Mosquito circadian and circa-bi-dian flight rhythms: a two-oscillator model

Summary Circadian rhythmicity was found in the flight activity ofCuliseta incidens recorded in constant darkness for up to 14 weeks. The first nonhuman circa-bi-dian (about-two-day) rhythms were also found (Figs. 6–7). Circadian periods were either stable, remaining <24h (Fig. 1), or labile, with a change from <24h to >24 h (Fig. 2). Inactivity phenomena (day-skipping) were common in the latter group only (Fig. 5). The period at activity onset was much more labile than the period at offset (Fig. 4). The activity patterns of some period-lengthened animals suggested control by two oscillators which could temporarily or permanently uncouple (Figs. 8–9).A pacemaker model consisting of a labile evening (E) oscillator mutually coupled to a stable morning (M) oscillator is the most economical proposal which can account for these results. The view that E and M uncouple and run with different periods can account for many records in which the period was labile. Circa-bi-dian rhythms can be explained by the period of E lengthening to where it synchronizes with M in a 21 mode. Thus, E and M are proposed to behave similarly to the human activity and temperature oscillators. It is speculated that day-skipping might indicate that E oscillates between circadian and circa-bi-dian ranges without overt activity being expressed.Abbreviations LD1212 alternating 12h light, 12h dark - DD constant dark - LL constant light - period of rhythm - _on period at activity onset - _off period at activity offset - activity time - mean activity time     

Rest in the scorpion — a sleep-like state?

Summary Forest-dwelling scorpions (Heterometrus, Pandinus) were continuously observed by time-lapse video recording and their behavior and body position were analyzed. Activity recorded on the tapes was scored into three states: (1) activity, (2) alert immobility, and (3) relaxed immobility. Arousal thresholds were determined by mechanical stimulation. Responsiveness was highest during activity and alert immobility, and significantly lower during relaxed immobility. Heart rate was continuously measured by chronically implanted electrodes and related to the behavioral state. Heart rate was highest during activity, intermediate in alert immobility, and lowest during relaxed immobility. Activity bouts were associated with sudden increases in heart rate. Settling down, however, was associated with a progressive decline in heart rate.The presence of rest regulation was investigated by 12 h rest deprivation by mechanical stimulation. During recovery, after initial activation, alert immobility and relaxed immobility were decreased.It can be concluded that rest in the scorpion is not a homogeneous state. The subdivision into alert and relaxed immobility on the basis of body posture revealed differences in arousal threshold and heart rate between the two states. The compensation of rest after rest deprivation indicates the presence of regulatory mechanisms comparable with those present in mammals and several nonmammalian vertebrate species, thus providing evidence for a sleep-like state in scorpions.Abbreviations SD sleep deprivation - L light - D dark or dim - LD light-dark or dim - H Heterometrus - P Pandinus     

A comparative study of enzyme activity variation between α-glycerophosphate and alcoholdehydrogenases in Drosophila melanogaster

An intraspecific comparison of -glycerophosphate (-GPDH: E.C.1.1.1.8) and alcohol dehydrogenase (ADH: E.C.1.1.1.1) enzyme activity levels was carried out in Drosophila melanogaster. The results indicate that (1) -GPDH is a relatively conservative and ADH a relatively variable enzyme system with regard to structurally determined activity variation but that (2) the conservative nature of -GPDH activity variation does not extend to the intra-genotypic level. The results are consistent with the view that different kinds of selective pressures are being exerted on the enzyme's structural and modifier gene loci.     

Entrainment of the circadian system of the house sparrow: A population of oscillators in pinealectomized birds

Summary Removal of the pineal gland modifies the entrainment behavior of house sparrows. Abnormal entrainment occurs in pinealectomized sparrows exposed to skeleton photoperiods (light cycles composed of 2 pulses of light per 24-h cycle). This abnormal entrainment depends upon the state of the locomotor activity (rhythmic or arrhythmic) before exposure to the light cycle, and upon the interval between the 2 pulses of light which constitute the skeleton photoperiod. The conditions that produce abnormal entrainment in pinealectomized birds are strongly correlated with those that produce 2 stable phases of entrainment to skeleton photoperiods in normal birds (bistability phenomenon). These results suggest that after pinealectomy, there remains a population of oscillators whose combined output is reflected in the locomotor activity of individual sparrows.Abbreviations LD 12 12 light-dark cycle with 12 h of light and 12 h of dark per 24-h cycle - CT circadian time     

