Sodium transport through the amiloride-sensitive Na-Mg pathway of hamster red cells

Previous work showed that in hamster red cells the amiloride-sensitive (AS) Na⁺ influx of 0.8 mmol/liter cells/hr is not mediated by Na-H exchange as in other red cells, but depends upon intracellular Mg²⁺ and can be increased by 40-fold by loading cells with Mg²⁺ to 10 mm. The purpose of this study was to verify the connection of AS Na⁺ influx with Na-dependent, amiloride-sensitive Mg²⁺ efflux and to utilize AS Na⁺ influx to explore that pathway.Determination of unidirectional influx of Na⁺ and net loss of Mg²⁺ in parallel sets of cells showed that activation by extracellular [Na⁺] follows a simple Michaelis-Menten relationship for both processes with a K _m of 105–107 mm and that activation of both processes is sigmoidally dependent upon cytoplasmic [Mg²⁺] with a [Mg²⁺]_0.5 of 2.1–2.3 mm and a Hill coefficient of 1.8. Comparison of V_max for both sets of experiments indicated a stoichiometry of 2 Na: l Mg. Amiloride inhibits Na⁺ influx and Mg²⁺ extrusion in parallel (K _i = 0.3 mm). Like Mg²⁺ extrusion, amiloride-sensitive Na⁺ influx shows an absolute requirement for cytoplasmic ATP and is increased by cell swelling. Hence, amiloride-sensitive Na⁺ influx in hamster red cells appears to be through the Na-Mg exchange pathway.There was no amiloride-sensitive Na⁺ efflux in hamster red cells loaded with Na⁺ and incubated with high [Mg²⁺] in the medium with or without external Na⁺, nor with ATP depletion. Hence, this is not a simple Na-Mg exchange carrier.     

RFLP mapping of partially sequenced leaf cDNA clones in maize

We report here the results of mapping a set of 92 leaf cDNA clones in maize. The ends of each of these cDNA clones have previously been partially sequenced, and the sequence comparison has revealed the putative function for 28 clones. It is expected that the RFLP map developed using these expressed sequence tags will be of great importance for future maize genome analysis, such as for PCR-based gene mapping or gene function identification.Contribution from the Missouri Agricultural Experiment Station. Journal Series N. 12,019.     

Rice Triosephosphate Isomerase Gene 5[prime] Sequence Directs [beta]-Glucuronidase Activity in Transgenic Tobacco but Requires an Intron for Expression in Rice

In rice (Oryza sativa L.), cytosolic triosephosphate isomerase (TPI) is encoded by a single gene. TPI catalyzes a vital step in glycolysis, and RNA blots showed that the tpi gene is expressed in all vegetative tissues (root, culm, and leaves) and in rice suspension cells. No effect of light on expression was detected, but submergence of rice seedlings resulted in elevated levels of TPI mRNA in roots and culms. The 2767-bp 5[prime] upstream sequence of the tpi gene was fused translationally with the [beta]-glucuronidase (gusA) gene, and the resulting construct, TPI-GUS, was found to express constitutive, high levels of GUS activity in transgenic tobacco (Nicotiana tabacum) plants. However, the same construct yielded no GUS activity in stably transformed rice plants, and RNA blots showed that no GUS mRNA could be detected even though stable integration of functional copies of the construct was confirmed by Southern blot and genomic polymerase chain reaction analyses. Transient assays using particle bombardment yielded high levels of GUS expression from the TPI-GUS construct in tobacco leaves, but essentially no expression in rice, barley, or maize leaves. When the first intron of the tpi gene was included in the construct (TPI-int1-GUS), transient GUS activity was routinely obtained in rice leaves, revealing that the first intron of the rice tpi gene is crucial for its expression in rice. TPI-int1-GUS also directed transient GUS expression in maize and barley leaves, but little or no activity was obtained from this construct in tobacco, tomato, or soybean leaves. These results with the rice tpi promoter are in accordance with mounting evidence that differences in gene expression exist between monocots and dicots.     

Transfection of the mouse ICAM-1 gene into murine neuroblastoma enhances susceptibility to lysis,reduces in vivo tumorigenicity and decreases ICAM-2-dependent killing

