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  • 1
    Electronic Resource
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    Springer
    Annals of operations research 2 (1984), S. 285-316 
    ISSN: 1572-9338
    Keywords: Regulation ; shadow price ; economics ; markets ; natural gas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Inclusion of the shadow prices for natural gas in a dynamic fuels model for the United States shows that the primary reason for the relatively large, fly-up in new marginal gas prices in the early 1980's was the release of the pent-up price effects of the U.S. government's price regulations. In accordance with principles, the shadow price of natural gas fell siginificantly following de-regulation of the highcost gas (section 107) in 1980, which represented the precursor for downward adjustments in marginal wellhead prices of new high-cost gas and drilling activity. The modeling results show that no significant fly-up in new marginal gas prices for lower-cost gas (section 102) is likely to occur in 1985, when its phased de-regulation ends and it is finally de-regulated, because no shadow price precursor currently exists for this gas. Shadow price principles clear up the primary misconceptions with regard to natural gas pricing. This application indicates the significance of shadow price principles for regulated pricing in general.
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  • 2
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    Entomologia experimentalis et applicata 34 (1983), S. 51-57 
    ISSN: 1570-7458
    Keywords: Blattella ; German cockroach ; Females ; Reproductive cycle ; Food intake ; Water intake ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé L'examen de la consommation d'eau et d'aliments par les femelles adultes de Blattella germanica a été lié au cycle reproductif. La consommation individuelle quotidienne des insectes a été reliée à certains évènements marquants dans chacun de quatre cycles de production d'oothèque. Les pics d'alimentation et d'absorption se produisaient pendant la période de maturation des oeufs, mais disparaissaient brutalement à l'apparition de chaque oothèque. Pendant la période où les femelles portent les oothèques, elles s'alimentent et s'abreuvent parcimonieusement. Le rôle éventuel joué par l'alimentation et particulièrement l'absorption dans la régulation de la reproduction de cet important insecte nuisible est examiné.
    Notes: Summary Food and water consumption by adult female German cockroaches has been examined in relation to the reproductive cycle. Daily consumption was recorded for individual insects and was related to certain landmark events in each of four egg-case production cycles. It was shown that peaks of feeding and drinking occur during the egg maturation period, but are abruptly terminated at the appearance of each egg case. During the period when females carry the egg case, they feed and drink sparingly. The possible role played by feeding and especially drinking in the regulation of reproduction in this important pest species is discussed.
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  • 3
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    Springer
    Journal of molecular evolution 19 (1983), S. 214-218 
    ISSN: 1432-1432
    Keywords: Codon: anticodon adaptation ; Mutation ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Synonymous codon usage frequencies, derived from cDNA clone sequences, were compared for several sets of vertebrate genes. Gene sets as diverse as those expressed in avian skeletal muscle and in mammalian liver showed similar patterns of synonymous codon usage. There were no significant differences suggesting tissue-specific co-adaptation of codon usage patterns and tRNA anticodon profiles. The results indicate a consensus codon usage pattern for vertebrate genes which is largely independent of taxonomic class, tissue of expression, and the cellular fate and rate of evolution of the encoded proteins. Certain elements of the consensus codon usage pattern indicate that it is the product of natural selection and not simply a mutational equilibrium among phenotypically equivalent synonyms.
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  • 4
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    Journal of biomedical science 3 (1996), S. 143-158 
    ISSN: 1423-0127
    Keywords: Transforming growth factor-β ; Tumorigenesis ; Mutation ; Tumor suppressor gene ; Receptor ; Microsatellite instability ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Transforming growth factor-β (TGF-β) plays a pivotal role in numerous vital cellular activities, most significantly the regulation of cellular proliferation and differentiation and synthesis of extracellular matrix components. Its ubiquitous presence in different tissues and strict conservation of nucleotide sequence down through the most primitive vertebrate organisms underscore the essential nature of this family of molecules. The effects of TGF-β are mediated by a family of dedicated receptors, the TGF-β types I, II, and III receptors. It is now known that a wide variety of human pathology can be caused by aberrant expression and function of these receptors or their cognate ligands. The coding sequence of the human type II receptor appears to render it uniquely susceptible to DNA replication errors in the course of normal cell division. There are now substantial data suggesting that TGF-β type II receptor should be considered a tumor suppressor gene. High levels of mutation in the TGF-β type II receptor gene have been observed in a wide variety of primarily epithelial malignancies, including colon, gastric, and hepatic cancer. It appears likely that mutation of the TGF-β type II receptor gene represents a very critical step in the pathway of carcinogenesis.
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  • 5
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    Journal of biomedical science 4 (1997), S. 319-326 
    ISSN: 1423-0127
    Keywords: Oxidative damage ; Reactive oxygen species ; Mitochondria ; Mitochondrial DNA ; Mutation ; Aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mitochondria are the major intracellular source and target sites of reactive oxygen species (ROS) that are continually generated as by-products of aerobic metabolism in animal and human cells. It has been demonstrated that mitochondrial respiratory function declines with age in various human tissues and that a defective respiratory chain results in enhanced production of ROS and free radicals in mitochondria. On the other hand, accumulating evidence now indicates that lipid peroxidation, protein modification and mitochondrial DNA (mtDNA) muutation are concurrently increased during aging. On the basis of these observations and the fact that the rate of cellular production of superoxide anions and hydrogen peroxide increases with age, it has recently been postulated that oxidative stress is a major contributory factor in the aging process. A causal relationship between oxidative modification and mutation of mtDNA, mitochondrial dysfunction and aging has emerged, although some details have remained unsolved. In this article, the role of mitochondria in the human aging process is reviewed on the basis of recent findings gathered from our and other laboratories.
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  • 6
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    Development genes and evolution 193 (1984), S. 149-157 
    ISSN: 1432-041X
    Keywords: Intercalary regeneration ; Regulation ; Morphallaxis ; Planarians
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the planarianDugesia lugubris, when two originally widely separated body levels are joined together, intercalary regeneration is induced. The whole sequence of levels normally intervening between the two levels joined are reformed by one of the two associated pieces. Generally regeneration is accomplished by morphallactic remodelling. This process starts at the margin of the suture, which was originally nearer to the head, and progressively extends through the piece, which is entirely remodelled if it is too short. Thus, a head cut at the level of the eyes and joined to a tail is totally reshaped, forming a new head with a new pair of eyes and a new prepharyngeal zone in which the original eyes persist. When the head piece is too short, the pharynx is not produced by the regenerate, but secondarily through remodelling of the tail piece. Remodelling of the head piece is also observed when it is joined to a prepharyngeal piece. When a head piece is joined in reverse orientation to a tail piece, the remodelling, which is directed by the tail, leads to the reversal of polarity in the head tissues. When the head piece is entirely remodelled it forms an anterior extremity, a new head with new eyes and a prepharyngeal zone containing the original eyes. After joining the preocular level to a prepharyngeal level the intercalary regenerate is entirely built up by dedifferentiated cells (epimorphosis), which are produced by the prepharyngeal tissues (the margin which represents the more posterior level). The results do not support Child's concept of dominance and are interpreted in the light of the concept of cell sociology.
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  • 7
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    Development genes and evolution 207 (1997), S. 42-50 
    ISSN: 1432-041X
    Keywords: Key words Cell lineage ; Dorsoventral axis ; Nemertea ; Regulation ; Spiralians
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Embryos acquire axial properties (e.g., the animal-vegetal, dorsoventral and bilateral axes) at various times over the course of their normal developmental programs. In the spiral-cleaving nemertean, Cerebratulus lacteus, lineage tracing studies have shown that the dorsoventral axis is set up prior to the first cleavage division; however, blastomeres isolated at the two-cell stage will regulate to form apparently perfect, miniature pilidium larvae. We have examined the nature of axial specification in this organism by determining whether partial embryos retain the original embryonic/larval axial properties of the intact embryo, or whether new axial relationships are generated as a consequence of the regulatory process. Single blastomeres in two-cell stage embryos were injected with lineage tracer, and were then bisected along the second cleavage plane at the four-cell stage. Thus, the relationship between the plane of the first cleavage division and various developmental axes could be followed throughout development in the ”half-embryos”. While some embryo fragments appear to retain their original animal-vegetal and dorsoventral axes, many fragments generate novel axial properties. These results indicate that axial properties set up and used during normal development in C. lacteus can be completely reorganized during the course of regulation. While certain embryonic axes, such as the animal-vegetal and dorsoventral axes, appear to be set up prior to first cleavage, these axes and associated cell fates are not irreversibly fixed until later stages of development in normal intact embryos. In C. lacteus, the process whereby these properties are ultimately determined is apparently controlled by complex sets of cell-cell interactions.
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  • 8
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    Plant cell reports 15 (1996), S. 833-835 
    ISSN: 1432-203X
    Keywords: Ferricyanide reduction ; Nitrogen ; Regulation ; Rosa damascena ; Suspension culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ability of suspension-cultured rose (Rosa damascena Mill. cv Gloire de Guilan) cells to reduce ferricyanide is decreased by 50% during an overnight incubation in a low-nutrient (1 mM CaCl2, 0.1 mM KCl) solution. This loss is not observed when nitrate and/or glutamate is added to the low-nutrient medium, but it occurs in medium containing all the components needed for normal growth except nitrate plus glutamate. Thus, the cells possess both constitutive and inducible enzymes for the reduction of ferricyanide, and nitrate or glutamate is both necessary and sufficient to stimulate the production of the inducible enzyme.
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  • 9
    ISSN: 1432-2048
    Keywords: Key words: ADP-glucose pyrophosphorylase B (small) subunit ; Transcription ; Regulation ; Solanum ; Lycopersicon ; Sucrose induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The 5′-flanking region of a B (small) subunit gene of ADP-glucose pyrophosphorylase (EC 2.2.7.27) – called the agpB1 promoter – was cloned from the potato cultivar Désirée and its activity studied in transgenic potato (Solanumtuberosum L.) and tomato (Lycopersiconesculentum Mill.) plants using the gusA reporter gene. In potato, high β-glucuronidase (GUS) activity was found in the storage tissues of developing tubers, but gusA expression was also detected in phloem-associated parenchymas in stolons, stems and petioles, as well as in the starch sheath adjacent to the vascular tissues in leaf veins, stems and petioles. In leaves, promoter activity was limited to stomatal guard cells and to the starch sheath of the major veins, with no detectable activity in the mesophyll. No expression was observed in roots. β-Glucuronidase activity was finally detected in pollen grains and in ovary placental tissues. The potato promoter::gusA construct was introduced in transgenic tomatoes and was shown to be highly regulated during fruit development, with a tight parallelism between GUS activity, the extractable ADP-glucose pyrophosphorylase activity and fruit starch content. In conclusion, the agpB1 promoter appears to be specific to sink tissues, contrasting with the sAGP gene recently described by P.A. Nakata and T.W. Okita (1996 Mol Gen Genet 250: 581–592) which is transcribed in both sink and source tissues. Furthermore, and in contrast to sAGP, agpB1 transcription is stimulated by sucrose.
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  • 10
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    Sexual plant reproduction 10 (1997), S. 300-304 
    ISSN: 1432-2145
    Keywords: Key words Embryo sac ; Structural changes ; Mutation ; Nicotiana tabacum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The semisterile tobacco plant BG-141.4 was produced using both irradiation with X-rays and anther culture. The embryological investigation of the progeny of this plant following selfing (R1) revealed disturbances in the structure of the mature embryo sacs (ESs). The major abnormality was a decrease in cell number in the ESs. Other abnormalities included disturbances in the distribution of nuclei and in cell differentiation. The overall frequency of abnormal ESs in individual plants investigated varied from 8% to 83%, while the frequency of ESs with a reduced number of cells varied from 5% to 72%. Since the examination of three subsequent generations - R2, R3 and R4 - showed similar results, it is concluded that a mutation has been induced. Its main phenotypic manifestation is most likely related to its lacking one or two nuclear division(s) during the coenocytic stage of megagametogenesis. The penetrance of the mutation varies widely.
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  • 11
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    Plant cell reports 17 (1997), S. 32-38 
    ISSN: 1432-203X
    Keywords: Key words Tobacco ; Nicotiana tobacum ; Mutation ; Auxin transport ; Indole acetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A mutation in tobacco (Nicotiana tabacum L. cv `Xanthi') called lat (low auxin transport) that changes many morphogenic features throughout the life of the plant has been isolated. Abnormalities were observed in seed development, embryogenesis, cotyledon formation, leaf initiation and development, leaf veination pattern, and flower development. Selfed R2 lat mutant plants set between 60% and 90% fewer seeds than wild-type tobacco, and about 10% of these seeds did not germinate. Non-germinating seeds contained either abnormal embryos or abnormal endosperm tissues. There was no uniformity in the stage at which embryonic development ceased in the aberrant seeds. Seedlings often revealed abnormal and highly varied phenotypes after germination. In some of these cases, cotyledons were heart-shaped, fused, cup-shaped, or cylindrical. Leaf morphology ranged from normal to cup-shaped, and some leaves occasionally produced shoots from the leaf midvein. Flowers ranged from normal to compound with occasional fused floral parts or split petals. Stamens were sometimes petal-like. This unusual assortment of phenotypic changes suggested that the mutation might affect a basic component of plant metabolism. We found that polar transport of indole-3-acetic acid (IAA) was reduced to about 9–19% of the wild-type level in the inflorescence axis of selfed R2 lat mutants. In addition, supplementation of 1-naphthaleneacetic acid (NAA) to sterile media suppressed some of the abnormalities of the lat mutation so long as the plants grew there. Similarities in the phenotype of embryos, cotyledon and leaf shapes, translocation of labeled IAA, and response to applied NAA indicate that the lat locus of tobacco may be analogous to the pin locus of Arabidopsis, or produce a protein that functions in the same auxin-transport pathway.
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  • 12
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    Current genetics 8 (1984), S. 253-259 
    ISSN: 1432-0983
    Keywords: Regulation ; Alcohol dehydrogenases ; Aspergillus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Aspergillus nidulans there are two alcohol dehydrogenases. In the presence of ethanol, alcohol dehydrogenase I (AHH I) is induced and alcohol dehydrogenase II (ADH II) is repressed. ADH I and ADH II have molecular weights of 39,000 and 36,000 respectively. At least ADH I is under the control of alcR, a transacting regulatory gene that is adjacent to alcA (the structural gene for ADH I, Pateman et al. 1983). Mutations in the alcR regulatory gene result in non inducibility of ADH I specific mRNA. Extreme alcA and alcR mutations result in derepressed levels of ADH II, and it is not clear whether alcR controls ADH II directly or through its control of ADH I synthesis. Both enzymes are subject to carbon catabolite repression. Induction of ADH I and ADH II operates at the level of synthesis or processing of mRNA.
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  • 13
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    Current genetics 31 (1997), S. 139-143 
    ISSN: 1432-0983
    Keywords: Key words Ribosomal protein ; Fungus ; Neurospora crassa ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Neurospora crassa ribosomal protein gene, crps-7, was isolated from a genomic DNA library closely linked to the morphological gene ro-2. Sequence analysis and a computerized database search revealed a high degree of homology to the Xenopus laevis rps8 and rat rps7 gene, as well as to uncharacterized ORFs from two yeast species. Comparison with a nearly full-length cDNA clone revealed two introns, one of which is in a conserved position shared with the Xenopus gene. Although a number of sequence motifs common to other N. crassa ribosomal protein genes are present upstream of the crps-7 gene, mRNA abundance is not tightly regulated by carbon availability. Relative transcript levels during nitrogen limitation and thermal stress were also examined.
