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PubMed1987

Effect of acetazolamide on renal metabolism and ammoniagenesis in the dog.

The effect of acetazolamide (ACZ) on renal metabolism and ammoniagenesis was studied in the dog in vivo and in vitro. ACZ was administered to 10 dogs with normal acid-base status and five with chronic metabolic acidosis induced by NH4Cl. In both groups of dogs, the acute administration of ACZ markedly reduced the urinary excretion of ammonium (from 33 to 10 in normal dogs and from 100 to 23 mumoles/100 ml GFR in acidotic dogs) whereas its release into the renal vein was increased in a reciprocal fashion (from 69 to 95 in normal dogs and from 91 to 152 mumoles/100 ml GFR in acidotic dogs). ACZ did not change the total ammonium production nor the renal glutamine utilization. The renal utilization or production of glutamate, alphaketoglutarate, alanine and citrate also remained unchanged. Despite a marked urinary alkalinization, citraturia remained minimal. However, the renal cortical concentrations of glutamine, glutamate, succinate, fumarate, malate, aspartate and phosphoenolpyruvate fell following ACZ administration, especially in acidotic dogs showing rapid renal utilization of glutamine. ACZ had no effect on the same metabolites in the kidney of normal dogs even when lactate utilization was enhanced by lactate infusion. This study demonstrates that an accelerated ammoniagenic flux can proceed in the dog kidney without the renal cortical changes produced by metabolic acidosis in this species. In vitro, using dog tubules, a selective effect of ACZ on glutamine metabolism as compared to lactate was observed. ACZ reduce the rate of the reactions catalyzed by alphaketoglutarate dehydrogenase and by succinyl CoA synthetase. Other enzymes of the ammoniagenic and gluconeogenic pathways (glutaminase, GLDH, malic enzyme, PEPCK) were not changed by ACZ. The metabolic effects of ACZ observed in the intact kidney in vivo or with tubules in vitro may be in part related to the effect of ACZ on these enzymes critical for the ammoniagenic process.

Acetazolamide↗
PubMed1966

Clearing-factor lipase in adipose tissue. Factors influencing the increase in enzyme activity produced on incubation of tissue from starved rats in vitro.

1. Evidence is presented that the increase in clearing-factor lipase activity that occurs when adipose tissue from starved rats is incubated in a defined medium in vitro is due to an increase in the total enzyme content of the system. It is shown that the clearing-factor lipase activity rises to reach a plateau level where, it is suggested, rates of enzyme synthesis and of enzyme destruction become balanced. 2. The presence of heparin in the incubation medium results in the extraction of part of the clearing-factor lipase originally present in the adipose tissue and this could provide the stimulus for the increase in total enzyme content. 3. Glucose is required in the incubation medium at a very low concentration. It can be replaced by fructose, but not by pyruvic acid, lactic acid, glyceric acid or dihydroxyacetone. 4. Adrenaline and corticotrophin inhibit the increase in enzyme activity when they are present in the incubation medium. 5. The high clearing-factor lipase activity associated with adipose tissue of fed rats is decreased by 50% within 3hr. of the injection of puromycin.

Adipose Tissue↗
PubMed1986

Purification and characterization of human hepatic cysteine-conjugate beta-lyase.

Cysteine-conjugate beta-lyase (EC 4.4.1.13) was purified about 880-fold from human liver obtained post mortem. The purification procedure included (NH4)2SO4 precipitation, chromatography on DEAE-cellulose and hydroxyapatite, gel filtration on Sephadex G-200, and chromatofocusing. The purified enzyme cleaves the C-S bond of several S-aryl-L-cysteines to yield equimolar amounts of thiols, pyruvic acid and ammonia via an alpha beta-elimination reaction. The Mr of the enzyme was estimated to be 88,000 by gel filtration. The enzyme is thermolabile, has a pH optimum of 8.5, and an apparent Km of 0.7 mM towards S-(p-bromophenyl)-L-cysteine. The enzyme requires pyridoxal 5'-phosphate as a cofactor, and hence the enzyme activity was completely abolished by hydroxylamine. No effect of EDTA or thiol-blocking reagents was observed on the activity of the enzyme.

Carbon-Sulfur Lyases↗
PubMed2003

Meiotic response of in vitro matured canine oocytes under different proteins and heterologous hormone supplementation.

