Effects of post-tetanic potentiation induced by whole-body electrostimulation and post-activation potentiation on maximum isometric strength.

It is currently unknown the most effective potentiation protocol to increase maximum strength. Hence, we investigated the separated and combined effects of post-tetanic potentiation (PTP) induced by whole-body electrostimulation (WB-EMS) and post-activation potentiation (PAP) induced by voluntary maximum isometric contractions on maximum isometric strength. Ten trained males were randomly evaluated on four occasions. In session A, maximum isometric strength (split squat) was measured in minutes 1, 4, and 8. In session B, the measurements were taken in minutes 2, 6, and 10. In session C, a WB-EMS protocol was applied to elicit PTP and the measurements were performed in minutes 1, 4, and 8. In session D, the same WB-EMS protocol was applied and the measurements were taken in minutes 2, 6, and 10. No significant differences in maximum isometric strength were observed between: (i) the control and WB-EMS in minutes 1 vs. 1 and 2 vs. 2; (ii) the control and PAP in minutes 1 vs. 4, 1 vs. 8, 2 vs. 6, and 2 vs. 10; and (iii) the PAP and WB-EMS plus PAP in minutes 4 vs. 4, 8 vs. 8, 6 vs. 6, and 10 vs. 10. In contrast, the WB-EMS plus PAP revealed a significant increase of 54% (~450 N) compared to the WB-EMS in minutes 4 and 8 compared to the minute 1 (p < 0.001), but not between minutes 2 vs. 6 and 2 vs. 10. The present results showed that PTP induced by WB-EMS in isolation or combined with PAP induced by voluntary maximum isometric contractions did not produce a significant increase in maximum isometric strength compared to the control and PAP alone, respectively.

Effectiveness of a low-fat yoghurt supplemented with rooster comb extract on muscle strength in adults with mild knee pain and mechanisms of action on muscle regeneration.

PURPOSE: To determine the effects of the intake of low-fat yoghurt supplemented with rooster comb extract (RCE) on muscle strength. METHODS AND RESULTS: 148 subjects, with mild knee pain, participated in a randomized, placebo-controlled, double-blind, and parallel study. Muscle strength, knee effusion, and pain perception were measured. C2C12 myoblasts were used to elucidate the mechanisms of action involved. RCE improved total work and mean power in men, and also peak torque in extension by 10%. RCE reduced synovial effusion by 11.8% and pain perception by 24.6%. Both RCE and HA increased myoblast proliferation by 29%, while RCE reduced myoblast differentiation by 36.2%, suggesting a beneficial role of RCE in muscle regeneration. CONCLUSIONS: Low-fat yoghurt supplemented with RCE improved muscle strength. This effect is partially explained by muscle regeneration enhancement, reduced synovial effusion, and reduced pain perception, which could exert a beneficial clinical impact on men affected by mild knee pain.

Evaluación nutricional de la papa de aire (Dioscorea bulbifera L) cultivada en panamá / Nutritional evaluation of air potato (Dioscorea bulbifera L) grown in panamá

El objetivo del presente estudio fue el de conocer la composición nutricional de los tubérculos de la papa de aire (Dioscorea bulbifera L.) especie subutilizada en la agricultura campesina panameña. Se seleccionaron 18 muestras obtenidas de parcelas de prueba ubicadas en comunidades campesinas del distrito de Donoso, provincia de Colón, en Panamá, durante los años 2012 y 2013. A las muestras seleccionadas se les determinó humedad, proteínas, azúcares, almidón, lípidos, cenizas y contenido energético. En el segundo año se incluyó el análisis de vitamina C, compuestos fenólicos y actividad antioxidante. No se encontraron diferencias significativas de los valores entre comunidades, tipo de parcela y año de cultivo, lo cual evidencia una alta estabilidad de estos valores nutricionales en las condiciones del trópico muy húmedo de Panamá. Los resultados obtenidos presentan un contenido nutricional similar al de otros tubérculos utilizados en la dieta campesina de Panamá. Los valores de actividad antioxidante y contenido de compuestos fenólicos encontrados le confieren características de alimento funcional(AU)

