金黄滴虫细胞核微丝系统的初步观察

金黄滴虫细胞核内经常存在着许多直径约为7nm的微丝。这些徽丝大多组合成走向不定的徽丝束,微丝束交织而成遍布核内的网架。核被下面微丝束较多,它们的存在常使核被外凸而成隆脊。核内微丝与核内结构如核仁、染色质等似乎都是相连的。有些微丝横跨核被,一端位于核内,另一端位于核周腔中,并靠近叶绿体。核周腔和内质网腔中也存在着微丝和另一种纤维,印管状纤维。用细胞松弛素B处理后,细胞核、核周腔和内质网腔中的微丝均消失,细胞核的形态也发生变化,似乎微丝网架有支持细胞核的作用。核内微丝可能是在内质网中组装,然后经核周腔进入核内的。     

A novel tubular array associated with protein bodies in the rough endoplasmic reticulum ofopaque-2 maize

Summary The seed storage proteins of maize (Zea mays L.) are synthesized during endosperm development on membrane-bound polyribosomes. Protein body formation in normal genotypes occurs via a sequential deposition of the various types of zeins, and leads to the formation of spherical structures with a diameter of about l m. In the endosperm mutantopaque-2 the level of one zein class is reduced; these kernels exhibit an opaque phenotype instead of the vitreous phenotype displayed in normal genotypes, presumably due to the decrease in total zein protein at the time of desiccation. Previous microscopic examination ofopaque-2 protein bodies at 22 DAP (days after pollination) showed that the protein bodies were morphologically similar to those of normal genotypes. However, the endosperm ofopaque-2 maize at 14 DAP contains tubular arrays within the rough endoplasmic reticulum. These tubular arrays are tightly associated with the developing protein bodies. Long strands of tubules, sometimes 10 m in length, are observed in the endosperm, and partially formed protein bodies often seem to be forming directly from these tubular arrays. No immunostaining is associated with this tubular material when any of the anti-zein antibodies are used.Abbreviations BSA bovine serum albumin - DAP days after pollination - IgG immunoglobulin G Dedicated to Professor Eldon H. Newcomb in recognition of his contributions to cell biology     

Photoreceptor membrane breakdown in the spider Dinopis: GERL differentiation in the receptors

Summary In the spider Dinopis, retinae of the posterior median eyes synthesise new photoreceptor membrane in bulk at dusk and destroy it at dawn (Blest, 1978). During the dawn period, there is a rapid, anticipatory differentiation of unusual organelles from the rough endoplasmic reticulum (RER) in the intermediate segments of the receptors. This system is classified as GERL. Its products appear to play a role in the autolysis of photoreceptor membrane. Consistent topographical relationship to Golgi bodies has not been determined. Circumscribed regions of RER whorls first reorganise to yield fenestrated profiles; these differentiate further to a number of structures by condensation and loss of ribosomes. Smooth tubular profiles are termed rigid tubules to indicate their probable homology with the rigid lamellae of vertebrate secretory cells. More complex smooth multilocular bodies are also produced. Evidence is discussed which implies that both rigid tubules and multilocular bodies give rise to condensing vacuoles. These, in turn, pinch off coated vesicles assembled as Nebenkerne. Some rigid tubules are transported to the interrhabdomeral cytoplasm of the receptive segments. At late stages of differentiation, rigid tubules, multilocular bodies and Nebenkerne give strong, positive responses to zinc iodide-osmium tetroxide (ZIO) treatment; early stages and both cis and trans Golgi components do not. GERL differentiation is independent of immediate illumination of the retina at dawn. It is suggested to mediate the lysis of membrane degradation products by the production of hydrolases.We thank Professor D.T. Anderson F.R.S. for our use of field facilities at the Crommelin Biological Field Station of Sydney University at Warrah, Pearl Beach, N.S.W., and Andrew and Sally Austin and Sally Stowe for help in the field. We are indebted to Rod Whitty and the Electron Microscopy Unit for advice and support throughout these studies     

