bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of mating type determination by transplantation of O macronuclear karyoplasm in Paramecium tetraurelia
Authors: Koizumi Sadaaki , Kobayashi Sumiko , Mikami Kazuyuki 
Published: May 2005

AbstractThe odd (O) or even (E) mating type in Paramecium tetraurelia is determined during the first cell cycle after new macronuclear development. The present paper demonstrates that mating type E is irreversibly determined at the end of the first cell cycle. Direct evidence comes from transplanting O macronuclear karyoplasm containing O‐determining factor into E autogamous cells during a new postzygotic macronuclear development. Transplantation of O macronuclear karyoplasm into E autogamous cells at 7–8 hr after the origin of the macronucleus from a product of the synkaryon produces nearly 100% O mating type among the exautogamous cell lines but almost none 10–11 hr after the origin of the macronucleus (around the end of the first cell cycle). The macronuclear anlagen at the stage at which mating type E seems to be fixed contains about 20 times as much DNA as the vegetative G1 micronucleus. The O‐determining factor shifting E cells toward O mating type by transplanting O macronuclear karyoplasm is also produced by the newly developed macronucleus in an effective concentration at 10–11 hr after the sensitive period and produced at full levels by the third cell cycle. The level of O factor in the macronucleus then gradually declines with subsequent repeated rounds of DNA synthesis and is finally lost by the eighth cell cycle.
The relationship of relative gene dose to the complex phenotype of the daughterless locus in Drosophila
Authors: Cronmiller Claire , Cline Thomas W. 
Published: May 2005

AbstractThe daughterless (da) gene provides an essential maternally supplied component for Drosophila sex determination and dosage compensation. In this connection, it is required as a positive regulator of a female‐specific master regulatory gene, Sex‐lethal (Sxl). In addition, zygotic da gene function is required for male and female viability. Thus, the phenotype da is complex; it includes both maternal and zygotic aspects, as well as both sex‐specific and nonsex‐specific aspects. Assessment of wild‐type da function has relied on the characterization of only a single leaky mutant da allele. In order to better understand the nature of this allele and the relationships between the various aspects of its complex phenotype, tandem duplications of both the mutant and wild‐type da alleles were isolated and used in a dose study of this gene's function. Three conclusions were reached: (1) by the most stringent genetic criteria, the mutant da allele is a simple hypomorph, an allele with reduced but non‐zero levels of wild‐type functions; (2) since increased dose of da+ had no effect on viability or progeny sex ratio, this gene seems not to be a dose‐sensitive element of the X/A ratio sex determination signal; and (3) expression of the maternal da+ allele does make a contribution to the nonsex‐specific developmental processes that require zygotic da+ function; however, that contribution is clearly minor. In contrast, the zygotic genotype with respect to da appears to have no effect on the expression of Sxl+ in the zygote, the sex‐specific process that requires maternal da+ function.
β‐Glucuronidase activity is present in the microscopic epididymis of the Tfm/Y mouse
Authors: Scott J. Elliott , Blecher Stan R. 
Published: May 2005

AbstractThe sex‐linked recessive gene Tfm in the mouse produces a condition of testicular feminization (androgen insensitivity syndrome, AIS) in hemizygotes, comparable to the condition of the same name in humans. The murine mutant was originally believed to have no derivatives of the mesonephric duct system (MDS), and this absence was ascribed to dependence of these derivatives on androgens for survival. However, microscopical epi‐didymides, retia testes, and vasa deferentia were identified in these animals in our laboratory. These micro‐organs may play a role in meiosis induction in Tfm/Y animals. The present study was designed to determine whether survival of these organs is due to retention of an ability to respond to androgens, or whether they are unique amongst MDS derivatives in being independent of androgens.Previous studies in our laboratory demonstrated that the enzyme β‐glucuronidase (βG) is androgen sensitive in the epididymis of the normal mouse. In the present investigation we used this enzyme as a marker to study androgen sensitivity in the microscopical epididymides of Tfm/Y hemizygotes and in the epididymides of control +/Y litter‐mate brothers. Both mutant and control animals were studied with and without exogenous androgen stimulation.Tfm/Y hemizygotes demonstrated low levels of diffuse, cytoplasmic βG activity that appears to be unresponsive to exogenous androgen stimulation. In light of our previous studies, this distribution of βG reaction products suggests some degree of androgen sensitivity. The survival of these micro‐organs and their partial androgen sensitivity may be related to the role of the MDS in inducing meiosis.
Nonreciprocal gonadal dysgenesis in Chironomus thummi hybrids: Temperature sensitivity of female sterility
Authors: Häugele Klaus 
Published: May 2005

