Temporal morphology and cap formation in Acetabularia--II. Effects of morphactin and auxin

In order to support the hypothesis that circadian rhythms are implicated in cap formation, experiments were undertaken on the possible time-dependency of the effects of (a) a competitive inhibitor of auxins, morphactin and (b) of auxin (IAA). It was found that: (i) the inhibitory effect of morphactin varies dramatically with the time at which the several weeks' treatment was first begun; (ii) the maximum inhibition varies with development and decreases with time; (iii) IAA accelerates cap formation when the algae are submitted to IAA during the exponential growth phase; the effect is time dependent and decreases with time; (iv) IAA first applied on smaller algae has a transient inhibitory effect which is time dependent; (v) anucleate fragments also respond differentially to an IAA treatment begun at several times in the 24-hr cycle, most clearly when newly formed mRNA have been accumulated and (vi) the effect of iAA is not cumulative with that of a LD shift; that of morphactin is not, or only slightly, improved by a LD shift.     

Temporal Morphology and Cap Formation in Acetabulars-I. Light-Dark Cycle Perturbations

La formation du chapeau, qui constitue un événement morphogénétique de la plus grande importance chez ?'algue Acetabularïa, est influénce par une perturbation unique du cycle lumière-obscurité, done aussi, vraisemblablement, des rythmes circadiens. La perturbation a lieu plusieurs semaines avant ?expression morphogénétique. ? effet est plus marqué sur la formation du chapeau que sur la croissance. Son importance dépend du moment du nyctémère où la perturbation intervient.

?effet dépend du stade de développement de ?'algue: lorsque le transfert d' un régime L-D à un autre a lieu pendant la phase de grande croissance, la formation du chapeau est retardée, mais ? importance de ? effet s'atténue avec le temps. Lorsque le transfert a lieu pendant la phase terminale de croissance (lente), la formation du chapeau est accélérée de façon transitoire. Lorsqu'il a lieu alors que les algues ont presque atteint leur taille finale, il est sans effet. Ces résultats présentent des analogies avec le photopériodisme.

Mots clefs–Acetabularia, rythmes circadiens, morphogénèse, photopériodisme.

Cap formation, a major developmental process in the alga Acetabularia, is influenced by a single perturbation of the entraining light-dark schedule and thus, presumably, of the circadian rhythms. This perturbation is brought about several weeks before cap formation, the most conspicuous expression of morphogenesis in Acetabularia. The effect is more pronounced on cap formation than on growth. It varies in importance with the circadian time at which the perturbation was brought about.

The effect is dependent on the developmental state of the alga: transfer carried out during the logarithmic phase of growth produces a delay whose importance decreases with time. When carried out during the phase of slow terminal growth, the transfer induces a transistory acceleration of cap formation. When the algae approach their final length, no effect is elicited. Photoperiodism seems to be involved.     

Temporal morphology and cap formation in Acetabularia--I. Light-dark cycle perturbations

Cap formation, a major developmental process in the alga Acetabularia, is influenced by a single perturbation of the entraining light-dark schedule and thus, presumably, of the circadian rhythms. This perturbation is brought about several weeks before cap formation, the most conspicuous expression of morphogenesis in Acetabularia. The effect is more pronounced on cap formation than on growth. It varies in importance with the circadian time at which the perturbation was brought about. The effect is dependent on the developmental state of the alga: transfer carried out during the logarithmic phase of growth produces a delay whose importance decreases with time. When carried out during the phase of slow terminal growth, the transfer induces a transitory acceleration of cap formation. When the algae approach their final length, no effect is elicited. Photoperiodism seems to be involved.     

Some aspects of glycoprotein metabolism in Acetabularia: Spatio‐temporal activity of β‐galactosidase and physiological effects of tunicamycin

Abstract

β‐galactosidase has been chosen as an indicator of glycoprotein metabolism in Acetabularia, an unicellular and uninucleate green alga. This catabolic enzyme was quantified by fluorecence spectrometry. It was found at all developmental stages, but the activity levels differed, peaking at the end of the growth phase, at the time of cap morphogenesis initiation, β‐galactosidase activity is also subjected to periodic modulation, displaying a bimodal rhythm with a prominent peak at 16 h. The distribution of the enzyme was examined by cytochemistry, using a substrate analogue (X‐gal). It is present both in the cytoplasm and in the cell wall. No apico‐basal gradient was detectable. The physiological role of glycoproteins was assessed with tunicamycin, an inhibitor of N‐linked glycoprotein synthesis. Two pulses of 3 or 4 h of inhibitor (10 μg ml‐1) always inhibited growth, but more severely during the light period. One pulse may inhibit growth during the light period and stimulate it during the dark one; it may also have little effect, in both periods. Cap formation is inhibited between time 0 and 7. During the dark or subjective dark period, it is often stimulated or not affected. The same results were obtained in constant light. Cap formation is also inhibited in anucleate algae treated during the light period.     

