植物硫转运蛋白研究进展

硫转运蛋白在植物对硫酸盐的吸收和转运中起着重要的作用。已经在拟南芥、大麦和小麦等植物中分离到了40多种硫转运蛋白基因。这些基因序列与其他种类生物的硫转运蛋白基因序列有着高度的保守性。利用CLUSTAL程序建立的系统进化树将植物硫转运蛋白划分为5个亚群。使用多种拓扑预测程序推测出不同植物硫转运蛋白的共同结构特点是均含有12个跨膜域。在柱花草和大麦中,硫转运蛋白基因表达调控包括植物体内硫水平的负调控和O—乙酰丝氨酸的正调控两种方式。对硫转运蛋白的组织定位和功能研究表明,高亲和硫转运蛋白主要定位于根部,在根系硫酸盐吸收中起重要作用。     

The place of metabolism in the origin of life

Metabolism and replication are generally considered essential features of biological life. Workers in the field of the origin of life are mostly split into two groups, depending on which of these two functions is postulated to have occurred first. Because of difficulties encountered by the replication-first (or genetics-first) approach, some workers have postulated that a highly developed metabolism must have originated before replication and the formation of a genetic apparatus. However, as supporters of a replication-first approach have pointed out, and as is discussed in this article, the alternative metabolism-first approach has fundamental problems that have not been sufficiently addressed.     

Phylogenetic analysis of the distribution of chromosomal races of Mus mnscuius domesticus Rutty in Europe

Robertsonian (Rb) translocation is a common chromosomal rearrangement in the house mouse. In free-living populations, 79 fusions with different combinations of chromosomes 1 to 18 have been found in some 45 populations. An updated list of these fusions is presented and analysed in order to reveal the possible processes by which the fusions spread within or among populations. A widespread hypothesis is that when two populations share the same fusion, it can be assumed that they have a common ancestor. This can serve as the basis for the use of the cladistic methods. While I present such an analysis on the updated list of Rbs, I also point to the problems associated with it in this case because many fusions have multiple origins and exchanges of Rbs between populations are frequent. I have tried to use a different approach, based on a critical and quantitative evaluation of the hypothesis of common ancestry. Assuming that the 153 possible fusions have an equal probability of occurrence, I give the formula to compute the probability that populations share a given number of fusions by chance alone. Only when this probability is lower than a chosen level (say 5%) can the populations be inferred to have a non-independent origin (i.e. they have a common ancestor or they have exchanged chromosomes by introgression). This probability measure is then used as a distance estimate to show the relationship between all the Rb populations. This analysis suggests that although some Rbs must have occurred more than once, most of the populations have non-independent origins. Almost all the populations from northern Africa to Belgium and Germany appear to have close karyotopic relationships and form a major group. Clearly independent Rb populations are mainly found in the periphery of this major group, for example in Scotland, Denmark and Spain. 'Chromosomal' flow between Rb populations appears to be a very important process.     

几种鳞毛蕨科药用蕨类植物的抑菌特性分析

研究了6种鳞毛蕨科药用蕨类植物的不同浸提液对几种常见微生物生长的影响情况,结果表明它们普遍表现了很好的抑菌效果,其中对金黄色葡萄球菌(Staphylococcus aureus)的抑制效果最好,最大的抑菌率达到90.4%;通过对鳞毛蕨科3个属的抑菌作用比较,耳蕨属(Polystichum)的普遍抑菌作用占优势;从浸提方法上看,醇提取的方法并不比水提取的方法有明显的优势.     

Pharmacology of azoles

Azole antifungals have different pharmacokinetic characteristics: complete oral absorption for Voriconazole, and to a lesser extent for fluconazole. The absorption of posaconazole and itraconazole increases with food intake. All of them have high tissue distribution with low plasma concentrations, especially low in the case of posaconazole and itraconazole. Posaconazole and itraconazole have high plasmatic protein binding and consequently both have a very low free fraction. Elimination of azole antifungals is through a metabolic pathway with CYP450 isoenzymes, and has a non linear pharmacokinetics with a high risk of interation with other drugs since azoles have the ability of CYP450 isoenzymes inhibition. Possibly the parameter that defines more precisely their efficacy is AUIC with an optimum value near 20, although cut-off values must be defined since some azoles may have difficulty to reach this value.     

