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  • Yeast  (261)
  • Adaptation
  • Physical Oceanography
  • Springer  (319)
  • Annual Reviews  (2)
  • London : Springer  (1)
  • 2005-2009  (3)
  • 1990-1994  (222)
  • 1980-1984  (97)
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  • 1
    Unknown
    London : Springer
    Keywords: Adaptation ; Artificial Life ; Bio-inspired Computing ; Bio-inspired Robotics ; Collective Behaviour ; Complex Systems ; Decentralized Management ; Distrbuted Management ; Distributed Computing ; Emergence ; Evolutinary Algorithms ; Immune Networks ; Information Transfer ; Multi-agent Systems ; Pattern Formation ; Self-assembly ; Self-organization ; Self-organizing Computation
    Description / Table of Contents: The main challenge faced by designers of self-organizing systems is how to validate and control non-deterministic dynamics. Over-engineering the system may completely suppress self-organization with an outside influence, eliminating emergent patterns and decreasing robustness, adaptability and scalability. Whilst leaving too much non-determinism in the system’s behaviour may make its verification and validation almost impossible. This book presents the state-of-the-practice in successfully engineered self-organizing systems, and examines ways to balance design and self organization in the context of applications. As demonstrated throughout, finding this balance helps to deal with diverse practical challenges. The book begins with the more established fields of traffic management and structural health monitoring, building up towards robotic teams, solving challenging tasks deployed in tough environments. The second half of the book follows with a deeper look into the micro-level, and considers local interactions between agents. These interactions lead towards self-modifying digital circuitry and self-managing grids, self-organizing data visualization and intrusion detection in computer networks, immunocomputing and nature-inspired computation, and eventually to artificial life. The case studies described illustrate the richness of the topic and provide guidance to its intricate areas. Many algorithms proposed and discussed in this volume are biologically inspired and readers will also gain an insight into cellular automata, genetic algorithms, artificial immune systems, snake-like locomotion, ant foraging, birds flocking and mutualistic biological ecosystems, amongst others. Demonstrating the practical relevance and applicability of self-organization, this book will be of interest to advanced students and researchers in a wide range of fields.
    Pages: Online-Ressource (XI, 375 Seiten)
    ISBN: 9781846289828
    Language: English
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  • 2
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    Annual Reviews
    Publication Date: 2022-05-25
    Description: Author Posting. © Annual Reviews, 2006. This article is posted here by permission of Annual Reviews for personal use, not for redistribution. The definitive version was published in Annual Review of Fluid Mechanics 38 (2006): 395-425, doi:10.1146/annurev.fluid.38.050304.092129.
    Description: Over the past four decades, the combination of in situ and remote sensing observations has demonstrated that long nonlinear internal solitary-like waves are ubiquitous features of coastal oceans. The following provides an overview of the properties of steady internal solitary waves and the transient processes of wave generation and evolution, primarily from the point of view of weakly nonlinear theory, of which the Korteweg-de Vries equation is the most frequently used example. However, the oceanographically important processes of wave instability and breaking, generally inaccessible with these models, are also discussed. Furthermore, observations often show strongly nonlinear waves whose properties can only be explained with fully nonlinear models.
    Description: KRH acknowledges support from NSF and ONR and an Independent Study Award from the Woods Hole Oceanographic Institution. WKM acknowledges support from NSF and ONR, which has made his work in this area possible, in close collaboration with former graduate students at Scripps Institution of Oceanography and MIT.
    Keywords: Solitary waves ; Nonlinear waves ; Stratified flow ; Physical Oceanography
    Repository Name: Woods Hole Open Access Server
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  • 3
    Publication Date: 2022-05-25
    Description: First published online as a Review in Advance on October 24, 2005. (Some corrections may occur before final publication online and in print)
    Description: Author Posting. © Annual Reviews, 2005. This article is posted here by permission of Annual Reviews for personal use, not for redistribution. The definitive version was published in Annual Review of Physiology 68 (2006): 22.1-22.29, doi:10.1146/annurev.physiol.68.040104.105418.
    Description: Superfast muscles of vertebrates power sound production. The fastest, the swimbladder muscle of toadfish, generates mechanical power at frequencies in excess of 200 Hz. To operate at these frequencies, the speed of relaxation has had to increase approximately 50-fold. This increase is accomplished by modifications of three kinetic traits: (a) a fast calcium transient due to extremely high concentration of sarcoplasmic reticulum (SR)-Ca2+ pumps and parvalbumin, (b) fast off-rate of Ca2+ from troponin C due to an alteration in troponin, and (c) fast cross-bridge detachment rate constant (g, 50 times faster than that in rabbit fast-twitch muscle) due to an alteration in myosin. Although these three modifications permit swimbladder muscle to generate mechanical work at high frequencies (where locomotor muscles cannot), it comes with a cost: The high g causes a large reduction in attached force-generating cross-bridges, making the swimbladder incapable of powering low-frequency locomotory movements. Hence the locomotory and sound-producing muscles have mutually exclusive designs.
    Description: This work was made possible by support from NIH grants AR38404 and AR46125 as well as the University of Pennsylvania Research Foundation.
    Keywords: Parvalbumin ; Ca2+ release ; Ca2+ uptake ; Cross-bridges ; Adaptation ; Sound production ; Whitman Center
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 229-234 
    ISSN: 1476-5535
    Keywords: Heat shock protein (HSP) ; Yeast ; Saccharomyces ; Viability ; Thermotolerance ; Ethanol tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Heat shock and ethanol stress of brewing yeast strains resulted in the induction of a set of proteins referred to as heat shock proteins (HSPs). At least six strongly induced HSPs were identified in a lager brewing strain and four HSPs in an ale brewing strain. Four of these HSPs with molecular masses of approximately 70, 38, 26 and 23 kDa were also identified in two laboratory strains ofSaccharomyces cerevisiae. The appearance of HSPs correlated with increased survival of strains at elevated temperatures and high concentrations of ethanol. These results suggest that HSPs may play a role in the ethanol and thermotolerance of yeasts. The properties of these proteins and membrane fatty acids in relation to heat and ethanol shock are being investigated.
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  • 5
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    Journal of industrial microbiology and biotechnology 7 (1991), S. 191-195 
    ISSN: 1476-5535
    Keywords: Yeast ; Trehalose ; Osmotolerance ; Viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A total of 12 yeast strains from various genera were examined for their ability to produce ethanol in the presence of high concentrations of glucose. From these studies, the yeastsTorulaspora delbrueckii andZygosaccharomyces rouxii were observed to the most osmotolerant. These osmotolerant yeast strains were also observed to possess high concentrations of intracellular trehalose. Futhermore, these strains were found to be tolerant to long-term storage at −20°C and to storage at 4°C in beer containing 5% (v/v) ethanol. Cells containing high trehalose levels at the time of freezing or cold storage exhibited the highest cell viabilities. Trehalose concentration was observed to increase during growth on glucose, reaching a maximum after 24–48 h. Increasing the incubation temperature from 21 to 40°C also resulted in an increase in intracellular trehalose content. These results suggest that trehalose plays a role in enhancing yeast survival under environmentally stressful conditions.
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  • 6
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    Journal of industrial microbiology and biotechnology 7 (1991), S. 263-268 
    ISSN: 1476-5535
    Keywords: Yeast ; β-Glucanase ; β-Glucosidase catabolite repression ; Sporulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The activities of three glycosidases, β-glucosidase and β(1,3)- and β(1,6)-glucanases have been monitored during growth and blastospore formation inSaccharomycopsis fibuligera. The assays were carried out on the cell-free culture and in a cell-free extract and a wall autolysate preparation from the growing cells. In complex medium containing 1% glucose an increase in the level of all three enzymes was associated with the transition from mycelium to blastospores. When the level of glucose was increased to 5% blastospore formation was repressed and the level of β-glucanases only increased at the end of the fermentation. The β-glucosidase activity increased during the growth phase. In a defined medium in which slow growth in a wholly yeast-like form was observed, growth was not associated with a high level of β-glucanase activity.
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  • 7
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    AI & society 7 (1993), S. 248-252 
    ISSN: 1435-5655
    Keywords: Culture ; Technology ; Cold utilitarianism ; Adaptation ; Civilization ; Western culture ; Eastern culture ; Instrumentality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The role of cultural models in the process of adaptation to the new technologies is very different according to different civilizations. Some basic cultural items seem to be particularly crucial, such as, for example, the levels of pragmatism or rationalism which characterize a civilization or some periods of its history. This paper presents a sketch aimed at setting up a comparison between Western and Eastern cultures facing the problem of adapting to new technologies. The concept ofcold utilitarianism is introduced. It allows a way of defining adaptation which is only partial and contradictory in Western culture, while it completely describes, though perhaps provisionally, the Eastern way of making and using technology.
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  • 8
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    Monatshefte für Chemie 111 (1980), S. 355-363 
    ISSN: 1434-4475
    Keywords: Cerulenin ; Fatty acid donor ; Inositol deficiency ; Phospholipid biosynthesis ; Triacylglycerols ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Der Umsatz der Lipide vonSaccharomyces carlsbergensis ATCC 9080 wurde nach Vormarkierung mit3H-Ölsäure und14C-Palmitinsäure untersucht. Inositversorgte Zellen zeigen eine Verschiebung der Fettsäuren von den Triacylglycerinen in die Phospholipide, im besonderen in Phosphatidylcholin und Phosphatidylinosit. Eine verstärkte Übertragung der Fettsäuren von Triacylglycerinen auf Phospholipide konnte festgestellt werden, wenn vormarkierte Zellen auf ein Nährmedium, welches Cerulenin enthielt, übertragen wurde. Cerulenin inhibiert die Fettsäuresynthese und ruft in wachsenden Zellen Fettsäuremangel hervor. Inositdefiziente Hefezellen, welche einen erhöhten Triacylglycerinspiegel aufweisen, verwenden diese Triacylglycerine unter Fettsäuremangelbedingungen ebenfalls für die Synthese von Phospholipiden, besonders von Phosphatidylcholin, Phosphatidyläthanolamin und Phosphatidylserin. Da aus früheren Arbeiten bekannt ist, daß inSaccharomyces carlsbergensis praktisch keine β-Oxidation existiert, können die Triacylglyerine in diesem Hefestamm als Speicher für Fettsäuren angesehen werden, welche zur Synthese von Phospholipiden dienen.
    Notes: Abstract The turnover of lipids was studied in the yeast,Saccharomyces carlsbergensis ATCC 9080, after prelabeling of the cells with [3H] oleic acid and [14C] palmitic acid. In inositol supplemented cells, a redistribution of fatty acids from triacylglycerols to phospholipids (mainly phosphatidylcholine and phosphatidylinositol) could be demonstrated. An increased transfer of fatty acids from triacylglycerols to phospholipids was observed when prelabeled cells were transferred to a growth medium containing cerulenin, which inhibits fatty acid synthesis and thus induces fatty acid deficiency in the growing cells. Inositol deficient cells contain increased levels of triacylglycerols, which are equally well utilized for phospholipid (mainly phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine) synthesis under conditions of fatty acid deficiency. The present results together with the previous finding that β-oxidation is practically absent inSaccharomyces carlsbergensis suggest that in this yeast triacylglycerols function as storage of fatty acids which can be mobilized for phospholipid biosynthesis.
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  • 9
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    Cellular and molecular life sciences 48 (1992), S. 172-178 
    ISSN: 1420-9071
    Keywords: Yeast ; protein degradation ; ubiquitin conjugating enzymes ; signals for proteolysis ; stress response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Selective degradation of cellular proteins serves to eliminate abnormal proteins and to mediate the turnover of certain short-lived proteins, many of which have regulatory functions. In eukaryotes a major pathway for selective protein degradation is ATP-dependent and is mediated by the ubiquitin system. This pathway involves substrate recognition by components of a ubiquitin-protein ligase system, covalent attachment of ubiquitin moieties to proteolytic substrates, and subsequent degradation of these conjugates by a multicatalytic protease complex. Recent genetic evidence suggests that the remarkable selectivity of this process is largely controlled at the level of substrate recognition by the ubiquitin ligase system. InSaccharomyces cerevisiae, ubiquitin-conjugating enzymes UBC1, UBC4 and UBC5 have been identified as key components of this highly conserved degradation pathway. Genetic analysis indicates that ubiquitin-dependent proteolysis is essential for cell viability and that UBC4 and UBC5 enzymes are essential components of the eukaryotic stress response.
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  • 10
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    Cellular and molecular life sciences 48 (1992), S. 537-543 
    ISSN: 1420-9071
    Keywords: Adaptation ; deep sea ; hydrostatic pressure ; hydrothermal vents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hydothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure, membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.
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  • 11
    ISSN: 1476-5535
    Keywords: Lignocellulosic waste ; Yeast ; Ethanol production ; Optimization study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Hardwood hemicellulose hydrolysate has been utilized as a substrate for ethanol production. Among the three different yeasts tested, the best performances have been obtained, in decreasing order, usingPachysolen tannophilus, Candida shehatae andPichia stipitis. Several pretreatments of this raw material have been studied to improve ethanol yields; in one such pretreatment a strain ofP. tannophilus produced ethanol with a yield of 0.29 gethanol/gsugars (gP/gS); which is only 15% less than the values observed with synthetic media. Neither aeration nor acetone addition improved the fermentation of this substrate; in fact, only a marked stimulation of biomass growth has been observed at the expense of both ethanol and xylitol production.