The goal of this study was to determine the nutritional composition of air potato (Dioscorea bulbifera L.) tubers, underutilized specie in the Panamanian peasant agriculture. The samples were obtained from test plots located in rural communities in the district of Donoso, Province of Colon in Panama, during the years 2012 and 2013. Contents of moisture, protein, sugars, starch, lipids, ashes and energetic were determined to the 18 selected samples. In the second year were included analysis of vitamin C, phenolic compounds and antioxidant activity. No significant differences of the values between communities, type of land and crop year were found, which suggest high stability of these nutritional values of air potato, in the very humid tropics conditions of Panama. The results show that the air potato tubers have a nutritional value similar to other tubers used in the peasant diet of Panama. The levels of antioxidant activity and phenolic content found, give D. bulbifera characteristics as a functional food(AU)

ESTUDIO ETNOBOTÁNICO DE LA PAPA DE AIRE (Dioscorea bulbifera L) EN DONOSO (COLÓN, REPÚBLICA DE PANAMÁ) / ETHNO-BOTANICAL STUDY OF AIR POTATO (Dioscorea bulbifera L) IN DONOSO (COLÓN, REPUBLIC OF PANAMÁ)

Con el objetivo de conocer y rescatar la historia, usos y manejo dado a Dioscorea bulbifera L. por las comunidades campesinas del distrito de Donoso (provincia de Colón, Panamá) se llevó a cabo un estudio etnobotánico en el primer semestre de 2012. El mismo se desarrolló a partir de grupos focales, recorridos de campo y entrevistas semiestructuradas a personajes clave (ancianos, curanderos y personas que cultivan D. bulbifera). Se realizaron cinco grupos focales y 11 entrevistas semiestructuradas, abordando aspectos relativos a historia, nombres, manejo tradicional, usos y formas de consumo de la papa de aire en la región. Como resultados destacados se tiene que D. bulbifera es una especie de muy vieja presencia en las comunidades, teniendo como uso principal la alimentación humana. Igualmente, los agricultores dan cuenta de la importancia de esta especie como alimento altamente nutritivo y con algunos usos medicinales. La información recabada sugiere un conocimiento erosionado respecto de esta especie, lo cual se refleja en el nivel de conocimiento de su manejo y la disminución de su cultivo. No obstante, el conocimiento rescatado resulta de gran utilidad para el establecimiento de ensayos que se orienten a la sistematización de prácticas de cultivo de esta especie.

In order to know and rescue the history, uses and management of Dioscorea bulbifera L. given by peasant communities in the district of Donoso (Colón Province, Panamá) an ethno-botanical study was conducted in the first semester 2012. The study was developed from focus groups, field observations and semi-structured interviews to key figures (elders, healers and people who plant D. bulbifera). Five focus groups and eleven semi-structured interviews were conducted, addressing aspects of history, names, traditional management, uses and forms of consumption of air potatoes in the region. Some outstanding results, demonstrate that Dioscorea bulbifera is a species of very old presence in the communities, used mainly for human consumption. Furthermore, farmers report the importance of this species as a highly nutritious food and having some medicinal uses. The information gathered suggests an eroded knowledge about this species, which is reflected in the level of knowledge of its handling and decreased cultivation. However, the rescued knowledge is useful for establishing essays that aim to systematize practices for cultivation of this species.

A low-fat yoghurt supplemented with a rooster comb extract on muscle joint function in adults with mild knee pain: a randomized, double blind, parallel, placebo-controlled, clinical trial of efficacy.

Preliminary results suggested that oral-administration of rooster comb extract (RCE) rich in hyaluronic acid (HA) was associated with improved muscle strength. Following these promising results, the objective of the present study was to evaluate the effect of low-fat yoghurt supplemented with RCE rich in HA on muscle function in adults with mild knee pain; a symptom of early osteoarthritis. Participants (n = 40) received low-fat yoghurt (125 mL d(-1)) supplemented with 80 mg d(-1) of RCE and the placebo group (n = 40) consumed the same yoghurt without the RCE, in a randomized, controlled, double-blind, parallel trial over 12 weeks. Using an isokinetic dynamometer (Biodex System 4), RCE consumption, compared to control, increased the affected knee peak torque, total work and mean power at 180° s(-1), at least 11% in men (p < 0.05) with no differences in women. No dietary differences were noted. These results suggest that long-term consumption of low-fat yoghurt supplemented with RCE could be a dietary tool to improve muscle strength in men, associated with possible clinical significance. However, further studies are needed to elucidate reasons for these sex difference responses observed, and may provide further insight into muscle function.

