Incorporation Of 14C-glucose Research Articles

The effect of glycerol and other intermediates on the incorporation of 14C-fructose and 14C-glucose to hepatic triglyceride

Mature male rats were given, orally, 14C-fructose either alone or in conjunction with dihydroxyacetone, glyceraldehyde, or glycerol. Glycerol was also administered with 14C-glucose in a dose equimolar with fructose. After 2 hr the rats were killed and the liver triglyceride fraction was separated. Estimations of the degree of incorporation of 14C from the radioactive labeled carbohydrate into the glycerol and fatty acid moieties were carried out. Dihydroxyacetone and glyceraldehyde reduced the incorporation of 14C-fructose into hepatic triglyceride to approximately equal extents, suggesting that both trioses contribute equally to α-glycerophosphate formation. Glycerol, however, brought about a profound increase in the amount of fructose converted to triglyceride. This effect of glycerol was not apparent to any measurable extent on glucose incorporation into triglyceride and none of the intermediates affected the proportional distribution of radioactive counts between the fatty acid and glycerol moieties of the triglyceride after 14C-fructose administration.

Influence of acetate on glucose metabolism in the perfused hind-quarter of the rat.

The metabolism of U-14C-glucose and U-14C-acetate and the interaction between the two substrates in the perfused hind-quarter of the rat was studied. 5% of glucose taken up was oxidized to CO2, accounting for 15% of total oxygen consumption. Glucose was mainly incorporated into glycogen, while incorporation into lipids was negligible. Acetate did not significantly alter glucose uptake, 14C-glucose oxidation or the incorporation of 14C-glucose into glycogen and lipids. 45% of acetate taken up was oxidized to CO2, accounting for 20-25% of total oxygen consumption. Insulin did not affect acetate uptake but increased 14C-acetate oxidation. Oxygen consumption was slightly increased by simultaneous oxidation of glucose and acetate and in this situation the tissue content.of high-energy phosphate compounds was slightly elevated. It is concluded that only minor effects by acetate on glucose metabolism in the perfused skeletal muscle were found. The insignificant effects compared to previously reported studies on heart tissue (Neely and Morgan 1974) can be explained by differences in acetate metabolism between the two tissues.

A bioassay for NSILA-S in individual serum samples and its relationship to somatotropin.

A practical bioassay for the acid-ethanol soluble non-suppressible insulin-like activity (NSILA-S) of individual serum samples has been developed utilizing the incorporation of 14C-glucose into the lipid faction of isolated adipocytes. NSILA-S activity was correlated with somatotropin status. Thus, the mean potencies (+/-SD) relative to an extract of pooled normal human serum were: normal samples 1.11 +/- 0.14, acromegalic 2.91 +/- 0.72, and somatotropin deficient 0.13 +/- 0.06. This variation in NSILA-S was not due to variability in extraction recoveries. The within assay precision was 9% (coefficient of variation) and the between assay 23%. This method allows the simultaneous extraction and processing of relatively large numbers of samples, and compares favorably with other more complex methods. Because of the evidence that NSILA-S may be related to the somatomedins, the present method should provide a simpler and more reliable alternative to the cartilage bioassays used to measure somatomedin activity.

An automated radiometric microassay of fungal growth: quantitation of growth of T. mentagrophytes.

An automated radiometric microassay of the growth of Trichophyton mentagrophytes and other filamentous fungi is described. The assay is based upon the incorporation of 14C(U) glucose into the organism. Fractionation studies indicate that 73% of the label is found in trichloroacetic acid-insoluble macromolecular components of the mycelium. Incorporation of label directly correlated with growth as estimated by visual scoring of turbidity and as recorded in photomicrographs. Incorporation of 14C(U) glucose delineated a lag, exponential and stationary or plateau phase of growth. These phases could be completely inhibited by the antifungal agent tolnaftate. It was concluded that the growth of filamentous fungi can be successfully monitored by the radiometric method described. Moreover, this method is sensitive, accurate, reproducible, rapid and free of the variability inherent in many traditional estimates growth.

