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1.
The effects of hepatitis B virus (HBV) on established human cell lines of various tissue origins were evaluated by clonal or colorimetric assays in methylcellulose culture. HBV exposure inhibited the growth of six hemopoietic cell lines, while similar incubation did not affect the growth of seven nonhemopoietic carcinoma cell lines of breast, colon, liver, and stomach origin. The inhibition of hemopoietic cell line colony formation was dependent on the presence of intact viral (Dane) particles and the ratio of exposure of virions to cells and was reversible with antibodies to pre-S1, pre-S2, and S envelope protein epitopes. Purified HBV DNA, surface antigen pre-S antigens, and core antigen did not inhibit cell line growth. These results further demonstrate the tropism of HBV for cells of hemopoietic origin, confirming our previous findings on the effects of HBV on the growth of normal bone marrow progenitor cells in vitro. Established human tissue culture cell lines may be used to study the interactions of hemopoietic cells with HBV. 相似文献
2.
The pericentriolar material in Chinese hamster ovary cells nucleates microtubule formation 总被引:48,自引:38,他引:10
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The structure and function of the centrosomes from Chinese hamster ovary (CHO) cells were investigated by electron microscopy of negatively stained wholemount preparations of cell lysates. Cells were trypsinized from culture dishes, lysed with Triton X-100, sedimented onto ionized, carbon-coated grids, and negatively stained with phosphotungstate. The centrosomes from both interphase and dividing cells consisted of pairs of centrioles, a fibrous pericentriolar material, and a group of virus-like particles which were characteristic of the CHO cells and which served as markers for the pericentriolar material. Interphase centrosomes anchored up to two dozen microtubules when cells were lysed under conditions which preserved native microtubules. When Colcemid-blocked mitotic cells, initially devoid of microtubules, were allowed to recover for 10 min, microtubules formed at the pericentriolar material, but not at the centrioles. When lysates of Colcemid-blocked cells were incubated in vitro with micotubule protein purified from porcine brain tissue, up to 250 microtubules assembled at the centrosomes, similar to the number of microtubules that would normally form at the centrosome during cell division. A few microtubules could also be assembled in vitro onto the ends of isolated centrioles from which the pericentriolar material had been removed, forming characteristic axoneme- like bundles. In addition, microtubules; were assembled onto fragments of densely staining, fibrous material which was tentatively identified as periocentriolar material by its association of CHO can initiate and anchor microtubules both in vivo and in vitro. 相似文献
3.
T N Salzmann R W Ratcliffe F A Bouffard B G Christensen 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1980,289(1036):191-195
A versatile stereocontrolled total synthesis of thienamycin starting from L-aspartic acid is reported. Stereocontrol is achieved by potassium tri-sec-butylborohydride reduction of a thermodynamically formed 3 alpha-acetylazetidinone intermediate. The key [3.2.0] bicyclic ring system is prepared by a metal catalyzed carbene insertion reaction. 相似文献
4.
啤酒多倍体酵母菌原生质体已成功地与单倍体原生质体进行融合。经细胞壁再生后,稳定的融合重组体被分离出来。这些融合体的基因分析表明,融合体中含有双亲的基因型。孢子形成良好,且每个子囊中含有四个孢子,每个孢子确实是二倍体。这样原生质体融合就提供了一个对啤酒酿造酵母进行遗传分析的方法。但是如果没有一个方便的杂交技术,这个方法将是很困难的。 相似文献
5.
Helene M. Langevin Kirsten N. Storch Robert R. Snapp Nicole A. Bouffard Gary J. Badger Alan K. Howe Douglas J. Taatjes 《Histochemistry and cell biology》2010,133(4):405-415
Studies in cultured cells have shown that nuclear shape is an important factor influencing nuclear function, and that mechanical
forces applied to the cell can directly affect nuclear shape. In a previous study, we demonstrated that stretching of whole
mouse subcutaneous tissue causes dynamic cytoskeletal remodeling with perinuclear redistribution of α-actin in fibroblasts
within the tissue. We have further shown that the nuclei of these fibroblasts have deep invaginations containing α-actin.
In the current study, we hypothesized that tissue stretch would cause nuclear remodeling with a reduced amount of nuclear
invagination, measurable as a change in nuclear concavity. Subcutaneous areolar connective tissue samples were excised from
28 mice and randomized to either tissue stretch or no stretch for 30 min, then examined with histochemistry and confocal microscopy.
In stretched tissue (vs. non-stretched), fibroblast nuclei had a larger cross-sectional area (P < 0.001), smaller thickness (P < 0.03) in the plane of the tissue, and smaller relative concavity (P < 0.005) indicating an increase in nuclear convexity. The stretch-induced loss of invaginations may have important influences
on gene expression, RNA trafficking and/or cell differentiation. 相似文献
6.
