Models for contact-mediated pattern formation: cells that form parallel arrays

Kinetic continuum models are derived for cells that crawl over a 2D substrate, undergo random reorientation, and turn in response to contact with a neighbor. The integro-partial differential equations account for changes in the distribution of orientations in the population. It is found that behavior depends on parameters such as total mass, random motility, adherence, and sloughing rates, as well as on broad aspects of the contact response. Linear stability analysis, and numerical, and cellular automata simulations reveal that as parameters are varied, a bifurcation leads to loss of stability of a uniform (isotropic) steady state, in favor of an (anisotropic) patterned state in which cells are aligned in parallel arrays.     

Cell growth and water relations of the halophyte,Atriplex nummularia L., in response to NaCl

Summary Growth reduction or cessation is an initial response of Atriplex nummularia L. cells to NaCl. However, A. nummularia L. cells that are adapted to 342 and 428 mM NaCl are capable of sustained growth in the presence of salt. Cells that are adapted to NaCl exhibit a reduced rate of division compared to unadapted cells. Unlike salt adapted cells of the glycophyte Nicotiana tabacum L., A. nummularia L. cells do not exhibit reduced rate of cell expansion after adaptation. However, the cell expansion rate of unadapted A. nummularia L. cells is considerably slower than that of unadapted glycophyte cells and this normally low rate of cell expansion may contribute to the enhanced capacity of the halophyte to tolerate salt. Turgor of NaCl adapted cells was equivalent to unadapted cells indicating that the cells of the halophyte do not respond to salt by osmotic over adjustment as reported for the glycophyte tobacco (Binzel et al. 1985, Plant Physiol. 79:118–125).     

三氧化二砷对食管癌细胞增殖和热休克蛋白70表达的影响

目的：研究三氧化二砷（As2O3）对食管癌细胞增殖和热休克蛋白70（HSP70）表达的影响。方法：通过相差显微镜、流式细胞术、免疫细胞化学染色和免疫印迹分析等方法观察As2O3对人食管癌细胞株EC1的作用效果和作用机制。结果：与对照组相比,经2μmol/L和5μmol/Las2O3作用的细胞出现明显的生长抑制,G2/M期细胞比例增加;2μmol/Las2O3作用48h后经Ecl细胞HSP70（heat shock protein70）及HSC70(heat shock cognate protein70)表达均增加。结论：As2O3诱导食管癌细胞G2/M期阻滞抑制细胞增殖和生长;HSP70的升高是细胞对As2O3作用后出现的应激反应,并与细胞周期阻滞相关。     

异种动物血清对体外培养人肿瘤细胞生长的影响

目的观察不同种属来源和浓度的动物血清对体外培养的肿瘤细胞（A549、MCF-7、BGC-823）生长的影响。探讨血清药理实验中血清供体动物的选择及血清添加量的问题。方法设置5种血清（牛、人、兔、大鼠、小鼠）及血清量（10%、20%、40%、60%、80%）的培养体系,用MTT法检测细胞增殖情况。结果不同种属来源的动物血清对肿瘤细胞生长的影响作用各不相同。从总的趋势来看,牛血清更适宜人肿瘤细胞生长,小鼠血清适应性最差。且随着加入量的增加,大多数血清会对肿瘤细胞的生长产生负效应。结论在肿瘤血清药理学试验中,为排除血清本身带给试验的干扰,应测定正常动物血清对肿瘤细胞增殖的影响,且血清添加量以小于20%为宜。     

Selective Changes in Cell Bodies and Growth Cones of Nerve Growth Factor-Differentiated PC12 Cells Induced by Chemical Hypoxia

Abstract: Cytosolic free Ca²⁺ concentration ([Ca²⁺]_i) was measured in differentiated PC12 cells to test whether chemical hypoxia selectively alters intracellular Ca²⁺ in growth cones and cell bodies. Hypoxia increased [Ca²⁺]_i and exaggerated its response to K⁺ depolarization in both parts of the cells. [Ca²⁺]_i in the cell bodies was greater than that in the growth cones under resting conditions and in response to K⁺ or hypoxia. Ca²⁺-channel blockers selectively altered these responses. The L-channel blocker nifedipine reduced [Ca²⁺]_i following K⁺ depolarization by 67% in the cell bodies but only 25% in the growth cones. In contrast, the N-channel blocker ω-conotoxin GVIA (ω-CgTX) diminished K⁺-induced changes in [Ca²⁺]_i only in the growth cones. During hypoxia, nifedipine was more effective in the cell bodies than in the growth cones. During hypoxia, ω-CgTX diminished K⁺-induced changes by 50–75% in both parts of the cell, but only immediately after depolarization. The combination of nifedipine and ω-CgTX diminished the [Ca²⁺]_i response to K⁺ with or without hypoxia by >90% in the cell body and 70% in the growth cones. Thus, the increased Ca²⁺ entry with K⁺ during hypoxia is primarily through L channels in the cell bodies, whereas in growth cones influx through L and N channels is about equal. The results show that chemical hypoxia selectively alters Ca²⁺ regulation in the growth cone and cell body of the same cell.     

