Zebrafish Clock rhythmic expression reveals independent peripheral circadian oscillators.

The only vertebrate clock gene identified by mutagenesis is mouse Clock, which encodes a bHLH-PAS transcription factor. We have cloned Clock in zebrafish and show that, in contrast to its mouse homologue, it is expressed with a pronounced circadian rhythm in the brain and in two defined pacemaker structures, the eye and the pineal gland. Clock oscillation was also found in other tissues, including kidney and heart. In these tissues, expression of Clock continues to oscillate in vitro. This demonstrates that self-sustaining circadian oscillators exist in several vertebrate organs, as was previously reported for invertebrates.

Morphology of the Antenna of Hermetia illucens (Diptera: Stratiomyidae): An Ultrastructural Investigation.

The black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), is a relevant species in waste and pest management, but is also of forensic and medical importance. A scanning electron microscopy (SEM) investigation of the antennae of both sexes of H. illucens is presented here for the first time. The antenna is composed of three regions: the scape, the pedicel, and the flagellum. The first two regions are single segments, whereas the third region, the longest one, is composed of eight flagellomeres. The scape and pedicel have microtrichia, chaetic sensilla, and rounded perforations. The flagellum is covered by different microtrichia, the morphology of which is described in detail. Two types of sensory pit are found on flagellomeres 1 to 6. An oval depression with trichoid sensilla extends from flagellomeres 4 to 6. On both sides of flagellomere 8 is a lanceolate depression covered by hair-like microtrichia. Morphometric and morphological analyses revealed some sex-related differences. The results of the SEM investigations are compared with those obtained on other species of the family Stratiomyidae and other brachyceran Diptera. The possible role of sensilla in sensory perception is also discussed in comparison with nondipteran species.

PASting together the mammalian clock.

Over the past year, the first components of the mammalian clock have been identified; Clock, bmal1 and three homologs of Drosophila period have been cloned, all of which encode PAS proteins. Expression of the mammalian period gene oscillates in many tissues in vivo and in immortalized cell cultures in vitro. Now, can we say that every cell has a circadian clock?

Studying the Evolution of the Vertebrate Circadian Clock: The Power of Fish as Comparative Models.

The utility of any model species cannot be judged solely in terms of the tools and approaches it provides for genetic analysis. A fundamental consideration is also how its biology has been shaped by the environment and the ecological niche which it occupies. By comparing different species occupying very different habitats we can learn how molecular and cellular mechanisms change during evolution in order to optimally adapt to their environment. Such knowledge is as important as understanding how these mechanisms work. This is illustrated by the use of fish models for studying the function and evolution of the circadian clock. In this review we outline our current understanding of how fish clocks sense and respond to light and explain how this differs fundamentally from the situation with mammalian clocks. In addition, we present results from comparative studies involving two species of blind cavefish, Astyanax mexicanus and Phreatichthys andruzzii. This work reveals the consequences of evolution in perpetual darkness for the circadian clock and its regulation by light as well as for other mechanisms such as DNA repair, sleep, and metabolism which directly or indirectly are affected by regular exposure to sunlight. Major differences in the cave habitats inhabited by these two cavefish species have a clear impact on shaping the molecular and cellular adaptations to life in complete darkness.

Ultrastructural Morphology of the Antenna and Maxillary Palp of Sarcophaga tibialis (Diptera: Sarcophagidae).

A scanning electron microscopy investigation of the antenna and maxillary palp of the adult of Sarcophaga tibialis Macquart (Diptera: Sarcophagidae), a species of medical, veterinary, and forensic relevance, is presented for the first time. Adults of both sexes used in this study were obtained from larvae collected in a case of traumatic myiasis in a domestic cat in northern Italy. The antenna of S. tibialis is that typical of cyclorrhaphan Diptera, consisting of three segments: the scape, the pedicel, and the postpedicel, bearing the arista. The scape is covered by microtrichia and has a row of long chaetic sensilla. The pedicel is also covered by microtrichia and has three types of chaetic sensilla and a cluster of setiferous plaques. Trichoid, styloconic, clavate, and basiconic sensilla are distributed among the microtrichia on the postpedicel. Invaginated basiconic-like sensilla and olfactory pits are also present, the latter ones more numerous in the female. Our results are compared with those obtained for other calyptrate flies, mainly in the family Sarcophagidae. The data obtained may represent a basis for electrophysiological studies on the sensorial activity of the species related to the search for food sources, mates, and suitable larviposition sites, and for comparative morphological studies with other Diptera.

The arrestin superfamily: cone arrestins are a fourth family.