No evidence for the occurrence of substrate inhibition of Arabidopsis thaliana sucrose synthase-1 (AtSUS1) by fructose and UDP-glucose.

Sucrose synthase (SuSy) catalyzes the reversible conversion of sucrose and NDP into the corresponding nucleotide-sugars and fructose. The Arabidopsis genome possesses six SUS genes (AtSUS1-6) that code for proteins with SuSy activity. As a first step to investigate optimum fructose and UDP-glucose (UDPG) concentrations necessary to measure maximum sucrose-producing SuSy activity in crude extracts of Arabidopsis, in this work we performed kinetic analyses of recombinant AtSUS1 in two steps: (1) SuSy reaction at pH 7.5, and (2) chromatographic measurement of sucrose produced in step 1. These analyses revealed a typical Michaelis-Menten behavior with respect to both UDPG and fructose, with Km values of 50 µM and 25 mM, respectively. Unlike earlier studies showing the occurrence of substrate inhibition of UDP-producing AtSUS1 by fructose and UDP-glucose, these analyses also revealed no substrate inhibition of AtSUS1 at any UDPG and fructose concentration. By including 200 mM fructose and 1 mM UDPG in the SuSy reaction assay mixture, we found that sucrose-producing SuSy activity in leaves and stems of Arabidopsis were exceedingly higher than previously reported activities. Furthermore, we found that SuSy activities in organs of the sus1/sus2/sus3/sus4 mutant were ca. 80-90% of those found in WT plants.

Sucrose synthase activity in the sus1/sus2/sus3/sus4 Arabidopsis mutant is sufficient to support normal cellulose and starch production.

Sucrose synthase (SUS) catalyzes the reversible conversion of sucrose and a nucleoside diphosphate into the corresponding nucleoside diphosphate-glucose and fructose. In Arabidopsis, a multigene family encodes six SUS (SUS1-6) isoforms. The involvement of SUS in the synthesis of UDP-glucose and ADP-glucose linked to Arabidopsis cellulose and starch biosynthesis, respectively, has been questioned by Barratt et al. [(2009) Proc Natl Acad Sci USA 106:13124-13129], who showed that (i) SUS activity in wild type (WT) leaves is too low to account for normal rate of starch accumulation in Arabidopsis, and (ii) different organs of the sus1/sus2/sus3/sus4 SUS mutant impaired in SUS activity accumulate WT levels of ADP-glucose, UDP-glucose, cellulose and starch. However, these authors assayed SUS activity under unfavorable pH conditions for the reaction. By using favorable pH conditions for assaying SUS activity, in this work we show that SUS activity in the cleavage direction is sufficient to support normal rate of starch accumulation in WT leaves. We also demonstrate that sus1/sus2/sus3/sus4 leaves display WT SUS5 and SUS6 expression levels, whereas leaves of the sus5/sus6 mutant display WT SUS1-4 expression levels. Furthermore, we show that SUS activity in leaves and stems of the sus1/sus2/sus3/sus4 and sus5/sus6 plants is ∼85% of that of WT leaves, which can support normal cellulose and starch biosynthesis. The overall data disprove Barratt et al. (2009) claims, and are consistent with the possible involvement of SUS in cellulose and starch biosynthesis in Arabidopsis.

Dual targeting to mitochondria and plastids of AtBT1 and ZmBT1, two members of the mitochondrial carrier family.

