The cycling and distribution of PER-like antigen in relation to neurons recognized by the antisera to PTTH and EH in Thermobia domestica

The cephalic nervous system of the firebrat contains antigens recognized by antisera to the clock protein period (PER), the prothoracicotropic hormone (PTTH) and the eclosion hormone (EH). The content of the 115 kDa PER-like antigen visualized on the western blots fluctuates in diurnal rhythm with a maximum in the night. The oscillations entrained in a 12:12 h light/dark (LD) cycle persist in the darkness and disappear in continuous light. They are detected by immunostaining in 14 pairs of the protocerebral neurons and are extreme in four suboesophageal neurons and two cells in each corpus cardiacum that contain PER only during the night phase. No circadian fluctuations occur in three lightly stained perikarya of the optic lobe. Five cell bodies located in each brain hemisphere between the deuto-and the tritocerebrum retain weak immunoreactivity under constant illumination. In all cells, the staining is confined to the cytoplasm and never occurs in the cell nuclei. The cells containing PER-like material do not react with the anti-PTTH and anti-EH antisera, which recognize antigens of about 50 and 20 kDa, respectively. The anti-PTTH antiserum stains in each brain hemisphere seven neurons in the protocerebrum, eight in the optic lobe, and 3–5 in the posterior region of the deutocerebrum. The antiserum to EH reacts in each hemisphere with just two cells located medially to the mushroom bodies. No cycling of the PTTH-like and EH-like antigens was detected.     

Phase resetting and phase singularity of an insect circannual oscillator

In circadian rhythms, the shape of the phase response curves (PRCs) depends on the strength of the resetting stimulus. Weak stimuli produce Type 1 PRCs with small phase shifts and a continuous transition between phase delays and advances, whereas strong stimuli produce Type 0 PRCs with large phase shifts and a distinct break point at the transition between delays and advances. A stimulus of an intermediate strength applied close to the break point in a Type 0 PRC sometimes produces arrhythmicity. A PRC for the circannual rhythm was obtained in pupation of the varied carpet beetle, Anthrenus verbasci, by superimposing a 4-week long-day pulse (a series of long days for 4 weeks) over constant short days. The shape of this PRC closely resembles that of the Type 0 PRC. The present study shows that the PRC to 2-week long-day pulses was Type 1, and that a 4-week long-day pulse administered close to the PRC’s break point induced arrhythmicity in pupation. It is, therefore, suggested that circadian and circannual oscillators share the same mode in phase resetting to the stimuli.     

Impacts of biological control and invasive species on a non-target native Hawaiian insect

The potential for classical biological control to cause unintended harm to native species was evaluated in the case of the endemic Hawaiian koa bug, Coleotichus blackburniae White (Hemiptera: Scutelleridae), and parasitoids introduced to Hawaii for control of an agricultural pest, the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae). Parasitism of C. blackburniae eggs, nymphs and adults by biocontrol agents was quantified across a wide range of habitats and compared to other sources of mortality. Egg mortality due to the biocontrol agent Trissolcus basalis Wollaston (Hymenoptera: Scelionidae) was low (maximum 26%) and confined to elevations below 500 m on a single host plant. Predation, mainly by alien spiders and ants, was the greatest source of egg mortality (maximum 87%). Parasitism of adult C. blackburniae by the biocontrol agent Trichopoda pilipes (F.) (Diptera: Tachinidae) was near zero at 21 of 24 sites surveyed. Three sites with high bug density had higher levels of T. pilipes parasitism, reaching maxima of 70% among adult female bugs, 100% among males and 50% among fifth instars. Male-biased parasitism indicated that T. pilipes is adapted to using male aggregation pheromone for finding C. blackburniae hosts. The relative impacts of biocontrol agents and other sources of mortality were compared using life tables. Invasive species, particularly generalist egg predators, had the greatest impacts on C. blackburniae populations. Effects of intentionally introduced parasitoids were relatively minor, although the tachinid T. pilipes showed potential for large impacts at individual sites. In retrospect, non-target attacks by biological control agents on C. blackburniae were predictable, but the environmental range and magnitude of impacts would have been difficult to foresee.     

