Magnesium Adenosine 5[prime]-Triphosphate-Energized Transport of Glutathione-S-Conjugates by Plant Vacuolar Membrane Vesicles

By characterization of the uptake of glutathione-S-conjugates, principally dinitrophenyl-S-glutathione (DNP-GS), by vacuolar membrane vesicles, we demonstrate that a subset of energy-dependent transport processes in plants are not H+-coupled but instead are directly energized by MgATP. The most salient features of this transport pathway are: (a) its specific, obligate requirement for MgATP as energy source; (b) the necessity for hydrolysis of the [gamma]-phosphate of MgATP for uptake; (c) the insensitivity of uptake to uncouplers of the transtonoplast H+ gradient (carbonylcyanide 4-trifluoromethoxyphenylhydrazone, gramicidin-D, and NH4Cl); (d) its pronounced sensitivity to vanadate and partial inhibition by vinblastine and verapamil; (e) the lack of chemical modification of DNP-GS either during or after transport; (f) the capacity of S-conjugates of chloroacetanilide herbicides, such as metolachlor-GS, but not free herbicide, to inhibit uptake; and (g) the ability of vacuolar membrane vesicles purified from a broad range of plant species, including Arabidopsis, Beta, Vigna, and Zea, to mediate MgATP-dependent, H+-electrochemical potential difference-independent DNP-GS uptake. On the basis of these findings it is proposed that the transport of DNP-GS across the vacuolar membrane of plant cells is catalyzed by a glutathione-conjugate transporter that directly employs MgATP rather than the energy contained in the transtonoplast H+-electrochemical potential difference to drive uptake. The broad distribution of the vacuolar DNP-GS transporter and its inhibition by metolachlor-GS are consistent with the notion that it plays a general role in the vacuolar sequestration of glutathione-conjugable cytotoxic agents.     

The effect of lysolecithin on prostanoid and platelet-activating factor formation by human gall-bladder mucosal cells

It has been demonstrated that lysolecithin (lysophosphatidyl choline, LPC) produces experimental cholecystitis in cats mediated by arachidonic acid metabolites. LPC is a cytolytic agent that has been postulated as a contributing factor in the development of cholecystitis in humans. The purpose of this research was to evaluate the effect of LPC on human gall-bladder mucosal cell phospholipase A(2) and cyclooxygenase activity. Gall-bladder mucosal cells were isolated from the gall-bladders of patients undergoing routine cholecystectomy. Fresh, isolated cells were maintained in tissue culture and stimulated with varying doses of LPC. Platelet-activating factor concentration was quantitated as an index of phospholipase A(2) activity and prostanoids were measured as an index of cyclooxygenase activity. Also, the effect of LPC on cyclooxygenase 1 and 2 expression in microsomal protein was evaluated. LPC caused dose related increases in 6-keto-PGF(1alpha) and PAF produced by human gall-bladder mucosal cells. Exposure of human gall-bladder mucosal cells to LPC failed to elicit expression of constitutive cyclooxygenase-1, while the expression of inducible cyclooxygenase-2 was increased. The results of this study indicate that LPC induces the formation of prostanoids and PAF by human gall-bladder mucosal cells, suggesting that this substance may promote the development of gall-bladder inflammation.     

小麦中期染色体银染蛋白的分析

对小麦中期染色体中银染蛋白的大小、形状和分布频率进行图像分析,看到：染色体顺的银染蛋白以颗粒状的形式存在,其大小不同,分布不均匀,数量差异也较大;从形状来看,大的银粒为点状,小的银粒有的为点状,有的实际为短纤维状,结果表明：染色体骨架在小麦中是真实存在的,骨架蛋白以颗粒和纤维状的形式分布于整个染色体中。     

Polyamine Titer in the Embryonic Axis and Cotyledons of Glycine max (L.) during Seed Growth and Maturation

