Influence of the venom delivery system on intraoral prey transport in snakes

We compared intraoral prey transport in venomous snake species from four families (two atractaspidids, nine elapids, three colubrids, 44 viperids) with that in eight non-venomous colubrid species, most feeding on similar mammalian prey. The morphology of the venom delivery system suggests that intraoral prey transport performance should be slightly decreased in atractaspidids, unmodified in most elapids and venomous colubrids, and increased or unmodified in vipers, as compared to that in non-venomous colubrid snakes. Our measurements of relative intraoral prey transport performance show that differences among families do not match expectations based on morphology or past studies. Decreased performance in Atractaspis results from reduction and loss of teeth on the medial palatal elements and dentaries, but affects only early phases of ingestion. Although joint and bone features of elapids and colubrids are similar, intraoral prey transport performance is significantly lower in elapids than in colubrids. Predicted enhancement of intraoral prey transport performance in vipers as compared to colubrids was not borne out by measurements, presumably because palatopterygoid movement during intraoral prey transport is reduced in many viper species to limit fang erection. Absence of significant performance differences between colubrids and viperids might suggest that evolution of the viperid venom delivery system was subject to little selection pressure from intraoral prey transport. Another possibility is that there are trade-offs between intraoral prey transport and strike performance in vipers related to relative skull mass and jaw fragility. Immobilizing prey prior to intraoral transport places less demand on transport performance in vipers. In this model, the conservative kinesis and greater robustness of the colubrid palate has greater potential for transporting live prey with less risk of injury.     

Transport of galectin-3 between the nucleus and cytoplasm. II. Identification of the signal for nuclear export

Galectin-3, a factor involved in the splicing of pre-mRNA, shuttles between the nucleus and the cytoplasm. Previous studies have shown that incubation of fibroblasts with leptomycin B resulted in the accumulation of galectin-3 in the nucleus, suggesting that the export of galectin-3 from the nucleus may be mediated by the CRM1 receptor. A candidate nuclear export signal fitting the consensus sequence recognized by CRM1 can be found between residues 240 and 255 of the murine galectin-3 sequence. This sequence was engineered into the pRev(1.4) reporter system, in which candidate sequences can be tested for nuclear export activity in terms of counteracting the nuclear localization signal present in the Rev(1.4) protein. Rev(1.4)-galectin-3(240-255) exhibited nuclear export activity that was sensitive to inhibition by leptomycin B. Site-directed mutagenesis of Leu247 and Ile249 in the galectin-3 nuclear export signal decreased nuclear export activity, consistent with the notion that these two positions correspond to the critical residues identified in the nuclear export signal of the cAMP-dependent protein kinase inhibitor. The nuclear export signal activity was also analyzed in the context of a full-length galectin-3 fusion protein; galectin-3(1-263; L247A) showed more nuclear localization than wild-type, implicating Leu247 as critical to the function of the nuclear export signal. These results indicate that residues 240-255 of the galectin-3 polypeptide contain a leucine-rich nuclear export signal that overlaps with the region (residues 252-258) identified as important for nuclear localization.     

Colocalization of α-lactalbumin and a major casein in secretory vesicles of rat mammary epithelial cells

Summary Whether both casein and noncasein (serum or whey) proteins of milk are contained within the same secretory vesicles of milk secreting mammary epithelial cells was explored. Antibodies to a major casein and to -lactalbumin of rat milk were localized in thin sections with colloidal gold-conjugated second antibodies. Antibodies to the casein component bound to an antigen present within lumina of Golgi apparatus cisternae and within secretory vesicles. This antigen was also recognized in structures within secretory vesicles and within alveolar lumina which were ultrastructurally identified as casein micelles. Antigens recognized by antibodies to -lactalbumin also were present in Golgi apparatus cisternae and within secretory vesicles. Both anti-casein and anti--lactalbumin antibodies recognized antigens within the same secretory vesicles. These observations show that one major noncasein protein of rat's milk is present in casein-containing secretory vesicles.     

Chronic restraint stress disturbs meiotic resumption through APC/C-mediated cyclin B1 excessive degradation in mouse oocytes

Psychological stress, which exerts detrimental effects on human reproduction, may compromise the meiotic competence of oocytes. Meiotic resumption, germinal vesicle breakdown (GVBD), is the first milestone to confer meiotic competence to oocytes. In the practice of assisted reproductive technology (ART), the timing for GVBD is associated with the rates of cleavage and blastocyst formation. However, whether chronic stress compromises oocyte competence by influencing GVBD and the underlying mechanisms are unclear. In the present study, a chronic restraint stress (CRS) mouse model was used to investigate the effects of stress on oocyte meiotic resumption, as well as the mechanisms. Following a 4-week chronic restraint stress in female mice, the percentage of abnormal bipolar spindles increased and indicated compromised oocyte competence in the CRS group. Furthermore, we identified a decreased percentage of GVBD and prolonged time of GVBD in the CRS mouse oocytes compared with the control group. CRS simultaneously reduced the expression of cyclin B1 (CCNB1), which represents a regulatory subunit of M-phase/mature promoting factor (MPF). However, MG132, an inhibitor of anaphase-promoting complex/cyclosome (APC/C), could rescue the prolonged time of GVBD and increase the expression level of CCNB1 of oocytes from the CRS mice. Collectively, our results demonstrated that stress disturbed meiotic resumption through APC/C-mediated CCNB1 degradation, thus providing a novel understanding for stress-related oocyte quality decline; moreover, it may provide a non-invasive approach to select high-quality gametes and novel targets for molecular therapy to treat stress-related female infertility.     

