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Trevor A. Thorpe - One of the best experts on this subject based on the ideXlab platform.

  • Ascorbic acid changes the pattern of purine metabolism during germination of white spruce somatic embryos
    Tree physiology, 2001
    Co-Authors: Claudio Stasolla, Hiroshi Ashihara, Natalia Loukanina, Edward C. Yeung, Trevor A. Thorpe
    Abstract:

    It has previously been shown that exogenous applications of ascorbic acid (AA) increase the conversion frequency of somatic embryos of white spruce (Picea glauca (Moench) Voss). To determine whether ascorbic acid alters purine metabolism during the early phases of embryo germination, the relative rates of purine Salvage and degradation were investigated by following the metabolic fates of exogenously applied [8-14C]adenine, [8-14C]adenosine, and [8-14C]inosine, and the activities of several key enzymes. We demonstrated that both the Salvage and the degradation pathways operate during germination. Specifically, adenine and adenosine were mainly Salvaged to nucleotides and nucleic acids, whereas an appreciable amount of inosine was degraded to CO2 and ureides. Comparisons of purine metabolism between control and AA-treated embryos showed that exogenous applications of ascorbic acid enhanced the ability of the embryos to take up adenine and adenosine throughout the germination period. Furthermore, the higher enzymatic activities of adenosine kinase and adenine phosphoribosyltransferase were responsible for the larger proportion of adenine and adenosine being Salvaged in AA-treated embryos compared with control embryos. Thus, there was a positive correlation between the ability to anabolize purine precursors and successful embryo conversion.

  • purine and pyrimidine metabolism during the partial drying treatment of white spruce picea glauca somatic embryos
    Physiologia Plantarum, 2001
    Co-Authors: Claudio Stasolla, Hiroshi Ashihara, Natalia Loukanina, Edward C. Yeung, Trevor A. Thorpe
    Abstract:

    The imposition of a partial drying treatment (PDT) on mature white spruce somatic embryos is a necessary step for successful germination and embryo conversion into plantlets. Purine and pyrimidine metabolism was investigated during the PDT of white spruce somatic embryos by following the metabolic fate of 14 C-labeled adenine, adenosine, and inosine, as purine intermediates, and orotic acid, uridine, and uracil, as pyrimidine intermediates, as well as examining the activities of key enzymes. Both the Salvage and the degradation pathways of purines were operative in partially dried embryos. Adenine and adenosine were extensively Salvaged by the enzymes adenine phosphoribosyltransferase and adenosine kinase, respectively. The activity of the former enzyme increased during the PDT. In both mature and partially dried embryos, a large proportion of inosine was recovered as degradation products. The de novo pathway of pyrimidine nucleotide biosynthesis, estimated by the incorporation of orotic acid into the nucleotides and nucleic acids, was high at the end of the maturation period and declined during the PDT. Uridine was the main substrate for the pyrimidine Salvage pathway, since a large proportion of uracil was recovered as degradation products, i.e. CO 2 and β-ureidopropionic acid in both mature and partially dried embryos. Uridine was mainly Salvaged by uridine kinase, whose activity was found to increase during the PDT. Taken together these results indicate that the PDT might be required for increasing the activity of adenine and uridine Salvage enzymes, which could contribute to the enlargement of the nucleotide pool required at the onset of germination.

Claudio Stasolla - One of the best experts on this subject based on the ideXlab platform.

  • Purine Salvage in plants.
    Phytochemistry, 2018
    Co-Authors: Hiroshi Ashihara, Claudio Stasolla, Tatsuhito Fujimura, Alan Crozier
    Abstract:

