39 research outputs found
Power engineering challenges in Zambia
The paper presents a review of current power engineering challenges in Zambia in relevance to the required potential necessary for the country’s modern economic development. An outline of the energy sector is provided. The driving need for enhancing the development of the energy sector is highlighted, accounted by the country’s annual increase of GDP, leading to an increase in electricity demand. Possible mitigations are suggested, with the development of Zambia's rich potential in renewable energy, as well as upgrading the operating power plants and constructing more off-grid and on-grid generating facilities
Enzymology of the branched-chain amino acid oxidation disorders: the valine pathway
Valine is one of the three branched-chain amino acids which undergoes oxidation within mitochondria. In this paper, we describe the current state of knowledge with respect to the enzymology of the valine oxidation pathway and the different disorders affecting oxidation
Fenologia e produtividade da fruta-pão (Artocarpus Altilis) e da Jaca (A. heterophyllus) na Amazônia Central
A fruta-pão (Artocarpus altilis) e a jaca (A. heterophyllus) são comumente cultivadas na Amazônia. Ambas apresentaram vários picos de floração ao longo do ano. A fruta-pão floresceu na época chuvosa e na de estiagem, enquanto que a jaca floresceu principalmente na época chuvosa. A proporção de inflorescências estaminadas e pistiladas na fruta-pão alternou irregularmente ao longo do ano, enquanto as flores pistiladas na jaca foram quase sempre mais frequentes. Os frutos da fruta-pão estavam presentes durante a maioria do ano, com picos de abundância no início da época chuvosa (janeiro a março) e na época de estiagem (agosto a outubro), enquanto frutos de jaca estavam presentes com abundância na época chuvosa de 1988 (janeiro a março) e na época de estiagem de 1988 e 1989 (julho a setembro). O vingamento dos frutos da fruta-pão foi maior que o da jaca, com médias de 76% e 48% por semestre, respectivamente. Tanto a fruta-pão como a jaca apresentaram uma acentuada caída de frutos entre o vingamento e a maturação, com médias de 36% e 28% por ano, respectivamente. Embora o número de frutos produzidos por planta não foi muito diferente (médias de 53 e 45 por planta, respectivamente), a produtividade da jaca foi expressivamente maior (475 kg/planta) que a da fruta-pão (48 kg/planta), porque os frutos da jaca são maiores que os da fruta-pão (médias de 8,9 kg e 1,1 kg, respectivamente). As abelhas foram os principais insetos visitantes, sendo muito mais numerosas que as formigas, borboletas ou moscas
Quantifying Reductive Carboxylation Flux of Glutamine to Lipid in a Brown Adipocyte Cell Line*S⃞
We previously reported that glutamine was a major source of carbon for
de novo fatty acid synthesis in a brown adipocyte cell line. The
pathway for fatty acid synthesis from glutamine may follow either of two
distinct pathways after it enters the citric acid cycle. The glutaminolysis
pathway follows the citric acid cycle, whereas the reductive carboxylation
pathway travels in reverse of the citric acid cycle from α-ketoglutarate
to citrate. To quantify fluxes in these pathways we incubated brown adipocyte
cells in [U-13C]glutamine or [5-13C]glutamine and
analyzed the mass isotopomer distribution of key metabolites using models that
fit the isotopomer distribution to fluxes. We also investigated inhibitors of
NADP-dependent isocitrate dehydrogenase and mitochondrial citrate export. The
results indicated that one third of glutamine entering the citric acid cycle
travels to citrate via reductive carboxylation while the remainder is oxidized
through succinate. The reductive carboxylation flux accounted for 90% of all
flux of glutamine to lipid. The inhibitor studies were compatible with
reductive carboxylation flux through mitochondrial isocitrate dehydrogenase.
Total cell citrate and α-ketoglutarate were near isotopic equilibrium as
expected if rapid cycling exists between these compounds involving the
mitochondrial membrane NAD/NADP transhydrogenase. Taken together, these
studies demonstrate a new role for glutamine as a lipogenic precursor and
propose an alternative to the glutaminolysis pathway where flux of glutamine
to lipogenic acetyl-CoA occurs via reductive carboxylation. These findings
were enabled by a new modeling tool and software implementation (Metran) for
global flux estimation