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Catabolic pathways for glucose, glycerol and 6-phosphogluconate in Mycobacterium leprae grown in armadillo tissues.

With radioisotopes, it was shown that suspensions of Mycobacterium leprae oxidized glycerol, 6-phosphogluconate, glucose, glucose 6-phosphate, and, at a low rate, gluconate, to CO2. The incubation period in these experiments was usually 20 h, but after 140 h up to five times more glucose and gluconate had been converted to CO2. Studies with differentially labelled glucose indicated that glycolysis and the hexose monophosphate pathway were used for glucose dissimilation. Key enzymes of glycolysis, the hexose monophosphate pathway and glycerol catabolism were detected in cell-free extracts from purified M. Leprae, but phosphoketolase, Entner-Doudoroff pathway activity and gluconate kinase were absent. All these enzymes were present also in host-tissue, but biochemical evidence is presented which indicates that all enzymes detected in extracts from M. leprae were authentic bacterial enzymes. Additionally, they could all be detected in extracts of M. leprae prepared by treatment with NaOH in which host enzymes adsorbed to M. leprae are inactivated.

Animals↗

Physiological and biochemical changes accompanying the loss of mucoidy by Pseudomonas aeruginosa.

Pseudomonas aeruginosa M60, a mucoid strain, was grown in continuous culture (D 0.05 h-1) under ammonia limitation with glucose as the carbon source. Steady-state alginate production occurred for only 1-2 d under these conditions [qalginate 0.097 g alginate h-1 (g dry wt cells)-1], after which time the percentage of mucoid cells and the alginate concentration in the culture decreased in parallel and approached zero after approximately 10 d. These changes were accompanied by similar decreases in the activities of the alginate biosynthetic enzymes (represented by phosphomannomutase and GDP-mannose dehydrogenase) and by a large increase in the activity of the first enzyme of the 'external' non-phosphorylative pathway of glucose metabolism, glucose dehydrogenase. In contrast, the activities of other enzymes associated with this pathway (gluconate dehydrogenase, 2-ketogluconate kinase plus 2-ketogluconate-6-phosphate reductase) or with the 'internal' phosphorylative pathway of glucose metabolism (glucokinase and glucose-6-phosphate dehydrogenase) remained essentially unchanged. The loss of mucoidy and alginate production was accompanied by the appearance of low concentrations of intracellular polyhydroxyalkanoate (PHA) and of extracellular gluconate and 2-ketogluconate (partly at the expense of alginate production and partly as a result of increased glucose consumption). It is suggested that ammonia-limited, glucose-excess cultures of P. aeruginosa growing at low dilution rate are unable fully to regulate the rate at which glucose and/or its 'external' pathway metabolites are taken up by the cell, and therefore form copious amounts of alginate in order both to overcome the potentially deleterious osmotic effects of accumulating surplus intracellular metabolites and to consume the surplus ATP generated by the further oxidation of these metabolites. The loss of mucoidy invokes the use of an alternative, but analogous, strategy via which non-mucoid cells produce an osmotically inactive intracellular product (PHA) plus increased amounts of the extracellular metabolites gluconate and 2-ketogluconate via the low-energy-yielding and, under these conditions, largely dead-end 'external' metabolic pathway.

Alginates↗

Influence of Na+ and anions on the dimorphic transition of Candida albicans.

The effect of Na+ (Cl- or gluconate salt) on growth and dimorphic potential of the pathogenic yeast Candida albicans has been examined. Profiles of germ tube formation as a function of salt addition, pH and temperature indicated Na+ inhibition of germ tube outgrowth at high ambient pH (pH 8.0) which was exacerbated by replacement of Cl- with gluconate (as an impermeant analogue). At acidic pH (pH 5.5) and permissive temperature (37 degrees C), gluconate alone promoted the dimorphic transition. Rates of glucose-induced medium acidification and plasma membrane H(+)-ATPase activity have been measured to assess whether salt treatments could retard the cytoplasmic alkalinization known to precede germ tube formation. The precise site of Na+ action remains unclear but the anion effects may be interpreted in terms of anion-exchanger and channel activity acting to modulate cytosolic pH.

