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Study of plasma antioxidant status in Alzheimer's disease.

To examine the plasma antioxidant status of Alzheimer's disease (AD) patients and to evaluate the influence of apolipoprotein E (APOE) genotype. There are reasons to suspect involvement of the free hydroxyl radical in the pathogenesis of AD. In contrast, studies in plasma of AD patients for the evaluation of levels of biomarkers of oxidation are controversial. Twenty AD patients diagnosed using the National Institute for Neurological Disorders/Alzheimer's Disease and Related Disorders (NINDS/ADRDA) criteria and 22 controls chosen amongst different subjects without cognitive damage. All the subjects--both AD patients and controls--were stratified by their APOE genotype (3/3, 3/4 or 4/4), which was determined by PCR. Plasma total antioxidant capacity (TAC) was determined using two complementary procedures: FRAP, which measures the ferric reduction capacity, and ABTS, which measures the radical scavenging capacity. In addition, 2-amino-adipic semialdehyde (2-AAS), a biomarker of protein oxidation, was evaluated. No significant difference was observed between the AD and control groups regarding plasma TAC. When the subjects were classified by their APOE genotype, significant differences were found in the APOE 4/4 group in the TCA determined by the FRAP method. Subjects with APOE genotype 4/4, which is the group with higher incidence in AD, showed lower antioxidant capacity of plasma. It is the first time that antioxidant capacity in plasma is evaluated in AD patients characterized by their APOE genotypes.

2-Aminoadipic Acid↗

Recurrence of gestational diabetes.

We conducted a retrospective review of 540 women with gestational diabetes managed by our Service between 1990 and 1996. The aim was to determine the recurrence rate of gestational diabetes and the factors associated with recurrence. Of 117 women who had a subsequent pregnancy, 82 (70%) had a recurrence of gestational diabetes according to criteria where the fasting glucose value > or = 5.5 and/or 1 hour > or = 10.0 and/or 2-hour > or = 8.0 mmol/L after a 75 g oral glucose load. The recurrence rate was 62.4% (58), using the criteria of the Australian Diabetes in Pregnancy Society (ADIPS). Older age in both the index and subsequent pregnancy and insulin requirement during the index pregnancy were the strongest predictors for recurrence of gestational diabetes. Non-English speaking country of birth, higher diagnostic glucose tolerance test (GTT) levels, greater prepregnancy BMI and weight gain between pregnancies were also associated with recurrence.

Adult↗

Is glutamate a trigger factor in epileptic hyperactivity?

The effects of glutamate and aspartate antagonists were studied on limb-jerk frequency and EEG patterns in rats made epileptic by cobalt implantation in the sensorimotor cerebral cortex. The results of this study were as follows: (1) alpha-Amino-4-phosphonobutyric acid (0.055--1.10 mM) decreased or completely prevented the epileptic manifestations. The effect was reversible 30 min after washing with artificial CSF solution. (2) DL-Pyroglutamic acid completely abolished the myoclonic jerks and EEG spikes. (3) alpha-Amino-5-phosphonovaleric acid and alpha-D-amino-adipic acid significantly reduced the frequency of epileptic spikes and myoclonic jerks. (4) Other analogs, alpha-amino-3-phosphonopropionic acid (0.6 mM), alpha-amino phosphonocaproic acid (0.95), and hydroxy-3-amino pyrrolidone-2 were without effect. (5) Glutamate itself did not decrease the epileptic manifestations.

Amino Acids↗

A Pseudomonas aeruginosa alginate-exotoxin A conjugate that elicits anti-alginate and exotoxin A-neutralizing antibodies.

Pseudomonas aeruginosa alginate was covalently coupled to exotoxin A by reductive amination using adipic acid dihydrazide as spacer. The conjugate was composed of 25% alginate and 75% exotoxin A and possessed an average molecular mass higher than 700 kDa as determined by polyacrylamide gel electrophoresis. The conjugate had virtually no ADP-ribosyltransferase activity and a reduced cytotoxicity for TSA8 murine cells, derived from Friend erythroleukemia cells, as indicated by a greater than 50-fold increased LD50. Anti-conjugate antibodies recognized exotoxin A and alginate. A booster injection resulted in markedly increased antibody ELISA titers to both exotoxin A and alginate. The antibodies neutralized the exotoxin A toxicity.