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  • 12
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    Journal of industrial microbiology and biotechnology 7 (1991), S. 35-39 
    ISSN: 1476-5535
    Keywords: 2-Deoxy-d-glucose ; Yeast ; Catabolite repression ; Derepression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The non-metabolizable and toxic glucose analogue 2-deoxy-d-glucose (2-DOG) has been widely employed to screen for regulatory mutants which lack catabolite repression. A number of yeast mutants resistant to 2-DOG have recently been isolated in this laboratory. One such mutant, derived from aSaccharomyces cerevisiae haploid strain, was demonstrated to be derepressed for maltose, galactose and sucrose uptake. Furthermore, kinetic analysis of glucose transport suggested that the high affinity glucose transport system was also derepressed in the mutant strain. In addition, the mutant had an increased intracellular concentration of trehalose relative to the parental strain. These results indicate that the 2-DOG resistant mutant is defective in general glucose repression.
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  • 13
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    Current genetics 17 (1990), S. 269-273 
    ISSN: 1432-0983
    Keywords: Yeast ; Actin ; Intron ; Antisense RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using Northern blot analysis we have detected an approximately 840 nucleotide-long RNA which is complementary to the 5′ leader sequence and the first ten nucleotides of the coding sequence of the yeast actin (ACT1) messenger RNA. We have determined two transcription start sites for this actin antisense RNA (ASR1), both within the ACT1 intron, at about 80 and 90 nucleotides downstream from the 5′ splice site. Analysis of a cDNA clone showed that this RNA species overlaps the entire trailer sequence and approximately 20 nucleotides of the coding sequence of the nearby yeast YPT1 gene.
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  • 14
    ISSN: 1432-0983
    Keywords: Yeast ; Mutants ; Cytochrome ; Mitochondria ; Oxidative phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper reports studies of bioenergetic modifications in a TTR1 single-nuclear mutant, isolated as resistant to triethyltin, an inhibitor of mitochondrial ATPase, and effective in cAMP-dependent protein phosphorylation. This mutant appears to have lost the wildtype cell ability to respond to a decrease of oxygen concentration in the growth medium by a decrease of cytochrome concentration in the cell. ATP synthesis rate in mutant cells in both the prestationary and stationary phase of growth appeared increased in comparison to wild-type cells, as too was respiration rate. A comparative study of mitochondria extracted from wild-type and from TTR1 mutant cells showed an increase in respiration rate, an increase in ATP synthesis rate, and an increase in TPP+ uptake in mutant mitochondria. The specific ATPase activity, as well as its sensitivity to TET, appears to be similar for mitochondria extracted from both strains. It was proposed that the modification of mitochondrial biogenesis in the TTR1 mutant may be due to a response of the cell to an increase in ATP hydrolysis caused by the mutation. It is also possible that the modification in cAMP-dependent protein kinase regulation which appeared to occur in this mutant affects protein(s) involved in mitochondrial biogenesis.
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  • 15
    ISSN: 1432-0983
    Keywords: Yeast ; Chromosome mapping ; Acidic ribosomal proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary DNA probes from the genes encoding the acidic ribosomal proteins L44, L44′ and L45, as well as from reporter genes for chromosomes IV, VII, XII and XV, have been hybridised to Southern blots of Saccharomyces cerevisiae DNA resolved by pulsed field gel electrophoresis. The protein L44′ and protein L45 genes have been found to hybridise to chromosome IV, identified by the CAT1 gene probe, while the protein L44 probe hybridises with a band containing chromosomes VII and XV, identified by the ATPase 1 and HIS3 genes respectively.
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  • 16
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    Current genetics 19 (1991), S. 329-332 
    ISSN: 1432-0983
    Keywords: Mismatch repair ; Plasmid integration ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A single base pair mismatch (G:T or A:C) in the CYC1 gene of the integrative plasmid pAB218 stimulates up to a five-fold integration into the yeast chromosome. Analysis of chromosomal sites of plasmid integration suggests that the mismatch-stimulated integration is not targeted as would be expected if crossovers, localised in the region of the mismatch, were a necessary step in mismatch repair. Instead, the observed mismatch-stimulated plasmid integration could be due to potentially recombinogenic structures formed during mismatch repair, such as single-stranded gaps or denatured DNA regions extending around the plasmid molecule.
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  • 17
    ISSN: 1432-0983
    Keywords: PET genes ; Yeast ; Mitochondria ; ATP synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study details the characteristics of two temperature-conditional pet mutants of yeast, strains ts1860 and ts379, which at the non-permissive temperature show deficiencies in the formation of three mitochondrially encoded subunits of the ATP synthase complex. By analysis of mitochondrial translation products, and of mitochondrial transcription in temperature shift experiments from the permissive (22°C) to the non-permissive (36°C) temperature, it was concluded that the nuclear mutations in both mutants primarily inhibit synthesis of ATP synthase subunit 9, and that reductions in subunit 8 and 6 synthesis are secondary pleiotropic effects. Following transfer to 36°C, cells of mutant ts379 display a near complete inhibition of subunit 9 synthesis within 1 h, coincident with a marked reduction in the level of the cognate oli1 mRNA. On the other hand, near complete inhibition of subunit 9 synthesis in strain ts1860 occurs after 3 h at 36°C, at which time there is little change in the level of subunit 9 mRNA. In both mutants the mRNA levels for subunits 6 and 8 are not significantly affected at the time of inhibition of subunit 9 synthesis. Provision of an alternative source of subunit 8, translated extra-mitochondrially for import into the organelle, does not overcome the mutant phenotype of either mutant at 36°C, confirming that subunit 8 is not the sole or primary deficiency in each mutant. The mutants indicate that the products of a least two nuclear genes (designated AEP1 and AEP2) are required for the expression of the mitochondrial oli1 gene and the synthesis of subunit 9. The product of the AEP1 gene (defective in mutant ts1860) is required for translation of oli1 mRNA while the AEP2 product (defective in mutant ts379) is essential either for the stability of oli1 mRNA or for the correct processing of precursor transcripts to the mature message.
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  • 18
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    Current genetics 19 (1991), S. 389-393 
    ISSN: 1432-0983
    Keywords: Yeast ; Pichia inositovora ; Linear plasmids ; Killer toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pichia inositovora, strain NRRL Y-18709, which contains three linear double-stranded DNA plasmids, pPinl-1, pPinl-2 and pPinl-3, was cured of these plasmids both by growing the strain in the presence of 50 μg/ml bisbenzimide, and by exposure to ultraviolet light. Both cured and uncured strains were tested for growth on a variety of carbon sources. No differences in growth response were detected, indicating no discernible involvement of the linear plasmids in the catabolism of these compounds. Culture supernatants of Pichia inositovora were shown to contain a substance larger than 100 kDa that is toxic to Saccharomyces cerevisiae, strain GS 1688. Toxin activity was optimal in YEPD assay plates containing 50 mM citrate buffer with a pH between 3.4 and 4.2. Culture supernatants from P. inositovora were also weakly active against Cephaloascus albidus, strain NRRL Y-18710, and Citeromyces matritensis, strain NRRL Y-18711. Concentrated supernatants from cured P. inositovora strains did not exhibit these activities, consistent with the hypothesis that this toxic activity is linear plasmid-encoded. Unlike the wellknown Kluyveromyces lactis system or the newly identified P. acaciae system, P. inositovora strains cured of their linear plasmids do not become detectably sensitive to toxin produced by the wild-type strain, suggesting a nonplasmid-encoded immunity function.
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  • 19
    ISSN: 1432-0983
    Keywords: Yeast ; Molecular cloning ; Nitrogen mustard hyper-resistance ; Choline transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The recessive hnm1 mutant allele is responsible for hyper-resistance to nitrogen mustard in Saccharomyces cerevisiae. Transformation with a single-copy HNM1 wild-type allele of such hyper-resistant mutants will restore wild-type sensitivity to nitrogen mustard. By contrast the presence of multi-copy vectors containing HNM1, in either a hyper-resistant hnm1 mutant or an HNM1 wild-type, will lead to a novel, mustard-sensitive phenotype unrelated to defects in DNA repair genes. Gene disruption of HNM1 revealed that this gene is nonessential for cells prototrophic for choline (CHO1) but lethal for cells with a cho1 genotype. Sensitivity to nitrogen mustard of wild-type HNM1, but not of hnm1 mutants, depends on the choline content of the growth medium, with cells grown in choline-free medium exhibiting the highest sensitivity. Sequencing of a 300 bp DNA fragment of HNM1 revealed the identity of this gene with the CTR locus, which is responsible for choline transport in Saccharomyces cerevisiae.
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  • 20
    ISSN: 1432-0983
    Keywords: Mutagen hyper-resistance ; Yeast ; Base sequence ; Gene disruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A multi-copy plasmid containing the SNQ3 gene confers hyper-resistance to 4-nitroquinoline-N-oxide (4NQO), Trenimon, MNNG, cycloheximide, and to sulfometuron methyl in yeast transformants. Restriction analysis, subcloning, and DNA sequencing revealed an open reading frame of 1950 bp on the SNQ3-containing insert DNA. Gene disruption and transplacement into chromosomal DNA yielded 4NQO-sensitive null mutants which were also more sensitive than the wild-type to Trenimon, cycloheximide, sulfometuron methyl, and MNNG. Hydropathic analysis showed that the SNQ3-encoded protein is most likely not membrane-bound, while the codon bias index points to low expression of the gene.
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  • 21
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Intragenic recombination ; Mutant polypeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Recombinational analysis of oxil mutants was performed using a and a mutant strains with the same mitochondrial and nuclear backgrounds, derived from strain 777-3A. In spite of minor inconsistencies the overall map of oxi1 mutations can be constructed on the basis of wild-type recombinant frequencies in the two-point oxi1 − − x oxi1 − crosses. The frequencies of wild-type recombinants varied in a wide range from 0.003% to 16%, reaching the maximal values expected for unlinked mitochondria) markers. No distinct clusters of mutants were observed. The analysis of translation products of oxil mutants showed that all but one of the oxil mutants studied are connected with the conspicuous changes of the polypeptide band corresponding to subunit 11 of cytochrome c oxidase in electrophoresis on polyacrylamide gels. The exceptional G565 mutant showed no conspicuous change in subunit II, but lacked subunit I of cytochrome c oxidase. Various oxi1 mutants seemed to carry premature chain termination mutations. Most of them show a correlation between the length of the putative fragment of subunit II synthesized and the position on the genetic map. The direction of translation is from the V2 to the V60 mutation. The V2 mutation is proximal to cap and V60 proximal to the par locus.
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  • 22
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    Current genetics 2 (1980), S. 61-67 
    ISSN: 1432-0983
    Keywords: Axenomycin ; Ribosome genetics ; Yeast ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Axenomycin inhibits protein synthesis in vivo and in vitro in Saccharomyces cerevisiae. The antibiotic acts by binding to ribosomes, most probably to the large ribosomal subunit. Mutant strains resistant to axenomycin appear to contain ribosomes that are not inhibited by the antibiotic. The responsible gene has been mapped on the VII chromosome between the centromere and the leu1 gene.
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  • 23
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    Current genetics 19 (1991), S. 89-94 
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Intron ; Mobile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial and nuclear genomes of 21 yeast species belonging to 12 genera have been tested for the presence of sequences similar to seven S. cerevisiae mitochondrial introns (Sc cox1.1,2,3,4,5c, Sc cob.4 and Sc LSU.1) and one K. lactis mitochondrial intron (Kl cox1.2). Some introns, (Sc cox1.4, Sc cob.4, Sc LSU.1 and Kl cox1.2-all group I type), are widely distributed and are found in species with either basidiomycete or ascomycete affinities. This distribution is suggestive of recent sequence transfer between species. The remaining S. cerevisiae introns cross react with an additional species but with no set pattern. Pulsed field gel electrophoretic studies confirm that none of the tested mitochondrial introns cross react with nuclear DNA. These introns are, therefore, mitochondria-specific. Seven strains of K. lactis exhibit striking variability in intron content. In contrast to all mitochondrial introns tested, two introns of nuclear genes (the K. lactis actin gene and the S. cerevisiae RP29B gene) are not detected beyond their source species.
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  • 24
    ISSN: 1432-0983
    Keywords: Yeast ; Pyruvate decarboxylase ; Gene expression ; Codon usage ; Gene fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three structural genes encode the pyruvate decarboxylase isoenzymes in the yeast Saccharomyces cerevisiae. PDC1 and PDC5 are active during glucose fermentation where PDC1 is expressed about six times more strongly than PDC5. Expression of PDC6 is weak and seems to be induced in ethanol medium. Consequently, pdc1Δ pdc5Δ double mutants do not ferment glucose and do not grow on glucose medium. Spontaneous mutants, derived from such a pdc1 pdc5 strain, were isolated which could again ferment glucose. They showed pyruvate decarboxylase activity due to a duplication of PDC6. The second copy of PDC6 was expressed under the control of the PDC1 promoter, which was still present in the pdc1 strain. However, the resulting PDC1-PDC6 fusion gene could only partially substitute for PDC1: to achieve normal growth and high pyruvate decarboxylase activity strains carrying PDC1-PDC6 required a functional PDC5 gene which is dispensable in a PDC1 wild-type background. Thus, expression of PDC5 depends on the state of the PDC1 locus: low in the PDC1 wild-type background and high in PDC1-PDC6 fusion strains and, as shown previously, in pdc1 mutants. The activation of PDC5 expression in PDC1-PDC6 strains may be due to particular properties of the PDC1-PDC6 fusion protein or simply to the weaker expression of PDC1-PDC6 in comparison to the wild-type PDC1 gene.
