THE SEPARATION OF SIMPLE SUGARS BY CELLULOSE THIN-LAYER CHROMATOGRAPHY

Direct measurement of the lambda of the lumped constant of the deoxyglucose method in rat brain: determination of lambda and lumped constant from tissue glucose concentration or equilibrium brain/plasma distribution ratio for methylglucose

Steady-state distribution spaces of 2-[14C]deoxyglucose ([14C]DG), glucose, and 3-O-[14C]methylglucose at various concentrations of glucose in brain and plasma ranging from hypoglycemic to hyperglycemic levels have been determined by direct chemical analyses in the brains of conscious rats. The hexose concentrations were measured chemically in freeze-blown brain extracted with ethanol to avoid the degradation of acid-labile products of [14C]DG back to free [14C]DG that has been found to occur with the more commonly used perchloric acid extraction of brain. Corrections were also made for nonphosphorylatable, labeled products of [14C]DG found in the nonacidic fractions of the brain extracts, which were previously included with the assayed [14C]DG, and for the contribution of the hexose contents in the blood in the brain, which was found to be particularly critical for the determination of the glucose distribution space, especially in hypoglycemic states. From the measured contents of the hexoses in brain and plasma, the relationships of the tissue concentrations and distribution spaces of each of the hexoses and of the lambda (i.e., ratio of tissue distribution space of DG to that of glucose) of the DG method to the tissue glucose concentration were derived. The lambda was then quantitatively related to the measured equilibrium ratio for [14C]methylglucose over the full range of brain and plasma glucose levels. By combining these new data with the values for the lumped constant, the factor that converts the rate of DG phosphorylation to glucose phosphorylation, previously determined in rats over the same range of plasma glucose levels, the phosphorylation coefficient was calculated and the lumped constant graphed as a function of the measured distribution space in brain for [14C]methylglucose.

Metabolic stability of 3-O-methyl-D-glucose in brain and other tissues

3-O-Methyl-D-glucose (methylglucose) is often used to study blood-brain barrier transport and the distribution spaces of hexoses in brain. A critical requirement of this application is that it not be chemically converted in the tissues. Recent reports of phosphorylation of methylglucose by yeast and heart hexokinase have raised questions about its metabolic stability in brain. Therefore, we have re-examined this question by studying the metabolism of methylglucose by yeast hexokinase and rat brain homogenates in vitro and rat brain, heart, and liver in vivo. Commercial preparations of yeast hexokinase did convert methylglucose to acidic products, but only when the enzyme was present in very large amounts. Methylglucose was not phosphorylated by brain homogenates under conditions that converted 97% of [U-14C]glucose to ionic derivatives. When [14C]methylglucose, labeled in either the methyl or glucose moiety, was administered to rats by an intravenous pulse or a programmed infusion that maintained the arterial concentration constant and total 14C was extracted from the tissues 60 min later, 97-100% of the 14C in brain, greater than 99% of the 14C in plasma, and greater than 90% of that in heart and liver were recovered as unmetabolized [14C]methylglucose. Small amounts of 14C in brain (1-3%), heart (3-6%), and liver (4-7%) were recovered in acidic products. Plasma glucose levels ranging from hypoglycemia to hyperglycemia had little influence on the degree of this conversion. The distribution spaces for methylglucose were found to be 0.52 in brain and heart and 0.75 in liver.

Direct chemical measurement of the lambda of the lumped constant of the [14C]deoxyglucose method in rat brain: effects of arterial plasma glucose level on the distribution spaces of [14C]deoxyglucose and glucose and on lambda

