ISSN:0265-9247    

DOI:10.1002/bies.950170502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the vertebrate spinal cord, motoneurons are clustered into longitudinal columns in agreement with the targets they innervate. Motoneurons within each column acquire properties early in development that ensure their axons navigate to appropriate targets, but how this target identity is specified is unknown. Recently, Tsuchida et al.(1)described the expression of putative regulatory genes within motor columns in the chicken spinal cord. Combinations of LIM‐family homeobox genes differentially mark columns that project to distinct target groups. Expression precedes column formation and axon outgrowth, making these genes candidates for specifying the target identity of motoneuron group

ISSN:0265-9247    

DOI:10.1002/bies.950170503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe form of higher plants is largely dependent upon cell division and expansion patterns. Taking a genetic approach, Takahashiet al.(1)have identified a regulatory molecule inArabidopsis thalianacalled DIMINUTO (DIM), which is involved in determining the degree and direction of plant cell expansion. Their extensive characterization of adimmutant suggested a direct involvement of theDIMgene in regulating cell elongation, perhaps by modulating the expression of structural genes which determine the orientation and elasticity of the cell wall.

ISSN:0265-9247    

DOI:10.1002/bies.950170504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractHigher plant shoot meristems are multicellular structures that are the site of postembryonic organogenesis. Analysis of chimeric plants has indicated that cells in different regions of the meristem can interact with each other so that their activities are coordinated during developmental processes. Correlations have not been demonstrated between events at a molecular level and the interactions observed at a phenotypic level in chimeras. Two recent papers(1,2)address this problem by reporting that expression of thefloricaulagene in one region of chimeric snapdragon meristems is sufficient to promote the transition from inflorescence to floral development and to induce the expression of the downstream organ identity genesdeficiensandplenathroughout the meristem.

ISSN:0265-9247    

DOI:10.1002/bies.950170505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractRetroviral lineage tracing experiments suggest that the cortical ventricular zone is composed of a mixture of precursor cell types. The majority generate a single cell type (neurones, astrocytes or oligodendrocytes) and the remainder generate neurones and a single type of glial cell. Pluripotential precursor cells, that have the ability to generate all three cell types, are not observed. A recent paper, however, reports that when single ventricular zone cells are cultured in isolation, a small percentage of these cells are pluripotential(1). This review will discuss what this knowledge tells us about cortical development.

ISSN:0265-9247    

DOI:10.1002/bies.950170506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractRas proteins function as critical relay switches that regulate diverse signaling pathways between cell surface receptors and the nucleus. Over the past 2‐3 years researchers have identified many components of these pathways that mediate Ras activation and effector function. Among these proteins are several guanine nucleotide exchange factors (GEFs), which are responsible for directly interacting with and activating Ras in response to extracellular stimuli. Analogous GEFs regulate Ras‐related proteins that serve other diverse cellular functions. In particular, a growing family of proteins (Dbl homology proteins) has recently been identified, which may function as GEFs for the Rho family of Ras‐related proteins. This review summarizes our current knowledge of the structure, biochemistry and biology of Ras and Rho family GEFs. Additionally, we describe mechanisms of GEF activation of Ras in signal transduction and address the potential that deregulated GEFs might contribute to malignant transformation through chronic Ras protein activ

ISSN:0265-9247    

DOI:10.1002/bies.950170507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractGenetic and molecular studies of development inCaenorhabiditis eleganshave identified regulators that appear to control pattern formation in the cellularized nematode embryo. Two genes,skn‐1andpie‐1, are required for specifying the different identities of two sister blastomeres in a 4‐cell embryo, called P2 and EMS. Theskn‐1gene encodes a DNA binding protein that may control blastomere development by regulating transcription in EMS and its descendants. ABa and ABp, the other two sisters in a 4‐cell embryo, are influenced to develop differently by cell signaling events that require the two genesapx‐1andglp‐1. In this review, I summarize evidence that some or all of these genes may encode embryonic determinants of blasto

ISSN:0265-9247    

DOI:10.1002/bies.950170508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe importance of seminal plasma in fertilization was appreciated as early as 1677 and would thus hardly seem a source for the search of antibacterial agents. The observation that seminal plasma had the ability to inhibit the growth of microorganisms in 1940 led to a systematic search for molecules possessing antimicrobial activity in addition to factors that might have a role in reproductive physiology. Extensive investigations led to the discovery in bovine seminal fluid of a 47‐residue peptide, possessing potent antimicrobial activity as well as calcium transport modulatory properties in bovine sperm. We describe in this article the two, apparently unrelated, biological activities of this peptid

ISSN:0265-9247    

DOI:10.1002/bies.950170509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractReversible acetylation at the ϵ‐amino group of lysines located at the conserved domain of core histones is supposed to play an important role in the regulation of chromatin structure and its transcriptional activity. One promising strategy for analyzing the precise function of histone acetylation is to block the activities of acetylating or deacetylating enzymes by specific inhibitors. Recently, two microbial metabolites, trichostatin A and trapoxin, were found to be potent inhibitors of histone deacetylases. Trichostatin A reversibly inhibits the mammalian histone deacetylase, whereas trapoxin causes inhibition through irreversible binding to the enzyme. The histone deacetylase from a trichostatin A‐resistant cell line is resistant to trichostatin A, indicating that the enzyme is the primary target. Both of the agents induce a variety of biological responses of cells such as induction of differentiation and cell cycle arrest. Trichostatin A and trapoxin are useful in analyzing the role of histone acetylation in chromatin structure and function as well as in determining the genes whose activities are regulated by histone acetyla

ISSN:0265-9247    

DOI:10.1002/bies.950170510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFree radicals are generally perceived as highly reactive species which are harmful to biological systems. There are, however, a number of enzymes that use carbon‐based radicals to catalyse a variety of important and unusual reactions. The most prominent example is ribonucleotide reductase, an enzyme which is crucial for the synthesis of DNA. In general, radicals are used to remove hydrogen from unreactive positions in the substrate, and in this way the substrate is activated to undergo chemical transformations that would otherwise be difficult to achieve. Several different mechanisms have evolved which allow enzymes to generate and maintain radicals in increasingly aerobic enviroments. An unexpected finding is the existance of stable protein‐based radicals, residing on a variety of amino‐acid side chains, which serve to link the radical‐generating and catalytic sites and to store the radical between tu

ISSN:0265-9247    

DOI:10.1002/bies.950170511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY