bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental changes in the sensitivity of Volvox to ultraviolet light
Authors: Baran George J. , Huskey Robert J. 
Published: May 2005

AbstractThe response of Volvox to ultraviolet irradiation was analyzed. Young individuals isolated from a synchronous culture were exposed to UV light (120 J/m2) and subjected to variable lenght periods of dark following irradiation. The major effect of the UV treatment was the inability of the gonidia present in the colonies at the time of irradiation to continue and complete the developmental program. Individuals show a heightened sensitivity to UV for a limited period immediately following inversion and are insensitive at other stages of development. The cytotoxic effect of UV during this interval is completely reversed by the immediate exposure to white light and is increased with longer periods of dark treatment prior to exposure to white light. The temporal profile of the sensitivity defines a smooth curve in which the maximal sensitivity occurs three hours after inversion. The response to higher doses of UV (up to 500 J/m2) is a nonlinear increase in cytotoxicity and is disproportionanately greater in those individuals just prior to the period of maximal sensitivity than those later in development. The results suggest that Volvox has at least two pathways for the repair of UV damage and that one of these, the principal dark repair pathway, is temporarily deficient in the gonidia of young individuals.
Germ line and somatic instability of a white mutation in Drosophila mauritiana due to a transposable genetic element
Authors: Haymer David S. , Marsh J. Lawrence 
Published: May 2005

AbstractA spontaneous white mutation recovered in Drosophila mauritiana is unstable and reverts to normal eye color at a frequency greater than 4 per 1,000 ×‐chromosomes. Germ line reversion occurs at a high rate in D. mauritiana males and in interspecific hybrid females, while the rate is depressed in D. mauritiana females. These events are not restricted to the germ line, as cases of variegated patterns of eye pigmentation, indicating somatic reversion, are recovered at a frequency comparable to that of the male germ line reversion rate. Germ line reversion events are genetically stable, while the somatic variegation patterns are not heritable. The patterns of eye pigment variegation produced suggests that reversion events are occurring throughout development. Whole genome DNA digests blotted and probed with the cloned D. melanogaster white gene indicate that this unstable white mutation in D. mauritiana is associated with an insertion of DNA that is lost upon reversion to wild type, indicating that this DNA insert is in fact a transposable element.
Complementation between alleles at the ovarian tumor locus of Drosophila melanogaster
Authors: King Robert C. , Mohler Dawson , Riley Shawn F. , Storto Patrick D. , Nicolazzo Peter S. 
Published: May 2005

AbstractThe (ovarian tumor) otu gene resides at 23.2 on the genetic map of the X chromosome and near 7F1 on the cytological map. This germ line‐expressed locus behaves as if it encodes a gene product which is required during certain steps in the transformation of oogonia into functional oocytes. On the basis of their ovarian morphologies 17 ethyl methane sulfonate (EMS)‐induced mutants have been distributed among three developmental classes as follows: quiescent (eight), oncogenic (four), and differentiated (five). The otu13 and otu14 alleles interact to yield fertile females, and many other heteroallelic combinations show partial complementation. Since many mutant alleles interact beneficially, the functional product of the otu gene may be a multimer. We conclude, from an analysis of heteroallelic interactions and dosage effects, that the abnormal phenotypes observed are graded consequences of reduced levels of functional gene product and that the minimum concentration required for development increases as oogenesis proceeds.
Developmental profiles of three embryo‐lethal maize mutants lacking leaf primordia: ptd*‐1130, cp*‐1418, and bno*‐747B
Authors: Sheridan William F. , Thorstenson Yvonne R. 
Published: May 2005