Adenosine Triphosphatases↗

Inhibition of experimental nephrocalcinosis with a prostaglandin synthetase inhibitor.

Nephrocalcinosis was induced in a group of experimental rats by means of intraperitoneal injections of 10% calcium gluconate. Two further groups of rats were treated with indomethacin and flurbiprofen (Froben) before receiving the i.p. calcium gluconate, to study the effects of prostaglandin inhibition on the process of renal parenchymal calcification. Tissue calcification was studied by means of contact microradiography and histology. Quantitative calcium analysis was by means of energy dispersive analysis of X-rays (EDAX). There was a marked inhibition of cortical nephrocalcinosis and a significantly reduced calcium concentration (P less than 0.005) in the animals treated with a prostaglandin inhibitor compared with the animals given i.p. calcium gluconate alone. This study suggests that prostaglandins are involved in the process of renal parenchymal calcification and may be aetiologically significant in the pathogenesis of stone formation.

Animals↗

Influence of chloride concentration and pH on the 36Cl efflux from depolarized skeletal muscle of Rana temporaria.

1. 36Cl- efflux rates were measured in depolarized fibre bundles (predominantly fast fibres) from m. semitendinosus of Rana temporaria in order to investigate the influence of chloride concentration (20-400 mM) and external pH (pHo, 5.5-11.6) on chloride self-exchange. Usually, the bundles were depolarized to a membrane potential of virtually zero ([Cl-]i = [Cl-]o = [Cl-]) in 140 mM-K+ and 20 mM-Cl- combined with either 60 mM-SO4(2-) (+52 mM-sucrose) or 120 mM-methyl sulphate, gluconate or glucuronate. Various values of [Cl-] were obtained by adding KCl to the medium, keeping constant the concentration of relatively impermeant solutes and thus the fibre volume. 2. The chloride permeability, PCl, at pH 7.5 decreased with increasing [Cl-] above 50 mM. At [Cl-] less than 50 mM, PCl was about 4 X 10(-6) cm s-1. 3. PCl at pHo 7.5 and 5.6 was a hyperbolic function of [Cl-1] (greater than or equal to 50 mM), consistent with saturation kinetics of chloride self-exchange. 4. Methyl sulphate inhibited chloride self-exchange and may enter depolarized fibre membranes slowly. Comparison of PCl estimates in SO4(2-), gluconate, and glucuronate suggested that SO4(2-) and gluconate may interfere with chloride self-exchange at low [Cl-], and that glucuronate interferes the least. 5. A change from chloride equilibrium to an inward KCl gradient increased the 36Cl- efflux rate in acid media (pH less than 6.5) and decreased the efflux rate at pHo greater than or equal to 7. The effects were not due to changes of membrane potential and demonstrate a change of transport mode consistent with single-filing at high pH and dominant exchange diffusion at low pH. This result makes interpretation of the saturation kinetics difficult. 6. At constant [Cl-], PCl showed a bell-shaped dependence on pHo with a maximum around pH 8.5. The decrease of chloride permeability as the pH is decreased below 8.5 showed an apparent pK of about 7. PCl fell at very alkaline pH with an apparent pK of about 10. 7. The results are in agreement with previous observations of an external pH-sensitive control of PCl (pK approximately 7) and suggest that, in conditions close to chloride equilibrium, this control includes a transition between a dominant conductive channel conformation at high pH and a dominant non-conductive conformation at low pH.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Escherichia coli F-18 and E. coli K-12 eda mutants do not colonize the streptomycin-treated mouse large intestine.

The Escherichia coli human fecal isolates F-18 and K-12 are excellent colonizers of the streptomycin-treated mouse intestine. E. coli F-18 and E. coli K-12 eda mutants (unable to utilize glucuronate, galacturonate, and gluconate) were constructed by insertional mutagenesis. Neither the E. coli F-18 eda nor the E. coli K-12 eda mutant was able to colonize the streptomycin-treated mouse intestine, whether they were fed to mice together with their respective parental strains or alone. Complementation of the eda mutants with pTC190 (containing a functional E. coli K-12 eda gene) completely restored the colonization ability of both eda mutants. Relative to their parental strains, the E. coli F-18 eda mutant and the E. coli K-12 eda mutant grew poorly in cecal mucus isolated from mice fed either normal mouse chow or a synthetic diet containing sucrose as the sole carbon source, yet the mutants and parental strains demonstrated identical growth rates in minimal medium with glucose as the carbon source. E. coli F-18 edd eda and E. coli K-12 edd eda double mutants colonized the streptomycin-treated intestine when fed to mice alone; however, when fed simultaneously with their respective parental strains, they were poor colonizers. Since the edd gene is involved only in gluconate metabolism via the Entner-Doudoroff pathway, these results implicate the utilization of gluconate and the Entner-Doudoroff pathway as important elements in E. coli colonization of the streptomycin-treated mouse large intestine.