Circadian oscillations of neuropeptide expression in the human biological clock

The mammalian suprachiasmatic nucleus is the principal component of a neural timing system implicated in the temporal organization of circadian and seasonal processes. The present study was performed to analyze the circadian profiles of two major neuropeptidergic cell groups in the human suprachiasmatic nucleus. To that end the brains of 40 human subjects collected at autopsy were investigated. The populations of arginine vasopressin- and vasoactive intestinal polypeptide-expressing neurons, located in the shell and core of the suprachiasmatic nucleus, respectively, showed marked circadian rhythms with an asymmetrical, bimodal waveform. Time series analysis revealed that these circadian cycles in neuronal activity could be described by a composite model consisting of a nonlinear periodic function, with mono- and diphasic cycles. The findings suggest that the 24-h biosynthesis of neuropeptides in the human suprachiasmatic nucleus, being part of the neural output pathway of the clock, is driven by a complex pacemaker system consisting of coupled nonlinear oscillators, in accordance with a multioscillator model of circadian timekeeping.Abbreviations AIC Akaikie's information criterion - ARMA autoregressive moving average - AVP arginine vasopressin - c-fos immediate early gene - Per period gene - SCN suprachiasmatic nucleus - VIP vasoactive intestinal polypeptide     

Review of the Dual-Clock Control of Tidal Rhythms and the Hypothesis that the Same Clock Governs Both Circatidal and Circadian Rhythms

Discoveries first published in 1986 did not fit the de rigueur working hypothesis that the clocks governing tide-associated rhythms had a fundamental period of 12.4 h, a value equal to the average interval between successive tides on most coastlines of the world. To explain the results a dual-clock schema was fashioned that envisioned two clocks, strongly coupled together 180° antiphase, each running at a basic rate of 24.8 h (the interval of a lunar day), as the driving agents of tide-associated rhythms (details are given in the text). This elaboration has been named the circalunidian-clock hypothesis, a hypocorism used in some armchair ruminations back in 1973. In the decade since 1986, a goodly amount of evidence has been garnered that is consistent with this hypothesis—suggesting that first-call divination appears to have been visionary. Acceptance of this hypothesis leads to further cerebration that a 24.8-h clock, its circa periods in constant conditions, and other properties—which fully overlap with our perception of the circadian clock that drives daily rhythms—may indicate that circadian and circalunidan timepieces are not different entities. The known properties of both daily and lunar clock-types are compared and contrasted, and, with the exception of one feature (for which there is at least a philosophical explanation), it is concluded that the same clock that drives tidal rhythms could also motor daily rhythms, i.e., there may be no such thing as a 12.4-h horologue.     

Review of the Dual-Clock Control of Tidal Rhythms and the Hypothesis that the Same Clock Governs Both Circatidal and Circadian Rhythms

Discoveries first published in 1986 did not fit the de rigueur working hypothesis that the clocks governing tide-associated rhythms had a fundamental period of 12.4 h, a value equal to the average interval between successive tides on most coastlines of the world. To explain the results a dual-clock schema was fashioned that envisioned two clocks, strongly coupled together 180° antiphase, each running at a basic rate of 24.8 h (the interval of a lunar day), as the driving agents of tide-associated rhythms (details are given in the text). This elaboration has been named the circalunidian-clock hypothesis, a hypocorism used in some armchair ruminations back in 1973. In the decade since 1986, a goodly amount of evidence has been garnered that is consistent with this hypothesis—suggesting that first-call divination appears to have been visionary. Acceptance of this hypothesis leads to further cerebration that a 24.8-h clock, its circa periods in constant conditions, and other properties—which fully overlap with our perception of the circadian clock that drives daily rhythms—may indicate that circadian and circalunidan timepieces are not different entities. The known properties of both daily and lunar clock-types are compared and contrasted, and, with the exception of one feature (for which there is at least a philosophical explanation), it is concluded that the same clock that drives tidal rhythms could also motor daily rhythms, i.e., there may be no such thing as a 12.4-h horologue.     

