Manganese tolerance in Verbascum olympicum Boiss. affecting elemental uptake and distribution: changes in nicotinic acid levels under stress conditions.

A multielemental determination methodology in conjunction with an organic acid analysis that were supplemented with other stress parameters and an ultrastructural analysis used herein to study Verbascum olympicum Boiss. (Scrophulariaceae) under Mn stress. Uptake and accumulation characteristics of B, Cu, Fe, Mn, Mo, and Zn were evaluated in 8-week-old seedlings grown in Hoagland's nutrient solution and exposed to 5 (CK), 50, and 200 µM MnSO4 for 7 days. Hydrogen peroxide levels were determined to evaluate oxidative stress, and changes in compatible substance levels (total phenolic contents, glutathione and glutathione disulfide levels) were determined to assess antioxidant defense mechanisms. The distribution of manganese on the root surface was characterized by scanning electron microscopy images and energy-dispersive X-ray spectroscopy analysis. The levels of nicotinic acid, which is involved in nicotinamide adenine dinucleotide biosynthesis, were determined in roots and leaves to assess tolerance mechanisms. V. olympicum exhibited the ability to cope with oxidative stress originating from excessive Mn, while increased Mn concentrations were observed in both roots and leaves. The translocation factor of B was the most affected among other studied elements under the experimental conditions. Total nicotinic acid levels exhibited a trend of reduction in the roots and leaves, which could be attributed to the appropriate metabolic progress associated with oxidative stress based on the nicotinamide adenine dinucleotide cycle that may reach glutathione in response to manganese stress during plant growth.

Urinary Excretion of Niacin Metabolites in Humans After Coffee Consumption.

SCOPE: Coffee is a major natural source of niacin in the human diet, as it is formed during coffee roasting from the alkaloid trigonelline. The intention of our study was to monitor the urinary excretion of niacin metabolites after coffee consumption under controlled diet. METHODS AND RESULTS: We performed a 4-day human intervention study on the excretion of major niacin metabolites in the urine of volunteers after ingestion of 500 mL regular coffee containing 34.8 µmol nicotinic acid (NA) and 0.58 µmol nicotinamide (NAM). In addition to NA and NAM, the metabolites N1 -methylnicotinamide (NMNAM), N1 -methyl-2-pyridone-5-carboxamide (2-Py), and nicotinuric acid (NUA) were identified and quantified in the collected urine samples by stable isotope dilution analysis (SIVA) using HPLC-ESI-MS/MS. Rapid urinary excretion was observed for the main metabolites (NA, NAM, NMNAM, and 2-Py), with tmax values within the first hour after ingestion. NUA appeared in traces even more rapidly. In sum, 972 nmol h-1 of NA, NAM, NMNAM, and 2-Py were excreted within 12 h after coffee consumption, corresponding to 6% of the ingested NA and NAM. CONCLUSION: The results indicate regular coffee consumption to be a source of niacin in human diet.

Integrated Analytical and Statistical Two-Dimensional Spectroscopy Strategy for Metabolite Identification: Application to Dietary Biomarkers.

A major purpose of exploratory metabolic profiling is for the identification of molecular species that are statistically associated with specific biological or medical outcomes; unfortunately, the structure elucidation process of unknowns is often a major bottleneck in this process. We present here new holistic strategies that combine different statistical spectroscopic and analytical techniques to improve and simplify the process of metabolite identification. We exemplify these strategies using study data collected as part of a dietary intervention to improve health and which elicits a relatively subtle suite of changes from complex molecular profiles. We identify three new dietary biomarkers related to the consumption of peas (N-methyl nicotinic acid), apples (rhamnitol), and onions (N-acetyl-S-(1Z)-propenyl-cysteine-sulfoxide) that can be used to enhance dietary assessment and assess adherence to diet. As part of the strategy, we introduce a new probabilistic statistical spectroscopy tool, RED-STORM (Resolution EnhanceD SubseT Optimization by Reference Matching), that uses 2D J-resolved 1H NMR spectra for enhanced information recovery using the Bayesian paradigm to extract a subset of spectra with similar spectral signatures to a reference. RED-STORM provided new information for subsequent experiments (e.g., 2D-NMR spectroscopy, solid-phase extraction, liquid chromatography prefaced mass spectrometry) used to ultimately identify an unknown compound. In summary, we illustrate the benefit of acquiring J-resolved experiments alongside conventional 1D 1H NMR as part of routine metabolic profiling in large data sets and show that application of complementary statistical and analytical techniques for the identification of unknown metabolites can be used to save valuable time and resources.