renalase在人近曲肾小管上皮细胞系的表达与分泌

目的:探讨renalase在人近曲肾小管上皮细胞系(HK-2)的表达与分泌,为进一步研究细胞水平renalase及其通路建立稳定的实验平台。方法:以HK-2细胞系作为研究材料。①应用Westernblot方法检测renalase蛋白的表达。②用real-timePCR方法检测renalasemRNA表达的变化。③用ELISA方法检测细胞上清液中renalase的浓度。结果:在mRNA水平及蛋白水平均检测到renalase表达。结论:首次在mRNA水平及蛋白水平证实了HK-2细胞能够表达renalase,为进一步研究儿茶酚胺或缺血缺氧刺激下细胞renalase的表达奠定了基础。     

Amphiphile-induced tubular budding of the bilayer membrane

Amphiphile-induced tubular budding of the erythrocyte membrane was studied using transmission electron microscopy. No chiral patterns of the intramembraneous particles were found, either on the cylindrical buds, or on the tubular nanoexovesicles. In agreement with these observations, the tubular budding may be explained by in-plane ordering of anisotropic membrane inclusions in the buds where the difference between the principal membrane curvatures is very large. In contrast to previously reported theories, no direct external mechanical force is needed to explain tubular budding of the bilayer membrane.     

Signal transduction in endothelial cells by the angiogenesis inhibitor histidine-rich glycoprotein targets focal adhesions

Histidine-rich glycoprotein (HRGP) is an abundant heparin-binding plasma protein. We have shown that a fragment released from the central histidine/proline-rich (His/Pro-rich) domain of HRGP blocks endothelial cell migration in vitro and vascularization and growth of murine fibrosarcoma in vivo. The minimal active HRGP domain exerting the anti-angiogenic effect was recently narrowed down to a 35 amino acid peptide, HRGP330, derived from the His/Pro-rich domain of HRGP. By use of a signal transduction antibody array representing 400 different signal transduction molecules, we now show that HRGP and the synthetic peptide HRGP330 specifically induce tyrosine phosphorylation of focal adhesion kinase and its downstream substrate paxillin in endothelial cells. HRGP/HRGP330 treatment of endothelial cells induced disruption of actin stress fibers, a process reversed by treatment of cells with the FAK inhibitor geldanamycin. In addition, VEGF-mediated endothelial cell tubular morphogenesis in a three-dimensional collagen matrix was inhibited by HRGP and HRGP330. In contrast, VEGF-induced proliferation was not affected by HRGP or HRGP330, demonstrating the central role of cell migration during tube formation. In conclusion, our data show that HRGP targets focal adhesions in endothelial cells, thereby disrupting the cytoskeletal organization and the ability of endothelial cells to assemble into vessel structures.     

Characterization of Rab21-positive tubular endosomes induced by PI3K inhibitors

We found that wortmannin, a potent phosphoinositide 3-kinase (PI3K) inhibitor, markedly induced the formation of Rab21-positive tubular compartments in A431 cells. By time-lapse fluorescence microscopy of live cells co-expressing fluorescent protein-fused Rab21 and other marker proteins, it was shown that the Rab21-positive tubules in wortmannin-treated cells were derived from Rab5-positive early endosomes, but not from late endosomes, recycling endosomes, lysosomes or the trans-Golgi network. The formation of Rab21-positive tubules was very dynamic and required microtubules. Rab21-positive tubules were also formed by the treatment of cells with 3-methyladenine (3-MA), which inhibits class III PI3K rather than class I PI3K. Furthermore, the loss of PI(3)P correlated with the tubulation of Rab21-positive endosomes in cells co-expressing fluorescent protein-fused Rab21 and a tandem FYVE domain. These results suggest that the lowering of PI(3)P as a result of class III PI3K inhibition may be an important cue for the morphological change of Rab21-positive early endosomes from vesicular to tubular form.     

