Hexose Levels Research Articles

Hexose and pentose phosphates in brain during convulsions.

The Metabolism of glucose via glycolysis and the citric acid cycle represents the chief source of energy supplies in the brain. However, enzymes for the metabolism of glucose via the hexosemonophosphate (O'Neill, Simon and Shreeve, 1965) and pentose phosphate (Dreyfus and Moniz, 1962) pathway are also present in brain. A major difficulty in studying intermediates of the hexose and pentose phosphate pathway in brain is their extremely low absolute levels. Recently, fluorimetric, enzymic assays for these substrates have been developed (Kauffman, Brown, Passonneau and Lowry, 1969), and these assays, combined with rapid freezing techniques (Lowry, Passonneau, Hasselberger and Schulz, 1964) have made it possible to study these intermediates in brains of mice. Electrically‐induced tonic‐clonic convulsions are associated with a striking increase in metabolic rate in brain, but phenobarbitone minimizes changes in metabolic rate during convulsions (King, Lowry, Passonneau and Venson, 1967). In order to determine whether or not levels of hexose and pentose phosphates are altered under these conditions, assays for these substrates have been carried out in brains of convulsing mice with or without administration of phénobarbital prior to stimulus.

Regulatory factors in methylene blue catalysis in erythrocytes

In erythrocytes of man and rabbits methylene blue catalysis is limited by the following factors at the pH optimum 7.5; primarily by the cellular concentration of NADP+, next by that of glucose‐6‐P. Possible further limiting steps are glucose‐6‐phosphate dehydrogenase, phosphogluconate dehydrogenase and reduced‐NADP dehydrogenase. Calculation of the intracellular NADP+ concentration with the two‐substrate equation for the glucose‐6‐phosphate dehydrogenase‐reaction does not yield reasonable results. The existence of inhibiting factors of the methylene blue catalysis is postulated. Their amount is presumably lower in intact cells as compared with hemolysates. There is no pH dependence of the glucose‐6‐P concentration in presence of methylene blue. There exists a competition between the oxidative pentose‐phosphate‐pathway and the Embden‐Meyerhof pathway, in which the phosphofructokinase plays a key role. The proportions of the two pathways at different pH values are calculated from data on oxygen and glucose consumption. At pH values below 7.6 glucose is utilized practically exclusively via the oxidative pentose phosphate pathway, whereas the Embden‐Meyerhof pathway is inhibited. At pH 8.2 the participation of the oxidative pentose‐phosphate pathway amounts to 40% of the total glucose utilization, while the Embden‐Meyerhof pathway is little if any reduced as compared to cells without methylene blue. With increased degree of oxidation of the pyridine nucleotides there occur decreases in the levels of hexose‐ and triose‐phosphates. With these changes and the decreased flow to lactate an increased formation of 2,3‐diphosphoglycerate occurs.

Serum glycoproteins and physical exercise

Changes in serum levels of protein-bound hexoses, α 2-macroglobulins, transferrin and γM-globulins were studied after one hour of physical stress, after a night's rest, following several days of training in athletes and in normal controls. A significant rise in the levels of the proteins studied (with the exception of the γM-globulins) was observed following one hour of work on the ergometer (170 W). During the training period and competitions, aihletes had elevated serum values of the bound hexoses, transferrin and α 2-macroglobulins.

Carbohydrate Metabolism in theNarcissusLeaf

Carbohydrate contents of both the photosynthetic and the storage organs of Narcissus tazetta L. were determined at four stages in their development under both ‘natural’ growing conditions and under conditions of varying light intensities. Starch was abundantly stored in all the storage organs, particularly in the bases of the photosynthetic organs under high light intensity and also at the second dormant stage. However, its level remained relatively stable in the green part of the foliage leaf and the scape at different stages and appeared not to be affected by light except at very high intensity. It was found in both the bundle sheaths and guard cells. Sucrose, which is the first sugar of photosynthesis, was continuously exported from the green parts of the blade and the scape to their bases where it was also stored. In the dark the sucrose level became low in the green blade and the green scape but it rose with increase of light intensity. The hexose level was very low at the dormant stage in all organs examined but rose as they matured and exceeded that of sucrose in the green organs except in high light intensity. Hexose is formed presumably as a result of sucrose hydrolysis and is constantly lost, presumably through respiration. At senescence sugar disappeared almost completely from all the organs, while nearly 10 per cent of residual dry weight of starch remained in the dead tissues. The interrelationship between the carbohydrates and their movement in the leaf is discussed.

Control of dimorphism in Mucor by hexoses: inhibition of hyphal morphogenesis.