Animals↗

Mouse intestine selects nonmotile flhDC mutants of Escherichia coli MG1655 with increased colonizing ability and better utilization of carbon sources.

D-gluconate which is primarily catabolized via the Entner-Doudoroff (ED) pathway, has been implicated as being important for colonization of the streptomycin-treated mouse large intestine by Escherichia coli MG1655, a human commensal strain. In the present study, we report that an MG1655 Deltaedd mutant defective in the ED pathway grows poorly not only on gluconate as a sole carbon source but on a number of other sugars previously implicated as being important for colonization, including L-fucose, D-gluconate, D-glucuronate, N-acetyl-D-glucosamine, D-mannose, and D-ribose. Furthermore, we show that the mouse intestine selects mutants of MG1655 Deltaedd and wild-type MG1655 that have improved mouse intestine-colonizing ability and grow 15 to 30% faster on the aforementioned sugars. The mutants of MG1655 Deltaedd and wild-type MG1655 selected by the intestine are shown to be nonmotile and to have deletions in the flhDC operon, which encodes the master regulator of flagellar biosynthesis. Finally, we show that DeltaflhDC mutants of wild-type MG1655 and MG1655 Deltaedd constructed in the laboratory act identically to those selected by the intestine; i.e., they grow better than their respective parents on sugars as sole carbon sources and are better colonizers of the mouse intestine.

Animals↗

Induction and regulation of a nicotinamide adenine dinucleotide-specific 6-phosphogluconate dehydrogenase in Streptococcus faecalis.

Streptococcus faecalis grown with glucose as the primary energy source contains a single, nicotinamide adenine dinucleotide phosphate (NADP)-specific 6-phosphogluconate dehydrogenase. Extracts of gluconate-adapted cells, however, exhibited 6-phosphogluconate dehydrogenase activity with either NADP or nicotinamide adenine dinucleotide (NAD). This was shown to be due to the presence of separate enzymes in gluconate-adapted cells. Although both enzymes catalyzed the oxidative decarboxylation of 6-phosphogluconate, they differed from one another with respect to their coenzyme specificity, molecular weight, pH optimum, K(m) values for substrate and coenzyme, and electrophoretic mobility in starch gels. The two enzymes also differed in their response to certain effector ligands. The NADP-linked enzyme was specifically inhibited by fructose-1,6-diphosphate, but was insensitive to adenosine triphosphate (ATP) and certain other nucleotides. The NAD-specific enzyme, in contrast, was insensitive to fructose-1,6-diphosphate, but was inhibited by ATP. The available data suggest that the NAD enzyme is involved primarily in the catabolism of gluconate, whereas the NADP enzyme appears to function in the production of reducing equivalents (NADPH) for use in various reductive biosynthetic reactions.

Adenosine Triphosphate↗

Novel pathway for alcoholic fermentation of delta-gluconolactone in the yeast Saccharomyces bulderi.