Circadian rhythms of corneal mitotic rate,retinal melatonin and immunoreactive visual pigments,and the effects of melatonin on the rhythms in the Japanese quail

We investigated circadian ocular rhythms in the Japanese quail, Coturnix coturnix japonica. The birds were placed under light-dark cycles (LD 1212), constant light (LL) and constant darkness (DD), and the retinas were dissected out at four-hour intervals throughout 24 h. Following measurements were performed. (1) Melatonin content in the retina was measured by radioimmunoassay. It was low in light and several folds higher in darkness under LD 1212. The rhythm continued in DD, but disappeared in LL. (2) Mitotic figures in the corneal epithelium were counted. Similar rhythms to the melatonin content were observed in the corneal mitotic rate with a slight phase delay. (3) The retinas were fixed at 4-h intervals and immunostained with anti-bovine rhodopsin serum and anti-chicken iodopsin monoclonal antibodies. The outer segments of photoreceptor cells were stained intensively throughout 24 h in LD 1212, LL and DD. In contrast, the stainability of the locus close to the outer limiting membrane where the Golgi apparatus exists changed diurnally. Scores showing the ratio of cells with positive staining indicated high values from 4 h after the onset of light to the beginning of dark phase under LD 1212. The values were high throughout 24 h in LL and intermediate or low in DD. (4) To investigate the effect of melatonin on the corneal mitotic rate and visual pigments at the Golgi region, melatonin was injected into one eye and saline into the contralateral eye. Melatonin induced a phase advance in the corneal mitotic rate under LD 1212, but did not induce a rhythm under LL. The ratio of photoreceptor cells with positive staining to anti-visual pigment antibodies at the Golgi region was not affected by melatonin injection.Abbreviations ANOVA analysis of variance - BSA bovine serum albumin - DD constant darkness - Io-mAb monoclonal antibodies against chicken iodospin - LD light-dark - LL constant light - mRNA messenger ribonucleic acid - PBS phosphate buffer solution - Rh-As antiserum against bovine rhodopsin - SCN suprachiasmatic nucleus - T transducin - T transducin      

Na+-translocating NADH-quinone reductase of marine and halophilic bacteria

The respiratory chain of marine and moderately halophilic bacteria requires Na⁺ for maximum activity, and the site of Na⁺-dependent activation is located in the NADH-quinone reductase segment. The Na⁺-dependent NADH-quinone reductase purified from marine bacteriumVibrio alginolyticus is composed of three subunits, , , and , with apparentM _r of 52, 46, and 32kDa, respectively. The FAD-containing -subunit reacts with NADH and reduces ubiquinone-1 (Q-1) by a one-electron transfer pathway to produce ubisemiquinones. In the presence of the FMN-containing -subunit and the -subunit, Q-1 is converted to ubiquinol-1 without the accumulation of free radicals. The reaction catalyzed by the -subunit is strictly dependent on Na⁺ and is strongly inhibited by 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO), which is tightly coupled to the electrogenic extrusion of Na⁺. A similar type of Na⁺-translocating NADH-quinone reductase is widely distributed among marine and moderately halophilic bacteria. The respiratory chain ofV. alginolyticus contains another NADH-quinone reductase which is Na⁺ independent and has no energy-transducing capacity. These two types of NADH-quinone reductase are quite different with respect to their mode of quinone reduction and their sensitivity toward NADH preincubation.     

