摘要:

AbstractIn addition to their function in transport of water, ions, small metabolites, and growth factors in normal plant tissue, the plasmodesmata presumably serve as routes for cell‐to‐cell movement of plant viruses in infected tissue. Virus cell‐to‐cell spread through plasmodesmata is an active process mediated by specialized virus encoded movement proteins; however, the mechanism by which these proteins operate is not clear. We incorporate recent information on the biochemical properties of plant virus movement proteins and their interaction with plasmodesmata in a model for transport of nucleic acids through plasmodesmatal channels. We propose that only single stranded (ss) nucleic acids can be transported efficiently through plasmodesmata, and that movement proteins function as molecular chaperones for ss nucleic acids to form unfolded movement protein‐ss nucleic acid complexes. These complexes are targeted to plasmodesmata. Plasmodesmatal permeability is then increased following interaction with movement protein and the entire movement complex or its nucleic acid component is translocated across the plasmodesmata

ISSN:0265-9247    

DOI:10.1002/bies.950130802

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.950130803

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

年代:1991

数据来源: WILEY

摘要:

AbstractMultidrug resistance resulting from expression of an energy‐dependent drug efflux pump encoded by the humanMDR1gene is a major impediment to effective cancer therapy. Pharmacologic intervention aimed at inhibiting this multidrug transporter should improve existing chemotherapy of human cancer, but drug development has been delayed by the difficulty and expense of developing valid animal models. Using recombinant DNA technology, a transgenic mouse has been engineered whose bone marrow is protected from the toxic effects of chemotherapy by expression of theMDR1gene. This animal system allows the rapid screening of drugs which inhibit the multidrug transporter and heralds a new era of using transgenic animals for pharmacologic screenin

ISSN:0265-9247    

DOI:10.1002/bies.950130804

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

年代:1991

数据来源: WILEY

摘要:

AbstractDuring development, large numbers of cells die by a process known as programmed cell death. This loss of cells plays a number of important roles, including the sculpting of the body form and the removal of vestigial tissues. Data obtained from a variety of organisms has suggested that a cell's ‘decision’ to die is a differentiative event, requiring the activation of specific sets of genes. Several putative ‘cell death’ genes have recently been cloned, and one has been identified as the product of the polyubiquitin gene. Accumulation of ubiquitin has been observed not only during programmed cell death, but also in several neurodegenerative disorders, including Alzheimer's

ISSN:0265-9247    

DOI:10.1002/bies.950130805

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

年代:1991

数据来源: WILEY

摘要:

AbstractTo understand the intracellular mechanisms that control exocytosis it is necessary to have access to the cell interior. This is achieved by plasma membrane permeabilisation or by application of patch‐pipettes. These conditions permit control over the cytosol composition and also allow leakage of soluble factors that may have roles in the exocytotic mechanism. Different permeabilisation methods allow different extents of leakage and therefore provide complementary data. The exocytotic machinery itself remains intact and can be activated by providing Ca2+and/or a guanine nucleotide. In some cells there is evidence for the participation of two guanine nucleotide‐binding proteins (Gpand GE), as well as a Ca2+‐binding protein. In others Ca2+is the only requirement. In a number of cell types, ATP is not required for the late steps in the secretory pa

ISSN:0265-9247    

DOI:10.1002/bies.950130806

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

年代:1991

数据来源: WILEY

摘要:

AbstractEndochondral bone formation can take place in the embryo, during fracture healing, or in postnatal animals after induction by implanted demineralized bone matrix. This matrix‐induced bone formation recapitulates the embryonic sequence of bone formation morphologically and biochemically. The steps in bone formation in both systems include differentiation of cartilage from mesenchyme, cartilage maturation, invasion of the cartilage by blood vessels and marrow precursors, and formation of bone and bone marrow. Recently, bone inductive molecules from demineralized bone matrix have been purified, sequenced and produced as recombinant proteins. While there are similarities between bone development in the embryo and that after induction by these purified molecules, the molecules responsible for bone induction in the embryo have not yet been defined. Because of similarities between the two methods of bone formation, studies of Bone induction by demineralized bone matrix may help to elucidate mechanisms of embryonic bone inductio

ISSN:0265-9247    

DOI:10.1002/bies.950130807

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.950130808

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

年代:1991

数据来源: WILEY

摘要:

AbstractDuring the past decade, it has become apparent that it is within our grasp to understand fully the development and functioning of complex organisms. It is widely accepted that this undertaking must include the elucidation of the genetic blueprint – the genome sequence – of a number of model organisms. As a prelude to the determination of these sequences, clonebased physical maps of the genomes of a number of multicellular animals and plants are being constructed. Yeast artificial chromosome (YAC) vectors, by virtue of their relatively unbiased cloning capabilities and capacity to carry large inserts, have come to play a central role in the construction of these maps. The application of YACs to the physical map of theCaenorhabditis elegansgenome has enabled cosmid clone ‘islands’ to be linked together in an efficient manner. The long‐range continuity has improved the linkage between the genetic and physical maps, greatly increasing its utility. Since the genome can be represented by a relatively small number of YACs, it has been possible to make replica filters of genomically ordered YACs available to the community

ISSN:0265-9247    

DOI:10.1002/bies.950130809

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe second messenger function of inositol 1,4,5‐ trisphosphate (InsP3) is now well‐defined – it mobilizes Ca2+from intracellular stores so that cytosolic Ca2+increases. However, the function of inositol 1,3,4,5‐ tetrakisphosphate (InsP4) has proved much more difficult to fathom, as it has been reported to exert a wide variety of effects in a collection of experimental systems. In this review, a proposed molecular mechanism for InsP4actions is discussed; it is suggested that InsP4is the second messenger that controls Ca2+entry into cells, and that it does so by binding to a receptor which itself interacts, directly or Indirectly, with the receptor for InsP3It is proposed that this is InsP4's true physiological function, but the mechanism by which it exerts this function has led to confusing data concerning its action, and also to some misconceptions about how inositol phosphates control Ca

ISSN:0265-9247    

DOI:10.1002/bies.950130810

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.950130811

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

年代:1991

数据来源: WILEY