Zea mays and Arabidopsis thaliana Brittle 1 (ZmBT1 and AtBT1, respectively) are members of the mitochondrial carrier family. Although they are presumed to be exclusively localized in the envelope membranes of plastids, confocal fluorescence microscopy analyses of potato, Arabidopsis and maize plants stably expressing green fluorescent protein (GFP) fusions of ZmBT1 and AtBT1 revealed that the two proteins have dual localization to plastids and mitochondria. The patterns of GFP fluorescence distribution observed in plants stably expressing GFP fusions of ZmBT1 and AtBT1 N-terminal extensions were fully congruent with that of plants expressing a plastidial marker fused to GFP. Furthermore, the patterns of GFP fluorescence distribution and motility observed in plants expressing the mature proteins fused to GFP were identical to those observed in plants expressing a mitochondrial marker fused to GFP. Electron microscopic immunocytochemical analyses of maize endosperms using anti-ZmBT1 antibodies further confirmed that ZmBT1 occurs in both plastids and mitochondria. The overall data showed that (i) ZmBT1 and AtBT1 are dually targeted to mitochondria and plastids; (ii) AtBT1 and ZmBT1 N-terminal extensions comprise targeting sequences exclusively recognized by the plastidial compartment; and (iii) targeting sequences to mitochondria are localized within the mature part of the BT1 proteins.

A suggested model for potato MIVOISAP involving functions of central carbohydrate and amino acid metabolism, as well as actin cytoskeleton and endocytosis.

We have recently found that microbial species ranging from Gram-negative and Gram-positive bacteria to different fungi emit volatiles that strongly promote starch accumulation in leaves of both mono- and di-cotyledonous plants. Transcriptome and enzyme activity analyses of potato leaves exposed to volatiles emitted by Alternaria alternata revealed that starch over-accumulation was accompanied by enhanced 3-phosphoglycerate to Pi ratio, and changes in functions involved in both central carbohydrate and amino acid metabolism. Exposure to microbial volatiles also promoted changes in the expression of genes that code for enzymes involved in endocytic uptake and traffic of solutes. With the overall data we propose a metabolic model wherein important determinants of accumulation of exceptionally high levels of starch include (a) upregulation of ADPglucose-producing SuSy, starch synthase III and IV, proteins involved in the endocytic uptake and traffic of sucrose, (b) down-regulation of acid invertase, starch breakdown enzymes and proteins involved in internal amino acid provision, and (c) 3-phosphoglycerate-mediated allosteric activation of ADPglucose pyrophosphorylase.

Microbial volatile emissions promote accumulation of exceptionally high levels of starch in leaves in mono- and dicotyledonous plants.

Microbes emit volatile compounds that affect plant growth and development. However, little or nothing is known about how microbial emissions may affect primary carbohydrate metabolism in plants. In this work we explored the effect on leaf starch metabolism of volatiles released from different microbial species ranging from Gram-negative and Gram-positive bacteria to fungi. Surprisingly, we found that all microbial species tested (including plant pathogens and species not normally interacting with plants) emitted volatiles that strongly promoted starch accumulation in leaves of both mono- and dicotyledonous plants. Starch content in leaves of plants treated for 2 d with microbial volatiles was comparable with or even higher than that of reserve organs such as potato tubers. Transcriptome and enzyme activity analyses of potato leaves exposed to volatiles emitted by Alternaria alternata revealed that starch overaccumulation was accompanied by up-regulation of sucrose synthase, invertase inhibitors, starch synthase class III and IV, starch branching enzyme and glucose-6-phosphate transporter. This phenomenon, designated as MIVOISAP (microbial volatiles-induced starch accumulation process), was also accompanied by down-regulation of acid invertase, plastidial thioredoxins, starch breakdown enzymes, proteins involved in internal amino acid provision and less well defined mechanisms involving a bacterial- type stringent response. Treatment of potato leaves with fungal volatiles also resulted in enhanced levels of sucrose, ADPglucose, UDPglucose and 3-phosphoglycerate. MIVOISAP is independent of the presence of sucrose in the culture medium and is strongly repressed by cysteine supplementation. The discovery that microbial volatiles trigger starch accumulation enhancement in leaves constitutes an unreported mechanism for the elicidation of plant carbohydrate metabolism by microbes.

Escherichia coli glycogen metabolism is controlled by the PhoP-PhoQ regulatory system at submillimolar environmental Mg2+ concentrations, and is highly interconnected with a wide variety of cellular processes.