Phytochrome-mediated induction of phenylalanine ammonia-lyase in the cotyledons of tomato (Lycopersicon esculentum Mill.) plants

Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5.) induction in cotyledons from 96-h dark-grown Lycopersicon esculentum Mill. was studied in response to continuous light and hourly light pulses (blue, red, far red). The increases of PAL promoted by blue and red pulses are reversed completely by immediately following 758 nm irradiations. The response to continuous red light could be substituted for by hourly 6-min red light pulses. The effect of continuous red treatments is mainly due to a multiple induction effect of phytochrome. In contrast to red light, hourly light pulses with far red and blue, light can only partially substitute for continuous irradiation. The continuous blue response could be due to a combination of a multiple induction response and of a high irradiance response of phytochrome. The continuous far red response, could represent a high irradiance response of phytochrome. Dichromatic irradiations indicate that phytochrome is the photoreceptor controlling the light response (PAL) in tomato seedlings.Abbreviations Norflurazon NF-4-chloro-5-(methylamino)-2-(,,,-trifluoro-m-tolyl)-3 (2H) pyridazinone - PAL phenylalanine ammonia-lyase - phytochrome photoequilibrium P_fr/P_tot - P_fr far-red absorbing form of phytochrome - P_r red absorbing form of phytochrome - P_tot total phytochrome: P_r+P_fr     

Entrainment and phase shifting of the circadian rhythm of cell division by light in cultures of the achlorophyllous ZC mutant ofEuglena gracilis

The photosynthesis-deficient ZC mutant ofEuglena gracilis Klebs (strain Z) was cultured at 16°C on an aerated, magnetically stirred, mineral medium containing 0.1% ethanol (pH 7.0). Cell division could be entrained by a 12: 12 light: dark cycle (LD: 12, 12) or even by a one-pulse skeleton photoperiod (LD: 1,23) The rhythm free-ran in DD for at least 8 days with a circadian period (=25.5 h) in populations that had been previously entrained by LD. The freerunning rhythm could be phase-shifted by a single 1-h light pulse (3000 lx). The strong (Type 0) phase-response curve derived from the resetting effects of such signals given at different circadian times was similar to that for the photosynthetic wild-type strain. These results demonstrate that the presence of a functional chloroplast compartment is not necessary for the circadian clock to function inEuglena and suggest that phase resetting of the circadian clock by light occurs via a similar pathway in both photosynthetic and non-photosynthetic cell types.     

Limits of maternal entrainment of the activity rhythm in the field mouseMus booduga

Summary Cycles of 12 h presence and 12 h absence of motherMus booduga entrain the circadian rhythm in the locomotor activity of her pups such that the pups rest in her presence and are active in her absence. We wanted to determine whether this maternal entrainment arises because activity is inhibited by the mother's presence and enhanced by her absence (masking). We performed experiments with the period of the presence/absence cycles ranging from 20 to 28 h and find that only periods of 23–25 h allow entrainment while periods below 23 h and above 25 h do not allow entrainment. Our results speak against the involvement of masking and in favour of the involvement of a genuine circadian organization.Abbreviations PA presence and absence of mother - LD light and darkness - DD continuous darkness - T period of Zeitgeber - period of activity rhythm - phase angle difference     

The effect of different night conditions on the CO2 fixation in a lichen Xanthoria parietina

CO₂ fixation was studied in a lichen, Xanthoria parietina, kept in continuous light, and with cyclic changes in light intensity, dark period or temperature. The diurnal and seasonal courses of CO₂ exchange were followed. The rate of net photosynthesis was observed to fall from morning to evening, and this decline was more pronounced in winter than in summer. The maximal net photosynthetic rate, 223 ng CO₂g^-1dws^-1, occured in winter and the minimum, 94 ng CO₂g^-1dws^-1, late in spring. The light compensation point in summer was four times as high as in winter. In continuous light (180 or 90 mol photons m^-2s^-1, 15°C) net photosynthesis decreased noticeably during one week, falling below the level maintained in a 12 h light: 12 h dark cycle. Photosynthetic activity did not decrease, however, in lichens held in continuous light (90 mol photons m^-2s^-1) with cyclic changes of temperature (12 h 20 °C: 12 h 5 °C). Active photosynthesis was also maintained in light of cyclically changing intensity (12 h: 12 h, 15 °C) when night-time light was at least 75% lower than illumination by day. A dark period of 4 hours in a 24-h light:dark cycle was sufficient to keep CO₂ fixation at the control level. It seems that plants need an unproductive period during the day to survive and this can be induced by fluctuations in light and/or temperature.     