Diapause hormone action in silkworm ovaries incubated in vitro; 14C-trehalose incorporation into glycogen

Developing ovaries from pharate adults of the silkworm, Bombyx mori, were incubated in a medium containing 14C-trehalose or 14C-glucose, and the effects of diapause hormone on the incorporation of these isotopes into ovary glycogen were studied. The rates of incorporation of 14C-trehalose remained unchanged in ovaries incubated for 36 hr when the medium was renewed at intervals of 12 hr, and showed saturation kinetics against the concentration of the sugar in the medium, giving apparent Km values of 6·0 mM for trehalose. There was no difference in 14C-glucose incorporation by ovaries grown in the presence (+SG) and absence (−SG) of the suboesophageal ganglion (SG). However, when 14C-trehalose was used as a substrate for glycogen synthesis, there was a marked difference in the incorporation between them, i.e. the incorporation was more than 60 per cent higher in +SG ovaries than that in −SG ovaries. Increased incorporation of 14C-trehalose was also observed in ovaries from SG-removed pharate adults which received an injection of diapause hormone preparations. Maximum stimulation rates (about twofold) appeared 36 hr after the injection. Further, comparable effects on 14C-trehalose incorporation were observed in ovaries which were incubated with diapause hormone preparations added in vitro. These data are discussed in relation to the hormonal regulation of trehalase activity in ovaries.

Synergistic action of prolactin and androgen on the cloacal glands of the newt

1. 1. Injections of prolactin in combination with testosterone propionate (TP) to hypophysectomized or hypophysectomized and castrated newts enhanced the development of tubular cells and secretion in the cloacal gland. 2. 2. Incorporation of 14C-glucose into the TCA-insoluble materials in the lateral gland was stimulated by prolactin when TP was administered simultaneously. Other pituitary hormones (FSH, LH and GH) did not exhibit such a synergistic action. 3. 3. Synthesis of acid mucopolysaccharides in the lateral gland was stimulated much more by prolactin and TP than prolactin or TP alone.

Glycogen metabolism in muscle: Its circadian and seasonal variations

The glycogen content of mice diaphragm and 14C-glucose incorporation into glycogen was studied around the clock at 4-hr intervals. It was found that glycogen content presents a circadian rhythm with a peak value around 4 hr; this rhythm was reproduced in four different months, but with changes both in the absolute values and in the range of oscillation around the 24-hr mean value. Although labeled glucose incorporation exhibited a circadian variation as well, its peak value was 180° out of phase compared with the glycogen rhythm. When the animals were submitted to a 29-hr fasting, the glycogen-24 hr-variation was still present, with similar oscillation around the mean. However, the absolute glycogen values were one-third as high as the ones obtained in the control animals. Our results suggest that the rhythm of glycogen content is due, at least partly, to the circadian variation of its synthesis. Furthermore, food intake is not the main factor responsible for the above mentioned rhythm.

CARBOHYDRATE‐INDUCED LIPOGENESIS IN THE HUMANPLACENTA OF NORMAL AND DIABETIC PREGNANCIES

Using in vitro incubation, human placental slices have been shown to synthesize lipid from 14-C fructose, but to a lesser extent than from 14-C glucose. Diabetic placentae did not incorporate more of either sugar into lipid than did placentae from normal pregnancies; nor did insulin in the incubation medium enhance lipogenesis. There was a correlation between the extent of incorporation of 14-C fructose and 14-C glucose into triglyceride, suggesting a linked enzyme system for phosphorylation of the two hexoses.