In anaerobic cultures of Mucor rouxii, morphogenesis was strongly dependent on hexose concentration as well as pCO(2). At low levels of hexose or CO(2), or both, hyphal development occurred; at high levels, the fungus developed as yeast cells. Other dimorphic strains of Mucor responded similarly to hexose and CO(2) but differred in their relative sensitivity to these agents. Glucose was the most effective hexose in eliciting yeast development of M. rouxii; fructose and mannose were next; and galactose was last. The fungus may be grown into shapes covering its entire dimorphic spectrum simply by manipulating the hexose concentration of the medium. Thus, at 0.01% glucose, hyphae were exceedingly long and narrow; at higher sugar concentrations, the hyphae became progressively shorter and wider; finally, at about 8% glucose, almost all cells and their progeny were isodiametric (spherical budding cells). Such yeast development occurred without a manifested requirement for exogenous CO(2). The stimulation of yeast development by hexose is not an artifact due to increased production of metabolic CO(2) (hyphae or yeast cells released metabolic CO(2) at similar rates). Presumably, the effect was caused by some other hexose catabolite which interfered with hyphal morphogenesis (apical growth); deprived of its polarity, the fungus grew into spherical yeastlike shapes. Although 10% glucose inhibited the development of hyphae from germinating spores, it did not prevent the elongation of preformed hyphae. This suggests that hexose inhibits hyphal morphogenesis not by blocking the operation of the enzyme complex responsible for apical growth but by preventing its initiation; such inhibition may be regarded as a repression of hyphal morphogenesis.

The protein and protein-bound carbohydrates in 4 species of nonhuman primates' sera.

SummaryBlood sera from four species of nonhuman primates were analyzed for their protein and protein-bound sugar content. Generally, the levels of total protein, protein-bound hexose, sialic acid, and fucose of Pan troglodytes (chimpanzee), Theropithecus gelada (baboon), and Macaca mulatta (rhesus monkey) are comparable to those of humans. In all species examined except Hylobates lar (gibbon), the protein-bound hexosamine levels are considerably higher than those of humans. In Hylobates lar, the total serum protein concentration is lower than in humans, while the protein-bound hexosamine level is very close to human levels. The electrophoretic patterns of the four species of nonhuman primates examined are very different from that of humans and from each other.

Serum glycoproteins in rats with experimental coccidioidomycosis.

The changes in the serum glycoproteins and the development of specific antibodies were examined during the course of experimental coccidioidomycosis in rats. The total glycoprotein, seromucoid hexose, seromucoid protein, and haptoglobin levels were signigicantly higher in sera from infected animals compared with sera from non-infected controls. These changes were evident at three days but not at two weeks following inoculation withC. immitis. The non-seromucoid hexose and total protein concentrations were not significantly different between infected animals and controls. The highest percentages of animals exhibiting positive tests for complement fixing and precipitin antibodies and positive cultures forC. immitis in organs at autopsy were found one week after infection.

The tricarboxylic acid cycle, the glyoxylate cycle, and the enzymes of glucose oxidation in Pseudomonas aeruginosa.

The enzymes of the glyoxylate cycle, the tricarboxylic acid cycle, glucose oxidation, and hydrogen transport were measured in extracts of Pseudomonas aeruginosa grown with glucose, α-ketoglutarate, or acetate as sole carbon source. The specific activity of isocitritase was increased 25-fold by growth on acetate whereas malate synthetase was increased only 4-fold. All of the enzymes of glucose metabolism, operative at the hexose level, were inducible. The enzymes of the tricarboxylic acid cycle were present under all conditions of growth but extracts from acetate-grown cells contained only one-quarter of the fumarase and pyruvic oxidase activity and half the malate-oxidizing activity of the other extracts. Transhydrogenase, NADH oxidase, and NADPH oxidase activities were similar in each type of extracts. Most of the enzymes were present in the soluble cytoplasm, exceptions being glucose oxidase, succinic dehydrogenase, and NADH oxidase.

Purification and Properties of Guanosine Diphosphate Hexose Pyrophosphorylase from Mammalian Tissues

Abstract The relative levels of guanosine diphosphate hexose and uridine diphosphate glucose pyrophosphorylases have been measured in extracts of various tissues of the rat and in the lactating glands from several mammals. Calf liver and rat mammary gland are good sources of both pyrophosphorylases. GDP-hexose pyrophosphorylase has been purified about 500-fold from mammalian tissues. The preparation purified 500-fold is not specific for either the nucleoside or the hexose component of the nucleoside diphosphate hexose. In decreasing order of activity, guanosine, inosine, and adenosine diphosphate hexoses are substrates with either glucose or mannose as the sugar. GDP-mannose and mannose 1-phosphate inhibit the formation and cleavage of GDP-glucose, but the rate of pyrophosphorolysis of GDP-glucose alone is faster than that of GDP-mannose alone. Thus, the enzyme has a higher affinity for GDP-mannose, but apparently a higher turnover for GDP-glucose. With GDP-glucose as substrate, the equilibrium constant, optimum pH, metal requirement, and Km have been determined for the purified GDP-hexose pyrophosphorylase.