ADP Ribose Transferases↗

Spontaneous mutations affecting transcriptional regulation by protocatechuate in Acinetobacter.

Positive selection yields Acinetobacter strains with a spontaneous mutation blocking catabolism of protocatechuate. For this study, the growth temperature during selection was lowered to 22 degrees C: growth at 37 degrees C was found to mask the role of the protocatechuate-responsive transcriptional regulator PcaU. The resulting mutants included those with amino acid substitutions useful for understanding PcaU structure and function, a 20-bp deletion whose repeated isolation suggested genetic instability of DNA in the putative PcaU operator, and a large deletion whose phenotype revealed that the supraoperonic cluster of genes for the protocatechuate branch of the beta-ketoadipate pathway extends to genes for the utilization of C(6)-C(10) straight-chain dicarboxylic acids including adipate.

Acinetobacter↗

Isoprenoid biosynthesis in multiple sclerosis, II. A possible role of NADPH.

Genetic predisposition in MS, influence of fat consumption on the disease, and excretion of lipid metabolites in urine led us to investigate isoprenoid metabolism in this disease. Ubiquinone concentration and biosynthesis was normal in lymphocytes. Cytochrome oxidase, which contains an isoprenoid side chain, was normal in activity. Cholesterol biosynthesis from acetate was found to be elevated in MS, and so was triglyceride biosynthesis. Increased biosynthesis may offer a very simple explanation to all the metabolites excreted (3-methylglutaconic acid, 2-hydroxy-2-methyl-3-butenoic acid and adipic acid). Increased biosynthesis may be caused by an elevated NADPH/NADP ratio, since such an elevation may also account for many other biochemical anomalies in MS. Elevated NADPH/NADP ratio may be of direct importance in the pathogenesis.

Cholesterol↗

Dicarboxylic aciduria due to medium chain acyl CoA dehydrogenase defect. A cause of hypoglycemia in childhood.

Dicarboxylic aciduria was found during hypoglycemic episode in a 14 months old girl. Her brother had died at the age of 4 years during febrile illness. A ketogenic diet induced in this patient a severe hypoglycemia. Urinary organic acid profile exhibited abnormal excretion of the C6-C10 dicarboxylic acids (adipic-suberic-sebacic) and related metabolites (5 hydroxyhexanoic, hexanoylglycine, suberyl glycine). This pattern suggested a defect in fatty acids beta oxidation. Plasma carnitine values was within control limits. Similar clinical findings and urinary organic acids excretion have been described in 6 patients since the initial case of Gregersen. Enzymatic studies on cultivated fibroblasts from our patient showed a defect in medium chain CoA dehydrogenase. The treatment of this disease consists of glucose infusion during attacks and prevention of fasting. This rare disease must be considered in a child with non ketotic hypoglycemia or Reye's syndrome.

Acyl-CoA Dehydrogenases↗

Compatibility study between acetylcysteine and some commonly used tablet excipients.

Differential scanning calorimetry (DSC), Fourier transform infra-red spectroscopy (FT-IR), HPLC and TLC were used to investigate the interactions between the mucolytic drug acetylcysteine and a number of commonly used tablet and capsule excipients. Acetylcysteine was found to be compatible with microcrystalline cellulose (Avicel PH 101), sodium carboxymethylcellulose, amorphous silicon dioxide (Aerosil), PVP, cross-linked PVP (Polyplasdone XL), corn starch, saccharose and magnesium stearate. Acetylcysteine thermal stability (onset degradation temperature) was decreased in mixtures with corn starch, magnesium stearate, saccharose and lactose. Interactions of acetylcysteine with lactose, PEG 4000 and 6000, glycine, adipic acid and saccharin sodium were found using DSC and studied in detail with FT-IR, HPLC and TLC. The results suggest that acetylcysteine in mixtures with PEG 4000, glycine or saccharin sodium is degraded during storage at conditions of high temperature and humidity.