Under anaerobic conditions, the yeast Saccharomyces bulderi rapidly ferments delta-gluconolactone to ethanol and carbon dioxide. We propose that a novel pathway for delta-gluconolactone fermentation operates in this yeast. In this pathway, delta-gluconolactone is first reduced to glucose via an NADPH-dependent glucose dehydrogenase (EC 1.1.1.47). After phosphorylation, half of the glucose is metabolized via the pentose phosphate pathway, yielding the NADPH required for the glucose-dehydrogenase reaction. The remaining half of the glucose is dissimilated via glycolysis. Involvement of this novel pathway in delta-gluconolactone fermentation in S. bulderi is supported by several experimental observations. (i) Fermentation of delta-gluconolactone and gluconate occurred only at low pH values, at which a substantial fraction of the substrate is present as delta-gluconolactone. Unlike gluconate, the latter compound is a substrate for glucose dehydrogenase. (ii) High activities of an NADP(+)-dependent glucose dehydrogenase were detected in cell extracts of anaerobic, delta-gluconolactone-grown cultures, but activity of this enzyme was not detected in glucose-grown cells. Gluconate kinase activity in cell extracts was negligible. (iii) During anaerobic growth on delta-gluconolactone, CO(2) production exceeded ethanol production by 35%, indicating that pyruvate decarboxylation was not the sole source of CO(2). (iv) Levels of the pentose phosphate pathway enzymes were 10-fold higher in delta-gluconolactone-grown anaerobic cultures than in glucose-grown cultures, consistent with the proposed involvement of this pathway as a primary dissimilatory route in delta-gluconolactone metabolism.

Anaerobiosis↗

Effect of growth temperature on the accumulation of glucose-oxidation products in Pseudomonas fluorescens.

The effect of the growth temperature, on the accumulation of glucose-oxidation products, was examined in aerated cultures with carbon excess in two strains of Pseudomonas fluorescens. At low growth temperatures (0 and 5 degrees C), 2-ketogluconate (KG) a-cumulated in the medium as the major oxidation product of glucose (up to 70%) before further metabolism. As the growth temperature was increased, the amount of 2-KG found to accumulate in the medium from glucose oxidation decreased. At a growth temperature of 20 degrees C, up to 25% of the glucose originally added accumulated in the medium as 2-KG. At the optimum growth temperature of 30 degrees C or above, no 2-KG was detected at any time during growth with glucose. Similar results were obtained when gluconate was used as the sole carbon and energy source. The results demonstrated a differential effect of growth temperature on the accumulation of oxidation products from glucose and gluconate. At low growth temperatures the major route for the catabolism of glucose and gluconate was the direct oxidative non-phosphorylated pathway.

Gluconates↗

Isolation and characterization of catabolite repression-resistant mutants of Escherichia coli.

A method has been developed for the isolation of Escherichia coli mutants which are resistant to catabolic repression. The method is based on the fact that a mixture of glucose and gluconate inhibits the development of chemotactic motility in the wild type, but not in the mutants. A motile E. coli strain was mutagenized and grown in glucose and gluconate. Mutants which were able to swim into a tube containing a chemotactic attractant (aspartic acid) were isolated. Most of these mutants were able to produce beta-galactosidase in the presence of glucose and gluconate and were normal in their ability to degrade adenosine 3',5-cyclic monophosphate. Some of these mutants were defective in the glucose phosphotransferase system.

3',5'-Cyclic-AMP Phosphodiesterases↗

Inhibition of alpha-adrenergic responses in the rat liver by lipophilic K+ channel blockers or depolarizing Cl- gradients. Evidence for a potential-sensitive step in the signal transduction path.

To study the role of K+ channels and membrane potential in alpha-adrenergic responses of the rat liver, lipophilic K+ channel blockers quinidine and 4-aminopyridine were used or external Cl- was replaced with gluconate, an impermeant ion. Glucose release, O2 uptake, portal pressure, and K+ flux were measured in the isolated perfused liver. The alpha-agonist phenylephrine caused biphasic changes in each parameter, a fast transient followed by sustained elevated responses. Infusion of 5 mM 4-aminopyridine, 0.1 mM quinidine, or gluconate prior to phenylephrine inhibited each parameter, with the greatest inhibition occurring during the second phase. A similar pattern was seen with 2 mM EGTA. This contrasts with the full inhibition of all responses following exposure to the alpha-antagonist phentolamine. Infusion of each inhibitor at the peak of the sustained phase inhibited all responses. Phenylephrine-stimulated release of K+ was augmented in the presence of EGTA and was inhibited by 4-aminopyridine or quinidine. In contrast, beta-adrenergic stimulation of glucose release and K+ flux were not affected by the K+ channel blockers. Phenylephrine-stimulated glucose release from hepatocyte suspensions decreased by about 50% in the presence of 4-aminopyridine, EGTA, or gluconate. The results are discussed in terms of a potential role for K+ channels in alpha-adrenergic signal transduction in the liver.