Using the Keio collection of gene-disrupted mutants of Escherichia coli, we have recently carried out a genome-wide screening of the genes affecting glycogen metabolism. Among the mutants identified in the study, Delta mgtA, Delta phoP and Delta phoQ cells, all lacking genes that are induced under low extracellular Mg2+ conditions, displayed glycogen-deficient phenotypes. In this work we show that these mutants accumulated normal glycogen levels when the culture medium was supplemented with submillimolar Mg2+ concentrations. Expression analyses conducted in wild-type, Delta phoP and Delta phoQ cells showed that the glgCAP operon is under PhoP-PhoQ control in the submillimolar Mg2+ concentration range. Subsequent screening of the Keio collection under non-limiting Mg2+ allowed the identification of 183 knock-out mutants with altered glycogen levels. The stringent and general stress responses, end-turnover of tRNA, intracellular AMP levels, and metabolism of amino acids, iron, carbon and sulfur were major determinants of glycogen levels. glgC::lacZY expression analyses using mutants representing different functional categories revealed that the glgCAP operon belongs to the RelA regulon. We propose an integrated metabolic model wherein glycogen metabolism is (a) tightly controlled by the energy and nutritional status of the cell and (b) finely regulated by changes in environmental Mg2+ occurring at the submillimolar concentration range.

Enhancing sucrose synthase activity in transgenic potato (Solanum tuberosum L.) tubers results in increased levels of starch, ADPglucose and UDPglucose and total yield.

Sucrose synthase (SuSy) is a highly regulated cytosolic enzyme that catalyzes the conversion of sucrose and a nucleoside diphosphate into the corresponding nucleoside diphosphate glucose and fructose. To determine the impact of SuSy activity in starch metabolism and yield in potato (Solanum tuberosum L.) tubers we measured sugar levels and enzyme activities in tubers of SuSy-overexpressing potato plants grown in greenhouse and open field conditions. We also transcriptionally characterized tubers of SuSy-overexpressing and -antisensed potato plants. SuSy-overexpressing tubers exhibited a substantial increase in starch, UDPglucose and ADPglucose content when compared with controls. Tuber dry weight, starch content per plant and total yield of SuSy-overexpressing tubers increased significantly over those of control plants. In contrast, activities of enzymes directly involved in starch metabolism in SuSy-overexpressing tubers were normal when compared with controls. Transcriptomic analyses using POCI arrays and the MapMan software revealed that changes in SuSy activity affect the expression of genes involved in multiple biological processes, but not that of genes directly involved in starch metabolism. These analyses also revealed a reverse correlation between the expressions of acid invertase and SuSy-encoding genes, indicating that the balance between SuSy- and acid invertase-mediated sucrolytic pathways is a major determinant of starch accumulation in potato tubers. Results presented in this work show that SuSy strongly determines the intracellular levels of UDPglucose, ADPglucose and starch, and total yield in potato tubers. We also show that enhancement of SuSy activity represents a useful strategy for increasing starch accumulation and yield in potato tubers.

Plastidial localization of a potato 'Nudix' hydrolase of ADP-glucose linked to starch biosynthesis.

Escherichia coli and potato (Solanum tuberosum) ADP-sugar pyrophosphatases (EcASPP and StASPP, respectively) are 'Nudix' hydrolases of the bacterial glycogen and starch precursor molecule, ADP-glucose (ADPG). We have previously shown that potato leaves expressing EcASPP either in the cytosol or in the chloroplast exhibited large reductions in the levels of starch, suggesting the occurrence of cytosolic and plastidial pools of ADPG linked to starch biosynthesis. In this work, we produced and characterized potato and Arabidopsis plants expressing EcASPP and StASPP fused with green fluorescent protein (GFP). Confocal fluorescence microscopy analyses of these plants confirmed that EcASPP-GFP has a cytosolic localization, whereas StASPP-GFP occurs in the plastid stroma. Both source leaves and potato tubers from EcASPP-GFP-expressing plants showed a large reduction of the levels of both ADPG and starch. In contrast, StASPP-GFP-expressing leaves and tubers exhibited reduced starch and normal ADPG contents when compared with control plants. With the exception of starch synthase in StASPP-GFP-expressing plants, no pleiotropic changes in maximum catalytic activities of enzymes closely linked to starch metabolism could be detected in EcASPP-GFP- and StASPP-GFP-expressing plants. The overall data (i) show that potato plants possess a plastidial ASPP that has access to ADPG linked to starch biosynthesis and (ii) are consistent with the occurrence of plastidic and cytosolic pools of ADPG linked to starch biosynthesis.