Advances in alternative DNA delivery techniques

This review describes recent advances in alternative DNA-delivery techniques with particular emphasis on silicon carbide fibers, intact tissue electroporation, electrophoresis and microinjection. The advantages/disadvantages of each method along with a historical overview and theory of practice are discussed.     

Selective foraging on woody plant species by the Eurasian beaver (Castor fiber) in Telemark, Norway

Beavers Castor spp. are generalist herbivores, feeding on the bark, shoots and leaves of woody plants, terrestrial herbs and forbs, ferns and aquatic vegetation. As central-place foragers, beavers move out from water to select and cut trees and vegetation, and then transport it back to their refuge. These terrestrial forays are energetically costly; therefore, beavers should concentrate their foraging activity near the central place and increase the degree of selectivity for specific sizes or species of food with increasing distance from the water. The aim of this study was to test the predictions of the central place and the optimal foraging theories for the food selection of the Eurasian beaver Castor fiber , and show the foraging preferences of the focal species in the boreal conifer forest zone of Europe. Foraging intensity by beavers and the abundance of woody species were surveyed in transects positioned randomly at seven beaver territories. In compliance with the central-place foraging theory, the foraging intensity declined with increasing distance from the river. Beavers fed preferentially on willows ( Salix ), rowan ( Sorbus ) and birches ( Betula ), although alders ( Alnus ) dominated their diet. Size selectivity showed similar patterns to previous North American studies, which were also carried out in habitats with predominantly small saplings. The probability of selection of small saplings dropped as distance increased, which is consistent with the predictions of optimal foraging models that larger prey items are more likely to be favoured with increasing provisioning distance.     

Structural characterization of genes corresponding to cotton fiber mRNA, E6: reduced E6 protein in transgenic plants by antisense gene

Two genes, each corresponding to fiber mRNA E6, were isolated from cotton cultivars Coker 312 (Gossypium hirsutum L.) and Sea Island (G. barbadense L.). E6 is one of the predominant fiber-specific mRNAs present during early fiber development. The distinguishing feature of the nucleotide-derived E6 protein is the presence of a motif where a dimer, Ser-Gly, is repeated several times. Two of the Sea Island genes contained a pentameric motif, Ser-Gly, while one of the Coker genes had one and the other had four motifs each. cDNA clones containing one or five Ser-Gly motifs were also identified. Thus, it appears that the strict conservation of this motif may not be critical to E6 protein function. Sequence characterizations of the genes and cDNAs showed that multiple members of the E6 family are transcribed in fiber and may result in proteins 238 to 246 amino acids long. The 3 ends of the genes and cDNAs showed considerable heterology among them. Transgenic plants containing antisense genes were generated to decipher E6 function. Transgenic cotton with reduced E6 protein levels in the range of 60 to 98% were identified. However, no discernible phenotypic changes in fiber development or properties were apparent. This result leads to the conclusion that E6 is not critical to the normal development or structural integrity of cotton fibers.     

In situ fermentation monitoring with recombinant firefly luciferase

A novel method is described for the on-line determination of viable cell number. It has been tested in fermentations of Escherichia coli. The cells are transfected with the gene for firefly luciferase and fed low levels of luciferin in the medium. The reaction requires ATP, so the nonviable cells cannot produce light. Thus, light production is linear with viable cell density from innoculation through most of exponential growth. The light emitted by these cells is then conducted from the reaction vessel to the light detection equipment by an optical fiber. With the equipment described below, as few as a 10(6) cells/mL, or an OD(600) of 0.004, are easily detectable and concentrations greater than 10(10) cells/mL are well within range. The data are collected by a computer, so adaptation to on-line control applications is straightforward. During lag phase, this method is much more accurate then optical density measurements. At the end of exponential growth, rapid changes in light production mark carbon source depletion and the onset of cell lysis. A simple model accounts for the luciferin used during the fermentation and corrects the light detected to the proper cell density. (c) 1993 John Wiley & Sons, Inc.     

Fine structure of the zoospore ofUlothrix belkae with emphasis on the flagellar apparatus

Summary The anterior end of the zoospore ofUlothrix belkae has been examined in detail and is compared toStigeoclonium and other filamentous green algae. The nature of the symmetry of green algal motile cells is discussed and the term, 180° rotational symmetry, is proposed to describe the type of arrangement of anterior end components seen inU. belkae, including the four basal bodies, rootlets and striated fibers. The four microtubular rootlets are cruciately arranged. A striated microtubule-associated component (SMAC) has a periodicity of 6.4 nm and extends with each 2-membered rootlet posteriorly into the cell. One 5-membered rootlet passes very near the eyespot. Phylogeny in green algal motile cells is discussed.     