    Abstract Purine bases and nucleosides are produced by turnover of nucleotides and nucleic acids as well as from some cellular metabolic pathways. Adenosine released from the S-adenosyl-L-methionine cycle is linked to many methyltransferase reactions, such as the biosynthesis of caffeine and glycine betaine. Adenine is produced by the methionine cycles, which is related to other biosynthesis pathways, such those for the production of ethylene, nicotianamine and polyamines. These purine compounds are recycled for nucleotide biosynthesis by so-called “Salvage pathways”. However, the Salvage pathways are not merely supplementary routes for nucleotide biosynthesis, but have essential functions in many plant processes. In plants, the major Salvage enzymes are adenine phosphoribosyltransferase (EC 2.4.2.7) and adenosine kinase (EC 2.7.1.20). AMP produced by these enzymes is converted to ATP and utilised as an energy source as well as for nucleic acid synthesis. Hypoxanthine, guanine, inosine and guanosine are Salvaged to IMP and GMP by hypoxanthine/guanine phosphoribosyltransferase (EC 2.4.2.8) and inosine/guanosine kinase (EC 2.7.1.73). In contrast to de novo purine nucleotide biosynthesis, synthesis by the Salvage pathways is extremely favourable, energetically, for cells. In addition, operation of the Salvage pathway reduces the intracellular levels of purine bases and nucleosides which inhibit other metabolic reactions. The purine Salvage enzymes also catalyse the respective formation of cytokinin ribotides, from cytokinin bases, and cytokinin ribosides. Since cytokinin bases are the active form of cytokinin hormones, these enzymes act to maintain homeostasis of cellular cytokinin bioactivity. This article summarises current knowledge of purine Salvage pathways and their possible function in plants and purine Salvage activities associated with various physiological phenomena are reviewed.

  • Ascorbic acid changes the pattern of purine metabolism during germination of white spruce somatic embryos
    Tree physiology, 2001
    Co-Authors: Claudio Stasolla, Hiroshi Ashihara, Natalia Loukanina, Edward C. Yeung, Trevor A. Thorpe
    Abstract:

    It has previously been shown that exogenous applications of ascorbic acid (AA) increase the conversion frequency of somatic embryos of white spruce (Picea glauca (Moench) Voss). To determine whether ascorbic acid alters purine metabolism during the early phases of embryo germination, the relative rates of purine Salvage and degradation were investigated by following the metabolic fates of exogenously applied [8-14C]adenine, [8-14C]adenosine, and [8-14C]inosine, and the activities of several key enzymes. We demonstrated that both the Salvage and the degradation pathways operate during germination. Specifically, adenine and adenosine were mainly Salvaged to nucleotides and nucleic acids, whereas an appreciable amount of inosine was degraded to CO2 and ureides. Comparisons of purine metabolism between control and AA-treated embryos showed that exogenous applications of ascorbic acid enhanced the ability of the embryos to take up adenine and adenosine throughout the germination period. Furthermore, the higher enzymatic activities of adenosine kinase and adenine phosphoribosyltransferase were responsible for the larger proportion of adenine and adenosine being Salvaged in AA-treated embryos compared with control embryos. Thus, there was a positive correlation between the ability to anabolize purine precursors and successful embryo conversion.

  • purine and pyrimidine metabolism during the partial drying treatment of white spruce picea glauca somatic embryos
    Physiologia Plantarum, 2001
    Co-Authors: Claudio Stasolla, Hiroshi Ashihara, Natalia Loukanina, Edward C. Yeung, Trevor A. Thorpe
    Abstract:

    The imposition of a partial drying treatment (PDT) on mature white spruce somatic embryos is a necessary step for successful germination and embryo conversion into plantlets. Purine and pyrimidine metabolism was investigated during the PDT of white spruce somatic embryos by following the metabolic fate of 14 C-labeled adenine, adenosine, and inosine, as purine intermediates, and orotic acid, uridine, and uracil, as pyrimidine intermediates, as well as examining the activities of key enzymes. Both the Salvage and the degradation pathways of purines were operative in partially dried embryos. Adenine and adenosine were extensively Salvaged by the enzymes adenine phosphoribosyltransferase and adenosine kinase, respectively. The activity of the former enzyme increased during the PDT. In both mature and partially dried embryos, a large proportion of inosine was recovered as degradation products. The de novo pathway of pyrimidine nucleotide biosynthesis, estimated by the incorporation of orotic acid into the nucleotides and nucleic acids, was high at the end of the maturation period and declined during the PDT. Uridine was the main substrate for the pyrimidine Salvage pathway, since a large proportion of uracil was recovered as degradation products, i.e. CO 2 and β-ureidopropionic acid in both mature and partially dried embryos. Uridine was mainly Salvaged by uridine kinase, whose activity was found to increase during the PDT. Taken together these results indicate that the PDT might be required for increasing the activity of adenine and uridine Salvage enzymes, which could contribute to the enlargement of the nucleotide pool required at the onset of germination.

