bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic analysis of somatic embryogenesis in carrot cell culture: Initial characterization of six classes of temperature‐sensitive variants
Authors: Schnall Jennifer A. , Cooke Todd J. , Cress Dean E. 
Published: May 2005

AbstractCell cultures of the carrot Daucus carota are a useful experimental system for studying the genetic regulation of plant embryogenesis. A modified filtration‐enrichment procedure was used to isolate 21 temperature‐sensitive variants in somatic embryogenesis; the variants display normal embryo development at the permissive temperature (24°C) and altered development at the restrictive temperature (33°C). Temperature‐shift experiments were performed on these variants to determine the timing of gene action for the putative temperature‐sensitive alleles. According to their phenotypes at the restrictive temperature, these variants can be divided into six classes: No Growth, Callus Proliferation, Globularstage Block, Oblong‐stage Block, Lateral Growth, and Root Formation. Although many variants exhibit lengthy temperature‐sensitive periods, the temperature sensitivity of some variants is restricted to one or two embryonic stages. These results plus those in the literature are incorporated into a preliminary model concerning the genetic regulation of carrot embryogenesis.
Quantitative evaluation of coat‐color patterns in artificially produced chimeras of the mouse by means of a microcomputer‐based video‐image analysis system
Authors: Tachi Chikashi 
Published: May 2005

AbstractThe possible application of microcomputer‐based video‐image analysis systems for the quantitative description of coat‐color patterns in artificially produced chimeras and genetic mosaics of mice was investigated using a program developed by theauthor. This system is capable of extracting, from sampled images of pelts, the morphometric image features as defined by Pratt [1978] that are essential to the quantitative description of coat‐color patterns in these animals. It does so with reasonable accuracy and speed and at low cost. No description of any similar system has been published in the literature. Performance of our system is described using C3H/HeJ ↔BALB/c chimeras as examples.The complex phenotypic expression of hair pigmentation in mice makes the use of a video‐image analysis system like this one essential to evaluate the morphometric parameters of the patterns (e.g., the mixing ratios between the two components, the number of different‐colored stripes, etc.) more precisely and reproducibly than has been done yet in the literature.The results indicate that the number of melanoblast clones in mice, as estimated from the number of minimal recognizable stripes (MRS), might be considerably largerthan previously indicated; the figure presently obtained, i.e., 22.3 ± 2.16 unilaterally in terms of the hypothetical maximum number of stripes (HMNS) (28.73 ± 1.55, after correction for the random clumping) in the thoracicolumbar region of the mouse closely approximates the number of the somites in that region. Concerning the degree of mixing between the two components, it was proposed that the unmixed portion of the components derived from one strain increases in proportion to the second power of the increase in the relative total content of the same components. Work is in progress in our laboratory to analyze a large number of the chimeric pelts using the system described in this paper.
Investigation of the tissue specificity of the lethal yellow (Ay) gene in mouse embryos
Authors: Papaioannou Virginia E. 
Published: May 2005

AbstractThe tissue specificity of the lethal yellow mutant was investigated by separation of blastocyst tissues. Embryos from experimental (Ay/ae × Ay/ae) and control (ae/ae × Ay/ae) crosses of the AG/CamPa inbred strain were recovered at 3.5 days post coitum, cultured for 24 hours, and then mechanically dissected into the component tissues of the blastocyst, the inner cell mass (ICM), and trophectoderm. These fragments were then cultured separately, with or without a feeder layer of inactivated fibroblasts, for an additional 3–5 days. Comparisons between experimental and control crosses indicated that the lethal Ay/Ay embryos were among the blastocysts successfully dissected but that both the ICM and trophectoderm from lethal embryos failed to develop further in vitro, eithal with or without feeders.With retrospective identification of the lethal embryos, it was found that at 4.5 days, after 1 day of culture, they had formed morphologically normal blastocysts but were frequently more fragile upon dissection and had smaller ICMs. Although none had hatched from the zona pellucida, some had ruptured it and were halfway out. With culture, lethal ICMs showed no development, and lethal trophectoderm usually attached but showed very limited outgrowth. Thus, no rescue of lethal tissue was shown with dissection and in vitro culture, and results are consistent with the gene affecting both tissues of the late blastocyst.
Minute mutations of Drosophila melanogaster change aldehyde oxidase and pyridoxal oxidase distribution patterns in imaginal wing discs
Authors: Van Zijll Langhout Bart W. , Sprey Thomas E. 
Published: May 2005

