Stress-free state of the red blood cell membrane and the deformation of its skeleton

The response of a red blood cell (RBC) to deformation depends on its membrane, a composite of a lipid bilayer and a skeleton, which is a closed, twodimensional network of spectrin tetramers as its bonds. The deformation of the skeleton and its lateral redistribution are studied in terms of the RBC resting state for a fixed geometry of the RBC, partially aspirated into a micropipette. The geometry of the RBC skeleton in its initial state is taken to be either two concentric circles, a references biconcave shape or a sphere. It is assumed that in its initial state the skeleton is distributed laterally in a homogeneous manner with its bonds either unstressed, presenting its stress-free state, or prestressed. The lateral distribution was calculated using a variational calculation. It was assumed that the spectrin tetramer bonds exhibit a linear elasticity. The results showed a significant effect of the initial skeleton geometry on its lateral distribution in the deformed state. The proposed model is used to analyze the measurements of skeleton extension ratios by the method of applying two modes of RBC micropipette aspiration.     

紫花凤梨的生物学习性

在南亚热带的广州对荷兰引进的紫花凤梨的生物学习性观察研究。考察了紫花凤梨的分芽发生与叶片生长;花序生长发育与开花;耐性、抗性表现等多个方面的生物学习性,并进行综合评价,并提出掌握和利用其习性的建议。     

蒙古扁桃种子萌发生理研究

探讨了蒙古扁桃种子萌发生理。实验结果表明 ,成熟的蒙古扁桃种子胚形态和生理发育完全 ,种皮含有萌发抑制物质。在 1 7°C下蒙古扁桃种子萌发率较高 ,光可以促进蒙古扁桃种子萌发。用 2 %PEG 60 0 0、0 .5 %NaHCO3 、0 .1 %NaCl、0 .2 %NaCl和 5 0 μg/mLNAA浸种处理均促进蒙古扁桃种子萌发 ,而 5 0 μg/mL 6 BA浸种处理对蒙古扁桃种子萌发有抑制作用。     

Zinc essentiality and toxicity. Biophysical aspects

The current concepts concerning zinc biology, its metabolism and transport into cells, its homeostasis, its role in the functioning of the human immune and endocrine systems, its participation in cell signaling, and its cytotoxicity, as well as the biophysical mechanisms of action of zinc ions at elevated concentrations on human blood cells are reviewed and analyzed.     

The postcranial dimensions of the La Chapelle-aux-saints 1 Neandertal

The La Chapelle-aux-Saints 1 Neandertal has figured prominently in considerations of Neandertal body size and proportions. In this context, a reassessment of its major long bones and a reassembly of its principal pelvic elements (sacrum and right ilium) was undertaken. There are secure measurements for its humeral and radial lengths and its femoral head diameter, but the femoral and tibial lengths were almost certainly greater than previous values. The resultant humeral, femoral and tibial lengths are similar to those of other male Neandertals, its femoral head diameter is among the largest known for Middle and Late Pleistocene humans, but its radial length is relatively short. The pelvic assembly provides modest bi-iliac and inlet transverse diameters compared with the few sufficiently complete and undistorted Middle and Late Pleistocene archaic human pelves, but its dimensions are similar to those of large male early modern humans.     

Structure and physiology of mammalian vas deferens in relation to fertility regulation

The structural and functional integrity of the vas deferens and its role in ensuring the fertilizing ability, viability of spermatozoa and their survival in the vas deferens, are elucidated. The regulation of the function of the vas deferens and the differential androgen dependency of its two regions have been discussed in relation to its secretory and absorptive activities as well as its contractility. The importance of ascorbic acid in maintaining its functions has also been investigated. The potentiality of the use of an androgen antagonist, steroids (testosterone, estradiol benzoate), prostaglandins, copper devices, vasectomy, vasocclusive agents, effects of nutr itional deficiencies, human chorionic gonadotropin-antiserum and plant products as antifertility agents have been discussed.     

