Isolation of motile spermatozoa by density gradient centrifugation in Percoll®

A procedure using centrifugation in density gradients composed of Percoll was developed for isolation of spermatozoa from mammalian semen. To evaluate the technique, rabbit, human, or bovine semen was layered over continuous Percoll gradients ranging in density from 1.02 to 1.13 gm/ml and centrifuged at 1,500g for 45 min. After centrifugation, the seminal plasma remained above the gradient, whereas the spermatozoa and seminal particles were distributed within the gradient according to their buoyant densities. Unlike most washing techniques, no sperm pellet was formed; instead, the spermatozoa were concentrated into a compact band above the most dense layer of Percoll. The spermatozoa recovered from the gradient were easily resuspended by gentle techniques. Thus, the mechanical stress to the spermatozoa was minimized. Osmotic stress to the spermatozoa was also negligible as the Percoll gradients were isotonic throughout. Spermatozoa obtained by this technique possessed motility equivalent to that of spermatozoa in the unfractionated semen. Sperm suspensions recovered from the gradients contained less than 5% of the nonspermatozoal particles present in the original samples of unfractionated semen. Soluble seminal components were also efficiently removed from the spermatozoa. Thirty billion bovine spermatozoa could be fractionated on a single gradient without loss of effectiveness. Recovery of spermatozoa from these preparative separations averaged 80%. These results demonstrated that Percoll was a superior medium for efficient density gradient isolation of motile spermatozoa free of contamination by other seminal constituents.     

Degradation of transgene-coded and endogenous proteins in the muscles of Caenorhabditis elegans

To develop reporter systems to study the regulation of protein degradation in innervated muscle, we have used strains of the nematode Caenorhabditis elegans containing transgenes that fuse lacZ or green fluorescent protein (GFP) coding regions to muscle-specific promoter/enhancer regions, such that the fusion proteins are expressed exclusively in body-wall and vulval muscle cells. The starvation-induced degradation of the beta-galactosidase reporter protein is quantitatively similar to that of two endogenous muscle proteins, arginine kinase and adenylate kinase. A soluble GFP in the muscle cytosol is degraded during starvation, but when GFP is fused to a full-length myosin heavy chain and incorporated into myofibrils, it is resistant to starvation-induced degradation. This suggests that under some conditions soluble muscle proteins may be extensively catabolized in preference to the proteins of the contractile fibers.     

Roles of actin filaments in cytoplasmic streaming and organization of transvacuolar strands in root hair cells ofHydrocharis

Summary Effects of cytochalasin B and mycalolide-B on cytoplasmic streaming, organizations of actin filaments and the transvacuolar strand were studied in root hair cells ofHydrocharis, which shows reverse fountain streaming. Both toxins inhibited cytoplasmic streaming and destroyed the organizations of actin filaments and transvacuolar strands. However, we found a great difference between these toxins with respect to reversibility. The effects of cytochalasin B were reversible but not those of mycalolide B. The present results suggest that actin filaments work as a track of cytoplasmic streaming and as a cytoskeleton to maintain the transvacuolar strand. The usefulness of root hair cells ofHydrocharis in studying the dynamic organization of actin filaments of plant is discussed.Abbreviations CB cytochalasin B - DMSO dimethylsulfoxide - ML-B mycalolide B     

Structure and function of the amphibian follicular epithelium during ovulation

Summary Low concentrations of cytochalasin B (CCB) are known to inhibit ovulation in the frog, Hyla regilla. Examination of amphibian thecal cell ultrastructure reveals filaments (average diameter 71 Å) arranged in bundles parallel to the surface of the oocyte. These filaments are often associated with hemidesmosome-like plaques on the basal plasmalemma. While individual filaments appear unaltered morphologically by CCB (1–5 g/ml), their organization into bundles, apparent relationship to the hemidesmosomes, and the highly contorted configuration of the thecal cells after oocyte expulsion, suggest that a nonmuscular contractile system residing within the follicle plays a fundamental role in ovulation.Our data suggest that the flattened epithelioid thecal cells shorten all axes that run parallel to the oocyte surface via filament bundle contractions, while they remain tightly bound together by macular attachment plaques. These cells thus increase in height to become cuboidal-low columnar in shape; the area covered by the base of each is greatly reduced. As this thecal sac decreases in size, the compression generated by the contractile mechanism forces the oocyte through the enzymatically weakened apex of the follicle and ovulation results.This investigation was supported by grant HD-07194 from the National Institutes of Health. The authors are grateful to Dr. Arthur L. Cohen, Director of the Electron Microscope Center for use of the Center's scanning electron microscope. We are also indebted to Mrs. Gail M. McDole and Mr. James D. Huber for able technical assistance     