Development of a gas chromatography mass spectrometry assay for the two eosinophil chemotactic factors of anaphylaxis

Gas chromatography mass spectrometry has been used for over a decade for the determination of the amino acid sequences of fragment peptides derived from larger parent molecules. The majority of these fragments have from four to seven residues and several different methods of derivatization have been devised. Few reports have been published in which similar techniques have been used for the quantification of such peptides, but there is a growing list of small peptides which have been shown to have biological activity in their own right. This report is concerned with the development of a gas chromatographic mass spectrometric assay for the two eosinophil chemotactic peptides, Val-Gly-Ser-Glu and Ala-Gly-Ser-Glu, which appear to have a role to play in the course of the inflammatory process in skin disorders.     

Host defense mechanisms of cephalopods

Humoral and cellular mechanisms of defense have been described for cephalopods, a relatively advanced group of mollusks. Typical of other mollusks, cephalopod agglutinins are the most documented component of humoral immunity. Lectins, which have agglutinating properties, have been described and characterized from octopuses. Agglutinins from cephalopod hemolymph have also been shown to agglutinate a variety of vertebrate red blood cells, as well as potential bacterial pathogens. Hemocytes are the primary component of cellular immunity. Although the hemocyte role in phagocytosis has been extensively studied in other mollusks, the mechanisms of phagocytosis have not been described extensively for cephalopods. Cephalopod hemocytes have phagocytic capabilities and may function in encapsulation and neutralization of foreign substances; however, the effects of environmental factors and the full extent of phagocytic capabilities of cephalopod hemocytes have not been reported. Hemocytes from cephalopods have a role in wound healing and inflammation which have been reported in detail by several investigators.     

Biomass estimation of orange roughy: a summary and evaluation of techniques for measuring stock size of a deep-water fish species in New Zealand

A number of techniques have been employed to measure biomass of orange roughy in New Zealand. Time series of stratified random trawl surveys in a number of areas over periods of 5–10 years have given relative abundance indices, which have been used in stock reduction analyses to estimate true biomass. This has given confident results for the Chatham Rise stock, and surveys have also shown strong trends in other regions. Acoustic surveys have been carried out on three grounds. They can give relative indices of orange roughy abundance in areas of fiat or medium sloping bottom, and have the potential for estimation of absolute biomass from a single survey. Egg production surveys have been employed on two grounds on the east coast of the North Island, where conditions of tight spawning aggregations and steep bottom topography have limited the success of other methods. Both daily fecundity reduction and annual egg production methods have been used. These have given estimates of true biomass from one-off surveys, although results are imprecise. Both unstandardized and standardized analyses of commercial catch-per-unit-effort data have given relative indices of abundance, which have formed an important part of stock assessment for several fisheries. No single technique used to measure the size of orange roughy stocks has proven ideal or appropriate in all New Zealand situations. All have advantages and disadvantages, depending on the characteristics of the fishing area and fish behaviour. For two areas, a combination of methods have been applied, which has given more confident results than those from a single technique.     

Bacteriophages of spirochetes

Historically, a number of bacteriophage-like particles have been observed in association with members of the bacterial order Spirochetales, the spirochetes. In the last decade, several spirochete bacteriophages have been isolated and characterized at the molecular level. We have recently characterized a bacteriophage of the Lyme disease agent, Borrelia burgdorferi, which we have designated phiBB-1. Here we review the history of the association between the spirochetes and their bacteriophages, with a particular emphasis on phiBB-1 and its prophage, the 32-kb circular plasmid family of B. burgdorferi.     

Histologic organization of the myocardium of the rat during hypokinesia (stereologic study)

For 30 days Wistar rats have been kept under conditions of hypokinesia. Using stereological methods, the volume and surface density of muscle fibers, microcirculatory bed and connective tissue components have been defined, and volumetric and surface--volume ratios of parenchymal and stromal structures have been calculated. Intracellular stereological parameters of the cardiac myocytes have been studied. Three-dimensional parameters in the parenchymatous-stromal interrelations of the atrophying myocardium accompanied with a deep rearrangement of the intracellular architectonics have been determined, as well as certain destructive changes of the cardiac myocyte ultrastructures. Such a treatment as a decreased functional loading is demonstrated to be the cause of cardiomyocytic lesions.     

