Multiple forms of tubulin in the cytoskeletal and flagellar microtubules of polytomella

The alga polytomella contains several organelles composed of microtubules, including four flagella and hundreds of cytoskeletal microtubules. Brown and co-workers have shown (1976. J. Cell Biol. 69:6-125; 1978, Exp. Cell Res. 117: 313-324) that the flagella could be removed and the cytoskeletans dissociated, and that both structures could partially regenerate in the absence of protein synthesis. Because of this, and because both the flagella and the cytoskeletons can be isolated intact, this organism is particularly suitable for studying tubulin heterogeneity and the incorporation of specific tubulins into different microtubule-containing organelles in the same cell. In order to define the different species of tubulin in polytonella cytoplasm, a (35)S- labeled cytoplasmic fraction was subjected to two cycles of assembly and disassembly in the presence of unlabeled brain tubulin. Comparison of the labeled polytomella cytoplasmic tubulin obtained by this procedure with the tubulin of isolated polytomella flagella by two-dimensional gel electrophoresis showed that, whereas the β-tubulin from both cytoplasmic and flagellar tubulin samples comigrated, the two α-tubulins had distinctly different isoelectic points. As a second method of isolating tubulin from the cytoplasm, cells were gently lysed with detergent and intact cytoskeletons obtained. When these cytoskeletons were exposed to cold temperature, the proteins that were released were found to be highly enriched in tubulin; this tubulin, by itself, could be assembled into microtubules in vitro. The predominant α-tubulin of this in vitro- assembled cytoskeletal tubulin corresponded to the major cytoplasmic α-tubulin obtained by coassembly of labeled polytomella cytoplasmic extract with brain tubulin and was quite distinct from the α-tubulin of purified flagella. These results clearly show that two different microtubule-containing organelles from the same cell are composed of distinct tubulins.     

Effect of oxygen tension on human peripheral blood leukocytes: lysosomal enzyme release and metabolic responses during phagocytosis

We found that nonlethal lysosomal enzyme release from human peripheral blood leukocytes during phagocytosis of opsonized zymosan in vitro was modified by the oxygen tension under which the cells were incubated; with decreasing Po(2), zymosan-induced release of lysosomal enzymes was potentiated. The effect on enzyme release could not be attributed secondarily to an effect on phagocytosis, because, as others have reported, Po(2) had little effect on that response. Metabolic responses that accompany phagocytosis were also modified by oxygen tension. Stimulation of oxidation by way of the pentose cycle was further enhanced by increasing Po(2). Conversely, anaerobic glycolysis was promoted by decreasing oxygen tension. ATP levels fell as a function of time and concentration of phagocytic stimulus, mirroring lysosomal enzyme release as modified by Po(2). Cyclic AMP levels fell during phagocytosis and lysosomal enzyme release, a change that could act to facilitate lysosomal enzyme release. However, the fall in nucleotide level was greatest with highest Po(2) (i.e., when lysosomal enzyme release was least). The inverse relationship between oxidative metabolism and enzyme release suggested that a product of oxidative metabolism might adversely influence enzyme release. Sulfhydryl antioxidants (Cysteine, glutathione) and scavengers of oxygen-derived reactants (superoxide dismutase, catalase, benzoate, hypoxanthine, xanthine, histidine, azide) all potentiated zymosan- stimulated enzyme release. These findings are consistent with the interpretation that one or more factors (e.g., superoxide anion, hydrogen peroxide, hydroxyl radical, singlet oxygen), generated in association with the burst of oxidative metabolism which accompanies phagocytosis, acts to inhibit lysosomal enzyme release.     

Arvicola terrestris an intermediate host of Echinococcus multilocularis in France: Epidemiological consequences

Houin R., Deniau M., Liance M. and Puel F. 1981. Arvicola terrestris, an intermediate host of Echinococcus multilocularis in France: epidemiological consequences. International Journal for Parasitology12: 593–600. Hydatid cysts characteristic of E. multilocularis were found in 5 out of 2010 A. terristris trapped in France in 1980. A comparison of the distribution of human cases and rodents led to the conclusion that A. terrestris is probably the reservoir of the parasite. Another argument in favour of the epidemiological importance of this vole is that the parasite grows slowly in this host which has a relatively long life. Moreover, no other rodents were found in France naturally infected by larval E. multilocularis. As populations of A. terrestris undergo important cyclical fluctuations, high transmission periods must occur. During the periods of peak population, prophylactic measures should be taken to protect the human population.     

红背山麻杆叶的化学成分研究(Ⅱ)——黄酮和苯乙醇苷类化合物

采用80％丙酮提取物的水萃取部位,利用凝胶、MCI、反相碳18、及 Toyopearl Butyl-650C 柱色谱进行分离纯化得到7个黄酮和3个苯乙醇苷类化合物。根据化合物的波谱数据分析鉴定为槲皮素(1)、槲皮苷(2)、异懈皮苷(3)、芦丁(4)、异牡荆素(5)、牡荆素(6)、木犀草素-7-O-α-L-鼠李糖(1→6)-β-D-葡萄糖苷(7)、2-phenethylβ-D-glucoside(8)、icariside D1(9)、2-苯乙基-D-芸香甙(10)。其中化合物1-3、5-6、8-10为首次从本属植物中分离得到。     

3D kinematic and dynamic analysis of the front crawl tumble turn in elite male swimmers

The aim of this study was to identify kinematic and dynamic variables related to the best tumble turn times (3mRTT, the turn time from 3-m in to 3-m out, independent variable) in ten elite male swimmers using a three-dimensional (3D) underwater analysis protocol and the Lasso (least absolute shrinkage and selection operator) as statistical method. For each swimmer, the best-time turn was analyzed with five stationary and synchronized underwater cameras. The 3D reconstruction was performed using the Direct Linear Transformation algorithm. An underwater piezoelectric 3D force platform completed the set-up to compute dynamic variables. Data were smoothed by the Savitzky-Golay filtering method. Three variables were considered relevant in the best Lasso model (3mRTT=2.58-0.425 RD+0.204 VPe+0.0046 TD): the head-wall distance where rotation starts (RD), the horizontal speed at the force peak (VPe), and the 3D length of the path covered during the turn (TD). Furthermore, bivariate analysis showed that upper body (CUBei) and lower limb extension indexes at first contact (CLLei) were also linked to the turn time (r=-0.65 and p<0.05 for both variables). Thus the best turn times were associated with a long RD, slower VPe and reduced TD. By an early transverse rotation, male elite swimmers reach the wall with a slightly flexed posture that results in fast extension. These swimmers opt for a movement that is oriented forward and they focus on reducing the distance covered.