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  • 14
    ISSN: 1432-0983
    Keywords: Thymidylate auxotrophy ; Mutation ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A diploid yeast thymidylate auxotroph was grown under conditions of thymidylate stress ranging from depletion to excess levels of the nucleotide. High concentrations of thymidylate were mutagenic and recombinagenic whereas starvation for thymine nucleotides was recombinagenic and only slightly mutagenic. These results are discussed in relation to possible mutagenic and recombinagenic mechanisms of nucleotide pool imbalances.
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  • 15
    ISSN: 1432-0983
    Keywords: Key words Nitrate reductase ; Regulation ; Arylsulphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Chlamydomonas reinhardtii, the expression of the nit1 gene encoding nitrate reductase is dependent on the nature of the nitrogen source and on other environmental factors. We have fused the nit1 promoter region to the arylsulphatase (ars) reporter gene lacking its own promoter and introduced this chimeric construction (nit1/ars) into a wall-less strain of C. reinhardtii. A new and sensitive method, based on the use of α-naphthylsulphate as a substrate and a diazonium salt as a chromogenic post-coupling agent, was developed to detect the activity of arylsulphatase (an enzyme which is almost completely secreted in the culture medium) both in vitro and in agar plates. The transformants carrying nit1/ars did not express arylsulphatase when grown in ammonium-sufficient medium but readily accumulated the enzyme in ammonium-free medium either supplemented, or not supplemented, with nitrate or nitrite. The nit1/ars construct, however, was not expressed in the nit2 mutant lacking a specific transcription regulator controlling the expression of nit1. These results, together with the observation that the transcription of nit1/ars is initiated at the same sites as the nit1 endogenous gene, confirms the hypothesis that the regulation of nit1 expression takes place mainly at the transcriptional level. The expression of the ars gene from the nit1 promoter was high enough to allow direct measurements of arylsulphatase activities in pools of transformants without prior isolation of nit1/ars clones. This original procedure has permitted the analysis of the effects of nested deletions in the nit1 promoter region on the expression of the reporter gene. The results indicate that the –282 to –198 sequence is required for transcription to occur and that the –751 to –282 region contains several elements mediating nit1 expression.
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  • 16
    ISSN: 1432-0983
    Keywords: Neurospora crassa ; Nitrogen metabolism ; Regulation ; Heterokaryons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nit-2 gene of Neurospora crassa is a major regulatory gene for control of nitrogen metabolism. Synthesis of the enzyme L-amino acid oxidase requires a functional nit-2 gene product and is also controlled by amino acid induction and nitrogen catabolite repression. Electrophoretic variants of L-amino acid oxidase have been employed to demonstrate that in heterokaryons, a nit-2 + gene product can turn on the expression of this enzyme in its own nucleus and also in nuclei that possess a nit-2 mutant. This trans-nuclear effect is only partial since the variant coded for in the nucleus containing the nit-2 mutant allele is always present in lower amounts than the alternative form. Two additional putative nitrogen control genes, MS5 and en(am)1, have been found to have clear effects upon the expression of L-amino acid oxidase. The en(am)1 mutant appears to result in an unusual case of reversal of the control present in wild-type: the enzyme is expressed in a constitutive fashion and inducers, required for enzyme synthesis in wild-type, actually reduce the level of L-amino acid oxidase in en(am)1. The MS5 mutant shows a substantial release from the usual nitrogen catabolite repression exerted by glutamine in wild-type.
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  • 17
    ISSN: 1432-0983
    Keywords: Regulation ; Lactate utilization ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A strain dependent growth on lactate in the presence of antimycin A (AA) has been observed — the strain D261 can grow on lactate and AA, whereas in the strain K8/6C antimycin A prevents the utilization of lactate and the induction of LDH. Genetic analysis demonstrates that growth on lactate in the presence of AA segregates from D261 as a single nuclear factor which we indicate by ALG1 and alg1 in its dominant and recessive states. alg1 complements the gene(s) which give(s) rise to the same phenotype in K8/6C. The analysis of the regulation by lactate of LDH in the absence and presence of AA and in rho − cells shows that growth on lactate and antimycin A is not corretated with the induction by lactate of LDH.
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  • 18
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    Archives of microbiology 116 (1978), S. 77-83 
    ISSN: 1432-072X
    Keywords: Pseudomonas oxalaticus OX1 ; Diauxic growth ; Oxalate and formate ; Calvin cycle ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diauxic growth of Pseudomonas oxalaticus was observed on a mixture of formate and oxalate in batch cultures. In the first phase of growth only formate was used. The capacity to oxidize oxalate appeared during the lag phase of 2–4 h after the exhaustion of formate and was followed by a second phase of growth on oxalate. The rate of autotrophic 14CO2 fixation measured in washed cell suspensions decreased markedly in this second growth phase on the addition of oxalate. In mixtures of formate with acetate, glyoxylate or glycollate, simultaneous utilization of both substrates was observed. During growth on acetate plus formate formate-oxidizing capacity remained low. With low acetate concentrations, sufficient formate remained after the exhaustion of acetate to support a second growth phase on formate. This phase followed a 1.5–2 h lag, during which formate-oxidizing capacity increased and the Calvin cycle enzymes were synthesized. In mixtures of formate with glyoxylate or glycollate, the formate-oxidizing capacity was high, formate was oxidized rapidly, and no second growth phase was seen. In these latter mixtures high activities of a membrane-bound, phenazine methosulphate/2,6-dichlorophenolindophenollinked formate dehydrogenase and low activities of the soluble NAD-linked formate dehydrogenase were detected. The synthesis of ribulose-1,5-diphosphate carboxylase was totally repressed during growth on formate plus glycollate and partially repressed on formate plus glyoxylate. The regulation of Calvin cyclus enzymes in Pseudomonas oxalaticus is discussed.
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  • 19
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    Archives of microbiology 117 (1978), S. 123-129 
    ISSN: 1432-072X
    Keywords: Hydrogenase ; Regulation ; CO2-effect ; H2-effect ; Mixotrophy ; Reverse electron flow ; Alcaligenes eutrophus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Forty-four mutants of Alcaligenes eutrophus H 16 were isolated which grew poorly or not at all under autotrophic conditions. Four types were characterized with respect to their defects and their physiological properties. One mutant lacked both enzymes specific for autotrophic CO2 fixation, another one lacked both hydrogenases, and two mutants lacked either the membrane-bound or the soluble hydrogenase. Comparing the results of studies on these mutant types, the following conclusions were drawn: the lack of each hydrogenase enzyme could be partially compensated by the other one; the lack of membrane-bound hydrogenase did not affect autotrophic growth, whereas the lack of the soluble hydrogenase resulted in a decreased autotrophic growth rate. When pyruvate as well as hydrogen were supplied to the wild-type, the cell yield was higher than in the presence of pyruvate alone. Mutant experiments under these conditions indicated that either of both hydrogenases was able to add to the energy supply of the cell. Only the soluble hydrogenase was involved in the control of the rate of hydrogen oxidation by carbon dioxide; the mutant lacking this enzyme did not respond to the presence or absence of CO2. The suppression of growth on fructose by hydrogen could be mediated by either of both hydrogenases alone.
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  • 20
    ISSN: 1432-072X
    Keywords: Rhodopseudomonas capsulata ; Continuous cultures ; Nitrogenase ; Glutamine synthetase ; H2 production ; Regulation ; Light ; Ammonia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen-limited continuous cultures of Rhodopseudomonas capsulata were used to investigate some aspects of the regulation of nitrogenase activity. The role of glutamine synthetase (GS) in this regulation was examined by measuring changes of its adenylylation state when the light intensity and the nitrogen source were varied. Maximal nitrogenase activity was observed at a dilution rate corresponding to about one third of the maximum specific growth rate (μmax), both in ammonia- and in glutamate-limited cultures. At higher dilution rates, both GS and nitrogenase were inactivated by ammonia. Determination of the kinetics of inhibition of both enzymes indicated that the degree of inactivation of nitrogenase and the adenylylation state of GS were not closely related. Increase of light intensity stimulated nitrogenase activity dramatically. Conversely, a shift-down in light intensity to a limiting value resulted in a decrease of nitrogenase activity suggesting that synthesis was inhibited. On the other hand, the adenylylation state of glutamine synthetase appeared to be unaffected by changes in light intensity, indicating that GS is probably not involved in the regulation of nitrogenase expression by light.
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  • 21
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    Archives of microbiology 112 (1977), S. 283-285 
    ISSN: 1432-072X
    Keywords: Wine yeasts ; Sulfur metabolism ; Regulation ; Sulfate uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five different strains of wine yeasts were investigated with respect to active uptake of [35S] sulfate and its regulation by methionine. Considerable differences exist between “low” and “high” sulfite-producing strains in the initial velocity of sulfate uptake. Further differences were established in repression of sulfate permease by l-methionine, most evident in a total lack of repression in one of the “high” sulfite producers. These findings explain in part variable sulfite and sulfide formation.
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  • 22
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    Archives of microbiology 111 (1977), S. 265-270 
    ISSN: 1432-072X
    Keywords: Ammonia assimilation ; Glutamine synthetase ; Continuous culture ; Regulation ; Inactivation ; New synthesis ; Schizosaccharomyces pombe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glutamine synthetase (GS) activity of Schizosaccharomyces pombe 972 was high in ammonia-limited cultures, low in phosphate-and sulphate-limited cultures and not detected in glucose-limited cultures. When ammonia was ‘pulsed’ into an ammonia-limited culture then GS activity decreased at a rate faster than that calculated if enzyme synthesis ceased and enzyme was diluted out by growth. Enzyme activity increased in ammonia-starved, phosphate-limited cultures and in the ammonia ‘pulse’ system when the added ammonia had been utilised. These increases in enzyme activity were prevented by the presence of 100 μg/ml cycloheximide. GS activity was inversely related to the intracellular concentration of glutamate.
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  • 23
    ISSN: 1432-072X
    Keywords: Citric acid production ; Glyoxylate cycle ; Isocitrate dehydrogenase ; Energy charge ; Regulation ; Saccharomycopsis lipolytica
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    Notes: Abstract The mechanism of the massive extracellular production of citric and isocitric acids by Saccharomycopsis lipolytica grown on n-paraffins has been studied. When growth stops, because of nitrogen limitation, the intracellular concentration of ATP sharply rises whereas that of AMP and ADP decreases to a low level. At the same time production of acids begins. The activity of the NAD-dependent isocitrate dehydrogenase which requires AMP for activity becomes very low and prevents the oxidative function of the citric acid cycle whereas isocitrate lyase is not inhibited. As citrate synthase inhibition by ATP appears to be insufficient to stop n-paraffin degradation, citric and isocitric acids accumulation can take place. Massive excretion of these acids, however, probably still involves other physiological changes brought about by nitrogen limitation, possibly some permeabilization of the cell to these acids.
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  • 24
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    Archives of microbiology 119 (1978), S. 323-325 
    ISSN: 1432-072X
    Keywords: Halobacterium ; Chemostat ; Energetics ; Bacteriorhodopsin ; Oxygen ; Growth rate ; Membrane ; Regulation
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    Topics: Biology
    Notes: Abstract The independent effects of oxygen tension and growth rate on bacteriorhodopsin synthesis in Halobacterium halobium have been studied in chemostat cultures. Bacteriorhodopsin synthesis occurs only at low growth rates and is stimulated by low oxygen tension. Fast growth rates override the stimulatory effects of oxygen tension, with the result that bacteriorhodopsin can scarcely be detected. Illumination of cultures maintained at low growth rate and low oxygen tension significantly increases the steady state cell yield. This finding suggests that under these conditions the purple membrane proton pump is coupled to energy transduction.
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  • 25
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    Archives of microbiology 117 (1978), S. 221-226 
    ISSN: 1432-072X
    Keywords: Nematophagous fungus ; Giant functional traps ; Mutation ; Development
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    Topics: Biology
    Notes: Abstract Mutagenesis with nitrosoguanidine yielded two classes of ring trap mutants in the predacious HyphomyceteDactylella brochopaga: strains which could make no traps and those with a proportion of giant, functional traps. A third strain, derived from a trapless strain made abnormally small functional traps. The giant traps are described, together with developmental abnormalities they sometimes display. The characteristics of the chief mutant strains are discussed.
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  • 26
    ISSN: 1432-072X
    Keywords: Photosynthesis ; Regulation ; Thioredoxin ; Cyanobacterium ; Chromatium
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    Topics: Biology
    Notes: Abstract Enzymes that are regulated by the ferredoxin/thioredoxin system in chloroplasts — fructose-1,6-bisphosphatase (FBPase), sedoheptulose-1,7-bisphosphatase purified from two different types of photosynthetic prokaryotes (cyanobacteria, purple sulfur bacteria) and tested for a response to thioredoxins. Each of the enzymes from the cyanobacterium Nostoc muscorum, an oxygenic organism known to contain the ferredoxin/thioredoxin system, was activated by thioredoxins that had been reduced either chemically by dithiothreitol or photochemically by reduced ferredoxin and ferredoxin-thioredoxin reductase. Like their chloroplast counterparts, N. muscorum FBPase and SBPase were activated preferentially by reduced thioredoxin f. SBPase was also partially activated by thioredoxin m. PRK, which was present in two regulatory forms in N. muscorum, was activated similarly by thioredoxins f and m. Despite sharing the capacity for regulation by thioredoxins, the cyanobacterial FBPase and SBPase target enzymes differed antigenically from their chloroplast counterparts. The corresponding enzymes from Chromatium vinosum, an anoxygenic photosynthetic purple bacterium found recently to contain the NADP/thioredoxin sytem, differed from both those of cyanobacteria and chloroplasts in showing no response to reduced thioredoxin. Instead, C. vinosum FBPase, SBPase, and PRK activities were regulated by a metabolite effector, 5′-AMP. The evidence is in accord with the conclusion that thioredoxins function in regulating the reductive pentose phosphate cycle in oxygenic prokaryotes (cyanobacteria) that contain the ferredoxin/thioredoxin system, but not in anoxygenic prokaryotes (photosynthetic purple bacteria) that contain the NADP/thioredoxin system. In organisms of the latter type, enzyme effectors seem to play a dominant role in regulating photosynthetic carbon dioxide assimilation.
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  • 27
    ISSN: 1432-072X
    Keywords: Key wordsEscherichia coli ; (Mixed acid) fermentation ; Facultative anaerobic metabolism ; O2 ; Aerobic ; respiration ; Regulation ; FNR ; ArcA
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    Topics: Biology
    Notes: Abstract In an oxystat, the synthesis of the fermentation products formate, acetate, ethanol, lactate, and succinate of Escherichia coli was studied as a function of the O2 tension (pO2) in the medium. The pO2 values that gave rise to half-maximal synthesis of the products (pO0.5) were 0.2–0.4 mbar for ethanol, acetate, and succinate, and 1 mbar for formate. The pO0.5 for the expression of the adhE gene encoding alcohol dehydrogenase was approximately 0.8 mbar. Thus, the pO2 for the onset of fermentation was distinctly lower than that for anaerobic respiration (pO0.5≤ 5 mbar), which was determined earlier. An essential role for quinol oxidase bd in microaerobic growth was demonstrated. A mutant deficient for quinol oxidase bd produced lactate as a fermentation product during growth at microoxic conditions (approximately 10 mbar O2), in contrast to the wild-type or a quinol-oxidase-bo-deficient strain. In the presence of nitrate, the amount of lactate was largely decreased. Therefore, under microoxic conditions, the pO2 appears to be too high for (mixed acid) fermentation to function and too low for aerobic respiration by quinol oxidase bo.
