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Decreased activity of mitochondrial PDH with age has been shown in the heart as well as in certain regions of the brain (the striatum and brainstem). [6] Pyruvate dehydrogenase (PDH) deficiency is a congenital degenerative metabolic disease resulting from a mutation of the pyruvate dehydrogenase complex (PDC) located on the X chromosome.
In eukaryotic cells the pyruvate decarboxylation occurs inside the mitochondrial matrix, after transport of the substrate, pyruvate, from the cytosol. The transport of pyruvate into the mitochondria is via the transport protein pyruvate translocase. Pyruvate translocase transports pyruvate in a symport fashion with a proton (across the inner ...
The PDHB gene is responsible for the coding of the E1 beta subunit of the pyruvate dehydrogenase complex. The DLAT gene is responsible for the coding of the E2 subunit, and the PDP1 is responsible for producing the PDH phosphatase catalytic subunit that catalyzes PDH dephosphorylation. This dephosphorylation activates the complex.
As PDK1 regulates the PDH complex, it has been proven to be an important regulator in certain cells, including the beta cells within the islets of the pancreas. In order to optimize glucose-stimulated insulin secretion (GSIS), a primary function of the pancreas, a low PDK1 activity must be maintained to keep PDH in a dephosphorylated and active ...
In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. [1] The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch, and sometimes the diencephalon is included in the brainstem. [2] The brainstem is very small, making up around only 2.6 percent of the brain's total ...
A vascular bundle is a part of the transport system in vascular plants. The transport itself happens in the stem, which exists in two forms: xylem and phloem. Both these tissues are present in a vascular bundle, which in addition will include supporting and protective tissues. There is also a tissue between xylem and phloem, which is the cambium.
The extinct arboreal plants of the genera Lepidodendron and Sigillaria were the first to have distinct aeration structures that rendered these modifications. "Parichnoi" (singular: parichnos) are canal-like structures that, in association with foliar traces of the stem, connected the stem's outer and middle cortex to the mesophyll of the leaf.
In some plants, the pith in the middle of the stem may dry out and disintegrate, resulting in a hollow stem. A few plants, such as walnuts, have distinctive chambered pith with numerous short cavities (see image at middle right). The cells in the peripheral parts of the pith may, in some plants, develop to be different from cells in the rest of ...