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  • 25
    ISSN: 1432-0983
    Keywords: Ubiquitin ; Regulation ; Adaptation ; Transcripts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It has previously been shown that the yeast ubiquitin genes UBI1, 2 and 3 are strongly expressed during the log-phase of batch culture growth, whereas the UBI4 gene is weakly expressed. We found that heat shock, treatment with DNA-damaging agents, starvation, and the feeding of starved cells all transiently induced UBI4. These results suggest that UBI4 is induced whenever a change in culture conditions dictates a dramatic shift in cellular metabolism, and that UBI4 expression returns to lower levels once cellular metabolism has adapted to the new conditions. In contrast, all of the treatments tested, except starvation, transiently repressed the UBI1, 2 and 3 genes. Although starvation also repressed UBI1, 2 and 3 its effect was not transient, and expression only recovered upon the addition of fresh media. These results, together with others presented here, suggest that high levels of UBI1, 2 and 3 expression are dependant upon ongoing cell growth, and that treatments which slow or stop growth repress their expression.
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  • 26
    ISSN: 1432-0983
    Keywords: AEP2 ; Yeast ; Mitochondria ; ATP synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The temperature-conditional pet mutant, ts379, of Saccharomyces cerevisiae fails to synthesize mitochondrial ATP synthase subunit 9 at the restrictive temperature due to mutation of a single nuclear locus, AEP2. The inability to synthesize subunit 9 correlates with a lowered accumulation of the cognate oli1 mRNA indicating that the AEP2 product is involved in oli1 transcript maturation or stabilization. The AEP2 gene has been isolated in this study from a wild-type yeast genomic library by genetic complementation of ts379 at the restrictive temperature. A 1740 nucleotide open-reading frame was observed that encodes a basic, hydrophilic protein of 67534 Da which possesses a putative mitochondrial address signal. Disruption of chromosomal DNA within this reading frame produced a non-conditional respiratory mutant unable to synthesize subunit 9, identifying the AEP2 gene. Hybridization analyses indicate that AEP2 is located on chromosome XIII and produces a 2.1 kb poly(A)+ transcript. Two additional open-reading frames were found in close proximity to that of AEP2. The three open-reading frames shared no significant homology with entries in several data bases.
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  • 27
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein gene ; Sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two genes encoding ribosomal protein YL41 were cloned from Saccharomyces cerevisiae chromosomal DNA. Both genes contain an uniterrupted region of only 75 nucleotides coding for a protein of 3.3 kD. Within the coding regions the nucleotide sequences are virtually identical, whereas in both the 5′-and 3′-flanking regions the two genes differ significantly from each other. The deduced protein shows an arginine and lysine content of 68 percent, i.e., 17 out of 25 residues, and the basic residues are evenly distributed over the molecule. When compared to the ribosomal protein sequences currently available no counterpart to YL41 could be found in prokaryotes and it seems likely that YL41 is a eukaryotespecific ribosomal protein.
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  • 28
    ISSN: 1432-0983
    Keywords: Yeast ; Trans-acting Factor ; RAP1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We show by deletion mutagenesis, followed by in vivo and in vitro analysis, that the binding of a protein factor to the upstream activation sequence (USA) of the Saccharomyces cerevisiae glycolytic gene PYK, encoding pyruvate kinase, is required for efficient transcription of the corresponding coding region. In addition, gel electrophoretic mobility shift and DNase I protection studies, involving yeast gene products expressed in E. coli, suggest that this trans-acting DNA-binding protein is encoding by the RAP1 gene. The identification of RAP1 binding sites located within the UAS element of the yeast PYK, PGK (phosphoglycerate kinase) and ENO1 (enolase) genes, and in the 5′-upstream region of the ADHI (alcohol dehydrogenase) gene, suggests that a mechanism of coordinate gene expression involving several of the glycolytic genes may exist in yeast.
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  • 29
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    Current genetics 18 (1990), S. 485-491 
    ISSN: 1432-0983
    Keywords: Yeast ; Ty elements ; Virus like particles
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    Topics: Biology
    Notes: Summary Electron microscopic analysis of thin sections of Saccharomyces cerevisiae NCYC74 has revealed the presence of many clumped cytoplasmic particles that morphologically resemble Ty element virus-like particles (VLPs). Accumulation of Ty VLPs has only previously been observed in S. cerevisiae strains that over-express a cloned Ty element. The particles in NCYC74 co-purify with Ty RNA, Ty-specific antigens and a reverse transcriptase activity. Furthermore, they appear to be recognised by antibodies to Ty VLPs during indirect immunofluorescence experiments. These observations provide compelling evidence that the cytoplasmic particle in NCYC74 are indeed Ty VLPs.
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  • 30
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    Current genetics 18 (1990), S. 29-39 
    ISSN: 1432-0983
    Keywords: Recombination ; DNA repair ; UV irradiation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A novel synthetic locus is described that provides a simple assay system for characterizing mitotic recombinants. The locus consists of the TRP1 and HIS3 genes inserted into chromosome III of S. cerevisiae between the CRY1 and MAT loci. Defined trp1 and his3 alleles have been generated that allow the selection of interchromosomal recombinants in this interval. Trp+ or His+ recombinants can be divided into several classes based on coupling of the other alleles in the interval. The tight linkage of the CRY1 and MAT loci, combined with the drug resistance and cell type phenotypes that they respectively control, facilitates the classification of the recombinants without resorting to tetrad dissection. We present the distribution of spontaneous recombinants among the classes defined by this analysis. The data suggest that the recombination intermediate can have regions of symmetric strand exchange and that co-conversion tracts can extend over 1–3 kb. Continuous conversion tracts are favored over discontinuous tracts. The distribution among the classes defined by this analysis is altered in recombinants induced by UV irradiation.
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  • 31
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondrial RNA splicing ; Nuclear pet - mutant ; Group I introns
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    Topics: Biology
    Notes: Summary We have studied the role of the product of the nuclear gene PET157 in mitochondrial pre-mRNA splicing. Cytoduction experiments show that a mitochondrial genome deleted for the three introns bI3, aI5 and aI6 is able to suppress the pet157-1 mutation: the strain recovers respiratory competency indicating that the product of the PET157 gene is only required for mitochondrial premRNA splicing. Characterization of the high molecular weight pre-mRNAs which accumulate in the pet157 mutant demonstrate that the product of the PET157 gene is required for the excision of two group I introns bI3 and aI6 (corresponding to aI5β) located in the cob-box and coxI genes respectively. Furthermore, the pet157 mutant strain accumulates the bI3 maturase in the form of a polypeptide of 50K (p50) previously observed in mitochondrial mutants defective in the excision of bI3. We have shown by restriction analysis and allelism tests that the pet157-1 mutation is allelic to the nuclear mrs1 mutation, previously described as specifically blocking the excision of bI3. Finally, revertants obtained by the deletion of bI3 or aI6 from the mitochondrial DNA were isolated from the MRS1 disrupted allele, confirming the involvment of the product of the MRS1/PET157 gene in the excision of the two introns bI3 and aI6.
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  • 32
    ISSN: 1432-0983
    Keywords: S. cerevisiae ; Yeast ; Cadmium resistance ; CAD2 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A cadmium-resistant strain, X3382-3A, which is able to grow in a medium containing 0.2 mM cadmium sulfate, was picked out from our laboratory stock strains of Saccharomyces cerevisiae. The cadmium resistance of this strain is controlled by a single dominant nuclear gene, denoted as CAD2. The locus of CAD2 was mapped by gene linkage to a site 15.5 centimorgans to the right of the his7 locus on the right arm of chromosome II. The cadmium resistance of the strain carrying CAD2 was evaluated for its properties of cadmium uptake, cadmium distribution and cadmium-metallothionein formation, in comparison with those of some other strains. The results suggest that the novel type of cadmium resistance controlled by CAD2 does not involve production of a cadmiumm-metallothionein.
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  • 33
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    Current genetics 2 (1980), S. 207-210 
    ISSN: 1432-0983
    Keywords: Yeast ; Plasmid ; Repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have developed a system for assaying pyrimidine dimers in the 2 ⇐m DNA plasmid of Saccharomyces cerevisiae, using Micrococcus luteus UV endonuclease to nick dimer-containing plasmid molecules and measuring percentages of nicked and covalently closed circles on agarose gels. UV-irradiation induced dimers in plasmid DNA, in vivo, at the same rate as in chromosomal DNA. After a dose of 20 Joules·m−2, approximately 86% of plasmid molecules had. at least one dimer. After 3 h incubation under normal growth conditions only 4% still retained dimers in a wild-type strain. In a rad1 (excision-defective) mutant 81% of plasmid molecules still had dimers after 3 h, suggesting that excision repair operates to remove dimers from plasmid DNA in wild-type yeast. Dimers can be removed from 2 ,um DNA in a rad1 mutant by photoreactivation.
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  • 34
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    Current genetics 2 (1980), S. 211-214 
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein dimorphism
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    Topics: Biology
    Notes: Summary Two-dimensional gel electrophoresis was used in a comparative study of ribosomal proteins from various strains of Saccharomyces cerevisiae. The results demonstrated a case of dimorphism of L8 protein of 60S ribosomal subunit. Of eight strains examined, two strains were one type and six were the other type. The former, which was tentatively designated as altered (A) type, was more acidic than the latter, common (C) type, as shown by mobility difference in pH gradient gel. Heterozygous (A/C) diploid cells contained both types of L8 protein and gave rise to tetrads of 2:2 segregation for A and C types, indicating that the difference of mobility was reflection of the allelic difference of the gene coding for L8 protein.
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  • 35
    ISSN: 1432-0983
    Keywords: Pulsed field gel-electrophoresis ; S1 nuclease sensitive sites ; Repair ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Repair under non-growth conditions of DNA double-strand breaks (DSB) and chromatin sites sensitive to S1 endonuclease (SSS) induced by 60Cobalt-gamma rays were monitored in repair-competent and deficient strains of Saccharomyces cerevisiae by pulsed field gelelectrophoresis. In stationary-phase cells of a repair-competent RAD diploid, and an excision-deficient rad3-2 diploid, SSS are repaired as efficiently as DSB, whereas in a repair-competent RAD haploid, and a rad 50-1 diploid, neither SSS nor DSB are repaired. The rad18-2 diploid repairs DSB well but is defective in SSS repair. Obviously, SSS repair in yeast chromatin, like DSB repair, depends on recombination, but unlike DSB repair depends additionally on RAD18 function.
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  • 36
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    Current genetics 1 (1980), S. 177-183 
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein alteration ; Cycloheximide
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    Topics: Biology
    Notes: Summary A spontaneous high-level cycloheximide-resistant mutant of the yeast Saccharomyces cerevisiae (strain cy32) is found to have an altered protein of the large subunit (60S) of cytoplasmic ribosomes, namely protein L29. The resistance character segregates together with this biochemical defect and is semidominant in heterozygous diploids. Judged from in vitro susceptibility to inhibition by cycloheximide there are at least 50% resistant ribosomes present in such diploid strains. From these results it is concluded that cycloheximide resistance of mutant cy32 is caused by mutation of a single gene and that it is the structural gene for L29 which is affected. Preliminary genetic mapping data are also reported. They indicate a location of cyhx-32 marker on chromosome 7 near met13.
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  • 37
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    Current genetics 17 (1990), S. 179-183 
    ISSN: 1432-0983
    Keywords: Heme ; Cytochromes ; Regulation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Simultaneous effects of mutations in the transcriptional regulatory genes, HAP1, HAP2 and HAP3, on all respiratory cytochromes of Saccharomyces cerevisiae were determined. Cytochrome behavior in hap mutants and in cyc4 and rhm1 mutants, altered in regulation of 5-aminolevulinate synthase, was compared. Although hap mutants were isolated as trans-acting, transcriptional regulators of the CYC1 (iso-1-cytochrome c) gene, each mutant exhibits partial deficiencies in all cytochrome types. In hap2 and hap3 strains all cytochromes were decreased proportionally to about 40–50% of wild type values. In contrast, hap1 caused a decrease in all cytochromes and an accumulation of a pigment, probably Zn porphyrin. Apparently apocytochrome and heme biosynthesis retain coordination in hap2 and hap3, but not in hap1, mutants. Unlike cyc4 and rhm1 mutants, hap mutants do not exhibit 5-aminolevulinate-dependent restoration of cytochromes. The hap1 mutant grew at nearnormal rates on glycerol, whereas hap2 and hap3 mutants grew very slowly. The frequency of [rho-] was high (16–18%) in hap2 and hap3 strains. Results are consistent with generalized control of mitochondrial replication directed by the HAP1-HAP2 system and heme-directed control of formation of all apocytochromes mediated by HAP1. Neither system exerts all-or-nothing control.
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  • 38
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    Current genetics 17 (1990), S. 275-280 
    ISSN: 1432-0983
    Keywords: Yeast ; DNA replication ; Effect on mutation
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    Topics: Biology
    Notes: Summary Incubation in YPD medium under permissive conditions when DNA replication is going on, strongly stimulates the induction of cdc+ colonies of UV-irradiated cells of yeast strains HB23 (cdc8-1/cdc8-3), HB26 (cdc8-3/cdc8-3) and HB7 (cdc8-1/cdc8-1). Inhibition of DNA replication by hydroxyurea, araCMP, cycloheximide or caffeine or else by incubation in phosphate buffer pH 7.0, abolishes this stimulation. Thus the replication of DNA is strongly correlated with the high induction of cdc+ colonies by UV irradiation. It is postulated that these UV-induced cdc+ colonies arise as the result infidelity in DNA replication.
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  • 39
    ISSN: 1432-0983
    Keywords: Yarrowia lipolytica ; 7SL RNA ; Essential genes ; Yeast
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    Topics: Biology
    Notes: Summary Cells containing a deletion of either the SCR1 or SCR2 genes, which code for the 7SL RNA component of the signal recognition particle (SRP) homologue, were found to be viable. Two independent approaches demonstrated that cells containing deletions of both genes were inviale. Therefore, Yarrowia lipolytica contains two (and only two) functional 7SL RNA genes.
