bluuebunny/crossref_metadata_2025_split huggingface dataset:
Directed positioning of nuclei in living Paramecium tetraurelia: Use of the laser optical force trap for developmental biology
Authors: Aufderheide Karl J. , Du Qing , Fry Edward S. 
Published: May 2005

AbstractWe have constructed a laser optical force trap (“laser tweezers”) by coupling an Nd:YAG laser to an optical microscope with a high numerical aperture objective. The laser beam (approximately 0.1 W power) is focused to a diffraction‐limited spot at the specimen plane of the objective: the wavelength chosen (1,064 nm) is not strongly absorbed by most biological materials and is thus not ablative. Because the intensity of the laser beam increases towards the center of the focal spot, small particles brought near the spot will be attracted to the center and held there. Movement of the laser beam will tend to move any trapped particles with it. The laser tweezers can permit precise, nondestructive repositioning of small structures inside a living cell, without recourse to micromanipulators. Initial work has involved the use of laser tweezers on cells of Paramecium tet‐raurelia held by a rotocompressor. We have been able to trap and reposition small organelles, especially the highly refractile structures known as crystals. Using a trapped crystal as a “tool”, we have been able to push micronuclei and other structures for many micrometers to virtually any desired location in a cell. In spite of extended exposure of specific structures and of individual cells to the laser beam, no damage has been detectible. Exposed cells, which were removed from the rotocompres‐sor and cultured, showed complete viabilty. The laser tweezers technique shows tremendous potential for applications to the study of many fundamental cellular and developmental phenomena in paramecia and other ciliates. For example, we intend to use this technique to investigate temporal and spatial characteristics of nuclear determining regions during sexual reorganization in Paramecium. © 1992 Wiley‐Liss, Inc.
Isolation of the Lembadion‐factor, A morphogenetically active signal, that induces Euplotes cells to change from their ovoid form into a larger lateral winged morph
Authors: Kusch Jürgen , Heckmann Klaus 
Published: May 2005

AbstractA morphogenetically active substance released by the predatory ciliate Lem‐badion bullinum is recognized by ciliates of the genus Euplotes, which are potential prey organisms of Lembadion. The substance (L‐factor) induces cells of the genus Euplotes to become less compact, which reduces their likelihood of becoming engulfed. Under the influence of this Lembadion‐ derived signal, E. octocarinatus develops extended wings and dorsal and ventral ridges and transforms within a few hours from its typical ovoid morph into an enlarged circular morph. This takes place without cell division. We have isolated the L‐factor and report that it is a protein with a mass of 31,500 Da. The factor has been purified to chromatographic and electrophoretic homogeneity and was found to be active at concentrations as low as 10−12 mol/L. © 1992 Wiley‐Liss, Inc.
Generation of Minute phenotypes by a transformed antisense ribosomal protein gene
Authors: Patel Rekha , Jacobs‐Lorena Marcelo 
Published: May 2005

AbstractAntisense RNAs have been used for gene interference experiments in many cell types and organisms. However, relatively few experiments have been conducted with antisense genes integrated into the germ line. In Drosophila reduced ribosomal protein (r‐protein) gene function has been hypothesized to result in a Minute phenotype. In this report we examine the effects of antisense r‐protein 49 expression, a gene known to correspond to a Minute mutation An antisense rp49 gene driven by a strong and inducible promoter was transformed into the Drosophila germ line. Induction of this gene led to the development of flies with weak Minute phenotypes and to the transient arrest of oogenesis. Parameters that may affect the success of antisense gene inactivation are discussed. © 1992 Wiley‐Liss, Inc.
Broad‐Complex function during oogenesis in Drosophila melanogaster
Authors: Huang Ruea‐Yea , Orr William C. 
Published: May 2005

