Inhibition of sperm-egg interaction by specific antibody

Treatment of hamster ova, in vitro, with ovary specific antibody interferes with sperm-egg interaction by inhibiting sperm attachment to the zona pellucida and subsequent zona penetration. This inhibition results from precipitation of the zona by the specific antibody.     

Penetration of somatic mammalian cells by sperm

Penetration of somatic mammalian cells by spermatozoa occurred after simple admixture in culture. With sperm labeled in vivo, autoradiography revealed incorporation of DNA into nuclei of recipient cells, indicating release of DNA after entrance by sperm. This system provides a new approach to study the molecular biology of information transfer and of haploid gene expression.     

An in vitro system for adhesion and fusion of maize gametes

The development of in vitro fertilization systems in flowering plants is important for understanding and controlling the mechanisms of fertilization. Here a method is described in which isolated maize gametes fuse. In a medium containing 5 mM calcium chloride, sperm and egg cells adhere for several minutes and then fuse within 10 seconds. The method is specific to male-female gamete pairs and results in 80 percent fusion, whereas fusions with other combinations of gametic and mesophyllic cells are less frequent. Eggs fertilized in vitro do not fuse with additional male gametes, which suggests that a block to polyspermy exists.     

Molecular mechanisms and forces involved in the adhesion and fusion of amphiphilic bilayers

The surface forces apparatus technique was used for measuring the adhesion, deformation, and fusion of bilayers supported on mica surfaces in aqueous solutions. The most important force leading to the direct fusion of bilayers is the hydrophobic interaction, although the occurrence of fusion is not simply related to the force law between bilayers. Bilayers do not need to "overcome" some repulsive force barrier, such as hydration, before they can fuse. Instead, once bilayer surfaces come within about 1 nanometer of each other, local deformations and molecular rearrangements allow them to "bypass" these forces.     

Mitochondrial fission, fusion, and stress

Mitochondrial fission and fusion play critical roles in maintaining functional mitochondria when cells experience metabolic or environmental stresses. Fusion helps mitigate stress by mixing the contents of partially damaged mitochondria as a form of complementation. Fission is needed to create new mitochondria, but it also contributes to quality control by enabling the removal of damaged mitochondria and can facilitate apoptosis during high levels of cellular stress. Disruptions in these processes affect normal development, and they have been implicated in neurodegenerative diseases, such as Parkinson's.     

Mitochondrial DNA mutations, oxidative stress, and apoptosis in mammalian aging

Mutations in mitochondrial DNA (mtDNA) accumulate in tissues of mammalian species and have been hypothesized to contribute to aging. We show that mice expressing a proofreading-deficient version of the mitochondrial DNA polymerase g (POLG) accumulate mtDNA mutations and display features of accelerated aging. Accumulation of mtDNA mutations was not associated with increased markers of oxidative stress or a defect in cellular proliferation, but was correlated with the induction of apoptotic markers, particularly in tissues characterized by rapid cellular turnover. The levels of apoptotic markers were also found to increase during aging in normal mice. Thus, accumulation of mtDNA mutations that promote apoptosis may be a central mechanism driving mammalian aging.     

Atomistic mechanisms and dynamics of adhesion, nanoindentation, and fracture

Molecular dynamics simulations and atomic force microscopy are used to investigate the atomistic mechanisms of adhesion, contact formation, nanoindentation, separation, and fracture that occur when a nickel tip interacts with a gold surface. The theoretically predicted and experimentally measured hysteresis in the force versus tip-to-sample distance relationship, found upon approach and subsequent separation of the tip from the sample, is related to inelastic deformation of the sample surface characterized by adhesion of gold atoms to the nickel tip and formation of a connective neck of atoms. At small tipsample distances, mechanical instability causes the tip and surface to jump-to-contact, which in turn leads to adhesion-induced wetting of the nickel tip by gold atoms. Subsequent indentation of the substrate results in the onset of plastic deformation of the gold surface. The atomic-scale mechanisms underlying the formation and elongation of a connective neck, which forms upon separation, consist of structural transformations involving elastic and yielding stages.     

Centric fusion, satellite DNA, and DNA polarity in mouse chromosomes

A fluorescent staining technique has demonstrated a contralateral arrangement of fluorescent spots in the centromeric region of mouse metacentric chromosomes which have resulted from centric fusion. The results suggest that centric fusion involves the maintenance of DNA polaritv through the centromere and that the thymidine-rich chain of satellite DNA in the centromeric region is associated with the same DNA chain in every mouse autosome.     

New method for manipulation,maintenance, and cloning of single mammalian cells in vitro

Individual mammalian cells can be isolated with the aid of easily handled glass beads to which the cells have become attached. Procedures for the preparation of cell cultures on beads, and for the recognition and manipulation of beads carrying single monocytes, HeLa cells, and Detroit-98 cells are described. Data obtained with Brucella infected monocytes, illustrating the efficiency of the method, are presented.     

Energetics, patterns of interaction strengths, and stability in real ecosystems

Ecologists have long been studying stability in ecosystems by looking at the structuring and the strengths of trophic interactions in community food webs. In a series of real food webs from native and agricultural soils, the strengths of the interactions were found to be patterned in a way that is important to ecosystem stability. The patterning consisted of the simultaneous occurrence of strong "top down" effects at lower trophic levels and strong "bottom up" effects at higher trophic levels. As the patterning resulted directly from the energetic organization of the food webs, the results show that energetics and community structure govern ecosystem stability by imposing stabilizing patterns of interaction strengths.     