Comparison between the recovery rate of three concentration protocols of water samples intended for analysis by Molecular Biology: Membrane filtration,filtration on gauze pad and centrifugation

The presence of microorganisms (bacteria, protozoa, viruses, etc.) in water is a crucial indicator of its quality and safety. The detection of these microorganisms by conventional and classical techniques is widely used in water quality control laboratories; nevertheless these methods have limitations in terms of rapidity and precision of results. The use of Molecular Biology has been a great evolution in the techniques of water analysis. However, the choice of the concentration protocol allowing for the best rate of microorganism recovery in a suspension remains a real challenge. The objective of this experimental study is to compare the recovery rate of three different protocols of water concentration (membrane filtration, filtration on gauze pad and centrifugation) for samples intended for analysis by polymerase chain reaction PCR. Which can then serve as a reference protocol for water quality control laboratories. The experimental results have shown that the membrane filtration protocol yields the best recovery rate and concentration of microorganisms followed by filtration on gauze pad, while the centrifugation protocol (8000g, 10 min, 22 °C) gives the lowest rate of recovery out of the three protocols. The experimental results obtained through this study allows us to contribute to the optimization and standardization of water samples concentration techniques intended for analysis by Molecular Biology.     

骨髓间充质干细胞条件培养液对小鼠卵母细胞的孤雌激活作用

目的研究骨髓间充质干细胞(mesenchymal stem cell,MSC)条件培养液对小鼠MII卵母细胞的孤雌激活作用及胚胎发育能力。方法分离、培养小鼠MSC,获取MSC条件培养液(conditioned medium of MSC,CM)。通过促排技术获取小鼠MII卵母细胞,分别采用CM、7%乙醇、IVF方法激活,体视显微镜下观察原核形成及囊胚形成率。在CM激活后不同时间点,利用α/β-tubulin抗体标记纺锤体,激光共聚焦显微镜下观察有/无细胞松弛素B(CB)存在时纺锤体的运动变化。结果 CM可以激活小鼠MII卵母细胞,最佳刺激时间为40min,激活率达到95.4%,囊胚形成率为62%,与7%乙醇组比较无显著差异,但明显低于IVF组(95.4%vs.100%;62%vs.88%,P0.01)。CB可以抑制纺锤体的旋转,阻止第二极体的排出,促进二倍体孤雌胚形成,提高囊胚形成率(62%vs.9%,P0.01)。结论 CM能有效激活小鼠MII卵母细胞并促进孤雌发育。     

Redistribution of motor proteins by Cytochalasin J treatment

In this study we extend our analysis of the effect of Cytochalasin J (CJ) on mitotic and interphase cells by the use of immunocytochemical techniques to localize antigens to anti-beta-tubulin, anti-dynein heavy chain (HC), anti-dynein intermediate chain (IC), and anti-kinesin antibodies following CJ treatment. Anti-dynein IC and HC staining of CJ treated cells showed a significant reduction in anti-dynein staining in the nuclear region of interphase cells. Monolayer cultures of PtK(1)cells treated with 10 microg/ml CJ for 10 min showed a significant reduction in pixel luminosity of fluorescence staining using anti-dynein IC and HC antibodies (P<0.05). Cytochalasin J treatment reorganized anti-dynein staining from a cytoplasmic punctate staining with greatest intensity in the perinuclear region, to a more uniform staining throughout the cytoplasm.     

A mechanism for accelerated degradation of intracellular proteins after limited damage by free radicals

I propose that limited free radical attack upon proteins, occurring continuously in cells, creates new N-termini (notably aspartate and glutamate) which render the proteins more susceptible to proteolysis by the ubiquitin conjugation system. I suggest that these reactions are a significant part of the previously described ‘N-end’ and ‘PEST’ rules, which indicate amino acid termini or sequences which tend to dictate short protein half-lives. I also argue that the N-end rule may apply to sequestered intracellular sites, such as mitochondria, these also being sites of radical generation.     