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  • 40
    ISSN: 1432-0983
    Keywords: Mitotic recombination ; Hyper-recombination ; RAD50 ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutations in the RAD50 gene of Saccharomyces cerevisiae have been shown to reduce double strand break repair, meiotic recombination, and radiation-inducible mitotic recombination. Several different point mutations (including ochre and amber alleles) have been previously examined for effects on spontaneous mitotic recombination and did not reduce the frequency of recombination. Instead, the rad50 mutations conferred a moderate hyper-rec phenotype. This paper examines a deletion/interruption allele of RAD50 that removes 998 of 1312 amino acids and adds 1.1 kb of foreign DNA. The results clearly indicate that spontaneous mitotic recombination can occur in the absence of RAD50; in fact, the frequency of recombination is elevated over the wild-type cell. One possible interpretation of these observations is that the initiating lesion in spontaneous recombination events in mitosis might not be a double strand break.
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  • 41
    ISSN: 1432-0983
    Keywords: Flow cytometry ; Rhodamine 123 ; Respiratory chain ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cationic lipophilic dye Rhodamine 123 (Rh123) is selectively enriched in mitochondria in a membrane potential-dependent manner. Application of drugs which interfere with the electron flow of the respiratory chain lead to a severe reduction of mitochondrial dye uptake. In this communication we show that the same effect is observed after Rh123-staining of respiratory-deficient yeast mutants. Based on this observation we used flow cytometry to discriminate respiratory-compentent and respiratory-deficient yeast cells. Combined with a cell sorter we were able to selectively enrich respiring and non-respiring yeast cells, repectively, from a mixture of cells.
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  • 42
    ISSN: 1432-0983
    Keywords: Yeast ; Mistranslation ; ψ-factor
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    Topics: Biology
    Notes: Summary Chromosomal omnipotent suppressor mutations recovered in ψ+ strains of Saccharomyces cerevisiae were brought into ψ− cytoplasm. SUP46, SUP138 and SUP139 acted as dominant omnipotent suppressors in the ψ− cytoplasm though their suppressor activity was substantially reduced. SUP46 and SUP138 conferred recessive thermosensitivity and antibiotic sensitivity in ψ− cytoplasm as in ψ+ cytoplasm. On the other hand, sup111 through sup115, which acted as recessive omnipotent suppressors in the ψ+ cytoplasm, manifested no, or very low, suppressor activity in the ψ− cytoplasm. They, however, still enhanced the efficiency of the SUP29 tRNA suppressor in ψ− cytoplasm. A multicopy plasmid carrying the wild-type SUP35 gene enhanced the efficiency of sup111 in ψ− cytoplasm.
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  • 43
    ISSN: 1432-0983
    Keywords: Yeast ; QH2: cytochrome c oxidoreductase ; Mitochondrial biogenesis ; Transcription
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    Notes: Summary In Saccharmmyces cerevisiae, the COR2 gene codes for the 40 kDa subunit II of the QH2: cytochrome c oxidoreductase, an enzyme of the mitochondrial respiratory chain. Regions in the 5′ flank of this gene important for regulated expression were identified by assaying β-galactosidase activities in cells carrying different COR2-lacZ fusion genes. Sequences downstream of position-201 relative to the translational initiation codon are sufficient to confer regulation by carbon source, whereas sequences downstream of position-153 do not give rise to significant expression. A binding site for the abundant general transcription factor GFI is present in the region between-201 and-153 just upstream from sequences which resemble the consensus DNA recognition sequence of the regulatory protein complex HAP2/HAP3: 5′-TNATTGGT-3′. By quantitating RNA levels and assaying β-galactosidase activities we show that synthesis of COR2, which is not a hemoprotein, is regulated by HAP1, HAP2/HAP3 and heme.
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  • 44
    ISSN: 1432-0983
    Keywords: Yeast ; Mutant ; Triethyltin chloride ; Protein phosphorylation
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    Notes: Summary Three mutants of Saccharomyces cerevisiae resistant to triethyltin (an inhibitor of mitochondrial ATPase) on non-fermentative media, and non-resistant to this drug on fermentative media, were isolated and named TTR1, TTR2 and TTR3. Apart from triethyltin resistance, these mutants show the following common characteristics: (1) Increased intracellular cytochrome c concentration. (2) Increased respiration rate. (3) Decreased growth yield. (4) Increased growth sensitivity to several drugs inhibiting oxidative phosphorylation: namely, CCCP (permeabilizing inner mitochondrial membrane to protons), valinomycin (permeabilizing inner mitochondrial membrane to potassium) and oligomycin (inhibitor of mitochondrial ATPase). (5) Increased sensitivity to carbon source starvation. For each mutant, these characteristics appeared to be due to a single pleiotropic nuclear mutation. Mutation TTR1 causes additional phenotypic characteristics which do not appear in mutants TTR2 and TTR3: (1) Pinkish coloration of colonies which is more pronounced after a long growth period. (2) Inability of the cells to store glycogen. (3) Growth defect of the cells on a galactose-containing medium. (4) Inability of a diploid homozygote mutant strain to sporulate. All these phenotypic characteristics have already been described in yeast mutants deregulated in cAMP-dependant protein phosphorylation. Crossing of a strain bearing the TTR1 mutation with a strain mutated in the adenylate cyclase structural gene suggested that the TTR1 phenotype is due to a modification in regulation of cAPK by cAMP, making cell multiplication possible without intracellular cAMP.
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  • 45
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    Current genetics 17 (1990), S. 493-497 
    ISSN: 1432-0983
    Keywords: Mitochondria ; Yeast ; Petites
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    Topics: Biology
    Notes: Summary A pleiotropic, respiration-deficient mutant was isolated from the petite negative yeast Pachysolen tannophilus after UV mutagenesis. The mutant is unable to utilize xylose, arabinose, galactose or glycerol, and shows no detectable respiration when grown on glucose. Cytochrome c oxidase, xylose reductase and xylitol dehydrogenase activities are lacking. Mitochondrial ultrastructre is altered. The results support the hypothesis that functioning mitochondria are necessary for xylose utilization in this organism.
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  • 46
    ISSN: 1432-0983
    Keywords: Yeast ; Ty2 ; Protein/DNA binding ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A series of transposable element-induced mutations at the HIS4 locus in Saccharomyces cerevisiae have been attributed to the transposition of a Ty element into the 5′ regulatory region of this gene. Various Ty-containing His+ revertants have been isolated and the HIS4/Ty junction region sequenced. The only difference found in this region between a His- and a weak His+ strain was a single point mutation, an A→G transition. The position of Ty remained unaltered. Examination of lacZ fusion plasmids further implicated this A→G transition as being reponsible for the altered phenotype, the bp transition representing an allele of a cis-acting regulatory element. Subsequent gel retardation and methylation interference experiments revealed that this A→G mutation enabled the binding of a trans-acting factor (TyBf) in vitro. In this paper we show that the TyBf binding site is in a region of chromatin hypersensitive to digestion by DNase I. The binding site is protected in vivo from digestion with exonuclease III, suggesting the presence of a bound protein in His+ (“on”) but not His- (“off”) Ty-containing strains. We propose that a trans-acting factor binding in vivo, presumably TyBf, is responsible for the activation of HIS4 expression in these insertion mutants.
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  • 47
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Cytochrome c oxidase ; Post-translational regulation
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    Notes: Summary Biogenesis of functional cytochrome c oxidase in yeast requires the product of the nuclear gene SCO1. Strains deleted for this gene fail to accumulate the mitochondrially-synthesized cytochrome c oxidase subunits I and II, despite the presence of the respective mRNAs. Here we present data which demonstrate that the observed phenotype does not result from a failure to translate the mRNAs, but from a preferential degradation of the newly synthesized subunits. The SCO1 protein is therefore involved in a post-translational step in the accumulation of cytochrome c oxidase subunits I and II. We propose that the SCO1 protein is required for the correct assembly of both subunits into the cytochrome c oxidase complex.
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  • 48
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    Current genetics 2 (1980), S. 175-180 
    ISSN: 1432-0983
    Keywords: Yeast ; Hydroxyurea ; DNA synthesis
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    Topics: Biology
    Notes: Summary Newly synthesised DNA molecules the same size as replicons (7 million-60 million daltons) accumulate in yeast cells treated with hydroxyurea. During prolonged incubation in low concentrations of the drug, there is a large accumulation of these molecules without any corresponding increase in their molecular weight. On release from the inhibtion the molecules are converted to large molecular weight DNA. These observations are consistent with an inhibition by hydroxyurea of the joining of completed replicons. In addition, newly synthesised DNA molecules the size of yeast Okazaki fragments also accumulate in cells treated with hydroxyurea.
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  • 49
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    Current genetics 2 (1980), S. 193-200 
    ISSN: 1432-0983
    Keywords: Recombination ; Plasmids ; Transformation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary [2 μm+ and [2μm°] yeast were transformed to stable leucine prototrophy with the hybrid yeast — E. coli plasmid, pJDB219. This plasmid contains the entire sequence of the endogenous 2 μm yeast DNA plasmid in addition to the yeast nuclear LEU2 + gene and the Co1E1 derivative, pMB9. In the [2 μm+] transformants, a new wholly yeast LEU2 + plasmid, pYX, was generated, probably by a recombination event between pJDB219 and 2 μm DNA. The plamid, pYX, in the absence of 2 μm DNA, was found to exist in equimolar amounts of two forms, A and B, which probably arise by intramolecular recombination across the inverted repeat sequences of the 2 μm DNA portion of the plasmid. pJDB219 was found to require the presence of 2 μm DNA to undergo this intramolecular recombination. The results suggest that 2, μm DNA and pYX code for a gene product required in this recombination event which pJDB219 cannot produce.
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  • 50
    ISSN: 1432-0983
    Keywords: Yeast ; Mutant ; p-Fluoro-dl-phenylalanine ; β-Phenethyl-alcohol
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    Topics: Biology
    Notes: Summary p-Fluoro-dl-phenylalanine (PFP)-resistant mutants which produce a large amount of β-phenethyl-alcohol, a rose-like flavor component, were isolated from the isogenic strains X2180-1A and X2180-1B of Saccharomyces cerevisiae. Cells of these mutants accumulated phenylalanine and tryptophan more than 3-fold times that of wild-type cells, while they accumulated less than half the tyrosine. The activity of prephenate dehydrogenase (PDG) (EC 1.3.1.12) was markedly decreased while that of 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase (EC 4.1.2.15) was increased. Genetic analysis revealed that the mutation occurred at the TYR1 locus, encoding PDG, and that the mutated TYR1 gene, tyr1-pfp, caused both PFP resistance and β-phenethyl-alcohol overproduction. This was supported by molecular genetic studies with cloned tyr1-pfp DNA.
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  • 51
    ISSN: 1432-0983
    Keywords: Peptides ; Transport ; Regulation ; Yeast
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    Topics: Biology
    Notes: Summary The transport of small peptides into the yeast Saccharomyces cerevisiae is subject to complex regulatory control. In an effort to determine the number, and to address the function, of the components involved in peptide transport and its regulation, spontaneous mutants resistant to toxic di- and tripeptides were isolated under inducing conditions. Twenty-four mutant strains were characterized in detail and fell into two phenotypic groups; one group deficient in amino acid-inducible peptide uptake, the other with a pleiotropic phenotype including a loss of peptide transport. Complementation analysis of recessive mutations in 12 of these strains defĩned three groups; ptr1 (nine strains), ptr2 (two strains), and ptr3 (one strain). Isolation and screening of 31 additional N-methyl-N-nitro-N-Nitrosoguanidine (MNNG)-induced, peptide transport-deficient mutants produced one ptr3 and 30 ptr2 strains: no additional complementation groups were detected. Uptake of radiolabeled dileucine was negligible in ptr1 and ptr2 strains and was reduced by 65% and 90% in the two ptr3 mutants, indicating that all strains were defective at the transport step. We conclude that the S. cerevisiae amino acid-inducible peptide transport system recognizes a broad spectrum of peptide substrates and involves at least three components. One gene, PTR3, may play an indirect or regulatory role since mutations in this gene cause a pleiotropic phenotype.
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  • 52
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    Journal of molecular evolution 38 (1994), S. 1-17 
    ISSN: 1432-1432
    Keywords: HSP70 ; Heat shock ; Evolution ; Phylogeny ; Yeast ; Multigene family ; Subcellular compartmentalization
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    Topics: Biology
    Notes: Abstract Eukaryotic genomes encode multiple 70-kDa heat-shock proteins (HSP70s). The Saccharomyces cerevisiae HSP70 family is comprised of eight members. Here we present the nucleotide sequence of the SSA3 and SSB2 genes, completing the nucleotide sequence data for the yeast HSP70 family. We have analyzed these yeast sequences as well as 29 HSP70s from 24 additional eukaryotic and prokaryotic species. Comparison of the sequences demonstrates the extreme conservation of HSP70s; proteins from the most distantly related species share at least 45% identity and more than one-sixth of the amino acids are identical in the aligned region (567 amino acids) among all proteins analyzed. Phylogenetic trees constructed by two independent methods indicate that ancient molecular and cellular events have given rise to at least four monophyletic groups of eukaryotic HSP70 proteins. Each group of evolutionarily similar HSP70s shares a common intracellular localization and is presumed to be comprised of functional homologues; these include heat-shock proteins of the cytoplasm, endoplasmic reticulum, mitochondria, and chloroplasts. HSP70s localized in mitochondria and plastids are most similar to the DnaK HSP70 homologues in purple bacteria and cyanobacteria, respectively, which is consistent with the proposed prokaryotic origin of these organelles. The analyses indicate that the major eukaryotic HSP70 groups arose prior to the divergence of the earliest eukaryotes, roughly 2 billion years ago. In some cases, as exemplified by the SSA genes encoding the cytoplasmic HSP70s of S. cerevisiae, more recent duplication events have given rise to subfamilies within the major groups. The S. cerevisiae SSB proteins comprise a unique subfamily not identified in other species to date. This subfamily appears to have resulted from an ancient gene duplication that occurred at approximately the same time as the origin of the major eukaryotic HSP70 groups.