The impact of TCM-199 supplemented with different proteins and heterologous hormones on the in vitro maturation (IVM) rate of bitch oocytes was evaluated by nuclear staining under fluorescence microscopy. Oocytes were recovered by slicing of ovaries from bitches presented at various stages of oestrous cycle to ovariohysterectomy. The basic culture medium was TCM-199 supplemented with 25 mM Hepes/l, with 10% heat-inactivated oestrous cow serum (ECS), 50 microg/ml gentamicin, 2.2 mg/ml sodium bicarbonate and 22-microg/ml pyruvic acid, 1.0-microg/ml oestradiol (E 8875; Sigma), 0.5-microg/ml follicle-stimulating hormone (FSH) (Folltropin-V; Vetrepharm Inc., Ontario, Canada) and 0.03 IU/ml human gonadotropin (hCG) (Profasi HP; Serono, Aubonne, Switzerland). Oocytes were distributed randomly between basic culture medium (control) and the corresponding experimental treatment. Hormone treatments were: oocytes cultured in; (1) medium without FSH, (2) control medium supplemented with 20 microg/ml oestradiol, or (3) medium supplemented with 1 microg/ml human somatotropin (hST; Humatrope, Lilly, Saint Cloud, France). The second experiment consisted of oocytes cultured in medium supplemented with 0.4% (w/v) bovine serum albumin (BSA, fraction V; Gibco Grand Island, NY, USA) instead of ECS, or oocytes cultured in medium with 10% inactivated oestrous bitch serum (EBS) instead of ECS. Oocytes were cultured in 100 microl droplets (up to 25 oocytes per drop) under mineral oil at 37 degrees C in a 100% humidified atmosphere containing 5% CO2 in air. After 72 h of IVM, the highest rates (p < 0.05) of meiotic resumption were achieved with the 0.4% BSA supplementation. A positive influence on the metaphase II (MII) acquisition rate was observed with hST supplement. Oocytes cultured with 10% EBS supplementation did not develop to the MII stage. The results in this study show that the protein and hormone supplements to TCM-199 culture medium tested did not promote the final steps of IVM of bitch oocytes.

Animals↗
PubMed1998

The production of D-acetoin by a transgenic Escherichia coli.

A 6 kbp SphI fragment encoding genes for the enzymes alpha-acetolactate synthase (ALS), alpha-acetolactate decarboxylase (ALDC) and meso-2,3-butanediol dehydrogenase (meso-BDH), involved in the formation of meso-2,3-butanediol (meso-BD) from pyruvic acid, was cloned into plasmid pUC118. When derivatives of this plasmid were introduced into Escherichia coli JM109, the transformants were able to produce D-acetoin (D-AC) without contamination with L-acetoin (L-AC).

Acetoin↗
PubMedDate not supplied

Can embryo metabolism be used for selecting bovine embryos before transfer?

The quality of in vitro-produced bovine embryos remains variable. The selection of these embryos based only on their morphology does not allow for acceptable gestational rates to be obtained. The use of metabolic markers to select viable embryos before transfer would be of valuable help, both economically and as a research tool. The ideal marker should meet several conditions: it should be able to be evaluated 1) in a totally non-invasive manner, 2) on individual embryos (which necessitates very sensitive techniques), 3) very rapidly (so that it is compatible with the immediate transfer of fresh embryos), and 4) in order to allow viable embryos to be separated from those that are not viable, whatever the production system used. In practice, such a marker does not exist, but certain methods of metabolic evaluation resemble it. The development of a metabolic marker is confronted by the metabolic characteristics of the embryo, notably the evolution of the metabolism during the development of the embryo and its adaptation to the changes in the environment.

Adaptation, Physiological↗
PubMed1983

Potassium-dependent increases in cytosolic pH stimulate metabolism and motility of mammalian sperm.

Sperm cytosolic pH, determined by the spectral properties of intracellular carboxyfluorescein, is decreased rapidly by the diffusion and subsequent dissociation of the uncharged weak acids pyruvic, lactic, or hydroxybutyric and is increased by diffusion and subsequent intracellular protonation of the weak base NH3. Metabolic and kinetic activity increases dramatically when intracellular pH is elevated above 6.8-6.9 by addition of 50 mM NH4Cl to sperm suspended in a 120 mM NaCl medium. Respiratory stimulation is not observed upon comparable additions of 50 mM Li+ or K+ or when the pH of the medium is increased from 6.5 to 8.2. However, increases of the external pH to 7.8-8.2 in medium employing 120 mM KCl result in increased metabolic and kinetic activity, comparable to the maximal stimulation induced by the phosphodiesterase inhibitor caffeine. An increase in cytosolic pH from 6.3-6.6 to 6.8 occurs concomitant with the respiratory stimulation induced by KCl in alkaline media. No change in cytosolic pH follows addition of caffeine. Cyclic AMP-dependent protein kinase activity ratios, determined in cellular extracts, are increased by caffeine treatment but are not elevated by 120 mM KCl, by alkaline pH, or by their combination. These observations indicate that cytosolic pH plays a role in the regulation of motility and metabolism of mammalian sperm that is not mediated by cyclic AMP but that may be under control of a plasma membrane voltage-dependent proton channel. However, H+ fluxes across vesicles prepared from sperm membranes are unaffected by variation in the magnitude of the transvesicular K+ concentration gradient.