Structural Characteristics of the Short-Tail Fibers of T4 Bacteriophage

The characteristics of pure preparations of short-tail fibers of bacteriophage T4 have been studied in the optical and electron microscope. Three main structures were observed: 1) spheres of 8.1 nm diameter; 2) fibers 43 nm long and 3.8 nm thick; and 3) fibers 54 nm long and 3.2 nm thick. Both types of fibers exhibited a regular beaded appearance. The 43-nm fibers were the most abundant structure. During the process of purification of the short-tail fibers, the formation of aggregates was observed each time the material containing the short-tail fibers was dialyzed against saline solutions. These aggregates became increasingly fibrous (as observed in the optical microscope) as the material used was increasingly enriched in short-tail fibers. Finally, most of the aggregates were of the fibrous type when they were formed from a purified preparation of short-tail fibers. In the electron microscope, it was found that the filamentous aggregates were organized in well-defined bundles. The amino acid composition of the highly purified short-tail fibers was also determined. Among the known fibrous proteins, the ones that most resemble the amino acid composition of the short-tail fibers are actin and fibrinogen. These observations are discussed in relation to the T4 short-tail fiber structure and their localization on the hexagonal baseplate of the T4 tail structure.     

2-Deoxyglucose Incorporation in the Cerebellum of Weaver and Nervous Mutant Mice

Abstract: The 2-deoxyglucose autoradiographic method has been used to study activity in cerebellum of the weaver and nervous mutant mice. Patterns of 2-deoxyglucose incorporation into the cerebral hemispheres from weaver and nervous strains did not differ significantly from those of the controls. In the normal cerebellum, 2-deoxyglucose incorporation was maximal in the granular layer, where mossy fibers form synapses with the dendrites of granule cells. In the cerebellum of nervous mice, which lacks Purkinje cells, the incorporation of the 2-deoxyglucose was maximal in the granular layer, but the incorporation into the molecular layer appeared less than in the control. The incorporation into the cerebellum from weaver, which lacks granule cells, was much higher than that of the control, the maximal incorporation being found in the Purkinje cell layer and in cell masses located in the white matter. These data suggest that the heterologous synapses that mossy fibers or climbing fibers form with the cells in the Purkinje cell layer and the cells in the white matter in the weaver cerebellum are functional.     

新疆罗布麻生态类型及其纤维品质研究

新疆塔里木河及叶尔羌河流域是我国能够提供商品精干罗布麻的主要地区。由于野生罗布麻生长高矮不一,形态各异,与其纤维品质的相关性较大。通过40个株号的罗布麻植株形态和纤维长度等的的测定,分析各类型罗布麻的纤维长度和罗布麻植株各部分纤维长度情况。研究结果表明：罗布红麻高杆类型主茎纤维最长,罗布麻放牧类型纤维最短。罗布麻植株各部分纤维长度是主茎上的大于分枝,主茎中部的最长,基部和梢部最短。为野生罗布麻资源开发利用提科学依据。     

Muscle palmitate uptake and binding are saturable and inhibited by antibodies to FABPPM

Studies show that uptake of long-chain fatty acids (LCFA) across the plasma membranes (PM) may occur partly via a carrier-mediated process and that the plasma membrane fatty acid-binding protein (FABP_PM) may be a component of this system. To test the hypothesis that FABP_PM is involved in transsarcolemmal transport of LCFA in muscle, we measured palmitate uptake in giant sarcolemmal vesicles and palmitate binding to PM proteins in rat muscles, (1) in the presence of increasing amounts of unbound palmitate and (2) in the absence or presence of antibody to FABP_PM. Both palmitate uptake and binding were found to be saturable functions of the unbound palmitate concentration with calculated V_max values of 10.5 ± 1.2 pmol/mg protein/15 sec and 45.6 ± 2.9 nmol/mg protein/15 min and K_m values of 12.8 ± 3.8 and 18.4 ± 1.8 nmol/L, respectively. The V_max values for both palmitate uptake and binding were significantly decreased by 75-79% in the presence of a polyclonal antibody to the rat hepatic FABP_PM. Antibody inhibition was found to be dose-dependent and specific to LCFA. Glucose uptake was not affected by the presence of the antibody to FABP_PM. Palmitate uptake and binding were also inhibited in the presence of trypsin and phloretin. These results support the hypothesis that transsarcolemmal LCFA transport occurs in part by a carrier-mediated process and that FABP_PM is a component of this process in muscle.