Electronic structure of polysilole and related compounds

The electronic structures, in the optimized geometries, of polysilacyclopentadiene (polysilole), polygermacyclopentadiene, and silole-thiophene alternating copolymer, have been studied theoretically using the one-dimensional tight-binding self-consistent field crystal orbital (SCF-CO) method. It has been found that the band gap values of these polymers are slightly smaller than those of the ordinary five-membered polyheterocycles such as polythiophene. The larger -polarized nature between the Group IV atom and the carbon atom might be expected to exhibit a different behaviour, compared with polythiophene, when they are doped with ann-type dopant.     

Isolation and structure of guinea pig gastric and pancreatic somatostatin

Somatostatin-14 has been isolated from guinea pig pancreas and stomach and purified to homogeneity by gel filtration, ion-exchange chromatography and reverse phase HPLC. Amino acid composition and sequence analysis indicated that guinea pig somatostatin from both tissues has the same structure as somatostatin-14 from all other mammalian species yet studied. The study has demonstrated that somatostatin-14 from gastric tissue has the same structure as the peptide from hypothalamus and pancreas.     

FOXP2 and the neuroanatomy of speech and language

That speech and language are innate capacities of the human brain has long been widely accepted, but only recently has an entry point into the genetic basis of these remarkable faculties been found. The discovery of a mutation in FOXP2 in a family with a speech and language disorder has enabled neuroscientists to trace the neural expression of this gene during embryological development, track the effects of this gene mutation on brain structure and function, and so begin to decipher that part of our neural inheritance that culminates in articulate speech.     

Mechanisms of thymus organogenesis and morphogenesis

The thymus is the primary organ responsible for generating functional T cells in vertebrates. Although T cell differentiation within the thymus has been an area of intense investigation, the study of thymus organogenesis has made slower progress. The past decade, however, has seen a renewed interest in thymus organogenesis, with the aim of understanding how the thymus develops to form a microenvironment that supports T cell maturation and regeneration. This has prompted modern revisits to classical experiments and has driven additional genetic approaches in mice. These studies are making significant progress in identifying the molecular and cellular mechanisms that control specification, early organogenesis and morphogenesis of the thymus.     

Hybridization and the evolution of invasiveness in plants and other organisms

Less than a decade ago, we proposed that hybridization could serve as a stimulus for the evolution of invasiveness in plants (Ellstrand and Schierenbeck Proc Nat Acad Sci USA 97:7043–7050, 2000). A substantial amount of research has taken place on that topic since the publication of that paper, stimulating the symposium that makes up this special issue. Here we present an update of this emergent field, based both on the papers in this volume and on the relevant literature. We reevaluate the lists that we presented in our earlier paper of reports in which hybridization has preceded the evolution of invasiveness. We discard a few cases that were found to be in error, published only as abstracts, or based on personal communication. Then we augment the list from examples in this volume and a supplementary literature search. Despite the omissions, the total number of cases has increased. Many have been strengthened. We add a list of cases in which there has been evidence that intra-taxon hybridization has preceded the evolution of invasiveness. We also provide a number of examples from organisms other than plants. We consider how our examples suggest mechanisms whereby hybridization may act to stimulate the evolution of invasiveness. Hybridization does not represent the only evolutionary pathway to invasiveness, but it is one that can explain why the appearance of invasiveness often involves a long lag time and/or multiple introductions of exotics.     

Effect of beta-endorphin and myelopeptides on the cAMP level and proliferation of lymphocytes in vitro

Beta-endorphin (10(-11)-10(-9) M) has been shown to induce naloxone-independent depression of the proliferative activity of human peripheral lymphocytes (HL), stimulated by pokeweed mitogen without affecting PHA-stimulated HL proliferation. Beta-endorphin (10(-10)-10(-7) M) also caused changes in HL cAMP level, that were blocked by naloxone. Marked individual sensitivity to beta-endorphin effects has been noted. It has been also shown that a bone marrow preparation, stimulating antibody production (myelopeptides), causes naloxone-independent depression in the proliferative activity of HL, stimulated by PHA and pokeweed mitogen, as well as naloxone-blocked decrease in cAMP HL level. It has been concluded that beta-endorphin interacts with several types of opiate lymphocyte receptors and that opioids, contained in myelopeptides, are involved in the realization of myelopeptide effect on lymphocytes.     