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  • 28
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    Archives of microbiology 115 (1977), S. 103-108 
    ISSN: 1432-072X
    Keywords: Root nodule symbiosis ; Rhizobium meliloti ; Medicago sativa ; Nitrogenase activity ; Regulation
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    Topics: Biology
    Notes: Abstract Symbiotic nitrogen fixation of Rhizobium meliloti bacteroids in Medicago sativa root nodules was suppressed by several inorganic nitrogen sources. Amino acids like glutamine, glutamic acid and aspartic acid, which can serve as sole nitrogen sources for the unnodulated plant did not influence nitrogenase activity of effective nodules, even at high concentrations. Ammonia and nitrate suppressed symbiotic nitrogen fixation in vivo only at concentrations much higher than those needed for suppression of nitrogenase activity in free living nitrogen fixing bacteria. The kinetics of suppression were slow compared with that of free living nitrogen fixing bacteria. On the other hand, nitrite, which acts as a direct inhibitor of nitrogenase, suppressed very quickly and at low concentrations. Glutamic acid and glutamine enhanced the effect of ammonia dramatically, while the suppression by nitrate was enhanced only slightly.
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  • 29
    ISSN: 1432-072X
    Keywords: Physarum polycephalum ; Amoebae ; Aminopeptidases ; Acid proteases ; Regulation ; Development ; Differential gene activity
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    Topics: Biology
    Notes: Abstract The cultivation of Physarum polycephalum amoebae in two media with different protein contents revealed a regulation of aminopeptidases and proteases depending on the albumin content of the medium: in growing amoebae and plasmodia the aminopeptidases have similar isoenzyme patterns and relative activities against nitroanilides. One alanine and four leucine aminopeptidase isoenzymes were found within the slightly acid pH range. During growth amoebae secrete—different from plasmodia—leucine aminopeptidase into the medium with low protein content. In an albumin-rich medium additional alanine aminopeptidase activity was found. Out of nine plasmodial proteases four were found in amoebae too. Only one band (pI 3.6) was present in the protein-poor medium. No protease activity could be detected in the proteinrich medium.
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  • 30
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    Archives of microbiology 166 (1996), S. 141-150 
    ISSN: 1432-072X
    Keywords: Key words CBB pathway ; CO2 fixation ; Transcription ; Regulation ; Proteobacteria ; Cyanobacteria
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    Topics: Biology
    Notes: Abstract In phototrophic and chemoautotrophic proteobacteria, genes encoding enzymes of the Calvin-Benson-Bassham pathway of CO2 fixation are often found in clusters that are transcribed from a single promoter under control of the LysR-type transcriptional activator, CbbR. Mutations affecting CbbR prevent induction of cbb genes. Gel-retardation assays have demonstrated CbbR binding to putative regulatory regions of cbb operons, and in two cases, footprinting experiments have delimited the nucleotide sequence protected by CbbR. Fusion of cbb control sequences to reporter genes has allowed the regions required for promoter activity to be defined, and recent experiments indicate that the cbb regulon in Rhodobacter is controlled by a global two-component signal transduction system that also regulates other metabolic processes in this organism. Different ways of regulating CBB cycle enzymes that also have roles in heterotrophic metabolism have recently been discovered. In cyanobacteria, the genes of the CBB pathway are organized and regulated differently, and these oxygen-evolving phototrophic bacteria have evolved different strategies to control the assimilation of CO2.
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  • 31
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    Archives of microbiology 113 (1977), S. 265-274 
    ISSN: 1432-072X
    Keywords: Thiobacillus A2 ; Glucose metabolism ; Regulation ; Enzymology ; Radiorespirometry ; Multiple catabolic pathways
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    Topics: Biology
    Notes: Abstract Enzymes essential to the operation of the Embden-Meyerhof glycolytic pathway, the Entner-Doudoroff pathway and oxidative pentose phosphate pathway were present in Thiobacillus A2 grown on glucose and other sugars. Radiorespirometry under various conditions with Thiobacillus A2 oxidising glucose specifically labelled with 14C in carbon atoms 1, 2, 3, 3+4, 6 or universally labelled demonstrated the simultaneous operation of the Embden-Meyerhof (48%), Entner-Doudoroff (28%), and pentose phosphate (24%) pathways in release of carbon dioxide from glucose. Growth on succinate, or autotrophically on formate or thiosulphate resulted in repression of most enzymes of the pathways, but high aldolase levels were retained indicating its role in gluconeogenesis and the Calvin cycle. Different fructose diphosphatase activities were found in succinate- and thiosulphate-grown organisms. The results indicate that all three major catabolic pathways for glucose function in Thiobacillus A2 grown on sugars. Thiobacillus acidophilus showed a different radiorespirometric pattern and apparently used the Entner-Doudoroff (64.5%) and pentose phosphate (35.5%) pathways, but showed unusually high release of carbon atom 6, as was also found for T. ferrooxidans.
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  • 32
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    Archives of microbiology 114 (1977), S. 203-210 
    ISSN: 1432-072X
    Keywords: Hydrogen bacteria ; Alcaligenes eutrophus H 16 ; Leucine biosynthesis ; α-isopropylmalate synthase ; Regulation ; Feedback inhibition ; Relief of inhibition by valine and isoleucine ; Inhibition by α-ketoisocaproate ; Temperature anomaly
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    Notes: Abstract The α-isopropylmalate synthase (EC 4.1.3.12) from Alcaligenes eutrophus H 16 was inhibited by l-leucine and α-ketoisocaproate. The extent of inhibition was influenced by substrate- and inhibitor concentrations as well as by the pH. Intermediary plateaus, which always appeared in the inhibition curves, suggested cooperative effects. The maximal Hill coefficient was found to be two. At low concentrations of leucine the inhibition mechanism was of the competitive type with respect to substrate acetyl coenzyme A and of the noncompetitive type with respect to substrate α-ketoisovalerate. The inhibition was specifically relieved by the addition of valine or isoleucine. The anomalous effect of temperature on enzyme activity was diminished by leucine. The Arrhenius energy of the reaction increased from about 11 kcal/mole in the absence of leucine to about 18 kcal/mole in the presence of leucine. The further addition of valine reversed this effect. The physiological relevance of the α-ketoisocaproate-mediated inhibition is discussed.
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  • 33
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    Archives of microbiology 117 (1978), S. 53-60 
    ISSN: 1432-072X
    Keywords: Rhodopseudomonas palustris ; Nitrogenase ; Regulation ; Ammonia ; Cross reactivity
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    Topics: Biology
    Notes: Abstract Ammonium salts, glutamine, asparagine, and urea cause an immediate inactivation (switch-off) of light-dependent acetylene reduction in intact cells of the photosynthetic bacteriumRhodopseudomonas palustris. This effect is reversible showing the same kinetic pattern of inactivation and reactivation with all effector compounds. Its duration depends on the amount of effector added to the cells. Both nitrogenase components are found catalytically active in a cell-free preparation after enzyme switch-off in vivo. Involvement of the ammonia assimilating system in this regulatory mechanism is indicated by the following observations: ammonia uptake during the switch-off period, resumption of acetylene reduction after disappearance of ammonia from the outer medium, and persistence of enzyme switch-off with dihydrogen and thiosulfate as electron donors in the absence of an additional carbon source. Nitrogenase activity in crude extracts is non-linear with time and is stimulated by manganese ions. After resolution of nitrogenase into its MoFe-protein and Fe-protein these properties are lost, indicating the presence of an activating factor. Nitrogenase ofR. palustris cross reacts reciprocally with the complementary proteins ofAzotobacter vinelandii, but not with those ofClostridium pasteurianum.
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  • 34
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    Archives of microbiology 112 (1977), S. 173-177 
    ISSN: 1432-072X
    Keywords: cAMP ; Regulation ; Chlorophyll synthesis ; Chlorella fusca
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    Topics: Biology
    Notes: Abstract The intracellular concentration of cAMP in the green alga Chlorella fusca was in the range of 2 · 10-9 to 10-8 moles/g dry weight and was strongly dependent on the growth conditions. The cAMP level was high with high light intensity, low nitrate or glucose concentration. Intracellular cAMP increased only by factor of 2 when high amounts (up to 10-3 M) of cAMP were added to the medium. Most of the given cAMP was converted to 5′-AMP. Addition of cAMP had little effect on the chlorophyll content of the cells, only at 10-6 M some enhancement in photoautotrophic cultures was observed. On the other hand high amounts of cAMP in the medium increased the growth rate. DBcAMP* showed a positive effect on chlorophyll synthesis and growth rate at much lower concentrations compared to cAMP. Stimulation effects of exogenous cAMP on the synthesis of chlorophyll were also observed in mixotrophic cultures with a high glucose/nitrate ratio, conditions where chlorophyll synthesis is repressed. Similar to autotrophic conditions DBcAMP was more effective than cAMP. These data indicate that cAMP may act in a system controlling the chlorophyll content of the cells in response to nutrients or light.
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  • 35
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    Archives of microbiology 139 (1984), S. 28-32 
    ISSN: 1432-072X
    Keywords: Cyanobacterium ; Phosphate ; Uptake ; Kinetics ; Regulation ; Pulse ; Steady state
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    Topics: Biology
    Notes: Abstract In order to study phosphate uptake kinetics the cyanobacteriumOscillatoria agardhii was grown in continuous culture under a phosphorus limitation. The affinity of the uptake system reflected in the initial slope of the uptake rate versus external substrate concentration curve (dV/ds) was found to be unaffected by the growth wate. The maximum phosphate uptake rate (V m ) decreased as the growth rate was increased. Attempts were made to relate the decrease ofV m to the increase in phosphorus content of the cells that occurred a higher growth rates. Accumulation of phosphate during pulse experiments indeed resulted in a decrease ofV m . However feedback regulation ofV m by accumulated phosphorus was found to occur only to a small extent in steady state growing cells. The main part of the regulation of the activity of the phosphate uptake system seemingly is determined by a long term process that is, at least longer than 2 h. The presence of short term feedback inhibition by accumulated phosphorus on the activity of the uptake system provides an explanation of the phenomenon thatOscillatoria agardhii is not able to grow at nearμ max growth rates under a phosphorus limitation.
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  • 36
    ISSN: 1432-1327
    Keywords: Key words High-potential ; Iron-sulfur protein ; Redox ; Mutation
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The recombinant high-potential iron-sulfur protein (HiPIP) iso-I from Ectothiorhodospira halophila has been mutated at position 68. The αC of Val 68 is within a 0.6-nm sphere from the closest iron ion of the cluster. The valine residue has been replaced by a negatively charged glutamate residue (V68E) and by a positively charged lysine residue (V68K). With respect to the recombinant wild-type protein the reduction potentials of the V68E and V68K variants are –21±2 and +29±2 mV respectively (200 mM NaCl, pH 7, 25  °C). The solution structure of the V68E mutant was solved up to a pairwise RMSD of 66 pm for backbone atoms and 138 pm for all heavy atoms. The structure of the variant is very similar to that of recombinant wild type, indicating that the observed changes in reduction potentials are largely due to the effect of the introduced charges. It is proposed that the valence distribution within the oxidized iron-sulfur cluster is affected only slightly by the change in charge at position 68, but consistently with a simple electrostatic model.
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  • 37
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    Journal of evolutionary economics 7 (1997), S. 415-433 
    ISSN: 1432-1386
    Keywords: Key words: Forward induction ; Deviation ; Discrete evolutionary processes ; Mutation ; Limit distribution ; JEL-classification: C70; C72
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    Topics: Economics
    Notes: Abstract. The paper deals with the driving forces behind behavior selection in both forward induction refinements and discrete evolutionary processes with mutations. Its main purpose is to analyse an important difference due to the support of the mutations. It shows that similar driving forces can allow to outweigh this difference. To this aim it constructs the limit Markov graph, a tool used to compute the probabilities in the limit distribution.
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  • 38
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    Journal of mathematical biology 35 (1997), S. 321-343 
    ISSN: 1432-1416
    Keywords: Key words: Sequence space ; Selection ; Mutation ; Error threshold ; Hopf bifurcations
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    Topics: Biology , Mathematics
    Notes: Abstract.  Deterministic models of mutation and selection in the space of (binary) nucleotide-type sequences have been investigated for haploid populations during the past 25 years, and, recently, for diploid populations as well. These models, in particular their ‘error thresholds’, have mainly been analyzed by numerical methods and perturbation techniques. We consider them here by means of bifurcation theory, which improves our understanding of both equilibrium and dynamical properties. In a caricature obtained from the original model by neglecting back mutation to the favourable allele, the familiar error threshold of the haploid two-class model turns out to be a simple transcritical bifurcation, whereas its diploid counterpart exhibits an additional saddle node. This corresponds to a second error threshold. Three-class models with neutral spaces of unequal size introduce further features. Such are a global bifurcation in haploid populations, and simple examples of Hopf bifurcations (as predicted by Akin’s theorem) in the diploid case.
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  • 39
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    Theoretical and applied genetics 65 (1983), S. 41-46 
    ISSN: 1432-2242
    Keywords: Triticum aestivum ; Wheat ; Protein ; Mutation
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    Topics: Biology
    Notes: Summary Poor adaptability or functional quality of much germplasm used for breeding high-protein hard red winter wheats prompted mutagenesis as an alternative means of increasing grain protein content. Four hard red winter wheat genotypes — KS644 (‘Triumph// Concho/Triumph’), ‘Kaw’, ‘Parker’, and ‘Shawnee’ — were treated with 0.40 M ethyl methanesulfonate (EMS). Advanced lines (M8-M10) were selected that had a 3-year mean grain protein advantage of 0.7% to 2.0% over controls. Increased grain protein content was generally associated with decreased grain yield and kernel weight, but some high-protein mutant lines had yields or kernel weights similar to those of original genotypes. Changes in height and lodging induced by EMS were generally favorable, most mutants being shorter and lodging less than controls, but blooming date was generally delayed, a deleterious change. One line also changed from resistant to segregating for wheat soil-borne mosaic virus. Mutant lines might be utilized in cross-breeding programs, particularly if negative pleiotropic effects and linkages are absent.
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  • 40
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    Theoretical and applied genetics 65 (1983), S. 225-230 
    ISSN: 1432-2242
    Keywords: Tissue culture ; Mutation ; Sequential mutations ; Rice ; Oryza sativa L.
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    Topics: Biology
    Notes: Summary Four mutations for early heading, albina, short culm and sterility were obtained in the progenies of twelve rice plants regenerated from a single callus of a rice seed. Studies on the segregation rates of these mutations revealed that for each mutation a single recessive gene was likely to be involved and that there was no linkage among the genes. The segregation pattern also showed that these mutations were induced in the following sequence: early heading, albina, and short culm and sterility during the stage of callus growth until the beginning of the regeneration of the rice plants.