The Mode of Action of Pronamide

Pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide] inhibited root and shoot growth, but had little effect on the germination of oat (Avena sativaL.) or cucumber (Cucumis sativusL.), and sprouting of quackgrass [Agropyron repens(L.) Beauv.] buds. Root growth was more sensitive than shoot growth. Pronamide decreased the longitudinal growth rate and caused radial enlargement in the elongation region of the roots of oat seedlings within 4 hr. Dry weights of the swollen root tips increased 6% over the controls after 4 hr. Pronamide stopped the growth of established oat plants within 24 hr when added to nutrient culture medium. It caused a slight increase in86Rb uptake by excised oat roots. Pronamide stopped normal mitosis in treated oat roots within 0.5 hr. Examination of treated root tips under a microscope showed numerous cells in arrested metaphase, c-pairs, multinucleate cells, polyploidy and swollen and misshapen nuclei. Incorporation of14C-glucose into oat root cell walls and14C-leucine into protein were increased by 26 and 20% respectively, following 4-hr incubations in pronamide. The primary mode of action of pronamide is mitotic poisoning.

Estrogen-Induced Uterine Responses and Growth: Relationship to Receptor Estrogen Binding by Uterine Nuclei11

The relationship between estrogen receptor(R) binding by uterine nuclei and uterotrophic responses was examined. Immature rats received a single injection of estradiol (E2) or estriol (E3) and the following parameters were measured: accumulation and retention of the estrogen receptor by the nuceus of uterine cells; incorporation of 14C-glucose into CO2 lipid, protein and RNA; RNA polymerase activity; water imbibition and increased dry weight. E2 and E3 were of equal potency with regard to the rapid accumulation of R by the nucleus but differed with respect to long term retention of R. The concentrations of nuclear RE2 and RE3 complexes were equivalent between 1 and 3 hr after estrogen injection; however, by 6 hr RE2 remained significantly elevated while RE3 levels had fallen to control values. E2 and E3 were also of equal potency with respect to the stimulation of enhanced glucose utilization, water imbibition, the incorporation of 14C-glucose into lipid, protein and RNA 3 hours following an injection of the hormone. Likewise the activity of RNA polymerase was equally stimulated by E2 and E3 3 hr after injection. Thus all early uterotropic responses (0-3 hrs) that were measured were equally stimulated by E2 and E3. However, E3 failed to stimulate true uterine growth (increase dry weight 24 hr after injection), whereas E2 produced a significant stimulation of true uterine growth. These data suggest that the RE complex is capable of stimulating early uterotrohic events regardless of which estrogen is present; however, in order to produce true uterine growth the RE complex must be retained in the nucleus for long periods of time. This proposal was tested by the administration of repetitive injections of E3. This treatment resulted in an increase in dry weight that was equivalent to the growth that was produced by repetitive injections of E2. These results demonstrate that E2 and E3 elicit early uterotrophic responses with equal facility following a single injection but that only E2 causes true uterine growth. The ability of E2 to stimulate true uterine growth appears to be related to the time of residence of the RE complex in the nucleus.

Effect on dietary sucrose and fructose on the metabolism and lipid fractions in liver in the rat.

Male and female weanling rats were fed one of the following diets for 26 weeks: 60% (w/w) starch as control (59% of energy content); 20 (20), 40 (39) or 60% (59%) sucrose; or 20% (20%) fructose. With increasing levels of dietary sucrose the livers of male rats but not those of females, were progressively heavier. Livers of rats of both sexes showed progressively higher total lipid levels mainly as a result of high triglyceride levels. The 20% fructose diet produced the same effect as the 40% sucrose diet. The incorporation of 14C-glucose into liver lipids in vitro, and the production of 14CO2 were both depressed by sucrose and fructose feeding in both sexes.