Inhibition of glycoconjugate secretion by colchicine and cytochalasin B

Summary The effects have been analyzed of cytochalasin B and colchicine on the secretion of glycoconjugates by human bronchial expiants labeled in vitro with radioactive glucosamine. Both cytochalasin B and colchicine had no effect on baseline ¹⁴C-labeled glycoconjugate release but caused a dose-dependent (10^–7–10^–4 M) inhibition of ¹⁴C-glycoconjugate release and discharge of labeled macromolecules from mucous and serous cells induced by 5 · 10^–5 M methacholine.Quantitative autoradiographic analyses showed that neither cytochalasin B nor colchicine inhibited ³H-threonine or ³H-glucosamine incorporation into mucous and serous cells of the submucosal glands or goblet cells of the airway epithelium. Colchicine (10^–5 M) but not cytochalasin B significantly reduced the rate at which labeled macromolecules were transported through mucous, serous and goblet cells but this effect was not observed until 4 h after the addition of colchicine. Neither cytochalasin B nor colchicine affected the basal rate of labeled-macromolecule discharge from mucous, serous or goblet cells. At a concentration of 10^–5 M, both agents completely inhibited the increase in labeled-macromolecule discharge induced in mucous and serous cells by methacholine.Our results suggest that in the submucosal gland of human airways microtubules and microfilaments may be important in secretagogue-induced but not in baseline cellular glycoconjugate discharge, implying that the mechanisms of the two processes differ significantly. Furthermore, a role for microtubules is suggested in the transport of secretory granules through mucous, serous and goblet cells.Supported by National Institutes of Health Research Grant 5R01HL22444. The authors gratefully acknowledge the technical assistance of Mr. Tudor Williams, Mr. Eduardo Quintanilla and Ms. Maureen Hayes     

Modulation of passive permeability by external ATP and cytoskeleton-attacking agents in cultured mammalian cells

External ATP causes a passive permeability change in several transformed cells, but not in untransformed cells. We previously demonstrated that in CHO-K1 cells, a transformed clone of Chinese hamster ovary cells, the external ATP-dependent permeability change was induced when the intracellular ATP concentration was reduced by a mitochondrial inhibitor (Kitagawa, T. and Akamatsu, Y. (1981) Biochim. Biophys. Acta 649, 76–82). A permeability change with similar characteristics was also observed when the CHO cells were treated with external ATP and a cytoskeleton-attacking agent such as vinblastine or cytochalasin B. Just like mitochondrial inhibitors, vinblastine could increase the sensitivity of transformed 3T3 cells to external ATP but showed no effect on passive permeability of normal 3T3 cells. However, in contrast with the effect of the mitochondrial inhibitors, the cytoskeleton drugs caused the permeability change with little reduction of intracellular ATP concentration, suggesting different actions of these two kinds of drug on the permeability change. The present results suggest an important role of cytoskeletal structures in controlling the external ATP-dependent permeability change in transformed cells. Possible effects of intracellular ATP on cytoskeletal structures are also discussed.     

Antiproliferative activity and interaction with proteins of N-cyclohexylacrylamide

N-cyclohexylacrylam?de (NCA), the synthesized compound, was evaluated for their cytotoxic activities against HeLa cancer cell line. Also, the current study has been analyzed by the use of molecular docking as protein-ligand interactions play a vital role in drug design. The docking study of NCA was performed with BCL-2, BCL-W, MCl-1, AKT, BRAF, CDK2, VEGFR, EGFR PARP1, CDK6 proteins. The 3D structures of proteins were obtained from the protein data bank and 3D structure of NCA compounds using GAUSSIAN. The in silico molecular docking results indicated that NCA compound can inhibit cancer-related proteins and can play a role as potential lead compounds for developing new drugs for cancer therapy with chemical modification.     

Degradation of Arabidopsis CRY2 is regulated by SPA proteins and phytochrome A

The UV-A/blue light photoreceptor crytochrome2 (cry2) plays a fundamental role in the transition from the vegetative to the reproductive phase in the facultative long-day plant Arabidopsis thaliana. The cry2 protein level strongly decreases when etiolated seedlings are exposed to blue light; cry2 is first phosphorylated, polyubiquitinated, and then degraded by the 26S proteasome. COP1 is involved in cry2 degradation, but several cop1 mutants show only reduced but not abolished cry2 degradation. SUPPRESSOR OF PHYA-105 (SPA) proteins are known to work in concert with COP1, and recently direct physical interaction between cry2 and SPA1 was demonstrated. Thus, we hypothesized that SPA proteins could also play a role in cry2 degradation. To this end, we analyzed cry2 protein levels in spa mutants. In all spa mutants analyzed, cry2 degradation under continuous blue light was alleviated in a fluence rate-dependent manner. Consistent with a role of SPA proteins in phytochrome A (phyA) signaling, a phyA mutant had enhanced cry2 levels, particularly under low fluence rate blue light. Fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy studies showed a robust physical interaction of cry2 with SPA1 in nuclei of living cells. Our results suggest that cry2 stability is controlled by SPA and phyA, thus providing more information on the molecular mechanisms of interaction between cryptochrome and phytochrome photoreceptors.     