Sinomenine inhibits primary CD4+ T-cell proliferation via apoptosis

Sinomenine is an active component isolated from Sinomenium acutum and is widely used as an immunosuppressive drug for treating autoimmune diseases. CD4(+) T-cell population plays a key role in adaptive immune response and is related to some autoimmune diseases. In this study, we investigated the possible immunosuppressive effect of sinomenine on CD4(+) T cells and its underlying mechanism. Our data demonstrated that sinomenine remarkably suppressed the proliferation of CD4(+) T cells, blocked the cell cycle progression from G0/G1 phase to S plusG2/M phases. Finally, the immunosuppressive activity elicited by sinomenine in CD4(+) primary lymphocytes was found to be largely accounted for by caspase 3-dependent cells apoptosis. Sinomenine did not significantly alter the expression of bcl-2 in activated CD4(+) primary T cells, suggesting that bcl-2 might not be involved in sinomenine-induced T cells apoptosis. In sum, this study proposes a novel mechanism for the immunosuppressive function of sinomenine on primary mouse CD4(+) T cells.     

Engraftment of a Galactose Receptor Footprint onto Adeno-associated Viral Capsids Improves Transduction Efficiency

New viral strains can be evolved to recognize different host glycans through mutagenesis and experimental adaptation. However, such mutants generally harbor amino acid changes that affect viral binding to a single class of carbohydrate receptors. We describe the rational design and synthesis of novel, chimeric adeno-associated virus (AAV) strains that exploit an orthogonal glycan receptor for transduction. A dual glycan-binding AAV strain was first engineered as proof of concept by grafting a galactose (Gal)-binding footprint from AAV serotype 9 onto the heparan sulfate-binding AAV serotype 2. The resulting chimera, AAV2G9, continues to bind heparin affinity columns but interchangeably exploits Gal and heparan sulfate receptors for infection, as evidenced by competitive inhibition assays with lectins, glycans, and parental AAV strains. Although remaining hepatotropic like AAV2, the AAV2G9 chimera mediates rapid onset and higher transgene expression in mice. Similarly, engraftment of the Gal footprint onto the laboratory-derived strain AAV2i8 yielded an enhanced AAV2i8G9 chimera. This new strain remains liver-detargeted like AAV2i8 while selectively transducing muscle tissues at high efficiency, comparable with AAV9. The AAV2i8G9 chimera is a promising vector candidate for targeted gene therapy of cardiac and musculoskeletal diseases. In addition to demonstrating the modularity of glycan receptor footprints on viral capsids, our approach provides design strategies to expand the AAV vector toolkit.     

Differential Phosphorylation of RhoGDI Mediates the Distinct Cycling of Cdc42 and Rac1 to Regulate Second-phase Insulin Secretion

Cdc42 cycling through GTP/GDP states is critical for its function in the second/granule mobilization phase of insulin granule exocytosis in pancreatic islet beta cells, although the identities of the Cdc42 cycling proteins involved remain incomplete. Using a tandem affinity purification-based mass spectrometry screen for Cdc42 cycling factors in beta cells, RhoGDI was identified. RNA interference-mediated depletion of RhoGDI from isolated islets selectively amplified the second phase of insulin release, consistent with the role of RhoGDI as a Cdc42 cycling factor. Replenishment of RhoGDI to RNA interference-depleted cells normalized secretion, confirming the action of RhoGDI to be that of a negative regulator of Cdc42 activation. Given that RhoGDI also regulates Rac1 activation in beta cells, and that Rac1 activation occurs in a Cdc42-dependent manner, the question as to how the beta cell utilized RhoGDI for differential Cdc42 and Rac1 cycling was explored. Co-immunoprecipitation was used to determine that RhoGDI-Cdc42 complexes dissociated upon stimulation of beta cells with glucose for 3 min, correlating with the timing of glucose-induced Cdc42 activation and the onset of RhoGDI tyrosine phosphorylation. Glucose-induced disruption of RhoGDI-Rac1 complexes occurred subsequent to this, coincident with Rac1 activation, which followed the onset of RhoGDI serine phosphorylation. RhoGDI-Cdc42 complex dissociation was blocked by mutation of RhoGDI residue Tyr-156, whereas RhoGDI-Rac1 dissociation was blocked by RhoGDI mutations Y156F and S101A/S174A. Finally, expression of a triple Y156F/S101A/S174A-RhoGDI mutant specifically inhibited only the second/granule mobilization phase of glucose-stimulated insulin secretion, overall supporting the integration of RhoGDI into the activation cycling mechanism of glucose-responsive small GTPases.