Acetylcysteine↗

Responses of solitary retinal horizontal cells from Carassius auratus to L-glutamate and related amino acids.

Effects of L-glutamate and its analogues on membrane potentials of solitary horizontal cells were studied by intracellular recording. L-glutamate depolarized these cells at micromolar concentrations (greater than or equal to 10 microM), while D-glutamate and L-alpha-amino adipic acid produced slight depolarizations only at millimolar concentrations. Neither L- nor D-aspartate, even at millimolar doses, produced any change in solitary horizontal-cell resting potential. Solitary horizontal-cell responses to L-glutamate did not desensitize detectably. Responses to pairs of brief, ionophoretic pulses of L-glutamate were nearly equal in amplitude at inter-pulse intervals as short as 50 ms. Responses to maintained applications of low doses of L-glutamate did not decline for as long as 2 min. Depolarizing responses were produced by ionophoretic applications of L-glutamate near cell somata as well as dendrites. The mean sensitivity was 1.4 +/- 1.5 mV/nC with a maximum of 5.1 mV/nC. Depolarizing responses to L-glutamate reversed in polarity at membrane potentials between 0 and -20 mV, were accompanied by a decrease in membrane slope resistance, and were suppressed by replacement of extracellular sodium ions with choline. These results demonstrate that chemosensitivity of retinal horizontal cells to acidic amino acids persists after dissociation protocols, and in several respects resembles that found in horizontal cells in situ. These findings are consistent with the notion that retinal horizontal cells receive a synaptic input involving L-glutamate or a similar substance.

2-Aminoadipic Acid↗

Human renal organic anion transporter 1-dependent uptake and toxicity of mercuric-thiol conjugates in Madin-Darby canine kidney cells.

Mercuric ions are highly reactive and form a variety of organic complexes or conjugates in vivo. The renal proximal tubule is a primary target for mercury uptake and toxicity, and circumstantial evidence implicates organic anion transporters in these processes. To test this hypothesis directly, the transport and toxicity of mercuric-thiol conjugates were characterized in a Madin-Darby canine kidney cell line stably transfected with the human organic anion transporter 1 (hOAT1). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-terazolium bromide assays (for mitochondrial dehydrogenase) confirmed that mercuric conjugates of the thiols N-acetylcysteine (NAC), cysteine, or glutathione were more toxic in hOAT1-transfected cells than in the nontransfected cells. The NAC-Hg(2+) conjugate was most cytotoxic, inducing greater than 50% cellular death over 18 h at a concentration of 100 microM. The cytotoxic effects were fully reversed by probenecid (an OAT1 inhibitor) and partially reversed by p-aminohippurate (an OAT1 substrate). Toxicity of this conjugate was reduced by the OAT1-exchangeable dicarboxylates alpha-ketoglutarate, glutarate, and adipate, but not by succinate, a nonexchangeable dicarboxylate. (203)Hg-uptake studies showed probenecid-sensitive uptake of mercury-thiol conjugates in the hOAT1-transfected cells. The apparent K(m) for the NAC-Hg(2+) conjugate was 44 +/- 9 microM. Uptake of the NAC-Hg(2+) conjugate was cis-inhibited by glutarate, but not by methylsuccinate, paralleling their effects on toxicity. Probenecid-sensitive transport of the NAC-Hg(2+) conjugate was also shown to occur in Xenopus laevis oocytes expressing the hOAT1 or the rOAT3 transporters, suggesting that OAT3 may also transport thiol-Hg(2+) conjugates. Thus, renal accumulation and toxicity of thiol-Hg(2+) conjugates may depend in part on the activity of the organic transport system.

Animals↗

Incorporation of labeled precursors into A16886B, a novel -lactam antibiotic produced by Streptomyces clavuligerus.

The incorporation of C-14 from amino acids into A16886B, 7-(5-amino-5-carboxyvaleramido)-7-methoxy-3-carbamoyloxymethyl-3-cephem-4- carboxylic acid, by Streptomyces clavuligerus is reported. As with cephalosporin C biosynthesis by the mold Cephalosporium acremonium, labels from cysteine, valine, and alpha-amino-adipic acid were incorporated. Unlike cephalosporin C, in A16886B label from lysine was incorporated into the alpha-aminoadipic acid side chain. Label from methionine-(14)C-methyl was incorporated into the methoxyl group. The relative percentage of incorporation of (3)H and (14)C from doubly labeled cystine suggests the improbability of the C-7 methoxyl group arising from an intermediate containing a double bond between C-6 and C-7.