The lumped constant in the operational equation of the 2-[14C]deoxyglucose (DG) method contains the factor lambda that represents the ratio of the steady-state tissue distribution spaces for [14C]DG and glucose. The lumped constant has been shown to vary with arterial plasma glucose concentration. Predictions based mainly on theoretical grounds have suggested that disproportionate changes in the distribution spaces for [14C]DG and glucose and in the value of lambda are responsible for these variations in the lumped constant. The influence of arterial plasma glucose concentration on the distribution spaces for DG and glucose and on lambda were, therefore, determined in the present studies by direct chemical measurements. The brain was maintained in steady states of delivery and metabolism of DG and glucose by programmed intravenous infusions of both hexoses designed to produce and maintain constant arterial concentrations. Hexose concentrations were assayed in acid extracts of arterial plasma and freeze-blown brain. Graded hyperglycemia up to 28 mM produced progressive decreases in the distribution spaces of both hexoses from their normoglycemic values (e.g., approximately -20% for glucose and -50% for DG at 28 mM). In contrast, graded hypoglycemia progressively reduced the distribution space for glucose and increased the space for [14C]DG. The values for lambda were comparatively stable in normoglycemic and hyperglycemic conditions but rose sharply (e.g., as much as 9-10-fold at 2 mM) in severe hypoglycemia.

Compared roles of glucose, galactose and fructose as glycogen precursors during the acute response to insulin in cultured rat foetal hepatocytes

1. The efficiency of the contribution of hexoses to basal- and stimulated-glycogenesis, when studied in cultured 18 day-old rat foetal hepatocytes in the presence of glucose, was as follows: galactose greater than glucose greater than fructose. 2. Glucose deprivation had opposite effects on the contributions of [14C]galactose (decreased) and [14C]fructose (increased) to glycogenesis, which occurred independently of insulin and were reversed by glucose concentrations as low as 30-100 microM. 3. The stimulation of glycogenesis by insulin measured with [14C]glucose (3.2-fold) was superior to that obtained with either [14C]galactose or [14C]fructose (2.7-fold in both cases), which revealed a specific beneficial effect of insulin on glucose contribution.

The structure of a novel polysaccharide isolated from Zymomonas mobilis determined by nuclear magnetic resonance spectroscopy

A novel polysaccharide has been observed in vivo by 13C nuclear magnetic resonance (NMR) spectroscopy of the gram-negative bacterium, Zymomonas mobilis. The polysaccharide, which was not removed from the Z. mobilis cell by washing with 0.86% saline, was extracted by mild acid treatment. The structure was elucidated by a combination of NMR techniques, including proton and proton-carbon two-dimensional methods. The structure was determined to be -alpha-fructofuranosyl-(2-1)-beta-fructofuranosyl-(2-6)-. The polysaccharide is unlike levan, a beta-(2-6)-fructose polymer which is produced by many bacteria, including Z.mobilis, when grown on sucrose. The polysaccharide isolated here is produced by cells cultured on glucose, fructose or sucrose.

Preparation, Characterization, and Microbial Degradation of Specifically Radiolabeled [ 14 C]Lignocelluloses from Marine and Freshwater Macrophytes

Specifically radiolabeled [ 14 C-lignin]lignocelluloses were prepared from the aquatic macrophytes Spartina alterniflora, Juncus roemerianus, Rhizophora mangle , and Carex walteriana by using [ 14 C]phenylalanine, [ 14 C]tyrosine, and [ 14 C]cinnamic acid as precursors. Specifically radiolabeled [ 14 C-polysaccharide]lignocelluloses were prepared by using [ 14 C]glucose as precursor. The rates of microbial degradation varied among [ 14 C-lignin]lignocelluloses labeled with different lignin precursors within the same plant species. To determine the causes of these differential rates, [ 14 C-lignin]lignocelluloses were thoroughly characterized for the distribution of radioactivity in nonlignin contaminants and within the lignin macromolecule. In herbaceous plants, significant amounts (8 to 24%) of radioactivity from [ 14 C]phenylalanine and [ 14 C]tyrosine were found associated with protein, although very little (3%) radioactivity from [ 14 C]cinnamic acid was associated with protein. Microbial degradation of radiolabeled protein resulted in overestimation of lignin degradation rates in lignocelluloses derived from herbaceous aquatic plants. Other differences in degradation rates among [ 14 C-lignin]lignocelluloses from the same plant species were attributable to differences in the amount of label being associated with ester-linked subunits of peripheral lignin. After acid hydrolysis of [ 14 C-polysaccharide]lignocelluloses, radioactivity was detected in several sugars, although most of the radioactivity was distributed between glucose and xylose. After 576 h of incubation with salt marsh sediments, 38% of the polysaccharide component and between 6 and 16% of the lignin component (depending on the precursor) of J. roemerianus lignocellulose was mineralized to 14 CO 2 ; during the same incubation period, 30% of the polysaccharide component and between 12 and 18% of the lignin component of S. alterniflora lignocellulose was mineralized.

