COMPARATIVE HYDROLYSIS OF GELATIN BY PEPSIN,TRYPSIN, ACID,AND ALKALI

A comparison has been made of the relative velocity of hydrolysis of the various peptid linkings of the gelatin molecule when hydrolyzed by acid, alkali, pepsin or trypsin. It has been found that: 1. Those linkages which are most rapidly split by pepsin or trypsin are among the more resistant to acid hydrolysis. 2. Those linkages which are hydrolyzed by pepsin are also hydrolyzed by trypsin. 3. Trypsin hydrolyzes linkages which are not attacked by pepsin. 4. Of the linkages which are hydrolyzed by both enzymes, those which are most rapidly hydrolyzed by pepsin are only slowly attacked by trypsin. 5. Those linkages which are attacked by trypsin or pepsin are among the ones first (most rapidly) hydrolyzed by alkali. In general it may be said that the course of the early stages of hydrolysis of gelatin is similar with alkali, trypsin, or pepsin and quite different with acid.     

Study of the regulation of plastid development in Euglena gracilis. II. Functional localisation and synthesis of ribosomal chloroplast particles (author's transl)]

Chloroplast ribosomes in greening cells of Euglena gracilis are found either in the stroma or bound to thylakoid membranes. The membrane-bound chloroplast ribosomes are of two main types: those which can be released by 0.5 M KCl or by puromycin and 0.5 M KCl, and those which are released by detergent (deoxycholate or Triton X-100) and KCl. The ribosomes which are released by puromycin are presumably bound to chloroplast membrane by nascent peptide chains. Ribosomes released by puromycin are found only during the course of plastidial differentiation at the time of active thylacoid membrane synthesis. Following greening, those ribosomes remain bound to the membranes but can be removed by KCl alone. An analysis of RNA labelling showed that 30-S but not 53-S subunits of membrane-bound ribosomes are of uniform specific activity. This suggests that 30-S subunit exchange in a common pool while 53 S subunits remain membrane bound and do not exchange in a common pool. Membrane-bound chloroplast ribosomes which are released either by puromycin or by detergent are originally derived from loosely bound particles, released by 0.5 M KCl.     

Stimulation of rat mastocytes and molecular oxygen

Free peritoneal mast-cells of the rat are stimulated in vitro by molecular oxygen as well as by hydrogen peroxide. Histamine release is also observed in vivo when molecular oxygen or diluted solutions of hydrogen peroxide are injected into the peritoneal cavity of the rat. Inflammatory lesions are produced (vascular congestion, oedema, exudate) which are suppressed by pretreatment with anti-H1 antihistaminics. When hydrogen peroxide solutions are more concentrated, inflammation is also provoked but antihistaminics are no more inhibitory. Mast-cells of the skin and of the lungs are not stimulated neither by molecular oxygen, nor by hydrogen peroxide.     

几种植物组织及其原生质体过氧化物酶同工酶的比较研究

对马尾松幼苗子叶和胚轴、甘蔗、小麦、烟草、黄花菜等幼叶及其原生质体的过氧化物酶同工酶(POI)分别作比较研究。观察到凡经纤维素酶处理的各植物组织POI酶带数均多于未经纤维素酶处理的组织的酶带数;除个别例外,后者一般又比无壁原生质体的酶带数多。此种差异随植株生长年龄而增大,表明植物组织内大部分POI主要存于质外体中。     

Protective antigens of bloodstage Plasmodium knowlesi parasites

The simian malaria Plasmodium knowlesi provides many favourable features as an experimental model; it can be grown in vivo or in vitro. Parasites of defined variant specificity and stage of development are readily obtained and both the natural host and a highly susceptible host are available for experimental infection and vaccination trials. Proteins synthesized by erythrocytic P. knowlesi parasites are characteristic of the developmental stage, as are the alterations that the parasite induces in the red cell surface. Erythrocytic merozoites are anatomically and biochemically complex, their surface alone is covered by at least eight distinct polypeptides. Immune serum from merozoite-immunized rhesus recognizes many parasite components, especially those synthesized by schizonts. All of the merozoite surface components and some of the schizont-infected red cell surface antigens are recognized by such immune sera. Rhesus monkeys rendered immune by repeated infection may by contrast recognize comparatively few antigens; a positive correlation was established for these 'naturally' immunized monkeys between protection and antibody directed against a 74 000 molecular mass antigen. Immunization with this purified antigen confers partial protection. Other putative protective antigens have been identified by monoclonal antibodies that inhibit merozoite invasion of red cells in vitro. The antigens recognized by inhibitory monoclonal antibodies are synthesized exclusively by schizonts and are processed, at the time of schizont rupture and merozoite release, to smaller molecules that are present on the merozoite surface. The multiplicity of protective antigens is clearly demonstrated by the fact that seven distinct merozoite surface antigens are recognized by three different inhibitory monoclonals. None of the protective antigens identified are variant or strain specific.     

