摘要:

AbstractIt may be that eukaryotic nuclei contain a collection of operationally independent units (genes), each controlled through its interactions with soluble protein factors which diffuse at random throughout the nucleoplasmic space. Alternatively, nuclei might be organized in such a sophisticated fashion that specific genes, occupy distinct sites and that spatially ordered RNA synthesis, processing and transport delivers mature RNAs to predestined sites in the cytoplasm.Different fields of research support each of these extreme views. Molecular biologists inspecting the precise details of specific interactions, usuallyin vitro, inevitably favour the former, while cell biologists working with far more complicated systems generally assume that more elaborate arrangements exist. In considering the importance of nuclear architecture, I have attempted to relate a collection of experiments each of which intimates some close relationship between structural aspects of chromatin organization and the precise mechanisms underlying nuclear function. I will argue that higherorder structures are crucial for achieving the observed efficiency and coordination of many nuclear processes.

ISSN:0265-9247    

DOI:10.1002/bies.950130102

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

年代:1991

数据来源: WILEY

摘要:

AbstractSince the growth cone was first described a century ago by Cajal, considerable effort has been directed towards understanding the mechanisms responsible for its guidance. Traditionally, attention has focussed on the role of adhesive molecules in determining neural development. Recently, it has become apparent that inhibitory interactions may play a crucial part in axonal navigation. A common feature of inhibition seen in three model systems (peripheral nerve segmentation, retinotectal mapping and CNS/PNS segregation) is a collapse of the motile structures of the growth cone. It is increasingly clear that the identification of molecular mechanisms of inhibition, as well as those of adhesion, will be of fundamental importance to understanding neural development.

ISSN:0265-9247    

DOI:10.1002/bies.950130103

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

年代:1991

数据来源: WILEY

摘要:

AbstractA considerable challenge confronts, any developing neuron. Before it can establish a functional and specific connection, it must extend an axon over tens and sometimes hundreds of microns through a complex and mutable environment to reach one out of many possible destinations. The field of axonal guidance concerns the control of this navigation process. To satisfactorily identify the cell interactions and molecular mechanisms that mediate axonal guidance, it is essential to first identify the pertinent cell populations. Embryonic surgeries have provided solid information on which tissues are critical and which are irrelevant to the navigation of motor axons within the chick embryo. The gross anatomical nerve pattern is established as axons respond to both positive (path) and negative (barrier) tissue environments. Analysis of the interactions of motoneurons with these tissues reveals that several cellular interactions – chemotaxis, substratum preference, and perhaps contact paralysis – are important to the common patterns of motor axon advance. Axons simultaneously interact with population‐specific cues that have begun to be identified on the tissue

ISSN:0265-9247    

DOI:10.1002/bies.950130104

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

年代:1991

数据来源: WILEY

摘要:

AbstractChemotaxis in bacteria is an excellent model for signal transduction processes. InAgrobacterium tumefaciens, the causative agent of crown gall tumour on wounded plants, it is a vital part of the organism's biology. A chromosomally‐determined chemotaxis system causes the bacterium to be attracted into the rhizosphere by chemoattractants in plant exudates. By interfacing with this system, the multifunctional products of two Tiplasmid encoded genes,virAandvirG, allow the sensing of specific wound phenolics such as acetosyringone. This attracts Ti‐plasmid harbouring A.tumefaciensto wound sites, where the higher acetosyringone concentrations lead tovirAandvirG‐mediated induction of thevir‐genes. The products of the induced genes, act in concert to effect transfer of the T‐DNA to the p

ISSN:0265-9247    

DOI:10.1002/bies.950130105

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

年代:1991

数据来源: WILEY

摘要:

AbstractCancers have a formidable capacity to develop resistance to a large and diverse array of chemical, biologic, and physical anti‐neoplastic agents. This can be largely traced to the instability of the tumor cell genome, and the resultant ability of tumor cell populations to generate phenotypic variants rapidly. It is therefore argued that anti‐cancer strategies should be directed at eliminating those genetically stable normal diploid cells that are required for the progressive growth of tumors. Micro‐vascular endothelial cells comprising the tumor vasculature represent such a normal cell target. Moreover, specificity for tumor associated vasculature by anti‐cancer agents may be achieved by virtue of the fact that many of the endothelial cells that comprise these blood vessels are in an immature, cycling, and ‘activated’ state, in contrast to the endothelial cells associated with normal tissue and organ bl

ISSN:0265-9247    

DOI:10.1002/bies.950130106

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

年代:1991

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950130107

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

年代:1991

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950130108

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

年代:1991

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950130109

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

年代:1991

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950130110

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

年代:1991

数据来源: WILEY

ISSN:0265-9247    

DOI:10.1002/bies.950130111

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

年代:1991

数据来源: WILEY