Investigation of ecdysteroid content and composition of Silene repens indigenous in Mongolia and introduced into western Siberia

The ecdysteroid profile was investigated by HPLC, and it has been found that 2-deoxyecdysone, 2-deoxy-20-hydroxyecdysone, polypodine B, 20-hydroxyecdysone, and integristerone A are synthesized in the aerial part. The composition of biologically active substances (BAS) has been investigated, and the presence of triterpene glycosides, alkaloids and flavonoids has been confirmed; tannins have been detected for the first time. It has been shown that the ecological conditions, such as altitude above sea level and humidity, influence the ecdysteroid composition and BAS levels.     

The origin and evolution of the neural crest

Many of the features that distinguish the vertebrates from other chordates are derived from the neural crest, and it has long been argued that the emergence of this multipotent embryonic population was a key innovation underpinning vertebrate evolution. More recently, however, a number of studies have suggested that the evolution of the neural crest was less sudden than previously believed. This has exposed the fact that neural crest, as evidenced by its repertoire of derivative cell types, has evolved through vertebrate evolution. In this light, attempts to derive a typological definition of neural crest, in terms of molecular signatures or networks, are unfounded. We propose a less restrictive, embryological definition of this cell type that facilitates, rather than precludes, investigating the evolution of neural crest. While the evolutionary origin of neural crest has attracted much attention, its subsequent evolution has received almost no attention and yet it is more readily open to experimental investigation and has greater relevance to understanding vertebrate evolution. Finally, we provide a brief outline of how the evolutionary emergence of neural crest potentiality may have proceeded, and how it may be investigated.     

Properties and applications of undecylprodigiosin and other bacterial prodigiosins

The growing demand to fulfill the needs of present-day medicine in terms of novel effective molecules has lead to reexamining some of the old and known bacterial secondary metabolites. Bacterial prodigiosins (prodiginines) have a long history of being re markable multipurpose compounds, best examined for their anticancer and antimalarial activities. Production of prodigiosin in the most common producer strain Serratia marcescens has been described in great detail. However, few reports have discussed the ecophysiological roles of these molecules in the producing strains, as well as their antibiotic and UV-protective properties. This review describes recent advances in the production process, biosynthesis, properties, and applications of bacterial prodigiosins. Special emphasis is put on undecylprodigiosin which has generally been a less studied member of the prodigiosin family. In addition, it has been suggested that proteins involved in undecylprodigiosin synthesis, RedG and RedH, could be a useful addition to the biocatalytic toolbox being able to mediate regio- and stereoselective oxidative cyclization. Judging by the number of recent references (216 for the 2007–2013 period), it has become clear that undecylprodigiosin and other bacterial prodigiosins still hold surprises in terms of valuable properties and applicative potential to medical and other industrial fields and that they still deserve continuing research curiosity.     

空间和平衡理论在景观生态学中的发展和应用

传统生态学承认生态系统中平衡、稳定状态的存在 ,“自然平衡理论”是其集中体现。而近 30年来 ,非平衡理论的出现 ,使得人们对生态系统的认识发生了彻底的改变。非平衡理论认为 ,偶然事件 (如干扰等 )在生态过程中起着重要作用。随着认识的转变 ,对生态过程中的“空间”和空间异质性的理解也发生了变化 ,传统生态学总是试图回避空间动态和空间异质性问题 ,而着重强调时间格局的重要性。但在近 2 0年来 ,空间格局则得到了广泛重视。空间理论及空间格局的研究表明 ,空间异质性既可能增加生态系统和生态过程的稳定性 ,也可能降低其稳定性。分析两种变化趋势 ,指出了它们的相互关系 ,同时讨论了空间理论的发展及其在景观生态学中的应用 ,并阐述了生态平衡的含义。     

Regulation of the functional and mechanical properties of platelet and red blood cells by nitric oxide donors

The effect of NO donors (sodium nitroprusside, S-nitrosoglutathione, dinitrosyl-iron complexes) on the functional and mechanical properties of human platelets and red blood cells has been investigated. It has been established by atomic force microscopy that NO donor-induced platelet disaggregation is accompanied by changes in the elastic properties of cells. It has been shown that, in the presence of NO donors, the detergent-induced hemolysis of red blood cells is delayed, and the elasticity modulus of these cells decreases. The results obtained indicate that NO donors regulate the structural and functional properties of platelets and red blood cells.     