AbstractAldehyde oxidase (AO) and pyridoxal oxidase (PO) distribution patterns were determined in the imaginal wing discs for a series of strains of Drosophila melanogaster heterozygous for different Minute mutations. The mutant severity ranged from very weak to strong. The results show an inverse response of AO and PO to the expressivity of the Minute mutation: in weaker Minutes the extent of the AO positive area increases, whereas PO activity disappears. The results are discussed with reference to an impaired protein synthesis in Minutes.
An autosomal dominant mutation of facial development in a transgenic mouse
Authors: Wakasugi Shoji , Iwanaga Tomohisa , Inomoto Takeaki , Tengan Toshimoto , Maeda Shuichiro , Uehira Masahiro , Araki Kimi , Miyazaki Junichi , Eto Kazuhiro , Shimada Kazunori , Yamamura Ken‐Ichi 
Published: May 2005

AbstractWe have created a transgenic mouse which showed an autosomal dominant mutation of facial development. This facial malformation was characterized by a short snout and a twisted upper jaw. All offspring showing the dysmorphic phenotype carried the injected gene. In order to analyze the primary cause of this mutation, newborn mice and embryos were examined. The outcome was that the malformation of nasal and premaxillary bone was not the primary defect but was a secondary event. The primary cause of this dysmorphism was a developmental defect in the first branchial arch. Genomic DNA fragments flanking the insertion site of this mutant mouse were cloned. Using these fragments, we have assigned the integration site to chromosome 13. The gene responsible for a previously reported mutant mouse, one which also has a short snout, is also reported to be on chromosome 13. In the fragments flanking the insertion site of the transgenic mouse, at least one fragment was highly conserved in mammals. These results indicate that this malformation is due to the insertional disruption of a host gene. However, the possibility that this mutation is caused by an inappropriate expression of the injected gene still remains to be investigated.
cAMP‐dependent protein kinase from Dictyostelium discoideum
Authors: Veron Michel , Mutzel Rupert , Lacombe Marie‐Lise , Simon Marie‐Noëlle , Wallet Valérie 
Published: May 2005

AbstractThe cAMP‐dependent protein kinase (cAK) from Dictyostelium discoideum is an enzyme composed of one catalytic and one regulatory subunit. Upon binding of cAMP, the holoenzyme dissociates to liberate free active catalytic subunits. The cAK is developmentally regulated, ranging from very little activity in vegetative cells to maximal expression in postaggregative cells. Although there is no immunological cross‐reaction between the subunits of cAKs from Dictyostelium and from other organisms, they share several biochemical properties. A complete cDNA for the regulatory subunit has been cloned and sequenced. Only one copy of the gene for the regulatory subunit is present per haploid genome. On the basis of the comparison of the structure of the cAK from Dictyostelium with its counterparts in yeast and higher eukaryotes, we propose a model for the evolution of cyclic‐nucleotide‐binding proteins.
Genes encoding novel GTP‐binding proteins in Dictyostelium
Authors: Saxe Stephen A. , Kimmel Alan R. 
Published: May 2005

