Circadian rhythms in rats: effects of random lighting

Increase in body weight, spontaneous running activity, and adrenal cortical function have been studied in rats exposed to a random lighting schedule. In two separate experiments, grouped control animals were given 12 or 14 hours of light alternating with 12 or 10 hours of darkness, respectively, while coresponding grouped experimental animals were given the same total amounts of light and darkness per 24 hour period in a randomized pattern. Random light for periods of 17 to 40 days exerted no influence on growth rate, on weights of endocrine organs, or on adrenal response to adrenocorticotrophic hormone. However, the physiological fluctuation of group running activity and adrenal steroid secretion was abolished. Group desynchronization and the development of circadian rhythms having periods both shorter and longer than 24 hours appear to have replaced the synchronized group rhythmicity.     

Circadian oscillations in rodents: a systematic increase of their frequency with age

The circadian activity rhythms of golden hamsters and two species of deermouse, when released from a light-dark cycle of 12 hours light and 12 hours of darkness into constant darkness, had progressively shorter periods as the animals became older. A possible bearing of this fact on the aging process is briefly outlined.     

Activity rhythms and adiurnal light-dark control

The running-wheel activity pattern of mature male rats was successfully synchronized to light-dark cycles as long as 48 hours and as short as 16 hours. Even after 6 months' exposure to "days" longer than the normal 24 hours, the animals returned promptly to circadian rhythmicity when placed under freerunning conditions of continuous dark. That such rhythms also reappeared when the light condition of the 36-hour cycle was reduced from 660 to 33 lumens per square meter suggests that brightness may be the critical factor in the unexpectedly broad range of entrainment demonstrated.     

Extraoptic phase shifting of circadian locomotor rhythm in salamanders

Timing of locomotor rhythm in the slimy ralamander, Plethodon glutinosus, can be shifted in phase by the environmental light cycle, whether the animals have eyes or not. Rhythmicity persists at least for the first day when animals are transferred to constant conditions, with a period of about 24 hours, and is therefore circadian in nature. An extraoptic photoreceptor site in the brain is suggested.     

Differential rescue of light- and food-entrainable circadian rhythms

When food is plentiful, circadian rhythms of animals are powerfully entrained by the light-dark cycle. However, if animals have access to food only during their normal sleep cycle, they will shift most of their circadian rhythms to match the food availability. We studied the basis for entrainment of circadian rhythms by food and light in mice with targeted disruption of the clock gene Bmal1, which lack circadian rhythmicity. Injection of a viral vector containing the Bmal1 gene into the suprachiasmatic nuclei of the hypothalamus restored light-entrainable, but not food-entrainable, circadian rhythms. In contrast, restoration of the Bmal1 gene only in the dorsomedial hypothalamic nucleus restored the ability of animals to entrain to food but not to light. These results demonstrate that the dorsomedial hypothalamus contains a Bmal1-based oscillator that can drive food entrainment of circadian rhythms.     

Comment on "Differential rescue of light- and food-entrainable circadian rhythms"

Fuller et al. (Reports, 23 May 2008, p. 1074) reported that the dorsomedial hypothalamus contains a Bmal1-based oscillator that can drive food-entrained circadian rhythms. We report that mice bearing a null mutation of Bmal1 exhibit normal food-anticipatory circadian rhythms. Lack of food anticipation in Bmal1-/- mice reported by Fuller et al. may reflect morbidity due to weight loss, thus raising questions about their conclusions.     

Circadian activity rhythm of the deer mouse, Peromyscus: effect of deuterium oxide

Chemical modification of a vertebrate activity rhythm, the circadian (approximately 24-hour) rhythm of Peromyscus leucopus noveboracensis, has been demonstrated. Activity in a running wheel was used to measure the rhythms of mice kept individually in conditions of continuous darkness. Deuterium oxide was presented in the drinking water. The length of the periods of rhythm increased directly and linearly with the increase in concentration of deuterium oxide. There is no threshold for this effect, and the maximum concentration of deuterium oxide (30 percent) that was presented resulted in a 6 percent lengthening of the period of circadian rhythm. The mice reverted to rhythms similar in period length to control values after deuterium oxide was withdrawn from their drinking water.     