Differences in the uptake of glucose and glycerol by Tieghemiomyces parasiticus in axenic culture

Tieghemiomyces parasiticus, a biotrophic haustorial mycoparasite, makes excellent axenic growth on a glycerol – casein hydrolysate medium, while growth on a glucose – casein hydrolysate medium is equivalent to that of a control medium containing only the nitrogen source. A comparison of 14C-glucose and 14C-glycerol uptake indicates these substrates enter this mycoparasite at significantly different rates. Incorporation of 14C-glucose is extremely slow and limited, while 14C-glycerol incorporation is very rapid. Excellent axenic growth of this mycoparasite occurs when a glucose – casein hydrolysate medium is supplemented with the surface-active agent Tween 80. These findings suggest that the inability of glucose to support growth results from the inability of this substrate to readily enter the vegetative hyphae of this mycoparasite when cultured axenically.

Effects of acetylcholine on incorporation of (14C)glucose into phosphatidylinositol and on phosphatidylinositol breakdown in subcellular fractions from cerebral cortex.

Effects of acetylcholine on incorporation of (14C)glucose into phosphatidylinositol and on phosphatidylinositol breakdown in subcellular fractions from cerebral cortex.

Incorporation of 14C-Glucose in the Polysaccharides of Various Body Parts of the Pond Snail Lymnaea Stagnalis as Affected By Starvation

In the present study the incorporation of label in the polysaccharides of various body parts of lettuce fed and of starved specimens of laboratory bred Lymnaea stagnalis was studied after the injection of 14 C-glucose in the haemocoel. These polysaccharides are mainly glycogen and, in the female organs, also galactogen. The t½-value for the injected label in the haemolymph of lettuce fed snails was larger than found in previous experiments with non-labelled glucose. It is suggested that this is caused by the presence of labelled intermediates in the haemolymph. It is demonstrated that 20 min after the injection of 14 C-glucose a maximum amount of label is incorporated in the tissues (in the total polysaccharides 28-32% of the amount of label removed from the haemolymph is recovered). Of the various body parts, the female accessory sex organs are most important in incorporating the label in polysaccharides (60-83% of the amount incorporated). In the prostate gland the lowest amount is incorporated. Of the other body parts, the muscle fraction is important, followed by the mantle and the digestive gland with the embedded ovotestis. In the heterogeneous rest fraction also some label is recovered. This means that the polysaccharide reserves (glycogen-in the mantle and the digestive gland/ovotestis-) of lettuce fed snails do not increase rapidly. After a starvation period of 14 days the total amount of label incorporated in polysaccharides of the body decreased significantly (with about 75%). It is demonstrated that this difference is mainly due to a decreased incorporation oflabel in the female accessory sex organs. In these organs the decrease is about 95%. It is concluded that the synthetic processes in the female organs (synthesis of galactogen, and also glycogen) are very important for the dynamics of the haemolymph-glucose. It is also concluded that the cessation of female reproductive activities is mainly responsible for the difference in the amount of 14 C-glucose removed from the haemolymph of fed and of starved snails. The incorporation of label in the polysaccharides of the female accessory sex organs decreased also when expressed per mg tissue wet weight, whereas it did not change significantly in the other body parts (the muscle fraction excluded). It is concluded that after a starvation period the polysaccharide synthesizing system in the female accessory sex organs is considerably inactivated, whereas this system in the other body parts is not much affected. Therefore, it is suggested that distinct regulatory mechanisms are operative for the control of the synthesis of polysaccharides in the female organs (mainly galactogen) and for the synthesis of polysaccharides in the other body parts (mainly glycogen).

The Influence of Root Knot Nematode, Meloidog Yne Javanica, On Photosynthesis and On Nutrient Demand By Roots of Tomato Plants

With an inoculum of 250 larvae, photosynthetic rate was less than in uninfected control plants but as inoculum level increased there was a rise and then a marked fall in photosynthesis. It is suggested that the complex nature of this relationship is due to the influence of several factors on photosynthesis. 14C-glucose incorporation into the roots was initially constant and only fell at the highest inoculum level (2,000 nematodes/plant). There was a marked decrease in 14CO2 incorporation with an inoculum of 250 nematodes compared with uninfected controls and a further decrease with 1,000 nematodes. Inoculation with 2,000 nematodes did not reduce 14CO2 incorporation further. The results do not support the hypothesis that creation of metabolic sinks in the roots, caused by the formation of syncytia and galls, have a major influence on top growth. The photosynthesis data indicate that inhibition of upward translocation of water and nutrients may be more important.