AbstractThe defective kernel (dek) mutants of maize are altered in both their embryo and endosperm development. Earlier studies have indicated that some of the dek mutants are unable to form shoot apical meristems or leaf primoirda. We have examined three embryo lethal dek mutants of this type, ptd*‐1130, cp*‐1418, and bno*‐747B, to obtain a developmental profile for each. Allelism tests show that these three mutants are not allelic. Embryos were examined in early, mid‐, and late kernel development as well as at kernel maturity by dissection and sectioning procedures and also at kernel maturity by scanning electron microscopy. All three mutants lag behind normal embryos in their rate of development. Embryos of ptd*‐1130 reached the transition stage by early kernel development and progressed no further but underwent cell enlargement and necrosis during late kernel development. Embryos of cp*‐1418 reached an early coleoptilar stage by midkernel development. They subsequently increased in size but did not form any leaf primordia. At kernel maturity, they no longer had a shoot apical meristem but often had a well formed root meristem. They appeared to remain healthy and did not become necrotic. Embryos of bno*747B reached the early coleoptilar stage by early kernel development but progressed no further. By kernel maturity, they had grown into masses of irregularly shaped embryonic tissue that no longer resembled any normal embryo stage but were not necrotic. None of these three mutants responded to attempts to support continued embryo development when cultured, but all three mutants formed callus on N6 and MS media supplemented with 2,4‐D. These results indicate that these mutants are all uniformly blocked at specific stages early in embryonic development, have different subsequent developmental fates, and represent three different genes performing unique functions that are essential for embryogenesis.
A comparison of genome modifications leading to genetic and epigenetic tumorous transformation in Nicotiana spp. tissue cultures
Authors: Durante Mauro , Geri Chiara , Buiatti Marcello , Ciomei Marina , Cecchini Edi , Martini Guido , Parenti Roberto , Giorgi Livio 
Published: May 2005

AbstractA single system is presented, where both genetic and epigenetic control of tumor induction can be studied at the same time. This system is offered by the amphidiploid tumorous hybrid Nicotiana glauca × N. langsdorffii, a nontumorous mutant of it and the nontumorous parent species N. glauca and N. langsdorffii. The aim of the present paper is to compare long‐term in vitro cultures of tumorous (genetic and habituated), and nontumorous strains, through the characterization of their genomes according to several physico‐chemical parameters. The data reported show that both qualitative and quantitative differences in DNA complexity are correlated with the tumorous transformation. Particularly, a high degree of mismatching between the DNAs of the tumorous and nontumorous hybrids and the lack, in the second genotype (nontumorous), of three DNA peaks in Ag+−Cs2SO4 analytical ultracentrifugation profile seem to support the hypothesis, suggested in a previous paper, of the presence, in the nontumorous mutant, of a gross chromosomal rearrangement, probably a deletion. Amplification and underreplication of specific sequences also seemed to be correlated with changes from the normal to the tumorous state, highly repetitive sequences being present in higher amounts in the normal strains and in the habituated N. glauca than in the case of the tumorous hybrid.Finally, DNA bound ion contents were found to be strikingly higher in tumorous than in nontumorous tissues. The results are discussed in the frame of the general hypothesis of high somatic genomic plasticity in plants.
Decreased methylation of the major mouse long interspersed repeated DNA during aging and in myeloma cells
Authors: Mays‐Hoopes Laura , Chao Wei , Butcher Henry C. , Huang Ru Chin C. 
Published: May 2005

AbstractSequences of DNA that hybridize on Southern blots with cloned EcoR1 1.3 kb (ER1) of long interspersed repeated sequence (L1Md) of mouse have been examined in genomic DNA of neonatal mice, livers and brains of adult mice (3, 10, 27, and 30 mo old), and the solid myeloma tumor MOPC‐315. The isoschizomers Hpa II (CCGG or mCCGG) and Msp I (CCGG or CmCGG) were used to assess methylation. We found that the L1Md sequence is fully methylated in young animals but demethylated in myeloma. Demethylation of L1Md sequence also occurred in aged animals. By scanning the autoradiogram, we found that approximately 8% of the 104–105 copies have been demethylated in 27‐mo‐old liver.
Epididymides of sex‐reversed XX mice lack the initial segment
Authors: LeBarr Deborah K. , Blecher Stan R. 
Published: May 2005