AbstractIn nonreciprocal hybrids of Chironomus thummi an environmental factor has been detected which, along with genetic factors, determines gonadal dysgenesis. Female hybrids of the cross Ch' thummi thummi ♂ ♂ × Ch. thummi piger ♀ ♀ show various degrees of rudimentary developed ovaries and sterility. The extent of these abnormalities is dependent on the developmental temperature of the hybrids. At a temperature of 21°C approximately 90% of the females are completely sterile and at 16°C only 30%. The curative effect of a temperature of 16°C on sterility occurs, however, only in those hybrid females which hatch from a specific type of egg mass (class A). Females of another type of egg mass (class B) show nearly as many dysgenic ovaries as do those developed at 21°C. At a developmental temperature of 21°C no such differentiation between the A and B class of egg masses is possible.Ovarian dysgenesis and sterility is induced during atemperature‐sensitive period which extends from the beginning of embryonic development through the first two‐thirds of the first larva instar stage. The abnormalities observed must be due to a failure in the early development of the germ line and are probably initiated by an inhibition of primordial germ cell divisions.
Evidence of a gene‐dosage effect for the glucocorticoid receptor in trisomy 18 mice
Authors: Vogliolo Daniel , Winking Heinz , Knuppen Rudolf 
Published: May 2005

AbstractThe amount of cytosolic glucocorticoid receptor in liver of Ts18, Tsl6, and Tsl9 vs euploid mouse fetuses was studied after incubation of [3H]dexamethasone with cytosol followed by isoelectric focusing on polyacrylamide gels. In addition, corticosterone concentrations and enzyme activities of alanine aminotransferase and tyrosine aminotransferase were measured in the cytosol of the livers. The amount of glucocorticoid receptor in the cytosol fractions of the livers was always higher in the Tsl8 than in the euploid fetuses of the same litter. It was also significantly (P < 0.0005) higher if pooled data from different litters were analyzed. The ratio of the glucocorticoid receptor in Ts l8 vs euploid mice varied between 1.3 and 4.7, with a mean of 2.1. In contrast, the glucocorticoid receptor levels in Tsl6 and Tsl9 fetuses were not different from the corresponding euploid controls. Comparing the corticosterone levels of the three trisomies tested with the corresponding euploid fetuses, no significant differences were found, indicating that the markedly elevated cytosolic glucocorticoid receptor concentrations in Tsl8 were not due to different corticosterone levels. This finding is consistent with the assignment of the glucocorticoid receptor gene to chromosome 18 in the mouse. There was no correlation betwen glucocorticoid receptor levels and the activity of the two glucocorticoid inducible enzymes tested in the liver of mouse fetuses.
Induction of gastrulation in the chick embryo
Authors: Zagris Nikolas , Matthopoulos Demetrios 
Published: May 2005

AbstractInteraction between the epiblast and the primary hypoblast in chick blastula results in induction of the primitive streak (PS) in the epiblast. Alpha‐amanitin, a specific inhibitor of poly A‐containing RNA synthesis, inhibits formation of the definitive PS. This inhibition is associated with qualitative changes in the pattern of protein synthesis in the hypoblast but not in the epiblast. The protein pattern of the component areas of the epiblast shows increase in some polypeptides after treatment with α‐amanitin. By contrast, α‐amanitin resulted in a decrease in synthesis of several polypeptides, which are either undetectable or weakly present in the hypoblast. The α‐amanitin‐sensitive translational products of the embryonic genome that are observed in the hypoblast may have specific functions in the control of PS induction and stabilization.
Expression of the differentiation antigen F7D6 in tumorous tissues of Drosophila
Authors: Bedian Vahe , Jungklaus Christine E. 
Published: May 2005