Effect of charge and lipid concentration on in-vivo percutaneous absorption of methyl nicotinate from liposomal vesicles.

We have investigated the influence of charge and lipid concentration on the in-vivo percutaneous absorption of a model compound, methyl nicotinate (MN), from liposomal vesicles. MN-loaded liposomes were produced by the reverse-phase evaporation method (REV) using different concentrations of phosphatidyl choline (PC), in association with surfactants such as dioctadecyl dimethyl ammonium bromide (DDAB18) and dicetyl phosphate (DCP), which impart a positive or negative charge to the systems, respectively. The liposomal suspensions were then processed to hydrogels and used to study in-vivo the MN permeation profile. MN was chosen as the model compound since it was capable of causing cutaneous erythema, the intensity and duration of which was proportional to the amount entering the living epidermis over time. The extent of the erythema was monitored by reflectance spectrophotometry, a non-invasive technique. In-vivo findings showed an interesting MN delayed release, which was proportional to the amount of phospholipids in each liposomal formulation. Furthermore, it could be noted that the erythematous effect was more prolonged when MN was delivered from neutral or negatively-charged liposomal forms.

Tazarotene: therapeutic strategies in the treatment of psoriasis, acne and photoaging.

Tazarotene is a member of the new generation of receptor-selective, synthetic retinoids for the topical treatment of mild to moderate plaque psoriasis, acne vulgaris and photoaging. Though they are effective in monotherapy, clinical studies with a focus on novel combination treatments and a comparison of different agents for these skin disorders are accumulating. The concomitant use of tazarotene with a mid-potency or high-potency corticosteroid enhances the efficacy in psoriatic plaques and reduces the risk of steroid-induced skin atrophy. Combining phototherapy with adjunctive tazarotene accelerates the clinical response and reduces the cumulative UVB or PUVA exposure load. Tazarotene applied once daily is superior to adapalene monotherapy in acne vulgaris and is efficacious in the treatment of photodamage. Novel therapeutic regimens such as short-contact therapy have been developed for both acne and psoriasis in order to diminish the major adverse events like pruritus, burning, local skin irritation and erythema.

Cytochrome P-450 isoforms involved in carboxylic acid ester cleavage of Hantzsch pyridine ester of pranidipine.

Cytochrome P-450 (CYP) isoforms responsible for the cleavage of Hantzsch pyridine ester at the 3-position of pranidipine were studied in vitro using cDNA-expressed human CYP enzymes. CYP1A1, 1A2, 2D6, and 3A4 cleaved the ester with a catalytic activity of 5.5, 0. 93, 13.1, and 22.4 nmol/30 min/nmol P-450, respectively. CYP2A6, 2B6, 2C8, 2C9, 2C19, and 2E1 were not involved in the de-esterification. The Km and Vmax values for the de-esterification were 11.8 microM and 0.47 nmol/min/nmol P-450 in the CYP2D6-catalyzed reaction and 8. 7 microM and 0.84 nmol/min/nmol P-450 in the CYP3A4-catalyzed reaction. The intrinsic clearance (Vmax/Km) of the de-esterification by CYP3A4 was 2-fold greater than that by CYP2D6. Quinidine almost completely inhibited the CYP2D6-mediated de-esterification at the concentration of 1 x 10(-6) M. Ketoconazole and troleandomycin inhibited the CYP3A4-mediated reaction in a dose-related manner. The results indicate that although the multiple CYP isoforms can catalyze the de-esterification, CYP3A4 and 2D6 are the major isoforms.

Purification and properties of biologically active chromium complex from bovine colostrum.