Effect of the Antiphagocytic Agent Cytochalasin B on Macrophage Invasion by Leishmania mexicana Promastigotes and Trypanosoma cruzi Epimastigotes*

Unstimulated mouse peritoneal exudate cells were cultured on coverslips in Medium 199 containing 10% (v/v) calf serum. Cytochalasin B dissolved in dimethyl sulphoxide (DMSO) and diluted in Medium 199 was added to cultures to give final concentrations of 1, 5 and 10 μg/ml. Equal numbers of Leishmania mexicana promastigotes, Trypanosoma cruzi epimastigotes and sheep red cells were added to 24 hr cultures incubated at 37 C. The macrophage monolayers were fixed and stained at various time intervals. L. mexicana promastigotes and sheep red blood cells were found to attach to macrophages in the presence of the drug but did not enter the cells. When the medium containing the Cytochalasin was replaced with normal medium phagocytosis of the adherent parasites and red cells followed rapidly. T. cruzi epimastigotes were found inside macrophages in both drug-treated and drug-free cultures although the number found to be intracellular in the latter was significantly greater. This study suggests that L. mexicana promastigotes enter macrophages by being phagocytosed, whereas T. cruzi epimastigotes can actively penetrate these cells.     

Formation of novel endoplasmic and cortical microtubular arrays inAdiantum protonemal cells induced by blue light irradiation and acropetal centrifugation

Protonemal cells ofAdiantum capillus-veneris were grown under red light conditions over 6 days and exposed to blue light for 8 hr (and then dim green light for 1 hr for technical reasons), before they were centrifuged acropetally over at least 1 hr at 2,000×g. After this treatment, an arrangement of endoplasmic microtubules (MTs) that resembled the shape of a tadpole could be detected some distance below the nucleus in about 40% of the cells. The percentage of protonemata bearing this Mtstructure was dependent on centrifugation time as well as the time of blue light irradiation. The size of the structure was constant at any time of its existence. Additionally, a wide belt of transversally oriented cortical MTs in the upper part of the protonemata was detected in many cells after blue light irradiation and acropetal centrifugation. Its formation rate seemed to be also dependent on the period of blue light irradiation and centrifugation time. None of the endoplasmic and few of the cortical transverse MT patterns could be seen without blue light irradiation. A strict coincidence in the formation of both MT patterns was not seen. Further, a few tadpole-shaped MT arrays remained during mitosis, whereas the cortical transverse MT pattern was found in stages other than metaphase and anaphase.     

柯萨奇病毒B3型感染引起HeLa细胞内源性小干扰RNA的变化

探究柯萨奇病毒B3型(Coxsackie virus type B3, CVB3)感染的细胞是否诱导内源性小干扰RNA(small interfering RNA,siRNA)的产生。以CVB3接种HeLa细胞,在细胞培养箱(5% CO2、37 ℃)孵育1 h。随后加入含2%血清的细胞维持液,继续培养3 h和6 h后收集细胞。用高通量测序(二代测序) 试剂盒提取细胞RNA,并反转录合成cDNA,构建文库,上机测序。过滤数据,去除插入片段过长的序列、低质量序列、poly A序列和小片段序列,与已知的小RNA数据库比对鉴定siRNA。通过茎-环反转录-聚合酶链反应,证实内源性siRNA在感染CVB3后的表达。结果显示,感染CVB3 3 h和6 h后,HeLa细胞产生了多种内源性siRNA。其中内源性siRNA(novel_sir3502和novel_sir2806)在感染后3 h和6 h均可持续表达。经比对,novel_sir3502和 novel_sir2806均可以识别45S和28S核糖体前体RNA。结果提示,CVB3感染可能干扰核糖体成熟。     

Translocation of nucleolar phosphoprotein B23 ( ) induced by selective inhibitors of ribosome synthesis

