The structure and cytochemistry of the pistil of Hypericum calycinum: the style

Summary A typical style of Hypericum calycinum is solid with a core of transmitting tissue traversing the whole length of the style. This transmitting tissue consists of loosely arranged cells and large intercellular spaces filled with a secretion product. The secretion product is rich in lipids, but poor in proteins and polysaccharides. The intercellular spaces of the transmitting tissue originate partly by a separation of cells as a result of the decomposition of the middle lamella and partly by degeneration of some of the cells of the transmitting tissue. H. calycinum is self-compatible. Both self- and cross-pollinations result in profuse pollen germination on the stigma and pollen tube growth through the style. The data on Hypericum is discussed in relation to information available on other solidstyled systems.     

Endogenous cholesterol synthesis is sufficient for ACTH-induced differentiation of rat adrenocortical cells in primary culture

Summary To define the role of endogenously synthesized cholesterol in the differentiation of adrenocortical cells in primary culture, fetal rat adrenal cells were cultured in the presence of exogenous cholesterol (serum-supplemented medium) or in the absence of it (serum-free medium or lipoprotein-free medium). Ultrastructurally the cells had features of glomerulosa cells: mitochondria were oval or rod shaped with lamellar inner membranes. The amount of smooth endoplasmic reticulum was small, and lipid droplets were few. When the cells were cultured in serum-free medium some intracytoplasmic vacuoles were seen. The undifferentiated zona glomerulosa-like cells secreted low amounts of corticosterone and 18-OH-deoxycorticosterone (18-OH-DOC) in all three media (serum-supplemented medium, serum-free medium, and lipoprotein-free medium). Stimulation of the adrenocortical cells with ACTH induced the ultrastructural features of differentiated zona fasciculata-like cells. Mitochondrial inner membranes were well developed in lipoprotein-free medium, but not in serum-free medium. The amount of intracellular lipids was increased in both media devoid of cholesterol. In the ACTH stimulated cultures the presence of exogenous cholesterol resulted in increased secretions of corticosterone and 18-OH-DOC. In the absence of an exogenous source of cholesterol, the amounts of steroids secreted were only half of that secreted in the presence of serum-supplemented medium. Endogenously synthesized cholesterol is sufficient for the morphologic differentiation of fetal rat adrenocortical cells under ACTH stimulation. However, without exogenously provided cholesterol, the steroid production accounts only for half of the maximal output achieved using serum-supplemented medium. This work was supported by Finnish Culture Foundation.     

A computerized mechanical cell stimulator for tissue culture: Effects on skeletal muscle organogenesis

Summary A tissue culture system has been developed which can mechanically stimulate cells growing on a highly elastic plastic substratum in a 24-well cell growth chamber. The collagen-coated substratum to which the cells attach and grow in the Mechanical Cell Stimulator (Model I) can be repetitively stretched and relaxed by stepper motor with linear accuracy of 30 μm. The activity controlling unit is an Apple IIe computer interfaced with the cell growth chamber via optical data links and is capable of simulating many of the mechanical activity patterns that cells are subjected to in vivo. Primary avian skeletal myoblasts proliferate and fuse into multinucleated myotubes in this set-up in a manner similar to normal tissue culture dishes. Under static culture conditions, the muscle cells differentiate into networks of myotubes which show little orientation. Growing the proliferating muscle cells on a unidirectional stretching substratum causes the developing myotubes to orient parallel to the direction of movement. In contrast, growing the cells on a substratum undergoing continuous stretch-relaxation cycling orients the developing myotubes perpendicular to the direction of movement. Neither type of mechanical activity significantly affects the rate of cell proliferation of the rate of myoblast fusion into myotubes. These results indicate that during in vivo skeletal muscle organogenesis, when substantial mechanical stresses are placed on skeletal muscle cells by both continuous bone elongation and by spontaneous contractions, only bone elongation plays a significant role in proper fiber orientation for subsequent functional work. Supported by grants NS16753, AR36266, and RR05818 from the National Institutes of Health, Bethesda, MD.     

Analysis of the biomacromolecular architecture of eukaryotic and prokaryotic serine proteases

Summary We have been developing computational approaches to increase our ability to analyze the growing body of three-dimensional structural data with applications centered on the serine proteases and their natural inhibitors and substrates. It is essential that these approaches emphasize the comparison of these macromolecules at the separate levels of secondary, tertiary and quaternary structure. We assume in our analysis that in functionally related macromolecules (i.e., a family of evolutionarily related enzymes), regions of structural and/or physicochemical similarity will exhibit functional similarity; regions that are different in structure and/or physicochemical properties will function differently and, therefore, be the source of observed specificity. It is the intent of our research to encapsulate such knowledge in a form which is capable of observing patterns which may serve as generalizable rules for macrostructural analysis (Liebman, M.N. 1986. Enzyme 36: 150–163), and to serve as the essential tools for the rational design of modified serine proteases and/or their natural inhibitors by the methods available through genetic engineering.     

