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F Wollnik

Publications and source records attributed to F Wollnik.

31 records · Page 2Linked to original sources
PubMed1989

Phase shifting the circadian clock with cycloheximide: response of hamsters with an intact or a split rhythm of locomotor activity.

Systemic administration of the protein synthesis inhibitor, cycloheximide, induced both phase advances and phase delays in the circadian rhythm of wheel-running activity in hamsters (Mesocricetus auratus) maintained in constant darkness or constant light. The magnitude and direction of the phase shifts were dependent on the circadian time (CT) of drug treatment. The phase response curves in constant darkness and constant light were of similar general shape, but they differed in the overall mean amplitude of the phase shifts. Maximal phase advances were observed after injections around CT 6-8, maximal delays at CT 0-2. Injections of various doses of cycloheximide at CT 0 induced a dose-dependent phase delay in the rhythm with a maximum delay induced by 10 mg cycloheximide. Injections of cycloheximide in animals with a split activity rhythm caused phase shifts of both components in the same direction (20/39) and in different directions (10/39). The results support the hypothesis that 80S ribosomal protein synthesis plays an important role in the biochemical mechanisms of circadian systems.

Animals↗
PubMed1989

SCN lesions abolish ultradian and circadian components of activity rhythms in LEW/Ztm rats.

A trimodal locomotor activity pattern has been observed in LEW/Ztm rats. Complete and partial lesions of the suprachiasmatic nucleus (SCN) were used to determine whether the same neural substrate may underlie the circadian rhythms and the ultradian modulation of wheel-running activity in these rats. Whereas sham lesions had little or no effect on the wheel-running activity pattern, complete SCN lesions resulted in a complete loss of circadian and ultradian activity components under free-running or 12:12 h light-dark cycle (12:12 LD) conditions. Ultradian and circadian activity components were still present after partial SCN lesions. Periodogram analysis for any given animal revealed that the ultradian periods were always submultiples of the entrained or free-running circadian period. Furthermore there was a high correlation between the amplitudes of circadian and ultradian spectral estimates, but with a different slope in males and females. These results indicate that in LEW/Ztm rats the SCN contributes to the control of both the circadian wheel-running rhythm and the trimodal ultradian modulation of that behavior.

Activity Cycles↗
PubMed1989

Physiology and regulation of biological rhythms in laboratory animals: an overview.

Biological rhythms have been observed in practically all groups of laboratory mammals and at every level of physiological and behavioural organization. Biological rhythms are classified according to their period as ultradian (less than 24 h), circadian (approximately 24 h), infradian (greater than 24 h), and seasonal or circannual rhythms (approximately 1 year). This review outlines what is known about the neurobiology of biological rhythms in mammals and describes the hierarchical order in which ultradian, circadian and infradian rhythms are related to each other. The article does not attempt to catalogue every physiological variable showing rhythmical fluctuations in laboratory mammals. Rather, it focuses on the basic concepts of circadian rhythms and recent advances made in our understanding of the physiology of the internal clock controlling circadian and other biological rhythms.

Animals↗
PubMed1988

Estrous correlated modulations of circadian and ultradian wheel-running activity rhythms in LEW/Ztm rats.

Estrogen treatment alters the expression of ultradian activity rhythms in male and female LEW/Ztm rats. This finding raises the possibility that the expression of ultradian rhythms may vary on different days of the estrous cycle. To test this hypothesis, we recorded the circadian and ultradian wheel-running activity rhythms of entrained (LD 12:12) and free-running sexually mature LEW/Ztm females during their 4- or 5-day estrous cycle. The mean daily activity, the duration of activity, the circadian period of activity, and the occurrence of ultradian rhythms differed significantly among the days of the estrous cycle. In LD 12:12, the phase angle difference between the beginning of activity and light offset varied reliably in 5-day cycling animals. The highest daily mean of activity, the longest duration, and the shortest circadian period length were observed on the day of estrus in both entrained and free-running animals. The day of estrus was characterized by a constant high level of activity throughout the activity phase, while the days following ovulation showed a bi- or trimodal activity pattern. Power spectrum analysis revealed significant ultradian components for the days of metestrus and diestrus, but only circadian components for the days of proestrus and estrus. These results were interpreted as indicating that endogenous changes in circulating hormone levels can induce changes in the ultradian and circadian patterns of wheel-running activity in LEW/Ztm rats.