Etude du phytochrome des graines de Pinus nigra Arn par spectrophotométrie bichromatique in vivo

Summary Phytochrome photoconversions P_rP_fr and P_frP_r can be measured by differential spectrophotometry in dry seeds (6% water content) of Pinus nigra Arn. A red light irradiation given before imbibition induces germination when the seeds are subsequently wetted and kept in darkness.In continuous darkness the phytochrome content shows a drastic increase at the beginning of moistening.The detectable pigment is entirely in the P_r form. The normal P_frP_r dark reversion is observed. P_fr destruction does not take place.     

The MHC haplotypes of the chicken

The major histocompatibility complex (MHC) of Gallus gallus is the B complex of which three classes of cell-membrane antigens have been clearly defined by serological, histogenetic, and biochemical methods. Two of these classes are homologous to classes I and II of mammals (B-F and B-L, respectively), while the third (B-G) is a differentiation antigen of the erythroid cell-line; the mammalian homologue of this class is still undefined. The B haplotypes comprise at least one gene of each class that displays linkage disequilibrium of a remarkable strength. The present work is the first systematic comparison by serological and histogenetic methods of the allelic products (allomorphs) of 15 haplotypes, including all of the 11 that were accepted as standard B haplotypes at the recent international Workshop on the chicken MHC in Innsbruck, Austria. The analysis has revealed many similarities, but only four pairs of probable identities: G2 and G12, F4 and F13, L4 and L13, L12 and L19. It appears therefore that the B-G locus is comparable in its degree of polymorphism to the class I (B-F) locus. The standard haplotypes are almost all of White Leghorn derivation, and preliminary typings of other breeds of chickens, and of wild chickens, indicate the existence of a much wider spectrum of allomorphs.     

Light-sampling behavior in photoentrainment of a rodent circadian rhythm

Summary Behavioral aspects of photoentrainment of circadian locomotor activity rhythms were recorded for a nocturnal den-dwelling rodent, the flying squirrel,Glaucomys volans. Methods included both telemetric monitoring and infrared observations of animals under constant dark (DD) or light-dark (LD) schedules in either standard wheel cages or in newly developed simulated den cages. By means of the den cages, several aspects of a circadian activity cycle could be simultaneously measured emphasizing the arousal from rest, the light-sampling behavior by which a squirrel assessed the environmental photoregimen, and the phase-shifting by which photoentrainment was achieved. Each animal in a den cage remained for 12 or more hours of its rest period almost exclusively in the darkened nest box, then at an abrupt arousal time moved to the light-sampling porthole. In darkness each animal initiated wheel activity immediately after arousal; light at arousal time, however, induced a return to the nest box for a nap and a delay phase-shift in onset of activity of approximately 40 min. On subsequent days, each animal appeared to be free-running ( _FR< 24 h) until onset again advanced into the light period. A squirrel usually viewed only a few minutes light per day, and on free-running days occasionally saw none of the 12-h light period. The significance of these data for theories of circadian photoentrainment is discussed.Abbreviations CT circadian time - PRC phase response curve - SCN suprachiasmatic nucleus     

Circadian organization in the pigeon,Columba livia: the role of the pineal organ and the eye

Summary The roles of the pineal organ and the eye in the control of circadian locomotor rhythmicity were studied in the pigeon (Columba livia). Neither pinealectomy nor blinding abolished the circadian rhythms in constant dim light conditions (LLdim). All the pinealectomized birds and the blinded birds entrained to light-dark (LD) cycles with no discernible anticipatory activity. However, the birds which had been both pinealectomized and blinded showed no circadian rhythms in prolonged LLdim. These birds entrained to LD cycles with anticipatory activity and showed residual rhythmicity for a while after transfer from LD cycles to LLdim. Continuous administration of melatonin induced suppression of the circadian rhythms and reduced total amount of locomotor activity in LLdim. These results suggest that not only the pineal organ but also the eye (perhaps the retina) is involved in the pigeon's circadian system.Abbreviations NAT N-acetyltransferase - LLdim constant dim light - cadian period - SCN suprachiasmatic nucleus - circadian activity time - LD light-dark     

