Pathways Of Glucose Utilization Research Articles

Influence of 2,4-Dichlorophenoxyacetic Acid on Pathways of Glucose Utilization in Bean Stem Tissues

2,4-Dichlorophenoxyacetic acid (2,4-D) is the best known selective herbicide for effective control of broadleafed weeds in monocotyledonous crops. Although the mechanisms by which 2,4-D acts on plants have not been elucidated, several lines of investigation have shown: A. Stimulatory and inhibitory effects on the respiration of pea and oat tissues, depending upon the concentrations employed (6). B. Reduction of bcarbohydrate content of bean stem (7). C. Increased participation of pentose cycle pathway of glucose catabolism in root tips of pea, corn, and oat seedlings (4). These results suggested that carbohydrate metabolism may be greatly effected. The present work is based upon the hypothesis that 2,4-D influences growth by affecting glucose utilization which furnishes the energy and/or building units for the synthesis of cellular constituents. This is approached by directly measuring utilization of radioactive carbon atoms from glucose in treated and untreated tissues after substantial morphological response has occurred. This paper reports the results from several experiments on the effect of 2,4-D on the pathways of glucose utilization in bean stem tissue using C14 labeled glucose.

Pathways of Glucose Utilization in Epididymal and Testicular Sperm Cells

Summary Pathways of glucose utilization in epididymal and testicular sperm cells were investigated, using C 14 -labeled glucose as a tracer. An equal contribution to CO 2 from the two substrates in epididymal spermatozoa, and a preferential recovery of CO 2 from glucose-1-C 14 , as compared with glucose-6-C 14 in testicular sperm cells, were observed. Results suggest that in epididymal spermatozoa the basic mechanism of glucose utilization is that of the Embden-Meyerhof scheme; whereas, in the testicular sperm cells, glucose may be metabolized via alternative pathways.

Pathways of glucose utilization in mammary tissue.

Although the most important method of glucose catabolism is undoubtedly by degradation via the classical Embden-Meyerhof-Parnas glycolytic pathway followed by oxidation of the triose by the tricarboxylic acid cycle, the existence of alternative routes of oxidation is now certain and these can, indeed, operate exclusively in some micro-organisms. Of these alternative pathways, the most important is that originally discovered by Warburg in yeast extracts and is now generally referred to as the pentose phosphate pathway. The pioneer work of Warburg, Lipmann and Dickens has been reviewed by Dickens (1953). Renewed interest in this pathway during the last few years has established its widespread occurrence in animal tissues, plants and micro-organisms. Precise evidence for its cyclic nature and characterization of the intermediates and enzyme reactions involved can be attributed chiefly to Horecker and Racker and their co-workers (Horecker & Mehler 1955; Gunsalas, Horecker & Wood 1955; Racker 1957). This somewhat complex cycle is shown in figure 31. Of the three glucose 6-phosphate molecules required for each turn of the cycle, two are regenerated from pentose phosphate by reactions catalyzed by transketolase and transaldolase. All of these enzyme reactions, like those of the glycolytic route, are localized essentially in the soluble fraction of cell homogenates (Glock & McLean 1954; Newburgh & Cheldelin 1956).

Studies on the interaction between phagocytes and tubercle bacilli. III. Some metabolic effects in guinea pigs associated with infection with tubercle bacilli.

In continuing studies concerning the interactions between phagocytes and tubercle bacilli the effect of tuberculous infection on respiration and glucose utilization was investigated in guinea pigs. Peritoneal exudates rich in polymorphonuclear leucocytes, derived from guinea pigs infected with tubercle bacilli, had a significantly higher rate of respiration than the same cells from normal animals. The difference between cells from normal and infected animals was greater when the animals were infected with a virulent strain (Vallée) than when infected with an attenuated one (R1Rv or BCG). By the use of glucose labelled with C(14) at position 1 or 6, or uniformly labelled glucose, it was established that this difference in oxygen uptake between normal and infected cells was probably not caused by a difference in the pathway of glucose utilization. Similarly, the respiration of liver and kidney slices from normal and infected guinea pigs was compared and it was found that liver slices showed differences similar to those shown by leucocytes, but that the kidney slices did not. The possibility has not been ruled out that the difference in rate of respiration of liver slices due to infection might be caused by tuberculous lesions in the livers of infected animals. The mononuclear cells which invade the liver have a higher rate of oxygen uptake than liver cells. The rate of glucose utilization and the total amount of CO(2) produced was also determined in intact guinea pigs. Both functions were found not to differ significantly in normal and infected animals. The rate of production of CO(2) from C(1) and C(6) of glucose was the same in both groups of animals. The ratio of the rate of production of C(14)O(2) from C(1) and C(6) of glucose by the whole animal was found to be about 1.35. It was found to be much higher with polymorphonuclear leucocytes (C(1)/C(6) = 8 in the absence of serum). During the process of phagocytosis this ratio increased from about 25 to about 130 (in the presence of 2 per cent serum) indicating an increase in the direct oxidative pathway of glucose utilization during stimulated cellular activity.

A newer pathway of carbohydrate metabolism; the pentose phosphate pathway.

In the past thirty years a vast body of information has been compiled relating to carbohydrate metabolism. Nevertheless, it is becoming increasingly evident that the elucidation of the metabolic disturbance in diabetes mellitus requires an even more complete knowledge than is presently available of the complex chemical routes followed by glucose in its conversions and interactions with other cell components. In this area of carbohydrate metabolism most gratifying progress has been made with the demonstration of previously unsuspected pathways of glucose utilization. Until rather recently, it was generally believed that the primary, if not the sole, route of glucose breakdown by mammalian tissue was via the Embden-Meyerhof or anaerobic-glycolytic pathway involving the conversion of glucose to pyruvate and lactate and its subsequent oxidation to co2 by the citric acid cycle. Evidence has now accumulated to indicate the existence of at least one new pathway of glucose metabolism, referred to as the pentose phosphate pathway, or the hexose monophosphate oxidative shunt, which may often supplement significantly the anaerobic-glycolytic scheme. Before turning to some of the details and possible significance of this alternate pathway, a brief review of the reactions of glycolysis and the citric acid cycle is desirable.

Pathways of glucose utilization in the mammary gland of the rat

Pathways of glucose utilization in the mammary gland of the rat

GLUCOSE-6-PHOSPHATE DEHYDROGENASE OF ADRENAL TISSUE

The direct oxidative pathway of glucose utilization or the hexose monophosphate shunt has received a great deal of attention recently, and numerous attempts have been made to evaluate its importance in various tissues. Glock and McLean, in making a survey of the levels of enzymes of this pathway in a number of mammalian tissues, recently reported unusually high activity in the adrenal glands, particularly in the adrenal cortex (1). This paper reports the results of an investigation of carbohydrate metabolism in adrenal tissue which also led to this finding. At the time this investigation was started, the knowledge of carbohydrate metabolism in the adrenal gland was limited to the observation that a glycolytic system could be obtained from adrenal tissue (2, 3) and that certain intermediates of the tricarboxylic acid cycle could be oxidized by the adrenal gland (4, 5). Evidence is presented in this report for the existence of two different pathways of glucose utilization in adrenal tissue. Besides the glycolytic pathway, there is shown to be a very active alternative pathway which proves to be the hexose monophosphate shunt. The cyclic nature of this pathway is indicated in adrenal systems as it has been previously in other tissues. A comparison is given of the glucose-6-phosphate dehydrogenase levels of a number of mammalian tissues, and Glock and McLean’s report of the unusually high activity in adrenal cortex is confirmed. A preliminary report of this work was presented earlier (6).