Animals↗
PubMed1988

Inhibitor of protein synthesis phase shifts a circadian pacemaker in mammalian SCN.

The suprachiasmatic nucleus (SCN) of the hypothalamus contains a circadian pacemaker that regulates many circadian rhythms in mammals. Experimental work in microorganisms and invertebrates suggests that protein synthesis is required for the function of the circadian oscillator, and recent experiments in golden hamsters suggest an acute inhibition of protein synthesis can induce phase shifts in a mammalian circadian pacemaker. To determine whether protein synthesis in the SCN region is involved in the generation of circadian rhythms in mammals, a protein synthesis inhibitor, anisomycin, was microinjected into the SCN region, and the effect on the circadian rhythm of locomotor activity of hamsters was measured. A single injection of anisomycin into the SCN region induced phase shifts in the circadian activity rhythm that varied systematically as a function of the phase of injection within the circadian cycle. These results suggest that protein synthesis may be involved in the generation of circadian rhythms in mammals and that the anatomic site of action of anisomycin is within the hypothalamic suprachiasmatic region.

Animals↗
PubMed1988

Effects of constant darkness and constant light on circadian organization and reproductive responses in the ram.

The relationship between circadian rhythms in the blood plasma concentrations of melatonin and rhythms in locomotor activity was studied in adult male sheep (Soay rams) exposed to 16-week periods of short days (8 hr of light and 16 hr of darkness; LD 8:16) or long days (LD 16:8) followed by 16-week periods of constant darkness (dim red light; DD) or constant light (LL). Under both LD 8:16 and LD 16:8, there was a clearly defined 24-hr rhythm in plasma concentrations of melatonin, with high levels throughout the dark phase. Periodogram analysis revealed a 24-hr rhythm in locomotor activity under LD 8:16 and LD 16:8. The main bouts of activity occurred during the light phase. A change from LD 8:16 to LD 16:8 resulted in a decrease in the duration of elevated melatonin secretion (melatonin peak) and an increase in the duration of activity corresponding to the changes in the ratio of light to darkness. In all rams, a significant circadian rhythm of activity persisted over the first 2 weeks following transfer from an entraining photoperiod to DD, with a mean period of 23.77 hr. However, the activity rhythms subsequently became disorganized, as did the 24-hr melatonin rhythms. The introduction of a 1-hr light pulse every 24 hr (LD 1:23) for 2 weeks after 8 weeks under DD reinduced a rhythm in both melatonin secretion and activity: the end of the 1-hr light period acted as the dusk signal, producing a normal temporal association of the two rhythms. Under LL, the 24-hr melatonin rhythms were disrupted, though several rams still showed periods of elevated melatonin secretion. Significant activity rhythms were either absent or a weak component occurred with a period of 24 hr. The introduction of a 1-hr dark period every 24 hr for 2 weeks after 8 weeks under LL (LD 23:1) failed to induce or entrain rhythms in either of the parameters. The occurrence of 24-hr activity rhythm in some rams under LL may indicate nonphotoperiodic entrainment signals in our experimental facility. Reproductive responses to the changes in photoperiod were also monitored. After pretreatment with LD 8:16, the rams were sexually active; exposure to LD 16:8, DD, or LL resulted in a decline in all measures of reproductive function. The decline was slower under DD than LD 16:8 or LL.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Neonatal sex reversal of the brain and the urinary excretion of sex dependent proteins (SDP) in the rat.

In contrast to females adult male rats excrete a variety of low molecular weight sex dependent urinary proteins (SDP). Electrophoretic separation of these proteins yields at least 8 protein bands which are arranged in typical patterns. The present study was performed to investigate the effect of sexual differentiation, which can be influenced by neonatal hormone treatment, on production and excretion of the individual SDP-bands (I-VIII). Two major groups of rats were studied: one group was neonatally treated with testosterone propionate (TP, females) or cyproterone acetate (males). Another group of rats with or without neonatal TP-treatment were gonadectomized in adulthood and subsequently implanted with TP. The results demonstrated that SDP excretion is mainly related to the circulating plasma testosterone levels. The sexual differentiation of the brain, however, influences the quantity of SDP excreted which is especially evident for bands I and II. Neonatal cyproterone had influence on these two bands only. The results demonstrate that the hormonal mechanisms regulating the excretion of SDP varies in respect to the different protein bands. The functional role of sexual brain differentiation on the excretion of SDP and the detailed mechanisms by which the brain may control this excretion remain to be determined.