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  • 41
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    Theoretical and applied genetics 50 (1977), S. 137-146 
    ISSN: 1432-2242
    Keywords: Sorghum ; Height ; Regulation ; Peroxidase
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    Topics: Biology
    Notes: Summary A relationship between height genes (dw locus) and perioxidase was demonstrated by extracting and determining peroxidase specific activity in internode tissue from different height isogenic lines of sorghum Sorghum bicolor (L.) Moench]. Tall plants (2 dwarf) had less peroxidase per gram tissue than their short counterparts (3 dwarf); their F1 offspring internodes were closer but had more peroxidase than the tall parent. Peroxidase in the F2 offspring was inversely related to their height and followed a simply-inherited pattern similar to that for height. Among different tissues analyzed, peroxidase concentration in roots was higher than in leaves and internodes, whole internode higher than in pith, and seed embryo higher than in endosperm. Peroxidase activity of nonviable seeds was negligible. Isoelectric focusing provided a more detailed peroxidase zymogram than did gel electrophoresis. Differences in peroxidase bands among tall and short parental plants, F1 and F2 segregating groups all appear to be reflected by intensity differences rather than by position or number of bands. Activities of nitrate reductase and acid phosphatase did not correlate with height. That finding provides a control and suggests that peroxidase activity is not associated with height by chance but may have a functional relationship.
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  • 42
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    Theoretical and applied genetics 67 (1984), S. 203-205 
    ISSN: 1432-2242
    Keywords: Ethyl methanesulphonate ; Mutation ; Myo-inositol ; Nicotiana tabacum, tobacco
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    Topics: Biology
    Notes: Summary Tobacco seeds treated with ethyl methanesulphonate produces mutations as well as physiological growth debility. The addition of myo-inositol to seeds undergoing mutagenic treatment stimulated growth and increased survival of subsequent plants with negligible effect on the mutation frequency.
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  • 43
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    Theoretical and applied genetics 53 (1978), S. 181-190 
    ISSN: 1432-2242
    Keywords: Pisum sativum ; Seed protein content ; Mutation ; Genotype-year-interaction
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    Topics: Biology
    Notes: Summary Seventeen X-ray and neutron induced mutants of the commercial variety ‘Dippes gelbe Victoria’ were analyzed with regard to their seed protein percentage. The interaction of genotypic and year effects in 1975 (normal weather conditions) and 1976 (extremely hot and dry) was also taken into consideration. To avoid undiscoverable environmental bias, the plants were grown in a nonstandard three-dimensional layout. Biometric analysis was done by using the theory of the general linear model with a formula-processing computer program. In the first year, significant genetically caused differences were found in the material. The bifurcated mutant 157A was especially of considerable interest because an improved protein content was combined with relative good yield. In the second year, no significant differences between the mutants were revealed, but all genotypes showed a similar good protein value of about 27%.
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  • 44
    ISSN: 1432-0878
    Keywords: Key words: Adrenoceptors ; Diurnal rhythms ; Regulation ; In situ hybridization ; Pineal gland ; Rat (Wistar)
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    Topics: Biology , Medicine
    Notes: Abstract. The rat pinealocyte is stimulated by norepinephrine, which is released from sympathetic nerve fibers innervating the gland. Norepinephrine binds to β1-adrenoceptors situated on the pinealocyte cell membrane. Ligand binding to these receptors exhibits a diurnal rhythm, with the largest number occurring in the late part of the light phase when the release of norepinephrine is minimal. By using in situ hybridization with a cDNA antisense oligonucleotide probe recognizing mRNA encoding the rat β1-adrenoceptor, we have demonstrated a stronger hybridization signal in the rat pineal gland than in other brain regions. Cells containing β1-mRNA are located in the superficial pineal gland, the deep pineal gland, and the pineal stalk. However, the number of receptors varies considerably between the individual pinealocytes. The β1-mRNA in situ hybridization signal for mRNA encoding the β1-adrenoceptor of the rat pineal has been quantified over a 24-h period; the strongest signal is found at mid-dark and the weakest signal at mid-light, indicating that the transcriptional regulation of β1-mRNA synthesis in the rat pineal is diurnal. In addition, maximal receptor protein expression occurs late in the light phase in the rat pineal and is thus considerably delayed compared with its peak mRNA synthesis. This lag time indicates that the β1-receptor is regulated at the translational or post-translational level. Removal of the sympathetic input to the pineal gland by superior cervical ganglionectomy decreases the β1-mRNA signal in the gland.
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  • 45
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    Molecular genetics and genomics 250 (1996), S. 207-213 
    ISSN: 1617-4623
    Keywords: Regulation ; C5a peptidase ; M protein ; Transcription termination ; Streptococcus pyogenes
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    Topics: Biology
    Notes: Abstract Streptococcal C5a peptidase (SCP), encoded byscpA inStreptococcus pyogenes, is a surface molecule which is able to cleave and inactivate the chemotactic factor C5a. ThescpA gene is part of thevir regulon and subject to positive regulation by the Mga protein. It is down-regulated compared to another Mga-activated gene,emm. A chloramphenicol acetyltransferase (CAT) reporter gene was used to measurescpA promoter activity. Previous work had shown that when a large portion of thescpA promoter region was deleted, expression of CAT increased relative to the wild-type. This deleted region was found to contain an inverted repeat. In this study we show that the inverted repeat in the leader mRNA is the site of transcription termination, which down-regulates expression ofscpA. This is a novel mechanism for regulation of gene expression inS. pyogenes. A specific deletion of the inverted repeat in thescpA promoter-CAT reporter construct was made using inverse PCR. Expression was measured from single-copy chromosomal integrants. When the inverted repeat was deleted, expression increased. Furthermore, Northern hybridization confirmed the existence of a truncated transcript, consistent with a transcription termination mechanism.
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  • 46
    ISSN: 1617-4623
    Keywords: Key words Salmonella typhimurium ; rpoS ; spv ; Virulence plasmid ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The SpvR protein is a DNA-binding protein of the LysR family, required for the transcription of the spvABCD virulence operon of Salmonella typhimurium. An alternative sigma factor, σS (RpoS), in conjunction with SpvR, controls the transcription of the spvR gene. In this study, we used a combination of primer extension experiments and deletion/fusion analyses of the spvR gene to identify sequences involved in spvR transcription in S. typhimurium. When induced in the stationary phase of growth in rich medium or during carbon starvation, transcription of spvR in S. typhimurium is driven by a single promoter (spvRp1) and initiates 17 nucleotides upstream of the spvR start codon. The level of spvR transcription originating at spvRp1 was 20-fold higher in the wild-type strain than in the rpoS mutant. In both strains, however, transcription at spvRp1 requires the SpvR protein. 5′ Deletions up to position −86, relative to the spvR start codon, did not inhibit inducibility by σS and/or SpvR. In contrast, 5′ deletion up to −75 abolished the activation of spvRp1 by SpvR in both the wild-type strain and rpoS mutant. Within the 11-bp sequence lying between position −86 and position −75, a 10-bp consensus motif TNTNTGCANA, present in both the spvR and spvA promoter regions, was identified and may contain the DNA recognition site for SpvR. In addition, we detected initiation of transcription within the spvR coding region. This finding may have implications for comparative studies of regulation with spvR gene fusions.
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  • 47
    ISSN: 1617-4623
    Keywords: Salmonella typhimurium ; rpoS ; spv ; Virulence plasmid ; Regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The SpvR protein is a DNA-binding protein of the LysR family, required for the transcription of thespvABCD virulence operon ofSalmonella typhimurium. An alternative sigma factor, σS (RpoS), in conjunction with SpvR, controls the transcription of thespvR gene. In this study, we used a combination of primer extension experiments and deletion/fusion analyses of thespvR gene to identify sequences involved inspvR transcription inS. typhimurium. When induced in the stationary phase of growth in rich medium or during carbon starvation, transcription ofspvR inS. typhimurium is driven by a single promoter (spvRp1) and initiates 17 nucleotides upstream of thespvR start codon. The level ofspvR transcription originating atspvRp1 was 20-fold higher in the wild-type strain than in therpoS mutant. In both strains, however, transcription atspvRp1 requires the SpvR protein. 5′ Deletions up to position −86, relative to thespvR start codon, did not inhibit inducibility by σS and/or SpvR. In contrast, 5′ deletion up to −75 abolished the activation ofspvRp1 by SpvR in both the wild-type strain andrpoS mutant. Within the 11-bp sequence lying between position −86 and position −75, a 10-bp consensus motif TNTNTGCANA, present in both thespvR andspvA promoter regions, was identified and may contain the DNA recognition site for SpvR. In addition, we detected initiation of transcription within thespvR coding region. This finding may have implications for comparative studies of regulation withspvR gene fusions.
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  • 48
    ISSN: 1573-5052
    Keywords: Fertilisation ; Flowers ; Germination ; Mutation ; Seed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A highland (altitude 1600 m) and a lowland (altitude –2 m) population of the perennial herb Silene vulgaris were tested on the effects of elevated levels of UV-B radiation on their reproductivity. Highland populations receive higher natural UV-B doses than lowland populations. Therefore adaptation to high UV-B levels of the highland population is to be expected. The lowland population showed a decrease in the number of seed producing flowers and the number of seeds produced per plant under elevated UV-B levels. The highland population increased the number of seeds per plant under elevated UV-B levels. In both populations individual seed mass as well as seed germination percentages were unaffected by the UV-B flux received by the parental plant. Possible effects of UV-B induced alterations in reproductivity on the geographical distribution of the different populations are discussed.
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  • 49
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    Molecular genetics and genomics 252 (1996), S. 275-283 
    ISSN: 1617-4623
    Keywords: Key words DNA mismatch repair ; MluI cell cycle box ; Mutation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Transcription of the Saccharomyces cerevisiae DNA mismatch repair genes PMS1, MSH2, and MSH6, a recently discovered homolog of the Escherichia coli mutS gene, was shown to be cell cycle regulated. In contrast, transcription of the MSH1, MSH3 and MLH1 genes was not regulated during the cell cycle. The MSH1 gene, which is thought to be involved in DNA mismatch repair in mitochondria, was also not induced under aerobic growth conditions. Regulation of the PMS1 gene was dependent on intact MluI cell cycle boxes, as demonstrated by analysis of a promoter mutant. Both reduced and increased expression of PMS1 resulted in a mitotic mutator phenotype. Analysis of mRNA levels was performed with a newly developed reverse transcription-PCR (polymerase chain reaction) approach using fluorescently labeled primers and an automated DNA sequencer for detection of PCR products.
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  • 50
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    Molecular genetics and genomics 250 (1996), S. 162-168 
    ISSN: 1617-4623
    Keywords: Key words DNA repair ; Regulation ; Gene fusion ; DRE element ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The interstrand cross-link repair gene SNM1 of Saccharomyces cerevisiae was examined for regulation in response to DNA-damaging agents. Induction of SNM1-lacZ fusions was detected in response to nitrogen mustard, cis-platinum (II) diamine dichloride, UV light, and 8-methoxypsoralen +UVA, but not after heat-shock treatment or incubation with 2-dimethylaminoethylchloride, methylmethane sulfonate or 4-nitroquinoline-N-oxide. The promoter of SNM1 contains a 15 bp motif, which shows homology to the DRE2 box of the RAD2 promoter. Similar motifs have been found in promoter regions of other damage-inducible DNA repair genes. Deletion of this motif results in loss of inducibility of SNM1. Also, a putative negative upstream regulation sequence was found to be responsible for repression of constitutive transcription of SNM1. Surprisingly, no inducibility of SNM1 was found after treatment with DNA-damaging agents in strains without an intact DUN1 gene, while regulation seems unchanged in sad1 mutants.
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  • 51
    Electronic Resource
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    Molecular genetics and genomics 250 (1996), S. 162-168 
    ISSN: 1617-4623
    Keywords: DNA repair ; Regulation ; Gene fusion ; DRE element ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The interstrand cross-link repair geneSNM1 ofSaccharomyces cerevisiae was examined for regulation in response to DNA-damaging agents. Induction ofSNM1-lacZ fusions was detected in response to nitrogen mustard, cis-platinum (II) diamine dichloride, UV light, and 8-methoxypsoralen + UVA, but not after heat-shock treatment or incubation with 2-dimethyl-aminoethylchloride, methylmethane sulfonate or 4-nitroquinoline-N-oxide. The promoter ofSNM1 contains a 15 bp motif, which shows homology to the DRE2 box of theRAD2 promoter. Similar motifs have been found in promoter regions of other damage-inducible DNA repair genes. Deletion of this motif results in loss of inducibility ofSNM1. Also, a putative negative up-stream regulation sequence was found to be responsible for repression of constitutive transcription ofSNM1. Surprisingly, no inducibility ofSNM1 was found after treatment with DNA-damaging agents in strains without an intactDUN1 gene, while regulation seems unchanged insad1 mutants.
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  • 52
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    Molecular genetics and genomics 256 (1997), S. 158-168 
    ISSN: 1617-4623
    Keywords: Key words Transposon ; Ac ; Regulation ; Zea mays ; Excision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants form their gametes late in somatic development and, as a result, often pass somatic mutations on to their progeny. Classic examples of this process are the germinal revertants of unstable, Ac/Ds transposon-induced kernel mutations in maize: frequent and early reversion events during somatic development are generally correlated with a high frequency of revertant gametes. We have characterized a Ds allele of the maize waxy(wx) gene, wx-m5:CS7, for which the correlation between somatic and germinal reversion frequencies no longer holds. The ability of wx-m5:CS7 (CS7) to produce revertant gametes is suppressed ∼100-fold in comparison with a second Ds allele, wx-m5:CS8 (CS8), which has an identical insertion at Wx and the same frequent and early somatic reversion pattern in endosperm. The excision of Ds from wx is not reduced 100-fold in the somatic tissues of CS7 plants as compared with CS8 plants. Suppressed formation of CS7 revertant gametes is independent of the Ac transposase source and is heritably passed to the embryos of progeny kernels; however, frequent and early somatic reversion is observed again in endosperms of these progeny kernels. This suppression appears to be caused by a dominant mutation in a trans-acting product that can suppress the germinal reversion of other Ds-induced alleles as well; the mutation is tightly linked to Wx but is not in the CS7 Ds itself. Taken together, the data suggest a novel mode of developmental control of Ac/Ds elements by the host plant, suppressing element excision in the shoot meristem.
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  • 53
    Electronic Resource
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    Molecular genetics and genomics 252 (1996), S. 275-283 
    ISSN: 1617-4623
    Keywords: DNA mismatch repair ; MluI cell cycle box ; Mutation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcription of theSaccharomyces cerevisiae DNA mismatch repair genesPMS1, MSH2, andMSH6, a recently discovered homolog of theEscherichia coli mutS gene, was shown to be cell cycle regulated. In contrast, transcription of theMSH1, MSH3 andMLH1 genes was not regulated during the cell cycle. TheMSH1 gene, which is thought to be involved in DNA mismatch repair in mitochondria, was also not induced under aerobic growth conditions. Regulation of thePMS1 gene was dependent on intactMluI cell cycle boxes, as demonstrated by analysis of a promoter mutant. Both reduced and increased expression ofPMS1 resulted in a mitotic mutator phenotype. Analysis of mRNA levels was performed with a newly developed reverse transcription-PCR (polymerase chain reaction) approach using fluorescently labeled primers and an automated DNA sequencer for detection of PCR products.