AbstractThe genetic factor Sxr causes sex reversal of chromosomally female (XX or XO) mice to phenotypic maleness by inducing development of testes that produce androgens. It has been considered that these sex‐reversed animals, called pseudomales, confirm the principle originally developed by Jost that adequate androgenization produces normal phenotypic maleness in mammals, irrespective of chromosomal sex. However, wepreviously discovered that the epididymis of sex‐reversed XX mice (pseudomales of genotype XXSxr) lacks EH 9 cells (epididymal head, cell type No. 9, the principal cell' of the initial segment). The purpose of the present study was to determine whether cell type EH 9 of XXSxr pseudomales is replaced by a principal cell of a different appearance, or whether the initial segment itself is actually absent. We made serial sections of entire epididymal heads and did microdissections to unravel the highly coiled epididymal duct. Using these two approaches, we studied the sequence of epididymal segments, and estimated lengths of the relevant portion of the epididymal duct; we found that the initial segment of XXSxr pseudomales is truly absent. This is the first report of a mutant genotype causing absence of a segment of the epididymis. The XXSxr mutant appears to be an exception to Jost's principle. This finding shows that, even in full androgenization, male phenotype may not always be independent of chromosomal sex.
Intron‐delay and the precision of expression of homoeotic gene products in Drosophila
Authors: Gubb D. 
Published: May 2005

AbstractIt is suggested that the time taken in transcribing the large introns within homoeotic transcription units will reduce the quantity of mature transcript synthesised per nuclear division cycle. This could provide an additional level of control that would affect the ratios of fate‐determining gene products to each other. Determination of regional fate depends on both the large domains of homoeotic genes and the small, serially repeated domains of segmentation genes. As a consequence, each row of cells along the anteroposterior axis of the embryo could be assigned a precise, and unique, fate. This precision is apparently not dependent on cell lineage discontinuities.
DNA methylation in vegetative and conjugating cells of a protozoan ciliate: Blepharisma japonicum
Authors: Salvini M. , Barone E. , Ronca S. , Nobili R. 
Published: May 2005

AbstractWe report here the presence of N6‐methyladenine (MeAde) in the macronuclear DNA (maDNA) of Blepharisma japonicum vegetative cells. We have further investigated the relationship between DNA methylation and cell union in cells activated for conjugation. Such activation was induced by treating cells of mating type I with complementary gamone 2. We found a reduction of about 24% of MeAde content in gamone‐treated cells ready for cell union. First indications of the presence and reduction of MeAde content came from electrophoresis of maDNA digested by appropriate restriction endonucleases. Chromatographic determination of the amount of methylated base by HPLC substantiated these observations. In vegetative cells, 1.576 ± 0.02% of total adenine was found to be methylated as opposed to 1.193 ± 0.04% in activated cells. The HPLC analysis of maDNA also revealed a peak with a retention time corresponding to that of 5‐hydroxymethyluracil, already found in some species of dinoflagellates. In that gamone treatment is correlated with a differential gene expression (indicated by a differential RNA and protein synthesis), our results suggest that there is a relationship between macronuclear genome activation and demethylation of maDNA. This is the first report of a correlation between gene activation and adenine demethylation in a eukaryotic organism.
A cytokinin mutant derived from cultured tobacco cells
Authors: Meins Frederick , Foster Rachel 
Published: May 2005

AbstractTissues cultured from the leaf lamina of wild‐type Nicotiana tabacum L. cv. “Havana 425” plants require an exogenous source of cytokinin for rapid growth. In contrast, leaf tissues of plants heterozygous or homozygous for the partially dominant, monogenic habituated leaf (H1‐1) trait, exhibit a cytokinin‐autotrophic phenotype in culture. Here we show that the H1 trait can arise in culture. Cytokinin autotrophic variants were obtained by culturing wild‐type tissues of leaf lamina successively on media containing reduced concentrations of the cytokinin, kinetin. Plants regenerated from clones of these variants exhibited the H1 phenotype, which segregated in breeding tests as expected for a dominant, monogenic trait. This trait, designated H1‐2, is inherited at a different locus than the H1‐1 trait described earlier. Our results show that cytokinin mutants can arise in cell culture and that at least two genes regulate the cytokinin requirement of cultured tobacco tissues.
Changes in plant gene expression during stress
Authors: Matters Gail L. , Scandalios John G. 
Published: May 2005

AbstractChanges in gene expression which occur during periods of environmentally induced stress provide models for the study of gene regulation. Several types of stress have been shown to elicit a specific and reproducible pattern of gene expression in various plant species. These stress factors include heat shock, anaerobiosis, plant pathogens, oxygen free radicals, heavy metals, water stress, and chilling. In some cases, changes in specific genes have been identified, such as increases in the expression of the gene encoding the phyto‐alexin‐synthesizing enzyme in pathogen elicitor‐treated cells. However, in most cases, the functional identity of stress‐induced genes is unknown. The alterations in gene expression during stress usually are rapid and repeatable, making these genetic systems ideal for examination of factors and mechanisms involved in gene regulation.
Sex ratio and testis size in mice carrying Sxr and T(X;16)16H
Authors: McLaren Anne 
Published: May 2005