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  • 53
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    Journal of molecular evolution 32 (1991), S. 396-404 
    ISSN: 1432-1432
    Keywords: Yeast ; Mitochondrial DNA ; Polymirphism ; Repeated sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A spontaneously arising mitochondrial DNA (mtDNA) variant ofSaccharomyces cerevisiae has been formed by two exta copies of a 14-bp sequence (TTAATTAAATTATC) being added to a tandem repeat of this unit. Similar polymorphisms in tandemly repeated sequences have been found in a comparison between mtDNAs from our strain and others. In 5850 bp of intergenic mtDNA squence, polymorphisms in tandemly repeated sequences of three or more base pairs occur approximately every 400–500 bp whereas differences in 1–2 bp occur approximately every 60 bp. Some polymorphisms are associated wit optional G+C-rich sequences (GC clusters). Two such optional GC clusters and one A+T repeat polymorphism have been discovered in the tRNA synthesis locus. In addition, the variable presence of large open reading frames are documented and mechanisms for generating intergenic sequence diversity inS. cerevisiae mtDNA are discussed.
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  • 54
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    Journal of molecular evolution 32 (1991), S. 439-442 
    ISSN: 1432-1432
    Keywords: Yeast ; Mitochondrial DNA ; ori ; rep ; Polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Threeori elements (ori 2,ori 5, andori 7) have been sequenced inSaccharomyces cerevisiae strain Dip 2 and compared to the equivalentori elements of a second strain (B). Bothori 2 andori 5 exhibit 98% base matching between strains Dip 2 and B. In contrast, the thirdori element (ori 7) exhibits extensive sequence rearrangements whereby a segment located downstream in the consensus strain occurs within theori structure in Dip 2. This represents a novel polymorphic form of the yeast mitochondrial genome.
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  • 55
    ISSN: 1432-1432
    Keywords: Yeast ; E. coli ; tRNA ; rRNA ; Sequence homologies ; Evolution ; Origins ; Coding mechanism
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary Many tRNAs ofE. coli and yeast contain stretches whose base sequences are similar to those found in their respective rRNAs. The matches are too frequent and extensive to be attributed to coincidence. They are distributed without discernible pattern along and among the RNAs and between the two species. They occur in loops as well as in stems, among both conserved and non-conserved regions. Their distributions suggest that they reflect common ancestral origins rather than common functions, and that they represent true homologies.
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  • 56
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    Journal of comparative physiology 171 (1992), S. 505-512 
    ISSN: 1432-1351
    Keywords: anduca sexta ; Olfaction ; Pheromones ; Temporal coding ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We investigated the ability of pheromone-sensitive olfactory receptors of male Manduca sexta to respond to 20-ms pulses of bombykal, the major component of the conspecific pheromonal blend. Isolated pulses of bombykal elicited a burst of activity which decreased exponentially with a time constant of 160–250 ms. Trains of pulses delivered at increasing frequencies (0.5–10 Hz) elicited temporally modulated responses at up to 3 Hz. Concentration of the stimulus (1, 10, 100 ng per odor source) had a marginal effect on the temporal resolution of the receptors. Within a train, the responses to individual pulses remained constant, except for 10-Hz trains (short-term adaptation). A dose-dependent decline of responsiveness was observed during experiments (long-term adaptation). Although individual neurons may not respond faithfully to each pulse of a train, the population of receptors sampled in this study appears to be capable of encoding the onset of odor pulses at frequencies of up to at least 3 Hz.
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  • 57
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    Journal of comparative physiology 171 (1992), S. 573-581 
    ISSN: 1432-1351
    Keywords: Insect retina ; Extracellular calcium ; Species differences ; Photoreceptor ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ion-selective microelectrodes inserted into the compound eyes of Calliphora, Locusta and Apis were used to monitor the changes in extracellular concentration of Ca2+ (Cao) brought about by a 1-min exposure to white light (maximal luminous intensity ca. 103 cd/m2). In the blowfly retina such stimulation causes a decrease in Cao. At high light intensities the Cao signal is phasic, falling over about 6 s to a transient light-induced minimum (ΔCao= -6.2% ± 0.4%, n = 20, SE) and then rising to an approximately stable plateau (-3.3% ± 0.6%). In migratory locusts the light-induced minimum corresponds to a ΔCao of -13.8% ± 1.6% (n = 10), and at the plateau the Cao decrease is-13.2% ± 1.5%. In honey-bees Cao at first decreases only slightly, by -2.6% ± 1.0% (n = 10); by the end of the 1-min stimulus the extracellular concentration averages 33.6% ± 14.6% above the dark level. The results suggest a relationship between the position of the characteristic curve of the photoreceptor in the dark-adapted state, the occurrence of quantum bumps, and light-induced increases or decreases in Cao. Therefore the species differences might be interpreted as a consequence of differences in the intracellular dark concentration of Ca2+.
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  • 58
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    Journal of comparative physiology 172 (1993), S. 583-591 
    ISSN: 1432-1351
    Keywords: Natural images ; Spatiotemporal filtering ; Adaptation ; Eye design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. Optimal spatiotemporal filters for early vision were computed as a function of signal-to-noise ratio (SNR) and α, a parameter defined as the ratio of the width of the probability distribution of velocities as perceived by the naturally behaving animal, and the characteristic velocity of the photoreceptors (the velocity required to move across a receptor's receptive field in a receptor's integration time). Animals that move slowly, on average, compared with the characteristic velocity of their photoreceptors have α ≪ 1, animals that move fast have α ≫ 1. 2. For α ≪ 1, the temporal part of the optimal filter adapts more to different SNRs (light levels) than the spatial part, leading to large adjustments in temporal resolving power and strong self-inhibition at high SNR, but little lateral inhibition. 3. For α ≫ 1, the spatial part of the filter adapts more strongly than the temporal part, leading to strong lateral inhibition at high SNR, and little self-inhibition. 4. For α ≈ 1, both spatial and temporal properties change about equally much when varying SNR. 5. Varying the width of the angular sensitivity of the photoreceptors shows that for every combination of α and SNR there is an optimal width. Visual systems with large α need wider angular sensitivities, in particular at low SNR, in order to reach the information maximum than visual systems with small α.
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  • 59
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    Journal of comparative physiology 175 (1994), S. 267-278 
    ISSN: 1432-1351
    Keywords: Drosophila ; Bang sensitivity ; Mechanotransduction ; Adaptation ; Sensory coding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Bang-sensitive mutants of Drosophila melano gaster (bas 1, bssMW1, eas2, tko25t) display seizure followed by paralysis when subjected to mechanical shock. However, no physiological or biochemical defect has been found to be common to all of these mutants. In order to observe the effects of bang-sensitive mutations upon an identified neuron, and to study the nature of mechanically induced paralysis, we examined the response of a mechanosensory neuron in these mutants. In each single mutant and the double mutant bas 1 bssMW1, the frequency of action potentials in response to a bristle displacement was reduced. This is the first demonstration of a physiological defect common to several of the bang-sensitive mutations. Adaptation of spike frequency, cumulative adaptation to repeated stimulation (fatigue) and the time course of recovery from adaptation were also examined. Recovery from adaptation to a conditioning stimulus was examined in two mutants (bas 1 and bss MW1), and initial recovery from adaptation was greater in both mutants. Quantification of receptor potentials was complicated by variability inherent in extracellular recording conditions, but examination of the waveform and range of amplitudes did not indicate clear mutant defects. Therefore the differences observed in the spike response may be due to an alteration of the transfer from receptor potentials to action potential production. DNA sequence analysis of tko and eas has indicated that they encode apparently unrelated biochemical products. Our results suggest that these biochemical lesions lead to a common physiological defect in mechanoreceptors. Although this defect does not provide a straightforward explanation for bang sensitivity, the altered cellular process may lead to bang sensitivity through its action in different parts of the nervous system.
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  • 60
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    Journal of molecular evolution 30 (1990), S. 196-201 
    ISSN: 1432-1432
    Keywords: Human evolution ; Australian songbirds ; Convergent evolution ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This article draws on many vertebrate examples to assess the future of DNA-DNA hybridization studies. I first discuss whether applications of the method have reached the point of diminishing returns, or rather the start of a great leap forward, in our evolutionary understanding. Vertebrate groups whose relationships are especially likely to be illuminated include parrots, pigeons, bats, pinnipeds, mammalian carnivores, frogs, and rodents. There are at least two reasons why classifications based on DNA-DNA hybridization may prove to differ from classifications based on particular character, whether these be noncoding DNA sequences or protein sequences or anatomical characters. Because evolutionary relationships can now be deduced independently of anatomical characters, this should permit a renaissance in comparative anatomical studies of adaptation. The origin of major functional shifts from changes in a small fraction of the genome is illustrated by polar bears, sea otters, warblers, vultures, and especially by humans.
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  • 61
    ISSN: 1432-1432
    Keywords: Evolution ; Gene regulation ; Drosophila ; Adaptation ; Enzymes
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    Notes: Abstract In an effort to understand the forces shaping evolution of regulatory genes and patterns, we have compared data on interspecific differences in enzyme expression patterns among the rapidly evolving Hawaiian picture-winged Drosophila to similar data on the more conservative virilis species group. Divergence of regulatory patterns is significantly more common in the former group, but cause and effect are difficult to discern. Random fixation of regulatory variants in small populations and/or during speciation may be somewhat more likely than divergence driven by selection. Within the picture-winged group, we also have compared enzymes that fulfill different metabolic roles. There are highly significant differences between individual enzymes, but no obvious correlations to functional categories.
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  • 62
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    European journal of nutrition 31 (1992), S. 178-188 
    ISSN: 1436-6215
    Keywords: Thermogenese ; Adaptation ; Energiebilanz ; Unterernährung ; Überernährung ; thermogenesis ; adaptation ; energy balance ; underfeeding ; overfeeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary In a model experiment eight adult sows were used to examine the effect of successive periods of under- and oversupply of energy (MÜMÜ) on thermogenesis and efficiency of energy utilization in comparison to a constant maintenance supply (NNNN). Each treatment sequence was assigned to each animal according to a change-over design over 8 weeks. Before and after the treatment periods all the animals were fed at maintenance level (N). Energy deficiency (M) was performed by use of a basal diet with 45 % of maintenance energy requirements and values for all the other nutrients sufficient for requirements. Normal (N) and excessive (Ü) intakes of energy was provided with supplements of starch. The total intake of gross energy during the periods MÜMÜ was exactly the same as during NNNN. Complete energy balances were performed for each animal and period as well as during the pre- and post-experimental phase. There was no or little response of altered energy intake on carbon and energy excretion in faeces, urine and methane. However, heat production was significantly decreased by 4.1 % on energy deficiency, and increased by 15.1 % during energy oversupply. Summed up over the total sequence the animals produced 5.4 % more heat on MÜMÜ than during NNNN. This response was associated with a mobilization of 1.1 MJ/d tissue energy and a decrease in body weight by 2.0 kg. The efficiency of utilization of ME was 88 % with energy undersupply and 75 % during overnutrition. Criteria of energy balance did not differ between the pre- and post-treatment periods. It could be demonstrated that the increase in energy expenditure at oversupply was entirely explainable by the so-called obligatory thermogenesis. At the energy deficiency periods the efficiency of energy utilization reflected both energy costs of ingestion and processing of nutrients as well as a slight reduction in metabolic rate. Finally, there were no residual effects of the treatment on the energy expenditure of the animals at the end of the experiment.
    Notes: Zusammenfassung In einem Modellversuch mit 8 nichtgraviden, nichtlaktierenden Sauen wurde eine alternierende Mangel- und Überfütterung an Energie über 8 Wochen im Vergleich zur Fütterung auf Erhaltungsniveau durchgeführt. Das Experiment war in Form eines changeover-Plans angelegt. Energiemangel wurde mit einer Basisration realisiert, die 45 % des energetischen Erhaltungsbedarfs lieferte, alle anderen Nähr- und Wirkstoffe aber bedarfsdeckend enthielt. Normalzufuhr an Energie und Energieüberschuß wurden durch Zulage von Stärke hergestellt. Die Zufuhr an Bruttoenergie war in der Summe von Energiemangel und Energieüberschuß exakt gleich der Fütterung auf Normalniveau. Von jedem Tier wurde in jeder Rationsperiode eine vollständige Messung der C-, N- und Energiebilanz durchgeführt. Zusätzlich wurde der Bilanzstatus aller Sauen unter Normalfütterung vor und nach den change-over-Perioden ermittelt. Die alternierende Energiezufuhr hatte keine oder nur minimale Effekte auf die C- und Energieausscheidung in Kot, Harn und CH4. Dagegen war die Wärmeproduktion bei Energiemangel signifikant um 4,1 % erniedrigt und bei Energieüberschuß um 15,1 % erhöht. In der Summe lag die Wärmebildung bei alternierender Versorgung um 5,4 % höher als bei Normalfütterung. Dies hatte eine Mobilisation von täglich 1,1 MJ Körperenergie zur Folge und erklärte auch die Abnahme der Lebendmasse der Tiere um 2,0 kg. Die Wirkungsgrade der ME beliefen sich auf 88 % bei Energiemangel und auf 75 % bei Energieüberversorgung. Die Bilanzdaten nach der Versuchsbehandlung waren gegenüber den vor Versuch ermittelten Werten nicht verändert. Unter den vorliegenden Bedingungen des Energieüberschusses konnte kein Hinweis auf eine diätinduzierte regulatorische Komponente der Thermogenese gefunden werden. Die beobachteten Effekte ließen sich vollständig durch die Theorie der obligatorischen Wärmebildung bei Nährstofftransformation erklären. Im Energiemangel war dagegen eine Adaptation der Stoffwechselrate festzustellen.