同时检测血清中多种抗体的蛋白质微阵列研究

建立一种用蛋白质微阵列法可同时检测血清中艾滋病毒（HIV）, 丙型肝炎病毒（HCV）和梅毒螺旋体（TP）抗体的方法.将基因工程HIV、HCV和TP 3种融合抗原共价结合于固相载体玻片上,制成蛋白质微阵列,血清样本经稀释、加样、孵育、洗涤后,加上Cy3荧光标记二抗,洗涤,激光共聚扫描,将获得的图片用Bio-discover公司的Imagene专用分析软件进行分析,所获数据在经过自行编写的软件,根据Cutoff值自动生成判断结果.用此蛋白质微阵列系统检测了400例阴性血清,确定了Cutoff值,检测中国药品生物制品检定研究所的HIV, HCV和TP 3种参比品,并与3种ELISA试剂盒的结果进行了比较.蛋白质微阵列的艾滋病毒阳性和阴性符合率均为100%(20/20); 丙型肝炎病毒阳性和阴性符合率均为95%(38/40).梅毒螺旋体参比品阳性符合率为100%(10/10),阴性符合率为100%(20/20),蛋白质微阵列与三种ELISA试剂检测国家HIV、TP、HCV参比品（共150份血清样本）,结果具有高度的符合率.     

Ultrastructure of the foregut and associated glands of Calicotyle kröyeri (Monogenea: Monopisthocotylea)

The mouth, pharynx and oesophagus of Calicotyle are lined by syncytial epithelia, and there are numerous unicellular glands associated with the oesophagus. An infolding of unmodified external tegument lines the mouth cavity and is connected by discrete cytoplasmic processes to subjacent perikarya. It contains two types of secretory body and its luminal surface is invested with a finely filamentous coating. The pharynx and oesophagus are lined by irregularly-folded epithelia that are interconnected by a septate desmosome. Membranous inclusions distinguish the pharynx epithelium and there is a well developed basal lamina for insertion of the pharyngeal muscles. The oesophagus epithelium is perforated by the openings of the oesophageal glands. These lie in the surrounding parenchyma and produce a dense, membrane-bound secretion which is conveyed by duct-like extensions of the glands to the oesophagus lumen. The ducts are supported in places by microtubules and are anchored to the oesophageal epithelium by septate desmosomes. A septate desmosome also marks the junction between the epithelium and the gut caeca.     

Cytochemical and fine structural analysis of oogenesis in the gastropod, Ilyanassa obsoleta

An analysis of differentiating oocytes of the gastropod, Ilyanassa obsoleta, has been made by techniques of light and electron microscopy. Early previtellogenic oocytes are limited by a smooth surfaced oolemma and are associated with each other by maculae adhaerentes. Previtellogenic oocytes are also distinguished by a large nucleus containing randomly dispersed aggregates of chromatin. Within the ooplasm are Golgi complexes, mitochondria and a few cisternae of the rough endoplasmic reticulum. When vitellogenesis begins, the oolemma becomes morphologically specialized by the formation of microvilli. One also notices an increase in the number of organelles and inclusions such as lipid droplets. During vitellogenesis there is a dilation of the saccules of the Golgi complexes and cisternae of the endoplasmic reticulum. Associated with the Golgi complexes are small protein-carbohydrate yolk precursors encompassed by a membrane. These increase in size by fusing with each other. The “mature” yolk body is a membrane-bounded structure with a central striated core and a granular periphery. At maturity a major portion of the ooplasmic constituents such as as mitochondria and lipid droplets occupy the animal region while the bulk of the population of yolk bodies are situated in the vegetal hemisphere. The follicle cells incompletely encompass the developing oocyte. In addition to the regularly occurring organelles, follicle cells are characterized by the presence of large quantities of rough endoplasmic reticulum and Golgi complexes whose saccules are filled with a dense substance. Associated with the Golgi saccules are secretory droplets of varied size. Amongst the differentiating oocytes and follicle cells are Leydig cells. These cells are characterized by a large vacuole containing glycogen. A possible function for the follicle and Leydig cells is discussed.     