4-Aminopyridine↗

Chloride is required for fluid transport by the rabbit corneal endothelium.

The role of chloride in fluid transport of the rabbit corneal endothelium was examined by measuring changes in corneal thickness following ion substitutions or addition of ion transport inhibitors in media superfusing the isolated tissue. Normal fluid transport is indicated by maintenance of constant thickness in a fresh cornea or thinning (deturgescence) of a preswollen deepithelialized cornea to its initial thickness at approximately 40 microns/h. These patterns are seen when tissues are superfused with HCO(3-)-Ringer containing 114 mM Cl-. When Cl- was substituted with gluconate, glucuronate, or SO4(2-) fresh and preswollen corneas immediately thinned at greater than 150 microns/h to a value less than 300 microns and then began to swell at 30 microns/h to above their original thickness. Substitution of Cl- with NO3- or Br- had a negligible immediate thinning effect, but fresh corneas subsequently swelled and preswollen corneas failed to deturgesce fully. The rapid thinning (called a "downtransient") observed with gluconate, glucuronate, and SO4(2-) also occurred in these media when ion and fluid transport were completely inhibited with ouabain or stilbenes or by absence of HCO3-, indicating that the thinning results from osmotic gradients induced by ionic reflection coefficients different from that of Cl-. When the downstransient was avoided in deepithelialized corneas by preswelling with the same Cl(-)-free media on both sides of the cornea, corneas maintained a constant but swollen thickness in gluconate and in NO3- or Br- deturgesced slowly and incompletely; ouabain or stilbenes caused further swelling in all media. We conclude that absence of Cl- partially impairs fluid transport, most probably via its role in a Cl(-)-HCO3- exchanger which has been proposed in a recent model of endothelial fluid transport.

Animals↗

Chloride dependence of the HCO3 exit step in urinary acidification by the turtle bladder.

To characterize the efflux of HCO-3 across the basolateral membrane of the H+-secreting cells of the turtle bladder, we examined the effect of substitution of gluconate or methyl sulfate for Cl- on the rate of acidification (JH). JH was measured as the short-circuit current in bladders in which Na+ transport was abolished with 10(-4) M ouabain. In hemibladders bathed in normal Ringer solution (Cl- = 122 mM) JH was 44.9 microA. Substitution of the Cl- resulted in a marked reduction in JH (12.5 microA with gluconate and 7.5 microA with methyl sulfate). Addition of Cl- to the mucosal surface had no effect on JH. In contrast, serosal addition of Cl- restored JH to control. The apparent Km for Cl- in gluconate Ringer was 0.13 mM. Serosal furosemide (1 mM) inhibited JH by 55% in Cl- Ringer. We conclude that HCO-3 exit across the basolateral membrane of the H+-secreting cell occurs via a Cl-HCO3 exchanger that has a high affinity for chloride.

Animals↗

Transport characteristics of the apical anion exchanger of rabbit cortical collecting duct beta-cells.

To functionally characterize transport properties of the apical anion exchanger of rabbit beta-intercalated cells, the mean change in anion exchange activity, dpHi/dt (where pHi is intracellular pH), was measured in response to lumen Cl- replacement with gluconate in perfused cortical collecting ducts (CCDs). beta-Cell apical anion exchange was not affected by 15-min exposure to 0.2 mM lumen DIDS in the presence of 115 mM Cl-. In contrast, apical anion exchange was significantly inhibited by 0.1 mM lumen DIDS in the absence of Cl-. beta-Cell apical anion exchange was unchanged by 15 mM maleic anhydride, 10 mM phenylglyoxal, 0.2 mM niflumic acid, 1 mM edecrin, 1 mM furosemide, 1 mM probenecid, or 0.1 mM diphenylamine-2-carboxylate. However, beta-cell apical anion exchange was inhibited by alpha-cyano-4-hydroxycinnamic acid, with an IC50 of 2.4 mM. Substitution of either sulfate or gluconate for lumen Cl- resulted in a similar rate of alkalinization. Conversely, pHi was unchanged by substitution of sulfate for lumen gluconate, confirming the lack of transport of sulfate on the beta-cell apical anion exchanger. Taken together, the results demonstrate a distinct "fingerprint" of the rabbit CCD beta-cell apical anion exchanger that is unlike that of other known anion exchangers.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

Influence of dietary copper on the survival of Drosophila.