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  • 54
    ISSN: 1573-5117
    Keywords: Regulation ; River ; Benthos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstracts Changes in composition, numbers and biomass of benthic fauna of the Tees below Cow Green Reservoir and an unregulated tributary Maize Beck were followed between 1972 and 1975 and pre- and post-impoundment conditions were compared. Species diversity was lowest just below the dam and numbers and biomass were highest 240 m downstream of the dam. Faunal densities increased in the Tees after impoundment but in Maize Back no major changes were observed.
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  • 55
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    Empirica 23 (1996), S. 303-316 
    ISSN: 1573-6911
    Keywords: Regulation ; liquor ; fair trade ; L3 ; L5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Several estimation methods agree that state regulations such as resale price maintenance and retail price posting affected the prices of liquor brands up to the mid-1970s in the US states in which the distribution system is privately owned; before-versus-after analysis using the quasiexperimental method provides the strongest evidence. The effects of particular regulations are not so clearcut, however. In the 1970s, the regulations supporting these practices began to be removed. The regulations that continued in effect seem to have lost their potency about that time. The effects of regulation no longer are seen.
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  • 56
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    Review of industrial organization 11 (1996), S. 459-471 
    ISSN: 1573-7160
    Keywords: Regulation ; incentives ; price caps ; competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper examines the properties of a price-cap regulatory regime similar in design to a plan recently proposed by AGT Ltd. in hearings on Alternative Forms of Regulation before the Canadian Radio-television and Telecommunications Commission. The price-cap plan incorporates a number of novel features which include (i) quantity weights that evolve through time rather than remaining fixed; (ii) adjustments for productivity that incorporate yardstick competition; and (iii) allowing the weights to reflect the firm's market power or absence thereof in the presence of competition. Hence, should competitive circumstances permit, the regulatory regime allows for its own sunset.
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  • 57
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    Environmental biology of fishes 46 (1996), S. 309-320 
    ISSN: 1573-5133
    Keywords: Individual growth ; Growth compensation ; Regulation ; Ontogenetic allometry ; Cyprinus carpio ; Leuciscus cephalus ; Rutilus rutilus ; Abramis brama
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Hypotheses which assume a contant proportional deviation of the individual size of fish scales (S) or body (L) from mean size throughout life are biologically insignificant. Growth is considered and illustrated as a complex self-regulating process which continuously changes throughout ontogeny. Speed and form of changes of the growth of individual fish depend mainly on the initial size of the specimen and on the habitat. Consider five main types of changes of the L-S regression lines for individual fish with different initial sizes. They are basically different from the current proportional model of individual growth. The regression lines for individual fish cannot and should not be used for back-calculating L from S either by proportional or by regression methods, as individual L(S)/theoretical L(S) ratio, determined at the time of capture, are usually considerably different, compared to the previous years. For back-calculation of the average L values from average S values the use of separate equations for each age-group or for the whole subpopulation are recommended.
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  • 58
    ISSN: 1432-136X
    Keywords: Key words Gastropod ; Glycolysis ; Heart ; Mollusc ; Perfusion ; Regulation ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The glycolytic flux and the regulation of phosphofructokinase (PFK) activity by fructose 2,6-bisphosphate and covalent modification was investigated in isolated ventricles of land snail Helix lucorum perfused with or without serotonin. Serotonin evoked a significant increase in the level of glycolytic intermediates and a threefold increase of glycolytic flux. Studies of saturation curves of PFK for the substrate fructose 6-phosphate at pH similar to intracellular pH of heart muscle showed that serotonin increases enzyme sensitivity to activation by fructose 6-phosphate. Moreover, PFK preparations from ventricles perfused with serotonin exhibited lower K a values for the activators AMP and fructose 2,6-bisphosphate, compared with the enzyme preparations from serotonin-untreated ventricles. The results suggest that PFK was converted to a more active form when exposed to serotonin. In vitro experiments of PFK phosphorylation showed that the conversion of the enzyme to a more active form was possibly due to its phosphorylation by an endogenous cyclic-AMP-dependent protein kinase. The concentration of fructose 2,6-bisphosphate increased in serotonin-treated ventricles and it exerted a synergistic effect with AMP on the activation of PFK. The bound fraction of glycolytic enzymes increased in the serotonin-treated ventricles only after the 4th min of perfusion. The results suggest that the stimulation of glycolytic flux in the ventricles of H. lucorum in the first minutes of perfusion with serotonin was partly due to the activation of PFK via enzyme molecule covalent modification and to increase of fructose 2,6-bisphosphate.
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  • 59
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    Electrophoresis 18 (1997), S. 675-681 
    ISSN: 0173-0835
    Keywords: Minisatellite ; DNA polymorphism ; Mutation ; DNA-sequencing ; DNA-electrophoresis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: In a study of DNA sequence and length variation in the repeat array of small D7S22 alleles, 100 alleles typed as the common 14 repeat allele (14R) and 92 rare ones were selected for further characterization. A polymerase chain reaction (PCR) based allele length measurement method revealed a discontinuous distribution of alleles. The 92 rare alleles were grouped by their number of repeats. All, except four 6R alleles were distributed within the 11R-19R allele groups. The 14Rs revealed no further length variation while 7 out of the 92 rare alleles showed small length deviations from the other alleles within their respective groups. Nucleotide sequencing of the repeat array was performed in 17 alleles selected from each of the nine allele groups. The micro length variation within allele groups was caused by the presence of either 33, 36 or 37 bp repeats in given positions. A comparison of three 14Rs revealed no further sequence variation between these. Nine out of the fourteen repeats in the 14R differed in sequence and/or size. Based on this difference the repeat array sequence was converted into a code of different variant repeats. The 6R showed a variant repeat code quite unlike that of the 14R, while the encoded allele structure of the other rare alleles suggested that most of them may have evolved from a 14R allele by deletion or duplication of repeat units. Nucleotide sequencing of progenitor and mutant in a D7S22 de novo mutation as well as typing in a polymorphic site near the repeat array suggested that the event was an intra-allelic deletion of exactly three repeats. The present findings indicate that the 14R is ancestral to most rare small alleles, and that mutations in small alleles most often are intra-allelic events leading to a change in bp size equal to an integer number of repeats.
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  • 60
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    Electrophoresis 18 (1997), S. 1418-1428 
    ISSN: 0173-0835
    Keywords: Two-dimentional polyacrylamide gel electrophoresis ; Streptomyces ; Development ; Multivariate ; Regulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Multivariate statistical comparisons of two-dimensional protein (2-D) gel patterns were used for the first time to define stages of a biological developmental system. The differentiating procaryote, Streptomyces coelicolor, was radiolabeled in liquid cultures at 16 intervals during development, and radioactive proteins were separated and quantified on 2-D gels. Cluster, principal component, and correlation analyses classified these gel patterns into four distinct groups, each reflecting a pattern of gene expression specific for a stage of development. These studies focused our attention on a phase of arrested growth as a key regulatory transition leading to secondary metabolism and a phase of renewed growth. Proteins whose synthesis was switched on or off during the “transitional” phase (some 21 and 18, respectively) were identified and will be the focus of future studies designed to identify their physiological or regulatory function.
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  • 61
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    Electrophoresis 18 (1997), S. 533-537 
    ISSN: 0173-0835
    Keywords: Messenger RNA ; Two-dimensional polyacrylamide gel electrophoresis ; Transcript image ; Liver ; Regulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: In order to obtain an estimate of the overall level of correlation between mRNA and protein abundances for a well-characterized pharmaceutically relevant biological system, we have analyzed human liver by quantitative two-dimensional electrophoresis (for protein abundances) and by Transcript Image methodology (for mRNA abundances). Incyte's LifeSeq™ database was searched for expressed sequence tag (EST) sequences corresponding to a series of 23 proteins identified on 2-D maps in the Large Scale Biology (LSB) Molecular Anatomy™ database, resulting in estimated abundances for 19 messages (4 were undetected) among 7926 liver clones sequenced. A correlation coefficient of 0.48 was obtained between the mRNA and protein abundances determined by the two approaches, suggesting that post-transcriptional regulation of gene expression is a frequent phenomenon in higher organisms. A comparison with published data (Kawamoto, S., et al., Gene 1996, 174, 151-158) on the abundances of liver mRNAs for plasma proteins (secreted by the liver) suggests that higher abundance messages are strongly enriched in secreted sequences. Our data confirms this: of the 50 most abundant liver mRNAs, 29 coded for secreted proteins, while none of the 50 most abundant proteins appeared to be secreted products (although four plasma and red blood cell proteins were presents in this group as contaminants from tissue blood).
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  • 62
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; DNA melting ; Kinetics ; Mutation ; Separation efficiency ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Constant denaturant capillary electrophoresis (CDCE) separation takes place in the heated portion of the capillary where faster-moving, unmelted DNA fragments are in equilibrium with slower-moving, partially melted forms. Within a certain temperature range, the position of the melting equilibrium and thus the average electrophoretic mobility of each mutant is different. The resulting difference in mobility allow sequences containing single base pair point mutations to be separated from each other. We report the results of experiments in which we explored the rules defining separation efficiency by varying the parameters of CDCE. We discovered an unusual peak broadening mechanism. In contrast to most other DNA electrophoresis systems, peak width in CDCE steadily decreases with the square root of the separation speed. Moreover, the peak width displays a sharp maximum at a specific temperature. To account for these observations, we use a model which describes CDCE separation as a random walk. According to this model, peaks in CDCE are broad because the kinetics of the melting equilibrium are slow and there-fore the number of random walk steps represented by melting/renaturation transitions is relatively small. In addition to providing a satisfactory interpretation of the data, the model also predicts that separation efficiency will increase as the ionic strength of the running buffer is increased and as the concentration of denaturant in the buffer is decreased. These predictions were verified and were used to establish conditions for high-resolution CDCE suitable for separating complex mixtures of single base pair mutants.
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  • 63
    ISSN: 0173-0835
    Keywords: Conversion ; Minisatellite ; Mutation ; Radiation ; Recombination ; Tandem repeat ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Minisatellites provide not only the basis for DNA fingerprinting and DNA profiling but also extremely informative systems for analysing processes of tandem repeat turnover in the human genome. Minisatellite instability appears to involve distinct mutation processes in somatic and germline cells; in the germline, mutation is frequently dominated by inter-allelic conversion-like events most likely occurring at meiosis and apparently regulated by cis-acting mutation initiator elements. Attempts to define these initiators in transgenic mice have so far been thwarted by what appears to be a major human/mouse barrier to the inter-species transfer of repeat instability. Minisatellites not only show high frequency spontaneous mutation in the germline, but also appear to be very sensitive to mutation induction by ionizing radiation, both in experimentally irradiated mice and in human populations exposed following the Chernobyl disaster; the mechanisms of mutation induction by radiation remain enigmatic.
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  • 64
    Publication Date: 2014-12-03
    Keywords: C91 - Laboratory, Individual Behavior, I18 - Government Policy ; Regulation ; Public Health
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 65
    Publication Date: 2014-01-22
    Description: Using the 2007 National Survey of Children's Health data, we find a statistically and economically significant effect of neighborhood parks and playgrounds on childhood obesity based on covariate matching estimators. The park/playground effect depends on gender, age, race, household income, neighborhood safety, and other neighborhood amenities. The results suggest that adding a neighborhood park/playground may reduce the obesity rate and make children more fit, but relevant interventions must consider socioeconomic status of the targeted children as well as other neighborhood amenities.
    Keywords: I18 - Government Policy ; Regulation ; Public Health, I38 - Government Policy ; Provision and Effects of Welfare Programs, R53 - Public Facility Location Analysis ; Public Investment and Capital Stock
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 66
    Publication Date: 2014-03-21
    Description: The economic theory of regulatory capture predicts that industry groups will attempt to influence their regulators (for example, by lobbying for rules that exclude competition). It has been suggested that the same logic applies to any powerful institution with the ability to affect industry profits. When the aim of industry is to alter the public’s perception of its product (for example, by disseminating favorable messages to the news media or via an advertising campaign, or by funding industry-friendly scientific research), the end result has been dubbed deep capture. We develop a formal model of deep capture, in which consumers have imperfect information about product quality, and a dominant producer is able to increase his profits by altering the parameters of the consumer’s search problem. We demonstrate the empirical relevance of the phenomenon with a discussion of the food industry response to the obesity epidemic.
    Keywords: D18 - Consumer Protection, D83 - Search ; Learning ; Information and Knowledge ; Communication ; Belief, I18 - Government Policy ; Regulation ; Public Health, L15 - Information and Product Quality ; Standardization and Compatibility, L51 - Economics of Regulation
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 67
    Publication Date: 2014-04-05
    Description: A substantial share of U.S. hog producers incorporate antimicrobial drugs into their livestock's feed or water at sub-therapeutic levels to promote feed efficiency and weight gain. Recently, in response to concerns that the overuse of antibiotics in livestock could promote the development of antimicrobial drug-resistant bacteria, the U.S. Food and Drug Administration adopted a strategy to phase out the use of antibiotics for production purposes. This study uses a stochastic frontier model and data from the 2009 USDA Agricultural Resource Management Survey of feeder-to-finish hog producers to estimate the potential effects on hog output and output variability resulting from a ban on antibiotics used for growth promotion. We use propensity score nearest neighbor matching to create a balanced sample of sub-therapeutic antibiotic (STA) users and nonusers. We estimate the frontier model for the pooled sample and separately for users and non-users—which allows for a flexible interaction between STA use and the production technology. Point estimates for the matched sample indicate that STA use has a small positive effect on productivity and production risk, increasing output by 1.0–1.3% and reducing the standard deviation of unexplained output by 1.4%. The results indicate that improvements in productivity resulted exclusively from technological improvement rather than from an increase in technical efficiency.
    Keywords: D24 - Production ; Cost ; Capital and Total Factor Productivity ; Capacity, I18 - Government Policy ; Regulation ; Public Health, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 68
    Publication Date: 2014-07-03
    Description: With the rise of behavioural economics has come the belief that decision-making biases justify paternalistic policies. Such views challenge the notion of consumer sovereignty and the validity of traditional approaches of economic welfare analysis. While behavioural economics might improve the effectiveness of policies that are already justified on some other market-failure grounds, this article argues that the existence of cognitive failures, alone, do not justify government regulation. If one abandons the idea that consumers know what is in their best interest, judging the merits of policies becomes arbitrary and reflects only what a paternalist wants for others. The typical behavioural economic experiment occurs with college students devoid of real-world context. The biases found in such setting may not extrapolate well to conditions where people have more experience and knowledge, and where they can learn from past mistakes. Even when behavioural biases persist in the ‘real world’, consumers face incentives to engage in activities that protect them from the adverse consequences of the biases, and public policies that shield people from such consequences reduce incentives to self-regulate. The article concludes with some ideas for future research and a discussion of the merits of freedom of choice.
