15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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Item Open Access Spontaneous short-term fluctuations in the daily pattern of heart rate, body temperature and locomotor activity in the laboratory rat(1982) Büttner, Dietmar; Wollnik, FranziskaHeart 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°C to 38·45 ± 0·25°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<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.Item Open Access Effects of constant darkness and constant light on circadian organization and reproductive responses in the ram(1988) Ebling, Francis J. P.; Lincoln, Gerald A.; Wollnik, Franziska; Anderson, NorahThe 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 re sponses 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. Conversely, after pretreatment with LD 16:8, the rams were sexually regressed, and exposure to LD 8:16, DD, or LL resulted in redevelopment of the reproductive axis; the rate of development was similar in all three treatments. The overall results illustrate that in the Soay ram the circadian organization of melatonin and activity rhythms is disrupted during pro longed exposure to DD and LL. Reproductive regression or recrudescence occurs under these constant conditions, apparently dictated by the immediate photoperiodic history.Item Open Access Phase shifting the circadian clock with cycloheximide : response of hamsters with an intact or a split rhythm of locomotor activity(1989) Wollnik, Franziska; Turek, Fred W.; Majewski, Philip; Takahashi, Joseph S.Systematic 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.Item Open Access Genetic analysis of circadian and ultradian locomotor activity rhythms in laboratory rats(1987) Wollnik, Franziska; Gärtner, Klaus; Büttner, DietmarObvious differences exist in the daily activity patterns of the LEW/Ztm and ACI/Ztm inbred strains of laboratory rats. The inbred strain ACI/Ztm shows a clear 24-h rhythm of locomotor activity. The activity pattern of the LEW/Ztm strain, however, is characterized by ultradian rhythms of 4- and 4.8-h periods. Genetic analysis of crosses between the two strains was used to examine the relative amounts of additive genetic and dominance effects for traits associated with circadian and ultradian rhythms of locomotor activity. The measured variables of the timing mechanism (amplitude c; acrophase φ; 24, 4.8-, and 4-h spectral estimates) exhibited substantial heritability, with general dominant-recessive modes of inheritance and the associated dominance variance.Item Open Access Wheel-running activity rhythms in two inbred strains of laboratory rats under different photoperiods(1991) Siebert, Ursula; Wollnik, FranziskaWheel-running activity patterns were studied in two inbred rat strains (ACI/Ztm and LEW/Ztm) under 24-h light-dark cycles with various photoperiods. The ACI strain was characterized by a unimodal activity pattern, whereas the LEW strain exhibited a multimodal activity pattern consisting of two activity bouts about 3-5 h apart. Harmonic spectral analyses and chi square periodograms revealed strain-specific differences in the characteristic rhythmic components of the activity pattern. The ACI strain showed only a strong 24-h rhythm, whereas the LEW strain showed additional rhythmic components with periods of 6, 4.8, and 4 h. Except in very young rats, these strain specific patterns were not affected by an experimental lengthening of the dark period. However, differences between the two strains were found in the free-running period and in the mode of entrainment. Our results indicate that the multimodal activity pattern of the LEW strain is not due to an ultradian bout oscillator, instead it may be the result of a unique coupling of multiple circadian oscillators.Item Open Access Comparative sensitivity analysis of muscle activation dynamics(2015) Rockenfeller, Robert; Günther, Michael; Schmitt, Syn; Götz, ThomasWe mathematically compared two models of mammalian striated muscle activation dynamics proposed by Hatze and Zajac. Both models are representative for a broad variety of biomechanical models formulated as ordinary differential equations (ODEs). These models incorporate parameters that directly represent known physiological properties. Other parameters have been introduced to reproduce empirical observations. We used sensitivity analysis to investigate the influence of model parameters on the ODE solutions. In addition, we expanded an existing approach to treating initial conditions as parameters and to calculating second- order sensitivities. Furthermore, we used a global sensitivity analysis approach to include finite ranges of parameter values. Hence, a theoretician striving for model reduction could use the method for identifying particularly low sensitivities to detect superfluous parameters. An experimenter could use it for identifying particularly high sensitivities to improve parameter estimation. Hatze’s nonlinear model incorporates some parameters to which activation dynamics is clearly more sensitive than to any parameter in Zajac’s linear model. Other than Zajac’s model, Hatze’s model can, however, reproduce measured shifts in optimal muscle length with varied muscle activity. Accordingly we extracted a specific parameter set for Hatze’s model that combines best with a particular muscle force-length relation.Item Open Access Sex differences in the daily pattern of locomotor activity in laboratory rats(1985) Wollnik, FranziskaThe present study supplies information supporting an obvious sex