A specific method for the determination of the aldotetroses

An assay procedure specific for the aldotetroses and applicable over a 5- to 200-μg range has been described. It is based on the development of a compound with a 524-mμ absorption maximum when the four-carbon sugars are reacted with phenol in hot concentrated sulfuric acid solution. The reaction conditions are a modification of those previously described for the assay of pentoses and hexoses by the phenol-sulfuric acid technique. The assay conditions described can also be utilized for the assay of these higher sugars simply by altering the level of phenol present and the wavelength employed for the determination. It is also possible to assay aldotetroses in the presence of equivalent levels of hexose or pentose with little interference and to assay the longer chain sugars in the presence of tetrose with only moderate interference. A number of reaction parameters have been studied, and the behavior of several compounds related to the four-carbon sugars under these assay conditions has been described.

The effects of total x-radiation on the glycoprotein content of blood serum in normal and hypothyroid animals

A significant increase of α1-glycoproteins and reduction of β2 and β-glycoproteins was observed after 88–90 h in intact rats subjected to total single irradiation in a dose of 600 r. The level of hexoses associated with proteins (anthronic reaction) remained unchanged. The irradiation of hypothyroid animals had no influence on the content of hexoses associated with proteins and on the electrophoretic distribution of blood serum glycoproteins with the exception of the fraction of γ-glycoproteins whose level tends to decrease.

Plasma glycoproteins in diseases of the hemopoietic system

A total of 60 patients with various diseases of the hemopoietic system were investigated. The levels of plasma proteins, neuraminic acid, protein-bound hexose, seromucoid and neuraminic acid in seromucoid were determined. Parallelism in the behaviour of constituents of the carbohydrate complex was observed. The highest values of neuraminic acid, hexose, and seromucoid were found in the acute phase of lymphogranulomatosis and myelosis. In lymphatic leukemia, on the other hand, the level of neuraminic acid was much lower. The level of neuraminic acid in plasma seromucoid was found to be especially high in Hodgkin's disease. It may be supposed that the shift in the level of seromucoid is due to the increase in the amount of the carbohydrate component rather than of the protein component. It was found that when the patients were treated with steroids or cytostatic drugs, the level of plasma glycoproteins decreased. We consider that assays of neuraminic acid and seromucoid are more reliable than those of hexose for detecting changes in glycoproteins.

METABOLIC EFFECTS OF GLUCAGON IN THE PERFUSED RAT HEART.

The effect of glucagon on glycogenolysis and the utilization of acetate-2-C14 and glucose-U-C14 was studied in the isolated perfused rat heart. Significant effects of glucagon were obtained with a concentration of 5 µg/ml. Glucagon increased the uptake and oxidation to CO2 of glucose-U-C14 and acetate-2-C14 by 300 and 50%, respectively. The cardiac glycogen content fell to 60% of initial levels in 5 min and then remained constant. Lactate production reached a peak 30 sec after perfusion with glucagon, reflecting the early rapid glycogenolysis, and then fell to a constant rate within 5 min. Steady-state levels of hexose or triose phosphates were increased 300% at a time when glycogen levels had reached a plateau, indicating an increased rate of glucose phosphorylation, after the initial phase of rapid glycogenolysis, despite elevated levels of glucose 6-phosphate. Glucose transport was stimulated by glucagon although glucose entry remained the rate-limiting step of glucose uptake since no free intracellular glucose was detected. The increased fuel utilization produced by glucagon is shown to be dissociated from the glycogenolytic effect and is probably a consequence of the increased work of the heart. The effects of glucagon on the perfused rat heart are identical to those of epinephrine.

Studies in vivo on hexose metabolism in Dictyostelium discoideum

During differentiation of D. discoideum, the intracellular concentrations of glucose and UDPG change, peaking at the culmination stage. Experiments using 1- and 6-C 14-glucose have shown that the exogenous glucose concentration affects the relative rates of C 14O 2 evolution from 1- and 6-C 14-glucose. These studies have led to the conclusion that the changing hexose levels occurring during development also exert an influence on the pathways of hexose metabolism.