Ammonium Chloride↗
PubMed1995

beta-Cystathionase from Bordetella avium. Role(s) of lysine 214 and cysteine residues in activity and cytotoxicity.

beta-Cystathionase (EC 4.4.1.8) from Bordetella avium is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the hydrolysis of L-cystine to yield pyruvic acid, NH3, and thiocysteine. The latter compound is highly toxic toward MC3T3-E1 osteogenic cells, rat osteosarcoma cells, and other cell lines maintained in tissue culture (Gentry-Weeks, C. R., Keith, J. M., and Thompson, J. (1993) J. Biol. Chem. 268, 7298-7314). Site-directed mutagenesis has established that lysine 214 of the sequence TKYVGGHSD, is primarily responsible for internal aldimine binding of PLP in the holoenzyme. Translation of the DNA sequence of the beta-cystathionase gene (metC) from B. avium, reveals 4 cysteine residues/enzyme subunit (M(r) = 42,600), and spectrophotometric analysis with 4,4'-dithiodipyridine showed that there were no disulfide linkages in the native protein. beta-Cystathionase is inhibited by sulfhydryl-reactive agents, including N-ethylmaleimide (NEM). To elucidate the mechanism of NEM inhibition, each of the 4 cysteine residues at positions 88, 117, 279, and 309 was individually replaced by alanine or glycine. The mutant proteins C88A, C117G, C279G, and C309A were purified to homogeneity, and each was assayed for enzyme activity, PLP-binding, NEM sensitivity, and susceptibility to chymotrypsin digestion. The activities of mutant proteins C88A and C279G were comparable with that of the native enzyme, and since both forms were inhibited by NEM, neither cysteine 88 nor 279 are prerequisite for enzyme activity. By elimination, cysteine residues 117 and 309 must be the targets for alkylation, and resultant inactivation of beta-cystathionase, by the -SH reactive agent. Substitution of cysteine 117 and 309 with glycine and alanine, respectively, yielded the inactive proteins C117G and C309A. PLP was not detectable in these proteins, and their absorption spectra lacked the peak (at 420 nm) that is characteristic of internal PLP-Schiff base formation. Edman degradation revealed that C117G (M(r) approximately 36,000) also lacked the first 63 amino acids comprising the N terminus of the native protein. The beta-cystathionase mutants C117G and C309A showed enhanced susceptibility to chymotrypsin digestion. Cysteine residues 117 and 309 may reside in conformationally sensitive environments, and in the native enzyme these amino acids most probably serve a structural function. Toxicity assays performed with the various mutant proteins obtained by site-directed mutagenesis established that only catalytically active forms of beta-cystathionase were were cytotoxic for tissue culture cells.

3T3 Cells↗
PubMed1996

The biogenetic anatomy of vitamin B6. A 13C NMR investigation of the biosynthesis of pyridoxol in Escherichia coli.

It is shown by incorporation experiments with 13C bond-labeled substrates, followed by analysis by means of 13C NMR spectroscopy, that two compounds, 1-deoxy-D-xylulose (12) and 4-hydroxy-L-threonine (), serve as precursors of pyridoxol (vitamin B6) (1) in Escherichia coli. Together, these two compounds account for the entire C8N skeleton of the vitamin. 1-Deoxy-D-xylulose supplies the intact C5 unit, C-2',2,3,4,4' of pyridoxol. 4-Hydroxy-L-threonine undergoes decarboxylation in supplying the intact C3N unit, N-1,C-6,5,5'. Both precursors are ultimately derived from glucose. The C5 unit of pyridoxol that is derived from 1-deoxy-D-xylulose originates by union of a triose phosphate (yielding C-3,4,4') with pyruvic acid (which decarboxylates to yield C-2',2). D-Erythroate (11) enters the C3 unit, C-6,5,5', and is therefore an intermediate on the route from glucose into 4-hydroxy-L-threonine.