Spatial and foraging behaviour, diet and morphogenesis of postlarvae and juveniles of Pempheris vanicolensis in the Gulf of Aqaba, Red Sea

Post-settlement ecology, ontogenesis of morphology and behaviour were studied in juvenile Pempheris vanicolensis (Pempheridae, Teleostei) in the Gulf of Aqaba, Red Sea. Postflexion larvae of 5.6-6.0 mm total length settled around breakwater heads and natural rocky outcrops of the subtidal zone, widely separated from adults dwelling in groups in coral reef crevices and caves. Settling juveniles formed groups of uniform age and foraged on zooplankton around their habitats. Their circadian behaviour was regulated by levels of illumination in the water, differing slightly in the various age groups. At sunset, juvenile P. vanicolensis migrated and dispersed in deeper water, returning before sunrise to their rocky habitats. Their patterns of foraging and migration behaviours were analysed. At 28.0-32.0 mm total length and 500 mg body weight, the increase in height and length ( H/L ratio) of the juvenile changed from monoto heterochronous, after which a rhomboid body shape, typical for this species, was formed. Concomitantly, the retina of the juvenile changed from a photopic to a scotopic one, the body became heavily pigmented, and the fish left the subtidal rocks, migrating to crevices in coral formations where they settled in close proximity to groups of adult P. vanicolensis .     

Temporal Patterns of Reported Single-Vehicle Car and Truck Accidents in Texas, U.S.A. During 1980-1983

Reported single car and truck accidents due specifically to driver 'fatigue' for the 4-year span of 1980-1983 were analyzed for 24-hr, 7-d and 1-yr patterns. Three types of data were examined: (1) accidents in rural Texas, (2) accidents only in San Antonio, the fourth largest city in Texas and (3) accident ratio (number of accidents per time interval divided by traffic volume for the interval) in this city.

A statistically significant seasonal variation of relatively low amplitude with peaks in May and July was detected only for accidents in rural areas. High-amplitude periodicities of 7 d were evident in all the data sets, with a peak on the weekend. A very prominent 24-hr pattern was detected as well, with the acrophase determined by single cosinor around 0300. A slight secondary peak in accidents, around 1500, was evident in the data from the rural areas. This secondary peak represented a 12-hr rhythm in addition to the 24-hr. Overall, features of the temporal patterns in accidents over 24 hr and over the year in urban and rural areas differed only slightly. Accident ratios yielded results similar to accident frequencies. However, with regard to the rural data, the shape of the 24-hr temporal pattern varied with driver age; older drivers exhibited a flatter curve with a more pronounced afternoon rather than early morning (around 0300) peak.     

Effect of morphactin on stem growth in relation to auxin in precooled rooted tulip bulbs

Effect of morphactin IT 3456, an auxin transport inhibitor, on tulip stem elongation induced by indole-3-acetic acid (IAA) was investigated. Tulip stem growth induced by IAA 0.1 % in lanolin paste applied on the top internode after excision of flower bud and removal of all leaves was greatly inhibited by 0.2 % morphactin IT 3456 applied on the 4th, 3rd, 2nd and 1st internode. The inhibitory effect of the morphactin on tulips stem growth promoted by IAA was restored by additional application of IAA below the morphactin treatment place. Morphactin inhibited also the growth of all internodes induced by flower bud in the absence of leaves. These results suggest a crucial role of auxin in the control growth of all internodes in tulip stem.     

生长素受体与信号转导机制研究进展

对生长素受体ABP1和TIR1及调控泛素化蛋白降解的生长素信号转导途径研究进展进行综述。     

Effects of Li+, Rb+ and tetraethylammoniumchloride on the locomotor activity rhythm of Musca domestica

Abstract

The effect of Li⁺, Rb⁺ and tetraethylammoniumchloride (TEA) on the locomotor activity rhythm of Musca domestica was studied. Li⁺ as well as TEA lengthen the free run period t. This effect was more pronounced in animals with shorter period lengths. The effect of Rb? depends on the previous period length. In flies which had a short period, Rb⁺ lengthened, and in those with a long period Rb⁺ shortened t. Replacing the Li⁺ solution with water reverted the period lengthening partly. In the case of Rb? and TEA the rhythm became obscured after replacing the solutions with water. The involvement of K⁺ ions and transport ATPases in the expression of circadian rhythms is discussed.     