Circadian Modulation of Acute Alcohol Sensitivity But Not Acute Tolerance in Drosophila

An increased understanding of the factors affecting behavioral and neurological responses to alcohol and alcohol physiology is necessary given the tremendous toll alcohol abuse and alcoholism exert on individuals and society. At the behavioral and molecular levels, the response to alcohol appears remarkably conserved from Drosophila to humans, suggesting that investigations across model species can provide insight into the identification of common modulatory factors. We investigated the interaction between the circadian clock and alcohol sensitivity, alcohol tolerance, and alcohol absorbance in Drosophila melanogaster. Using a loss-of-righting reflex (LoRR) assay, we found that flies exhibit a circadian rhythm in the LoRR, with the greatest sensitivity to alcohol occurring from mid to late night, corresponding to the flies' inactive phase. As predicted, a circadian rhythm in the LoRR was absent in circadian mutant flies and under conditions in which the circadian clock was nonfunctional. Circadian modulation of the response to alcohol was not due to circadian regulation of alcohol absorbance. Similar to other animals, Drosophila develop acute and chronic tolerance to alcohol upon repeat exposures. We found that the circadian clock did not modulate the development of acute alcohol tolerance measured as the difference in sensitivity to alcohol between naïve and pre-exposed flies. Thus, the circadian clock modulates some, but not all, of the behavioral responses to alcohol exposure, suggesting that specific mechanisms underlie the observed circadian modulation of LoRR rather than global cellular circadian regulation. This study provides valuable new insights in our understanding of the circadian modulation of alcohol-induced behaviors that ultimately could facilitate preventative measures in combating alcohol abuse and alcoholism. (Author correspondence: lyons@bio.fsu.edu)     

Endogenous rhythms of locomotion in the American horseshoe crab, Limulus polyphemus

American horseshoe crabs (Limulus polyphemus) exhibit clear circadian rhythms of visual sensitivity in the laboratory and in the field they exhibit seasonal patterns of mating behavior that are closely associated with the tides. Recent reports suggest that Limulus locomotor activity may be controlled by endogenous circadian and/or circatidal clocks and that light:dark (LD) cycles may affect the rhythmic output of both of these clocks. In this study, we examined locomotor behavior in the laboratory to determine the extent of this endogenous activity and to examine the influence of LD cycles on these rhythms. Thirty-three L. polyphemus were captured during the breeding season and their activity was monitored with activity boxes and “running wheels” in seawater kept at constant temperature and salinity. Activity patterns were analyzed using visual inspection of actograms and Chi-square and Lomb-Scargle periodograms. Overall, 36% of the animals was significantly more active during L, while only 12% was more active during D (52% showed no preference). Circatidal rhythms were observed in LD in 67% of the horseshoe crabs. Surprisingly, LD cycles appeared to synchronize these rhythms at times. In DD, the majority of animals tested (63%) exhibited circatidal rhythms that persisted for at least seven days. Overall, the results demonstrate that an endogenously controlled tidal rhythm of locomotion operates during, and significantly after, the breeding season in this species. In addition, the present results are consistent with the presence of circalunidian oscillators controlling these rhythms.     

Circadian and light-induced expression of luciferase in Neurospora crassa

We have constructed a plasmid vector for expressing firefly luciferase in Neurospora crassa under control of the light- and clock-regulated ccg-2 (eas) promoter. The sequence of the luciferase gene in the vector has been modified to reflect the N. crassa codon bias. Both light-induced activity and circadian activity are demonstrated. Expression of luciferase in strains carrying mutant frequency alleles shows appropriate period length alterations. These data demonstrate that luciferase is a sensitive reporter of gene expression in N. crassa. Our results also show that the modified luciferase is expressed in Aspergillus nidulans.     

