Arteriovenous differences

Since the brain utilizes energy almost exclusively from oxidative metabolism of glucose, brain metabolism has been studied by focusing on net oxygen and glucose uptake. Oxygen consumption was classically measured as the arteriovenous difference of 02 content. When a substance is exchanged between brain and blood, the difference between its steady state of delivery to brain in the arterial blood and removal in the venous blood must be equal to the net rate of its utilization or... 

The combination of hypoxia and hypercapnia in pulmonary insufficiency results in cerebral vasodilation and increased CBF and may lead to increased intracranial pressure. Arteriovenous differences for oxygen across the brain generally decrease as a function of increased CBF, leaving CMR02 unchanged [6]. 

Table 7.5 Arteriovenous differences of oxygen, glucose, fatty acids, acetoacetate and hydroxybutyrate across the brain of obese females during prolonged fasting...

Measurement of arteriovenous differences across the brain shows that it does take up the precursor amino acids for formation of the neurotransmitters including tryptophan and tyrosine. It also takes up the branched-chain amino acids for formation of glutamine. 

From arteriovenous difference, the utilisation of glucose by human brain is approximately 0.32 mmol/min which, if completely oxidised would consume (6 x 0.32) or 1.92 mmol/min of oxygen. The rate of oxygen uptake by the human brain is also measured from arteriovenous difference it is 2.1 mmol/min (i.e. very close to that calculated, 1.92). 

Arteriovenous differences show that after the overnight fast the liver of a lean adult releases glucose at a rate of about 8 g/h and the brain utilises more than half of this... 

Arginine, 2D biosynthesis, 435 catabolism, 431 134 chemical structure, 20 plasma concentration, 465 Argininosuccinate lyase, 439 Acgininosuccinate synthase, 439 Aromatic amino acids, chemical structure, 19 Arsenate, 840 Artenosclcrosis, 357 Arteriovenous differences, 19 199 Artery, physiology, 359 Ascoitale... 

Measuring Body Fuel Use in Specific Organs Arteriovenous Differences Special Topic Nitric Oxide and Vasodilation Creatine Phosphate Creatinine Glycogen Gluconeogenesis... 

The PO2 at the venous end of the capillaries should stay around 38 mmHg, and thus the normal arteriovenous difference in PO2 is 50 to 60 mm Hg. This corresponds to a normal delivery of 2.3 mmol of O2 to the tissue per liter of blood. 

The aromatization of C19 3 S-hydroxy-A- steroids received by the placenta from the fetus is the major source of the estrogens in the later stages of pregnancy (M16). Their utilization by the placenta, together with estrogen production will be seen from the arteriovenous differences given in Tables 3 and 4. 

It will be seen from the arteriovenous differences given in Table 3 that a considerable amount of progesterone produced by the placenta is... 

The known effects of thyrocalcitonin are primarily in bone. Removal of the gut had no effect on the hypocalcemic effect of calcitonin (A6), and neither did nephrectomy (H8). No change in soft tissue calcium content was seen in soft tissues to explain the hypocalcemia (Kl). Calcitonin apparently inhibits bone resorption and thereby decreases calcium entry into the blood. Calcitonin prevents the release of calcium from cultured bone (A5, FIO). In vivo, the release of Ca from prelabeled bone is decreased by calcitonin (Jl). The bone arteriovenous difference in calcium levels is increased by calcitonin (M3). The mode of action of calcitonin is unknown. Calcitonin does not inhibit parathormone (A6, H7, T3), nor is its effect apparently mediated through RNA synthesis (T3). 

Marconi AM, Battaglia EC, Meschia G, et al. 1989. A comparison of amino acid arteriovenous differences across the liver and placenta of the fetal lamb. Am J Physiol 257(6 Pt 1) E909-E915. 

Relevant laboratory findings include an early decreased arteriovenous difference in the partial pressure of oxygen (Po2) with progressive lactic acidosis. 

Bartlett, K., Bhuiyan, A.K., Aynsley Green, A., Butler, P.C. Alberti, K.G. (1989) Clin. Sci. 77, 413 16. Human forearm arteriovenous differences of carnitine, short-chain acylcarnitine and long-chain acylcamitine. 

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