Arrestins constitute a superfamily of regulatory proteins that down-regulate phosphorylated G-protein membrane receptors, including rod and cone photoreceptors and adrenergic receptors. The potential role of arrestin in color visual processes led us to identify a cDNA encoding a cone-like arrestin in Xenopus laevis, the principle amphibian biological model system. Alignment of 18 deduced amino acid sequences of all known arrestins from both invertebrate and vertebrate species reveals five arrestin families. Further analysis identifies 7 variable and 4 conservative arrestin structural motifs that may identify potential functional domains. The adaptive evolutionary relationship of Xenopus cone arrestin to the arrestin gene tree suggests high intrafamily homology and early gene duplication events.

Tourette's syndrome in a special education population: a pilot study involving a single school district.

To determine whether children requiring special education represent a high-risk group for identifying Tourette's syndrome (TS), we performed direct examinations for the presence of tics in 35 special education and 35 regular classroom students from a single school district. Of the special education students, nine (26%) had definite or probable tics as compared with only two (6%) of the regular classroom students. About one-third of the students with tics currently meet diagnostic criteria for TS and probably more will do so in the future. About one-half of the subjects with tics have evidence of obsessive-compulsive behavior (OCB) or an attention-deficit hyperactivity disorder (ADHD). For three randomly selected students with definite tics, direct examinations of first-degree relatives revealed the presence of tics in all families. Subjects to the limitations of this pilot study, we conclude that TS and related tic disorders are commonly associated with the need for special education in this single school district. TS might also be an important contributor to school problems in the childhood population at large and may be a highly prevalent condition. In addition, we conclude that childhood tics are associated with OCB and ADHD, are genetically determined, and are part of the TS clinical spectrum.

Treatment of RAEB-t with intensive chemotherapy and GM-CSF.

A 55-yr old woman with refractory anaemia with excess of blasts in transformation developed prolonged bone marrow hypoplasia following two courses of mitozantrone and cytosine arabinoside. The administration of granulocyte-monocyte colony stimulating factor after two months of pancytopenia led to recovery of normal bone-marrow function, without any morphological evidence of myelodysplasia, which has persisted until the last blood count (6 months +).

Rhythmic transcription: the molecular basis of oscillatory melatonin synthesis.

Pulsatile hormone synthesis and secretion are characteristic features of various oscillatory biological systems. Circadian rhythms are critical in the regulation of most physiological functions, and much interest has been centred on the understanding of the molecular mechanisms governing them. Adaptation to a changing environment is an essential feature of physiological regulation. The day-night rhythm is translated into hormonal oscillations governing the metabolism of all living organisms. In mammals the pineal gland is responsible for the circadian synthesis of the hormone melatonin in response to signals originating from the endogenous clock located in the hypothalamic suprachiasmatic nucleus (SCN). The molecular mechanisms involved in rhythmic synthesis of melatonin involve the CREM gene, which encodes transcription factors responsive to activation of the cAMP signalling pathway. The CREM product, ICER, is rhythmically expressed and participates in a transcriptional autoregulatory loop which also controls the amplitude of oscillations of serotonin N-acetyl transferase, the rate-limiting enzyme of melatonin synthesis. Thus, a transcription factor modulates the oscillatory levels of a hormone.

Circadian rhythm generation, expression and entrainment in a molluscan model system.

The Bulla ocular pacemaker provides remarkable opportunities for cellular study of circadian pacemaker systems. The demonstration of circadian oscillations within individual neurons maintained in culture provides us with a first occasion to study the biophysical and biochemical properties of bona fide neuronal circadian pacemakers. The ocular clock is robust and shares formal similarity with other circadian systems. The development of molecular techniques that can be applied to single neurons should allow research on the Bulla retina to continue to progress towards a molecular analysis of circadian timekeeping.

Flies and fish: birds of a feather.

The identification of specific clock-containing structures has been a major endeavour of the circadian field for many years. This has lead to the identification of many key components of the circadian system, including the suprachiasmatic nucleus in mammals, and the eyes and pineal glands in lower vertebrates. However, the idea that these structures represent the only clocks in animals has been challenged by the discovery of peripheral pacemakers in most organs and tissues, and even a number of cell lines. In Drosophila, and vertebrates such as the zebrafish, these peripheral clocks appear to be highly autonomous, being set directly by the environmental light/dark cycle. However, a hierarchy of clocks may still exist in mammals. In this review, we examine some of the current views regarding peripheral clocks, their organization and how they are entrained.

A simple method for the separation and assay of non-ionic detergents.

A simple one-dimensional thin-layer chromatographic separation method is described that permits separation and estimation of the non-ionic detergents Lubrol WX, Triton X-100 and Brij 58 in the presence of the common natural lipids.

Relative effects of different surfactants on intestinal absorption and the release of proteins and phospholipids from the tissue.