AbstractMice heterozygous for the T(X;16)16H translocation and carrying Sxr on their normal (inactive) X chromosome (ie, T16H/X Sxr individuals) may develop as males, females, or hermaphrodites. The proportion of males varied from 22% to 65% depending on the source of the normal X chromosome. A model is proposed, according to which relatively small variations in the spreading of inactivation from the X chromosome into the attached Sxr fragment produce large changes in the proportion of males. Testis weight in T16H/X Sxr males was found to be significantly smaller than in X/X Sxr males, irrespective of the source of the normal X chromosome.
Description of an embryonic lethal gene, l(5)‐1, linked to Wsh
Authors: Papaioannou Virginia E. 
Published: May 2005

AbstractA recessive lethal mutant linked to Wsh causes the death of homozygous embryos between 4.5 and 5.5 days postcoitum (pc). Histological examination of implantation sites from intercross and backcross matings indicates that homozygotes are not all evident at 4.5 days pc, when embryos have begun to form trophectoderm giant cells and primitive endoderm, but are degenerating by 5.5 days pc, with only a few primary giant cells remaining after this time. The mutants thus form blastocysts that initiate the implantation process but the inner cell mass and polar trophectoderm fail to develop further. In vitro examination and culture of blastocysts indicated that the mutant homozygotes hatch from the zona pellucida and outgrow, although they do so somewhat more slowly than normal embryos. After 3 days of culture, the inner cell masses of mutant outgrowths may be smaller than normal. Since the gene has no known heterozygous effect and the primary gene function remains unknown, the mutant has been given the provisional symbol l(5)‐1 for the first lethal on chromosome 5.
Influence of mouse trisomy 16 on expression of specific genes
Authors: Fundele Reinald , Winking Heinz , Jägerbauer Eva‐Maria 
Published: May 2005

AbstractWe examined developmental changes in the relative activities of three different isozyme systems: aldolase, enolase and phosphoglycerate mutase, in tissues of fetal mice with trisomy 16 and of fetal euploid littermates. We wanted to determine whether morphological abnormalities such as reduced weight and size, which are generally observed in murine trisomy, are reflected at the molecular level. Following electrophoretic separation and subsequent measurement of relative activities of enolase isozymes in brain and phospho‐glycerate mutase isozymes in heart, we found no significant differences between trisomy 16 fetuses and their euploid littermates. Synthesis of liver‐specific aldolase was, however, delayed in trisomy 16 fetuses.
Differential riboflavin deposition in white and variegated white mutants of Drosophila hydei
Authors: van Breugel Frans M. A. 
Published: May 2005

AbstractRiboflavin deposition in organs of Drosophila hydei was studied by means of a growth test using a riboflavin‐deficient strain of the fungus Aspergillus nidulans. In wild‐type animals, riboflavin is deposited in Malpighian tubules (MT) and testes but not in adult eyes. Certain white (w) mutants do not contain riboflavin, whereas intermediately colored w mutants contain minor amounts of the substance. Riboflavin‐containing MT cells contain special globules that can be fixed and stained with the redox dye phenazine‐methosulphate. The number and size of these granules is related to growth effect and point to a role of the w locus in the intracellular deposition of riboflavin in special organs. In white‐mottled (wm) position‐effect variegation mutants, a significant correlation was found between the extent of variegation (percentage of yellow cells) and riboflavin content (growth effect) of the MT. However, the individual variation of cell phenotype was extremely large and exaggerated types were observed indicating “overdominance” of the rearranged w+ gene. This contradicts an unsubstantiated dogma of position‐effect variegation that assumes that the affected gene simply switches between the on and off state, as is discussed.
Tumor formation and morphogenesis on different Nicotiana sp and hybrids induced by Agrobacterium tumefaciens T‐DNA mutants
Authors: Nacmias B. , Ugolini S. , Ricci M. D. , Pellegrini M. G. , Bogani P. , Bettini P. , Inzé D. , Buiatti M. 
Published: May 2005