Temperature Dependency of Circadian Period in a Single Cell (Acetabularia)

The circadian rhythm in the oxygen production of 30 individual Acetabularia cells has been studied at different temperatures. The temperature induced period variation was continuously evaluated over the whole data record of each individual cell with an advanced spectral analysis technique. The observed circadian periods of O₂ production displayed a well established region of temperature compensation between 25 °C and 30 °C with a Q₁₀, value of 0.9, whereas between 15°C and 22°C a positive temperature coefficient was measured (Q₁₀ at 22 °C 0.9, Q₁₀ at 20°C 0.8, Q₁₀at 17°C 0.7).     

Effects of IAA and four IAA conjugates on morphogenesis and callus growth from tomato leaf discs

The effects of indole-3-acetic acid (IAA) and four IAA conjugates, indoleacetylalanine (IAAla), indoleacetylaspartic acid (IAAsp), indoleacetylglycine (IAGly), and indoleacetylphenylalanine (IAPhe), on growth and morphogenesis in tomato leaf discs in vitro were examined. Free IAA stimulated root initiation in the absence of cytokinin and stimulated callus growth in the presence of 0.89 M benzylaminopurine (BAP). Free IAA also inhibited shoot initiation obtained with 8.9 M BAP. The activities of the IAA conjugates depended on the conjugating amino acid, the concentration of the conjugate, and the response being measured. IAAsp had little or no activity in promoting root initiation or callus growth or in inhibiting shoots, while IAPhe was similarly inactive except at the highest concentration tested (100 M). IAAla and IAGly were both very active in inhibiting shoots and promoting callus growth, but were much less active in stimulating rooting, except at 100 M, at which concentration they were as effective as free IAA. Thin-layer chromatography of the IAA conjugates revealed that IAAla, IAGly and IAPhe were largely stable to autoclaving, but that IAAsp underwent some hydrolysis to products identical with free IAA and aspartic acid. Pretreatment of seedlings with IAA, IAAla or IAGly altered the subsequent shoot initiation response from leaf discs on media with and without IAA.     

Twofold effect of blue light on a circadian rhythm in Acetabularia

Abstract

The circadian chloroplast migration in Acetabularia mediterranea was monitored by continuously measuring the transmission of the cells near the apex. Under continuous red light the amplitude of the rhythm decreased rapidly within a few days. However, circadian changes of chloroplast density were still detectable even after 28 days of red light, indicating the persistence of the rhythm. When blue light was added after red light preirradiation of several days phase shifts were observed which were expressed as advances as well as delays. The period of the rhythm proved to be strongly dependent on the intensity of the continuous blue light which was given in addition to red light. Different red light intensities did not change the period. The occurrence of both effects indicates that the sensory transduction of blue light photoreception in Acetabularia works in two different ways: quanta counting processes and processes of light intensity measurement.     

生物钟在卵巢生理和病理中的作用

哺乳动物的昼夜节律是基因编码的分子钟在体内产生的一种以大约24 h为周期的生理现象,使机体的生理过程与外界环境的变化相协调,是对环境适应的一种表现.在哺乳动物中,繁殖生理功能受生物钟系统的调节.在下丘脑-垂体-卵巢(hypothalamic-pituitary-ovarian,HPO)轴的各组织中均已观察到生物钟基因的...     

Effects of nutritional lithium deficiency on behavior in rats

To demonstrate whether nutritional lithium deficiency is associated with behavioral changes, male Sprague-Dawley rats were placed on a lithium-deficient diet (Li content <.01 ppm). A lithium-deprived group, receiving drinking water containing 31 μM NaCl, were compared to a control group receiving drinking water containing 31 μM LiCl. Growth and general appearance were the same in both groups. However, lithium-deficient animals demonstrated decreased aggression in social interactions with other rats and also in response to handling. The phase of wheel-running activity was delayed by 0.8 h and exhibited decreased amplitude (p<.05). Other behaviors, including acquisition and retention of a passive avoidance response, were unaffected by lithium deprivation. An erratum to this article is available at .     

Effects of isoflurane on measurements of delayed lumininescence in Acetabularia acetabulum.