The life span of Drosophila melanogaster was reduced when copper compounds were fed at concentrations of 1 X 10(-3) M or greater. Feeding lower concentrations of copper compounds failed to significantly change life span. A combination of copper gluconate and gluconic acid increased the adult life span by 21.6%. We conclude that only an extraordinarily high dietary intake of copper would accelerate senescence. Dietary gluconic acid retarded the normal age-related accumulation of copper in adult flies.

Animals↗

Digoxin reduces beta-adrenergic contractile response in rabbit hearts. Ca(2+)-dependent inhibition of adenylyl cyclase activity via Na+/Ca2+ exchange.

Whereas mobilization of intracellular Ca2+ stimulates neuronal adenylyl cyclase via Ca2+/calmodulin, mobilized Ca2+ directly inhibits adenylyl cyclase in other tissues. To determine the physiologic role of the Ca(2+)-dependent interaction between Na+/Ca2+ exchange and beta-adrenergic signal transduction in the intact heart, digoxin (0.3 mg/kg) was administered intravenously in rabbits. 30 min after the administration, digoxin impaired the peak left ventricular dP/dt response to dobutamine infusions by up to 38% as compared with control rabbits. This impairment was not caused by changes in either beta-adrenergic receptor number or in the functional activity of stimulatory guanine nucleotide-binding protein. It was associated with 33-36% reductions in basal and stimulated adenylyl cyclase activities. Animals treated with calcium gluconate (20 mg/kg/min for 30 min) also demonstrated similar reductions in adenylyl cyclase activities. In addition, increasing the free Ca2+ concentration progressively inhibited adenylyl cyclase activity in the control, digoxin-treated, and calcium gluconate-treated sarcolemma preparations in vitro. Moreover, digoxin and calcium gluconate pretreatment blunted the increase in cAMP in myocardial tissue after dobutamine infusion in vivo. Thus, digoxin rapidly reduces beta-adrenergic contractile response in rabbit hearts. This reduction may reflect an inhibition of adenylyl cyclase by Ca2+ mobilized via Na+/Ca2+ exchange.

4-Nitrophenylphosphatase↗

Arsenic species in solutions for parenteral nutrition.

BACKGROUND: In spite of its high toxicity, arsenic is a common contaminant in pharmaceuticals. This is stated by pharmacopoeias' monographs where it is not generically included with other heavy metals, but has its own specifications. Arsenic should not exceed 0.1 mg/L in most pharmaceutical products for IV administration. This limit, however, was established without taking into consideration the specific arsenic species which contribute to this amount. In this work, the presence of arsenite and arsenate species in solutions of amino acids, salts, vitamins, and lipids commercialized for IV administration was investigated. METHODS: The measurements were done by hydride generation atomic absorption spectrometry. RESULTS: The results showed that all commercial formulations contain both arsenic species in some level; however, the total arsenic content exceeded the allowed limit in only a few samples. Calcium gluconate, sodium bicarbonate, heparin, and vitamin solutions were the most contaminated, presenting total arsenic concentration ranging from 62 to 249 microg/L. The most important finding, however, was the different ratios As(V)/As(III) among the formulations. Whereas practically only As(V) was found in ampoules containing water for injection and salt solutions (NaCl, KC1, phosphates), As(III) predominated in solutions of vitamins, gluconate, and glucose. As these are reducing substances, we investigated the possibility of their reaction with As(V) and its conversion into As(III). The heating of As(V) in the presence of gluconate, glucose, ascorbic acid, methionine, isoleucine, sodium chloride, and pure water, in autoclave for 15 minutes, showed that, whereas no As(III) was found in pure water and sodium chloride solution, approximately 50% of As(V) was converted into As(III) in the remainder of the solutions. CONCLUSIONS: The results showed that As(V), the main species in these formulations, may be converted into As(III), depending on the presence of reducing substances among the formulation constituents.

Arsenic↗