bluuebunny/crossref_metadata_2025_split huggingface dataset:
What's new: To boldly glow…. Applications of laser scanning confocal microscopy in developmental biology
Authors: Paddock Stephen W. 
Published: February 2005

AbstractThe laser scanning confocal microscope (LSCM)LSCM: laser scanning confocal microscope; FISH: fluorescence in situ hybridisation; DiO6: 3,3′‐dihexyloxacarbocyanine iodide; NBD‐ceramide: 6‐((N‐(7‐nitrobenz‐2‐oxa‐1,3‐diazol‐4‐yl)amino)‐caproyl)sphingosine; DiO: 3,3′‐dioctadecyloxacarbocyanine perchlorate; DiI: 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethyl‐indocarbocyanine perchlorate; CCD: charge‐coupled device; DIC: differential interference contrast; FURA2: (‐(2‐(5‐carboxyoxazol‐2‐yl)‐6‐aminobenzofuran‐5‐oxy)‐2‐)2′‐amino‐5′‐methylphenoxy)‐ethane‐N,N,N′,N′‐tetraacetic acid, sodium salt);BCECF: 2′,7′‐bis‐(carboxyethyl)‐5‐(and‐6‐)‐carboxyfluorescein;fluo‐3: 1‐(2‐amino‐5‐(2,7‐dichloro‐6‐hydroxy‐3‐oxo‐3H‐xanthen‐9‐yl)‐2‐(2′amino‐5′‐methylphenoxy)‐ethane‐N,N,N′,N′,‐tetraacetic acid, ammonium salt; DAPI: 4′,6‐diamidino‐2‐phenylindole, dihydrochloride; PET: positron emission tomogrophy; CT: computer‐assisted tomogrophy; CiD: cubitus interruptus dominus; MRC: Medical Research Council; TOTO‐1: benzothiazolium‐4‐quinolinium dimer; YOYO‐1: benzoxazolium‐4‐quinolinium dimer; ex.: excitation wavelength; em.: emission wavelength.
is now established as an invaluable tool in developmental biology for improved light microscope imaging of fluorescently labelled eggs, embryos and developing tissues. The universal application of the LSCM in biomedical research has stimulated improvements to the microscopes themselves and the synthesis of novel probes for imaging biological structures and physiological processes. Moreover the ability of the LSCM to produce an optical series in perfect register has made computer 3‐D reconstruction and analysis of light microscope images a practical option.
Cellular mechanisms of signal transduction for neurotrophins
Authors: Saltiel Alan R. , Decker Stuart J. 
Published: February 2005

AbstractThe molecular cloning of new neuroactive growth factors and their receptors has greatly enhanced our understanding of important interactions among receptors and singnaling molecules. These studies have begun to illuminate some of the mechanisms that allow for specificity in neuronal signaling. Model cell systems, such as the PC‐12 pheochromocytoma cell line, express receptors for these different neurotirophic factors, leading to comparisons of signaling pathways for these factors. Upon binding their ligands, these receptors undergo phosphorylation on tyrosine residues, which directs their interaction with signaling proteins containing src homology (SH2) domains, sequences that mediate associations with tyrosine‐phosphorylated proteins. These SH2 proteins translate the tyrosine kinase activity of receptors into downstream events that result in the specific cellular response. Investigations such as these have revealed that molecular specificity in signaling pathways may arise from combinatorial diversity in interactions between receptors and key regulatory proteins.
Hormones, neuroblasts and the adult insect
Authors: Shepherd David 
Published: February 2005

AbstractInsect neurogenesis has been subjected to extensive study and as a result is regarded as being well understood. It is, therefore, all the more surprising when a fundamentally novel aspects of the process is uncovered. Until recently it was thought that the production of central neurons ceased before the emergence of the adult. Recently, however, Cayre et al. have shown that neurogenesis also occurs in the adult brain. Their studies also show that the rate at which adult neuroblasts divide is controlled by hormones, suggesting that hormones may play a more important role in regulating neurogenesis than previously suspected.
A pattern confirmed and refined – synaptic, nonsynaptic and parasynaptic exocytosis
Authors: Golding David W. 
Published: February 2005