Garret Suen Jarrod J. Scott Frank O. Aylward Sandra M. Adams Susannah G. Tringe Adrián A. Pinto-Tomás Clifton E. Foster Markus Pauly Paul J. Weimer Kerrie W. Barry Lynne A. Goodwin Pascal Bouffard Lewyn Li Jolene Osterberger Timothy T. Harkins Steven C. Slater Timothy J. Donohue Cameron R. Currie 《PLoS genetics》2010,6(9)
Herbivores can gain indirect access to recalcitrant carbon present in plant cell walls through symbiotic associations with lignocellulolytic microbes. A paradigmatic example is the leaf-cutter ant (Tribe: Attini), which uses fresh leaves to cultivate a fungus for food in specialized gardens. Using a combination of sugar composition analyses, metagenomics, and whole-genome sequencing, we reveal that the fungus garden microbiome of leaf-cutter ants is composed of a diverse community of bacteria with high plant biomass-degrading capacity. Comparison of this microbiome''s predicted carbohydrate-degrading enzyme profile with other metagenomes shows closest similarity to the bovine rumen, indicating evolutionary convergence of plant biomass degrading potential between two important herbivorous animals. Genomic and physiological characterization of two dominant bacteria in the fungus garden microbiome provides evidence of their capacity to degrade cellulose. Given the recent interest in cellulosic biofuels, understanding how large-scale and rapid plant biomass degradation occurs in a highly evolved insect herbivore is of particular relevance for bioenergy. 相似文献
7.
The genome sequence of the leaf-cutter ant Atta cephalotes reveals insights into its obligate symbiotic lifestyle 总被引:1,自引:0,他引:1
Suen G Teiling C Li L Holt C Abouheif E Bornberg-Bauer E Bouffard P Caldera EJ Cash E Cavanaugh A Denas O Elhaik E Favé MJ Gadau J Gibson JD Graur D Grubbs KJ Hagen DE Harkins TT Helmkampf M Hu H Johnson BR Kim J Marsh SE Moeller JA Muñoz-Torres MC Murphy MC Naughton MC Nigam S Overson R Rajakumar R Reese JT Scott JJ Smith CR Tao S Tsutsui ND Viljakainen L Wissler L Yandell MD Zimmer F Taylor J Slater SC Clifton SW Warren WC Elsik CG Smith CD Weinstock GM Gerardo NM Currie CR 《PLoS genetics》2011,7(2):e1002007
Leaf-cutter ants are one of the most important herbivorous insects in the Neotropics, harvesting vast quantities of fresh leaf material. The ants use leaves to cultivate a fungus that serves as the colony's primary food source. This obligate ant-fungus mutualism is one of the few occurrences of farming by non-humans and likely facilitated the formation of their massive colonies. Mature leaf-cutter ant colonies contain millions of workers ranging in size from small garden tenders to large soldiers, resulting in one of the most complex polymorphic caste systems within ants. To begin uncovering the genomic underpinnings of this system, we sequenced the genome of Atta cephalotes using 454 pyrosequencing. One prediction from this ant's lifestyle is that it has undergone genetic modifications that reflect its obligate dependence on the fungus for nutrients. Analysis of this genome sequence is consistent with this hypothesis, as we find evidence for reductions in genes related to nutrient acquisition. These include extensive reductions in serine proteases (which are likely unnecessary because proteolysis is not a primary mechanism used to process nutrients obtained from the fungus), a loss of genes involved in arginine biosynthesis (suggesting that this amino acid is obtained from the fungus), and the absence of a hexamerin (which sequesters amino acids during larval development in other insects). Following recent reports of genome sequences from other insects that engage in symbioses with beneficial microbes, the A. cephalotes genome provides new insights into the symbiotic lifestyle of this ant and advances our understanding of host-microbe symbioses. 相似文献
8.
Dynamic fibroblast cytoskeletal response to subcutaneous tissue stretch ex vivo and in vivo 总被引:7,自引:0,他引:7
Langevin HM Bouffard NA Badger GJ Iatridis JC Howe AK 《American journal of physiology. Cell physiology》2005,288(3):C747-C756
Cytoskeleton-dependent changes in cell shape are well-established factors regulating a wide range of cellular functions including signal transduction, gene expression, and matrix adhesion. Although the importance of mechanical forces on cell shape and function is well established in cultured cells, very little is known about these effects in whole tissues or in vivo. In this study we used ex vivo and in vivo models to investigate the effect of tissue stretch on mouse subcutaneous tissue fibroblast morphology. Tissue stretch ex vivo (average 25% tissue elongation from 10 min to 2 h) caused a significant time-dependent increase in fibroblast cell body perimeter and cross-sectional area (ANOVA, P < 0.01). At 2 h, mean fibroblast cell body cross-sectional area was 201% greater in stretched than in unstretched tissue. Fibroblasts in stretched tissue had larger, "sheetlike" cell bodies with shorter processes. In contrast, fibroblasts in unstretched tissue had a "dendritic" morphology with smaller, more globular cell bodies and longer processes. Tissue stretch in vivo for 30 min had effects that paralleled those ex vivo. Stretch-induced cell body expansion ex vivo was inhibited by colchicine and cytochalasin D. The dynamic, cytoskeleton-dependent responses of fibroblasts to changes in tissue length demonstrated in this study have important implications for our understanding of normal movement and posture, as well as therapies using mechanical stimulation of connective tissue including physical therapy, massage, and acupuncture. mechanotransduction; connective tissue; tensegrity; musculoskeletal manipulations; acupuncture 相似文献
9.
Decreased gene expression from T7 promoters may be due to impaired production of active T7 RNA polymerase 总被引:1,自引:0,他引:1
Background
Protein expression vectors that utilize the bacteriophage T7 polymerase/promoter system are capable of very high levels of protein production. Frequently, however, expression from these vectors does not reliably achieve optimal levels of protein production. Strategies have been proposed previously that successfully maintain high expression levels, however we sought to determine the cause of induction failure. 相似文献10.