Insulin regulation of spermatozoa metabolism.
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Sialic acid levels were evaluated by means of the enzymatic colorimetric Biochemia method on 24 hours urine samples of 250 males and females; the urine analysis, serum urea and glucose and creatinine clearance were in normal range. Means values of urinary sialic acid on samples treated with charcoal powder activated to remove the pyruvate-oxidase inhibitors were: 53.4 mg/l, 63.5 mg/24 hours and 58.7 mg/24 hours/1.73 m2.
Glucose, lactate, and pyruvate can be continuously measured in whole blood by using three extracorporeal electrochemical biosensors. We fixed two newly developed sensors, for lactate and pyruvate, in series with an endocrine artificial pancreas ("Betalike") without affecting its performance. These new sensors for use with whole blood should be able to clarify the fate of the intermediary metabolites of glucose in diabetic patients receiving infusions of drugs or insulin.
By comparing environmental anaerobiosis with exercise anaerobiosis it appears that animals with high anoxia tolerance use (partly) different types of metabolic reactions to sustain energy metabolism, whereas low tolerance animals (Arthropoda, Echinodermata, Vertebrata) use the same pathway under both conditions. During exercise anaerobiosis the classical glycolysis (lactate pathway) is a main pathway among all multicellular organisms, although in marine invertebrates--except the Arthropoda and Echinodermata--it mostly does not terminate in lactate. During environmental anaerobiosis Cnidaria, Mollusca, Annelida and Sipunculida first couple additional pathways for energy extraction to the glycolytic pathway (the aspartate--succinate pathway) and later deviate the main carbon flow of glycogen at the level of phosphoenolpyruvate towards succinate, propionate and acetate production. Metabolic adaptations to anoxic cellular conditions in these groups are high fuel stores, increased ATP yield by anaerobic sources, formation of easily excretable (volatile) end products, an aspartate-dependent system for transport of hydrogen through the inner membrane of the mitochondrion and a rapid recovery from anaerobic metabolism. During anaerobic conditions three sources can contribute to the anaerobic power output, endogenous stores of both ATP and phosphagen and catabolism. Anaerobic power output rates have been calculated for a number of Mollusca, Annelida and Crustacea. Extreme anoxia resistance is coupled to a strongly reduced metabolic rate. In animals with high aspartate stores, the aspartate--succinate pathway and phosphagen hydrolysis can provide sufficient ATP during environmental anaerobiosis; however, with exercise anaerobiosis when ATP turnover rates may be increased by a factor of 20, pyruvate derivatives simultaneously accumulate in high amounts relative to succinate.
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Neuraminidase expressed by cloned nanH of Clostridium perfringens has been immobilized and employed to determine the concentration of sialic acid in human serum. Two enzyme pairs, cloned neuraminidase-N-acetylneuraminate (NANA) lyase and pyruvate oxidase-peroxidase, have been respectively co-immobilized on to 1,12-aminododecane-agarose with glutaraldehyde. The relative specific activities of the co-immobilized neuraminidase and NANA lyase were 61 and 77%, and those of pyruvate oxidase and peroxidase were 51 and 96% of the corresponding soluble enzymes respectively. The optimal reaction pH at 37% C for each of the co-immobilized enzymes was about 1 pH unit higher than that of the corresponding soluble enzyme. The optimal reaction temperature of peroxidase was increased as a result of immobilization. The thermostability of the immobilized cloned neuraminidase, NANA lyase, pyruvate oxidase and peroxidase were increased 80-, 83-, 115- and 147-fold at 45 degrees C over the soluble forms respectively. The results correlated satisfactorily with those obtained by using a soluble enzyme system. The system is thus a reliable assay method for sialic acid in serum.
An immobilized enzyme system has been developed and employed to determine the concentration of sialic acid (N-acetylneuraminic acid) in human serum and urine. Two enzyme pairs, neuramindiase-Neu-5-Ac lyase and pyruvate oxidase-peroxidase, have been respectively co-immobilized onto 1,12-aminododecane-agarose with glutaraldehyde. The relative specific activity of the co-immobilized neuraminidase and Neu-5-Ac lyase were 60% and 78%, and those of pyruvate oxidase and peroxidase were 50% and 95% of the corresponding soluble enzymes, respectively. The optimal reaction pH at 37 degrees C for each of the co-immobilized enzymes was about one pH unit higher than that of the corresponding soluble enzyme. The optimal reaction temperature of each enzyme was increased as a result of immobilization. The thermal stability at 45 degrees C of the immobilized neuraminidase, Neu-5-Ac lyase, pyruvate oxidase, and peroxidase were increased 80-, 83-, 115-, and 147-fold, respectively. Km and Vm of each immobilized and co-immobilized enzyme have also been determined. The system provided a convenient and rapid method to determine the concentration of total sialic acid without pretreatment of the sample. The results correlated satisfactorily with those obtained by using a soluble enzyme system. The co-immobilized enzymes were stable for at least 1 year of 500 tests when used repeatedly. The system is thus a reproducible and reliable novel assay method for sialic acid in the serum or urine sample.