Influence of vascular flow on amino acid transport across frog small intestine

1. The vascularly perfused intestine of the frogs, Rana ridibunda and R. pipiens, was used to investigate the transfer of the non-metabolized amono acids alpha-amino isobutyric acid (AIB) and 1-amino-cyclopentane-1-carboxylic acid (cycloleucine) across the intestinal epithelium from the lumen into the portal vein. 2. The steady-state rate of transfer of cycloleucine was significantly increased with increasing vascular flow rate, both in the presence and absence of Na in the fluid in the intestinal lumen, although at all flow rates the transfer was lower when the Na was replaced by K. The relatively high rate of transfer of cycloleucine seen at high rates of vascular flow when the luminal perfusate was free of Na was almost abolished when leucine was added to the lumen. 3. When the vascular flow is interrupted cycloleucine is taken up from the lumen and accumulates in the tissue. The accumulated amino acid can be measured during the subsequent wash-out when the vascular flow is resumed. The rates of transfer of accumulated cycloleucine as measured during subsequent wash-out were lower than those found at continuous flow; it is suggested that there is a limit to the amount of amino acid that the epithelial tissue can retain when the vascular flow is interrupted. A significant accumulation of cycloleucine occurs when Na is present in the lumen, but the accumulation is negligible when Na is replaced by K. 4. The unloading of the amino acids AIB and cycloleucine from the epithelium into the vasculature was investigated. The two amino acids showed markedly different kinetics of exit, that of AIB being monoexponential while that of cycloleucine was biexponential. Moreover, the rate of exit of cycloleucine was influenced by the presence of Na in the intestinal lumen, and by the rate of vascular perfusion. The apparent diffusion coefficients for the exit were smaller than those expected had unloading taken place by unobstructed free diffusion. 5. It is concluded that specific processes for exit from the epithelium play a significant role in amino acid transfer across the small intestine, and that the exit of AIB is more restricted than that of cycloleucine.

Metabolite levels during induction in the chloroplast and extrachloroplast compartments of spinach protoplasts

The light activation of photosynthesis has been investigated in spinach palisade cell protoplasts. (1) After a short induction period, maximal rates of photosynthesis are achieved. (2) [14C]Bicarbonate initially labels anionic compounds in the chloroplast and then in the extrachloroplast compartments. These pools saturate within 2-4 min and radioactivity accumulates mainly in sucrose in the extrachloroplast compartment, in starch and in cationic compounds. (3) Enzymic determinations were made of metabolite levels during the induction period in the chloroplast and extrachloroplast compartments. There is no general build-up of intermediates. Perturbations of individual intermediates occurred, consistent with the activation of specific enzymes. (4) It is suggested that fructose-1,6-bisphosphatase and ribulose-1,5-bisphosphate carboxylase may limit flux in the Calvin cycle during induction. (5) The onset of sucrose synthesis is not accompanied by accumulation of intermediates in the cytosol. It is suggested that sucrose phosphate synthase or sucrose phosphate phosphatase is activated. (6) Measurements of metabolites in whole leaves during a 24 h illumination cycle confirmed that substrates are not depleted during the dark period, and that the onset of photosynthesis is not accompanied by a rise in intermediate levels. (7) It is concluded that the causes of the induction lag in protoplasts can differ from those in isolated chloroplasts.

Reliable sampling method for analysis of the ecology of the human alimentary tract

An intubation method has been developed that allows removal of a sample of human intestinal fluid within a short period of time, that avoids contamination, and that minimizes exposure of the sample to air. Preliminary results obtained with this method have shown that the stomach and duodenum are essentially sterile and that the bacterial population present in the remainder of the small intestine is similar to that described by previous workers except that Veillonella species were encountered frequently and Haemophilus species were also detected in the lower jejunum and ileum of some individuals.