AbstractWe have identified a two‐member gene family in the Dictyostelium genome and have isolated corresponding cDNA or genomic DNA recombinant clones. Analyses of these DNA sequences predicted encoded proteins of ∼︁200 amino acids with ∼︁90% sequence identity to each other. These Dictyostelium proteins also share amino acids identity within the GTP‐binding domains in the family of G‐regulatory proteins involved in cellular regulation and transmembrane signalling. Additional structural similarities are seen with members of the ras supergene family, such as ras, ral, and rho. They are similar in size (usually ∼︁200 amino acids), possess four conserved domains involved in GTP interaction and are believed to be anchored in the membrane by fatty acid modification of a cysteine residue near the carboxy terminus. More extensive identity is observed with YPT1 and SEC4, two other members of this family of genes that are essential in yeast. The amino‐terminal half of both Dictyostelium proteins is 70% identical in amino acid sequence to the YPT1 and SEC4 yeast proteins with less identity continuing through the remainder of the proteins. In addition these proteins terminate in two cysteine residues that are thought to be required for membrane anchorage.The two genes within this Dictyostelium family are organized differently in the genome and are differentially regulated during development. One gene is colinear in sequence with its mRNA in the protein coding region, whereas the other gene encodes a spliced mRNA. The intron‐containing gene is associated with a developmentally regulated (AAC)‐repeat sequence. Finally, we have shown that the expression of one of the genes is induced during development with kinetics similar to that of other (AAC)n‐associated genes; conversely, the expression of the second gene is repressed at a similar developmental stage.
The cyclic nucleotide phosphodiesterase of Dictyostelium discoideum: The structure of the gene and its regulation and role in development
Authors: Podgorski Gregory J. , Faure Michel , Franke Jakob , Kessin Richard H. 
Published: May 2005

AbstractThe cyclic nucleotide phosphodiesterase (phosphodiesterase) of Dictyostelium discoideum plays an essential role in development by hydrolyzing the cAMP used as a chemoattractant by aggregating cells. We have studied the biochemistry of the phosphodiesterase and a functionally related protein, the phosphodiesterase inhibitor protein, and have cloned the cognate genes. A 1.8‐kb and a 2.2‐kb mRNA are transcribed from the singlephosphodiesterase gene. The 2.2‐kb mRNA comprises the majority of the phosphodiesterase mRNA found in differentiating cells and is transcribed only during development from a promoter at least 2.5 kb upstream of the translational start site. The 1.8‐kb phosphodiesterase mRNA is detected at all stages of growth and development, is present at lower levels than the developmentally induced mRNA, and is transcribed from a site proximal to the protein‐coding region. The phosphodiesterase gene contains a minimum of three exons, and a 2.3‐kb intron, the longest yet reported for this organism. We have shown that the pds A. gene and fourfgd genes affect, the accumulation of the phosphodiesterase mRNAs, and we believe that these loci represent a significant portion of the genes regulating expression of the phosphodiesterase. The phosphodiesterase gene was introduced into cells by transformation and used as a tool to explore the effects of cAMP on the terminal stages of development. In cells expressing high levels of phosphodiesterase activity, final morphogenesis cannot be completed, and differentiated spore and stalk cells do not form. We interpret these results to support the hypothesis that cAMP plays an essential role in organizing cell movements in late development as well as in controlling the aggregation of cells in the initial phase of the developmental program.
Contact alters cAMP metabolism in aggregation‐competent Dictyostelium amoebae
Authors: Fontana Donna R. , Price Pamela L. 
Published: May 2005