Positional syntenic cloning and functional characterization of the mammalian circadian mutation tau

The tau mutation is a semidominant autosomal allele that dramatically shortens period length of circadian rhythms in Syrian hamsters. We report the molecular identification of the tau locus using genetically directed representational difference analysis to define a region of conserved synteny in hamsters with both the mouse and human genomes. The tau locus is encoded by casein kinase I epsilon (CKIepsilon), a homolog of the Drosophila circadian gene double-time. In vitro expression and functional studies of wild-type and tau mutant CKIepsilon enzyme reveal that the mutant enzyme has a markedly reduced maximal velocity and autophosphorylation state. In addition, in vitro CKIepsilon can interact with mammalian PERIOD proteins, and the mutant enzyme is deficient in its ability to phosphorylate PERIOD. We conclude that tau is an allele of hamster CKIepsilon and propose a mechanism by which the mutation leads to the observed aberrant circadian phenotype in mutant animals.     

Fungal endogenous rhythms expressed by spiral figures

Culture zonations in two fungi, Nectria cinnabarina and Penicillium diversum, are expressions of endogenous rhythms. These culture zonations may take the form of either concentric rings or Archimedes' spirals. The rhythm in N. cinnabarina is noncircadian. The rhythm in P. diversum is relatively insensitive to temperature and has a period of approximately 24 hours. The lack of a demonstrable mechanism for phase shifting suggests that this rhythm may also be noncircadian.     

小豆EMS诱变叶形突变体筛选及农艺性状分析(英文)

[目的]对EMS化学诱变小豆京农6号M3代材料进行筛选鉴定,以期获得有潜力、有价值的变异材料。[方法]利用浓度0.5%、0.9%、1.4%的EMS分别处理小豆京农6号12h和24h,对M3代叶形变异率、变异类型、农艺性状及产量构成因素进行分析。[结果]EMS诱变变异叶形突变体223份,占突变体群体总数的18.31%,类型丰富,产生了小密叶、肾形叶、剑叶、鸡爪叶、叶缺刻等叶形突变体。浓度0.9%EMS处理24h,其叶形变异类型最为丰富,且突变频率最高,其变异率分别为4.93%、10.31%、2.69%、8.07%、3.14%。当处理时间相同时,浓度0.9%EMS处理变异类型最丰富,同时表现出一定的高剂量抑制效应,总体表现为浓度0.9%浓度0.5%浓度1.4%;诱变时间不同时,处理时间越长,变异率越高,且变异类型也越丰富。综合叶形突变体农艺性状分析,各种突变类型总体表现为小叶肾叶叶缺刻小密叶剑叶鸡爪叶。这表明小叶、肾叶突变体具有株高降低、紧凑直立、多分枝、多荚、单株产量高、百粒重高等优良性状。[结论]该研究筛选的突变体可为小豆育种及遗传学研究提供有价值的材料。     

Retrograde amnesia produced by electroconvulsive shock after reactivation of a consolidated memory trace

Rats had a memory loss of a fear response when they received an electroconvulsive shock 24 hours after the fear-conditioning trial and preceded by a brief presentation of the conditioned stimulus. No such loss occurred when the conditioned stimulus was not presented. The memory loss in animals given electroconvulsive shock 24 hours after conditioning was, furthermore, as great as that displayed in animals given electroconvulsive shock immediately after conditioning. This result throws doubt on the assertion that electroconvulsive shock exerts a selective amnesic effect on recently acquired memories and thus that electroconvulsive shock produces amnesia solely through interference with memory trace consolidation.     