Chris J. Peterson - One of the best experts on this subject based on the ideXlab platform.

  • Woody Species Composition, Diversity, and Recovery Six Years after Wind Disturbance and Salvage Logging of a Southern Appalachian Forest
    MDPI AG, 2019
    Co-Authors: Callie A. Oldfield, Chris J. Peterson
    Abstract:

    Salvage logging after wind disturbance of a mixed conifer-hardwood forest results in sapling compositional changes but no changes to species diversity six years post-disturbance. Several conceptual frameworks allow for predictions of the effects of forest disturbances on composition, but fewer yield predictions of species diversity. Following compound disturbance, tree species diversity and composition is predicted to shift to early successional species. Because of the greater cumulative severity, diversity should be lower in areas experiencing windthrow + Salvage logging than in similar sites experiencing windthrow alone. We examined the effects of wind disturbance and Salvage logging on diversity parameters over six years. We hypothesized that the effects of Salvage logging on diversity would be short-lived, but that species composition would be altered six years post-disturbance. Sampling plots were established in a mixed-hardwood forest in north Georgia, USA, after a 2011 EF3 tornado and surveyed in 2012 and 2017. Nineteen 20 × 20 m plots were surveyed (10 unSalvaged, 9 Salvaged) for parameters including Shannon diversity, species richness, and composition. Ordinations were used to visualize tree and sapling species composition in Salvage logged plots. We found that there was no significant difference in Shannon diversity between Salvaged and unSalvaged plots before disturbance, <1 post-disturbance, or 6 years post-disturbance. The disturbances altered the tree and sapling species compositions, with Salvaged plots having more mid-successional saplings but few true pioneer species. There appears to be an emerging pattern in the wind disturbance + salvaging literature which our study supports⁻ salvaging does not affect tree species diversity but shifts species composition over time

  • Effects of post-windthrow Salvage logging on microsites, plant composition and regeneration
    Applied Vegetation Science, 2013
    Co-Authors: Kaysandra Waldron, Jean Claude Ruel, Sylvie Gauthier, Louis De Grandpré, Chris J. Peterson
    Abstract:

    AbstractQuestions: How does windthrow influence plant diversity and composition aswell as regeneration and microsite characteristics? What are the consequencesofpost-windthrowSalvageloggingonthesekeyattributes?Location:Easternblackspruce–mossforest,Quebec,Canada.Methods:Atotalof92plotsweresampled,eachwitharadiusof11.28 m;49ofthese plots were Salvaged while 43 were unSalvaged. Regeneration density,plantdiversityandseedbedswerecharacterized.Wetestedtheeffectofmicroto-pography and windthrow severity on species richness and Shannon diversityindex for Salvaged and unSalvaged windthrows using a mixed model. Partialredundancyanalysis(RDA)determinedwhichenvironmentalandstandcharac-teristicsweremostimportantinexplainingdifferencesinplantspeciesandforestfloortypesamongthetreatments.Theeffectsof treatments(Salvaged and unsal-vagedwindthrows),microtopographyattributes,windthrowseverityandregen-eration species on seedling and sapling abundance were tested using a linearmixedmodel.Results:Salvagedwindthrow,withalargeproportionofskidtrails,deadmossesand Sphagnum, had a lower degree of seedbed heterogeneity. Also, some under-storey species present in the unSalvaged ecosystem were absent from the sal-vaged windthrow. Sphagnum and other moss species were clearly associatedwith the unSalvaged treatment. White birches were positively associated withmoundmicrotopographyintheunSalvagedwindthrow.Conclusion: From an ecosystem-based forest management perspective, naturalpost-windthrow understorey conditions and microsite heterogeneity can be inpart maintained in Salvaged cut blocks by incorporating retention patches thatinclude downed and standing dead wood and living trees of diverse sizes. ThesestepsshouldfavourplantregenerationandaugmentdiversityforSalvageloggingafterwinddisturbance.IntroductionIn many parts of the world, major disturbance episodesoften lead to Salvage logging (often called sanitary loggingin Europe; Lindenmayer et al. 2004, 2008). Functionally,Salvage logging can be distinguished from other harvestoperations in that, with salvaging after natural distur-bance, the ecosystem is subjected to two sequential distur-bances within a short period (Lindenmayer et al. 2008).Peterson & Leach (2008) suggest that multiple disturbanceimpacts need to be understood on the basis of cumulativeseverity. Indeed, recent conceptual advances (e.g. the cuspmodel of Frelich & Reich 1999; the three-axis model ofRoberts 2004, 2007) have begun to address the potentialfor multiple disturbances to change the trajectory of com-munity development, sometimes in undesirable directions(Paine et al. 1998). Because of the potential for thecombined severity of natural disturbance followed bysalvaging to yield unwanted ‘ecological surprises’ (Paineet al. 1998), guidelines are needed for the planning of