AbstractThe 63‐kDa antigen recognized by the monoclonal antibody F7D6 is present in all Drosophila embryonic cells and disappears from most tissues as each one reaches its final, differentiated state. Larval tissues lose the antigen around the time of hatching, imaginal tissues lose it during metamorphosis, and germ cells lose it during gametogenesis (Bedian et al: Devel Biol 115:105–118, 1986). The nervous system and spontaneously contracting musculature of the gut and gonads are exceptions and remain antigen positive at all stages. The F7D6 antigen appears to be associated with dividing, undifferentiated cells and electrogenic cells. This prompted us to test tumors for antigen presence. We tested four different recessive mutants that give rise to four different types of tumorous transformation: the embryonic tumor Notch, several larval melanotic tumors, the imaginal disc tumor 1(2)gl, and three alleles of the ovarian tumor otu. In all cases, tumorous tissues in homozygotes contained the F7D6 antigen. The electrophoretic mobility of the antigen appeared to be unaltered in tumorous tissues compared to normal cells, but the antigen is expressed at higher levels. The antigen is found on the cytoplasmic surface of plasma membranes and appears to be a marker of undifferentiated normal and tumorous cells. Similarities and differences between the F7D6 antigen and Drosophila c‐src protein are discussed.
Neurochemical characterization of embryonic brain development in trisomy 19 (Ts19) mice: Implications of selective deficits observed for abnormal neural development in aneuploidy
Authors: Saltarelli Mario D. , Forloni Gian Luigi , Oster‐Granite Mary Lou , Gearhart John D. , Coyle Joseph T. 
Published: May 2005

AbstractIn this study, we examined the neurochemical profiles of selected brain regions (cerebral hemispheres, diencephalon/brainstem) in fetal (day 14 to 18 gestation) trisomy 19 (Ts19) mice. The neurochemical characteristics we observed in Ts19 mice were quite different from those we observed previously in Ts16 mice. Choline acetyltransferase (ChAT) activity was reduced significantly in the cerebral hemispheres, but not in the brainstem/diencephalon, of the fetal Ts19 mouse brain, suggesting a selective vulnerability of telencephalic cholinergic neurons. Additionally, the activity of glutamic acid decarboxylase (GAD) was reduced significantly in both hemispheres and diencephalon/brainstem of late gestation Ts19 fetuses, suggesting a selective vulnerability of GABAergic neurons as well. While the levels of catecholaminergic and dopaminergic markers were reduced significantly at late gestational ages, the relative rate of turnover of dopamine (DA), measured by the ratio of DOPAC/DA, was elevated significantly in Ts19 mice. Neither reduction in the thickness of various cellular zones of the cerebral cortex nor reduced cell density of the cerebral cortex accounts for the alterations in neurochemical parameters observed in Ts19 mice. These results suggest that the effects of the triplication of specific genes on the respective chromosomes, rather than a generalized disruption of developmental homeostasis resulting from extra chromosomal material, may produce selective alterations in neurochemical and neuroanatomical markers observed in these two mouse trisomies.
Constitutive transcription of a soybean heat‐shock gene by a cauliflower mosaic virus promoter in transgenic tobacco plants
Authors: Schöffl Fritz , Rieping Mechthild , Baumann Götz 
Published: May 2005

AbstractTranscription of heat‐shock protein genes in soybean can be induced by high temperature stress leading to a transient expression of heat‐shock proteins. We have tested whether the replacement of a native heat‐shock promoter by a viral promoter results in constitutive transcript levels of the respective gene in transgenic plants. The 35S‐transcript promoter of the cauliflower mosaic virus was linked to the protein‐coding region of the genomic heat‐shock gene hs6831, encoding a 17.6‐kD heat‐shock protein of soybean. After transformation of tobacco plants with this chimeric construction using a disarmed Agrobacterium binary vector, abundant mRNA levels were detected in transgenic plants. The steady‐state level of this mRNA at 25°C was equal to that generated by the native heat‐shock promoter at 40°C; however, it was markedly reduced by heat shock applied to the transgenic plants. These findings suggest a sufficiently high stability of heat‐shock mRNA produced at the normal growth temperature to direct constitutive expression of heat‐shock proteins. The application of constitutive gene expression for the investigation of thermotolerance is discussed.
Chromatin structure and plant gene expression
Authors: Kahl Gönter , Weising Kurt , Görz Andrea , Schäfer Willi , Hirasawa Eiji 
Published: May 2005

