Circadian pacemaker does not arrest in deep hibernation. Evidence for desynchronization from the light cycle

A freerunning rhythm of locomotor activity was observed between hibernation bouts in Turkish hamsters (mesocricetus brandti) kept in 10L:14D light-dark cycles at 10 +/- 1 degree C. The data further indicate an influence of natural hypothermia upon the circadian system and its ability to entrain to light-dark cycles.     

A spontaneous benomyl-resistant mutant ofPodospora anserina exhibiting a diurnal growth rhythm

Summary A spontaneous mutant ofP. anserina isolated by screening for benomyl resistance exhibited a diurnal growth rhythm dependent on light-dark cycles. The rhythmic character, the benomyl resistance and a growth rate reduced to 50% of that of the wild type were inherited together over more than 10 generations. The locus was mapped on linkage group II, 0.35 map units distal to the locusz (=0.81 map units from the centromere).     

Acute effects of unilateral or bilateral superior cervical ganglionectomy on rat pineal N-acetyltransferase activity and melatonin content.

Acute bilateral superior cervical ganglionectomy (SCGX) completely prevents the nocturnal rises in pineal N-acetyltransferase (NAT) activity and melatonin content in male rats kept in light-dark cycles of 14:10. Unilateral SCGX causes the NAT and melatonin levels to be intermediate between those in sham-operated control rats and those in rats from which both ganglia had been removed.     

Acute effects of unilateral or bilateral superior cervical ganglionectomy on rat pineal N-acetyltransferase activity and melatonin content

Summary Acute bilateral superior cervical ganglionectomy (SCGX) completely prevents the nocturnal rises in pineal N-acetyltransferase (NAT) activity and melatonin content in male rats kept in light-dark cycles of 1410. Unilateral SCGX causes the NAT and melatonin levels to be intermediate between those in sham-operated control rats and those in rats from which both ganglia had been removed.Supported by NSF, grant No. PCM 77-05734.     

Functional absence of brain photoreceptors mediating entrainment of circadian rhythms in the adult rat

Summary The photic energy penetrating into the brain was increased in adult rats sustaining craniotomies sealed with transparent plastic. After blinding, these animals failed to entrain their circadian food intake rhythm to light-dark cycles. Short pulses of light did not phase-shift the freerunning rhythm. We conclude that adult rats lack brain photoreceptors mediating entrainment of circadian rhythms.     

A visual stimulus in the courtship ofDrosophila suzukii

Summary The males ofDrosophila suzukii have a specific black spot on their wings and this was surgically removed. In this situation, the males were almost normally accepted by the females when they were stored under a diurnal light-dark cycle, but they were somewhat discriminated against by the females previously exposed to continuous light.     

Zeitgeber-schedule dependent resynchronization of circadian rhythms in nocturnal mammals (Primates and Chiroptera)

Summary Changing the L: D time ratio of an entraining light-dark regime leads to characteristic alterations of the resynchronization behaviour of the circadian activity rhythms in night monkeys (Aotus trivirgatus) and African fruit bats (Rousettus aegyptiacus) after 8 h advance and delay shifts of the LD-Zeitgeber. Reduced speed of re-entrainment and occurrence of antidromic resynchronization point to a lower Zeitgeber strength of 24-h LD-cycles with a prolonged D-phase.Supported by the Deutsche Forschungsgemeinschaft (Er 59/8).     

Reaction time of the topminnowAplocheilus lineatus to surface waves determined by video- and electromyogram recordings

Summary Evoked muscle potentials during a localizing response for a wave center occur inAplocheilus lineatus 30±1.5 msec ( ) earlier than the simultaneously monitored body movements. Considering this time, only the first 8–10 wave cycles of a total wave signal are utilized to identify and localize a wave source.This study was supported by the Deutsche Forschungsgemeinschaft.     

Zeitgeber induced modulation of activity patterns in nocturnal mammals (Chiroptera)

Summary Changing the L:D intensity ratio of a synchronizing light-dark regime leads to characteristic modulations of the activity pattern of 5 Chiroptera species. These modulations fit the predictions ofWever's oscillator model.Supported by a grant from the Deutsche Forschungsgemeinschaft (No. Er 59, 1–4).     

Exogenous melatonin accelerates re-entrainment: Attenuation of the circadian rhythm of metabolic rate in the canary,Serinus canaria

Administration of melatonin in the drinking water (200 g/ml in 1% ethanol) decreased the time of re-entrainment of the circadian rhythm of the metabolic rate (measured as oxygen uptake) of domestic canaries (Serinus canaria) after 10-h delay phase shifts of the light-dark (LD) cycle by 1.3 days on average. Associated with faster re-entrainment, the amplitude of the metabolic rhythm was attenuated by 46% on, average on the first day after the shift as compared with about 25% in the controls. After re-entrainment, the amplitude of the metabolic rhythm during melatonin administration was about 23% lower than in the controls. The minimum resting metabolic rate increased by ca 5% on average during treatment with melatonin. The results are consistent with the hypothesis that constant high plasma levels of melatonin act on higher levels of the circadian oscillatory system rather than by directly affecting peripheral or central photoreceptors.     