The role of brush border enzymes in tubular reabsorption of disaccharides: a microperfusion study in rat kidney

Renal tubular reabsorption of maltose, sucrose and lactose were studied in vivo et situ by continuous microperfusion of single proximal convolutions of rat kidney. The 14C-label of maltose (2.5 mmol/l) was removed from the lumen of the proximal tubule at about the same rate as found for glucose. Maltose reabsorption was completely inhibited in presence of 30 mmol/l glucose or of 0.1 mmol/l phlorizin. Chemical analysis of the samples showed a complete conversion of maltose into glucose within a perfusion distance of 2 mm. It is concluded from these results that within the tubular lumen maltose is split very rapidly by a brush border glucosidase. The short half time of this process permits the breakdown product glucose to be almost completely reabsorbed subsequently within the proximal tubule. In contrast, sucrose and lactose were neither split nor reabsorbed by the tubule brush border.

Steady-state metabolism and transport of D-glucose by rat small intestine in vitro

1. Conditions of incubation of everted sacs of rat small intestine were selected to ensure that absorption of d-glucose by mucosal tissue from the incubation medium, intracellular metabolism of the absorbed glucose and transport of glucose through the intact intestinal tissue proceeded linearly with respect to time of incubation within stated time intervals. 2. Under these experimental conditions, steady intracellular concentrations of glucose and lactate were demonstrated. 3. The quantitative translocational and metabolic fate of absorbed glucose was determined under these steady-state conditions. About 25% of glucose absorbed from the external mucosal solution was accumulated (temporarily) within mucosal tissue and about 25% transported through the intact tissue into the external serosal solution; the remainder (about 50%) of the absorbed glucose was metabolized, 90% to lactate and 10% to CO(2). Concomitant respiration rates were comparable with those reported for several other preparations of intestine and were stoicheiometrically in excess of the O(2) metabolism required to account for the production of CO(2) from the absorbed glucose. 4. Water transport through the everted sacs proceeded at an optimum rate under the experimental conditions selected. 5. Some other observations are recorded which influenced the design of the experiments and the interpretation of results; these include the initial physiological state of the animal, the anaesthetic used and the ionic composition of the incubation medium.

Cell enlargement and sugar accumulation in the gynaecium of the glasshouse carnation (Dianthus caryophyllus L.) induced by ethylene

Histological examination of the ovary walls from ethylene-treated cut flowering stems of the carnation showed that the cells had enlarged and this appeared to account for the increased growth of the ovary which follows ethylene treatment of this flower. Sugar analyses of the flower parts indicated that growth of the ovary was accompanied by an increase in the ratio of sucrose to reducing sugars in the petals and ovary, and a net increase in sugars in the ovary. A sugar, tentatively identified as xylose, increased in the petals after ethylene treatment. Nitrogen, phosphorus and potassium contents of the ovary also increased after the ethylene treatment. The results, consistent with the hypothesis that sucrose is translocated in response to ethylene, are discussed in relation to previous work relating to the involvement of ethylene in flower senescence.

Studies of normal and nephritic rat glomerular basement membrane

Solubilization of the normal glomerular basement membrane with various solvents revealed that the material is held together by hydrogen and disulfide linkages as well as ionic salt bridges which ionize at around pH 10.0. Pronase digestion indicated that differences in susceptibility to enzyme digestion exist between normal and nephritic membrane. Titration of a urea-insoluble material indicated that some alteration must have taken place in the association between various components of the nephritic basement membrane. Chemical analysis of alkali-solubilized fractions suggested that greater alkali susceptibility of the nephritic material may be present. A collagen-like material resembling both tendon and dog basement membrane collagen in its amino acid composition was isolated. It contained 10% hexose, but in addition to glucose and galactose, mannose was also detected. A glycopeptide fraction obtained by pronase and collagenase digestion has a carbohydrate composition similar to the collagen-like material above. These substances probably represent incompletely digested fragments of the basement membrane.