AbstractcAMP and cell‐cell contact are involved in the coordination of differentiation and morphogenesis in Dictyostelium discoideum. The experiments described in this paper establish a relationship between cAMP and cell‐cell contact. Contact between Enterobacter aerogenes and aggregation‐competent Dictyostelium amoebae and contact between Dictyostelium amoebae themselves results in the transient secretion of cAMP and an alteration in the amount of cAMP secreted in response to subsequent stimulation by cAMP, i.e., an alteration in magnitude of a cAMP relay response. The subsequent cAMP relay response can be enhanced or diminished depending upon the number of contacts formed and the concentration of cAMP present at the time of contact. Latex beads are capable of evoking cAMP secretion. However, the bead/amoebal contact is unable to alter the magnitude of a subsequent response to cAMP. This suggests that a nonspecific interaction via cell‐cell contactelicits transient cAMP secretion in aggregation‐competent Dictyostelium amoebae.The two responses to cell‐cell contact are distinct from each other and distinct from the cAMP relay response. (1) The dose‐response curves for the responses to Enterobacter contact are clearly different. (2) Contact with latex beads can elicit cAMP secretion but not alter the magnitude of a subsequent cAMP relay response. (3) The temperature dependences of the contact‐induced responses and the cAMP relay response show that only the contact‐induced cAMP secretion is inhibited at 12 and 15°C, while only the cAMP relay response is inhibited at 28°C.A 4‐second application of cAMP at the time that contact is initiated enhances both contact‐induced responses. Whether the relationship between these two developmental regulators is important for the regulation of Dictyostelium development has yet to be established.
The effect of caffeine, adenosine, and buffer ionic composition on the induction of cell‐surface cAMP binding during starvation of Dictyostelium discoideum
Authors: Drummond Iain A. S. , Chisholm Rex L. 
Published: May 2005

AbstractWe have analyzed the effects of the cAMP relay inhibitor, caffeine, and the receptor antagonist, adenosine, on the regulation of the cell‐surface cAMP receptor in suspensionstarved Dictyostelium discoideum cells by measuring ammonium sulfate‐stabilized binding of [3‐H]cAMP to intact cells. When cells were starved in fast (230 r.p.m.) shaken suspension in 10 mM Na+/5 mM K+ phosphate buffer, pH 6.5, plus 1 mM CaCl2 and 2.5 mM MgCl2, and assayed for specific cAMP binding, receptor accumulation peaked at approximately 6 hours, reaching a maximum of 1.5 pmol cAMP bound/107 cells (saturation binding). Neither caffeine nor adenosine inhibited the accumulation of cAMP receptors. Similar results were obtained in caffeine‐treated, slow shaken (90 r.p.m.) suspension cultures. These results suggest that starvation alone is sufficient stimulus to induce the cAMP receptor. We have also tested the effects of different buffer ionic compositions on the accumulation of cAMP receptors. Elevation of the monovalent ion concentration to 30‐40 mM was found to significantly inhibit the induction of cAMP receptors.
Characterization of genes that are developmentally regulated during Dictyostelium discoideum spore germination
Authors: Ennis Herbert L. , Giorda Roberto , Ohmachi Tetsuo , Shaw David R. 
Published: May 2005

AbstractSimilar to other stages in Dictyostelium development, spore germination is a particularly suitable model for studying the regulation of gene expression, because developmentally regulated changes in both protein and mRNA synthesis occur during the transition from dormant spore to amoeba. Spores are constitutively dormant and must be activated to germinate. Under the proper environmental conditions, spores germinate in a highly synchronous manner to give rise to individual amoebae that can then enter the vegetative growth phase. Protein synthesis is developmentally regulated during this process. Because protein synthesis is transcriptionally controlled during spore germination, the respective genes must be developmentally transcribed, and these can be isolated and analyzed. Three cDNA clones specific for mRNA developmentally regulated during spore germination have been characterized and used as probes to study mRNA accumulation and decay during spore germination. Because we are interested in defining the sequences of developmentally regulated genes that may relate to their regulation of transcription, we have sequenced the cDNAs and have isolated and sequenced their respective genomic clones. The sequences of the three gene families, their genomic organization, and their special structural features are described.
Analysis of the prestarvation response in growing cells of Dictyostelium discoideum
Authors: Clarke Margaret , Yang Jing , Kayman Samuel C. 
Published: May 2005