The control of chitin deposition by ecdysterone in larvae of Bombyx mori

The effect of ecdysterone on the deposition of chitin in Bombyx larvae was examined. The chitin content in the abdomen decreased following hormone treatment to a value half that of the controls. Studies with 14C-glucose revealed that whereas controls exhibited a gradual decrease in the rate of 14C-glucose incorporation into chitin, the administration of ecdysterone resulted in a rapid fall in the rate of incorporation followed by a rise until ecdysis occurred. Chitin catabolism was estimated at 0·11 mg chitin/hr, based on the chitin content and incorporation rates. A dual rôle is indicated for ecdysterone in chitin metabolism, namely the activation of both synthetic and lytic systems.

Role of acetylglucosamine in chitin synthesis in crayfish—I. Correlation of 14C-acetylglucosamine incorporation with stages of the molting cycle

1. 1. Incorporation of 14C-acetylglucosamine into the chitin of crayfish ( Orconectes obscurus) has been correlated with the stages of the molting cycle. 2. 2. Acetylglucosamine incorporation increased earlier in premolt (stage D 1″) and remained much higher than previously reported 14C-glucose incorporation. 3. 3. Acetylglucosamine incorporation was similar to previously reported glucose incorporation during intermolt and postmolt. 4. 4. Substantial amounts of breakdown products from the old cuticle are reincorporated into new cuticle. Over half of the radioactivity incorporated into postmolt chitin was reutilized in new chitin synthesis during the succeeding premolt. 5. 5. These data support a major role for acetylglucosamine in premolt chitin synthesis.

Inhibition of glucosyltransferase activity by antisera to known serotypes of Streptococcus mutans.

Using a recently developed assay for glucosyltransferase activity based on (14)C-glucose incorporation into an alcohol-insoluble polysaccharide, we were able to study inhibition by antibody of this enzyme activity. Rabbit antibody was relatively specific for the strain of Streptoccus mutans from which the enzyme was obtained. Absorption studies showed that neither removal of antibodies directed to dextran nor absorption with intact bacteria offset the enzyme-inhibitory capacity of these sera, whereas absorption with partially purified enzyme did result in removal of the inhibitory capacity.

Uptake of 14C-glucose by Botryodiplodia theobromae PAT and changes in its carbohydrate content during growth.

There is a rapid uptake of 14C-glucose and unlabelled glucose during the period of pigmentation of the mycelium of Botryodiplodia theobromae Pat. Incorporation of 14C-glucose into structural components of the mycelium started within 24 hours of incubation and progressively increased until the 14th day of growth. The mycelium contains glucose, isomaltose, and sucrose. There is a decrease in these carbohydrates during autolysis. Autolysis in B. theobromae occurs in an acid medium of pH 5.2.

Metabolism of intravenously injected 14C-glucose in weanling rats with hypothalamic obesity

Weanling male rats with bilateral lesions in the ventromedial hypothalamic nuclei (VMN) and sham-operated controls were injected intravenously with 14C-glucose to compare plasma glucose disappearance rates, and lipid and glycogen synthesis in liver, diaphragm, and epididymal adipose tissue. Removal of 14C-glucose from plasma was more than twice as rapid in VMN rats as in control animals despite comparable glucose levels. Incorporation of 14C-glucose into lipid was increased in all three tissues of VMN rats and was primarily due to an increase in fatty acid synthesis. Incorporation of label into glycogen by VMN rats was increased in adipose tissue but unchanged in liver and diaphragm. The results indicate that weanling VMN rats exhibit increase glucose utilization in vivo primarily directed toward lipogenesis. This finding is not restricted to adipose tissue but is present as well in liver and muscle.