A biologically active, low-molecular-weight, chromium-binding substance present in milk (M-LMCr) was isolated from bovine colostrum and purified more than 2000 times by means of ethanol precipitation and successive ion-exchange and Sephadex gel chromatographies. The purified M-LMCr appeared to be an anionic organic Cr compound with a molecular weight of 1500, as determined by gel permeation chromatography. It contained aspartic acid, glutamic acid, glycine and cysteine in a ratio of 5:4:2:1 and no detectable carbohydrate. Although we were unable to detect nicotinic acid, some ultraviolet-absorbing (lambda max 260 nm) chemical structure was shown to be a constituent. Purified M-LMCr stimulated the rates of both [U-14C]glucose oxidation and [3-3H]glucose conversion into lipid in rat epididymal adipocytes at Cr concentrations greater than 1.5 ng/mL in relation to insulin action. This substance appears to have properties similar to those of glucose tolerance factor in yeast and the low-molecular-weight, chromium-binding substance present in mammalian liver. The role of M-LMCr in Cr nutrition and detoxication is discussed.

Nicotinic acid or N-methyl nicotinamide prolongs elevated brain dopa and dopamine in L-dopa treatment.

A peripheral dopa decarboxylase inhibitor, benserazide, was given ip, followed by intubation with L-dopa. Brain dopa and DA levels were elevated maximally between 0.5-2.5 hr and 1.0-2.5 hr, respectively. Dopa in serum, liver, and brain were at control values after 4 hr. Supplementation of dopa with NAM or NAC, as possible methyl group acceptors to lower catabolism of DA, showed that NAM had no effect on DA levels or on SAM. However, with both NAC and N-methyl NAM (a methylated compound intended as a control) at time periods where dopa and DA were normally decreasing, the brain levels were increased over control values with benserazide and dopa alone. NAC or N-methyl NAM appeared to extend the period of elevated brain DA levels with L-dopa treatment. The mechanism responsible for these results is uncertain.

Changes in the affinity of [3H]nimodipine binding sites in the brain upon chlorpromazine treatment and subsequent withdrawal.

Male mice were chronically treated with chlorpromazine mixed in powdered diet, and the properties of brain calcium channels were assessed using [3H]nimodipine binding. It was found that this treatment resulted in a significant increase in the affinity of calcium channels, without a significant change in their density. These effects of chlorpromazine were time dependent. When mice were administered chlorpromazine for 2 months, then the drug was withdrawn, there was a rebound decrease in the channel affinity.

Effect of vitamin E on IgE antibody formation in mice.

Effect of vitamin E (alpha-tocopheryl acetate and alpha-tocopheryl nicotinate) on IgE antibody formation in mice was investgiated . Female BALB/c mice were immunized with dinitrophenylated ascaris protein (DNP-As) and aluminium hydroxide gel (alum). Supplementation of vitamin E in diets or oral administration of vitamin E mixed with sesame oil resulted in a suppression of IgE antibody formation. On the contrary to IgE antibody formation, IgM or IgG (hemagglutinin; HA) formation was significantly enhanced. These results indicate that vitamin E is capable of suppressing IgE antibody formation and enhancing non-IgE antibody formation.

Cerebral arterial spasm--a controlled trial of nimodipine in patients with subarachnoid hemorrhage.

We enrolled 125 neurologically normal patients with intracranial aneurysms in a multi-institution, prospective, double-blind, randomized, placebo-controlled trial within 96 hours of their subarachnoid hemorrhage, to determine whether treatment with the calcium blocker nimodipine would prevent or reduce the severity of ischemic neurologic deficits from arterial spasm. A deficit from cerebral arterial spasm that persisted and was severe or caused death by the end of the 21-day treatment period occurred in 8 of 60 patients given placebo and in 1 of 56 given nimodipine (P = 0.03, Fisher's exact test). Analysis of the amount of basal subarachnoid blood on pre-entry CAT scans in patients with deficits from spasm showed that an increase in subarachnoid blood was not associated with a worse neurologic outcome among patients who received nimodipine, unlike the situation in patients given a placebo. There were no side effects from nimodipine. We conclude that nimodipine should be given to patients who are neurologically normal after subarachnoid hemorrhage in order to reduce the occurrence of severe neurologic deficits due to cerebral arterial spasm.