Active polyamine metabolism occurs in Glycine max (L.) seeds during development. Most (≥97%) of putrescine (Put), spermidine (Spd), spermine (Spm), and cadaverine (Cad) are present as free forms in the growing embryo. In the cotyledon or embryonic axis, Put decreases to a nearly undetectable level, while Spd level sharply increases as seed dry weight accumulation progresses. Spm level in the axis also increases along with the Spd level. There is little change in Spm level in the cotyledons. Maturation and dehydration results in a slight reduction of Spd level in the cotyledons. Cad is present in relatively large quantities (5.5-12 micromoles per gram dry weight) in the axes of mature soybean seeds. Only traces of Cad, as expressed on a dry weight basis, are found in the developing or mature cotyledons. The synthesis and accumulation of Cad in the axis begins at the time when the axis or the seed accumulates 30 to 50% of its maximum dry weight. The Cad accumulation (0.8 nanomole per axis per day) proceeds until the later stages of dehydration. When soybean plants are subjected to complete defoliation and shade during the midpoint of seed maturation, Cad accumulation in the axis and seed dry weight accumulation ceased almost immediately. The treatment, however, does not affect the viability of soybean seeds.     

An Auxin-Responsive Promoter Is Differentially Induced by Auxin Gradients during Tropisms

We constructed a chimeric gene consisting of a soybean small auxin up RNA (SAUR) promoter and leader sequence fused to an Escherichia coli [beta]-glucuronidase (GUS) open reading frame and a 3[prime] untranslated nopaline synthase sequence from Agrobacterium tumefaciens. This chimeric gene was used to transform tobacco by Agrobacterium-mediated transformation. In R2 etiolated transgenic tobacco seedlings, GUS expression occurred primarily in elongation regions of hypocotyls and roots. In green plants, GUS was expressed primarily in the epidermis and cortex of stems and petioles, as well as in elongation regions of anther filaments in developing flowers. GUS expression was responsive to exogenous auxin in the range of 10-8 to 10-3 M. During gravitropism and phototropism, the GUS activity became greater on the more rapidly elongating side of tobacco stems. Auxin transport inhibitors and other manipulations that blocked gravitropism also blocked the asymmetric distribution of GUS activity in gravistimulated stems. Light treatment of dark-grown seedlings resulted in a rapid decrease in GUS activity. Light-induced decay in GUS activity was fully reversed by application of auxin. Taken together, our results add support for the formation of an asymmetric distribution of auxin at sites of action during tropism.     

DISCOVERY OF MONOGRAPTIDS IN BASAL PART OF LOWER SILURIAN FROM S. ANHUI WITH SPECIAL REFERENCE TO THEIR ORIGIN

For a long time, the evolutionary series of a idoraptids-dimorphograptids-monograptids has been generally recognized by graptolite researchers. In the past years, the akidograptids were found to appear in the Lower Silurian Parakidograptus acuminatus Zone, while the dimorphograptids in the P. acuminatus and Orthograpius vesiculosus Zones, but the monograptids appeared as late as in the O. vesiculosus zone; this evolutionary series can be easily accepted by other people. Chen Xu and Lin Yao-kun (1978) pu...     

Mechanisms of chromatin-based epigenetic inheritance

Multi-cellular organisms such as humans contain hundreds of cell types that share the same genetic information(DNA sequences), and yet have different cellular traits and functions. While how genetic information is passed through generations has been extensively characterized, it remains largely obscure how epigenetic information encoded by chromatin regulates the passage of certain traits, gene expression states and cell identity during mitotic cell divisions, and even through meiosis. In this r...     

A 10-miRNA risk score-based prediction model for pathological complete response to neoadjuvant chemotherapy in hormone receptor-positive breast cancer

Patients with hormone receptor(HR)-positive tumors breast cancer usually experience a relatively low pathological complete response(p CR) to neoadjuvant chemotherapy(NAC). Here, we derived a 10-micro RNA risk score(10-mi RNA RS)-based model with better performance in the prediction of p CR and validated its relation with the disease-free survival(DFS) in 755 HRpositive breast cancer patients(273, 265, and 217 in the training, internal, and external validation sets, respectively). This model,pres...