difference in the daily pattern of locomotor activity in laboratory rats. Ultradian rhythms, which have been found to be genetically fixed in two inbred strains of rats, are also sex-specific. They were observed in male animals of these strains. The females failed to show any ultradian rhythmicity.Item Open Access Effects of chronic administration and withdrawal of antidepressant agents on circadian activity rhythms in rats(1992) Wollnik, FranziskaExperimental and clinical studies indicate that clinical depression may be associated with disturbances of circadian rhythms. To explore the interaction between circadian rhythmicity, behavioral state, and monoaminergic systems, the present study investigated the effects of chronic administration and withdrawal of the following antidepressant agents on circadian wheel-running rhythms of laboratory rats: a) moclobemide, a reversible and selective monoamine oxidase (MAO) type A inhibitor; b) Ro 19-6327, a selective MAO type B inhibitor; c) desipramine, a preferential norepinephrine reuptake inhibitor; d) clomipramine and e) fluoxetine, both serotonin reuptake inhibitors; and f) levoprotiline, an atypical antidepressant whose biochemical mechanism is still unknown. Wheel-running activity rhythms were studied in three inbred strains of laboratory rats (ACI, BH, LEW) under constant darkness (DD). Two of these inbred strains (BH and LEW) show profound abnormalities in their circadian activity rhythms, namely, a reduced overall level of activity and bimodal or multimodal activity patters. Chronic treatment with moclobemide and desipramine consistently increased the overall level, as well as the circadian amplitude, of the activity rhythm. Furthermore, the abnormal activity pattern of the LEW strain was changed into a unimodal activity pattern like that of other laboratory rats. The free-running period τ was slightly shortened by moclobemide and dramatically shortened by desipramine. Effects of moclobemide and desipramine treatment on overall activity level and duration were reversed shortly after termination of treatment, whereas long aftereffects were observed for the free-running period. All other substances tested had no systematic effects on the activity rhythms of any of the strains. The fact that moclobemide and desipramine altered the period, amplitude, and pattern of circadian activity rhythms is consistent with the hypothesis that monoaminergic transmitters play a significant role in the neuronal control of behavioral state and circadian rhythmicity. Although the present study found that some antidepressives affect parameters of circadian rhythmicity, it could not demonstrate a common effect of all classes of antidepressives.Item Open Access Effect of lithium carbonate on activity level and circadian period in different strains of rats(1994) Hafen, Thomas; Wollnik, FranziskaLithium, an important pharmacological agent for the treatment of manic-depressive illness in humans, is known to lengthen the circadian period in a number of different species. Recent experiments, on the other hand, suggest that pharmacological agents may affect the circadian system indirectly through an increase or decrease of activity. To explore the interaction between pharmacological and activity effects on the circadian system, lithium was administered chronically to three different strains of rats (ACI, BH, and LEW) while wheel-running activity was studied quantitatively. Two of these inbred strains (BH and LEW) show profound abnormalities in their circadian activity rhythms, namely, a reduced overall level of activity and bimodal or multimodal activity patterns. Wheel-running activity was monitored for 4 weeks under baseline conditions, followed by 3 weeks with lithium treatment (0.3% Li2CO3 administered with food) and 4 weeks with normal food. Treatment with lithium (average intake per day = 3.6 ± 0.2 mg) consistently decreased both the overall level and the circadian amplitute of the activity rhythm. The free-running period τ was slightly lengthened during lithium treatment, while the most dramatic effect on period was observed after lithium withdrawal. Correlation analysis, however, revealed only a small negative correlation between activity level and period length, which proved significantly only for animals of the ACI strain. Our data support the traditional interpretation that lithium lengthens circadian period by a direct pharmacological effect on the circadian pacemaker rather than through indirect effects of activity feedback.Item Open Access The protective reflex of Bowerbankia (Bryozoa) : calibration and use to indicate movements of the medium beneath a capillary surface wave(1980) Wiese, Konrad; Wollnik, Franziska; Jebram, DiethardtThe protective polypide-withdrawal reflex ofBowerbankia imbricata (Bryozoa, Ctenostomata) was released by controlled oscillations of the medium (water). The range of effective oscillation frequencies extends from 10 to 200 Hz. The displacements at the threshold of the reflex are 120 μm (peak to peak) at 10 Hz, an average of 30 μm in the range 40-80 Hz, and 150 μm at 200 Hz. The thresholds of oscillation velocity remain within the limits of 0.5 to 1.0 cm/s throughout the frequency range 10-110 Hz, which suggests that this parameter is involved in stimulus reception. The "all-or-none reflex movement" of the animal was employed as an indicator of the position of a defined amount of displacement of the medium beneath a capillary surface wave; this result was compared with calculated values.
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