Der Filterapparat der Kaulquappen

Anuran larvae are threatened by predators and desiccation of their aquatic habitats. The rapid metamorphosis triggered by fast growth enables early leave of the waters and avoidance of the jeopardieses. The fast growth is facilitated by the nearly unlimited nutritive support utilized by the filter apparatus in cooperation with the oral disc. They are novelties and were formed by the common ancestor of anuran larvae and are common traits. The filter apparatus and the oral disc are understood as key inovations because of their crucial role in niche occupation, radiation and speciation. Other rare novelties are oviductal gestation and parental care. Numerous additional strategies contribute to prevent complete extinction during development. They range from egg deposition in lotic waters and special adaptations such as terrestrial and arboricol development to direct development. The morphological adaptations of these larvae are only modifications of the bauplan in proportions and arrangements of anatomical components. They are no novelties.     

Colicin biology.

Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.     

Glycosylation-independent ERAD pathway serves as a backup system under ER stress

During endoplasmic reticulum (ER)–associated degradation (ERAD), terminally misfolded proteins are retrotranslocated from the ER to the cytosol and degraded by the ubiquitin-proteasome system. Misfolded glycoproteins are recognized by calnexin and transferred to EDEM1, followed by the ER disulfide reductase ERdj5 and the BiP complex. The mechanisms involved in ERAD of nonglycoproteins, however, are poorly understood. Here we show that nonglycoprotein substrates are captured by BiP and then transferred to ERdj5 without going through the calnexin/EDEM1 pathway; after cleavage of disulfide bonds by ERdj5, the nonglycoproteins are transferred to the ERAD scaffold protein SEL1L by the aid of BiP for dislocation into the cytosol. When glucose trimming of the N-glycan groups of the substrates is inhibited, glycoproteins are also targeted to the nonglycoprotein ERAD pathway. These results indicate that two distinct pathways for ERAD of glycoproteins and nonglycoproteins exist in mammalian cells, and these pathways are interchangeable under ER stress conditions.     

The floodplain grasslands of the Middle Lena-river. I. General characteristic and ordination

The middle part of one of the largest rivers of Eurasia, the Lena, stretches for a more than 1500 km; the width of its floodplain varies from 5 to 30 km. This floodplain is covered by islands at various stages of development, which are covered by a mosaic of different successional stages. Forests are the terminal stage of succession. Soils are permafrost, ranging from chernozem to saline and alluvial types. Grassland communities are due mainly to the activity of man. Two major ecological factors are responsible for the differentiation: hydrothermic regime (regulated mainly by the altitude above the river) and by soil salinity. Both direct and indirect gradient analyses are used to demonstrate this relation. Species positions along these gradients are given. Two climatically differentiated parts of the floodplain are distinguished. The first steppe-meadow floodplain is characterized by low soil salinity and a more favourable regime of precipitation; the second (meadow-steppe part) by a very dry and continental climate and strong soil salinization up to true sodum-chloride solontchaks.     

Taste receptors in the gastrointestinal tract. V. Acid sensing in the gastrointestinal tract

Luminal acidity is a physiological challenge in the foregut, and acidosis can occur throughout the gastrointestinal tract as a result of inflammation or ischemia. These conditions are surveyed by an elaborate network of acid-governed mechanisms to maintain homeostasis. Deviations from physiological values of extracellular pH are monitored by multiple acid sensors expressed by epithelial cells and sensory neurons. Acid-sensing ion channels are activated by moderate acidification, whereas transient receptor potential ion channels of the vanilloid subtype are gated by severe acidosis. Some ionotropic purinoceptor ion channels and two-pore domain background K(+) channels are also sensitive to alterations of extracellular pH.     

A review of criticisms of phylogenetic nomenclature: is taxonomic freedom the fundamental issue?