AbstractNeurons are now known to produce a variety of types of chemical transmitters. Classical transmitters are stored within synaptic vesicles which undergo synaptic exocytosis in association with presynaptic thickenings. The larger, dense‐cored secretory granules present in most neurons contain neuropeptides and mainly discharge their contents at morphologically undifferentiated (i.e.nonsynaptic) sites. The synaptic character of vesicle discharge enables transmitters to exercise a highly focal action, whereas nonsynaptic release probably relates to the slow rate of degradation of many neuropeptides and their consequent widespread diffusion and sphere of action. However, one variant of the basic pattern, involving the restriction of granule discharge to areas of the terminal plasmalemma situated adjacent to the postsynaptic cells (i.e. a parasynaptic configuration), enables a degree of targeted peptide discharge to be achieved. The diversity of patterns of neural exocytosis adds a further dimension to the complexity of nervous function.
Roadblocks and detours during DNA replication: Mechanisms of mutagenesis in mammalian cells
Authors: Naegeli Hanspeter 
Published: February 2005

AbstractMutations in specific genes result in birth defects, cancer, inherited diseases or lethality. The frequency with which DNA damage is converted to mutations increases dramatically when the cellular genome is replicated. Although DNA damage poses special problems to the fidelity of DNA replication, efficient mechanisms exist in mammalian cells which function to replicate their genome despite the presence of many damaged sites. These mechanisms operate in either error‐prone or error‐free modes of DNA synthesis, and frequently involve DNA strand‐pairing reactions. Genetic studies in yeast and other eukaryotes suggest that replication through DNA damage is highly regulated and catalysed by complex biochemical machineries composed of many specialised gene products. Knowledge of the molecular details by which such factors facilitate the replication of damaged DNA in mammalian cells should reveal basic rules about how DNA damage induces mutagenesis and carcinogenesis.
Mitosis
Authors: Earnshaw William C. , Pluta Ann F. 
Published: February 2005

AbstractWithin the last decade, the study of mitosis has evolved into a multidisciplinary science in which findings from fields as diverse as chromosome biology and cytoskeletal architecture have converged to present a more cohesive understanding of the complex events that occur when cells divide. The largest strides have been made in the identification and characterization of regulatory enzymes (kinases and phosphatases) that modulate mitotic activity, as well as a number of the proteins and structural components (spindle, chromosomes, nuclear envelope) which carry out the mitotic instructions. One emerging theme appears to be that molecular signalling, which can involve modification of components (such as phosphorylation) or even their specific destruction, monitors the state of the mitotic cell at all stages. One of the major challenges for the future will be the identification of addititonal targets of the signalling machinery, as well as new regulatory components and their targets on the chromosomes, on the spindle, and at the cleavage furrow.
Transcription by RNA polymerase II: A process linked to DNA repair
Authors: Chalut Christian , Moncollin Vincent , Egly Jean Marc 
Published: February 2005

AbstractThe proteins that are implicated in the basal transcription of protein coding genes have now been identified. Although little is known about their function, recent data demonstrate the ability of these proteins, previously called class II transcription factors, to participate in other reactions: TBP, the TATA‐box binding factor, is involved in class I and III transcription, while TFIIH has been shown to possess components that are involved in the DNA repair mechanism. The involvement of some if not all of the TFIIH subunits in transcription and repair may explain the heterogeneity of the various and sometimes completely unrelated symptoms observed in xeroderma pigmentosum, Cockayne Syndrome and trichothiodystrophy disorders.
Advances in immunology
Authors: Flanik Martin F. 
Published: February 2005

AbstractMuch was accomplished in the last decade in understanding how the adaptive immune system evolved to combat pathogens. Essential features of antigen presentation and T lymphocyte recognition were decipherd, setting the stage for further studies that elucidated basic elements of lymphocyte differentiation (including positive and negative selection during lymphocyte ontogeny) and the major interactions that occur among cells in secondary lymphoid organs in an ongoing immune response. The major challenges of today are found in the burgeoning fields of programmed cells death, enzymology of recombination and somatic mutation, development of memory, and the recognition of pathogens by unconventional lymphocytes.
The molecular basis for dominant yellow agouti coat color mutations
Authors: Perry William L. , Copeland Neal G. , Jenkins Nancy A. 
Published: February 2005

