Oxygen consumption and lipoxygenase activity in isolated tomato fruit chromoplasts

This Study using purified tomato fruit chromoplasts has shown significant rates of oxygen consumption even in the absence of external precursors. Oxygen consumption rates increased up to 7-fold when chromoplast samples were incubated for 24 h at room temperature. This increase in oxygen consumption is most likely due to the activation of lipoxygenase in the chromoplasts

Precursor uptake assays and metabolic analyses in isolated tomato fruit chromoplasts

<p>Abstract</p> <p>Background</p> <p>Carotenoids are the most widespread group of pigments found in nature. In addition to their role in the physiology of the plant, carotenoids also have nutritional relevance as their incorporation in the human diet provides health benefits. In non-photosynthetic tissues, carotenoids are synthesized and stored in specialized plastids called chromoplasts. At present very little is known about the origin of the metabolic precursors and cofactors required to sustain the high rate of carotenoid biosynthesis in these plastids. Recent proteomic data have revealed a number of biochemical and metabolic processes potentially operating in fruit chromoplasts. However, considering that chloroplast to chromoplast differentiation is a very rapid process during fruit ripening, there is the possibility that some of the proteins identified in the proteomic analysis could represent remnants no longer having a functional role in chromoplasts. Therefore, experimental validation is necessary to prove whether these predicted processes are actually operative in chromoplasts.</p> <p>Results</p> <p>A method has been established for high-yield purification of tomato fruit chromoplasts suitable for metabolic studies. Radiolabeled precursors were efficiently incorporated and further metabolized in isolated chromoplast. Analysis of labeled lipophilic compounds has revealed that lipid biosynthesis is a very efficient process in chromoplasts, while the relatively low incorporation levels found in carotenoids suggest that lipid production may represent a competing pathway for carotenoid biosynthesis. Malate and pyruvate are efficiently converted into acetyl-CoA, in agreement with the active operation of the malic enzyme and the pyruvate dehydrogenase complex in the chromoplast. Our results have also shown that isolated chromoplasts can actively sustain anabolic processes without the exogenous supply of ATP, thus suggesting that these organelles may generate this energetic cofactor in an autonomous way.</p> <p>Conclusions</p> <p>We have set up a method for high yield purification of intact tomato fruit chromoplasts suitable for precursor uptake assays and metabolic analyses. Using targeted radiolabeled precursors we have been able to unravel novel biochemical and metabolic aspects related with carotenoid and lipid biosynthesis in tomato fruit chromoplasts. The reported chromoplast system could represent a valuable platform to address the validation and characterization of functional processes predicted from recent transcriptomic and proteomic data.</p

Precursor uptake assays and metabolic analyses in isolated tomato fruit chromoplasts

Background Carotenoids are the most widespread group of pigments found in nature. In addition to their role in the physiology of the plant, carotenoids also have nutritional relevance as their incorporation in the human diet provides health benefits. In non-photosynthetic tissues, carotenoids are synthesized and stored in specialized plastids called chromoplasts. At present very little is known about the origin of the metabolic precursors and cofactors required to sustain the high rate of carotenoid biosynthesis in these plastids. Recent proteomic data have revealed a number of biochemical and metabolic processes potentially operating in fruit chromoplasts. However, considering that chloroplast to chromoplast differentiation is a very rapid process during fruit ripening, there is the possibility that some of the proteins identified in the proteomic analysis could represent remnants no longer having a functional role in chromoplasts. Therefore, experimental validation is necessary to prove whether these predicted processes are actually operative in chromoplasts. Results A method has been established for high-yield purification of tomato fruit chromoplasts suitable for metabolic studies. Radiolabeled precursors were efficiently incorporated and further metabolized in isolated chromoplast. Analysis of labeled lipophilic compounds has revealed that lipid biosynthesis is a very efficient process in chromoplasts, while the relatively low incorporation levels found in carotenoids suggest that lipid production may represent a competing pathway for carotenoid biosynthesis. Malate and pyruvate are efficiently converted into acetyl-CoA, in agreement with the active operation of the malic enzyme and the pyruvate dehydrogenase complex in the chromoplast. Our results have also shown that isolated chromoplasts can actively sustain anabolic processes without the exogenous supply of ATP, thus suggesting that these organelles may generate this energetic cofactor in an autonomous way. Conclusions We have set up a method for high yield purification of intact tomato fruit chromoplasts suitable for precursor uptake assays and metabolic analyses. Using targeted radiolabeled precursors we have been able to unravel novel biochemical and metabolic aspects related with carotenoid and lipid biosynthesis in tomato fruit chromoplasts. The reported chromoplast system could represent a valuable platform to address the validation and characterization of functional processes predicted from recent transcriptomic and proteomic data

Modeling system risk in the South African insurance sector : a dynamic mixture copula approach