Antibacterial activity of ZnO nanoparticle suspensions on a broad spectrum of microorganisms

Nanoparticle metal oxides represent a new class of important materials that are increasingly being developed for use in research and health-related applications. Highly ionic metal oxides are interesting not only for their wide variety of physical and chemical properties but also for their antibacterial activity. Although the in vitro antibacterial activity and efficacy of regular zinc oxides have been investigated, little is known about the antibacterial activity of nanoparticles of ZnO. Preliminary growth analysis data suggest that nanoparticles of ZnO have significantly higher antibacterial effects on Staphylococcus aureus than do five other metal oxide nanoparticles. In addition, studies have clearly demonstrated that ZnO nanoparticles have a wide range of antibacterial effects on a number of other microorganisms. The antibacterial activity of ZnO may be dependent on the size and the presence of normal visible light. The data suggest that ZnO nanoparticles have a potential application as a bacteriostatic agent in visible light and may have future applications in the development of derivative agents to control the spread and infection of a variety of bacterial strains.     

The Use of PC12 Cells for the Study of the Mechanism of Action of Neurotrophic Factors: Signal Transduction and Programmed Cell Death

The PC12 cell line is one of the most widely used of all neuronal cell lines. Over 2200 studies using PC12 cells have been published since the first in 1974. It is so widely used because it possesses properties that make it applicable to a wide variety of neurobiological problems. This article is a brief overview of some neurobiological issues that have been approached in recent years using the PC12 cell line and the properties of PC12 cells that have allowed their application to these problems. The intent is to provide an idea of the versatility of this line and of the types of studies that have successfully employed it. This may suggest potential approaches to solving problems in the readers own research. A major focus of this article is on the use of PC12 cells as a model for the study of neurotrophic factor signal transduction. PC12 cells have proved to be a particularly valuable model for this purpose and a significant fraction of studies using PC12 cells, particularly recent studies, have been directed toward this end.     

Cryopreservation of islets of Langerhans

Development of techniques for cryopreservation of pancreatic islets of Langerhans could potentially allow for increased freedom from the time restrictions presently affecting viability in islet cell transplantation. While several investigators have attempted islet cell freezing and have obtained favorable in vitro results after thawing, there have been few reported in vivo successes with islets transplanted after freezing. We have developed a simple system for freezing islet cell pancreatic fragments to ?196 °C and have either stored them in liquid nitrogen for 24 hr or immediately thawed the islets prior to transplantation. In addition, antilymphoblast globulin has been used as graft pretreatment modality in order to modify islet cell immunogenicity. We found that ALG was effective in prolongation of graft survival after freezing as well as on fresh nonfrozen transplants. The use of freezing and ALG appears, therefore, to have a favorable effect on the immunogenicity of the pancreatic islet cell allograft.     

Chance and the origin of life

Random chemical reactions in the Earth's primitive hydrosphere could have generated no more than 200 bits of information, whereas the first Darwinian organism must have encoded about a million bits, and therefore could not have arisen by chance. This information gap is bridged by separating reproduction from organism, and postulating a reproductive chemical community that would generate information by proto-Darwinian evolution. The information content of the initial community could have been as low as 160 bits, and its evolution might have led to the first Darwinian cell.     

Core-coat conductor of lipid bilayer and micromachined silicon

We have etched a groove into a (110) plane of silicon and have covered it with a bilayer of glycerol monooleate. We have varied the depth of the groove, the concentration of salt in the electrolyte and the density of gramicidin in the membrane. We have clamped one end of the groove at a constant voltage with respect to the bath keeping the other end sealed or electrically open with respect to the bath. We have measured (i) the voltage at the center of the groove and at the sealed distal end and (ii) the current through the system in sealed and open configuration. We have found that the spread of voltage is in quantitative agreement with the stationary solutions of Kelvin's equation for a homogeneous cable.     

Genome evolution of allopolyploids: a process of cytological and genetic diploidization

Allopolyploidy is a prominent mode of speciation in higher plants. Due to the coexistence of closely related genomes, a successful allopolyploid must have the ability to invoke and maintain diploid-like behavior, both cytologically and genetically. Recent studies on natural and synthetic allopolyploids have raised many discrepancies. Most species have displayed non-Mendelian behavior in the allopolyploids, but others have not. Some species have demonstrated rapid genome changes following allopolyploid formation, while others have conserved progenitor genomes. Some have displayed directed, non-random genome changes, whereas others have shown random changes. Some of the genomic changes have appeared in the F1 hybrids, which have been attributed to the union of gametes from different progenitors, while other changes have occurred during or after genome doubling. Although these observations provide significant novel insights into the evolution of allopolyploids, the overall mechanisms of the event are still elusive. It appears that both genetic and epigenetic operations are involved in the diploidization process of allopolyploids. Overall, genetic and epigenetic variations are often associated with the activities of repetitive sequences and transposon elements. Specifically, genomic sequence elimination and chromosome rearrangement are probably the major forces guiding cytological diploidization. Gene non-functionalization, sub-functionalization, neo-functionalization, as well as other kinds of epigenetic modifications, are likely the leading factors promoting genetic diploidization.     