    Keywords: D03 - Behavioral Economics ; Underlying Principles, I18 - Government Policy ; Regulation ; Public Health, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 69
    Publication Date: 2014-09-02
    Description: In response to low consumption levels of fruits and vegetables by Supplemental Nutrition Assistance Program (SNAP) participants, the USDA Food and Nutrition Service created the Healthy Incentives Pilot (HIP) to test the efficacy of providing a 30% incentive for purchases of targeted fruits and vegetables (TFVs). Four to six months after implementation, mean daily TFV intake for adult HIP participants was 0.22 cup-equivalents higher (24% higher) than for control-group SNAP participants. These impact estimates with a random-assignment research design generally agree with previously published nonexperimental elasticity estimates, which imply that a pure price reduction of 30% would increase fruit and vegetable consumption by about 20%.
    Keywords: I18 - Government Policy ; Regulation ; Public Health, I38 - Government Policy ; Provision and Effects of Welfare Programs
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 70
    Publication Date: 1997-12-31
    Description: The nuclear factor of activated T cells (NFAT) group of transcription factors is retained in the cytoplasm of quiescent cells. NFAT activation is mediated in part by induced nuclear import. This process requires calcium-dependent dephosphorylation of NFAT caused by the phosphatase calcineurin. The c-Jun amino-terminal kinase (JNK) phosphorylates NFAT4 on two sites. Mutational removal of the JNK phosphorylation sites caused constitutive nuclear localization of NFAT4. In contrast, JNK activation in calcineurin-stimulated cells caused nuclear exclusion of NFAT4. These findings show that the nuclear accumulation of NFAT4 promoted by calcineurin is opposed by the JNK signal transduction pathway.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chow, C W -- Rincon, M -- Cavanagh, J -- Dickens, M -- Davis, R J -- CA58396/CA/NCI NIH HHS/ -- CA65831/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1997 Nov 28;278(5343):1638-41.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Program in Molecular Medicine, Department of Biochemistry and Molecular Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9374467" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Binding Sites ; COS Cells ; Calcineurin/metabolism ; Calcineurin Inhibitors ; Calcium-Calmodulin-Dependent Protein Kinases/*metabolism ; Cell Line ; Cell Nucleus/*metabolism ; Cyclosporine/pharmacology ; Cytoplasm/metabolism ; DNA-Binding Proteins/genetics/*metabolism ; Humans ; JNK Mitogen-Activated Protein Kinases ; Jurkat Cells ; Mitogen-Activated Protein Kinase Kinases ; *Mitogen-Activated Protein Kinases ; Mutation ; NFATC Transcription Factors ; *Nuclear Proteins ; Phosphorylation ; Protein Kinases/metabolism ; Recombinant Fusion Proteins/metabolism ; *Signal Transduction ; T-Lymphocytes/metabolism ; Transcription Factors/genetics/*metabolism ; Transcription, Genetic
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  • 71
    Publication Date: 1997-03-07
    Description: The DED1 gene, which encodes a putative RNA helicase, has been implicated in nuclear pre-messenger RNA splicing in the yeast Saccharomyces cerevisiae. It is shown here by genetic and biochemical analysis that translation, rather than splicing, is severely impaired in two newly isolated ded1 conditional mutants. Preliminary evidence suggests that the protein Ded1p may be required for the initiation step of translation, as is the distinct DEAD-box protein, eukaryotic initiation factor 4A (eIF4A). The DED1 gene could be functionally replaced by a mouse homolog, PL10, which suggests that the function of Ded1p in translation is evolutionarily conserved.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chuang, R Y -- Weaver, P L -- Liu, Z -- Chang, T H -- GM48752/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Mar 7;275(5305):1468-71.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Molecular, Cellular, and Developmental Biology Program, Ohio State University, Columbus, OH 43210, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9045610" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cytoplasm/metabolism ; DEAD-box RNA Helicases ; Eukaryotic Initiation Factor-4A ; Genes, Fungal ; Mice ; Mutation ; Peptide Initiation Factors/genetics/metabolism ; Phenotype ; *Protein Biosynthesis ; RNA Helicases ; RNA Nucleotidyltransferases/genetics/*metabolism ; RNA Splicing ; RNA, Fungal/*genetics ; RNA, Messenger/*genetics ; Recombinant Fusion Proteins/metabolism ; Saccharomyces cerevisiae/enzymology/*genetics ; *Saccharomyces cerevisiae Proteins
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  • 72
    Publication Date: 1997-07-18
    Description: Cell divisions that produce progeny differing in their patterns of gene expression are key to the development of multicellular organisms. In the budding yeast Saccharomyces cerevisiae, mother cells but not daughter cells can switch mating type because they selectively express the HO endonuclease gene. This asymmetry is due to the preferential accumulation of an unstable transcriptional repressor protein, Ash1p, in daughter cell nuclei. Here it is shown that ASH1 messenger RNA (mRNA) preferentially accumulates in daughter cells by a process that is dependent on actin and myosin. A cis-acting element in the 3'-untranslated region of ASH1 mRNA is sufficient to localize a chimeric RNA to daughter cells. These results suggest that localization of mRNA may have been an early property of the eukaryotic lineage.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Long, R M -- Singer, R H -- Meng, X -- Gonzalez, I -- Nasmyth, K -- Jansen, R P -- 7 F32 HD08088-02/HD/NICHD NIH HHS/ -- GM54887/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jul 18;277(5324):383-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9219698" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/genetics/*physiology ; Cell Cycle ; Cell Nucleus/metabolism ; *DNA-Binding Proteins ; Deoxyribonucleases, Type II Site-Specific/genetics ; Fungal Proteins/genetics ; Genes, Fungal ; Genes, Mating Type, Fungal ; In Situ Hybridization, Fluorescence ; Microtubules/physiology ; Mutation ; *Myosin Heavy Chains ; *Myosin Type V ; Myosins/genetics ; RNA, Fungal/genetics/*metabolism ; RNA, Messenger/genetics/*metabolism ; Repressor Proteins/biosynthesis/*genetics ; Saccharomyces cerevisiae/cytology/genetics/metabolism/*physiology ; *Saccharomyces cerevisiae Proteins ; Transcription Factors/biosynthesis/*genetics ; Transformation, Genetic ; Tropomyosin/genetics/physiology ; Zinc Fingers
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  • 73
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-11-14
    Description: Genetic testing for cancer susceptibility is already part of the clinical management of families with some of the well-defined (but uncommon) inherited cancer syndromes. In cases where the risks associated with a predisposing mutation are less certain, or where there is no clearly effective intervention to offer those with a positive result, its use is more controversial. Careful evaluation of costs and benefits, and of the efficacy of interventions in those found to be at risk, is essential and is only just beginning. An immediate challenge is to ensure that both health professionals and the public understand clearly the issues involved.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ponder, B -- New York, N.Y. -- Science. 1997 Nov 7;278(5340):1050-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Box 238, Level 3 Lab Block, Hills Road, Cambridge CB2 2QQ, UK. bajp@mole.bio.cam.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9353178" target="_blank"〉PubMed〈/a〉
    Keywords: Confidentiality ; Cost-Benefit Analysis ; Female ; Genetic Counseling ; Genetic Predisposition to Disease ; Genetic Services ; *Genetic Testing ; Genetic Variation ; Humans ; Insurance, Health ; Insurance, Life ; Male ; Mutation ; Neoplasms/*diagnosis/*genetics ; Resource Allocation ; Risk Assessment ; Risk Factors ; Uncertainty
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  • 74
    Publication Date: 1997-11-14
    Description: The discovery of anticancer drugs is now driven by the numerous molecular alterations identified in tumor cells over the past decade. To exploit these alterations, it is necessary to understand how they define a molecular context that allows increased sensitivity to particular compounds. Traditional genetic approaches together with the new wealth of genomic information for both human and model organisms open up strategies by which drugs can be profiled for their ability to selectively kill cells in a molecular context that matches those found in tumors. Similarly, it may be possible to identify and validate new targets for drugs that would selectively kill tumor cells with a particular molecular context. This article outlines some of the ways that yeast genetics can be used to streamline anticancer drug discovery.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hartwell, L H -- Szankasi, P -- Roberts, C J -- Murray, A W -- Friend, S H -- N01-BC65017/BC/NCI NIH HHS/ -- New York, N.Y. -- Science. 1997 Nov 7;278(5340):1064-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Seattle Project, Molecular Pharmacology Department, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9353181" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Antineoplastic Agents/pharmacology/therapeutic use ; *Drug Design ; *Drug Screening Assays, Antitumor ; Humans ; Mutation ; Neoplasms/*drug therapy/genetics ; Signal Transduction ; Yeasts/genetics
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  • 75
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-06-13
    Description: Exposure of the yeast Saccharomyces cerevisiae to high extracellular osmolarity induces the Sln1p-Ypd1p-Ssk1p two-component osmosensor to activate a mitogen-activated protein (MAP) kinase cascade composed of the Ssk2p and Ssk22p MAP kinase kinase kinases (MAPKKKs), the Pbs2p MAPKK, and the Hog1p MAPK. A second osmosensor, Sho1p, also activated Pbs2p and Hog1p, but did so through the Ste11p MAPKKK. Although Ste11p also participates in the mating pheromone-responsive MAPK cascade, there was no detectable cross talk between these two pathways. The MAPKK Pbs2p bound to the Sho1p osmosensor, the MAPKKK Ste11p, and the MAPK Hog1p. Thus, Pbs2p may serve as a scaffold protein.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Posas, F -- Saito, H -- GM50909/GM/NIGMS NIH HHS/ -- GM53415/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jun 13;276(5319):1702-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9180081" target="_blank"〉PubMed〈/a〉
    Keywords: Calcium-Calmodulin-Dependent Protein Kinases/*metabolism ; Enzyme Activation ; Genes, Fungal ; Genetic Complementation Test ; MAP Kinase Kinase Kinases ; *Mitogen-Activated Protein Kinase Kinases ; *Mitogen-Activated Protein Kinases ; Mutation ; Osmolar Concentration ; Osmotic Pressure ; Peptides/metabolism ; Phosphorylation ; Protein Kinases/*metabolism ; Protein-Serine-Threonine Kinases/*metabolism ; Protein-Tyrosine Kinases/genetics/*metabolism ; Recombinant Fusion Proteins/metabolism ; Saccharomyces cerevisiae/*enzymology/genetics ; *Saccharomyces cerevisiae Proteins ; Signal Transduction
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  • 76
    Publication Date: 1997-05-02
    Description: The neurofibromatosis type 1 (NF1) tumor suppressor protein is thought to restrict cell proliferation by functioning as a Ras-specific guanosine triphosphatase-activating protein. However, Drosophila homozygous for null mutations of an NF1 homolog showed no obvious signs of perturbed Ras1-mediated signaling. Loss of NF1 resulted in a reduction in size of larvae, pupae, and adults. This size defect was not modified by manipulating Ras1 signaling but was restored by expression of activated adenosine 3', 5'-monophosphate-dependent protein kinase (PKA). Thus, NF1 and PKA appear to interact in a pathway that controls the overall growth of Drosophila.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉The, I -- Hannigan, G E -- Cowley, G S -- Reginald, S -- Zhong, Y -- Gusella, J F -- Hariharan, I K -- Bernards, A -- NS22229/NS/NINDS NIH HHS/ -- NS34779/NS/NINDS NIH HHS/ -- NS36084/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1997 May 2;276(5313):791-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Massachusetts General Hospital Cancer Center and Harvard Medical School Building 149, 13th Street, Charlestown, MA 02129, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9115203" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Cell Count ; Cyclic AMP/metabolism ; Cyclic AMP-Dependent Protein Kinases/genetics/*metabolism ; Drosophila/cytology/*genetics/growth & development/metabolism ; *Drosophila Proteins ; GTP Phosphohydrolases/metabolism ; Genes, Insect ; Insect Proteins/chemistry/genetics/*metabolism ; Molecular Sequence Data ; Mutation ; *Nerve Tissue Proteins ; Neurofibromin 1 ; Phenotype ; Proteins/chemistry/genetics ; Recombinant Fusion Proteins/pharmacology ; Signal Transduction ; *ras GTPase-Activating Proteins ; ras Proteins/metabolism
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  • 77
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-03-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thomas, K R -- Capecchi, M R -- New York, N.Y. -- Science. 1997 Mar 7;275(5305):1404-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9072801" target="_blank"〉PubMed〈/a〉
    Keywords: Alleles ; Anemia, Sickle Cell/*genetics ; B-Lymphocytes ; Cells, Cultured ; DNA, Recombinant ; *Gene Conversion ; Hemoglobin, Sickle/*genetics ; Humans ; Mutation ; Oligonucleotides/*genetics
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  • 78
    Publication Date: 1997-02-28
    Description: The small guanosine triphosphatase (GTPase) Rho is implicated in the formation of stress fibers and focal adhesions in fibroblasts stimulated by extracellular signals such as lysophosphatidic acid (LPA). Rho-kinase is activated by Rho and may mediate some biological effects of Rho. Microinjection of the catalytic domain of Rho-kinase into serum-starved Swiss 3T3 cells induced the formation of stress fibers and focal adhesions, whereas microinjection of the inactive catalytic domain, the Rho-binding domain, or the pleckstrin-homology domain inhibited the LPA-induced formation of stress fibers and focal adhesions. Thus, Rho-kinase appears to mediate signals from Rho and to induce the formation of stress fibers and focal adhesions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Amano, M -- Chihara, K -- Kimura, K -- Fukata, Y -- Nakamura, N -- Matsuura, Y -- Kaibuchi, K -- New York, N.Y. -- Science. 1997 Feb 28;275(5304):1308-11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-01, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9036856" target="_blank"〉PubMed〈/a〉
    Keywords: 3T3 Cells ; Actins/*metabolism ; Adenosine Triphosphate/metabolism ; Animals ; Binding Sites ; *Cell Adhesion ; Cell Line ; DNA, Complementary/genetics ; Enzyme Inhibitors/pharmacology ; GTP Phosphohydrolases/metabolism ; Intracellular Signaling Peptides and Proteins ; Lysophospholipids/pharmacology ; Mice ; Mutation ; Protein-Serine-Threonine Kinases/antagonists & inhibitors/genetics/*metabolism ; Recombinant Fusion Proteins/metabolism ; Staurosporine/pharmacology ; rho-Associated Kinases
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  • 79
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-08-22
    Description: Mutations in the SUPERMAN gene affect flower development in Arabidopsis. Seven heritable but unstable sup epi-alleles (the clark kent alleles) are associated with nearly identical patterns of excess cytosine methylation within the SUP gene and a decreased level of SUP RNA. Revertants of these alleles are largely demethylated at the SUP locus and have restored levels of SUP RNA. A transgenic Arabidopsis line carrying an antisense methyltransferase gene, which shows an overall decrease in genomic cytosine methylation, also contains a hypermethylated sup allele. Thus, disruption of methylation systems may yield more complex outcomes than expected and can result in methylation defects at known genes. The clark kent alleles differ from the antisense line because they do not show a general decrease in genomic methylation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jacobsen, S E -- Meyerowitz, E M -- New York, N.Y. -- Science. 1997 Aug 22;277(5329):1100-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Biology 156-29, California Institute of Technology, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9262479" target="_blank"〉PubMed〈/a〉