AbstractThe nuclear DNA of eukaryotic organisms is associated with a variety of proteins, which together make up what is called “chromatin.” Chromatin serves to package all genes into higher‐order structures such as nucleosomes, solenoids, and loop domains. Tight packing of a particular gene and its regulatory sequences does not allow the approach of RNA I or II polymerase proteins. Before or during the activation of such an inactive gene its chromatin has to adopt a relaxed, more “open” configuration. This altered chromatin can be probed by its higher sensitivity toward nucleases, such as DNAse I or S1 nuclease, and the appearance of DNAse I‐hypersensitive sites. These sites may constitutively be present or may be induced, and they can be mapped to specific DNA sequence motifs. In many cases, such sites are delimited by non‐B‐DNA, notably Z‐DNA, which in turn may form part of enhancer elements. The Z‐DNA configuration may be induced or maintained by methylation of cytosyl residues within underlying sequences.Two plant gene model systems have been selected to probe their chromatin structure. Constitutively expressed T‐DNA genes of Agrobacterium induced tobacco crown gall tumor cells have been shown to be organized in canonical nucleosomes, to be more sensitive to DNAse I than the bulk of host chromatin, and to contain a series of six constitutive DNAse I‐hypersensitive sites. Inducible ribulose‐1,5‐bisphosphate carboxyl‐ase/oxygenase small subunit (rbcS) genes of pea are rearranged into a nuclease‐sensitive format upon activation by light, especially in their promoter region. The rbcS promoter harbors a series of five constitutive DNAse I‐hypersensitive sites and one light‐inducible site, which is surrounded by potential regulatory sequences (enhancer cores, inverted repeats). The 3′ region of rbcS genes also contains constitutive sites. Methylation/demeth‐ylation of Alu I‐, Fnu4H1‐, HaeIII‐, Sau3AI‐, and Sau 96I sequences in rbcS promoters does not play any role in rbcS gene inactivation/activation.
Plant tubulin genes: Structure and differential expression during development
Authors: Silflow Carolyn D. , Oppenheimer David G. , Kopozak Steven D. , Ploense Sara E. , Ludwig Steven R. , Haas Nancy , Peter Snustad D. 
Published: May 2005

AbstractMicrotubules are important components of the cytoskeleton of plant cells and play key roles in plant growth and morphogenesis. Recent molecular studies have begun to elucidate the structure and expression of plant genes coding for the major components of microtubules, α‐ and β‐tubulin. Tubulin amino acid sequences deduced from the DNA sequences of eight higher plant tubulin genes are 79–87% homologous with constitutively expressed mammalian tubulins. The genome of the model plant system Arabidopsis thaliana contains four dispersed α‐tubulin sequences and at least seven β‐tubulin sequences, only two of which appear to be linked. Of the five A. thaliana genes whose expression has been analyzed, the transcripts of one α‐tubulin and one β‐tubulin gene are constitutively expressed in roots, leaves, and flowers. A second α‐tubulin gene is expressed predominately in flowers; the transcripts of the second and third β‐tubulin genes are found predominately in leaves or in roots, respectively.
Structural and biochemical studies on four sex‐linked chorion mutants of Drosophila melanogaster
Authors: Komitopoulou Katia , Margaritis Lucas H. , Kafatos Fotis C. 
Published: May 2005

AbstractFour female‐sterile mutants, fs(l)K451, fs(1)K1214, fs(1)K575TS, and fs(1)384, were studied in terms of chorion structure and chorion protein composition. The first three of these mutants cause morphological defects, ie, substantial underproduction and disruption of the endochorion, correlated with underproduction of the six major chorion proteins, s15–s38; the phenotypes are consistent with the observation that these mutants interfere with amplification of the major chorion genes that encode the s15–s38 proteins [Orr et al.: Proc Natl Acad Sci USA 81:3773–3777, 1984; Komitopoulou et al.: Dev Genet 7:75–80, 1986]. The fourth mutant, fs(1)384, and its alleles do not interfere with production of the major chorion proteins and the morphologically detectable bulk of the endochorion but lead to failure of endochorionic organization. Apparently this complementation group is responsible for a minor chorion product, which is evidently important morphogenetically and which is processed posttranslationally in a complex manner [Bauer and Waring: Dev Biol 121:349–358, 1987].
Multiplicity of functions for the otu gene products during Drosophila oogenesis
Authors: Storto Patrick D. , King Robert C. 
Published: May 2005