AbstractThe Broad‐Complex (BR‐C) appears to encode factors that mediate ecdysone effects during the larva‐adult transition. The main goal of this study was to gain insight into what roles the BR‐C might play during oogenesis. The main findings are as follows. First, as determined by heteroallele studies and clonal analysis, de12 is a somatic line mutation that appears to fall into the broad domain of the BR‐C. Second, the de12 mutation is associated with the insertion of the gypsy transposon at position 169.5 (Chao and Guild, Embo J, 1986, 5:143–150) in the BR‐C domain. In its new context this gypsy element exhibits ovarianspecific activation. Both this gypsy activation and the de12 phenotype are partially suppressible by su(f) and su(Hw). Third, we have identified a set of transcripts that cross‐hybridize with BR‐C sequence spanning the gypsy insertion site (166–179). There are significant differences in these cross‐hybridizing species, both in size and relative abundance, between de12 and its parent strain. Finally we have determined that in de12 there is a premature arrest of chorion gene amplification in the late stages of oogenesis. © 1992 Wiley‐Liss, Inc.
Sequential up‐regulation of thyroid hormone β receptor, ornithine transcarbamylase, and carbamyl phosphate synthetase mRNAs in the liver of Rana catesbeiana tadpoles during spontaneous and thyroid hormone‐induced metamorphosis
Authors: Helbing Caren , Gergely Gus , Atkinson Burr G. 
Published: May 2005

AbstractDuring both spontaneous and thyroid hormone (TH)‐induced metamorphosis, the Rana catesbeiana tadpole undergoes postembryonic developmental changes in its liver which are necessary for its transition from an ammonotelic larva to a ureotelic adult. Although this transition ultimately results from marked increases in the activities and/or de novo synthesis of the urea cycle enzymes, the precise molecular means by which TH exerts this tissue‐specific response are presently unknown. Recent reports, using RNA from whole Xenopus laevis tadpole homogenates and indirect means of measuring TH receptor (TR) mRNAs, suggest a correlation between the up‐regulation of TRβ‐mRNAs and the general morphological changes occurring during amphibian metamorphosis. To assess whether or not this same relationship exists in a TH‐responsive tissue, such as liver, we isolated and characterized a cDNA clone containing the complete nucleotide sequence for a R. catesbeiana urea cycle enzyme, ornithine transcarbamylase (OTC), as well as a genomic clone containing a portion of the hormone‐binding domain of a R. catesbeiana TRβ gene. Through use of these homologous sequences and a heterologous cDNA fragment encoding rat carbamyl phosphate synthetase (CPS), we directly determined the relative levels of the TRβ, OTC, and CPS mRNAs in liver from spontaneous and TH‐induced tadpoles. Our results establish that TH affects an up‐regulation of mRNAs for its own receptor prior to up‐regulating CPS and OTC mRNAs. Moreover, results with cultured tadpole liver demonstrate that TH, in the absence of any other hormonal influence, can affect an up‐regulation of both the TRβ and OTC mRNAs. © 1992 Wiley‐Liss, Inc.
The genetic program for preimplantation development
Authors: Kidder Gerald M. 
Published: May 2005

AbstractThis review summarizes information on accumulation profiles of individual gene transcripts in preimplantation development. Most of the information is from the mouse, but some data from other species are reviewed as well. The principal finding is that the transcription of most genes is not temporally linked with any of the three morphogenetic transitions (compaction, cavitation, and blastocoel expansion) that characterize this period. Most genes that are expressed during pre‐implantation development of the mouse are already being transcribed in the 4‐cell stage, and some clearly begin as early as the 2‐cell stage. Once activated, a gene continues to be transcribed at least into the blastocyst stage, resulting in continuous mRNA accumulation. Thus the pattern of gene transcription established at the time of genomic activation in the 2‐cell stage is perpetuated into the blastocyst, with a few additions along the way. This information is interpreted in light of previous findings concerning the sensitivity of morphogenetic transitions to inhibition of gene expression. The lack of a clear relationship between the timing of expression of most genes and the schedule of morphogenesis leads one to conclude that temporal regulation is imposed downstream of transcription and translation. This conclusion is substantiated by a consideration of factors controlling the events of compaction. © 1992 Wiley‐Liss, Inc.
Sequence and expression of IMP‐L1, an ecdysone‐inducible gene expressed during Drosophila imaginal disc morphogenesis
Authors: Natzle Jeanette E. , Robertson Jeannette P. , Majumdar Arindam , Vesenka Gwendolyn D. , Enlow Brett , Clark Katherine E. 
Published: May 2005