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    Calcified tissue international 36 (1984), S. S118 
    ISSN: 1432-0827
    Keywords: Bone ; Strain ; Remodeling ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary For bone to remodel adaptively, the cells responsible should follow some algorithm. Nine different loading situations and structures are discussed. It seems that either algorithm must be extremely complex, or cells in different structures must follow different algorithms.
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    Oecologia 97 (1994), S. 179-185 
    ISSN: 1432-1939
    Keywords: Diapause ; Development ; Grasshopper ; Adaptation ; Geographic variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryonic development times and the stage at which embryonic diapause occurs varied dramatically among 23 populations of the Melanoplus sanguinipes/ devastator species complex in California, USA. Grasshoppers were collected from a wide range of latitudes (32°57N to 41°20N) and altitudes (10m to 3031 m), spanning much of the variation in climatic conditions experienced by these insects in California. When reared in a “common garden” in the laboratory, total embryonic development times were positively correlated to the mean annual temperature of the habitat from which the grasshoppers were collected (varying from about 19 days to 32 days when reared at 27°C). These grasshoppers overwinter as diapausing eggs and the proportion of embryonic development completed prior to diapause was significantly higher in populations collected from cool habitats (〉70%) than in populations collected from warm environments (〈26%). The length of pre-diapause development time is determined by the stage of embryonic development at which diapause occurs, and varies considerably among populations of these grasshoppers; grasshoppers from warmer environments tend to diapause at very early stages of embryogenesis, while grasshoppers from cooler environments diapause at very late stages. The combined effect of variation in embryonic development times and variation in the stage at which diapause occurs results in a dramatic reduction in the time needed to hatch in the spring; populations from warm environments required up to 20 days (at 27°C) to hatch while populations from cool environments required as few as 5 days to complete embryonic development prior to hatching. Egg size also varied significantly among populations, but tended to be larger in populations with shorter embryonic development times. Significant family effects were observed for development time and stage of diapause, suggesting significant heritabilities for these traits, although maternal effects may also contribute to family level variation. We interpret these findings to support the hypothesis that embryonic development time and the stage of embryonic diapause have evolved as adaptations to prevailing season lengths in the study populations.
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  • 65
    ISSN: 1432-1939
    Keywords: Adaptation ; Leaf pubescence ; Leaf reflectance ; Desert ecology
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    Topics: Biology
    Notes: Summary The performance of coastal and desert species of Encelia (Asteraceae) were evaluated through common garden growth observations. The obectives of the study were to evaluate the roles of leaf features, thought to be of adaptive value (increased leaf reflectance and/or transpirational cooling), on plant growth in the hot, arid, desert garden versus their impact on growth under cooler, relatively more moist coastal garden conditions. E. californica native to the coast of southern California and E. farinosa, and E. frutescens, interior desert species, were grown in common gardens at coastal (Irvine, California) and interior (Phoenix, Arizona) sites under both irrigated and natural conditions. Although all species survived in both gardens during the two and a half year study period, there were large differences in their sizes. In the desert garden, leaf conductance and leaf water potential were both lower than at the coastal site. E. californica shrubs were leafless much of the time under natural conditions in the desert garden and had the smallest size there as well. Under natural conditions, E. farinosa, with its reflective leaf surface, was able to maintain lower leaf temperatures and attained a large size than the other two species in the desert garden. The green-leaved species (E. californica and E. frutescens) were not able to maintain leaves into the drought periods in the desert garden, with the exception of the irrigated E. frutescens which did maintain its leaf area if provided with supplemental watering to maintain transpirational leaf cooling. In the coastal garden, all species survived and there were few clear differences in the physiological characteristics among the three species. E. californica, the coastal native, attained a larger size in the coastal garden when compared with either of the two desert species.
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  • 66
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Cytochrome oxidase
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    Topics: Biology
    Notes: Summary We have analyzed a mutation in the mitochondrial gene oxi3 coding for subunit I of cytochrome-oxidase in the yeast Saccharomyces cerevisiae. This mutation replaces one of the seven invariant histidines of the polypeptide (position 378) by a tyrosine, and leads to a respiratory deficient phenotype. A total of 157 revertants, which have recovered the ability to grow on a respiratory substrate, have been selected from this mutant (tyrosine 378). The nature of the reversion has been analysed by a rapid screening procedure and 32 of the revertants have been sequenced. They are all true backmutations reintroducing the histidine in position 378. This very exceptional situation suggests that this histidine is a ligand of the redox center of cytochrome oxidase.
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  • 67
    ISSN: 1432-0983
    Keywords: Yeast ; DNA-polymerase α ; Cell cycle
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    Topics: Biology
    Notes: Summary The 5′ ACGCGT3′ MluI motif, which is found in the upstream region of several yeast DNA-synthesis genes which are periodically expressed during the mitotic cell-cycle, is present twice in the 5′ non-coding region of the DNA-polymerase α gene (POL1). Deletion, of the most distal repeat does not affect POL1 transcription, while the adjacent 40 base-pair (bp) downstream sequence is necessary both for the proper level and the fluctuation of POL1 mRNA. This region contains the 5′ACGCGTCGCGT3′ sequence, which is sufficient to control periodic transcription of a CYC1-lacZ reporter gene with the same kinetics observed for POL1. The adjacent 29 bp AT-rich region does not show any activity by itself, but it acts synergistically in conjunction with at least one MluI hexamer to stimulate CYC1-lacZ expression. By further deletion analysis, DNA sequences necessary to initiate POL1 transcription at the proper sites have also been identified.
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    Current genetics 21 (1992), S. 203-206 
    ISSN: 1432-0983
    Keywords: Yeast ; Galactokinase ; Mutant selection
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    Topics: Biology
    Notes: Summary The galactose analogue 2-deoxy-galactose (2DG) has been widely used to select for mutations in the gene encoding the galactose pathway enzyme galactokinase (GalK). We have tested the effect of 2DG on Candida albicans to see if it could be used to obtain GalK- mutants in this diploid asexual yeast. 2DG was shown to be toxic to wild-type cells. Enzyme assays demonstrated that 2DG can induce GalK as efficiently as galactose. Examination of the initital rate of galactose uptake indicated that the galactose transport system is constitutive. 2DG-resistant mutants were isolated from mutagenized cultures and shown to have very low levels of GalK activity. The potential genetic applications of this system of direct mutant selection are discussed.
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  • 69
    ISSN: 1432-0983
    Keywords: Repressor ; Zinc finger ; Leucine zipper ; GATA-1 ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The UGA43 gene of Saccharomyces cerevisiae is required for repression of inducible genes involved in the utilization of 4-aminobutyric acid (GABA) or urea as nitrogen sources. The UGA43 gene has been cloned by complementation of a uga43 mutation. The N-terminal region of the UGA43 protein is very similar to the DNA-binding zinc-finger region typical of the GATA regulatory factor family in vertebrates. UGA43 is the first reported instance of a GATA protein with a negative regulatory function. The C-terminal region of the predicted UGA43 protein contains a putative leucine zipper. Sequencing of three uga43 mutant alleles suggests that the GATA and putative leucine-zipper regions are both required for the repressive activity of UGA43. UGA43 appears to be a highly regulated gene. On “poor” nitrogen sources, UGA43 transcripts are measured at high levels whereas they are nearly undetectable in conditions of nitrogen catabolite repression. The levels measured on “poor” nitrogen sources are further increased in uga43 mutant cells, suggesting that UGA43 exerts negative autoregulation.
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  • 70
    ISSN: 1432-0983
    Keywords: Yeast ; cAMP ; RAS ; GAP
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    Topics: Biology
    Notes: Summary The ccs1-1 mutation of Saccharomyces cerevisiae, which has been previously described, is associated with an increase in cytochrome content, in respiration, and in ATP synthesis. In addition, this mutation leads to the same phenotype as cells de-regulated in the cAMP pathway. From a yeast genomic library, we have isolated a DNA fragment in a recombinant plasmid pCD1 which complements the ccs1-1 mutation. Homologous integration of this DNA in the genome occurs at the CCS1 locus. An 11 kb of the DNA insert is necessary for complementation. Sequencing part of the fragment identifies CCS1 as the IRA2 gene. The IRA2 gene is known to encode an attenuator of RAS gene product activity which stimulates the GTPase activity of the RAS proteins. This result underlines the involvement of cAMP-dependent phosphorylation in mitochondrial function. We present the sequence of 1 kb DNA upstream of the putative ATG of the IRA2/CCS1 gene product which is devoid of an ORF and could contain several regulatory sites.
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    Current genetics 24 (1993), S. 21-25 
    ISSN: 1432-0983
    Keywords: Yeast ; Glycerol kinase ; GUT1 ; ADR1 control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The GUT1 gene of Saccharomyces cerevisiae, encoding glycerol kinase, was cloned and sequenced. The cloned genomic DNA fragment contains an open reading frame potentially coding for a protein of 709 amino acids with homology to bacterial glycerol kinases (40.8% identity over 502 amino acids, and 42.1% identity over 496 amino acids, in comparison to the smaller E. coli and B. subtilis enzymes). Disruption of GUT1 showed that the gene is required for growth on glycerol, but not on glucose or ethanol media. No glycerol kinase activity was detected in the disruption mutant. According to enzyme activity and transcript analysis, synthesis of glycerol kinase is repressed by glucose, and derepression is ADR1-dependent.
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  • 72
    ISSN: 1432-0983
    Keywords: Yeast ; FLP ; Phase variation-type expression ; Gene replacement
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    Topics: Biology
    Notes: Abstract Expression of a neomycin phosphotransferase II (NPTII) gene has been designed to be regulated by an FLP-mediated switching of the orientation of the NPTII coding region located on the invertible DNA segment in episomal yeast plasmids. Inversion of the segment from inverted to direct orientation with respect to the promoter resulted in a dramatic increase in G418 resistance. FLP also promoted a double reciprocal exchange between the transforming and the resident 2-μm plasmid, leading to insertion of the FLP and REP2 genes into the transforming plasmid. The results demonstrate a possible use of FLP recombinase for ‘phase variation’-type regulation of gene expression and gene replacement in eukaryotic cells.
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  • 73
    ISSN: 1432-0983
    Keywords: DNA repair ; Heat shock ; Hyperthermia ; Mutagenesis ; pso3-1 mutant ; Psoralen ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A putative tolerance, induced by heat shock (HS), to the lethal and mutagenic effects of 8-methoxypsoralen (8-MOP) photoaddition and hyperthermia was analyzed in Saccharomyces cerevisiae using the wild-type strain N123 and the isogenic DNA repair-deficient mutant pso3-1. In wild-type cells, the HS (38°C for 1 h) did not modify either the survival or the mutation frequency observed after 8-MOP photoaddition, even though it conferred protection against the lethal effect of hyperthermia (50°C). In the pso3-1 mutant, HS induced an increase of the survival, and a decrease of the mutation frequency, after 8-MOP photoaddition and it also protected against the lethal effect of hyperthermia. The responses induced by HS were specific for 8-MOP photoaddition, since they were not observed after 254 nm ultraviolet-light damage. These results indicate that the protection conferred by HS depends of the type of lesion, and operates through the induction of different repair processes. In the pso3-1 mutant, HS could channel the repair intermediates to and error-free repair pathway.
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  • 74
    ISSN: 1432-0983
    Keywords: AEP1 ; Yeast ; Mitochindria ; ATP synthase ; PET gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Due to mutation in a single nuclear locus, AEP1, the temperature-conditional pet mutant ts1860 of Saccharomyces cerevisiae fails to synthesize mitochondrial ATP synthase subunit 9 at the restrictive temperature of 36°C. The presence at this temperature of near-normal levels of the cognate oli1 mRNA in mutant ts1860 indicates that, as previously shown, the product of the AEP1 gene is required for translation of the mitochondrial oli1 transcript. In this study the AEP1 gene has been cloned from a wild-type yeast genomic library by genetic complementation of a temperature-conditional aep1 strain at the restrictive temperature. A 2,330-bp genomic fragment which restores subunit 9 synthesis in aep1 mutant strains was characterized. This fragment encoded five open reading frames: the longest of these, at 1,554 nucleotides, was identified as the AEP1 gene, since disruption of this reading frame generated a non-conditional pet strain unable to synthesize subunit 9. The predicted product of AEP1 is a basic, hydrophilic protein of 59,571 Da which possesses a putative mitochondrial address sequence. Hybridization studies with AEP1-specific probes indicate that the gene is located on chromosome XIII and produces several poly(A)+ transcripts ranging in size from 0.9 to 2.7 kb. None of the identified reading frames share significant homologies with entries of several data bases.
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  • 75
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    Current genetics 24 (1993), S. 179-180 
    ISSN: 1432-0983
    Keywords: Mapping ; Yeast ; Schizosaccharomyces pombe
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    Topics: Biology
    Notes: Abstract The genetic map of the fission yeast Schizosaccharomyces pombe has been revised in the distal region of chromosome arm IIR. The spo4 locus, hitherto considered the outermost marker, has been moved to an intermediate position. As a result, and in accordance with recent physical mapping data, the order of the entire distal subgroup of some 12 genetic markers is reversed relative to previously published gene maps.
