摘要:

AbstractSixteen years ago, Michael Ashburner and his colleagues proposed a hierarchical model for the genetic control of polytene chromosome puffing by the steroid hormone ecdysone. The recent molecular isolation and characterization of three early ecdysone‐inducible genes has confirmed many aspects of this model — these genes are directly induced by ecdysone, repressed by ecdysone‐induced proteins, and appear to encode DNA binding regulatory proteins. The three early genes are also remarkably similar in structure. They are all unusually long and complex, with multiple transcripts that direct the synthesis of several related proteins from each locus. Proteins encoded by two of the early genes bind to both early and late ecdysone‐induced puffs, implying that they are key regulators in the hi

ISSN:0265-9247    

DOI:10.1002/bies.950121202

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

年代:1990

数据来源: WILEY

摘要:

AbstractCentral nervous system (CNS)Abbreviations: CNS=central nervous system; PNS=peripheral nervous system; MS=multiple sclerosis; MBP=myelin basic protein; MHC=major histocompatibility complex; EAE=experimental allergic encephalomyelitis; O‐2A=oligodendrocyte‐type 2 astrocyte; GC=galactocerebroside; GFAP=glial fibrillary acidic protein; FGF=fibroblast growth factor; IGF1=insulin‐like growth factor.regeneration is a subject of great interest, particularly in diseases causing a dramatic loss of neurons. However, some CNS diseases do not affect neurons but damage other cells, such as the myelin‐forming cells — called oligodendrocytes — which are also crucial to the harmonious function of the nervous system. Diseases in which oligodendrocytes and myelin are attacked can cause devastating neurological dysfunction which is sometimes followed by recovery and myelin repair or remyelination. The question of the regeneration potential of oligodendrocytes in experimental and human demyelinating diseases such as multiple sclerosis has been debated for a long time. Present evidence suggests that oligodendrocyte precursor cells persist in the adult CNS and that oligodendrocyte regeneration can occur but may be limited by ongoing disease processes. Here we will briefly review recent advances which have broadened our understanding of the cellular and molecular events of CNS re

ISSN:0265-9247    

DOI:10.1002/bies.950121203

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

年代:1990

数据来源: WILEY

摘要:

AbstractGenome instability has been associated with progression of transformed cells to high tumorigenicity. Although genome instability may result from a variety of factors, some studies suggest that DNA in the region of a chromosome rearrangement can subsequently have much higher rates of DNA deletions or gene amplification. One approach to studying the factors that produce these high rates of DNA rearrangement is by analysis of unstable integration sites for DNA transfected into mammalian cells. Integrated sequences commonly show a temporary instability, and at rare locations this instability is continuous and can be observed even after multiple subclonings. These continuously unstable locations undergo DNA amplification of both the integrated sequences and the surrounding cell DNA, and it can occur either at the original site or on episomes after looping out from the chromosome. Because the adjacent cell DNA plays a role in this instability, and the region can be shown to be stable before integration, the results indicate that these recombinational hotspots can be formedde novoby the process of integration. Current studies are attempting to determine which sequences are responsible for the high rates of recombination and whether similar types of event are involved in the instability associated with endogenous cellular genes in cancer cells.

ISSN:0265-9247    

DOI:10.1002/bies.950121204

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

年代:1990

数据来源: WILEY

摘要:

AbstractCell–extracellular matrix interactions are important in the process of tumor cell invasion and metastasis. In particular, the interactions of tumor cells with basement membranes of tissue epithelial, as well as vascular endothelial, cells are likely to represent key steps in the metastatic process. The interactions between cells and the connective tissue matrix are mediated by a large family of cell surface receptors, the integrins, which represent multiple receptors the integrins, which represent multiple receptors for extracellular matrix and basement membrane components. Here, I review recent progress in elucidating the roles of integrins in tumor cell invasion. Altered expression of this large family of receptors on invasive tumor cells, as compared with non‐invasive cells, may represent a fundamental step in the progressive expression of the invasive phenot

ISSN:0265-9247    

DOI:10.1002/bies.950121205

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

年代:1990

数据来源: WILEY

摘要:

AbstractDuring development of theXenopusembryo, the formation of the nervous system depends on an inductive interaction between mesoderm and ectoderm. The result is a neural tube that is regionally differentiated along the anterior–posterior axis from forebrain to spinal cord (Fig. 1). The discovery of genes whose transcripts can be used as molecular markers for different regions of the nervous system has permitted reassessment of the existing theories of neural tissue formation. Although the neural inducing molecules remain elusive, the mechanism by which cells interact to form a regionally differentiated nervous system is becoming cleare

ISSN:0265-9247    

DOI:10.1002/bies.950121206

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121207

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe discovery, made in Oxford, that crude penicillin could cure systemic and life‐threatening bacterial infections was followed by attempts to purify penicillin, to determine its structure and then to produce it by total chemical synthesis. The β‐lactam structure of the molecule, first proposed in October 1943, was a source of controversy until 1945. However, no useful chemical synthesis was achieved and fermentation became the commercial source of the antibiotic.In 1953, one of the products of aCephalosporiumsp. from Sardinia was shown to be a new and hydrophilic penicillin (penicillin N). This was contaminated with a substance having the same side‐chain but a characteristic absorption spectrum. The latter, cephalosporin C, showed antibacterial activity but was not inactivated by a penicillinase. The determination of its β‐lactam structure and isolation of its nucleus enabled pharmaceutical companies to produce many semisynthetic cephalosporins.A new tripeptide was later found to be an intermediate in the biosynthesis of both penicillin N and cephalosporin C, and this was followed by the complete elucidation of the biosynthetic pathways leading to these compounds and to benzylp

ISSN:0265-9247    

DOI:10.1002/bies.950121208

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121209

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121210

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

年代:1990

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950121211

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

年代:1990

数据来源: WILEY