AbstractDrosophila imaginal discs are induced by the steroid hormone 20‐hydroxy‐ecdysone to initiate morphogenesis leading to formation of the adult appendages and thoracic epidermis at the end of the third larval instar. Ecdysone‐dependent transcriptional activation of a set of genes that encode imaginal disc transcripts found on membrane‐bound polysomes precedes and may be responsible for some aspects of the cellular changes that mediate epithelial morpho‐genesis in this system. A 1.35 kb transcript from one of these genes, IMP‐L1, is first observed in vivo at or just prior to pupariation, as ecdysone titers are peaking and beginning to decline. Expression is initiated in proximal areas of the antennal disc, later spreading to a more widespread but nonuniform distribution throughout other thoracic imaginal discs. IMP‐L1 is not, however, expressed in other ecdysone target tissues such as salivary glands or fat body. The IMP‐L1 gene encodes a novel protein product containing a signal peptide, a possible transmembrane domain, two highly charged domains and a proline rich C‐terminal domain. We suggest that the delayed timing of expression of this secondary response gene is necessary for proper ordering of cellular events associated with disc morphogenesis. © 1992 Wiley‐Liss, Inc.
Cloning and sequence comparison of the mouse, human, and chicken engrailed genes reveal potential functional domains and regulatory regions
Authors: Logan C. , Hanks M. C. , Noble‐Topham S. , Nallainathan D. , Provart N. J. , Joyner A. L. 
Published: May 2005

AbstractWe have isolated and characterized genomic DNA clones for the human and chicken homologues of the mouse En‐1 and En‐2 genes and determined the genomic structure and predicted protein sequences of both En genes in all three species. Comparison of these vertebrate En sequences with the Xenopus En‐2 (Hemmati‐Brivanlou et al., 1991) and invertebrate engrailed‐ like genes showed that the two previously identified highly conserved regions within the En protein [reviewed in Joyner and Hanks, 1991] can be divided into five distinct subregions, designated EH1 to EH5. Sequences 5′ and 3′ to the predicted coding regions of the vertebrate En genes were also analyzed in an attempt to identify cis‐acting DNA sequences important for the regulation of En gene expression. Considerable sequence similarity was found between the mouse and human homologues both within the putative 5′ and 3′ untranslated as well as 5′ flanking regions. Between the mouse and Xenopus En‐2 genes, shorter stretches of sequence similarity were found within the 3′ untranslated region. The 5′ untranslated regions of the mouse, chicken and Xenopus En‐2 genes, however, showed no similarly conserved stretches. In a preliminary analysis of the expression pattern of the human En genes, En‐2 protein and RNA were detected in the embryonic and adult cerebellum respectively and not in other tissues tested. These patterns are analogous to those seen in other vertebrates. Taken together these results further strengthen the suggestion that En gene function and regulation has been conserved throughout vertebrate evolution and along with the five highly conserved regions within the En protein, raise an interesting question about the presence of conserved genetic pathways. © 1992 Wiley‐Liss, Inc.
Mutations in the glutamine synthetase I (gsI) gene produce embryo‐lethal female sterility in Drosophila melanogaster
Authors: Caggese Corrado , Caizzi Ruggiero , Barsanti Paolo , Bozzetti Maria Pia 
Published: May 2005

AbstractA female‐sterile mutation (fs(2) PM11‐19) was recovered in a screen for P‐M hybrid dysgenesis induced mutations uncovered by a deletion of region 21B and was identified as an allele of the gene encoding the Drosophila glutamine synthetase I (GSI) mitochondrial isozyme.Molecular analysis has shown that fs(2)PM11‐19 contains a 5 kb insert within 500 bp upstream of the transcriptional start site of the gsI gene. Mutant flies have extremely low levels of gsl transcription and GSI activity. A pre‐existing deficiency (Df(2L) netpm1) with a breakpoint near the transcription start site was also found to be a female‐sterile allele of gsl.All eggs laid by PM11‐19 homozygous females, as well as by females heterozygous for this mutation and a deletion or any of several recessive lethal alleles of the gsl gene, fail to hatch. We conclude that an adequate level of maternally supplied GSI activity is necessary in the early stages of Drosophila embryonic development. © 1992 Wiley‐Liss, Inc.
Use of a yeast site‐specific recombinase to generate embryonic mosaics in Drosophila
Authors: Dang Duyen T. , Perrimon Norbert 
Published: May 2005