  • Salvage logging after windthrow alters microsite diversity abundance and environment but not vegetation
    Forestry, 2008
    Co-Authors: Chris J. Peterson, Andrea D Leach
    Abstract:

    Summary An increasing number of researchers propose that disturbance effects in forests are mediated through ‘ legacies ’ , which are organisms or organically derived structures that persist after a disturbance. Much controversy currently surrounds the potential impact of post-disturbance Salvage logging, in part, because of the potential for such actions to alter post-disturbance legacies and thus forest regeneration. Microsites (e.g. downed tree crowns, boles, stumps, treefall pits and mounds) created by natural disturbances are a subset of the broader concept of legacies, but the effect of windthrow + Salvage logging on microsites and their environment and vegetation has not been previously examined. In a wind-damaged forest in western Tennessee, USA, we documented microsite diversity and abundance, environmental conditions, and initial vegetation regeneration in Salvaged and unSalvaged areas. We found that Salvaged areas had signifi cantly greater variety of microsites, altered microsite abundance, higher soil temperature and greater canopy openness relative to unSalvaged areas. However, 2 years after the storm, herbaceous cover and species richness and tree seedling density and species richness did not differ between Salvaged and unSalvaged areas. Soil moisture also was unaffected by salvaging. In contrast, environmental conditions and vegetation characteristics differed signifi cantly among microsite types, with treefall mounds being warmer and drier than other microsites. This intermediateseverity wind disturbance, followed by moderate intensity of salvaging, created microsites that differed in environment and vegetation, and although the salvaging altered microsite diversity, abundances and conditions, the initial vegetation did not show detrimental effects of the Salvage operations. We suggest that primary determinants of the consequences of salvaging after natural disturbance are the severity of the natural disturbance, and intensity of Salvage operations. Detrimental effects of salvaging may accrue only if some combined severity threshold is exceeded.

Hiroshi Ashihara - One of the best experts on this subject based on the ideXlab platform.

  • Purine Salvage in plants.
    Phytochemistry, 2018
    Co-Authors: Hiroshi Ashihara, Claudio Stasolla, Tatsuhito Fujimura, Alan Crozier
    Abstract:

    Abstract Purine bases and nucleosides are produced by turnover of nucleotides and nucleic acids as well as from some cellular metabolic pathways. Adenosine released from the S-adenosyl-L-methionine cycle is linked to many methyltransferase reactions, such as the biosynthesis of caffeine and glycine betaine. Adenine is produced by the methionine cycles, which is related to other biosynthesis pathways, such those for the production of ethylene, nicotianamine and polyamines. These purine compounds are recycled for nucleotide biosynthesis by so-called “Salvage pathways”. However, the Salvage pathways are not merely supplementary routes for nucleotide biosynthesis, but have essential functions in many plant processes. In plants, the major Salvage enzymes are adenine phosphoribosyltransferase (EC 2.4.2.7) and adenosine kinase (EC 2.7.1.20). AMP produced by these enzymes is converted to ATP and utilised as an energy source as well as for nucleic acid synthesis. Hypoxanthine, guanine, inosine and guanosine are Salvaged to IMP and GMP by hypoxanthine/guanine phosphoribosyltransferase (EC 2.4.2.8) and inosine/guanosine kinase (EC 2.7.1.73). In contrast to de novo purine nucleotide biosynthesis, synthesis by the Salvage pathways is extremely favourable, energetically, for cells. In addition, operation of the Salvage pathway reduces the intracellular levels of purine bases and nucleosides which inhibit other metabolic reactions. The purine Salvage enzymes also catalyse the respective formation of cytokinin ribotides, from cytokinin bases, and cytokinin ribosides. Since cytokinin bases are the active form of cytokinin hormones, these enzymes act to maintain homeostasis of cellular cytokinin bioactivity. This article summarises current knowledge of purine Salvage pathways and their possible function in plants and purine Salvage activities associated with various physiological phenomena are reviewed.