AbstractWe have previously shown that growing cells of Dictyostelium discoideum (strains NC4 and AX3) produce a soluble substance that accumulates in the medium in proportion to cell density; this substance regulates the production of certain proteins previously thought to be induced by starvation [Clarke et al., 1987]. We suggest the name PSF (prestarvation factor) for this substance. During growth, Dictyostelium cells monitor the relative concentrations of PSF and food bacteria. When PSF reaches a sufficiently high level relative to the concentration of bacteria, synthesis of PSF‐regulated proteins is induced. We propose the name prestarvation response for this induction, which takes place in exponentially growing cells several generations before the food bacteria are depleted. We have explored the mechanism by which the food bacteria inhibit the response of Dictyostelium cells to PSF. We find that the bacteria do not inactivate PSF or inhibit its production; instead, they affect the ability of NC4 cells to detect PSF, possibly by binding to the same cell surface receptor. In the absence of bacteria, as during axenic growth of AX3 cells, the prestarvation response occurs at much lower cell densities, probably accounting for the presence of certain developmentally regulated mRNAs and proteins in axenic cultures.
Deactivation of gene expression upon the onset of development in Dictyostelium discoideum
Authors: Singleton Charles K. , McPherson Clifton E. , Manning Suzanne S. 
Published: May 2005

AbstractSeveral genes that are deactivated upon the initiation of development of Dictyostelium discoideum have been identified by differential screening of various cDNA libraries. These genes have in common a decrease in the steady‐state levels of their corresponding mRNAs as development proceeds. When development was carried out in the absence of protein synthesis by inhibition with cycloheximide, the decrease in mRNA levels for most genes (V genes) was normal or slightly accelerated. However, for about 5% of the genes (H genes), cycloheximide caused an apparent induction of expression, as revealed by a slight or dramatic increase in mRNA levels instead of the normal decrease. This effect was due to inhibition of protein synthesis and not to cycloheximide per se. The induction was found to be due to an enhancement of the trascription rate; normal rates of transcription for the H genes were dependent upon continued protein synthesis during vegetative growth and during development. Thus, two general regulatory classes exist for deactivation of gene expression upon initiation of development, one dependent and one independent of protein synthesis. Models concerning the control of expression of these two classes of genes are discussed here. Analysis of expression of these genes in mutant strains that are aggregation‐deficient has also been performed, and the results lead to subdivisions of the classes.
Control of early gene expression in Dictyostelium
Authors: Mann Sandra K. O. , Pinko Christopher , Firtel Richard A. 
Published: May 2005

AbstractWe have examined the expression of a cAMP pulse‐repressed and two cAMP pulse‐induced genes in response to cAMP and caffeine under a number of different physiological conditions, and in several classes of developmental mutants altered in cAMP‐mediated signal transduction pathways. The data presented help characterize the mutants with regard to early gene expression. Analysis of the data indicates that full induction of the pulse‐induced or repression of the pulse‐repressed genes requires cycles of activation and adaptation of the cAMP receptor but does not require a rise in intracellular cAMP. Comparison of the results obtained between different mutant classes suggests that repression and activation of the two classes of genes can be uncoupled, implying that different intracellular mechanisms control these processes. In addition, we examined the effects of caffeine and show that it can induce pulse‐induced mRNA accumulation in the absence of cAMP.
Transmembrane signal transduction regulates gene expression in Dictyostelium discoideum
Authors: Pavlovic Jovan , Haribabu Bodduluri , Dottin Robert P. 
Published: May 2005

AbstractcAMP regulates gene expression in Dictyostelium discoideum through the cell surface receptor and is therefore a transmembrane signal transduction event. We have now begun to examine the signal transduction pathway that transmits the cAMP‐induced signal to the nucleus. The results presented here indicate that Ca2+ plays a crucial role. A comparison of the accumulation of UDPGP1 mRNA during development with the corresponding transcription rates revealed that this gene is regulated primarily at the level of transcription. To elucidate the factors involved in the regulation of the UDPGP1 gene we characterized its cis acting sequences. We constructed a series of deletions into the 5′ flanking region of the UDPGP1 gene and analyzed the expression of the mutated DNA in transformants. A sequence element essential for the expression of the UDPGP1 gene is located between ‐500 bp and ‐288 dp from the transcription start site. This promoter element appears to be a short G + C‐rich sequence positioned between ‐374 to ‐395 and coincides with a DNase I hypersensitive site.