AbstractAn efficient method for generating embryonic mosaics using a yeast site‐specific recombinase (FLP), under the control of a heat shock promoter, is described. FLP‐recombinase can promote mitotic exchange between homologous chromosomes that contain FRT (FLP Recombination Target) sequences. To demonstrate the efficiency of FLP‐recombinase to generate embryonic mosaics, clones of the recessive and cell autonomous mutation armadillo (arm), detected by their ability to differentiate ectopic denticles in the naked cuticle of each abdominal segment, have been induced. We have analyzed the parameters of FLP‐recombinase induced embryonic mitotic recombination and have demonstrated that clones can be efficiently induced during the postblastoderm mitotic divisions. We discuss applications of this technique for the analyses of the roles of various mutations during embryonic patterning. © 1992 Wiley‐Liss, Inc.
Characterization of REC104, a gene required for early meiotic recombination in the yeast Saccharomyces cerevisiae
Authors: Galbraith Anne M. , Malone Robert E. 
Published: May 2005

AbstractThe REC104 gene was initially defined by mutations that rescued the inviability of a rad52 spo13 haploid strain in meiosis. We have observed that rec104 mutant strains undergo essentially no induction of meiotic gene conversion, and we have not been able to detect any meiotic crossing over in such strains. The REC104 gene has no apparent role in mitosis, since mutations have no observable effect on growth, mitotic recombination, or DNA repair. The DNA sequence of REC104 reveals that it is a previously unknown gene with a coding region of 549‐bp, and genetic mapping has localized the gene to chromosome VIll near FUR1. Expression of the REC104 gene is induced in meiosis, and it appears that the gene is not transcribed in mitotic cells. Possible roles for the REC104 gene product in meiosis are discussed. © 1993 Wiley‐Liss, Inc.
Searching for synaptonemal complex proteins and their genes
Authors: Moens Peter B. , Spyropoulos Barbar , Dobson Melanie , Karaiskakis Angelo , Pearlman Ronald E. 
Published: May 2005

AbstractAs an alternative to the production and use of monoclonal antisynaptonemal complex (SC) antibodies to isolate SC genes, we have explored the use of polyclonal anti‐SC antibodies to identify SC genes from a cDNA expression library. The method proved relatively simple, reliable, and fast and has yielded two SC genes. A homologue of one of these genes from a different species has previously been isolated in another laboratory. © 1993 Wiley‐Liss, Inc.
There are two mechanisms of achiasmate segregation in Drosophila females, one of which requires heterochromatic homology
Authors: Hawley R. Scott , Irick Holly , Haddox Deana A. , Whitley Michelle D. , Arbel Tamar , Jang Janet , McKim Kim , Zitron Anne E. , New Christine , Childs Geoffrey , Lohe Allan 
Published: May 2005

AbstractThere are numerous examples of the regular segregation of achiasmate chromosomes at meiosis I in Drosophila melanogaster females. Classically, the choice of achiasmate segregational partners has been thought to be independent of homology, but rather made on the basis of availability or similarities in size and shape. To the contrary, we show here that heterochromatic homology plays a primary role in ensuring the proper segregation of achiasmate homologs. We observe that the heterochromatin of chromosome 4 functions as, or contains, a meiotic pairing site. We show that free duplications carrying the 4th chromosome pericentric heterochromatin induce high frequencies of 4th chromosome nondisjunction regardless of their size. Moreover, a duplication from which some of the 4th chromosome heterochromatin has been removed is unable to induce 4th chromosome nondisjunction. Similarly, in the absence of either euchromatic homology or a size similarity, duplications bearing the X chromosome heterochromatin also disrupt the segregation of two achiasmate X chromosome centromeres. Although heterochromatic regions are sufficient to conjoin nonexchange homologues, we confirm that the segregation of heterologous chromosomes is determined by size, shape, and availability. The meiotic mutation Axs differentiates between these two processes of achiasmate centromere coorientation by disrupting only the homology‐dependent mechanism. Thus there are two different mechanisms by which achiasmate segregational partners are chosen. We propose that the absence of diplotene‐diakinesis during female meiosis allows heterochromatic pairings to persist until prometaphase and thus to co‐orient homologous centromeres. We also propose that heterologous disjunctions result from a separate and homology‐independent process that likely occurs during prometaphase. The latter process, which may not require the physical association of segregational partners, is similar to those observed in many insects, in Saccharomyces cerevisiae and in C. elegans males. We also suggest that the physical basis of this process may reflect known properties of the Drosophila meiotic spindle. © 1993 Wiley‐Liss, Inc.
The independent stage‐specific expression of the 18‐kDa heat shock protein genes during microsporogenesis in Zea mays L
Authors: Atkinson Burr G. , Raizada Manish , Bouchard Robert A. , Frappier J. Roger H. , Walden David B. 
Published: May 2005