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  • 76
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    Current genetics 26 (1994), S. 281-284 
    ISSN: 1432-0983
    Keywords: Ofloxacin ; Mitochondria ; Mutation ; Recombination ; Topoisomerase ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ofloxacin, a specific inhibitor of bacterial topoisomerase II, is known to inhibit the growth of yeast cells and to induce rho − mutants in the yeast S. cerevisiae. The frequency of ofloxacin-induced petite mutants under non-growth conditions was found to be strongly diminished when the cells were depleted in intramitochondrial ATP. Under optimal conditions of mitochondrial mutagenesis the drug induced mitotic recombination and reverse mutation in diploid strains but failed to cure either killer plasmids or the 2 μm DNA of dividing cells. The sensitivity to ofloxacin of the strains deficient in the DNA strandbreak repair pathway (rad52) was significantly higher then that of the wild-type strains and of the mutants deficient in excision or mutagenic DNA repair. The results are compatible with the idea that the cytotoxic and genetic activity of ofloxacin in yeast probably results from the inhibited DNA ligation function of topoisomerase II creating DNA breaks that are reparable through the recombination repair pathway.
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  • 77
    ISSN: 1432-0983
    Keywords: Yeast ; Trehalose synthase ; GGS1/TPS1 gene ; Glycolysis ; Fermentable sugars ; Suppression
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    Topics: Biology
    Notes: Abstract Byp1-3 is an amber nonsense allele of the Sacchromyces cerevisiae GGS1/TPS1 gene which encodes the small subunit of the trehalose synthase complex. Mutations in this gene confer an inability to grow on glucose or fructose but the phenotype of byp1-3 mutants is leaky in a strain-dependent manner. Overexpression of the isolated byp1-3 allele suppressed the growth defect of a ggs1/tps1Δ mutant. Expression of an in-vitro-generated mutant allele of GGS1/TPS1 that lacks all the coding sequences downstream from the byp1-3 mutation led to the production of a shortened protein that did not complement the ggs1/tps1Δ mutant. We have isolated, as an allele-specific multi-copy suppressor of the growth defect of the byp1-3 mutant on fructose, the gene for tRNAGLN (CAG). Thus the leaky phenotype of byp1-3 mutants is due to a low level of read through of the internal nonsense codon by tRNAGLN (CAG). Using overexpression of the isolated byp1-3 allele, as well as of the tRNAGLN (CAG) gene, we were able to demonstrate that as little as about 10% of the normal Ggs1/Tps1 protein level is sufficient for slow growth on fructose. We also show a correlation between the level of Ggs1/Tps1, the ability to accumulate trehalose in stationary phase and the ability to grow on fermentable sugars. Sequence analysis of the cloned tRNAGLN (CAG) gene showed that it is located 700 bp upstream of URA10. However, we found considerable differences to the reported sequence of URA10, in particular in the non-coding region.
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  • 78
    ISSN: 1432-0983
    Keywords: Small G proteins ; YPT1 ; Yeast ; abGDI ; Mitochondria ; MRS2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract MRS6 is a newly-identified gene in the yeast Saccharomyces cerevisiae. Its product Mrs6p shows significant homology to the mammalian GDP dissociation inhibitor (GDI) of Rab/Ypt-type small G proteins and to the human choroideraemia protein (CHM), the component A of Rab-specific GGTase II. The interaction of Mrs6p with G proteins is indicated by our observation that the MRS6 gene suppresses the effect of a temperature-sensitive ypt1 mutation. Disruption of the MRS6 gene is lethal to haploid yeast cells. This is consistent with the notion that Mrs6p is interacting with Rab/Ypt-type small G proteins, which are known to have essential functions in vesicular transport. Unexpeciedly, the MRS6 gene product also affects mitochondrial functions as revealed by the facts that highcopy numbers of MRS6 (1) suppress the pet - phenotype of mrs2-1 mutant strains and (2) cause a weak pet - phenotype in wild-type strains. We conclude from these results that the MRS6 gene product has a vital function in connection with Rab/Ypt-type proteins in the cytoplasm and, in addition, affects mitochondrial functions.
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  • 79
    ISSN: 1432-0983
    Keywords: 2-Oxoglutarate dehydrogenase ; Molecular cloning ; Saccharomyces cerevisiae ; Sequencing ; Suppressor ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity of mitochondrial 2-oxoglutarate dehydrogenase in S. cerevisiae can be impaired either by the ogd1 or the kgd1 mutation. The OGD1 gene and two suppressor genes were isolated by complementation of the ogd1 mutant. The complementation of the kdg1 mutant by the OGD1 gene, an allelism test, and meiotic mapping, revealed that the ogd1 and kgd1 mutations are allelic. The two mutations were differentiated by the cloned suppressor gene which was able to partially complement ogd1, but not kgd1. The molecular analysis of the suppressor gene revealed its identity with the natural tRNA CAG Gln gene found in the upstream region of URA10.
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  • 80
    ISSN: 1432-0983
    Keywords: Yeast ; Cell cycle ; Sporulation ; Glycoprotein gp115
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    Topics: Biology
    Notes: Abstract The GGP1 (GAS1) gene encodes an exocellular 115-kDa glycoprotein (gp115) of the yeast Saccharomyces cerevisiae. We have monitored the changes in GGP1 mRNA levels under different conditions of G1 arrest. Transcript levels rapidly decrease during transition from exponential growth to stationary phase. They also decrease in the ts cdc25 and cdc28 START mutants when brought to the restrictive temperature. In cells arrested in G1 by αF treatment, the GPP1 mRNA level undergoes a threefold reduction. During release from the G1 block the mRNA level rapidly increases with a maximum at the onset of budding. During sporulation GGP1 mRNA level steadily decreases. These results indicate that the accumulation of the GGP1 transcript is inhibited during arrest in the G1 phase and during entry into the differentiative pathway of meiosis and sporulation. The induction of expression upon entry into the mitotic cycle suggest that GGP1 could be one of the genes whose transcription is activated at START.
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  • 81
    ISSN: 1432-0983
    Keywords: Yeast ; Saccharomyces cerevisiae ; Sporulation mutants ; Reporter genes
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    Notes: Abstract Reporter genes consisting of sporulation-specific promoters fused to lacZ were used as markers to monitor the sporulation pathway of the yeast Saccharomyces cerevisiae. Strains transformed with these lacZ gene fusions expressed β-galactosidase (assayable on plates using the substrate 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside, X-gal) in a sporulation-dependent manner. Mutagenesis experiments performed on transformed strains resulted in the recovery of a number of novel sporulation mutants. Three classes of mutants were obtained: those which overexpressed the reporter gene under sporulation conditions, those which did not express the gene under any conditions, and those which expressed the gene in vegetative cells not undergoing sporulation. On the basis of the blue colony-colour produced in the presence of X-gal these have been described as superblue, white, and blue vegetative mutants, respectively. These were further characterised using earlier reporter genes and other marker systems. This study established that the multicopy reporter plasmids chosen do not interfere with sporulation; they are valid tools for monitoring the pathway and they provide a way to isolate mutations not readily selected by other markers.
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  • 82
    ISSN: 1432-0983
    Keywords: Yeast ; Saccharomyces cerevisiae ; Transformation ; Plasmid
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    Topics: Biology
    Notes: Abstract We have compared a number of procedures for the transformation of whole cells of the yeast Saccharomyces cerevisiae and assessed the effects of dimethylsulphoxide (DMSO) or ethanol, both of which have been reported to enhance transformation efficiency. We find that simplified methods benefit from the addition of one of these compounds, and although differences are observed between strains as to the more beneficial reagent, peak transformation efficiency is, in general obtained with 10% DMSO or 10% EtOH. Increases of between six- and 50-fold are observed, despite a reduction in cell viability, and at this concentration the two compounds are not additive in their effects. The optimum level appears to depend on a balance between improved DNA uptake and reduced cell viability. As a result of this work we present a straightforward and rapid transformation procedure.
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  • 83
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    Current genetics 24 (1993), S. 481-486 
    ISSN: 1432-0983
    Keywords: Mitotic recombination ; RAD3 gene ; Nucleotide excision repair ; Yeast
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    Notes: Abstract We have tested the ability of mutants of three additional genes in the excision repair pathway of Saccharomyces cerevisiae to suppress the hyper-recombination and rad52 double-mutant lethality phenotypes of the rad3-102 (formerly rem1-2) mutation. Such suppression has previously been been observed with mutant alleles of RAD1 and RAD4. We had hypothesized that the rad3-102 mutation created elevated levels of DNA lesions which could be processed by the products of the RAD1 and RAD4 genes into recombinogenic double-strand breaks requiring the RAD52 product for repair. In this report, we show that the RAD2, RAD7, and RAD10 genes are also necessary for this processing. We discuss our observations of varying levels of mitotic crossingover in Rem- rad double-mutant strains.
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  • 84
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    Current genetics 25 (1994), S. 24-29 
    ISSN: 1432-0983
    Keywords: Yeast ; Yarrowia lipolytica ; Lysine acetyl transferase ; Lysine catabolism
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    Topics: Biology
    Notes: Abstract In the yeastYarrowia lipolytica, theLYC1 locus controls the first step of the lysine degradation pathway which is catalyzed by lysine N-6-acetyl transferase (LAT). This gene was cloned by complementation of thelyc1-100 mutation. Its position in the cloned insert was determined by conversion mapping and by complementation. TheLYC1 gene encodes a 391 amino-acid polypeptide which has no homolog in protein databases. The required upstream region extends over 960 bp. When placed under the control of theGAL10 promoter inSaccharomyces cerevisiae, LYC1 drives the expression of lysine acetyl transferase activity, thus providing strong evidence that it is the structural gene encoding this enzyme.
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  • 85
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    Current genetics 25 (1994), S. 30-33 
    ISSN: 1432-0983
    Keywords: Plasmid exchange ; ras/Ras gene ; Basidiomycete ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was shown by a plasmid exchange procedure that the Ras-encoding cDNA of the basidiomyceteLentinus edodes (namedLeras cDNA) can functionally replace its homolog genes (ScRAS1 andScRAS2) in the yeastSaccharomyces cerevisiae to maintain the viability of an yeast strain containing genetic disruptions of bothRAS genes. The strain replaced by aLeras−cDNA-carrying plasmid, however, grew slower than the strains replaced by aScRAS1− or aScRAS2−carrying plasmid. The intracellular level of cAMP in the strain harboring theLeras−cDNA-carrying plasmid was clearly higher than that of a parental strain which maintains a plasmid carrying theS. cerevisiae cAMP-dependent protein kinase catalytic subunit C1 gene,TPK1, but was lower than that in a strain harboring anScRAS2−carrying plasmid. These results suggest that theLeras cDNA can complement theras1 − ras2− mutation of yeast by virture of the stimulation of adenylate cyclase activity, although the complementation is not as efficient as that obtained by expressing theScRAS2 gene.
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  • 86
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    Current genetics 20 (1991), S. 471-474 
    ISSN: 1432-0983
    Keywords: Yeast ; DNA replication ; Chemical mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Incubation of cdc8 mutants of the yeast Saccharomyces cerevisiae in YPD under permissive conditions, when DNA replication is taking place, prior to transfer to restrictive conditions, strongly stimulates induction of cdc + colonies of ethyl methane sulphonate (EMS)- and methyl methane sulphonate (MMS)-treated yeast strains HB23 (cdc8-1/cdc8-3), HB26 (cdc8-3/cdc8-3) and HB7 (cdc8-1/cdc8-1). After diepoxybutane (DEB) treatment, both the induction of cdc + colonies and their stimulation after incubation in YPD under permissive conditions is low. The results obtained show that stimulation of induction of cdc + colonies under permissive conditions occurs not only after UV-treatment, but also after treatment with such mutagens as EMS and MMS.
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  • 87
    ISSN: 1432-0983
    Keywords: Ribosomes ; Antisuppressor ; Yeast
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    Topics: Biology
    Notes: Summary The yeast antisuppressor mutation, asu9-1 (Liebman and Cavenagh 1980) was found to cause an alteration in the 40S ribosomal subunit. Two-dimensional polyacrylamide gel electrophoresis patterns of the 40S ribosomal proteins from four different strains bearing the asu9-1 mutation all contained the same extra protein spot which was completely absent in five strains which did not carry the asu9 mutation.
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  • 88
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondrial DNA ; Antibiotic resistance mutations
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    Topics: Biology
    Notes: Summary A large proportion of the spontaneous erythromycin resistant mutants isolated from a strain carrying a previously-induced chloramphenicol resistance mutation at cap3 do not map at ery1, the locus most often associated with mitochondrial erythromycin resistance. Most of the new mutations are also nonallelic at spil, spi2, and other known antibiotic resistance loci within the 21S rRNA gene; they are allelic with each other and define the new locus, ery2. Induced second-site erythromycin resistant mutants from the cap r3 strain, as well as spontaneous or induced mutants from strains carrying a cap r 1 mutation, all tend to map at eryl. The cap r3 mutation is apparently necessary for the expression of erythromycin resistance resulting from a second mutation at ery2.
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  • 89
    ISSN: 1432-0983
    Keywords: Yeast ; Thermoconditional DNA repair ; Mutagenesis ; Allelism test
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    Notes: Summary Of two mutant genes (snm1-2 ts and snm2-1 ts) conferring thermoconditional mutagen sensitivity in Saccharomyces cerevisiae one (snm2-1 ts) is shown to be centromere-linked. At the restrictive temperature this allele reduces UV-induced back mutation frequency of the ochre allele hiss-2 but has no influence on forward mutation at the CAN1 locus. Complementation tests and recombination analysis revealed snm2 ts to be allelic with rad5 (rev2).