应用电子探针对植物根际和根内营养元素微区分布的探讨

用电子探针可检测出玉米、大豆根际和根内含有Na,Mg,Al,Si,P,S,Cl,K,Ca,Ti,Fe,Cu和Zn 13种元素。这些元素在根际土壤、粘液层和根组织内的含量分布有一定的规律性。除Si,Al,Ca,Fe在根际土壤中峰值较高外,Ti仅在土壤中达到可检测量;S,Fe和Zn富集在粘液层,Mg,P,Cl只在根组织内才有较明显的峰。这些规律可作为区分根—土界面的参考指标。K含量在根内明显高于根际土壤,并由表皮层到中柱径向增加;Ca则与K不同,且受植物种类的影响。     

Preservation of the diffusible cations for secondary ion mass spectrometry. II. Artefacts in material embedded in araldite or melamine.

Flotation on hot water (about 60 degrees C) which is frequently employed to stretch semithin sections on substrates for SIMS (secondary ion mass spectrometry) microscopy, is the cause of numerous artefacts. In the case of epoxy resin-embedded tissue, one observes loss of potassium and sodium and accumulation of calcium. The relative contrast of cell nuclei in the ionic images, is rapidly affected by these ion migrations. After prolonged contact with hot water, tissue becomes uniformly emissive. In the case of hydrosoluble resin-embedded tissue, potassium and sodium do not appear to be affected by the action of water, which suggests that they are covalently bound with chelating sites buried beneath the layer of water bound to the surface of the macromolecules. Calcium accumulates, probably on widely exposed anionic sites. Moreover, the domains observed in hydrosoluble resin-embedded tissue shrink differently according to the proportion of water removed by melamine; this can provide interesting information on the initial equilibrium between water, ion sand macromolecules. Our results seem to support the assumption that bound water should play an important role in the preservation of both macromolecular architecture and ion distributions.     

猴脑线粒体DNA提取及限制性内切酶分析

本文用冷碱法从2只恒河猴和1只食蟹猴的脑组织中提取mtDNA,最后的得率大约为0.7μgmtDNA/g脑组织,是肝脏组织得率的1/3左右。与肝脏组织相比较,从脑组织中提取mtDNA有以下优点:1.匀浆方便。2.样品中蛋白杂质少,容易彻底抽提去除蛋白质。3.大分子RNA杂质极少,不经Sepharose-4B柱或RNawe处理,就可得到较纯的样品。加之哺乳动物脑的体积较大,哺乳动物脑组织不失为提取mtDNA的一个有用的组织来源。经16种限制性内切酶分析,并与来自同一个体肝脏组织的mtDNA比较,结果进一步证实,mtDNA无组织特异性。对12岁以上老年猴脑mtDNA的分析表明,在衰老中,动物mtDNA的序列可能没有变化,甲基化程度也无显著增高。     

Low incidence of bronchus-associated lymphoid tissue (BALT) in chronically inflamed human lungs

The relevance of bronchus-associated lymphoid tissue (BALT) in man is still under discussion. Animal experiments indicate that the development of BALT is dependent on microbial stimulation. Therefore, the incidence of BALT was investigated retrospectively in specimens removed during surgical procedures on patients with chronic pulmonary inflammation. All these patients had severe chronic bronchitis and bronchiectasis, but BALT was found in only 8%. In patients with BALT and a malignant tumor, occlusion of a bronchus with poststenotic pneumonia was always present and BALT was observed exclusively in areas peripheral to the occlusion. In man other compartments of the lung must be responsible for the immune function of BALT found in animals. Partly presented at the Congress of the Eur. Respir. Soc, 21.- 26.9.1991 in Brussels. (Abstract: Eur Respir J. 4, Suppl. 14:217p)     

马铃薯Y病毒外壳蛋白基因的克隆及序列分析

本文报道应用聚合酶链式反应(PCR)技术,在体外扩增马铃薯 Y 病毒外壳蛋白基因及其克隆和序列分析的结果。病毒 RNA 从马铃薯 Y 病毒感染的烟草叶片中提取,用合成的PCR 3引物及 AMV 逆转录酶合成了单链的 cDNA。利用 PCR 技术,经30个循玎的扩增。得到了一特异的0.8kb 片段。克隆后对此片段进行了限制性内切酶物理图谱分析,并测定了其全序列。实验结果证明,我们克隆到的是完整的马铃薯 Y 病毒的外壳蛋白基因。与国外报道的马铃薯 Y 病毒 N 株相比,其核苷酸序列及推测的氨基酸序列的同源率分别为97.8%和97%。将该基因导入马铃薯以期获得抗 Y 病毒马铃薯的工作正在进行。本文还对 PCR 技术用于扩增植物 RNA 病毒的方法以及用基因工程方法培育抗病毒作物新品种的可行性等进行了讨论。