AbstractAgouti expression during the middle portion of the mouse hair growth cycle induces melanocytes to synthesize yellow instead of black pigment, generating black hairs with a yellow band. Dominant agouti alleles increase the amount of yellow pigment in the coat and are associated with pleiotropic effects including obesity, diabetes and increased tumor susceptibility. Four dominant agouti alleles (Aiapy, Aiy, Asy and Avy) were recently shown to result from insertions that cause ubiquitous expression of chimeric transcripts encoding a wild‐type agouti protein(1,2). Three insertions were identified as intracisternal A‐particles, which helps explain the variable coat colors and parental imprinting effects associated with some dominat agouti alleles.
Subcellular localization and trafficking of the GLUT4 glucose transporter isoform in insulin‐responsive cells
Authors: Holman Geoffrey D. , Cushman Samuel W. 
Published: February 2005

AbstractThe rate‐limiting step in the uptake and metabolism of Dglucose by insulin target cells is thought to be glucose transport mediated by glucose transporters (primarily the GLUT4 isoform) localized to the plasma membrane. However, subcellular fractionation, photolabelling and immunocytochemical studies have shown that the pool of GLUT4 present in the plasma membrane is only one of many subcellular pools of this protein. GLUT4 has been found in occluded vesicles at the plasma membrane, clathrin‐coated pits and vesicles, early endosomes, and tubulo‐vesicular structures; the latter are analogous to known specialized secretory compartments. Tracking the movement of GLUT4 through these compartments, and defining the mechanism and site of action of insulin in stimulating this subcellular trafficking, are major topics of current investigation. Recent evidence focuses attention on the exocytosis of GLUT4 as the major site of insulin action. Increased exocytosis may be due to decreased retention of glucose transporters in an intracellular pool, or possibly to increased assembly of a vesicle docking and fusion complex. Although details are unknown, the presence in GLUT4 vesicles of a synaptobrevin homologue leads us to propose that a process analogous to that occurring in synaptic vesicle trafficking is involved in the assembly of GLUT4 vesicles into a form suitable for fusion with the plasma membrane. Evidence that the pathways of signalling from the insulin receptor and of GLUT4 vesicle exocytosis may converge at the level of the key signalling enzyme, phosphatidylinositol 3‐kinase, is discussed.
Model phylogenies to explain the real world
Authors: Harvey Paul H. , Holmes Eddie C. , Nee Sean 
Published: February 2005

AbstractPhylogenetic trees based on gene sequence data contain information about the evolutionary processes responsible for their genesis. Methods have now been developed which help to reveal those processes. The methods are based on simple models of evolutionary change but, when applied across individuals in a population, rather than across species in a higher‐level taxon, they can reveal the past history of population change. Examples from salamanders and viruses are used to illustrate how the past history of changes in speciation rate and the origin of epidemics can be inferred in the absence of fossil material or historical documentation.
Specificity in splicing
Authors: Holliday Robin , Murray Vincent 
Published: February 2005

AbstractConsiderable information about the process of premRNA splicing has accmulated, but the mechanism by which highly accurate splicing is achieved is unresolved. Fifteen years ago we proposed that accuracy in splicing might depend on small RNA molecules (splicer RNAs) which hybridise across adjacent exon termini, or intron termini. Gene expression, including alternative splicing, could be controlled by the transcription of specific splicer RNA genes. We re‐assess our model here, in the light of subsequent developments.
Leech segmentation: A molecular perspective
Authors: Shankland Marty 
Published: February 2005

AbstractA variety of leech homeobox genes have been identified by homology with genes that are known to bring about the regionalization and segmentation of the anteroposterior body axis in other organisms. Embryonic expression patterns suggest a number of interphyletic similarities in the way that these genes are utilized. However, several interesting differences have also been observed. In particular, transplantation experiments in the leech embryo have shown that axially aligned patterns of homeobox gene expression are not specified by a global pattern of positional cues. Rather, the leech independently establishes anteroposterior patterns of gene expression in each of five discrete stem cell lineages, and these patterns are brought into their final alignment through a process of morphogenetic assembly.
Bee vision of pattern and 3D. The Bidder Lecture 1994
Authors: Horridge Adrian 
Published: February 2005

