No abstract

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Articlestructure of the LASV spike complex, which provides fundamental information regarding the SSP, receptor recognition and the stability of this trimeric complex.

Abstract. Pulse-labeling studies of slow axonal trans-

The organization of the cytoskeleton is compared in the large myelinated parasympathetic and somatic motor axons of the avian oculomotor system. Electron microscopic studies demonstrate that neurofilaments are the chief structural elements in these axons, and quantitative analyses of the distribution of neurofilaments in axonal cross-sections found that the average neurofilament packing density is 25% greater in the parasympathetic axons than in the somatic motor axons. In both types of axon the distributions of neurofilaments matched a randomly generated (Poisson) distribution. In axoplasm, a Poisson distribution could arise if the neurofilaments were distributed in the cross-sectional plane by stochastic forces operating randomly and without significant neurofilament-neurofilament interactions. Thus, in these axons, the neurofilaments behave as if they are inert 'molecules' in a dilute solution-subject to non-specific stochastic forces that tend to distribute them at random. We propose that neurofilaments normally are relatively free to move apart from each other and to fill the available space within the axon.

No abstract

In this study we investigate the NADPH-dependent stereoselective reduction of the bicyclic diketone bicyclo[2.2.2]octane-2,6-dione (BCO2,6D) to the chiral ketoalcohol (1R,4S,6S)-6-hydroxybicyclo[2.2.2]octane-2-one (BCO2one6ol). Our aim was to develop a whole cell batch process for reduction of carbonyl substrates with (i) a high cosubstrate yield (formed product/consumed cosubstrate) and (ii) a high conversion rate under anaerobic conditions with Saccharomyces cerevisiae as biocatalyst and glucose as cosubstrate. Five open reading frames (ORFs), YMR226c, YDR368w, YOR120w, YGL157w, and YGL039w, encoding reductases involved in the conversion of BCO2,6D were identified using cell-free extract from strains belonging to the ExClone collection (yeast ORF expression clones; ResGen, Invitrogen Corp., UK). We report the one-step purification and characterization of three major BCO2,6D reductases, YMR226cp, YDR368wp (YPR1p), and YOR120wp (GCY1p). The reductases were overexpressed under a strong constitutive promoter and the impact on cosubstrate yield, conversion time, glucose consumption rate, and reduction rate was investigated when reductases were overexpressed either alone or in combination with low phosphoglucose isomerase activity (encoded by YBR196c). Combining overexpression of BCO2,6D reductase with reduced glycolytic rate (low phosphoglucose isomerase activity) offers a fast whole cell stereoselective bioreduction system useful for facilitated anaerobic batch conversions.

The evolution of nervous systems has included significant changes in the axon tracts of the central nervous system. These evolutionary changes required changes in axonal growth in embryos. During development, many axons reach their targets by following guidance cues that are organized as pathways in the embryonic substrate, and the overall pattern of the major axon tracts in the adult can be traced back to the fundamental pattern of such substrate pathways. Embryological and comparative anatomical studies suggest that most axon tracts, such as the anterior commissure, have evolved by the modified use of preexisting substrate pathways. On the other hand, recent developmental studies suggest that a few entirely new substrate pathways have arisen during evolution; these apparently provided opportunities for the formation of completely new axon tracts. The corpus callosum, which is found only in placental mammals, may be such a truly new axon tract. We propose that the evolution of the corpus callosum is founded on the emergence of a new preaxonal substrate pathway, the "glial sling," which bridges the two halves of the embryonic forebrain only in placental mammals.Increases in the number of central nervous system (CNS) neurons and in the complexity of the synaptic neuropil characterize the vertebrate phylogeny (1, 2). These increases are usually manifest as enlargements of specific CNS areas such as the cerebellum, the tectum, and the cerebrum. Local enlargements can be attributed to focal increases in the dominant class of vertebrate neurons-local circuit neurons-neurons with axons that extend only short distances in the CNS before synapsing (1).Local areas of the CNS are connected by another important class of neurons-projection neurons-which send their axons along a few long stereotyped routes to target areas far from their cell bodies. The white matter of the vertebrate CNS is composed largely of axon tracts of projection neurons, and many of the same major axon tracts can be identified throughout the vertebrates. Although the overall pattern of these major tracts appears to have been conserved during evolution (2-8), there are some significant variations. Frequently, the compactness of particular tracts varies, as in the spinal lemniscal tracts (2, 9-11). In some cases, the particular stereotyped route taken by homologous axons varies-e.g., the stereotyped routes of the corticospinal tracts differ among most primates, ungulates, rodents, and marsupials (12-14). Moreover, a few major vertebrate axon tracts have appeared with no apparent precursors. The most dramatic example is the (dorsal) corpus callosum, which is found only in placental mammals (15,16).The corpus callosum is a large interhemispheric commissure, and most axons of the corpus callosum interconnect homotopic neocortical areas (17)(18)(19)(20)(21)(22). for exceptions to this general rule.) Monotremes and marsupials have no dorsal corpus callosum (2,16,(26)(27)(28). Among the placental mammals, the corpus callosum generally increases as t...