Effect of strychnine on the electroretinogram of the isolated rabbit retina

Zusammenfassung Strychnin in einer Konzentration von 3×10^–6 bis 3,5×10^–5 M/l verursacht eine vorübergehende Vergrösserung derb-Welle des ERG der isolierten Kaninchennetzhaut, in einer Konzentration von 7×10^–5 bis 7×10^–4 M/l verkleinert es dieb-Welle. Aus den Ergebnissen wird geschlossen, dass die Substanz zumindest teilweise schon auf die Schicht des zweiten Neurons wirkt.     

The effect of perchlorate ion and some pharmacological agents on the sensitivity of the frog (Rana pipiens) rectus abdominis to acetylcholine

Zusammenfassung Die Reaktion des mit Eserin vorbehandelten musculus rectus abdominis des Frosches auf Acetylcholin liess sich durch Oxotremorin (2.0·10^–5 M), Arecolin (2.0·10^–5M), Aceclidin (1.0·10^–4 M) und Carbachol (2.0·10^–7 M) verstärken, während Atropin (1.0·10^–5 M) hemmend wirkte. Perchlorationen in Konzentrationen über 2 · 10^–4 M sensibilisierten den Froschmuskel erheblich und reduzierten die Grenzdosis, bei der eine Potenzierung durch Substanzen mit muskarinähnlicher Wirkung beobachtet wird. Alle beschriebenen Reaktionen liessen sich durch Gehirnextrakte verstärken, in denen zuvor Acetylcholin durch Kochen in alkalischer Lösung zerstört worden war.

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This work was supported by NIH Grants No. NB 03007 and No. 5-F1-GM-22,905.     

Interaction du 2,4-dichlorophénol et de l'eau oxygénée dans la destruction enzymatique de l'acideβ-indolylacétique

Summary DCP increases IAA destruction by bothLens andPhaseolus root breis. H₂O₂ inhibits catabolism byLens extracts but activates it whenPhaseolus is used, mainly when roots are cultivated in the dark and contain inhibitors of IAA destruction. DCP 1·10^–3 M and H₂O₂ 1·10^–4 or 1·10^–3 volume forLens and DCP 1·10^–4 M and H₂O₂ 1·10^–3 volume forPhaseolus nullify auxin catabolism.     

Growth stimulating effects of the bromophenol,lanosol, on red algae in axenic culture

Zusammenfassung Wachstumstimulation von 2,3-Dibromo-4,5-Dihydroxybenzylalkohol (Lanosol) in Konzentrationen von 4×10^–5–4×10^–6 wurde in axenischen Kulturen der RotalgenGoniotrichum alsidii undPolysiphonia urceolata festgestellt. Während das Disulfatdikaliumsalz nicht toxisch und von niedrigerer Aktivität war, hatte 2×10^–4 M Lanosol eine Hemmwirkung aufPolysiphonia.     

Melatonin antagonizes colchicine-induced mitotic arrest

Summary Melatonin, in concentrations up to 10^–3 M, showed no effect on mitosis in cultures of HeLa or KB cells. However, when melatonin at 10^–4 M was preincubated with HeLa cells prior to addition of 10^–7 M colchicine, a reduction in the mitotic index, in comparison to colchicine alone, was observed.This work was supported by PHS Grant No. CA 16425.     

Naringenin inhibition on expiants in vitro ofCichorium intybus (Chicory)

Riassunto La naringenina alla concentrazione di 10^–4 M inibisce in modo totale l'emissione di gemme in radici diCichorium intybus in vitro senza tuttavia bloccare completamente la callogenesi. A concentrazioni scalari minori (10^–5, 10^–6, 10^–7 M) questa sostanza causa una inibizione solo nella fase iniziale dell'esperienza.     

Influence of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) on auxin metabolism of plants

Zusammenfassung Die Enzymaktivität der IES-peroxidase in Hafer-Koleoptilen wurde durch Atrazin in Konzentrationen von 10^–10–10^–21 M gehemmt, im Konzentrationsbereich von 10^–6–10^–8 M gesteigert. Atrazin förderte ferner das Wachstum von Sojabohnen-Kallusgewebe in Gegenwart von 5 mg/l Kinetin und 10^–10 bis 10^–18 M Atrazin im Nähragar. Diese Einwirkung von Atrazin auf den Wuchsstoffmetabolismus der Pflanzen gibt erste Anhaltspunkte, die zahlreich beobachteten Förderungen bzw. Hemmungen des Pflanzenwachstums unter dem Einfluss von Atrazin zu erklären. Die Resultate bilden weiterhin eine neue Grundlage für eine mögliche Interpretation des «Proteineffekts» der Triazine.     

Drug interactions in intestinal absorption of3H-digitoxin in rats

Summary The absorption of³H-digitoxin from perfused rat small intestine was inhibited by probenecid (1.0×10^–2 M), ethacrynic acid (0.5×10^–3 M), and mersalyl (8.0×10^–3 M) indicating that digitoxin absorption is at least partly an active process.     

Beeinflussung der ATPase aminspeichernder Granula von Nebennierenmark und Milznerven durch Thallium

Summary ATPases of the amine storing granules from bovine adrenal medulla and splenic nerves are inhibited by Tl⁺⁺⁺ 3×10^–5 and 5×10^–6 M, respectively. Tl⁺ up to 10^–3 M is ineffective. By T1⁺⁺⁺ in concentrations of 10^–4 M or more, proteins are precipitated, so that the enzyme inhibiton by these concentrations is unspecific. If T1⁺ is oxidized to Tl⁺⁺⁺ in the organism, the inhibition of granular ATPase may be responsible for the alterations of the catecholamine metabolism observed in thallium intoxication.