To elucidate the possible role of nucleolar phosphoprotein B23 in ribosome synthesis, drugs which inhibit the processing of ribosomal RNA were employed. After treatment with actinomycin D, toyocamycin or high doses of α-amanitin, a uniform nucleoplasmic fluorescence was observed. Low doses of α-amanitin and the protein synthesis inhibitor puromycin and cycloheximide had no effect on protein B23 translocation. By ELISA immunoassay, there was a 60% decrease in the amount of protein B23 in the nucleoli of the actinomycin D-treated cells as compared with the control nucleoli. Conversely, the amount of protein B23 in the nucleoplasm (excluding nucleoli) was 3-fold higher in the actinomycin D-treated cells. Preribosomal ribunucleoprotein particles (pre-rRNPs) were extracted from isolated nucleoli of Novikoff hepatoma ascites cells and fractionated on sucrose density gradients. Protein B23 was found co-localized with the pre-rRNPs as determined by ELISA assays which agrees with previous studies. The proteins in these 80 S and 55 S pre-ribosomal ribonucleoprotein particles were fractionated by 10% gel electrophoresis. Immunoblots showed protein B23 was present in both pre-rRNPs.     

Enhanced rate of degradation of basic proteins by 26S immunoproteasomes

Immunoproteasomes are alternative forms of proteasomes specialized in the generation of MHC class I antigenic peptides and important for efficient cytokine production. We have identified a new biochemical property of 26S immunoproteasomes, namely the ability to hydrolyze basic proteins at greatly increased rates compared to constitutive proteasomes. This enhanced degradative capacity is specific for basic polypeptides, since substrates with a lower content in lysine and arginine residues are hydrolyzed at comparable rates by constitutive and immunoproteasomes. Crucially, selective inhibition of the immunoproteasome tryptic subunit β2i strongly reduces degradation of basic proteins. Therefore, our data demonstrate the rate limiting function of the proteasomal trypsin-like activity in controlling turnover rates of basic protein substrates and suggest new biological roles for immunoproteasomes in maintaining cellular homeostasis by rapidly removing a potentially harmful excess of free histones that can build up under different pathophysiological conditions.     

Ubiquitin B在HSP90抑制剂17-AAG诱导人宫颈癌HeLa细胞周期阻滞中的作用

目的 研究Ubiquitin B（Ubb）在热休克蛋白90（HSP90）抑制剂17-AAG诱导人宫颈癌HeLa细胞周期阻滞中的作用及机制.方法 不同浓度17-AAG处理HeLa细胞后,流式细胞术检测细胞周期分布,荧光分光光度法检测细胞蛋白酶体活性变化;Ubb siRNA 转染HeLa细胞后,Real Time PCR法检测Ubb干扰效应,Western 印迹检测细胞周期相关蛋白的表达改变.结果 17-AAG可以诱导HeLa细胞阻滞于G2/M期,同时显著增强细胞内糜蛋白酶样蛋白酶体活性,并且两者的变化均呈现剂量依赖性;干扰HeLa细胞内Ubb后,可以逆转17-AAG引起的G2/M期阻滞;17-AAG可明显下调HeLa细胞周期相关蛋白Cdk1和Hec1的表达,并且这一变化也是Ubb依赖的.结论 Ubb在17-AAG诱导的HeLa细胞周期阻滞中发挥重要作用,Ubb和HSP90抑制剂17-AAG在功能上相互关联,可能成为宫颈癌治疗的新靶点.     

细胞松弛素B对日本沼虾四倍体的适宜诱导条件的研究

本文研究了用细胞松弛素B(Cytochalasin B,CB)诱导日本沼虾(Macrobrachium nipponense)多倍体的处理条件和方法。试验水温分别为18—19℃、22—23℃,CB浓度为1.0—2.0mg/L,处理的起始时间在受精后5—9h,处理的持续时间为10—20min。结果表明,在水温为18—19℃时,四倍体卵子的最适诱导条件为:受精后7—8h,CB溶液的浓度1.5mg/L,处理20min,四倍体诱导率最高可达56.1%;在水温为22—23℃时,最适诱导条件为:在受精后6 h左右,CB溶液浓度为1.5mg/L,处理15—20min,四倍体诱导率最高可达54.3%。处理的起始时间和CB溶液的浓度对胚胎的四倍体率有显著影响(P<0.05);胚胎的成活率随CB浓度的提高与处理的持续时间的延长而下降。考虑到胚胎成活率因素,建议选择CB浓度为1.5mg/L,处理持续时间15—20min。