Differential labeling of glycerol moieties of phospholipids and triacylglycerols of cultured mammalian cells by [U-14 C] glucose

Rabbit liver cells, in which fatty acid synthesis was suppressed by the rabbit serum component of the medium, were grown through 8- to 120-fold increases in cell numbers and mass of cell lipid in the presence of [U-14 C]-glucose. Triacylglycerols, phosphatidylcholine, and phosphatidylethanolamine were isolated from the total cell lipid and deacylated. Carbons 1 and 3 of the glycerol from the triacylglycerols and the no. 1 glycerol carbons of the two deacylated phospholids were oxidized by periodate and isolated as the dimedon derivative of formaldehyde. The specific activities of the glycerol carbons indicated that 58, 44, and 37 percent of the glycerol of the triacylglycerols. phosphatidylcholine, and phosphatidylethanolamine, respectively, were derived from the glucose of the medium. An additional 8 percent and 1-2 percent of the glycerol of each lipid was derived, respectively, from [U-14 C] glycerol and U14C-labeled amino acids added to the medium. In agreement with an experiment with albumin-bound [9,10- minus 3H]-oleic acid, and with smilar earlier experiments, it appears likely that appriacylglycerols originated from serum lipoproteins, or their partial hydrolysis products. An appreciable part of the ethanolamine of the cells' phosphatidylethanolamine originated from exogenous U- minus 14 C-labeled amino acids. Phosphatidyl-ethanolamine, however, was not a primary source of phosphatidylcholine. Labeling of the fatty acids of triacylglycerols and phospholipids by radioactive glucose, glycerol and amino acids was negligible.

Bacterial degradation of streptococcal glucans

Several strains of bacteria were isolated which have the ability to use the polyglucan polymers produced by four strains of Streptococcus mutans as a sole source of carbon and energy for growth requirements. This study shows that the enzyme system responsible for the degradation of the polyglucan is extracellular in nature.

Phenotypes of pleiotropic-negative sporulation mutants of Bacillus subtilis

The phenotypic properties of representatives of the five genetic classes of pleiotropic-negative sporulation mutants have been investigated. Protease production, alkaline and neutral proteases, was curtailed in spoA mutants, but the remainder of mutant classes produced both proteases, albeit at reduced levels. The spoA and spoB mutants plaqued phi2 and phi15 at high efficiency, but the efficiency of plating of these phages on spoE, spoF, and spoH mutants was drastically reduced. Antibiotic was produced by the spoH mutants and to a degree by some spoF mutants, but the other classes did not produce detectable activity. The spoA mutants were less responsive to catabolite repression of histidase synthesis by glucose than was the wild type. Severe catabolite repression could be induced in spoA mutants by amino acid limitation, suggesting that the relaxation of catabolite repression observed is not due to a defect in the mechanism of catabolite repression. Although others have shown a perturbation in cytochrome regulation in spoA and spoB mutants, the primary dehydrogenases, succinate dehydrogenase and reduced nicotinamide adenine dinucleotide dehydrogenase, leading to these cytochromes are unimpaired in all mutant classes. A comparison of the structural components of cell walls and membranes of spoA and the wild type is made. The pleiotropic phenotypes of these mutants are discussed.

Chemical and serological relationships between the heteropolysaccharides of Mycobacterium tuberculosis and Mycobacterium kansasii

The identity of a heteropolysaccharide from cell walls of Mycobacterium tuberculosis H37Ra with Seibert's tuberculopolysaccharide I was demonstrated by thin-layer chromatography, chemical analysis, and antigenic tests. The polysaccharide of M. kansasii was shown to be identical with that of M. tuberculosis. Defatted cells were disintegrated by ultrasonic treatment in the presence of glass beads; cell walls were obtained by differential ultracentrifugation. Ethyl alcohol-precipitated carbohydrate extracts were analyzed for protein and nucleic acid; these impurities were removed. Tuberculopolysaccharide I from the mycobacterial culture filtrate is probably derived from a lipopolysaccharide of the cell wall, which is partially removed by chloroform in the intact state. Alkaline extraction releases additional polysaccharide, in varying degrees of association with cell wall murein.