AbstractThe ovarian tumor gene behaves as if it encodes a product (OGP), which is required durirng several early steps in the transformation of oogonia into functional oocytes. Seventeen ethyl methane sulfonate‐induced mutations have been studied, and their mutant phenotypes can be explained as graded responses by individual germ cells to different levels of OGP synthesized by the mutant germ cells themselves. The lowest and highest levels of OGP appear to be produced by otu10 and otu14, respectively. The 15 mutants with intermediate OGP levels are temperature sensitive; subnormal temperatures improve ovarian development, while above‐normal temperatures suppress it. A subgroup ofthese mutants are unable to form a system of actin microfilament bundles in the cortical cytoplasm of their nurse cells during stage 10B, and these defective nurse cells are unable to transport their cytoplasm to the oocyte, as normally happens between stages 10B and 12. In addition to its role in the actin‐mediated transport of nurse cell cytoplasm, OGP also appears to alter the morphology of giant polytene chromosomes, which form as the nurse cells undergo endocycles of DNA replication. Genetic evidence suggests that otu also encodes a second product (SP) that is utilized late in oogenesis. SP is required for the synthesis in the ooplasm of glycogen‐rich, beta yolk spheres. Products of the otu gene also play a vital but unknown role in embryogenesis.
Anemia in a line of transgenic mice carrying a mutant dihydrofolate reductase gene
Authors: Isola Luis M. , Gordon Jon W. 
Published: May 2005

AbstractSeveral lines of transgenic mice were produced by pronuclear injection of a full‐length cDNA encoding a mutant dihydrofolate reductase (DHFR, E.C. 1.5.1.3). The mutation causes altered enzyme kinetics for folate reduction as well as low affinity for methotrexate (MTX). One line of mice carrying the plasmid displays a moderate‐to‐severe anemia that is evident in fetuses and newborn mice and that moderates with age. RNA studies revealed high levels of transcription of the mutant gene in the fetal and adult liver, and low or absent expression in adult bone marrow. Transcription of the mutant gene was not found in the fetal liver of other pedigrees examined. The data thus suggest that expression of this mutant gene in the main hematopoietic organ of the fetus adversely affects erythropoiesis by altering the cellular environment for erythroid differentiation, and that translocation of the site of hematopoiesis to bone marrow, where the foreign gene is not expressed, leads to normalization of red cell production.
Effect of low‐temperature rearing on heat shock protein synthesis and heat sensitivity in Drosophila melanogaster
Authors: Singh A. K. , Lakhotia S. C. 
Published: May 2005

AbstractThe patterns of synthesis of heat shock proteins (hsp) and heat sensitivity to elevated temperatures in larvae of Drosophila melanogaster reared since hatching at 20°C (warmreared) or at 10°C (cold‐reared) were compared. The pattern of hsp synthesis in salivary glands from the cold‐ and warm‐reared late‐third‐instar larvae exposed for l hr to 33°C or to 37°C was generally similar except for remarkable differences in the 23 kd hsp and a heat‐inducible 14 kd polypeptide. The hsp 23 was abundantly synthesised in control as well as heat‐shocked warm‐reared larval salivary glands, its synthesis in heat‐shocked glands being dependent on new transcription. The synthesis of hsp 23 was much less in control glands of cold‐reared larvae and was not further inducible by heat shock. The 14 kd polypeptide synthesis was greater in control as well as heat‐shocked salivary glands of cold‐reared larvae, whereas, in the warm‐reared ones, its activity was much less. The cold‐reared larvae showed greater sensitivity to elevated temperature; fewer adults eclosed when the cold‐reared late‐third‐instar larvae were exposed to 40°C for l hr and also a pretreatment at 37°C for l hr was less effective in stopping the killing effect of a subsequent 40°C heat shock in cold‐reared than in warmA‐reared larvae. The greater thermosensitivity of the cold‐reared larvae may be correlated with the altered patterns of heat shock gene transcription and translation in cold‐reared larvae.