Role of estrogens in adipocyte development and function

Estrogen has historically been viewed as a major regulator of adipose tissue in adult females, but recent work has indicated that estrogen's role in adipose biology may be broader than initially appreciated and has also provided important insights into the mechanism of estrogen effects on adipose tissue. Estrogen has direct effects on adipocytes to inhibit lipogenesis and may also have direct effects on other cellular constituents of adipose tissue, as well as metabolic effects on other target organs that can regulate adipose tissue. Estrogen has central effects on food consumption and energy expenditure that contribute to its overall inhibitory effects on adipose deposition. Estrogen also plays an important role in regulating adipose deposition in males and recently has been shown to be an important factor in the determination of adipocyte number, indicating that it regulates key developmental events in adipogenesis. Although critical questions still remain in our understanding of the overall role of estrogen in adipose tissue, it is clear that estrogen plays a more important role in adipose tissue than originally realized and that it is a major regulator of adipose tissue in both sexes during development and adulthood.     

人参皂苷Rg3药代动力学及抗肿瘤作用的研究进展

人参皂苷Rg3是存在于天然药物人参中的一种四环三萜皂苷,研究表明人参皂苷Rg3具有确切的抗肿瘤活性,在诱导肿瘤细胞凋亡、抑制肿瘤细胞增殖、增强免疫功能等方面具有显著作用。本文通过查阅近年来相关文献,概括人参皂苷Rg3药效学及药代动力学研究进展,探讨人参皂苷Rg3抗肿瘤的作用机理以及体内吸收、分布、代谢、排泄规律,并在此基础上结合现代中药理论对今后人参皂苷Rg3的研究方向进行了展望。     

Synthesis and study of biological activity of stereoisomeric dipeptides containing tyrosine and arginine residues

Series of methyl esters of stereoisomeric dipeptides of the sequences Tyr-Arg and Arg-Tyr has been synthesized by classic methods of the peptide chemistry. The study of their reactivity towards thrombin and trypsin has shown that the kinetic parameters of enzyme-catalyzed hydrolyses of stereoisomeric compounds differ in values essentially. Testing the synthetic peptides on analgic effect, on inhibition of the reaction fibrinogen with thrombin or on influence upon the process of fibrin-monomer polymerization has shown that these biological effects depend on peptide structure and on configuration of amino acid residues forming the peptides.     

The role of the vacuole in the accumulation and mobilization of sucrose

The contribution that isolated vacuoles have made to understanding sucrose storage and mobilization is reviewed briefly, with particular reference to the storage root of red beet (Beta vulgaris L.). Work with isolated vacuoles has shown that in this tissue sucrose is confined to the vacuole and some progress has been made in elucidating the possible mechanism of sucrose transport into the vacuole. The evidence that this is a H⁺: sucrose antiport, dependent on the activity of a proton-translocating ATPase is examined. It is concluded that while there is some evidence for the presence of a proton pump, a link between this and sucrose uptake has still to be established. Using isolated vacuoles it has been demonstrated that during mobilization of sucrose, hydrolysis occurs within the vacuole but the mechanism of unloading of hexoses from the vacuole remains to be elucidated.     