Escherichia coli↗
PubMed1984

Effects of ketamine anaesthesia on the metabolic response to pelvic surgery.

The effects of ketamine anaesthesia on the metabolic and endocrine response to pelvic surgery were investigated, and compared with results obtained in a control group of patients anaesthetized with thiopentone and halothane. Ketamine anaesthesia before the onset of surgery was associated with a significant increase in blood glucose and plasma cortisol concentrations, and in heart rate. However, when surgery was established there were no metabolic, endocrine or haemodynamic differences between ketamine and halothane anaesthesia. We conclude that ketamine does not exacerbate the metabolic response to surgery.

Adult↗
PubMed1977

Effect of dietary threonine supplementation on tyrosine toxicity in the rat.

The objective of this study was to determine the effect of threonine supplementation on tyrosine metabolism in rats fed a low protein diet with excess tyrosine. The growth retardation and the development of eye and paw lesions that occur in rats ingesting a basal plus 3% or 5% L-tyrosine diet could be alleviated partially by the addition of 0.5% or 1.0% L-threonine to the diet. An increased blood tyrosine level in rats fed excess tyrosine was also lowered by threonine supplementation. In tyrotoxic conditions, the activities of liver tyrosine transaminase (EC 2.6.1.5) and threonine dehydratase (EC 4.2.9.16) were elevated, but p-hydroxyphenyl pyruvic acid oxidase (EC 1.13.11.27) which is also intimately associated with tyrosine toxicity was found to be inactivated. Furthermore, biosynthesis of ascorbic acid in liver was significantly lowered in this condition. However, addition of L-threonine in the diet, not only could cure the signs developed due to excess tyrosine, but also could affect the levels of enzymes studied.

4-Hydroxyphenylpyruvate Dioxygenase↗
PubMed1983

A metabolic comparison of cysteine and methionine supplements in the diet of a rat.

Adult male Long-Evans rats (250-300 g) were fed diets containing 15% of casein not supplemented with amino acids, supplemented with 0.505% cysteine or supplemented with 0.620% methionine for a period of 17 days. Rats fed the diets supplemented with cysteine had an increased incorporation of the 14C-radioactivity from [U-14C]alanine into liver glycogen and a decreased incorporation from [U-14C]acetate into fatty acids. Pyruvate carboxylase activity was slightly increased and citrate cleavage enzyme activity decreased in the livers of those rats fed the diets supplemented with cysteine. Rats fed diets supplemented with methionine had a decreased liver phosphoenolpyruvate carboxykinase activity. Based on these data it appears that rats fed diets supplemented with cysteine adapt metabolically to store energy as glycogen, while those fed diets supplemented with methionine tend to store energy as lipid.

Animals↗
PubMed1989

Calcium uptake by bovine epididymal spermatozoa is regulated by the redox state of the mitochondrial pyridine nucleotides.

Immature caput epididymal sperm accumulate calcium from exogenous sources at a rate 2- to 4-fold greater than mature caudal sperm. Calcium accumulation by these cells, however, is maximal in the presence of lactate as external substrate. This stimulation of calcium uptake by optimum levels of lactate (0.8-1.0 mM) is about 5-fold in caput and 2-fold in caudal sperm compared to values observed with glucose as substrate. Calcium accumulation by intact sperm is almost entirely mitochondrial as evidenced by the inhibition of uptake by rotenone, antimycin, and ruthenium red. The differences in the ability of the various substrates in sustaining calcium uptake appeared to be related to their ability to generate NADH (nicotinamide adenine dinucleotide). Previous reports have documented that mitochondrial calcium accumulation in several somatic cells is regulated by the oxidation state of mitochondrial NADH. A similar situation obtains for bovine epididymal sperm since calcium uptake sustained by site III oxidation of ascorbate in the presence of tetramethyl phenylenediamine and rotenone was also stimulated by NADH-producing substrates, including lactate, and inhibited by substrates generating NAD+ (nicotinamide adenine dinucleotide, oxidized form). Further, calcium uptake by digitonin-permeabilized sperm in the presence of succinate was stimulated when NADH oxidation was inhibited by rotenone. The compounds alpha-keto butyric, valeric, and caproic acids, which generate NAD+, inhibited the maximal calcium uptake observed in the presence of succinate and rotenone, and the hydroxy acids lactate and beta-hydroxybutyrate reversed this inhibition. These results document the regulation of sperm calcium accumulation by the physiological substrate lactate, emphasize the importance of mitochondria in the accumulation of calcium by bovine epididymal sperm, and suggest that the mitochondrial location of the isozyme LDH-X in mammalian sperm may be involved in the regulation of calcium accumulation.

