摘要:

AbstractDuring late embryonic and early postnatal development, synaptic connections are extensively modified so that some functional connections are weakened and eliminated from a neural circuit while others are strengthened and maintained. The mechanisms that underlie synapse elimination are beginning to be understood from studies of the neuromuscular junction. A recent paper(1)provides some intriguing insights into the role proteases may play in the developmental disassembly of neuromuscular synapses.

ISSN:0265-9247    

DOI:10.1002/bies.950190402

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

年代:1997

数据来源: WILEY

摘要:

AbstractHigher plants must undergo a major developmental switch, the transition to flowering, if they are to successfully complete their life cycle. In many plants, the crucial decision of when to begin to produce flowers is primarily controlled by environmental signals. The process of floral induction involves the integration of the activities of two types of genes: those that control flowering time as a response to the environment as well as an endogenous clock, and those that determine the floral identity of the cells. The first direct link between these two classes of genes has now been demonstrated(1). Forced expression ofCONSTANS, a flowering‐time gene, promotes flowering through the transcriptional activation ofLEAFY, a flower‐meristem‐identity

ISSN:0265-9247    

DOI:10.1002/bies.950190403

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

年代:1997

数据来源: WILEY

摘要:

AbstractGenetic analysis ofDrosophilahas shown that a morphogenetic gradient of the Transforming Growth Factor‐β family memberdpppatterns the embryonic dorsalventral axis. Molecular and embryological evidence fromXenopushas strongly suggested a similar role forBmp‐4, thedpphomolog, in patterning the dorsalventral axis of chordates. A recent report has now identified mutations in two genes,dinoandswirl, that disrupt dorsal‐ventral patterning in the zebrafishDanio rerio(1). Characterization of these mutations parallels findings fromDrosophila, thus establishing a genetic framework for the analysis of dorsalventral patterning in a vert

ISSN:0265-9247    

DOI:10.1002/bies.950190404

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

年代:1997

数据来源: WILEY

摘要:

AbstractRecent advances in our understanding of developmental phenomena has come from highly interdisciplinary studies where molecular biology, ecology and evolution converge to elucidate fundamental mechanisms, how they change through time, and what function they actually have in the context of the niche of the organism. A recent study on butterfly eyespots(1)pinpoints the surprisingly simple regulatory cascade controlling such an apparently complex phenotype. The implications go beyond the elucidation of a fascinating developmental pathway, into the mechanisms and tempo of speciation and macroevolution.

ISSN:0265-9247    

DOI:10.1002/bies.950190405

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

年代:1997

数据来源: WILEY

摘要:

AbstractEmbryonic development results in animals whose body plans exhibit a variety of symmetry types. While significant progress has been made in understanding the molecular events underlying the early specification of the antero‐posterior and dorso‐ventral axes, little information has been available regarding the basis for left‐right (LR) differences in animal morphogenesis. Recently however, important advances have been made in uncovering the molecular mechanisms responsible for LR patterning. A number of genes (including well‐known signaling molecules such asSonic hedgehogandactivin) are asymmetrically expressed in early chick embryos, well before the appearance of morphological asymmetries. One of these,nodal, is asymmetrically expressed in frogs and mice as well, and its expression is altered in mouse mutants exhibiting defects in laterality. In the chick, these genes regulate each other in a sequential cascade, which independently determines the situs of the heart and other

ISSN:0265-9247    

DOI:10.1002/bies.950190406

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

年代:1997

数据来源: WILEY

摘要:

AbstractIntermediate filaments, which form the structural framework of both the cytoskeleton and the nuclear lamina in most eukaryotic cells, have been found to be highly dynamic structures. A continuous exchange of subunit proteins at the filament surface and a stabilisation of soluble subunits by chaperone‐type proteins may modulate filament structure and plasticity. Recent studies on the cell cycle‐dependent interaction of intermediate filaments with associated proteins, and a detailed analysis of intermediate filament phosphorylation in defined subcellular locations at various stages of mitosis, have brought new insights into the molecular mechanisms involved in the mitotic reorganisation of intermediate filaments. Some of these studies have allowed new speculations about the possible cellular functions of cytoplasmic intermediate filaments, and increased our understanding of the specific functions of the lamins and the lamina‐associated membrane proteins in the post‐mitotic reassembly of the