AbstractA series of experiments are presented that have been performed to observe the interactions between Agrobacterium tumefaciens strains mutated in the T‐DNA genes involved in indoleacetic acid and cytokinin biosynthesis and several Nicotiana species and hybrids. Infections were induced on leaf cuttings of Nicotiana debneyi, N. knightiana, N. clevelandii, N. bigelovii var bigelovii, N. bigelovii var quadrivalvis, N. glauca, N. langsdorffii, the amphidiploid tumorous hybrid N. glauca × N. langsdorffii, and a nontumorous mutant of it. The effect of deletions of the Ti plasmid varied according to plant genotype. Insertion mutants in iaaM and iaaH suppressed tumor formation in N. langsdorffii, reduced it in N. bigeloviivar quadrivalvis, had no effect in N. glauca and the two amphidiploid hybrids, and promoted tumorigenesis when compared to the wild‐type Agrobacterium strain B6S3 in N. bigelovii N. debneyi, and N. knightiana. The same mutations induced shoot formation in N. glauca, increased it in N. debneyi, and suppressed root formation in N. knightiana. On the other hand, an insertion mutation of the isopentenyl transferase gene (ipt‐) had no effect in N. bigelovii var quadrivalvis, N. debneyi, the tumorous hybrid, suppressed tumor formation in N. langsdorffii, and inhibited it in N. glauca, the nontumorous hybrid, N. bigelovii var bigelovii, and N. knightiana. Insertion in ipt suppressed shoot formation in the nontumorous hybrid and inhibited it in the nontumorous amphidiploid and N. debneyi, while promoting root formation in N. glauca and N. debneyi.The suggestion of the existence of specific hormone equilibria necessary for the shift to each morphogenetic pattern was supported by experiments with exogenous hormone treatments of three genotypes (N. glauca, N. langsdorffii, and the nontumorous N. glauca × N. langsdorffii).
The cellular basis of wing size modification in Drosophila: The effects of the miniature gene, crowding, and temperature
Authors: Kuo Tea , Larsen Ellen 
Published: May 2005

AbstractTo elucidate the mechanisms whereby genes and environment influence wing size, we investigated the effects of various rearing temperatures and larval crowding conditions on the wings of the mutant miniature and wild‐type fruit flies. In adults we monitored wing size, cell number, wing thickness, cell density; in larval imaginal discs we looked for cell death. Cell density was inversely proportional to wing size. Of particular interest was the finding that smaller wings tend to be thicker. Electron microscope studies showed that the miniature wing layers are grossly abnormal. We hypothesize that these abnormalities are due to abnormal cell flattening of the wing epithelial cells, and we conclude that gene and environmental effects on cell flattening may be an important component in determining cell density and hence organ size.
Allelic variation at the frizzled locus of Drosophila
Authors: Adler Paul N. , Charlton Jeannette , Vinson Charles 
Published: May 2005

AbstractThe epidermis of Drosophila has a tissue polarity that is manifested by a parallel array of polarized structures (primarily hairs and bristles). The production of normal tissue polarity requires the function of the frizzled (fz) locus. We have isolated a large number of alleles at this locus and have phenotypically characterized more than 25 of them. We have found extensive allelic variation that a previous study failed to detect. Most of the alleles fall into a hypomorphic to amorphic series. Two alleles, however, have unusual properties. These alleles, which in general are moderately strong alleles, fail to produce a rough eye phenotype that is characteristic of all the other moderate or strong fz alleles. Thus, these two alleles are tissue specific in effect. Furthermore, these two alleles also have a neomorphic or antimorphic effect on hair polarity in one region of the wing.
Post‐transcriptional regulation and DNA undermethylation of intracisternal A particle genes in embryonal carcinoma cell lines
Authors: Morgan Richard A. , Huang Ru Chih C. 
Published: May 2005

AbstractNorthern blot analysis and in vitro nuclear transcription assays were performed in order to clarify conflicting reports on the expression of intracisternal A particle (IAP) genes in embryonal carcinoma (EC) cell lines. Results demonstrate that post‐transcriptional mechanisms control the final steady‐state levels of IAP RNA in EC cells. IAP genes were further found to be undermethylated in IAP‐expressing EC cell lines.