Quantification of the elevated rate of domain rearrangements in metazoa

Most eukaryotic proteins consist of multiple domains created through gene fusions or internal duplications. The most frequent change of a domain architecture (DA) is insertion or deletion of a domain at the N or C terminus. Still, the mechanisms underlying the evolution of multidomain proteins are not very well studied.Here, we have studied the evolution of multidomain architectures (MDA), guided by evolutionary information in the form of a phylogenetic tree. Our results show that Pfam domain families and MDAs have been created with comparable rates (0.1-1 per million years (My)). The major changes in DA evolution have occurred in the process of multicellularization and within the metazoan lineage. In contrast, creation of domains seems to have been frequent already in the early evolution. Furthermore, most of the architectures have been created from older domains or architectures, whereas novel domains are mainly found in single-domain proteins. However, a particular group of exon-bordering domains may have contributed to the rapid evolution of novel multidomain proteins in metazoan organisms. Finally, MDAs have evolved predominantly through insertions of domains, whereas domain deletions are less common.In conclusion, the rate of creation of multidomain proteins has accelerated in the metazoan lineage, which may partly be explained by the frequent insertion of exon-bordering domains into new architectures. However, our results indicate that other factors have contributed as well.     

Chance and the origin of life

Random chemical reactions in the Earth's primitive hydrosphere could have generated no more than 200 bits of information, whereas the first Darwinian organism must have encoded about a million bits, and therefore could not have arisen by chance. This information gap is bridged by separating reproduction from organism, and postulating a reproductive chemical community that would generate information by proto-Darwinian evolution. The information content of the initial comunity could have been as low as 160 bits, and its evolution might have led to the first Darwinian cell.     

Concerted evolution of exons and introns in the MHC-linked tenascin-X gene of mammals.

Two modes of evolution of repeated domains in proteins have been described: (1) a conservative mode, whereby individual domains are conserved across gene duplication and speciation events, and (2) a concerted mode, whereby repeat domains become homogenized within a gene, presumably by intragenic partial duplication and/or gene conversion. The evolution of repeated EGF-like and fibronection-type-III-like (Fn-III) domains in the vertebrate extracellular matrix proteins tenascin-X (TNX) and tenascin-C (TNC) was studied by comparisons between human and mouse orthologs and between the paralogous TNC and TNX genes. The EGF-like repeats have largely been homogenized within each gene by concerted evolution since the duplication of the two genes but have been conserved since the divergence of rodents and primates. The Fn-III domains of TNC have likewise mainly evolved in a conservative fashion since the divergence of rodents and primates. In contrast, the Fn-III repeats of TNX fall into three distinct categories with regard to mode of evolution: (1) The three C-terminal repeats have been conserved since before duplication of the TNX and TNC genes. (2) Certain other repeats have been homogenized within each gene since gene duplication but have been conserved since the divergence of rodents and primates. (3) Still other repeats have evolved in a concerted fashion in rodent and primate lineages since their divergence. Remarkably, certain introns adjacent to the exons encoding these concertedly evolving Fn-III repeats have themselves evolved in a concerted fashion. This is the first known example of concerted evolution of repeated introns within a protein-coding gene.     

Pathogenesis of neonatal group B streptococcal infections

Infections of the neonate due to the group B Streptococcus have been recognized since the 1930s, but it was during the 1970s that their incidence grew alarmingly throughout the world. A research effort stimulated by this problem has yielded significant new information about many facets of the pathogenesis of these infections. Immunologic investigations have pinpointed a lack of transplacentally acquired antibody as a significant risk factor. In the laboratory, assays of antibody which have a functional endpoint have demonstrated that the type-specific carbohydrate antigens play a major role in stimulating the development of protective antibody. These assays have been shown to correlate with certain tests of primary antigen-antibody interaction which do not have a functional endpoint, but are simpler to use in larger scale epidemiologic studies. These tools may be useful in filling the gaps in our current knowledge of the pathogenesis of this infection.