Truck Drivers Sleep-Wake Time Arrangements

Irregular working hours, including night work, change sleep-wake time arrangements which in turn might affect the ability to drive safely. This study aims to compare the effects of an irregular and a fixed day shift system on the sleep-wake cycle of truck drivers. The investigation of sleep-wake cycle was carried-out with 37 truck drivers working on two transportation plants: 24 working on irregular working hours and 13 on fixed day shift. The truck drivers filled out sleep logs and wore actigraphs for 10 consecutive days to identify activity and rest episodes. The group working in irregular hours showed more sleep episodes per 24 h and they were shorter compared to the fixed shift group (p < 0.05). No differences were found between the two transportation plants. These results suggest an the influence of working hours on specific sleep-wake patterns. The polyphasic sleep pattern shown by irregular shift group could be a strategy to cope with sleep deprivation, which may account for their difficulty to resist falling asleep behind the wheel.     

Acute Complexin Knockout Abates Spontaneous and Evoked Transmitter Release

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Forced expression of Phox2 homeodomain transcription factors induces a branchio-visceromotor axonal phenotype

What causes motor neurons to project into the periphery is not well understood. We here show that forced expression of the homeodomain protein Phox2b, shown previously to be necessary and sufficient for branchio-visceromotor neuron development, and of its paralogue Phox2a imposes a branchiomotor-like axonal phenotype in the spinal cord. Many Phox2-transfected neurons, whose axons would normally stay within the confines of the neural tube, now project into the periphery. Once outside the neural tube, a fraction of the ectopic axons join the spinal accessory nerve, a branchiomotor nerve which, as shown here, does not develop in the absence of Phox2b. Explant studies show that the axons of Phox2-transfected neurons need attractive cues to leave the neural tube and that their outgrowth is promoted by tissues, to which branchio-visceromotor fibers normally grow. Hence, Phox2 expression is a key step in determining the peripheral axonal phenotype and thus the decision to stay within the neural tube or to project out of it.     

Cell fate specification and differentiation in the nervous system of Caenorhabditis elegans

Neuronal cell fates are specified by a hierarchy of events mediated by cell-intrinsic determinants and cell-cell interactions. The determination of cell fate can be subdivided into three general steps. First, cell fate is restricted by the cell's position in the animal. For example, neurons are specified along the anterior-posterior body axis through the action of the Hox genes lin-39, mab-5, and egl-5. Second, a decision is made to generate a particular cell type, such as the progenitor of a neurogenic lineage as opposed to that of an epidermal lineage. Among the genes that influence this decision is the proneural gene lin-32. Third, characteristics of a particular cell type are specified. For example, in a neurogenic lineage, a decision may be made to generate a specific neuron type such as a sensory or motor neuron. Genes that affect neuronal fate can act in different ways to influence the development of different types of neurons. © 1996 Wiley-Liss, Inc.     

Screen for mutations affecting development of zebrafish neural crest

The neural crest provides a useful model to learn how cell fate diversification is regulated during vertebrate development. Our approach is to isolate zebrafish mutations in which the development of neural crest derivatives is disrupted, in order to learn about the underlying genetic mechanisms. We describe a screen in which parthenogenetic diploid embryos are examined both for visible phenotypes and for cellular defects in neural crest-derived sensory neurons recognized immunohistochemically. We present preliminary results from this screen and briefly describe a few representative mutations. We also discuss the general utility of our strategy and comment on the future directions of this approach. © 1996 Wiley-Liss, Inc.     

Lobula plate and ocellar interneurons converge onto a cluster of descending neurons leading to neck and leg motor neuropil in Calliphora erythrocephala

Summary In the fly, Calliphora erythrocephala, a cluster of three Y-shaped descending neurons (DNOVS 1–3) receives ocellar interneuron and vertical cell (VS4–9) terminals. Synaptic connections to one of them (DNOVS 1) are described. In addition, three types of small lobula plate vertical cell (sVS) and one type of contralateral horizontal neuron (Hc) terminate at DNOVS 1, as do two forms of ascending neurons derived from thoracic ganglia. A contralateral neuron, with terminals in the opposite lobula plate, arises at the DNOVS cluster and is thought to provide heterolateral interaction between the VS4–9 output of one side to the VS4–9 dendrites of the other. DNOVS 2 and 3 extend through pro-, meso-, and metathoracic ganglia, branching ipsilaterally within their tract and into the inner margin of leg motor neuropil of each ganglion. DNOVS 1 terminates as a stubby ending in the dorsal prothoracic ganglion onto the main dendritic trunks of neck muscle motor neurons. Convergence of VS and ocellar interneurons to DNOVS 1 comprises a second pathway from the visual system to the neck motor, the other being carried by motor neurons arising in the brain. Their significance for saccadic head movement and the stabilization of the retinal image is discussed.