3-Hydroxybutyric Acid↗
PubMedDate not supplied

Hydralazine and its metabolites: in vitro and in vivo activity in the rat.

The vasodilator, hypotensive, and antihypertensive effects of hydralazine and its known and putative metabolites were compared in vitro, in the isolated, perfused mesenteric arterial bed of the rat, and in vivo, in the urethane-anesthetized normotensive rat (NR) and in the conscious renal hypertensive rat (RHR). In the mesenteric bed, hydralazine produced inhibition of noradrenaline (NA)-induced vasoconstriction (IC50-NA = 0.4 micrograms/ml). All the metabolites were five to greater than 250 times less potent than the parent compound. Hydralazine inhibited potassium-induced vasoconstriction at concentrations (IC50-K+ = 700 micrograms/ml) above those required to inhibit NA. Two metabolites, 9-hydroxy-3-methyl-s-triazolo-(3.4-a)phthalazine and the acetone hydrazone (HP-AH), were more potent (five- and 10-fold, respectively) than hydralazine in inhibiting potassium-induced vasoconstriction. The other metabolites produced less than 50% inhibition at the highest concentration tested. In in vivo studies, blood pressure in NR or RHR was reduced by hydralazine, following doses of 0.1 or 0.25 mg/kg i.v. and above. HP-AH was sixfold less active than hydralazine in NR and 10-fold less active in RHR, while the pyruvic acid hydrazone was 33- and 14-fold 1 s active, respectively. The other metabolites tested were practically inactive in concentrations up to the limits of solubility. Although several hydralazine metabolites show some vasodilator and blood pressure-lowering activity, it seems unlikely that the formation of metabolites is a major factor in the antihypertensive effect of hydralazine or is responsible for its long duration of action.

Animals↗
PubMed2003

Aberrant intranuclear localization of biotin, biotin-binding enzymes, and beta-catenin in pregnancy-related endometrium and morule-associated neoplastic lesions.

Biotin-rich intranuclear inclusions, also known as optically clear nuclei, have been observed in various neoplastic and non-neoplastic lesions. They look like nuclei of herpesvirus-infected cells and cause a false-positive immunohistochemical result by avidin-biotin-complex (ABC) method. In the literature, all types of neoplastic lesions with intranuclear inclusions, with one exception, have been characteristically associated with squamoid structures known as morules. By contrast, all reported non-neoplastic lesions with such inclusions lacked morules and were confined to pregnancy-related endometrium. In the present study, adding unreported types of morule-associated neoplastic lesions, we investigated the distribution of biotin, biotin-binding enzymes, and beta-catenin in these lesions by immunohistochemical staining. We detected the intranuclear localization of biotin and of two mitochondrial biotin-binding enzymes (pyruvic acid carboxylase and propionyl CoA carboxylase) in all lesions examined, regardless of whether they were neoplastic or non-neoplastic and irrespective of the presence or absence of morules. The intranuclear localization of beta-catenin was detected in all neoplastic lesions with morules and in ovarian endometrioid adenocarcinoma without morules, but not in non-neoplastic endometrial lesions. These results suggest the following conclusions: (1) lesions with biotin-rich intranuclear inclusions can be classified as non-neoplastic/pregnancy-related endometrial and as neoplastic/pregnancy-unrelated or morular category; (2) the intranuclear biotin in both types of lesion is found in conjunction with biotin-binding enzymes. However, the role of beta-catenin in morule-associated neoplastic lesions, the relationship between beta-catenin and biotin/biotin-binding enzymes, and the mechanism of migration of biotin and biotin-binding enzymes from the cytoplasm to the nucleus remain unclear.

Biotin↗
PubMed1984

Changes in metabolism of the rumen bacterium Streptococcus bovis H13/1 resulting from alteration in dilution rate and glucose supply per unit time.

Streptococcus bovis H13/1 was grown in a glucose-limited chemostat. A concomitant increase in dilution rate and glucose supply per unit time caused both an increase in lactate production per mole of glucose fermented and a linear increase in growth yield over the dilution rate range 0.052 to 0.141/h. When the dilution rate was increased with no change in glucose supply per unit time there was a reduction in lactate production and an increase in that of acetate and ethanol coinciding with a non-linear increase in growth yield. YMaxglu = 38.6 and a maintenance coefficient, ms = 0.290 mmol/l glucose/g cells/h were calculated. The results also suggested an interaction between the formate and CO2 pools.

Acetates↗