The proposal to implement a phylogenetic nomenclatural system governed by the PhyloCode), in which taxon names are defined by explicit reference to common descent, has met with strong criticism from some proponents of phylogenetic taxonomy (taxonomy based on the principle of common descent in which only clades and species are recognized). We examine these criticisms and find that some of the perceived problems with phylogenetic nomenclature are based on misconceptions, some are equally true of the current rank-based nomenclatural system, and some will be eliminated by implementation of the PhyloCode. Most of the criticisms are related to an overriding concern that, because the meanings of names are associated with phylogenetic pattern which is subject to change, the adoption of phylogenetic nomenclature will lead to increased instability in the content of taxa. This concern is associated with the fact that, despite the widespread adoption of the view that taxa are historical entities that are conceptualized based on ancestry, many taxonomists also conceptualize taxa based on their content. As a result, critics of phylogenetic nomenclature have argued that taxonomists should be free to emend the content of taxa without constraints imposed by nomenclatural decisions. However, in phylogenetic nomenclature the contents of taxa are determined, not by the taxonomist, but by the combination of the phylogenetic definition of the name and a phylogenetic hypothesis. Because the contents of taxa, once their names are defined, can no longer be freely modified by taxonomists, phylogenetic nomenclature is perceived as limiting taxonomic freedom. We argue that the form of taxonomic freedom inherent to phylogenetic nomenclature is appropriate to phylogenetic taxonomy in which taxa are considered historical entities that are discovered through phylogenetic analysis and are not human constructs.     

Comparison of proteins bound to the different functional classes of messenger RNA.

Proteins from nuclear ribonucleoproteins, informosomes, polysomal messenger ribonucleoproteins and cytoplasmic "binding factor" are characterized. 1. Nuclear ribonucleoproteins are purified from nuclei disrupted by ultrasonication. Possible contamination by nucleoplasm, histones or remaining cytoplasmic structures is controlled. 2. Informosomal proteins are obtained by mild RNAase degradation. This method gives informosomal proteins without appreciable contamination. 3. Polysomal messenger ribonucleoproteins are obtained from cells where the initiation of protein synthesis is arrested in order to release the messenger ribonucleoproteins from the polysomes. Their proteins are obtained like the informosomal proteins by mild RNAase digestion. No contamination by informosomes could be detected by sodium dodecyl sulfate gel electrophoresis. 4. Cytoplasmic "binding factor" proteins are purified by affinity chromatography. 5. The four sets of proteins are analysed by sodium dodecylsulfate acrylamide gel electrophoresis. In spite of the fact that some proteins from one or another kind of messenger ribonucleoprotein, have apparently the same molecular weight, the majority of proteins differ.     

Evidence That IAA Conjugates Are Slow-Release Sources of Free IAA in Plant Tissues

Evidence that indoleacetic acid (IAA) conjugates are metabolized via enzyme-catalyzed hydrolysis to free IAA and that their biological activities are related to the rates at which they are hydrolyzed by the tissue is presented. These conclusions are based on the following observations. Slow but continuous decarboxylation of the IAA moiety of IAA-l-alanine and IAA-glycine occurs when these conjugates are applied to pea (Pisum sativum L. cv. Alaska) stem segments. Inasmuch as IAA conjugates are protected from peroxidase-catalyzed oxidative decarboxylation, the conjugates are probably hydrolyzed and the freed IAA then further metabolized. Free IAA and IAA-l-alanine are converted, by pea stem tissue, into the same metabolites. The metabolism is enzymic, since conjugates of IAA with the d-isomers of the amino acids are inactive. Ethylene production induced by IAA-l-alanine and by IAA-glycine is correlated with their hydrolysis, as indicated by their decarboxylation and with the appearance or nonappearance of IAA metabolites in the tissues.     

Colicin Biology

Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.     

Multiple loop conformations of peptides predicted by molecular dynamics simulations are compatible with nuclear magnetic resonance

The affinity and selectivity of protein-protein interactions can be fine-tuned by varying the size, flexibility, and amino acid composition of involved surface loops. As a model for such surface loops, we study the conformational landscape of an octapeptide, whose flexibility is chemically steered by a covalent ring closure integrating an azobenzene dye into and by a disulfide bridge additionally constraining the peptide backbone. Because the covalently integrated azobenzene dyes can be switched by light between a bent cis state and an elongated trans state, six cyclic peptide models of strongly different flexibilities are obtained. The conformational states of these peptide models are sampled by NMR and by unconstrained molecular dynamics (MD) simulations. Prototypical conformations and the free-energy landscapes in the high-dimensional space spanned by the phi/psi angles at the peptide backbone are obtained by clustering techniques from the MD trajectories. Multiple open-loop conformations are shown to be predicted by MD particularly in the very flexible cases and are shown to comply with the NMR data despite the fact that such open-loop conformations are missing in the refined NMR structures.     

Variances and Asymptotic Distributions of Direct Standardized Rates

Formulas for the variance of direct standardized rates are given for three different sampling models. The three models are product multinomial models when population totals are fixed by design, or strata totals are fixed by design, or cell (each population—each stratum) totals are fixed by design. Asymptotic distributions are derived for each model. A discussion on the relevance and use of standardized rates and the need for distribution theory is also provided.