Toc64/OEP64 is not essential for the efficient import of proteins into chloroplasts in Arabidopsis thaliana

Toc64/OEP64 was identified biochemically in pea as a putative component of the chloroplast protein import apparatus. In Arabidopsis, three paralogous genes (atTOC64-III, atTOC64-V and atTOC64-I) encode Toc64-related proteins, and these have been reported to localize in chloroplasts, mitochondria and the cytosol, respectively. To assess the role of the atToc64-III protein in chloroplast protein import in an in vivo context, we identified and characterized Arabidopsis knockout mutants. The absence of detectable defects in toc64-III single mutants raised the possibility of redundancy, and prompted us to also identify toc64-V and toc64-I mutants, cross them to toc64-III, and generate double- and triple-mutant combinations. The toc64 mutants were analysed carefully with respect to a variety of criteria, including chlorophyll accumulation, photosynthetic performance, organellar ultrastructure and chloroplast protein accumulation. In each case, the mutant plants were indistinguishable from wild type. Furthermore, the efficiency of chloroplast protein import was not affected by the toc64 mutations, even when a putative substrate of the atToc64-III protein (wheatgerm-translated precursor of the 33 kDa subunit of the oxygen-evolving complex, OE33) was examined. Moreover, under various stress conditions (high light, osmotic stress and cold), the toc64 triple-mutant plants were not significantly different from wild type. These results demonstrate that Toc64/OEP64 is not essential for the efficient import of proteins into chloroplasts in Arabidopsis, and draw into question the functional significance of this component.     

ULTRASTRUCTURE AND TAXONOMIC POSITION OF THE RARE VOLVOCALEAN ALGA,CHLORCORONA BOHEMICA1

Chlorcorona bohemica (Fott) Fott was previously of uncertain taxonomic affinities. The cell to cell connections, which are one of the chief features of the colony, are composed of wall extensions from adjacent cells. The outgrowths are connected by a fine fibrous component extending from wall to wall. The structure of the wall itself and the cell to cell connections, are similar to those of Pyrobotrys, although the connections in the latter are not as elongated. In addition, the flagellar apparatus of Chlorocorona is very similar to the flagellar apparatus of Pyrobotrys, and unlike that in other Chlorophyceae examined. These features suggest that Chlorcorona is closely related to Pyrobotrys and should be referred to the family Spondylomoraceae.     

中国蒿属植物比较形态和解剖学研究——(Ⅰ)叶表皮结构

本文通过光学显微镜和扫描电镜,观察国产菊科蒿属2亚属7组30种代表植物成熟叶片的表皮细胞、气孔器、表皮毛的特征和气孔形状、气孔外拱盖及拱盖内缘、角质膜和蜡质纹饰。其中表皮细胞多角(边)形,大小不等,垂周壁平直、弓形,或者表皮细胞形状不规则,大小不等,垂周壁波浪状或波纹状。下表皮均有气孔器,上表皮有或无气孔器,气孔器类型有无规则型。无规则四细胞型、不等细胞型、十字型、横列型和平列型。大多数种类具多细胞单列毛。多细胞双列毛和腺毛仅发现在腺毛蒿组。这些微形态特征在组间存在着某些差异,具有一定的分类学和生态学意义。     

IMMUNOLOCALIZATION OF CENTRIN IN OXYRRHIS MARINA (DINOPHYCEAE)1

A new polyclonal antibody was raised against centrin isolated from the flagellate green alga Spermatozopsis similis (Chlorophyta; anti-SSC). It stains by immunofluorescence and immunoelectron microscopy well-known reference systems for centrin like the nucleus–basal body connectors in Chlamydomonas reinhardtii (Chlorophyta) and the system II fibers (rhizoplasts) of Scherffelia dubia (Chlorophyta). In addition, it recognizes in immunoblots a single 20-kDa protein in isolated cytoskeletons of Spermatozopsis similis and Tetraselmis striata (Chlorophyta) as well as purified centrin isolated from Tetraselmis striata. Using this antibody, centrin was localized in whole cells and isolated cytoskeletons of Oxyrrhis marina Dujardin (Dinophyceae) by immunofluorescence and immunogold electron microscopy. In the flagellar apparatus of O. marina, five different structures were antigenic. Four short fibers (connectives 1–4) link the basal bodies to the four major fibrous flagellar roots, which do not cross-react with anti-centrin. The most prominent of the labeled structures (connective 5), a crescent-shaped fiber, extends from the flagellar canal of the transverse flagellum along the base of the tentacle to the flagellar canal of the longitudinal flagellum, interconnecting the distal parts of the microtubular roots/bands in the basal apparatus. For most of its length, it underlies and is connected to a transversely oriented subamphiesmal microtubular band. In immunoblot analyses, anti-SSC recognizes only a single 20-kDa protein in cytoskeletons of O. marina. Functional and phylogenetic aspects of centrin-containing structures in dinoflagellates are discussed.     

An automated climbing apparatus to measure chemotherapy-induced neurotoxicity in Drosophila melanogaster

We have developed a novel model system in Drosophila melanogaster to study chemotherapy-induced neurotoxicity in adult flies. Neurological deficits were measured using a manual geotactic climbing assay. The manual assay is commonly used; however, it is laborious, time-consuming, subject to human error and limited to observing one sample at a time. We have designed and built a new automated fly-counting apparatus that uses a “video capture-particle counting technology” to automatically measure 10 samples at a time, with 20 flies per sample. Climbing behavior was assessed manually, as in our previous studies, and with the automated apparatus within the same experiment yielding statistically similar results. Both climbing endpoints as well as the climbing rate can be measured in the apparatus, giving the assay more versatility than the manual assay. Automation of our climbing assay reduces variability, increases productivity and enables high throughput drug screens for neurotoxicity.