AbstractInsect vision is nothing if not active. The regular head movements, called saccades, enable the fly Drosophila to keep a straight path in flight despite inequalities in the thrust of the wings. Using their own motion, bees in flight measure the ranges of nearby objects. A long history of research shows that bees discriminate visually in ways that depend on their activity or task, so we must distinguish between vision during flying, fixating or hovering and landing.Bees return again and again for a reward of sugar solution and use their eyes to find their way. In an apparatus that makes them discriminate between two simulataneously visible but regularly interchanged targets, seen at a distance of 27 cm, bees are able to distinguish a remarkable number of simple patterns, but they fail in certain critical cases. The results can be explained with the hypothesis that bees have several broadly tuned overlapping filters with large fields that respond to the predominant orientation in a region of the image, and others for radial and circular patterns. Together with colour, these filters are independent of range. Bees prefer to use landmarks where they can, then global pattern at the largest scale, and lastly the detail around the goal. The way that discrimination of one visual feature is independent of other variables can be explained by models analogous to the colour triangle in colour discrimination.
Cell polarity and the mechanism of asymmetric cell division
Authors: Way Jeffrey C. , Wang Lili , Run Jin‐Quan , Hung Ming‐Shiu 
Published: February 2005

AbstractDuring development one mechanism for generating different cell types is asymmetric cell division, by which a cell divides and contributes different factors to each of its daughter cells. Asymmetric cell division occurs through out the eukaryotic kingdom, from yeast to humans. Many asymmetric cell divisions occur in a defined orientation. This implies a cellular mechanism for sensing direction, which must ultimately lead to differences in gene expression between two daughter cells. In this review, we describe two classes of molecules: regulatory factors that are differentially expressed upon asymmetric cell division, and components of a signal transduction pathway that may define cell polarity. The lin‐11 and mec‐3 genes of C. elegans, the Isl‐1 gene of mammals and the HO gene of yeast, encode regulatory factors that determine cell type of one daughter after asymmetric cell division. The CDC24 and CDC42 genes of yeast affect both bud positioning and orientation of mating projections, and thus may define a general cellular polarity. We speculate that molecules such as Cdc24 and Cdc42 may regulate expression of genes such as lin‐11, mec‐3, Isl‐1 and HO upon asymmetric cell division.
A parallel between development and evolution: Germ cell recruitment by the gonads
Authors: Denis Herman 
Published: February 2005

AbstractIn gonad‐bearing animals gametogenesis can be divided into three main phases. During embryonic development the primordial gem cells move towards the gonadal primordia. A long, intra‐gonadal phase follows during which the germ cells grow and differentiate. Mature germ cells are finally released from the gonads and brought to the exterior. Thus, germ cells are successively motile, non‐motile and motile again. This complex life history is given here a simple evolutionary interpretation. The basic assumption is that primitive Metazoa already had germ cells, but no gonads to harbour them. Higher animals acquired gonads, which sequestered the germ cells, thus creating the temporary confinement experienced by germ cells in most present‐day Metazoa. This evolutionalry scheme may explain why several steps of germ cell differentation are totally or partially independent of the gonads. These steps presumably existed in primitive, gonad‐free Metazoa, and conserved their autonomy in higher animals.
Giant leap for p53, small step for drug design
Authors: Anderson Mary E. , Tegtmeyer Peter 
Published: February 2005

AbstractWe review the findings of Cho et al.(1) on the crystal structure of a p53 tumor suppressor‐DNA complex. The core DNA binding domain of p53 folds into a structure termed a β‐sandwich, which organizes two loops and a loop‐sheet‐helix structure on one surface of p53 to interact with the consensus DNA recognition sequence of p53. These structures help to explain the functions of wild‐type p53 and the effects of tumor‐associated mutations on p53 DNA binding, transactivation and suppression of cellular proliferation.
The formation and functioning of yeast mitotic spindles
Authors: Masuda Hirohisa 
Published: February 2005