    Keywords: *Alleles ; Arabidopsis/*genetics/growth & development/metabolism ; *Arabidopsis Proteins ; Base Sequence ; Crosses, Genetic ; Cytosine/metabolism ; DNA (Cytosine-5-)-Methyltransferase/genetics ; *DNA Methylation ; DNA, Antisense ; DNA, Plant/metabolism ; Gene Expression Regulation, Plant ; *Genes, Plant ; Genetic Complementation Test ; Molecular Sequence Data ; Mutation ; Phenotype ; Plants, Genetically Modified ; RNA, Messenger/metabolism ; RNA, Plant/metabolism ; Transcription Factors/*genetics
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  • 80
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-11-14
    Description: Pathogenic Yersinia species have a specialized secretion system (type III) to target cytotoxic Yop proteins during infection. The signals of YopE and YopN sufficient for the secretion of translational reporter fusions were mapped to the first 15 codons. No common amino acid or peptide sequence could be identified among the secretion signals. Systematic mutagenesis of the secretion signal yielded mutants defective in Yop translation; however, no point mutants could be identified that specifically abolished secretion. Frameshift mutations that completely altered the peptide sequences of these signals also failed to prevent secretion. Thus, the signal that leads to the type III secretion of Yop proteins appears to be encoded in their messenger RNA rather than the peptide sequence.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Anderson, D M -- Schneewind, O -- AI 07323/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1997 Nov 7;278(5340):1140-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology, Molecular Biology Institute, University of California, Los Angeles, School of Medicine, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9353199" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Bacterial Outer Membrane Proteins/chemistry/genetics/*secretion ; Bacterial Proteins/chemistry/genetics/*secretion ; Base Sequence ; Codon ; Frameshift Mutation ; *Membrane Proteins ; Molecular Sequence Data ; Mutation ; Nucleic Acid Conformation ; Point Mutation ; Protein Biosynthesis ; RNA, Bacterial/chemistry/*genetics/metabolism ; RNA, Messenger/chemistry/*genetics/metabolism ; Recombinant Fusion Proteins/biosynthesis/secretion ; Yersinia enterocolitica/*metabolism/pathogenicity
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  • 81
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-04-11
    Description: The use of molecular phylogenies to examine evolutionary questions has become commonplace with the automation of DNA sequencing and the availability of efficient computer programs to perform phylogenetic analyses. The application of computer simulation and likelihood ratio tests to evolutionary hypotheses represents a recent methodological development in this field. Likelihood ratio tests have enabled biologists to address many questions in evolutionary biology that have been difficult to resolve in the past, such as whether host-parasite systems are cospeciating and whether models of DNA substitution adequately explain observed sequences.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huelsenbeck, J P -- Rannala, B -- GM40282/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Apr 11;276(5310):227-32.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Integrative Biology, University of California, Berkeley, CA 94720, USA. john@mws4.biol.berkeley.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9092465" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; *Biological Evolution ; Computer Simulation ; *DNA/genetics ; Electron Transport Complex IV/genetics ; *Evolution, Molecular ; Hantavirus/genetics ; Likelihood Functions ; Mutation ; Phthiraptera/genetics ; *Phylogeny ; RNA, Viral/genetics ; Rodentia/genetics
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  • 82
    Publication Date: 1997-06-20
    Description: A leucine-rich nuclear export signal (NES) allows rapid export of proteins from cell nuclei. Microinjection studies revealed a role for the guanosine triphosphatase (GTPase) Ran in NES-mediated export. Nuclear injection of a Ran mutant (Thr24 --〉 Asn) blocked protein export but not import, whereas depletion of the Ran nucleotide exchange factor RCC1 blocked protein import but not export. However, injection of Ran GTPase-activating protein (RanGAP) into RCC1-depleted cell nuclei inhibited export. Coinjection with Ran mutants insensitive to RanGAP prevented this inhibition. Therefore, NES-mediated protein export appears to require a Ran-GTP complex but does not require Ran-dependent GTP hydrolysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Richards, S A -- Carey, K L -- Macara, I G -- EST3207122/ES/NIEHS NIH HHS/ -- GM 50526/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jun 20;276(5320):1842-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology, University of Vermont, Burlington, VT 05405, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9188526" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Transport ; Carrier Proteins/metabolism ; *Cell Cycle Proteins ; Cell Line ; Cell Nucleus/*metabolism ; Cricetinae ; Cytoplasm ; DNA-Binding Proteins/metabolism ; GTP Phosphohydrolases/*metabolism ; GTP-Binding Proteins/metabolism ; *GTPase-Activating Proteins ; Glutathione Transferase/metabolism ; Green Fluorescent Proteins ; *Guanine Nucleotide Exchange Factors ; Guanosine Triphosphate/*metabolism ; Luminescent Proteins/metabolism ; Mutation ; Nuclear Envelope/metabolism ; Nuclear Localization Signals ; Nuclear Proteins/genetics/*metabolism ; Receptors, Glucocorticoid/metabolism ; Recombinant Fusion Proteins/metabolism ; Temperature ; ran GTP-Binding Protein
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  • 83
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-01-17
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Warren, S T -- New York, N.Y. -- Science. 1997 Jan 17;275(5298):408-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9005557" target="_blank"〉PubMed〈/a〉
    Keywords: Alleles ; Amino Acid Sequence ; Base Sequence ; *Crossing Over, Genetic ; Homeodomain Proteins/chemistry/*genetics ; Humans ; Molecular Sequence Data ; Mutation ; Peptides/analysis/*genetics ; Polydactyly/*genetics ; Syndactyly/*genetics ; *Transcription Factors ; Trinucleotide Repeats
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  • 84
    Publication Date: 1997-06-13
    Description: The crystal structures of a germline antibody Fab fragment and its complex with hapten have been solved at 2.1 A resolution. These structures are compared with the corresponding crystal structures of the affinity-matured antibody, 48G7, which has a 30,000 times higher affinity for hapten as a result of nine replacement somatic mutations. Significant changes in the configuration of the combining site occur upon binding of hapten to the germline antibody, whereas hapten binds to the mature antibody by a lock-and-key fit mechanism. The reorganization of the combining site that was nucleated by hapten binding is further optimized by somatic mutations that occur up to 15 from bound hapten. These results suggest that the binding potential of the primary antibody repertoire may be significantly expanded by the ability of germline antibodies to adopt more than one combining-site configuration, with both antigen binding and somatic mutation stabilizing the configuration with optimal hapten complementarity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wedemayer, G J -- Patten, P A -- Wang, L H -- Schultz, P G -- Stevens, R C -- R01 AI39089/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1997 Jun 13;276(5319):1665-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, Berkeley, CA 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9180069" target="_blank"〉PubMed〈/a〉
    Keywords: Antibodies, Catalytic/*chemistry/genetics/immunology ; Antibody Affinity ; Antibody Diversity ; Antigen-Antibody Complex ; Antigen-Antibody Reactions ; Binding Sites ; *Binding Sites, Antibody ; Crystallography, X-Ray ; *Evolution, Molecular ; Haptens/immunology ; Hydrogen Bonding ; Immunoglobulin Fab Fragments/*chemistry/genetics/immunology ; Molecular Sequence Data ; Mutation ; Protein Conformation ; Protein Structure, Secondary
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  • 85
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-05-02
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barinaga, M -- New York, N.Y. -- Science. 1997 May 2;276(5313):682.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9157547" target="_blank"〉PubMed〈/a〉
    Keywords: Alzheimer Disease/diagnosis/enzymology/*genetics ; Brain/*enzymology ; Cells, Cultured ; Electron Transport Complex IV/*genetics/metabolism ; Energy Metabolism ; Humans ; Mitochondria/*genetics ; Mutation
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  • 86
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-05-16
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barinaga, M -- New York, N.Y. -- Science. 1997 May 16;276(5315):1030-1.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9173537" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Biological Clocks/*genetics ; CLOCK Proteins ; Chromosome Mapping ; Circadian Rhythm/*genetics ; Cloning, Molecular ; Gene Expression Regulation ; Mice ; Mutation ; Trans-Activators/chemistry/*genetics/physiology
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  • 87
    Publication Date: 1997-11-21
    Description: In evaluating current combination drug regimens for treatment of human immunodeficiency virus (HIV) disease, it is important to determine the existence of viral reservoirs. After depletion of CD8 cells from the peripheral blood mononuclear cells (PBMCs) of both patients and normal donors, activation of patient CD4 lymphocytes with immobilized antibodies to CD3 and CD28 enabled the isolation of virus from PBMCs of six patients despite the suppression of their plasma HIV RNA to fewer than 50 copies per milliliter for up to 2 years. Partial sequencing of HIV pol revealed no new drug resistance mutations or discernible evolution, providing evidence for viral latency rather than drug failure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wong, J K -- Hezareh, M -- Gunthard, H F -- Havlir, D V -- Ignacio, C C -- Spina, C A -- Richman, D D -- AI 01361/AI/NIAID NIH HHS/ -- AI 27670/AI/NIAID NIH HHS/ -- AI 38858/AI/NIAID NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1997 Nov 14;278(5341):1291-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine, University of California, San Diego, School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9360926" target="_blank"〉PubMed〈/a〉
    Keywords: Anti-HIV Agents/*therapeutic use ; CD4-Positive T-Lymphocytes/immunology/*virology ; Coculture Techniques ; Drug Resistance, Microbial/genetics ; Drug Therapy, Combination ; HIV Infections/*drug therapy/*virology ; HIV-1/genetics/isolation & purification/*physiology ; Humans ; Immunologic Memory ; Indinavir/therapeutic use ; Lamivudine/therapeutic use ; Lymphocyte Activation ; Mutation ; RNA, Viral/analysis/blood ; T-Lymphocyte Subsets/immunology/virology ; Viral Load ; Viremia/*drug therapy/virology ; Virus Activation ; Virus Latency ; Virus Replication ; Zidovudine/therapeutic use
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  • 88
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-02-21
    Description: The Caenorhabditis elegans survival gene ced-9 regulates ced-4 activity and inhibits cell death, but the mechanism by which this occurs is unknown. Through a genetic screen for CED-4-binding proteins, CED-9 was identified as an interacting partner of CED-4. CED-9, but not loss-of-function mutants, associated specifically with CED-4 in yeast or mammalian cells. The CED-9 protein localized primarily to intracellular membranes and the perinuclear region, whereas CED-4 was distributed in the cytosol. Expression of CED-9, but not a mutant lacking the carboxy-terminal hydrophobic domain, targeted CED-4 from the cytosol to intracellular membranes in mammalian cells. Thus, the actions of CED-4 and CED-9 are directly linked, which could provide the basis for the regulation of programmed cell death in C. elegans.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wu, D -- Wallen, H D -- Nunez, G -- CA-64556/CA/NCI NIH HHS/ -- T32A107413-03/PHS HHS/ -- New York, N.Y. -- Science. 1997 Feb 21;275(5303):1126-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology and Comprehensive Cancer Center, The University of Michigan Medical School, Ann Arbor, MI 48109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9027313" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Apoptosis ; Apoptosis Regulatory Proteins ; Caenorhabditis elegans/*cytology/genetics ; *Caenorhabditis elegans Proteins ; Calcium-Binding Proteins/analysis/genetics/*metabolism ; Cell Fractionation ; Cell Line ; Cytosol/chemistry ; Genes, Helminth ; Helminth Proteins/analysis/genetics/*metabolism ; Humans ; Intracellular Membranes/chemistry ; Mutation ; Proto-Oncogene Proteins/analysis/genetics/*metabolism ; *Proto-Oncogene Proteins c-bcl-2 ; Transfection ; bcl-X Protein
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 89
    Publication Date: 1997-01-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keulen, W -- Nijhuis, M -- Schuurman, R -- Berkhout, B -- Boucher, C -- New York, N.Y. -- Science. 1997 Jan 10;275(5297):229; author reply 230-1.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8999550" target="_blank"〉PubMed〈/a〉
    Keywords: Anti-HIV Agents/*pharmacology ; Cells, Cultured ; Drug Resistance, Microbial ; Drug Therapy, Combination ; Genetic Variation ; HIV Infections/drug therapy/virology ; HIV Reverse Transcriptase/*genetics/metabolism ; HIV-1/drug effects/*enzymology/genetics ; Humans ; Lamivudine/*pharmacology/therapeutic use ; Mutation ; Reverse Transcriptase Inhibitors/*pharmacology ; Zidovudine/therapeutic use
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  • 90
    Publication Date: 1997-11-21
    Description: The hypothesis that quiescent CD4+ T lymphocytes carrying proviral DNA provide a reservoir for human immunodeficiency virus-type 1 (HIV-1) in patients on highly active antiretroviral therapy (HAART) was examined. In a study of 22 patients successfully treated with HAART for up to 30 months, replication-competent virus was routinely recovered from resting CD4+ T lymphocytes. The frequency of resting CD4+ T cells harboring latent HIV-1 was low, 0.2 to 16.4 per 10(6) cells, and, in cross-sectional analysis, did not decrease with increasing time on therapy. The recovered viruses generally did not show mutations associated with resistance to the relevant antiretroviral drugs. This reservoir of nonevolving latent virus in resting CD4+ T cells should be considered in deciding whether to terminate treatment in patients who respond to HAART.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Finzi, D -- Hermankova, M -- Pierson, T -- Carruth, L M -- Buck, C -- Chaisson, R E -- Quinn, T C -- Chadwick, K -- Margolick, J -- Brookmeyer, R -- Gallant, J -- Markowitz, M -- Ho, D D -- Richman, D D -- Siliciano, R F -- AI23871/AI/NIAID NIH HHS/ -- AI27670/AI/NIAID NIH HHS/ -- AI28108/AI/NIAID NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1997 Nov 14;278(5341):1295-300.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9360927" target="_blank"〉PubMed〈/a〉
    Keywords: Anti-HIV Agents/pharmacology/*therapeutic use ; CD4-Positive T-Lymphocytes/immunology/*virology ; Cell Separation ; Cross-Sectional Studies ; Drug Resistance, Microbial/genetics ; Drug Therapy, Combination ; HIV Infections/*drug therapy/*virology ; HIV-1/drug effects/genetics/isolation & purification/*physiology ; Humans ; Immunologic Memory ; Lymphocyte Activation ; Mutation ; Proviruses/physiology ; RNA, Viral/blood ; Time Factors ; Viral Load ; Viremia ; Virus Integration ; *Virus Latency ; *Virus Replication
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  • 91
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-08-22
    Description: Signaling cascades triggered by receptor tyrosine kinases (RTKs) participate in diverse developmental processes. The active state of these signaling pathways was monitored by examination of the in situ distribution of the active, dual phosphorylated form of mitogen-activated protein kinase (ERK) with a specific monoclonal antibody. Detection of the active state of the Drosophila epidermal growth factor receptor (DER) pathway allowed the visualization of gradients and boundaries of receptor activation, assessment of the distribution of activating ligands, and analysis of interplay with the inhibitory ligand Argos. This in situ approach can be used to monitor other receptor-triggered pathways in a wide range of organisms.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gabay, L -- Seger, R -- Shilo, B Z -- New York, N.Y. -- Science. 1997 Aug 22;277(5329):1103-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9262480" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies, Monoclonal ; Body Patterning ; Calcium-Calmodulin-Dependent Protein Kinases/immunology/*metabolism ; Cell Differentiation ; Drosophila/cytology/embryology/genetics/*metabolism ; *Drosophila Proteins ; *Epidermal Growth Factor ; Eye Proteins/metabolism ; Gene Expression Regulation, Developmental ; Genes, Insect ; Membrane Proteins/metabolism ; Mutation ; Nerve Tissue Proteins/metabolism ; Phosphorylation ; Photoreceptor Cells, Invertebrate/cytology/embryology ; Receptor, Epidermal Growth Factor/*metabolism ; *Signal Transduction