The actions of anionic, cationic and non-ionic surfactants on the absorptive capability of rat jejunal tissue in vivo were compared with their effects on the amounts of protein and phospholipid released from the mucosal surface under the same conditions. Release of a comparatively small amount of protein was accompanied by large increases in the absorption rates of both L-valine and salicylate, whereas much larger quantities of phospholipid were released before any increase in absorption were observed. Much of the released material appeared to be derived from mucus which was partly degraded after exposure to the higher concentrations of surfactants. The liberation of cholesterol by high concentrations of anionic surfactants suggested that some disruption of the mucosal membrane occurred under those conditions. The relative potency of the surfactants in stimulating both absorption of the solutes and the release of polypeptides and lipids followed the order: anionic greater than non-ionic greater than cationic. The possible pharmaceutical relevance of these findings is discussed.

Luteal function in unilaterally hysterectomized ewes treated with gonadotropin-releasing hormone.

An experiment was conducted to examine effects of GnRH administered to ewes during metestrus on subsequent luteal and uterine functional interrelationships. Treatments consisted of GnRH (0 or 100 micrograms/d) and uterine status (intact or unilaterally hysterectomized [UHYST]). On d 12 of an estrous cycle, all ewes were unilaterally ovariectomized and one-half of these ewes were subjected to contralateral UHYST. Corpora lutea in the remaining ovary were enucleated. One-half of the intact and UHYST ewes were injected i.v. with 2 mL of GnRH on d 2 and 3 after subsequent estrus, and the remaining ewes were injected similarly with 2 mL of saline. Jugular blood samples were collected at 15-min intervals after GnRH or saline injection and analyzed for serum LH. Caudal vena caval and(or) jugular blood were collected daily from d 5 to 10 and on d 12 and 14 of the cycle and analyzed for progesterone, oxytocin, and prostaglandin F2 alpha (PGF2 alpha). Injection of ewes with GnRH increased serum concentrations of LH within 60 min compared with those of saline-treated ewes (P = .01). Treatment with GnRH did not alter concentrations of oxytocin in intact or UHYST ewes (P > .10) but on d 12 and 14 mean jugular concentrations of oxytocin were greater (P = .01) in intact than in UHYST ewes. Vena cava plasma concentrations of PGF2 alpha did not differ (P > .10) among treatments. Treatment with GnRH did not affect (P > .10) serum concentrations of progesterone, but concentrations of this steroid over the sampling period tended to be greater (P = .09) in UHYST ewes than in intact ewes. In conclusion, treatment of intact and UHYST ewes with GnRH failed to alter systemic concentrations of oxytocin, PGF2 alpha, and progesterone; however, the concentrations of oxytocin were affected by unilateral hysterectomy.

Ultrafast dynamics. Attosecond band-gap dynamics in silicon.

Electron transfer from valence to conduction band states in semiconductors is the basis of modern electronics. Here, attosecond extreme ultraviolet (XUV) spectroscopy is used to resolve this process in silicon in real time. Electrons injected into the conduction band by few-cycle laser pulses alter the silicon XUV absorption spectrum in sharp steps synchronized with the laser electric field oscillations. The observed ~450-attosecond step rise time provides an upper limit for the carrier-induced band-gap reduction and the electron-electron scattering time in the conduction band. This electronic response is separated from the subsequent band-gap modifications due to lattice motion, which occurs on a time scale of 60 ± 10 femtoseconds, characteristic of the fastest optical phonon. Quantum dynamical simulations interpret the carrier injection step as light-field-induced electron tunneling.

Zebrafish circadian clocks: cells that see light.

In the classical view of circadian clock organization, the daily rhythms of most organisms were thought to be regulated by a central, 'master' pacemaker, usually located within neural structures of the animal. However, with the results of experiments performed in zebrafish, mammalian cell lines and, more recently, mammalian tissues, this view has changed to one where clock organization is now seen as being highly decentralized. It is clear that clocks exist in the peripheral tissues of animals as diverse as Drosophila, zebrafish and mammals. In the case of Drosophila and zebrafish, these tissues are also directly light-responsive. This light sensitivity and direct clock entrainability is also true for zebrafish cell lines and early-stage embryos. Using luminescent reporter cell lines containing clock gene promoters driving the expression of luciferase and single-cell imaging techniques, we have been able to show how each cell responds rapidly to a single light pulse by being shifted to a common phase, equivalent to the early day. This direct light sensitivity might be related to the requirement for light in these cells to activate the transcription of genes involved in DNA repair. It is also clear that the circadian clock in zebrafish regulates the timing of the cell cycle, demonstrating the wide impact that this light sensitivity and daily rhythmicity has on the biology of zebrafish.