We determined the expression of intercellular adhesion molecules (ICAM) on neuro-2a cells in order to evaluate whether they were involved in cytolysis of murine neuroblastoma. Fluorescence-activated cell sorting analysis revealed that the control neomycin-resistance-genetransduced line (neuro-2a/LN) had poor expression of ICAM-1 (mean channel fluorescence, MCF=3.7). An ICAM-1-positive transfectant of neuro-2a (neuro-2a/ICAM-1⁺) (CMF=64.3) was generated to evaluate directly the role of this adhesion molecule in cytolysis. Neuro-2a/ICAM-1⁺ was more sensitive to LAK killing (69.7% at an effector-to-target ratio of 1001) compared to neuro-2a/LN (48.6%) (P<0.001). Blocking of neuro-2a/LN and neuro-2a/ICAM-1⁺ lysis with anti-ICAM-1 monoclonal antibodies (mAbs) did not account for all the LFA-1-dependent killing. These data indicate that even in neuro-2a/ICAM-1⁺ cells, other LFA-1 ligands participated in the effector-target interaction. Therefore, we examined these cell lines for ICAM-2 expression. Both neuro-2a/LN and neuro-2a/ICAM-1⁺ lines expressed ICAM-2 (MCF=16.4 and 16.5). ICAM-2 accounted for the majority of the LFA-1-dependent killing in the ICAM-1-negative target, neuro-2a/LN, while ICAM-1 played a primary role in the cytolysis of the ICAM-1⁺ transfectant. Inhibition of lysis in the presence of anti-ICAM-1 and ICAM-2 mAbs was comparable to that seen with the addition of anti-LFA-1 mAb, indicating that other LFA-1 ligands were not involved in this system. ICAM-1 expression was associated with decreased in vivo tumorigenicity; mice inoculated with neuro-2a/ICAM-1⁺ cells had a significantly longer survival compared to those receiving neuro-2a/LN cells (median survival time 35.5 versus 24.5 days) (P<0.001). It is important to note that ICAM-1 transfection of murine neuroblastoma did not alter its metastatic potential. We conclude that transfection of mouse neuroblastome with ICAM-1 increases its sensitivity to in vitro lysis and reduces its in vivo tumorgenicity. In ICAM-1-negative murine neuroblastoma cells, ICAM-2 plays a primary role in cell-mediated lysis.This work was supported in part by the Children's Cancer Research Fund, the Minnesota Medical Foundation, the Viking Children's Fund and NIH grants PO1-CA-21737, NO1-AI-85002. E. K. is a recipient of the Irvine McQuarrie Research Scholar Award and B. R. B. a recipient of the Edward Mallinkrodt Foundation Scholar Award     

高粱蚜灰色灾变长期预测模型

本文应用灰色系统灾变预测理论建立了吕梁地区高粱蚜发生量预测模型．     

百合离体生殖细胞骨架的扫描电镜观察

从百合的花粉管分离出来的生殖细胞,经表面活化剂Ｔｒｉｔｏｎ Ｘ－１００ 及核糖核酸酶、硫酸铵离析处理。离析后的细胞经临界点干燥,扫描电镜观察显示：在离体生殖细胞的胞质内有一个非常复杂的支架网络系统。这一网络系统有内外两层：外层（靠近细胞膜）网络结构紧密,纤维束粗长;内层（靠近核）网络结构疏松,纤维束短细。一些间接证据显示,这一支架网络系统可能为微管骨架     

刺果番荔枝中的番荔枝内酯

从刺果番荔枝（Ａｎｎｏｎａ ｍ ｕｒｉｃａｔａ Ｌ．）的种子中分离到３ 个单四氢呋喃型番荔枝内酯类化合物,用波谱方法鉴定为海南哥纳香甲素（ｈｏｗ ｉｉｃｉｎ Ａ, Ｓ１３）、乙素（ｈｏｗ ｉｉｃｉｎ Ｂ, Ｓ５）和新化合物４－去氧海南哥纳香乙素（４－ｄｅｓｏｘｙｈｏｗ ｉｉｃｉｎ Ｂ, Ｓ２）。     

Zn2＋参与遗传调控的研究进展

Zn^2＋在遗传调控中的作用十分广泛而显著.结合新近的研究资料,着重从染色质结构与功能、核酸的生物合成、DNA的结构及构象、基因表达的调控等四个主要方面来反映Zn^2＋与遗传调控的相关性,并阐述Zn^2＋在其中发挥作用的机理.     

蜜蜂脑中5—HT，GABA，Ach免疫反应阳性神经元分布的比较研究

通过免疫细胞化学方法－ＰＡＰ法,研究了中华峰（Ａｐｉｓｓｉｎｅｎｓｉｓ）和意大利峰（ＡｐｉｓｍｅｌｌｉｆｅｒａＬ）脑和视叶中乙酰胆碱（Ａｃｈ）、５－羟色胺（５－ＨＴ）、γ－氨基丁酸（ＧＡＢＡ）免疫反应阳性神经元胞体和纤维的形态、染色强度、分布和各种神经丛之间的联系．一方面将这些阳性分布系统和蜜蜂脑中相应的神经元类型进行比较,另一方面也分析了在一些特殊解剖学通路中存在的可能的神经递质及其作用．     

ALTERNATIVE HOSTS OF TRICHOGRAMMA DENDROLIMI MATSUMURA IN DIFFERENT HABITATS (HYMENOPTERA: TRICHOGRAMMATIDAE)

Abstract  This paper deals with alternative hosts of an egg parasitoid. Trichogramma dendrolimi Matsumura in three habitats: mixed forest, pure stand and sparse wood. The experiment was conducted in Liuyan County which is located in the eastern part of Hunan Province. The results suggested that there are 103 species of alternative Lepidopteran hosts for T. dendrolimi . There were two critical periods throughout the year when there were no eggs of Dendrolimus punctatus Walker and few eggs of alternative hosts available for ovipsition by the parasitoids.