哺乳动物卵巢中的细胞凋亡及其调节

细胞凋亡是近几年细胞生物学研究的热点。卵巢中发生的生殖细胞减少、卵泡闭琐和黄体退化都与细胞凋亡密切相关。就上述三个过程中的细胞凋亡进行了概述 ,并简要介绍了新近发现的几种因素对卵巢细胞凋亡的调节。     

Contracture and catecholamines in mammalian myocardium

Contractures induced by KCl are produced in cat ventricular muscle after depletion of catecholamine stores by previous treatment with reserpine or by selective blocking of adrenergic receptor sites with propranalol. Contractures are reproducible for 2 to 3 hours and are markedly depressed by the addition of epinephrine. The relaxation of contracture induced by epinephrine parallels the eftect of this compound of shortening the duration of the normal twitch. The failure of the normal mammalian myocardium to maintain tension in solutions of high KCI concentration appears to be related to the endogenous amounts of catecholamines in the tissue.     

三氯乙酸在黄土中的渗透机理研究

【目的】研究三氯乙酸（TCA）与黄土化学作用对其渗透性能的影响机理,为防止TCA渗流对地下水的污染提供参考。【方法】以杨凌黄土为研究对象,采用压汞试验,测定不同质量分数TCA溶液（0%（纯水）,2%和8%）污染黄土孔隙分布密度、孔隙率和平均孔径的变化;采用土柱渗透试验,测定不同质量分数TCA溶液对黄土渗透特性和水分运移的影响;通过浑浊度试验、X射线衍射试验和扫描电镜观察,从上覆溶液的浊度演化、黄土胶结的腐蚀程度和表层颗粒的结构形态等角度对TCA在黄土中的渗透规律进行分析。【结果】当TCA质量分数由0%增加到8%时,TCA污染土中孔径0.1~1.0 μm孔隙的分布密度减小,孔隙率由25.2%上升至40.4%,平均孔径由0.28 μm升至0.34 μm,TCA对黄土同时表现出团聚性和腐蚀性。2% TCA溶液有利于黄土表层颗粒团聚,间接扩大渗流路径,使上覆溶液可以快速入渗,其在土柱中的渗流耗时是纯水的70%,有效增大了黄土的渗透性。8% TCA溶液破坏了黄土的胶结结构,使黄土表层的团聚颗粒分散为悬浮颗粒,悬浮颗粒的沉降和浊流入渗堵塞了渗流路径,从而在土壤表层形成了1~3 cm厚的不透水层,土颗粒之间生成的针状和片状氯化物结晶进一步堵塞孔隙并降低了溶液的入渗速率,其在土柱中的渗流耗时是纯水的3.6倍,明显降低了黄土渗透性。【结论】质量分数2%和8% TCA溶液对黄土渗透性影响不同,TCA污染的预防和治理需考虑TCA团聚、腐蚀行为对黄土渗透性的影响。     

论杀虫剂穿透生物学与昆虫抗药性测定

本文阐明了杀虫剂穿透生物学的基本概念及其对昆虫抗药性测定的指导意义,论述了杀虫剂穿透生物学提出的背景及其与田间毒理学的关系,分析了在昆虫抗药性测定中存在的问题及其主要原因;提出了杀虫剂穿透生物学在昆虫抗药性测定中的应用原则。     

Estrogenic activity of o,p'-DDT in the mammalian uterus and avian oviduct

When rats and birds were treated with o, p-DDT, their reproductive tissues exhibited the same response as when they were treated with estrogen. Weight, water content, glycogen, and RNA increased in uteri and oviducts of rats, chickens, and quail receiving o, p-DDT; p, p-DDT produced little if any response. The o, p-DDT did not accumulate in the reproductive or adipose tissues to a greater extent than p, p-DDT.     

Carbonic anhydrase interaction with DDT, DDE, and dieldrin

The active site of various carbonic anhydrases is not blocked by DDT. DDE, or dieldrin. Impairment of catalytic efficiency can only be documented in opalescent test solutions in which the insecticides are present in excess of their solubility limit. These slowly forming precipitates occlude enzyme from solution and furnish a physical explanation of the supposed inhibition. The amounts occluded depend, among other things, on the conformational and topographical characteristics of the particular carbonic anhydrase molecules.     

Teratocarcinomas and mammalian embryogenesis

In the last decade there has emerged an appreciation of the remarkable similarity between the cells that give rise to teratocarcinomas in mice and the cells that give rise to the developing mouse embryo. The resemblance is so close that in certain instances the tumor stem cells can join with their embryonic counterparts and develop into a completely normal mouse. The availability of stem cell lines isolated from mouse teratocarcinomas has made possible a number of new biochemical, immunological, and genetic approahes to the study of early mammalian development.     

基因工程教学中人文精神的渗透

大学生除了需要有丰富的专业知识外,还需要有较广阔的人文视野及较厚重的人文素养。但当代大学生人文精神严重缺失,特别是一些理工科学生。在专业课程教学过程中渗透人文精神,是对大学生进行人文素质教育的有效途径。文章结合教学实践阐述了基因工程教学中培养人文精神的必要性及渗透人文精神的途径:提高教师人文素养;利用基因工程相关公众事件、科幻电影等素材激发学生社会道德责任感;深挖教学内容,唤醒学生关爱生命,以人为本的情怀;通过科学史实和科学家的故事,搭建人文精神与科学精神的桥梁。     

对外汉语教学中的文化渗透

语言与文化有着密不可分的关系.汉语作为一种语言,既反映了中华民族文化的基础和精髓,也对中华民族文化的形成与发展产生深远的影响.作为对外汉语教师应该将语言技能训练和中国文化教育有机结合起来,将文化教育很好的渗透到语言教学当中,达到最佳的教学效果.本文拟从对外汉语教学中的汉字教学、词汇教学、语法教学等环节入手,探讨如何将文化教学更好的渗透到语言教学当中.