小豆EMS诱变M3代叶形突变体的筛选及农艺性状分析

[目的]对EMS化学诱变小豆京农6号M3代材料进行筛选鉴定,以期获得有潜力、有价值的变异材料。[方法]利用EMS处理小豆京农6号,对M3代叶形变异率、变异类型、农艺性状及产量构成因素进行分析。[结果]浓度0.9%EMS处理24h,叶形变异类型最为丰富,且突变频率最高。综合叶形突变体农艺性状分析,各种突变类型总体表现为小叶〉肾叶〉叶缺刻〉小密叶〉剑叶〉鸡爪叶。小叶、肾叶突变体具有较低株高、紧凑直立、多分枝、多荚、单株产量高、百粒重高等优良性状。[结论]该研究筛选的突变体可为小豆育种及遗传学研究提供有价值的材料。     

Opossum fetuses grown in culture

Opossum fetuses explanted at limb bud stages have been successfully grown in culture for periods up to 20 hours. Blood circulation was maintained, and organogenesis continued at about the same rate as in vivo.     

Diurnal Rhythm and Photoperiodism in Testicular Recrudescence of the House Finch

A circadian rhythm in house finches appears to control the timing of the photoperiodic response of testicular recrudescence. A 6-hour light period coupled with dark periods of varying duration does not stimulate spermatogenesis in cycle lengths of 24, 48, and 72 hours, but initiates spermatogenesis in cycles of 12, 36, and 60 hours.     

Latitudinal and longitudinal oscillations of cloud features on neptune

Voyager observations suggest that three of Neptune's major cloud features oscillate in latitude by 2 degrees to 4 degrees and that two of them simultaneously oscillate in longitude by 7.8 degrees and 98 degrees about their mean drift longitudes. The observations define most convincingly the two orthogonal oscillations of the second dark spot (near 53 degrees south). These oscillations have similar periods near 800 hours and approximately satisfy a simple advective model in which a latitudinal oscillation produces a phase-shifted longitudinal oscillation proportional to the local wind shear. The latitudinal motion of the Great Dark Spot can be fit with an oscillation period of about 2550 hours, whereas its dominant longitudinal motion, if oscillatory at all, has such a long period that it is not well constrained by the Voyager data.     

Adenosine 3'-5'-monophosphate in rat pineal gland: increase induced by light

Rats were maintained in alternating periods of 12 hours of light and 12 hours of darkness. The concentration of adenosine 3',5'-monophosphate in pineal gland was six times higher at the end of the light period than at the end of the period of darkness. This effect of light was abolished in blinded animals.     

Biochemical modeling of an autonomously oscillatory circadian clock in Euglena

Eukaryotic microorganisms, as well as higher animals and plants, display many autonomous physiological and biochemical rhythmicities having periods approximating 24 hours. In an attempt to determine the nature of the timing mechanisms that are responsible for these circadian periodicities, two primary operational assumptions were postulated. Both the perturbation of a putative element of a circadian clock within its normal oscillatory range and the direct activation as well as the inhibition of such an element should yield a phase shift of an overt rhythm generated by the underlying oscillator. Results of experiments conducted in the flagellate Euglena suggest that nicotinamide adenine dinucleotide (NAD+), the mitochondrial Ca2+-transport system, Ca2+, calmodulin, NAD+ kinase, and NADP+ phosphatase represent clock "gears" that, in ensemble, might constitute a self-sustained circadian oscillating loop in this and other organisms.     

Independence of short- and long-term memory: a neural system analysis

Rats were given electrical stimulation to the midbrain reticular formation or to the hippocampus 4 seconds after they received shocks contingent on the animals' bar-press responses. They were retested for memory of the shocks 64 seconds or 24 hours after the shocks. The animals that received stimulation to the midbrain reticular formation showed amnesia at the 64-second retest and memory at the 24-hour retest. In contrast, animals that received stimulation to the hippocampus showed memory at the 64-second retest and amnesia at the 24-hour retest. The data support a dual, parallel-processing model of memory.