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  • 90
    ISSN: 1432-0983
    Keywords: Electro-fusion ; Yeast ; Plasmogamy ; Proliferation
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    Topics: Biology
    Notes: Summary Electric field-induced fusion was induced between Saccharomyces cerevisiae protoplasts from the ρ − heterozygous diploid strain 2114 and the respiratory-competent diploid strain 3441, carrying chromosomal markers. Close membrane contact between the cells of the two different strains (ratio 1:1) was achieved by dielectrophoresis in a weak inhomogeneous alternating field (about 1 kV/cm, 2 MHz). Due to dielectrophoresis pearl chains of two or more cells of the two strains are formed between the electrodes. Cell fusion was induced by application of two single square field pulses sufficiently high to induce reversible electrical breakdown in the membrane contact zone between cells within a pearl chain (about 7 to 8 kV/cm field strength and 40 Ms duration). The two subsequent pulses were applied at an interval of about 10 s. Hybrids could be isolated on selection medium in a high yield (compared with conventional fusion techniques). The hybrids were diploid, respiratory-competent and produced prototrophic spores. Thus, the fused hybrids contained only the chromosomal markers of strain 2114 and the cytoplasmic marker for respiratory competence from strain 3441; electro-fusion thus resulted mainly in plasmogamy.
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  • 91
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    Current genetics 6 (1982), S. 93-98 
    ISSN: 1432-0983
    Keywords: Yeast ; Genetic mapping ; Trisomic analysis ; Arginine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary By use of a set of 8 aneuploid strains of the yeast Saccharomyces cerevisiae, carrying from 1 to 5 identified disomic chromosomes, in crosses to a set of haploid strains collectively bearing 11 unmapped genes, the following chromosome assignments were obtained for these unmapped genes: arg80 on XIII;arg3 on X;car2 on XII; cpa1 and tsm8740 on XV; tsm7269 (=rna6) on II; cpa2 on X or XV; arg82 and tsm4572 on III, IV or XVI; car1 and arg81 on II, IV, VI, VII or XVI. Linkage tests between the unmapped genes and markers located on the chromosomes that had been designated as possible carriers by the previous analysis allowed 8 genes to be localized. The remaining three genes, cpa2, car1 and arg81 (located on fragment F8), could not be positioned on any of the chromosomes indicated by the trisomic analysis, in spite of testing for linkage to markers covering most of the known regions of these chromosomes.
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  • 92
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    Current genetics 8 (1984), S. 49-55 
    ISSN: 1432-0983
    Keywords: Protoplast fusion ; Yeast ; Yarrowia lipolytica ; Kluyveromyces lactis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Prototrophic hybrids have been obtained by the fusion of auxotrophic haploid strains of the two yeasts Yarrowia (Saccharomycopsis) lipolytica and Kluyveromyces lactis. The hybrid fusants had a colonial morphology intermediate between that of the two parent strains, were uninucleate, and contained an approximately diploid amount of DNA per cell. The growth rates of all the fusants on a minimal glucose medium were slower than those of the two parents. Two of the fusants studied could utilise a novel range of carbon sources. All of these data suggested that the hybrids contained a diploid nucleus formed by the fusion of the two haploid parental nuclei. However, analytical CsCl density gradient centrifugation demonstrated that the nuclear DNA of the fusants was derived almost entirely from the Y. lipolytica parent. Moreover, an examination of the protein constitution of the fusants by two-dimensional gel electrophoresis showed that their protein patterns were indistinguishable from that of Y. lipolytica. Two possible mechanisms for the formation of a diploid nucleus containing DNA derived almost entirely from one of the haploid parents are discussed.
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  • 93
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    Current genetics 7 (1983), S. 473-480 
    ISSN: 1432-0983
    Keywords: ars sequences ; Yeast ; Chlamydomonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A hybrid plasmid (pLG4) containing pBR325 and the yeast arg4 gene was constructed then used to isolate DNA fragments of Chlamydomonas able to promote high frequency transformation of yeast. Three plasmids containing EcoRI restriction fragments of chloroplast DNA and two plasmids containing Aval fragments of nuclear DNA were shown to support autonomous replication of plasmids in yeast. The three EcoRI fragments correspond to restriction fragments R4, R5 and R11 of native chloroplast DNA. These fragments are clustered in the physical map of chloroplast DNA constructed by Rochaix (1978). All isolated plasmids were shown to transform yeast at high frequency but the yeast transformants were quite unstable mitotically. Potential cloning sites are still available in the new plasmids which could be used as vectors in yeast and possibly in Chlamydomonas itself.
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  • 94
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondrial DNA ; Antibiotic resistance mutations ; Suppressor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Strains that are genotypically sensitive to chloramphenicol and also contain one of the nuclear suppressors of mitochondrial chloramphenicol resistance (Waxman et al. 1979) were constructed. A manganese mutagenesis on such a strain produced chloramphenicol resistant mutants, most of which resulted from mutations in nuclear genes. These mutants may be either dominant or recessive, and they probably do not code for membrane proteins. The few mitochondrial mutants fall into several classes, but all result from mutations in the 21S rRNA gene. The suppressor allele effectively prevents the appearance of the most common group of mitochondrial mutants (those that map at cap1), and thereby enhances the selection of novel mutants in the region.
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  • 95
    ISSN: 1432-1017
    Keywords: Receptor potential ; Intracellular and extracellular calcium concentration ; Intensity dependence ; Adaptation ; Sensitivity control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The light-induced membrane voltage response (receptor potential, ReP) and the absorption change of the intracellularly injected calcium indicator arsenazo III (arsenazo response) were recorded simultaneously in Limulus ventral nerve photoreceptor cells. A double pulse technique was applied for stimulation. After pressure injection of the indicator into the cell absorption changes were measured at 646 nm to obtain a measure of the changes of the intracellular calcium ion concentration. 1. The size of the arsenazo response increases with increasing intensity of the light stimulus. The intensity dependence of the size of the arsenazo response δAmax shows almost no correlate with the peak amplitude of the ReP, but correlates rather well with the time integral of the ReP. 2. Decreasing light adaptation (caused by prolongation of the repetition time of the pulse pairs) leads to an increase in size of the arsenazo response. Also here δAmax correlates better with the time integral of the ReP than with its peak amplitude. 3. Lowering the calcium concentration in the superfusate (from 10 mmol/l to ca. 40 Μmol/l) causes after ca. 10 min a drastical diminution of the arsenazo response to values below the noise level, and a less marked reduction in size of the ReP. The falling phase of the ReP is slower. After return to normal calcium concentration the arsenazo response recovers partly in ca. 50 min, while the ReP recovers faster. The results show two opposite correlations between ReP and arsenazo response: Increase in size and duration of the ReP causes a greater transient increase of the intracellular calcium ion concentration. This in turn tends to reduce and shorten the ReP. Which effect dominates obviously depends on the conditions of the experiment: when the calcium concentration in the superfusate is reduced to ca. 40 Μmol/l a slow decrease of the ReP is accompanied by a small increase of the intracellular calcium ion concentration.
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    European biophysics journal 7 (1981), S. 205-208 
    ISSN: 1432-1017
    Keywords: Grasshopper ; Electroretinogram ; Adaptation ; Spectral sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The grasshopper ERG displays a rapid recovery of responsivity following the onset of a background light. Although observed earlier in skate and frog, this phenomenon has not previously been seen in an invertebrate. Furthermore, a period of hyperresponsivity exists in early dark adaptation and resembles that found in skate and frog. Thus, recovery in the light and hyperresponsivity in the dark seem to be corollaries of each other. Finally, spectral sensitivity of the ERG is determined and two peaks are found: one at 510 nm and the other at 360 nm. The former appears to be a rhodopsin-mediated sensitivity but the latter does not and they are not clearly separated by chromatic adaptation.
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  • 97
    ISSN: 1432-1017
    Keywords: Photoreceptor ; Visual pigment ; Adaptation ; Facilitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A conditioning light can cause a decrease (adaptation) or an increase (facilitation) in the sensitivity of barnacle photoreceptors, as measured by the amplitude of the late receptor potential (LRP). We show that a net transfer of visual pigment from the rhodopsin (R) to the metarhodopsin (M) state induces a large facilitation whereas the reverse transfer results in a much smaller facilitation or even an adaptation. These effects were not due to the response to the conditioning light but to the pigment reactions. When the conditioning light did not alter the pigment population (i.e., M → M, R → R) it was followed by an intermediate degree of facilitation. These conclusions are correct for cells which have relatively low sensitivity. In sensitive cells, all pigment transitions produce adaptation. LRP facilitation and the prolonged depolarizing afterpotential (PDA) show several common characteristics with respect to pigment transitions: 1.Their magnitude increases with the amount of pigment transferred from R to M. 2. Both are depressed by the M → R transition. 3. Their production is impeded by the M → R transition. 4. The PDA itself is facilitated by the R → M transition and this facilitation decays with a time course comparable to that of LRP facilitation. These results suggest that there may be an underlying process common to LRP facilitation and PDA.
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  • 98
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    European biophysics journal 8 (1982), S. 173-187 
    ISSN: 1432-1017
    Keywords: Leech photoreceptors ; Extracellular calcium ; Excitation ; Adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Extracellular recordings from the vacoule of photoreceptor cells of Hirudo medicinalis L. were performed using microelectrodes. The cells were adapted by white light flashes given at constant intervals (20 s). Response height versus relative intensity curves obtained from the same cell in physiological saline (PS) and in bathing solutions of either a) lowered calcium contents (2 ΜM/1 or less) or b) raised calcium contents (15 mM/1) were compared. The cells' adaptation state in PS was operationally defined by the ratio Q=h A /h S where h A is the response height evoked by the adapting flashes, and h S is the corresponding saturation response height. Sensitivity changes were measured by the half saturation intensity shift. Lowering extracellular calcium resulted in: 1. The response height increased and the shape of the response became more rounded and prolonged. 2. The total resistance between the vacuole and outside decreased from 8.2±1.4 MΩ (n=6) in PS to 4.6±0.4 MΩ (n=5). The resistance was independent of the cells' adaptation state. 3. A change of the cells' sensitivity occured either in direction to light adaptation or in direction to dark adaptation. It depended functionally on the ratio Q: a) if Q was less or equal to about 0.6 the cells' sensitivity increased. b) if Q was greater than 0.6 the cells' sensitivity diminished. Raising extracellular calcium decreased the sensitivity of all cells tested independent of their adaptation states in PS. The results can be interpreted under the assumptions that 1. the sensitivity of leech photoreceptor cells is inversely proportional to the intracellular free calcium concentration and Z. intracellular calcium can interact with extracellular calcium in relatively dark adapted cells whereas in relatively light adapted cells the raise of intracellular free calcium is mainly effected by a release from intracellular stores. It is assumed that a Q value of about 0.6 separates relatively light adapted cells from relatively dark adapted cells.
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  • 99
    ISSN: 1432-0983
    Keywords: Petite mutation ; NUC2 nuclease ; Yeast ; RAD52 ; Ethidium bromide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Defects in the RAD52 gene of the yeast Saccharomyces cerevisiae reduce the levels of the NUC2 endo-exonuclease by approximately 90% compared to the levels in wild-type strains. To examine the potential role of this nuclease in the induction of mitochondrial ‘petite’ mutations, congenic RAD52 and rad52-1 haploids were subjected to treatment with ethidium bromide, a well-known inducer of these mutations. The rad52 strain showed a much higher resistance to ethidium bromide-induced petite formation than the corresponding wild-type strain. Two approaches were taken to confirm that this finding reflected the nuclease deficiency, and not some other effect attributable to the rad52-1 mutation. First, a multicopy plasmid (YEp213-10) carrying NUC2 was transformed into a RAD52 strain. This resulted in an increased fraction of spontaneous petite mutations relative to that seen for the same strain without the plasmid and sensitized the strain carrying the plasmid to peptite induction by ethidium bromide treatment. Second, a strain having a nuc2 allele that encodes a temperaturesensitive nuclease was treated with ethidium bromide at the restrictive and permissive temperatures. Petite induction was reduced under restrictive conditions. Enzyme assays revealed that the RAD52 (YEp213-10) strain had the highest level of antibody-precipitable NUC2 endo-exonuclease whereas the nuc2 and rad52 mutants had the lowest levels. Furthermore, addition of ethidium bromide to the reaction mixture stimulated the activity of the nuclease on double-stranded DNA. Peptite induction by antifolate-mediated thymine nucleotide depletion was also inhibited by inactivation of RAD52 indicating that the effect of reduced NUC2 endo-exonuclease was not restricted to ethidium bromide treatment. Taken collectively, these results indicate that the NUC2 gene product functions in the production of mitochondrial petite mutations.
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  • 100
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Aminoacyl-tRNA synthetase ; RNA splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial leucyl-tRNA synthetase (mLRS) of Saccharomyces cerevisiae is involved in both mitochondrial protein synthesis and pre-mRNA splicing. We have created mutations in the regions HIGH, GWD and KMSKS, which are involved in ATP-, amino acid-and tRNA-binding respectively, and which have been conserved in the evolution of group I tRNA synthetases. The mutants GRD and NMSKS have no discernible phenotype. The mutants AWD and ARD act as null alleles and lead to the production of 100% cytoplasmic petites. The mutants HIGN, NIGH and KMSNS are unable to grown on glycerol even in the presence of an intronless mitochondrial genome and accumulate petites to a greater extent than the wild-type but less than 40%. Experiments with an imported bI4 maturase indicate that the lesion in these mutations primarily affects the synthetase and not the splicing functions.
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