Cell biology and clinical promise of G-CSF: immunomodulation and neuroprotection

In the light of the enthusiasm to use of recombinant human granulocyte colony-stimulating factor (G-CSF) for immunomodulation and neuroprotection, it should be remembered that the current knowledge is based on a century of laborious research. G-CSF is a pleiotropic cytokine playing a major role as regulator of haematopoiesis. Although the precise mechanisms of G-CSF are not known, there is growing evidence supporting the notion that G-CSF also exerts profound immunoregulatory effect in adaptive immunity and has a neuroprotective role in both cerebral ischemia and neurodegeneration. Here, we describe the immunomodulation and the neuroprotection that can be achieved with G-CSF, and summarize possible mechanisms of G-CSF as a potential therapeutic agent in autoimmune diseases and neurological disorders. Our understanding of these novel sites of action of G-CSF has opened therapeutic avenues for the treatment of autoimmune diseases and neurological disorders, and has translated the beneficial effects of G-CSF from basic experiments to clinical patients.     

Identification and characterization of QTL controlling Agrobacterium-mediated transient and stable transformation of Brassica oleracea

A commonly encountered difficulty with the genetic engineering of crop plants is that different varieties of a particular species can show great variability in the efficiency with which they can be transformed. This increases the effort required to introduce transgenes into particular genetic backgrounds. The use of Substitution Lines has allowed the finer mapping of three Quantitative Trait Loci (tf1, tf2 and tf3) that explain 26% of the variation in the efficiency of Agrobacterium-mediated transformation in Brassica oleracea. Use of an 'orthogonal set' of genotypes (containing all eight possible combinations of 'positive' and 'negative' alleles at the three QTL), along with time course studies of transgene expression, has allowed the determination of the stages at which these genes have their effects during transformation. With regard to control of the level of transient transgene expression, tf1 (on LGO1) alone has no detectable effect, whilst tf2 (on LGO3) and tf3 (on LGO7) have highly significant effects (P < 0.001). All three loci have highly significant (P < 0.001) effects on the levels of expression of stably integrated transgene. The use of RFLP markers has shown that tf1 and tf2 are in duplicated regions of the B. oleracea genome and appear to be paralogous in origin. Colinearity of these regions with the A. thaliana genome has been identified. The results allow the selection of progeny Brassica oleracea genotypes that are more efficiently transformed than either parent used in the original cross.     

Krebs and his trinity of cycles

Everyone who has ever taken biology at school has heard of the Krebs cycle, but few realize that Hans Krebs also discovered two other cycles. It is appropriate, at the centenary of his birth, to consider the circumstances and experiments that led Krebs to establish these metabolic pathways.     

Sequence heterochrony and the evolution of development

One of the most persistent questions in comparative developmental biology concerns whether there are general rules by which ontogeny and phylogeny are related. Answering this question requires conceptual and analytic approaches that allow biologists to examine a wide range of developmental events in well-structured phylogenetic contexts. For evolutionary biologists, one of the most dominant approaches to comparative developmental biology has centered around the concept of heterochrony. However, in recent years the focus of studies of heterochrony largely has been limited to one aspect, changes in size and shape. I argue that this focus has restricted the kinds of questions that have been asked about the patterns of developmental change in phylogeny, which has narrowed our ability to address some of the most fundamental questions about development and evolution. Here I contrast the approaches of growth heterochrony with a broader view of heterochrony that concentrates on changes in developmental sequence. I discuss a general approach to sequence heterochrony and summarize newly emerging methods to analyze a variety of kinds of developmental change in explicit phylogenetic contexts. Finally, I summarize a series of studies on the evolution of development in mammals that use these new approaches.     

Design of potent and specific inhibitors of carboxypeptidases A and B.

The combination in one molecule of functional groups that can interact specifically with different substrate binding areas at the active site of carboxypeptidases A and B has led to the development of potent and specific inhibitors of these enzymes. 2-Benzyl-3-mercaptopropanoic acid (SQ 14,603) has a Ki of 1.1 x 10(-8) M vs. carboxypeptidase A and a Ki of 1.6 x 10(-4) M vs. the B enzyme. 2-Mercaptomethyl-5-guanidinopentanoic acid (SQ 24,798) has a Ki of 4 x 10(-10) M vs. carboxypeptidase B and a Ki of 1.2 x 10(-5) M vs. carboxypeptidase A. It is proposed that the sulfhydryl groups of these inhibitors bind to the catalytically important zinc ions of these enzymes, and that, in conjunction with the benzyl and guanidinopropyl side chains, they are responsible for their specificity.