Detection of HBs antigen by hemagglutination inhibition tests; experiment with standardization]

The standarization of a reagent for automated detection of HBs antigen by an inhibition of the hemagglutination reaction is described. Its advantages are its specificity, its fast efficiency, its low cost. But, its handling is delicate and requires a good technicity.     

世界麦双尾蚜研究进展：分布、

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has become a worldwide cereal pest with its dispersion to over 30 countries in this century. According to the natural history of its occurrence around the world, it is postulated RWA originated from western or central Asia. The aphid dispersed gradually to Europe and northern Africa, but its big jump across the ocean to North America is still a mystery. There are two overwintering strategies in RWA. The anholocyclic biotype, often reproducing earlier and more offsprings than the holocyclic one, has greater impact on crops in South Africa and United States. According to the experiments on its thermal response, RWA could withstand temperatures below -20℃, while temperatures above 30℃ would be harmful to its survival. The preference to colder condition may determine its distribution on the world. RWA has made great damages to cereal crops worldwide. It caused loss in crop yield by directly feeding on plant nutrition and disturbing the plant metabolism. But its status as plant virus transporter is open to question. By now, the aphid is still a serious pest in many countries and its invasion to more countries and areas maybe continues. Therefore, the research on its biological characteristics as well as its dispersion apparently needs to be enhanced in the future.     

Molecular Weight and Chemical-Modifications of the Gum from the Seeds of Sesbania cannabina (RETZ.) PERS

The water-soluble polysaccharide is isolated and purified from the seeds of Sesbania cannabina (Retz.) Pers. Its physiochemical properties are investigated. The purified preparation seems to be homogeneous after ultra-centrifugation. The sedimentation coefficient of the gum obtained from alcoholic purification is 4.71 S, its intrinsic viscosity is 5.93 dl/g and its molecular weight is estimated to be 391,000. When it is obtained from copper alcoholic purification, however, its sedimentation coefficient is 2.82 S, its intrinsic viscosity 2.44 dl/g and its molecular weight 206,000. Several derivatives of the gum have been prepared, including carboxymethylated gum, hydroxyethylated gum and carboxymethylhydroxyethylated gum.     

南瓜果肉色素的提取及稳定性的研究

本文研究了从南瓜果肉中提取色素的方法,并对它的光、热、酸、碱稳定性进行了研究,发现其性质较稳定,且原料来源广泛,提取工艺简单,着色效果好,是食品、医药、化妆品等领域的理想添加剂。     

Development and in vitro evaluation of thiolated chitosan--Poly(methacrylic acid) nanoparticles as a local mucoadhesive delivery system

The main objective of this study was to develop a local, oral mucoadhesive metronidazole benzoate (MET) delivery system that can be applied and removed by the patient for the treatment of periodontal diseases. The results of present study revealed that the retention time of MET at its absorption site could be increased by formulating it into nanoparticles using thiolated chitosan (TCS)-poly(methacrylic acid) (PMAA). The nanoparticles of MET prepared from TCS-PMAA may represent a useful approach for targeting its release at its site of absorption, sustaining its release and improving its oral availability.     

Phosphorylation Regulates the Ubiquitin-independent Degradation of Yeast Pah1 Phosphatidate Phosphatase by the 20S Proteasome