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  • 92
    Publication Date: 1997-01-17
    Description: Transmembrane receptors for hormones, neurotransmitters, light, and odorants mediate their cellular effects by activating heterotrimeric guanine nucleotide-binding proteins (G proteins). Crystal structures have revealed contact surfaces between G protein subunits, but not the surfaces or molecular mechanism through which Galphabetagamma responds to activation by transmembrane receptors. Such a surface was identified from the results of testing 100 mutant alpha subunits of the retinal G protein transducin for their ability to interact with rhodopsin. Sites at which alanine substitutions impaired this interaction mapped to two distinct Galpha surfaces: a betagamma-binding surface and a putative receptor-interacting surface. On the basis of these results a mechanism for receptor-catalyzed exchange of guanosine diphosphate for guanosine triphosphate is proposed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Onrust, R -- Herzmark, P -- Chi, P -- Garcia, P D -- Lichtarge, O -- Kingsley, C -- Bourne, H R -- CA-54427/CA/NCI NIH HHS/ -- GM-27800/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jan 17;275(5298):381-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143-0450, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8994033" target="_blank"〉PubMed〈/a〉
    Keywords: Aluminum Compounds/pharmacology ; Animals ; Binding Sites ; COS Cells ; Fluorides/pharmacology ; Guanosine 5'-O-(3-Thiotriphosphate)/metabolism ; Guanosine Diphosphate/metabolism ; Models, Molecular ; Mutation ; Phenotype ; *Protein Conformation ; Retinaldehyde/pharmacology ; Rhodopsin/*metabolism/pharmacology ; Rod Cell Outer Segment/metabolism ; Transducin/*chemistry/metabolism
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  • 93
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-01-10
    Description: The long-standing supposition that the biological clock cannot function in cells that divide more rapidly than the circadian cycle was investigated. During exponential growth in which the generation time was 10 hours, the profile of bioluminescence from a reporter strain of the cyanobacterium Synechococcus (species PCC 7942) matched a model based on the assumption that cells proliferate exponentially and the bioluminescence of each cell oscillates in a cosine fashion. Some messenger RNAs showed a circadian rhythm in abundance during continuous exponential growth with a doubling time of 5 to 6 hours. Thus, the cyanobacterial circadian clock functions in cells that divide three or more times during one circadian cycle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kondo, T -- Mori, T -- Lebedeva, N V -- Aoki, S -- Ishiura, M -- Golden, S S -- New York, N.Y. -- Science. 1997 Jan 10;275(5297):224-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-01 Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8985018" target="_blank"〉PubMed〈/a〉
    Keywords: Cell Division ; *Circadian Rhythm ; Cyanobacteria/cytology/genetics/growth & development/*physiology ; Genes, Reporter ; Luciferases/genetics/metabolism ; Luminescence ; Mutation ; Photosynthetic Reaction Center Complex Proteins/genetics ; Photosystem II Protein Complex ; RNA, Bacterial/genetics/metabolism ; RNA, Messenger/genetics/metabolism ; Transformation, Bacterial
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  • 94
    Publication Date: 1997-03-21
    Description: Protein farnesyltransferase (FTase) catalyzes the carboxyl-terminal lipidation of Ras and several other cellular signal transduction proteins. The essential nature of this modification for proper function of these proteins has led to the emergence of FTase as a target for the development of new anticancer therapy. Inhibition of this enzyme suppresses the transformed phenotype in cultured cells and causes tumor regression in animal models. The crystal structure of heterodimeric mammalian FTase was determined at 2.25 angstrom resolution. The structure shows a combination of two unusual domains: a crescent-shaped seven-helical hairpin domain and an alpha-alpha barrel domain. The active site is formed by two clefts that intersect at a bound zinc ion. One cleft contains a nine-residue peptide that may mimic the binding of the Ras substrate; the other cleft is lined with highly conserved aromatic residues appropriate for binding the farnesyl isoprenoid with required specificity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Park, H W -- Boduluri, S R -- Moomaw, J F -- Casey, P J -- Beese, L S -- GM46372/GM/NIGMS NIH HHS/ -- GM52382/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Mar 21;275(5307):1800-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9065406" target="_blank"〉PubMed〈/a〉
    Keywords: *Alkyl and Aryl Transferases ; Binding Sites ; Crystallography, X-Ray ; Dimerization ; Ligands ; Models, Molecular ; Molecular Sequence Data ; Mutation ; *Protein Conformation ; Protein Structure, Secondary ; Proteins/metabolism ; Sequence Alignment ; Transferases/*chemistry/genetics/metabolism ; Zinc/metabolism
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  • 95
    Publication Date: 1997-04-18
    Description: Multiple endocrine neoplasia-type 1 (MEN1) is an autosomal dominant familial cancer syndrome characterized by tumors in parathyroids, enteropancreatic endocrine tissues, and the anterior pituitary. DNA sequencing from a previously identified minimal interval on chromosome 11q13 identified several candidate genes, one of which contained 12 different frameshift, nonsense, missense, and in-frame deletion mutations in 14 probands from 15 families. The MEN1 gene contains 10 exons and encodes a ubiquitously expressed 2.8-kilobase transcript. The predicted 610-amino acid protein product, termed menin, exhibits no apparent similarities to any previously known proteins. The identification of MEN1 will enable improved understanding of the mechanism of endocrine tumorigenesis and should facilitate early diagnosis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chandrasekharappa, S C -- Guru, S C -- Manickam, P -- Olufemi, S E -- Collins, F S -- Emmert-Buck, M R -- Debelenko, L V -- Zhuang, Z -- Lubensky, I A -- Liotta, L A -- Crabtree, J S -- Wang, Y -- Roe, B A -- Weisemann, J -- Boguski, M S -- Agarwal, S K -- Kester, M B -- Kim, Y S -- Heppner, C -- Dong, Q -- Spiegel, A M -- Burns, A L -- Marx, S J -- New York, N.Y. -- Science. 1997 Apr 18;276(5311):404-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Gene Transfer, National Human Genome Research Institute (NHGRI), National Institutes of Health (NIH), Bethesda, MD 20892, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9103196" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Chromosome Mapping ; Chromosomes, Human, Pair 11 ; *Cloning, Molecular ; DNA, Complementary/genetics ; Exons ; Frameshift Mutation ; *Genes, Tumor Suppressor ; Humans ; Molecular Sequence Data ; Multiple Endocrine Neoplasia Type 1/*genetics ; Mutation ; Neoplasm Proteins/chemistry/*genetics ; *Proto-Oncogene Proteins
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  • 96
    Publication Date: 1997-05-02
    Description: The human neurofibromatosis type 1 (NF1) tumor suppressor protein functions as a Ras-specific guanosine triphosphatase-activating protein, but the identity of Ras- mediated pathways modulated by NF1 remains unknown. A study of Drosophila NF1 mutants revealed that NF1 is essential for the cellular response to the neuropeptide PACAP38 (pituitary adenylyl cyclase-activating polypeptide) at the neuromuscular junction. The peptide induced a 100-fold enhancement of potassium currents by activating the Ras-Raf and adenylyl cyclase-adenosine 3',5'-monophosphate (cAMP) pathways. This response was eliminated in NF1 mutants. NF1 appears to regulate the rutabaga-encoded adenylyl cyclase rather than the Ras-Raf pathway. Moreover, the NF1 defect was rescued by the exposure of cells to pharmacological treatment that increased concentrations of cAMP.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Guo, H F -- The, I -- Hannan, F -- Bernards, A -- Zhong, Y -- R01-NS31747/NS/NINDS NIH HHS/ -- R01-NS34779/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1997 May 2;276(5313):795-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9115204" target="_blank"〉PubMed〈/a〉
    Keywords: 8-Bromo Cyclic Adenosine Monophosphate/pharmacology ; Adenylyl Cyclases/*metabolism ; Animals ; Animals, Genetically Modified ; Bucladesine/pharmacology ; Colforsin/pharmacology ; Cyclic AMP/metabolism ; Drosophila/*enzymology/genetics ; *Drosophila Proteins ; Enzyme Activation ; Genes, Insect ; In Vitro Techniques ; Insect Proteins/genetics/*physiology ; Mutation ; *Nerve Tissue Proteins ; Neuromuscular Junction/drug effects/*enzymology ; Neuropeptides/metabolism/*pharmacology ; Patch-Clamp Techniques ; Pituitary Adenylate Cyclase-Activating Polypeptide ; Potassium/metabolism ; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide ; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I ; Receptors, Pituitary Hormone/metabolism ; Signal Transduction ; *ras GTPase-Activating Proteins ; ras Proteins/metabolism
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  • 97
    Publication Date: 1997-07-11
    Description: Platelet-derived growth factor (PDGF)-B-deficient mouse embryos were found to lack microvascular pericytes, which normally form part of the capillary wall, and they developed numerous capillary microaneurysms that ruptured at late gestation. Endothelial cells of the sprouting capillaries in the mutant mice appeared to be unable to attract PDGF-Rbeta-positive pericyte progenitor cells. Pericytes may contribute to the mechanical stability of the capillary wall. Comparisons made between PDGF null mouse phenotypes suggest a general role for PDGFs in the development of myofibroblasts.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lindahl, P -- Johansson, B R -- Leveen, P -- Betsholtz, C -- New York, N.Y. -- Science. 1997 Jul 11;277(5323):242-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medical Biochemistry, University of Goteborg, Medicinaregatan 9A, S-413 90 Goteborg, Sweden.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9211853" target="_blank"〉PubMed〈/a〉
    Keywords: Aneurysm/*etiology ; Animals ; Brain/blood supply ; Capillaries/*cytology/embryology/metabolism ; Cell Movement ; Endothelium, Vascular/cytology/metabolism ; Hemorrhage/etiology ; Mice ; Mice, Inbred C57BL ; Mutation ; Neovascularization, Physiologic ; Platelet-Derived Growth Factor/deficiency/genetics/*physiology ; Proto-Oncogene Proteins/deficiency/genetics/*physiology ; Proto-Oncogene Proteins c-sis ; Receptor Protein-Tyrosine Kinases/metabolism ; Receptor, Platelet-Derived Growth Factor beta ; Receptor, TIE-2 ; Receptors, Platelet-Derived Growth Factor/metabolism ; Signal Transduction ; Stem Cells/cytology/metabolism ; Up-Regulation
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  • 98
    Publication Date: 1997-07-18
    Description: The three-dimensional structure of the complex between human H-Ras bound to guanosine diphosphate and the guanosine triphosphatase (GTPase)-activating domain of the human GTPase-activating protein p120GAP (GAP-334) in the presence of aluminum fluoride was solved at a resolution of 2.5 angstroms. The structure shows the partly hydrophilic and partly hydrophobic nature of the communication between the two molecules, which explains the sensitivity of the interaction toward both salts and lipids. An arginine side chain (arginine-789) of GAP-334 is supplied into the active site of Ras to neutralize developing charges in the transition state. The switch II region of Ras is stabilized by GAP-334, thus allowing glutamine-61 of Ras, mutation of which activates the oncogenic potential, to participate in catalysis. The structural arrangement in the active site is consistent with a mostly associative mechanism of phosphoryl transfer and provides an explanation for the activation of Ras by glycine-12 and glutamine-61 mutations. Glycine-12 in the transition state mimic is within van der Waals distance of both arginine-789 of GAP-334 and glutamine-61 of Ras, and even its mutation to alanine would disturb the arrangements of residues in the transition state.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Scheffzek, K -- Ahmadian, M R -- Kabsch, W -- Wiesmuller, L -- Lautwein, A -- Schmitz, F -- Wittinghofer, A -- New York, N.Y. -- Science. 1997 Jul 18;277(5324):333-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Institut fur molekulare Physiologie, Abteilung Strukturelle Biologie, Rheinlanddamm 201, 44139 Dortmund, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9219684" target="_blank"〉PubMed〈/a〉
    Keywords: Aluminum Compounds/chemistry/metabolism ; Amino Acid Sequence ; Binding Sites ; Catalysis ; Cell Transformation, Neoplastic ; Crystallography, X-Ray ; Enzyme Activation ; Fluorides/chemistry/metabolism ; GTP Phosphohydrolases/chemistry/*metabolism ; GTP-Binding Proteins/chemistry/metabolism ; GTPase-Activating Proteins ; Guanosine Diphosphate/metabolism ; Guanosine Triphosphate/metabolism ; Humans ; Models, Molecular ; Molecular Sequence Data ; Mutation ; *Protein Conformation ; Protein Structure, Secondary ; Proteins/*chemistry/*metabolism ; Signal Transduction ; ras GTPase-Activating Proteins ; ras Proteins/chemistry/genetics/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 99
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-04-25
    Description: A population of RNA molecules that catalyze the template-directed ligation of RNA substrates was made to evolve in a continuous manner in the test tube. A simple serial transfer procedure was used to achieve approximately 300 successive rounds of catalysis and selective amplification in 52 hours. During this time, the population size was maintained against an overall dilution of 3 x 10(298). Both the catalytic rate and amplification rate of the RNAs improved substantially as a consequence of mutations that accumulated during the evolution process. Continuous in vitro evolution makes it possible to maintain laboratory "cultures" of catalytic molecules that can be perpetuated indefinitely.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wright, M C -- Joyce, G F -- New York, N.Y. -- Science. 1997 Apr 25;276(5312):614-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9110984" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Catalysis ; DNA-Directed RNA Polymerases/genetics/metabolism ; *Directed Molecular Evolution ; Evolution, Molecular ; Molecular Sequence Data ; Mutation ; Nucleic Acid Conformation ; Promoter Regions, Genetic ; *RNA, Catalytic/chemistry/genetics/metabolism ; Saccharomyces cerevisiae/chemistry ; Templates, Genetic ; Transcription, Genetic ; Viral Proteins
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 100
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1997-07-25
    Description: Transport of membrane proteins between intracellular compartments requires specific sequences in the protein cytoplasmic domain to direct packaging into vesicle shuttles. A sequence that mediates export from the endoplasmic reticulum (ER) has proved elusive. A di-acidic signal (Asp-X-Glu, where X represents any amino acid) on the cytoplasmic tail of vesicular stomatitis virus glycoprotein (VSV-G) and other cargo molecules was required for efficient recruitment to vesicles mediating export from the ER in baby hamster kidney cells. The existence of such a signal provides evidence that export from the ER occurs through a selective mechanism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nishimura, N -- Balch, W E -- GM 42336/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jul 25;277(5325):556-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9228004" target="_blank"〉PubMed〈/a〉
    Keywords: Acid Phosphatase/metabolism ; Amino Acid Sequence ; Animals ; Biological Transport ; Cell Line ; Cricetinae ; Cytoplasm/chemistry ; Endoplasmic Reticulum/*metabolism ; Golgi Apparatus/metabolism ; *Membrane Glycoproteins ; Membrane Proteins/*chemistry/*metabolism ; Molecular Sequence Data ; Mutation ; Protein Folding ; Protein Sorting Signals/chemistry/*metabolism ; Receptors, Antigen, T-Cell, alpha-beta/metabolism ; Recombinant Fusion Proteins/metabolism ; Viral Envelope Proteins/*chemistry/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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