AbstractThe mitotic spindle contains the machinery responsible for sister chromatid segregation. It is composed of a complex and dynamic array of microtubules, which are nucleated from the spindle poles. Studies of yeast spindle functions by molecular genetic analysis and by in vitro functional analysis have identified proteins that are mitosis‐specific and present at very low concentrations in the cell, and have revealed the molecular bases of several processes required for the formation and functioning of the mitotic spindle. Here I review the current knowledge of the processes that are common to most eukaryotes: microtubule nucleation at the spindle poles, bipolar spindle assembly, maintenance of the spindle structure, chromosome attachment to the spindle and chromosome separation on the spindle.
Are there DNA damage checkpoints in E. coli?
Authors: Bridges Bryn A. 
Published: February 2005

AbstractThe concept of regulatory ‘checkpoints’ in the eukaryotic cycle has proved to be a fruitful one. Here, its applicability to the bacterial cell cycle is examined. A primitive DNA damage checkpoint operates in E. coli such that, after exposure to ultraviolet light, while excision repair occurs, chromosome replication continues very slowly with the production of discontinuous daughter strands. The slower the rate of excision of photoproducts, the greater the delay before the normal rate of DNA replication is restored, the additional time for repair ensuring that normal survival is maintained. A model is proposed in which replication rate is controlled by the ratio of RecAcoated to uncoated single stranded regions of DNA in the replication fork. There are also two cell division inhibitors SulA (=SfiA) and SfiC under the control of the SOS system and sensitive to DNA damage, but they are irrelevant to the survival of wild‐type bacteria under normal conditions. In strains where SulA and SfiC do not operate, inhibition is not influenced by the rate of excision repair and so fails one of the criteria for a DNA damage checkpoint, namely the monitoring of the DNA for the level of residual damage.
Moving up the hierarchy: A hypothesis on the evolution of a genetic sex determination pathway
Authors: Wilkins Adam S. 
Published: February 2005

AbstractA hypothesis on the evolutionary origin of the genetic pathway of sex determination in the nematode Caenorhabditis elegans is presented here. It is suggested that the pathway arose in steps, driven by frequency‐dependent selection for the minority sex at each step, and involving the sequential acquisition of dominant negative, neomorphic genetic switches, each one reversing the action of the previous one. A central implication is that the genetic pathway evolved in reverse order from the final step in the hierarchy up to the first. The possible applicability of the model to the other well‐characterized sex determination pathway, that of Drosophila melanogaster, and to sex determination in mammals, is discussed, along with some potential implications for pathway evolution in general. Finally, the specific molecular and population genetic questions that the model raises are described and some tests are proposed.
Left‐right asymmetry in vertebrates
Authors: Almirantis Y. 
Published: February 2005

AbstractA mechanism for the generation of the morphological left‐right asymmetry in higher organisms is proposed, based on the idea that chirality at the molecular level is the primordial source for macroscopic asymmetry. This mechanism accounts for a variety of experimental results on artificial production of situs inversus and fits well with mutations in mice causing visceral transposition.
Eukaryotic DNA methyltransferases – structure and function
Authors: Adams Roger L. P. 
Published: February 2005

AbstractMethylation of DNA plays an important role in the control of gene expression in higher eukaryotes. This is largely achieved by the packaging of methylated DNA into chromatin structures that are inaccessible to transcription factors and other proteins. Methylation involves the addition of a methyl group to the 5‐position of the cytosine base in DNA, a reaction catalysed by a DNA (cytosine‐5) methyltransferase. This reaction occurs in nuclear replication foci where the chromatin structure is loosened for replication, thereby allowing access to methyltransferases. Partly as a result of their recognising the presence of a methylcytosine on the parental strand following replication, these large enzymes are able to maintain the distribution of methyl groups along the DNA of somatic cells and, thereby, maintain tissue‐specific patterns of gene expression.
Nucleosomal anatomy – where are the histones?
Authors: Pruss Dmitry , Hayes Jeffrey J. , Wolffe Alan P. 
Published: February 2005

AbstractThe recent surge of discoveries concerning the structural organization of nucleosomes, together with genetic evidence of highly specialized roles for the histones in gene regulation, have brought a renewed need for a detailed understanding of nucleosomal anatomy. Here we review recent structural advances leading to a new level of understanding of the nucleosome and chromatin fibre structure. We discuss the problems and challenges for existing models of chromatin structure and, in particular, consider how linker histones may bind within the nucleosome, together with the implications of their association for the structure of the chromatin fibre.