Saccharomyces cerevisiae Pah1 phosphatidate phosphatase, which catalyzes the conversion of phosphatidate to diacylglycerol for triacylglycerol synthesis and simultaneously controls phosphatidate levels for phospholipid synthesis, is subject to the proteasome-mediated degradation in the stationary phase of growth. In this study, we examined the mechanism for its degradation using purified Pah1 and isolated proteasomes. Pah1 expressed in S. cerevisiae or Escherichia coli was not degraded by the 26S proteasome, but by its catalytic 20S core particle, indicating that its degradation is ubiquitin-independent. The degradation of Pah1 by the 20S proteasome was dependent on time and proteasome concentration at the pH optimum of 7.0. The 20S proteasomal degradation was conserved for human lipin 1 phosphatidate phosphatase. The degradation analysis using Pah1 truncations and its fusion with GFP indicated that proteolysis initiates at the N- and C-terminal unfolded regions. The folded region of Pah1, in particular the haloacid dehalogenase-like domain containing the DIDGT catalytic sequence, was resistant to the proteasomal degradation. The structural change of Pah1, as reflected by electrophoretic mobility shift, occurs through its phosphorylation by Pho85-Pho80, and the phosphorylation sites are located within its N- and C-terminal unfolded regions. Phosphorylation of Pah1 by Pho85-Pho80 inhibited its degradation, extending its half-life by ∼2-fold. The dephosphorylation of endogenously phosphorylated Pah1 by the Nem1-Spo7 protein phosphatase, which is highly specific for the sites phosphorylated by Pho85-Pho80, stimulated the 20S proteasomal degradation and reduced its half-life by 2.6-fold. These results indicate that the proteolysis of Pah1 by the 20S proteasome is controlled by its phosphorylation state.     

Water? What's so special about it?

What is so special about water? Why does it have the properties it has, and how might these reasons be relevant to its apparent biological importance? By exploring the structure and dynamics of water, from the isolated molecule and its interactions, through its many crystalline phases and to its so-called anomalous liquid phase, some of its apparently unusual behaviour is rationalized. The way in which it interacts with some relatively simple interfaces is also discussed. As a result of this exploration, a checklist of possible molecular-level reasons for its biological importance is devised.     

The Delft School of Microbiology in historical perspective

The paper discusses the contributions made to the Delft School of Microbiology by its founding fathers, defines its contents and analyses its influence. The paper is concluded by a discussion of the significance of the Delft School for the future development of general microbiology.     

High-frequency P element loss in Drosophila is homolog dependent

P transposable elements in Drosophila melanogaster can undergo precise loss at a rate exceeding 13% per generation. The process is similar to gene conversion in its requirement for a homolog that is wild type at the insertion site and in its reduced frequency when pairing between the homologs is inhibited. However, it differs from classical gene conversion by its high frequency, its requirement for P transposase, its unidirectionality, and its occurrence in somatic and premeiotic cells. Our results suggest a model of P element transposition in which jumps occur by a "cut-and-paste" mechanism but are followed by double-strand gap repair to restore the P element at the donor site. The results also suggest a technique for site-directed mutagenesis in Drosophila.     

Cloning and expression in Escherichia coli of an extremely thermostable oligo-1,6-glucosidase gene from Bacillus thermoglucosidasius.

The gene for an extremely thermostable oligo-1,6-glucosidase (dextrin-6-alpha-D-glucanohydrolase; EC 3.2.1.10) of obligately thermophilic Bacillus thermoglucosidasius KP1006 was cloned within a 4.2-kilobase HindIII-PvuII fragment of DNA by using the plasmid pUC19 as a vector and Escherichia coli C600 as a host. The gene was transcribed, presumably from its own promoter, in E. coli. E. coli with the hybrid plasmid accumulated oligo-1,6-glucosidase mainly in the cytoplasm. The level of enzyme production was comparable to that observed for B. thermoglucosidasius. The enzyme coincided absolutely with the B. thermoglucosidasius enzyme in its molecular weight (60,000), in its electrophoretic behavior on denaturing and nondenaturing polyacrylamide gels, in the temperature dependency of its stability and activity, and in its antigenic determinants.     

Acetylcholinesterase: how is structure related to function?

In accordance with its biological role, termination of neurotransmission at cholinergic synapses by rapid hydrolysis of the neurotransmitter, acetylcholine, acetylcholinesterase is one of nature's most efficient enzymes. Solution of its three-dimensional structure revealed that its active site is located at the bottom of a deep and narrow gorge. Such an architecture was unanticipated in view of its high turnover number. The present review examines how the highly specialized structure of acetylcholinesterase, with its sequestered active site, contributes to its catalytic efficacy, and discusses how the traffic of substrate and products to and from the active site is controlled.