Amides↗

Substrate inhibition of beta-lactamases, a method for predicting enzymatic stability of cephalosporins.

Selected cephalosporins, including cefamandole, cephaloridine, cephaloglycin, and cefoxitin, were examined for their ability to inhibit the enzymatic activity of and act as substrates for beta-lactamases produced by Enterobacter cloacae and Staphylococcus aureus. Enzyme inhibition was determined by Michaelis-Menten kinetic measurements and by a spot plate assay using a chromogenic substrate (Glaxo compound 87/312). These two methods provide comparable estimates of kinetic parameters. Inhibition of beta-lactamase, as measured by these two methods, was generally found to correlate with resistance to hydrolysis and is proposed as a preliminary method of assessing susceptibility of cephalosporins to beta-lactamase hydrolysis. Four 7-alphaOCH(3), 7-alphaH cephalosporin analogue pairs were also examined. The presence of the 7-alphaOCH(3) substituent invariably resulted in reduced susceptibility to enzymatic hydrolysis, regardless of the other C7 substituent. The 7-alphaOCH(3) compounds were also better inhibitors than were their 7-alphaH analogues, with the exception that 7-alphaOCH(3) compounds having C7 adipic acid substituents were less inhibitory to the S. aureus enzyme than were the corresponding 7-alphaH analogues. Response of these two enzymes to 7-alphaOCH(3) and 7-alphaH cephalosporins suggests that beta-lactamase hydrolysis of these compounds involves attack at the alpha side of the betalactam ring.

Amidohydrolases↗

Methanogenic decomposition of ferulic Acid, a model lignin derivative.

Ferulic acid, a model lignin derivative, was observed to be biodegradable to methane and carbon dioxide under strict anaerobic conditions. This conversion appears to be carried out by a consortium of bacteria similar to that previously described for the methanogenic degradation of benzoic acid. A temporary buildup of acetate in these cultures indicates that it is a likely intermediate and precursor for methane formation. An analog of coenzyme M, 2-bromoethanesulfonic acid (BESA), inhibited gas production and enhanced the buildup of propionate, butyrate, isobutyrate, and isovalerate. Phenylacetate, cinnamate, 3-phenylpropionate, benzoate, cyclohexane carboxylate, adipate, and pimelate were also detected in BESA-inhibited cultures. A pathway is proposed which includes these various acids as possible intermediates in the methanogenic degradation of ferulic acid. This model overlaps previously described benzoic acid degradation pathways, suggesting that this type of anaerobic degradation may be common for aromatic compounds.

Journal Article↗

Isolation and Characterization of a Cyclohexane-Metabolizing Xanthobacter sp.

An unusual Xanthobacter sp., capable of independent growth on cyclohexane as the sole source of carbon and energy, has been isolated from soil by using classical enrichment techniques. The mean generation time for growth on cyclohexane was 6 h. The microorganism showed a limited ability to utilize hydrocarbons, with only alicyclic hydrocarbons closely related to cyclohexane supporting growth. Ultrastructural studies indicated the presence of electron-transparent vesicles in the cyclohexane-grown Xanthobacter sp., but the presence of complex intracytoplasmic membranes could not be identified. A soluble inducible enzyme capable of oxidizing cyclohexane was identified in cell extracts. This enzyme had a pH optimum of 6.5, an absolute specificity for NADPH, and a stoichiometric requirement for molecular O(2) which was consistent with the formation of cyclohexanol. The enzyme showed no activity towards straight chain alkanes and only a limited activity towards unsaturated ring compounds. Enzymatic studies with cell extracts have indicated the main route of metabolism of cyclohexane by this Xanthobacter sp. to proceed via cyclohexane --> cyclohexanol --> cyclohexanone --> 1-oxa-2-oxocycloheptane (epsilon-caprolactone) --> 6-hydroxyhexanoate (6-hydroxycaproate) --> --> adipic acid. Alternative routes involving initial double hydroxylation of the cyclohexane ring may operate fortuituously but are unlikely to represent major pathways for the dissimilation of cyclohexane by this microorganism.