Kinetics of the flash-induced electrochromic absorbance change in the presence of background illumination. Turnover rate of the electron transport. II. Higher plant leaves

The flash-induced electrochromic absorbance change (A ₅₁₅) was measured in leaves of higher plants in the absence and presence of continuous monochromatic background illumination of different intensities and wavelengths. The variation of the amplitude of A ₅₁₅ in background light was used to estimate the steady-state turnover time of the electron transport. In red light we obtained about 5 msec which was accounted for by the turnover of the linear electron transport. With far red background illumination or in the presence of the photosystem 2 inhibitor, DCMU, the steady-state turnover time tentatively assigned to photosystem 1 cyclic electron transport was much larger (100 msec).Increasing the intensity of background illumination with far red light gradually diminished the slow rise of A ₅₁₅ in parallel with suppression of the initial rise generated by photosystem 1. At high intensities of the red light, however, while A ₅₁₅ was attenuated, the slow rise was not eliminated and its proportion relative to the initial rise did not vary appreciably.     

Neuroanatomy of the terminal (sixth abdominal) ganglion of the crayfish,Procambarus clarkii (Girard)

Summary We studied the neuroanatomy of the terminal (sixth abdominal) ganglion in the crayfish Procambarus clarkii with silver-impregnated sections and nickel fills. We describe the fiber tracts, commissures and neuropilar areas, and give the topological relationships of motoneurons and intersegmental interneurons with reference to their neuropilar landmark structures.All five anterior abdominal ganglia have an almost identical number of 600–700 neurons with a similar pattern of distribution. Each contains a single neuromere with a common plan of neuropil organization. In contrast, the terminal ganglion consists of two neuromeres which appear to be derived from the intrinsic sixth abdominal and telson ganglion. The basic organization of each neuromere parallels that of the third abdominal ganglion in the appearance and arrangement of fiber tracts and commissures, although some modifications occur. The fusion of two neuromeres is represented by the duplication of segmentally homologous neurons, MoGs and LGs, whose topological relationships to the neuropil structures are similar to those of the anterior ganglion.We also discuss the origin of the telson and its ganglion (the seventh abdominal neuromere), and dispute the classical theory that the telson derives from a postsegmental region.     

Unusual discharge patterns of single fibers in the pigeon's auditory nerve

Summary Extracellular recording from single auditory nerve fibers in the pigeon,Columba livia, revealed some unusual discharge patterns of spontaneous and evoked activity.Time interval histograms (TIHs) of spontaneous activity showed a random interval distribution in 73% of the auditory fibers (Fig. 1a). The remaining 27% revealed periodicity in the TIHs (Fig. 1b–e), determined by the characteristic frequency (CF) of a given fiber. Normally, those fibers had a CF<2.2 kHz. In both cases spontaneous activity was irregular.The time pattern of quasiperiodic spontaneous firing in different auditory fibers is described by three main types of autocorrelation histograms (ACHs; decaying, nondecaying, and modulated), reflecting the spontaneous oscillations of the hair cell membrane potential (Fig. 1b–d).Single-tone suppression in auditory fibers with quasi-periodic spontaneous activity was found (Figs. 2, 10) and it could be observed if the eighth nerve was cut. There was no suppressive effect in fibres with random spontaneous firing.The frequency selectivity properties of auditory fibers were studied by means of an automatic method. Both simple (Fig. 4) and complex (Figs. 7, 8) response maps were found. Apart from the usual excitatory area, complex response maps were characterized by suppressive areas lying either above (Fig. 7), below (Fig. 8e), or on both sides of the CF (Fig. 8a–c). Generally, complex response maps were observed for fibers showing quasiperiodic spontaneous activity (Figs. 7, 8).Input-output functions at frequencies evoking single-tone suppression were nonmonotonic, while they were always monotonic at frequencies near the CF (Fig. 12).No difference in sharpness was observed between normal frequency threshold curves (FTCs) and exitatory areas of complex response maps (Fig. 9).On-off responses evoked by suppressive stimuli were found (Figs. 2, 3). They had a periodic pattern determined by the CF and did not depend on the stimulus frequency (Fig. 3).Low-CF fibers were observed which changed their time discharge structure to tone levels about 45 dB lower than their thresholds at the CF (Fig. 6).The observed features of the discharge patterns of the pigeon's auditory fibers reflect the distinctive nature of the fundamental mechanisms of auditory analysis in birds that are connected with electrical tuning of the hair cells and probably with the micromechanics of the bird's cochlea.Abbreviations ACH autocorrelation histogram - BP base period - CF characteristic frequency - FTC frequency threshold curve - IHC inner hair cell - OHC outer hair cell - PSTH peristimulus time histogram - TIH time interval histogram     