Cry1C蛋白对4种棉花害虫的致死效果

【背景】苏云金芽胞杆菌(Bt)属革兰氏阳性细菌,是目前世界上应用最广泛的杀虫剂。来自Bt的Cry1Ac基因自1997年商业化以来,其产生的蛋白对棉铃虫、红铃虫等鳞翅目害虫起到了很好的控制作用。但该基因对甜菜夜蛾、斜纹夜蛾、玉米螟等害虫的控制作用较差,因此,需要寻找新的Bt基因亚型控制上述害虫。【方法】将Cry1C蛋白加到人工饲料上形成药膜后,接入低龄幼虫进行生物测定,以常规不加毒蛋白的饲料为对照,计算1、3、5、7 d后不同害虫的校正死亡率。【结果】随着Cry1C蛋白浓度的增加及时间的延长,甜菜夜蛾和斜纹夜蛾的校正死亡率逐渐升高,Cry1C浓度为10μg·m L-1时,处理7 d后,甜菜夜蛾和斜纹夜蛾的校正死亡率分别为100%和85.42%,表明甜菜夜蛾比斜纹夜蛾更敏感,而棉铃虫和玉米螟对Cry1C蛋白的敏感性较差。【结论与意义】Cry1C基因可作为控制棉田甜菜夜蛾和斜纹夜蛾的有价值的候选基因,但是对棉铃虫和玉米螟无效。该研究为筛选新的Bt基因亚型用于防治不同的棉花害虫提供了数据参考。     

Seasonality of circadian locomotor activity in an insect

Daily periodic locomotor activity of Carabus auronitens was recorded in a climate-constant laboratory with the animals exposed to naturally changing photoperiods. Most actograms exhibit directed seasonal variations of duration and phase position of daily activity. Seasonal locomotor activity starts in early spring (following dormancy) on a low daily level, first being confined to a short time span around dusk (and even shorter around dawn). In the course of season, the daily onsets of activity become closely related with sunset and the duration of daily activity is steadily extended with both parts of the bimodal phase fusing to a common, unimodal activity band by late spring. Subsequently, it is further extended into forenoon, until in summer (shortly before aestivation), spontaneous phase inversion turns activity periodicity from nocturnality into diurnality within 1 day. Such seasonal variations are paralleled by changes in the precision of synchronization of the individuals' activity rhythms to the entraining light/dark cycle. No geographical differences were detected. The results support the idea of the circadian clock as a system of two dynamically coupled physiological oscillators that invert their phase relation as soon as the natural dark phase falls short of some minimum-tolerable night length.Abbreviations LD light/dark cycle - nLD natural light/dark cycle - DD constant darkness - endogenous period length - SS sunset - SR sunrise - PRC phase-response curve     

Corazonin- and PDF-immunoreactivities in the cephalic ganglia of termites

Antisera against the pigment-dispersing factor (PDF) and corazonin (Crz) reacted with distinct sets of neurons in the cephalic ganglia of termites. The locations of immunoreactive cells were similar but their numbers differed among the eight species examined: PDF-ir occurred in 0-6 cells in each optic lobe and 1-2 pairs of cells in the subosophageal ganglion (SOG), and Crz-ir in 0-2 pairs of cells in the pars intecerebralis, 3-14 cells in each lateral protocerebrum, and 0-6 pairs of cells in the SOG. Staining patterns were identical in the pseudergates, soldiers, and substitutive reproductives of Prorhinotermes simplex. Workers and soldiers were compared in the remaining 7 species. The only caste divergence was detected in Coptotermes formosanus, in which the soldiers differed from the workers by lack of 4 Crz-ir perikarya in the pars intercerebralis and occasionally also by the absence of 2 Crz-ir perikarya in the SOG. Diurnal changes in PDF-ir and Crz-ir were examined in P. simplex kept under long day (18:6 h light:darkness) or short day (10:14 h) photoperiods. No circadian fluctuations in the distribution or the intensity of immunostaining were found in the pseudergates and soldiers that were sacrificed in 4 h intervals or in the male and female substitutive reproductives examined in 6 h intervals.