  • Profiles of purine biosynthesis, Salvage and degradation in disks of potato (Solanum tuberosum L.) tubers
    Planta, 2006
    Co-Authors: Riko Katahira, Hiroshi Ashihara
    Abstract:

    To find general metabolic profiles of purine ribo- and deoxyribonucleotides in potato ( Solanum tuberosum L.) plants, we looked at the in situ metabolic fate of various ^14C-labelled precursors in disks from growing potato tubers. The activities of key enzymes in potato tuber extracts were also studied. Of the precursors for the intermediates in de novo purine biosynthesis, [^14C]formate, [2-^14C]glycine and [2-^14C]5-aminoimidazole-4-carboxyamide ribonucleoside were metabolised to purine nucleotides and were incorporated into nucleic acids. The rates of uptake of purine ribo- and deoxyribonucleosides by the disks were in the following order: deoxyadenosine > adenosine > adenine > guanine > guanosine > deoxyguanosine > inosine > hypoxanthine > xanthine > xanthosine. The purine ribonucleosides, adenosine and guanosine, were Salvaged exclusively to nucleotides, by adenosine kinase (EC 2.7.1.20) and inosine/guanosine kinase (EC 2.7.1.73) and non-specific nucleoside phosphotransferase (EC 2.7.1.77). Inosine was also Salvaged by inosine/guanosine kinase, but to a lesser extent. In contrast, no xanthosine was Salvaged. Deoxyadenosine and deoxyguanosine, was efficiently Salvaged by deoxyadenosine kinase (EC 2.7.1.76) and deoxyguanosine kinase (EC 2.7.1.113) and/or non-specific nucleoside phosphotransferase (EC 2.7.1.77). Of the purine bases, adenine, guanine and hypoxanthine but not xanthine were Salvaged for nucleotide synthesis. Since purine nucleoside phosphorylase (EC 2.4.2.1) activity was not detected, adenine phosphoribosyltransferase (EC 2.4.2.7) and hypoxanthine/guanine phosphoribosyltransferase (EC 2.4.2.8) seem to play the major role in Salvage of adenine, guanine and hypoxanthine. Xanthine was catabolised by the oxidative purine degradation pathway via allantoin. Activity of the purine-metabolising enzymes observed in other organisms, such as purine nucleoside phosphorylase (EC 2.4.2.1), xanthine phosphoribosyltransferase (EC 2.4.2.22), adenine deaminase (EC 3.5.4.2), adenosine deaminase (EC 3.5.4.4) and guanine deaminase (EC 3.5.4.3), were not detected in potato tuber extracts. These results suggest that the major catabolic pathways of adenine and guanine nucleotides are AMP → IMP → inosine → hypoxanthine → xanthine and GMP → guanosine → xanthosine → xanthine pathways, respectively. Catabolites before xanthosine and xanthine can be utilised in Salvage pathways for nucleotide biosynthesis.

  • Ascorbic acid changes the pattern of purine metabolism during germination of white spruce somatic embryos
    Tree physiology, 2001
    Co-Authors: Claudio Stasolla, Hiroshi Ashihara, Natalia Loukanina, Edward C. Yeung, Trevor A. Thorpe
    Abstract:

    It has previously been shown that exogenous applications of ascorbic acid (AA) increase the conversion frequency of somatic embryos of white spruce (Picea glauca (Moench) Voss). To determine whether ascorbic acid alters purine metabolism during the early phases of embryo germination, the relative rates of purine Salvage and degradation were investigated by following the metabolic fates of exogenously applied [8-14C]adenine, [8-14C]adenosine, and [8-14C]inosine, and the activities of several key enzymes. We demonstrated that both the Salvage and the degradation pathways operate during germination. Specifically, adenine and adenosine were mainly Salvaged to nucleotides and nucleic acids, whereas an appreciable amount of inosine was degraded to CO2 and ureides. Comparisons of purine metabolism between control and AA-treated embryos showed that exogenous applications of ascorbic acid enhanced the ability of the embryos to take up adenine and adenosine throughout the germination period. Furthermore, the higher enzymatic activities of adenosine kinase and adenine phosphoribosyltransferase were responsible for the larger proportion of adenine and adenosine being Salvaged in AA-treated embryos compared with control embryos. Thus, there was a positive correlation between the ability to anabolize purine precursors and successful embryo conversion.

  • purine and pyrimidine metabolism during the partial drying treatment of white spruce picea glauca somatic embryos
    Physiologia Plantarum, 2001
    Co-Authors: Claudio Stasolla, Hiroshi Ashihara, Natalia Loukanina, Edward C. Yeung, Trevor A. Thorpe
    Abstract:

    The imposition of a partial drying treatment (PDT) on mature white spruce somatic embryos is a necessary step for successful germination and embryo conversion into plantlets. Purine and pyrimidine metabolism was investigated during the PDT of white spruce somatic embryos by following the metabolic fate of 14 C-labeled adenine, adenosine, and inosine, as purine intermediates, and orotic acid, uridine, and uracil, as pyrimidine intermediates, as well as examining the activities of key enzymes. Both the Salvage and the degradation pathways of purines were operative in partially dried embryos. Adenine and adenosine were extensively Salvaged by the enzymes adenine phosphoribosyltransferase and adenosine kinase, respectively. The activity of the former enzyme increased during the PDT. In both mature and partially dried embryos, a large proportion of inosine was recovered as degradation products. The de novo pathway of pyrimidine nucleotide biosynthesis, estimated by the incorporation of orotic acid into the nucleotides and nucleic acids, was high at the end of the maturation period and declined during the PDT. Uridine was the main substrate for the pyrimidine Salvage pathway, since a large proportion of uracil was recovered as degradation products, i.e. CO 2 and β-ureidopropionic acid in both mature and partially dried embryos. Uridine was mainly Salvaged by uridine kinase, whose activity was found to increase during the PDT. Taken together these results indicate that the PDT might be required for increasing the activity of adenine and uridine Salvage enzymes, which could contribute to the enlargement of the nucleotide pool required at the onset of germination.

Kelley Bose - One of the best experts on this subject based on the ideXlab platform.

  • Adult testicular torsion.
    The Journal of urology, 2002
    Co-Authors: James M. Cummings, John A. Boullier, Davinder Sekhon, Kelley Bose
    Abstract:

    Purpose: Testicular torsion in adulthood is thought to be relatively unusual. We compared a series of men 21 years old or older with testicular torsion with a concurrent series of younger patients with torsion. Materials and Methods: We reviewed the medical records of patients admitted with testicular torsion in a 9-year period to hospitals affiliated with our institution. Data included patient demographics, history, physical findings, radiographic results if any, operative findings and outcome (testicular Salvage versus loss). Results: The charts of 48 patients were evaluated. Excluded from study was a neonate with torsion and 3 males who underwent delayed surgery for presumed missed torsion. Of the remaining 44 patients we compared 17 who were 21 years old or older (range 21 to 34) with 27 younger than 21 (range 8 to 20). The Salvage rate differed in the 2 age groups with 70.3% of testes Salvaged in the younger group versus only 41% in the older group. A factor affecting Salvage in each group was time to presentation. In the older age group patients in whom the testis was lost had a significantly higher mean delay in presentation than those in whom it was Salvaged (102 versus 11 hours). A similar pattern was noted in the younger group with a mean time to presentation of 108 and 6.5 hours in those with testicular loss and Salvage, respectively. Mean time between presentation and operation was 7.1 hours in the older and 4.8 in the younger group, which was not statistically different. A significant difference was noted in the degree of spermatic cord twisting. The cord was twisted a mean of 585 degrees in the adults versus 431 in the younger group. Conclusions: Testicular torsion in adults was more common in our series than expected. Salvage of the affected testis was better in younger patients, presumably due to less twisting of the cord.