Poly(ethylene glycol) precipitation and two aqueous-phase separation of progesterone 11-α hydroxylase from Rhizopus nigricans

Summary Poly(ethylene glycol) precipitation and two aqueous phase separation were examined as possible techniques for the large scale isolation of a microsomal fraction enriched in 11- progesterone hydroxylase activity from the filamentous fungus Rhizopus nigricans. Both techniques concentrated the enzyme and increased its specific activity between 1.5 and 2.0-fold, but with low yield. Cell debris needed to be removed before PEG precipitation and also before two aqueous phase separation.     

Basal Forebrain Cholinergic Immunolesion by 192IgG-Saporin: Evidence for a Presynaptic Location of Subpopulations of α2-and β-Adrenergic as Well as 5-HT2A Receptors on Cortical Cholinergic Terminals

To study whether the changes in cortical noradrenergic and serotonergic mechanisms observed in patients with Alzheimer's disease are the consequence of reduced cortical cholinergic activity, a novel cholinergic immunotoxin (conjugate of the monoclonal antibody 192IgG against the low-affinity nerve growth factor receptor with the cytotoxic protein saporin, 192IgG-saporin) was used to produce a specific and selective loss of cholinergic cells in rat basal forebrain nuclei. To correlate the responses to cholinergic immunolesion in cholinoceptive cortical target regions with cholinergic hypoactivity, quantitative receptor autoradiography to measure adrenoceptors and 5-hydroxytryptamine (5-HT) receptor subtypes, and histochemistry to estimate acetylcholinesterase activity, were performed in adjacent brain sections. ₁-adrenoceptor and 5-HT_1A receptor binding were not affected by cholinergic immunolesion in any of the cortical and hippocampal regions studied. However, cholinergic immunolesion resulted in significantly reduced ₂-and -adrenoceptor as well as 5-HT_2A receptor binding in a number cortical and hippocampal regions displaying a reduced activity of acetylcholinesterase, already detectable seven days after a single injection of 192IgG-saporin and persisting up to three months post lesion without any significant recovery. The data suggest that at least a subpopulation of ₂-and -adrenoceptor as well 5-HT_2A receptor subtype is present on cortical and hippocampal cholinergic terminals originating in the basal forebrain. The lesion-induced receptor changes suggest that the alterations in cortical 5-HT₂ receptor binding observed in patients with Alzheimer's disease might be secondary to the cholinergic deficits.     

Intraspecific variation of spectral sensitivity in threespine stickleback (Gasterosteus aculeatus) from different photic regimes

To examine the influence of the spectral characteristics of underwater light on spectral sensitivity of the ON and OFF visual pathways, compound action potential recordings were made from retinal ganglion cells of threespine stickleback from different photic regimes. In fish from a red-shifted photic regime (P₅₀ 680 nm for downwelling light at 1m), peak sensitivity of both the ON and OFF pathways was limited to long wavelength light (_max 600–620). In contrast, the ON pathway of fish from a comparatively blue-shifted (P₅₀ 566 nm) photic regime exhibited sensitivity to medium (_max 540–560) and long (_max 600 nm) wavelengths, while the OFF pathway exhibited peak sensitivity to only medium (_max 540 nm) wavelength light. In a third population, where the the ambient light is moderately red-shifted (P₅₀ 629 nm), the ON pathway once again exhibited only a long wavelength sensitivity peak at 620 nm, while the OFF pathway exhibited sensitivity to both medium (_max 560 nm) and long (_max 600–620 nm) wavelength light. These findings suggest that the photic environment plays an integral role in shaping spectral sensitivity of the ON and OFF pathways.