The volatile halogenated methyl ethyl ether, isoflurane, used as an anaesthetic, inhibits actin-based dynamics directly or indirectly in animal cells. In plant cells, most intracellular movements are related to actin pathways. We have used isoflurane in a unicellular alga, Acetabularia acetabulum, to test the dynamics of choloroplast organization. By measuring the delayed luminescence, we found that isoflurane worked efficiently in the unicellular organism and showed dose- and time-course-dependent actin-inhibition patterns. When A. acetabulum was treated with saturated solutions of isoflurane in artificial seawater (defined as 100% isoflurane) for 3 or 6 min, the delayed luminescence (DL) was decreased and was never recovered. In contrast, if treated with 75% diluted isoflurane, the DL was firstly inhibited and then recovered several hours later, and if treated with 50% diluted isoflurane, the change of DL was small. Our work proved that isoflurane can affect actin-related pathways in both animals and plants.     

Behavioral and Neurochemical Effects of Fencamfamine on Rats: A Chronobiologic Approach

Fencamfamine (FCF) is a psychostimulant classified as an indirect dopaminergic agonist. Circadian rhythms of some behavioral and neurochemical parameters were investigated in control rats and in rats which had been treated with a single dose of FCF across the 24-hr span. Rats were entrained to light/dark (LD) 12:12, lights on from 0700 to 1900. In behavioral experiments (performed in March) the rats were injected intraperitoneally with saline or FCF (3.5 mg/kg) at one of six times: 0900, 1300, 1700, 2100, 0100 or 0500. Fifteen minutes after treatment the duration of sniffing, rearing and locomotion was recorded during 120 min. Controls showed circadian rhythms for sniffing and rearing with acrophases at 2255 and 0118, respectively. In animals treated with FCF, only locomotion displayed significant circadian variation with acrophase at 1912. Two-way analysis of variance (ANOVA) showed a statistically significant circadian time-dependent effect of FCF on all behavioral parameters studied; the increase of sniffing, rearing and locomotion induced by FCF was higher in rats treated during the rest phase. In the biochemical studies (performed between March-June), rats were treated (i.p.) with saline or FCF (10 mg/kg) at one of four times: 0900, 1700, 2100 or 0100. The levels of homovanillic acid (HVA) in the striatum and tuberculum olfactorium, 5-hydroxyindolacetic acid (5-HIAA) in the cerebellum and 3-methoxy-4-hydroxypheniglycol (MHPG) in the frontal cortex were determined. Controls showed circadian rhythms for HVA (striatum), MHPG (frontal cortex) and 5-HIAA (cerebellum) with acrophases at 2233, 1955 and 1029, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Behavioral and Neurochemical Effects of Fencamfamine on Rats: A Chronobiologic Approach

Biological Rhythms in Clinical and Laboratory Medicine. Edited by Y. Touitou and E. Haus. Berlin, Heidelberg, New York Springer-Verlag, 1992, 730 pp. (347 figures and 54 tables), $210.     

Circadian rhythms and the evolution of photoperiodic timing in insects

This review discusses possible evolutionary trends in insect photoperiodism, mainly from a chronobiological perspective. A crucial step was the forging of a link between the hormones regulating diapause and the systems of biological rhythms, circadian or circannual, which have independently evolved in eukaryotes to synchronize physiology and behaviour to the daily cycles of light and darkness. In many of these responses a central feature is that the circadian system resets to a constant phase at the beginning of the subjective night, and then ‘measures’ the duration of the next scotophase. In ‘external coincidence’, one version of such a clock, light now has a dual role. First, it serves to entrain the circadian system to the stream of pulses making up the light/dark cycle and, second, it regulates the nondiapause/diapause switch in development by illuminating/not illuminating a specific light sensitive phase falling at the end of the critical night length. Important work by A. D. Lees on the aphid Megoura viciae using so‐called ‘night interruption experiments' demonstrates that pulses falling early in the night lead to long‐day effects that are reversible by a subsequent dark period longer than the critical night length and also show maximal sensitivity in the blue–green range of the spectrum. Pulses falling in the latter half of the night, however, produce long‐day effects that are irreversible by a subsequent long‐night and show a spectral sensitivity extending into the red. With movement to higher latitudes, insects develop genetic clines in various parameters, including critical night length, the number of long‐night cycles needed for diapause induction, the strength of the response, and the ‘depth’ or intensity of the diapause thus induced. Evidence for these and other types of photoperiodic response suggests that they provided strong selective advantages for insect survival.