Role of STIM1/ORAI1-mediated store-operated Ca2+ entry in skeletal muscle physiology and disease

Store-operated Ca²⁺ entry (SOCE) is a Ca²⁺ entry mechanism activated by depletion of intracellular Ca²⁺ stores. In skeletal muscle, SOCE is mediated by an interaction between stromal-interacting molecule-1 (STIM1), the Ca²⁺ sensor of the sarcoplasmic reticulum, and ORAI1, the Ca²⁺-release-activated-Ca²⁺ (CRAC) channel located in the transverse tubule membrane. This review focuses on the molecular mechanisms and physiological role of SOCE in skeletal muscle, as well as how alterations in STIM1/ORAI1-mediated SOCE contribute to muscle disease. Recent evidence indicates that SOCE plays an important role in both muscle development/growth and fatigue. The importance of SOCE in muscle is further underscored by the discovery that loss- and gain-of-function mutations in STIM1 and ORAI1 result in an eclectic array of disorders with clinical myopathy as central defining component. Despite differences in clinical phenotype, all STIM1/ORAI1 gain-of-function mutations-linked myopathies are characterized by the abnormal accumulation of intracellular membranes, known as tubular aggregates. Finally, dysfunctional STIM1/ORAI1-mediated SOCE also contributes to the pathogenesis of muscular dystrophy, malignant hyperthermia, and sarcopenia. The picture to emerge is that tight regulation of STIM1/ORAI1-dependent Ca²⁺ signaling is critical for optimal skeletal muscle development/function such that either aberrant increases or decreases in SOCE activity result in muscle dysfunction.     

Outdoor continuous culture of Porphyridium cruentum in a tubular photobioreactor: quantitative analysis of the daily cyclic variation of culture parameters

The present work reports on the daily cyclic variation of oxygen generation rates, carbon consumption rates, photosynthetic activities, growth rates and biochemical composition of the biomass in a pilot plant continuous outdoor culture of the microalgae Porphyridium cruentum. A linear relationship between the external irradiance and the average irradiance inside the culture was found. In addition, the oxygen generation and carbon consumption rates were found to be a function of the average irradiance inside the culture. A reduction in photosynthetic activity of the cells at noon and recovery in the afternoon was also observed. Therefore, the cells showed a short-term response of parameters such as oxygen generation rate as well as carbon consumption rate with external and average irradiance; a model of photosynthesis rate considering photoinhibition is proposed. This model is a useful tool for the operation and scaleup of tubular photobioreactors, and can be used for determining CO₂ requirements of the system. The higher the photosynthesis rates, the lower the carbon losses, ranging from 25% at noon to 100% during the night. The growth rate showed a linear relationship with the daily mean average irradiance inside the culture with a long-term response. Likewise, a linear relationship among the oxygen generation rate and the growth rate was obtained. With respect to the biochemical composition of the biomass, the cells showed a long-term response of metabolic routes to mean daily culture conditions. During the illuminated period, energy was stored as carbohydrates and synthesis of proteins was low. During the night, the stored carbohydrates were consumed. The fatty acid dry weight (DW) content decreased during the daylight period, whereas the fatty acid profile, as total fatty acids, was a function of growth rate. A short-term variation of exopolysaccharides synthesis with solar irradiance was also observed, i.e. the higher the external irradiance the higher the excretion of exopolysaccharides as a protection against adverse culture conditions.     

Modelling of a continuous pilot photobioreactor for microalgae production

In this study, a model of a continuous pilot photobioreactor for microalgae production is proposed. Three aspects have been studied: the modelling of kinetic growth, the gas-liquid transfer and the hydrodynamics in the photobioreactor. The modelling of each aspect has been developed with the dynamic simulation software SpeedUp, after experimental studies, then validated step-by-step. The connection of these three aspects aims to predict and optimise biomass production of the pilot plant.