AbstractThe small (18‐kDa) heat shock proteins (hsps) of maize are encoded by a complex multigene family. In a previous report, we described the genetic information from cDNAs encoding two different members of the family. In this communication, we report the isolation and characterization of cDNA and genomic clones encoding information for a third member of this hsp family (c/gMHSP18–1). DNA fragments containing nucleotide sequences common to, or specific for, each of these characterized 18‐kDa genes were prepared and used as probes to assess the expression of these genes during microsporogenesis and development of the gametophyte in an inbred line of maize (Oh43). Our results demonstrate (1) that mRNA transcripts encoding the 18‐kDa hsps are expressed and/or accumulate during microsporogenesis, and (2) that genes encoding two of the characterized 18‐kDa hsps are expressed and/or accumulate independently, in a stage‐specific manner during microsporogenesis. These observations imply that the stage‐specific expression of particular 18‐kDa hsp genes results from gene‐specific regulation during microsporogenesis and gametophyte development rather than from an overall activation of the heat shock or stress response. © 1993Wiley‐Liss, Inc.
Expression of endogenous and microinjected hsp 30 genes in early Xenopus laevis embryos
Authors: Ali Adnan , Krone Patrick H. , Heikkila John J. 
Published: May 2005

AbstractIn the present study, we have examined the regulation of expression of a newly isolated member of the hsp 30 gene family, hsp 30C. Using RT‐PCR, we found that this gene was first heat‐inducible at the tailbud stage of development. We also examined the expression of two microinjected modified hsp 30C gene constructs in Xenopus embryos. One of the constructs had 404 bp of hsp 30C 5′‐flanking region, whereas the other had 3.6 kb. Both gene constructs had 1 kb of 3′‐flanking region. RT‐PCR assays were employed to detect the expression of these microinjected genes. The presence of extensive 5′‐ and 3′‐flanking regions of the hsp 30C gene did not confer proper developmental regulation, since heat‐inducible expression of both of the microinjected constructs was detectable at the midblastula stage. The premature expression of the microinjected hsp 30 gene was not a result of high plasmid copy number or the presence of plasmid DNA sequences. These results suggest that the microinjected genes contain all the cis‐acting DNA sequences required for correct heat‐inducible regulation but do not contain the elements required for the proper regulation of hsp 30 gene expression during development. It is possible that regulatory elements controlling the developmental expression of the hsp30 genes may reside upstream or downstream of the entire cluster. © 1993Wiley‐Liss, Inc.
The induction of pyruvate kinase synthesis by heat shock in Xenopus laevis embryos
Authors: Marsden M. , Nickells R. W. , Kapoor M. , Browder L. W. 
Published: May 2005

AbstractHeat‐shocked Xenopus embryos have an unusually complex heat shock response. The dominant heat shock protein (Hsp) has a relative molecular mass (Mr) of 62,000 D (Hsp62). Affinity‐purified IgGs against the glycolytic enzyme pyruvate kinase (PK; EC 2.7.1.40) specifically immunoprecipitated Hsp62 from extracts of embryos that had been heat‐shocked at 37°C for 30 min. Thus, Hsp62 and pyruvate kinase are immunologically cross‐reacting. Electrophoretic separation of PK isoforms suggests that heat‐shocked Xenopus embryos increase synthesis of an isoform of PK. Thermal denaturation studies suggest that this isoform has enhanced thermal stability. The identification of PK as an Hsp is discussed within the context of a physiological requirement for elevated levels of anaerobic glycolysis in heatstressed cells as a vital component of the acquisition of thermotolerance. © 1993Wiley‐Liss, Inc.