Journal Article↗

Methane fermentation of ferulate and benzoate: anaerobic degradation pathways.

The anaerobic biodegradation of ferulate and benzoate in stabilized methanogenic consortia was examined in detail. Up to 99% of the ferulate and 98% of the benzoate were converted to carbon dioxide and methane. Methanogenesis was inhibited with 2-bromoethanesulfonic acid, which reduced the gas production and enhanced the buildup of intermediates. Use of high-performance liquid chromatography and two gas chromatographic procedures yielded identification of the following compounds: caffeate, p-hydroxycinnamate, cinnamate, phenylpropionate, phenylacetate, benzoate, and toluene during ferulate degradation; and benzene, cyclohexane, methylcyclohexane, cyclohexanecarboxylate, cyclohexanone, 1-methylcyclohexanone, pimelate, adipate, succinate, lactate, heptanoate, caproate, isocaproate, valerate, butyrate, isobutyrate, propionate, and acetate during the degradation of either benzoate or ferulate. Based on the identification of the above compounds, more complete reductive pathways for ferulate and benzoate are proposed.

Journal Article↗

Comparative study of the ability of three xanthobacter species to metabolize cycloalkanes.

The ability of three species of Xanthobacter to metabolize cyclohexane and its derivatives has been compared. Xanthobacter flavus was unable to utilize any of the cycloalkanes under investigation. X. autotrophicus was unable to utilize cyclohexane but was able to grow with a limited range of substituted cycloalkanes, including cyclohexanol and cyclohexanone. Comparison of a previously isolated cyclohexane growing Xanthobacter sp. with X. flavus and X. autotrophicus indicated it to be closely related to X. autotrophicus. Studies with cell-free extracts have indicated that the route of metabolism for cyclohexanol by X. autotrophicus is the same as that shown for the cyclohexane growing Xanthobacter sp., proceeding via cyclohexanol-->cyclohexanone--> epsilon-caprolactone-->--> adipic acid. A comparison of the cyclohexanol dehydrogenase found in X. autotrophicus with that found in the cyclohexane-growing Xanthobacter sp. indicated these enzymes to be distinctly different from one another on the basis of substrate specificity, molecular weight, and pH optima. The cyclohexanone monooxygenase enzymes found in the two bacteria were also found to be different when the pH optima and cofactor specificity of the two enzymes were compared. Preliminary genetic studies on the cyclohexane-growing Xanthobacter sp. have indicated that there are no plasmids present in this bacterium. The presence of RP4 in the Xanthobacter sp. can be detected following its conjugation with an RP4-carrying Escherichia coli strain.

Journal Article↗

Identification of metabolites from the degradation of fluoranthene by Mycobacterium sp. strain PYR-1.

Mycobacterium sp. strain PYR-1, previously shown to extensively mineralize high-molecular-weight polycyclic aromatic hydrocarbons in pure culture and in sediments, degrades fluoranthene to 9-fluorenone-1-carboxylic acid. In this study, 10 other fluoranthene metabolites were isolated from ethyl acetate extracts of the culture medium by thin-layer and high-performance liquid chromatographic methods. On the basis of comparisons with authentic compounds by UV spectrophotometry and thin-layer chromatography as well as gas chromatography-mass spectral and proton nuclear magnetic resonance spectral analyses, the metabolites were identified as 8-hydroxy-7-methoxyfluoranthene, 9-hydroxyfluorene, 9-fluorenone, 1-acenaphthenone, 9-hydroxy-1-fluorenecarboxylic acid, phthalic acid, 2-carboxybenzaldehyde, benzoic acid, phenylacetic acid, and adipic acid. Authentic 9-hydroxyfluorene and 9-fluorenone were metabolized by Mycobacterium sp. strain PYR-1. A pathway for the catabolism of fluoranthene by Mycobacterium sp. strain PYR-1 is proposed.

Biodegradation, Environmental↗