Serum Glycoprotein Levels During Wound Tissue Regeneration

Abstract The level of protein-bound hexoses was compared in several fractions of electrophoretically separated globulins in the sera of normal and wounded rats. Changes in the concentration of protein components which were not apparent from the amount of total protein of different fractions could be identified. Although wounding resulted in no change from the normal protein level of one α-globulin fraction, the protein-bound hexoses decreased significantly below the normal. In another α-globulin fraction from wounded animals, a parallel increase in both protein and hexose above the normal was observed. The total proteins in the β-globulin fraction were not affected by wounding, even though there was an appreciable increase in hexose in the wounded over the normal level. In spite of the marked decrease in the amount of protein in the γ-globulins of wounded rats, no significant difference in the hexoses associated with this fraction was observed. Other globulin fractions were unchanged during wound tissue regeneration.

Effect of insulin on structural sugars in adipose tissue.

Hexosamine and acid mucopolysaccharide concentrations were measured in the fat-free, dry residue (“stroma”) of epididymal adipose tissue from normal rats and from rats made obese by insulin. The hexosamine concentration was 6.81 ±0.267 (SE) jug/mg stroma over a wide range of body weights in normal rats. Adipose tissue from rats given insulin for from 7 to 28 days contained the same proportion of stroma as that from normal rats, but concentrations of hexosamine and acid mucopolysaccharides within the stroma were greatly reduced. Enzymatic digests of stroma on fractionation yielded evidence of hyaluronic acid, chondroitin sulfate and heparin. Of the 3 fractions, hyaluronic acid was reduced the most by insulin. Serum hexosamine and protein-bound hexose levels were lower, and seromucoid levels were higher, in rats given insulin. It appears, from these and other data cited, that insulin impairs the synthesis of certain structural sugars found in adipose tissue and serum. An increase in the rate of breakdown of...

The mucoprotein of the fat/plasma interface of cow's milk: I. Chemical and physical characterization

A mucoprotein isolated from the fat/plasma interface of cow's milk has been characterized. As analyzed by free-boundary electrophoresis, the mucoprotein was essentially homogeneous with respect to surface charge density. Chemically, it contained considerably higher levels of sialic acid, hexose, and hexosamine than any of the major proteins of milk. The strong tendency of this substance to aggregate in high gravitational fields was absent in sedimentation experiments using reduced centrifugal speeds.

魚肉の褐変に関する研究-XI

Sugar, phosphate, arginine, and lysine were analyzed to examine the effect of heat on their contents in flesh, and whether they have connection with browning of flesh by heat. The results obtained may be summarized as follow. Level of total acid-soluble hexose was decreased significantly by heat in browned flesh, but little change was seen in flesh which was not browned. On the other hand, change in level of total acid-soluble pentose gave no correlation with browning of flesh. Inorganic phosphorus in flesh of every species tested here were increased by heating, and seemed to be independent of browning of flesh, although inorganic phosphorus accelerates browning of amino-sugar system. Total and soluble arginine, and total lysine in flesh were decreased by heat not only in browned flesh but in unbrowned one, whereas soluble lysine was increased. However, extracts prepared from raw flesh lost a considerable amount of lysine and browned on heat treatment. These results suggest that the content of total acid-soluble hexose plays an important role as a limiting factor in the browning of flesh, and that lysine which occurs in soluble form in raw flesh possibly relates to browning to some extent.

Effect of Preslaughter Change to a Cold Environment on Characteristics of Pork Muscle

Market-weight swine were placed in cold water (0.5° C.) for 30–40 min. in an attempt to stimulate a severe environmental change. The extreme change in environment from warm to cold temperature decreased the initial muscle glycogen level with a resultant decrease in lactic acid concentration and an increase in color intensity of the chilled muscle. Water-binding capacity of the chilled muscle was not consistently affected. When the animals were held 3 hr. rather than 10–20 min. subsequent to treatment and prior to slaughter, there were no substantial changes in treatment response. Increased effects due to a 12-hr, holding period between treatment and slaughter were probably the result of a longer fasting period. The influence of rate of glycolysis and level of hexose monophosphates upon the water-binding capacity of the muscle have been discussed.

A study on correlations between C-reactive protein and certain other acute-phase reactants

The ceruloplasmin activity and levels of total sialic acid, seromucoid, and total glycoprotein hexoses were determined in 1,104 normal and pathologic sera with particular reference to the presence or absence of C-reactive protein. The concentrations of these acute-phase reactants generally increased with the intensity of the C-reactive protein reaction. The highest degree of correlation was between sialic acid and C-reactive protein and the lowest degree between total glycoprotein hexoses and C-reactive protein.