ISSN:0265-9247    

DOI:10.1002/bies.950190407

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

年代:1997

数据来源: WILEY

摘要:

AbstractCyclin‐dependent kinases and their regulatory subunits, the cyclins, are known to regulate progression through the cell cycle. Yet these same proteins are often expressed in non‐cycling, differentiated cells. This review surveys the available information about cyclins and cyclin‐dependent kinases in differentiated cells and explores the possibility that these proteins may have important functions that are independent of cell cycle regul

ISSN:0265-9247    

DOI:10.1002/bies.950190408

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

年代:1997

数据来源: WILEY

摘要:

AbstractUnder the putative influence of dietary selection pressure, the subcellular distribution of alanine:glyoxylate aminotransferase 1 (AGT) has changed on many occasions during the evolution of mammals. Depending on the particular species, AGT can be found either in peroxisomes or mitochondria, or in both peroxisomes and mitochondria. This variable localization depends on the differential expression of N‐terminal mitochondrial and C‐terminal peroxisomal targeting sequences by the use of alternative transcription and translation initiation sites. AGT is peroxisomal in most humans, but it is mistargeted to the mitochondria in a subset of patients suffering from the rare herediatry disease primary hyperoxaluria type 1. Mistargeting is due to the unlikely combination of a normally occurring polymorphism that generates a functionally weak mitochondrial targeting sequence and a disease‐specific mutation which, in combination with the polymorphism, inhibits AGT dimerization. The mechanisms by which AGT can be targeted differentially to peroxisomes and/or mitochondria highlight the different molecular requirements for protein import into these two organ

ISSN:0265-9247    

DOI:10.1002/bies.950190409

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe molecular pathways for insulin's signal transduction from its cell surface receptor to the cell's interior metabolic machinery remain in many ways uncharted. Lately two molecules have been proposed as second messengers transducing the insulin signal into the target cell. One is a phospholigosaccharide/inositolphosphoglycan and the other is diacylglycerol, both deriving from the same plasma membrane glycolipid, which is hydrolysed in response to insulin treatment. The phospho‐oligosaccharide appears to mediate many metabolic effects of insulin through control of the phosphorylation state of key regulatory metabolic enzymes. Diacylglycerol may mediate insulin's stimulation of glucose transport over the plasma membrane. The glycolipid precursor of these putative second messengers, as well as the receptor for insulin, appear to be localized in caveolae microdomains of the plasma membrane, and glucose transporters accumulate in caveolae in response to insulin treatment, suggesting a focal role for caveolae in insulin signallin

ISSN:0265-9247    

DOI:10.1002/bies.950190410

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

年代:1997

数据来源: WILEY

摘要:

AbstractHow different neural crest derivatives differentiate in distinct embryonic locations in the vertebrate embryo is an intriguing issue. Many attempts have been made to understand the underlying mechanism of specific pathway choices made by migrating neural crest cells. In this speculative review we suggest a new mechanism for the regulation of neural crest cell migration patterns in avian and mammalian embryos, based on recent progress in understanding the expression and activity of receptor tyrosine kinases during embryogenesis. Distinct subpopulations of crest‐derived cells express specific receptor tyrosine kinases while residing in a migration staging area. We postulate that the differential expression of receptor tyrosine kinases by specific subpopulations of neural crest cells allows them to respond to localized growth factor ligand activity in the embryo. Thus, the migration pathway taken by neural crest subpopulations is determined by their receptor tyrosine kinase response to the differential localization of their cognate ligan

ISSN:0265-9247    

DOI:10.1002/bies.950190411

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

年代:1997

数据来源: WILEY