhythm with the acrophase again occurring in late summer. The overall mean for percent positive stool specimens for the 7-year period was 5.3%, compared with the national average of 3.8% for G. lamblia positive stools. The data indicate that there may be a “Giardia season” i...

Behavioral and neurochemical effects of fencamfamine on rats: a chronobiologic approach.

Abstract: Fencamfamine (FCF) is a psychostimulant classified as an indirect dopaminergic agonist Circadian rhythms of some behavioral and neurochemical parameters were investigated in control rats and in rats which had been treated with a single dose of FCF across the 24-hr span Rats were entrained to light/dark (LD) 12:12, lights on from 0700 to 1900 In behavioral experiments (performed in March) the rats were injected intraperitoneally with saline or FCF (35 mg/kg) at one of six times: 0900, 1300, 1700, 2100, 0100 or 0500 Fifteen minutes after treatment the duration of sniffing, rearing and locomotion was recorded during 120 min Controls showed circadian rhythms for sniffing and rearing with acrophases at 2255 and 0118, respectively In animals treated with FCF, only locomotion displayed significant circadian variation with acrophase at 1912 Two-way analysis of variance (ANOVA) showed a statistically significant circadian time-dependent effect of FCF on all behavioral parameters studied; the increase of sniffing, rearing and locomotion induced by FCF was higher in rats treated during the rest phase In the biochemical studies (performed between March-June), rats were treated (ip) with saline or FCF (10 mg/kg) at one of four times: 0900, 1700, 2100 or 0100 The levels of homovanillic acid (HVA) in the striatum and tuberculum olfactorium, 5-hydroxyindolacetic acid (5-HIAA) in the cerebellum and 3-methoxy-4-hydroxypheniglycol (MHPG) in the frontal cortex were determined Controls showed circadian rhythms for HVA (striatum), MHPG (frontal cortex) and 5-HIAA (cerebellum) with acrophases at 2233, 1955 and 1029, respectively(ABSTRACT TRUNCATED AT 250 WORDS)

Masking and Biological Rhythms

Abstract: (1989). Masking and Biological Rhythms. Chronobiology International: Vol. 6, No. 1, pp. 1-2.

Comparison of the circadian rhythm in cell proliferation in corneal epithelium of male rats studied under normal and hypobaric (hypoxic) conditions.

Abstract: Groups of 20-45-day-old rats maintained on a light (0600-1800)/dark (1800-0600) regimen with food and water available ad libitum were studied for the effect of hypoxic hypoxia on the circadian rhythm of corneal epithelial mitosis and thymidine incorporation. In experiments conducted during the months of September and November, hypoxic hypoxia was accomplished by the exposure of rats to a simulated altitude of 7500 m in one series of experiments, or to a gaseous mixture of 8% oxygen and 92% nitrogen at sea level atmospheric pressure (760 mmHg) in another series of experiments. Controls were included as well. Statistically significant (P less than 0.05) circadian rhythmicity in the corneal mitotic index was substantiated in the control animals with mesor (M) = 12.4%, amplitude (A) = 9.6% and acrophase (phi) of 0911. In the hypoxic hypoxia situation, the mesor and amplitude were depressed to 8.6 and 5.9%, respectively. In control groups, thymidine incorporation was circadian rhythmic with M = 38.5 and A = 11.3 cpm/microns DNA and acrophase of 2255. In the hypoxic hypoxia situation, the mesor was similar to the controls; whereas the amplitude was suppressed to 6.1% and acrophase was phase advanced by about 7 hr. Changes in the circadian rhythm of corneal mitosis and in thymidine incorporation under hypoxic hypoxia can be explained by programmed-in-time energy requirements during the corneal cell regeneration cycle.