Abstract: In this paper, a dynamic mixture copula model is used to estimate the marginal expected shortfall in the South African insurance sector. We also employ the generalized autoregressive score model (GAS) to capture the dynamic asymmetric dependence between the insurers’ returns and the stock market returns. Furthermore, the paper implements a ranking framework that expresses to what extent individual insurers are systemically important in the South African economy. We use the daily stock return of five South African insurers listed on the Johannesburg Stock Exchange from November 2007 to June 2020. We find that Sanlam and Discovery contribute the most to systemic risk, and Santam turns out to be the least systemically risky insurance company in the South African insurance sector. Our findings defy common belief whereby only banks are systemically risky financial institutions in South Africa and should undergo stricter regulatory measures. However, our results indicate that stricter regulations such as higher capital and loss absorbency requirements should be required for systemically risky insurers in South Africa

Making Fisheries Co-management Work for Both Poverty Reduction and Responsible Fisheries: Lessons from Coastal and Inland Waters of West and Central Africa

Fisheries co-management is the institutional model of choice to maintain and rebuild fishery resources in the small-scale sector. This paper argues that the transfer of regulatory and property rights from the central state to multi-stakeholder bodies, including resource users, and local government, can only achieve sectoral efficiency goals - such as maximising wealth generated from fisheries or other socially desirable optima - if they are accompanied by efforts to address the vulnerability and social exclusion of the new rights-holders and decision-makers. Case studies from West and Central African countries are presented to indicate how resource rebuilding and poverty reduction are addressed jointly by strengthening both co-management systems and the livelihoods of fishery resource users

Caractérisation Physiologique Et Évaluation Du Comportement Germinatif De Semences De Rottboellia Cochinchinensis, Euphorbia Heterophylla, Et Porophyllum Ruderale, Trois Adventices Des Rizières De Côte d’Ivoire

Weeds are the most important biological constraint reducing rice production. This study was conducted to know the physiological characteristics and the germinative behavior of the seeds of Rottboellia cochinchinensis, Euphorbia heterophylla and Porophyllum ruderale, three major weeds of rice field in Côte d'Ivoire. Seed characteristics were determined according to ISTA’s standards. These three weeds had orthodox seeds with low moisture content (&lt; 15%). These weeds raise better when they were sown on the surface (0-0.5 cm) or slightly buried in the ground. E. heterophylla and P. ruderale germinated well when their seeding density is high (150 seeds/Petri dish). For R. cochinchinensis, when the seedling density is low (25 seeds/Petri dish). The germination was maximum after five to nine days

Carotenoides en agroalimentación y salud

Los carotenoides son compuestos especiales; si bien es común referirse a ellos como pigmentos, lo cierto es que son compuestos de gran versatilidad e importancia en la naturaleza. Más específicamente, son de gran interés en agroalimentación y salud. Así, por ejemplo, son pigmentos naturales y por lo tanto tienen un importante papel en la elección de alimentos por parte de los consumidores. Asimismo, algunos de ellos son precursores de la vitamina A. Sin embargo, que cada vez exista más interés en los carotenoides en este contexto se debe en gran parte a muchos estudios de distinta naturaleza que indican que pueden proporcionar beneficios para la salud. Su interés en alimentación funcional es por lo tanto indudable. En este libro se refleja la experiencia en carotenoides de un gran número de profesionales de la región iberoamericana. En conjunto, se ofrece una visión general de la investigación sobre estos compuestos en agroalimentación y salud. Los autores son miembros de la red IBERCAROT (http://carotenoides.us.es), que tiene entre sus objetivos conformar una red estable y funcional de profesionales que aúnen esfuerzos en pos de identificar nuevas fuentes de carotenoides de interés nutricional, mejorar su producción y aumentar el valor de los productos que los contengan

Ruin problem in health care insurance with random interest rate

M.Com. (Financial Economics)Abstract: Ruin theory is a predominant topic in actuarial science and many researchers have brought their contributions in it to make the theory close to reality. Historically, the pioneers of ruin theory have assumed a risk model that is not affected by the force of interest. However, it is well-known that insurance companies operate in an economic environment where the force of interest plays an important role, hence the study of ruin probability without considering the force of interest is flawed in reality. In this thesis, we consider Ramsay’s model, modified by the inclusion of random interest rate on the surplus process, where we investigate the effect of random interest rate on the ruin probability. Autoregressive model is introduced to model the randomness of the interest rate. Based on the statistics’ test, we found that The Three- Months South Africa Treasury Bill Rates (TBR) used in this study can be modelled by an autoregressive structure of order one. We then derive exponential type upper bounds for the ruin probability by using a renewal recursive technique. Finally, we provide numerical examples where the length of the sickness period and that of the healthy period follow an Erlang distribution to illustrate our results. We found that the probability of ruin is very small when we considered a random interest rate in the Ramsay’s risk model unlike the results obtained by Adekambi (2013) when he considered a constant interest rate in the Ramsay model