Alpha-Globulins↗
PubMed1986

Effects of adult or perinatal hormonal environment on ultradian rhythms in locomotor activity of laboratory LEW/Ztm rats.

Four experiments were performed with male and female rats of the inbred strain LEW/Ztm maintained under a light-dark schedule of 12:12 hours. The animals were subject to castration (GOX) or ovariectomy (OVX), estradiol 17 beta-implantation (E2-capsules), and perinatal hormonal treatments with testosterone propionate (TP) and an androgen antagonist (cyproterone acetate, CA). Results indicated a difference in the locomotor activity pattern between the two sexes as a result of the endogenous estradiol levels of the adult animals. The activity pattern of male LEW rats was characterized by ultradian rhythms of 4 and 4.8 hr periods. The female LEW rats, on the other hand, generally exhibited a clear circadian activity pattern and no ultradian activity rhythms. Following ovariectomy, each of the females showed distinct ultradian rhythms. These disappeared after E2-implantation. Castration of adult males had no effect on the ultradian activity pattern. Implantation of E2-capsules resulted in a marked decrease of the ultradian activity components. Perinatal treatment of the males with an androgen antagonist (CA) did not appear to effect ultradian rhythms during adulthood. Females treated perinatally with testosterone showed a significant increase in the ultradian activity components. This effect is assumed to be due to low estrogen levels in these animals during adulthood. Our study supports the assumption that ultradian rhythms are a result of changes in the phase relationships between several circadian oscillators. The synchrony of these oscillations seems to be facilitated by estradiol.

Activity Cycles↗
PubMed1984

Blood pressure in rats: a comparison of a multifactorial experimental design to measurements in an outbred stock.

Systolic blood pressure was measured in males of 8 inbred strains and 1 outbred stock of rats 5 times over a period of 20 min on 5 consecutive days. The strain means ranged between 107.9 mmHg and 149.3 mmHg. The estimated variance between strains (V = 248.7 mmHg) was about 5 times higher than the variance within strains (V = 54.3 mmHg). The intraindividual variance within strains was relatively constant (V = 24.0-37.6 mmHg), while the interindividual variance varied to a great extent (V = 4.5-44.5 mmHg) from strain to strain. The outbred stock showed values of blood pressure and components of variance similar to those of a single inbred strain. Thus, by investigation of a battery of 8 inbred strains in a multifactorial experimental design a greater phenotypic variability due to genetic strain differences is achieved than by measurements in a single outbred stock.

Analysis of Variance↗
PubMed1982

Spontaneous short-term fluctuations in the daily pattern of heart rate, body temperature and locomotor activity in the laboratory rat.

Heart rate (HR), body temperature (BT) and locomotor activity (LA) were measured continuously over 5 days in freely moving rats. In addition to the well-known circadian rhythms, all variables exhibited considerable fluctuations in amplitude mainly during the dark, but also in the light periods. The values of HR varied from 286 +/- 12 to 470 +/- 26 b.p.m. and BT from 36.15 +/- 0.15 degrees C to 38.45 +/- 0.25 degrees C. The large variability of HR, BT and LA within a single day was due more to large short-term fluctuations within periods of about 3-5 hours duration, than to differences between the light and the dark period. Good consistency of daily patterns and similarity of the 3 variables was found within the animals. Usually there were 3 or 4 regular peaks during the dark and often another peak 3-4 hours after the onset of light. Correlation coefficients, calculated on the basis of 5-min mean values, were highly significant (P less than 0.001) for LA vs HR (0.61-0.73), LA vs BT (0.40-0.53), and HR vs BT (0.61-0.68). Between-hour correlations were higher than these common correlations of 5-min values. HR vs BT (0.76-0.83) and LA vs BT (0.63-0.79) correlated as well as LA vs HR (0.72-0.83). The short-term fluctuations (within-hours) gave lower correlation coefficients for LA vs BT (0.23-0.32) and HR vs BT (0.29-0.41) than LA vs HR (0.40-0.70). This seems to result from a physiological delay of BT relative to HR and LA.

Animals↗