Niacin requirement for growth of axenic Entamoeba histolytica.

Niacin (nicotinic acid) was found to be essential for the cultivation of axenic Entamoeba histolytica. This vitamin requirement was also satisfied by nicotinamide. Panmede liver digest, a source of vitamins in the axenic medium was replaced with a dialyzed hot water extract of homogenized whole liver, supplemented with various growth factors. Cultured medium made with the liver extract and not supplemented with niacin failed to support continued multiplication of E. histolytica, but did support serial subculture when niacin was added. The concentration of added niacin required to achieve maximum growth was about 1 microgram per ml of medium. This is the first demonstration of a niacin requirement by the organism.

Excretion of tryptophan-niacin metabolites by young men: effects of tryptophan, leucine, and vitamin B6 intakes.

Three human metabolic studies, each 35 days in length, were performed to investigate the relationship between tryptophan intake and the proportion of dietary tryptophan converted to niacin and the effect of supplements of L-leucine and vitamin B6 on this conversion. Nine college men consumed a basal diet that provided 8 mg of niacin, 1 mg of vitamin B6, and either 245, 548, or 845 mg of tryptophan from proteins per day. During each 35-day study, for one 15-day period basal diet alone was consumed, for another 15-day period basal diet plus 10 g of L-leucine per day was consumed, and for the last 5-day period, 20 mg of vitamin B6 per day was added to the diets of both groups. N1-methylnicotinamide, N1-methyl-2-pyridone-5-carboxamide, and quinolinic acid were measured in 24-hr urine samples. There were no significant or consistent effects of L-leucine or vitamin B6 supplements on the excretin of any of the metabolites measured. The proportion of tryptophan converted to niacin tended to increase as tryptophan consumption increased; however, this change was small and was probably not significant over the range of tryptophan intakes studied. The average conversion ration of tryptophan to niacin was approximately 72:1 in these subjects.

Selenium-dependent enzymes.

Selenium, molecular weight 78.96, resembles sulfur in many of its chemical properties and occurs in inorganic forms as H2Se, H2Se2O3, H2SeO3, and H2SeO4 which are the analogues of hydrogen sulfide, thiosulfate, sulfite, and sulfate, respectively. The commonly available radionuclide, 75Se, is a gamma emitter (half-life 122 days) that is used extensively as a tracer in biochemical studies and as a radiopharmaceutical agent for diagnostic purposes. Organoselenium compounds, in general, are less stable and more reactive than the corresponding sulfur analogues and these properties may account for the toxicity of selenium when it is incorporated indiscriminately in place of sulfur in cellular constituents. On the other hand living systems may have exploited the greater reactivity of certain types of organoselenium compounds in those instances where selenium is specifically required as a component of an enzyme or other macromolecule. Several enzymic processes that do not distinguish selenium from sulfur and therefore may be important in selenium toxicity were discussed in some detail in two earlier reviews on selenium biochemistry (1, 2) and this aspect of the problem is not treated here. Rather, the information currently available on the properties and catalytic functions of the four known selenium-dependent enzymes is summarized. These enzymes are formate dehydrogenases of Escherichia coli and several anaerobic bacteria, clostridial glycine reductase, mammalian and avian glutathione peroxidase, and nicotinic acid hydroxylase of Clostridium barkeri. Additional selenoproteins whose catalytic activities are as yet unidentified are mentioned.

[Mechanism of the anti-arrhythmia action of potassium and magnesium nicotinates]. / K mekhanizmu antiaritmicheskogo distviia nikotinatov kaliia i magniia.

It has been shown in rat experimental aconitinic arrhythmia and in dog postinfarction arrhythmia that combined potassium and magnesium nicotinates show a pronounced anti-arrhythmic effect. The studies on the drug distribution in the tissues indicate that the content of potassium, magnesium and total coenzymatic forms of nicotinic acid rises in the myocardium by the 12th hour from the commencement of the drug administration. Intracellular and exocellular content of potassium and sodium has been shown to return to normal.

Pyridine nucleotide cycle of Salmonella typhimurium: regulation of nicotinic acid phosphoribosyltransferase and nicotinamide deamidase.

Nicotinic acid phosphoribosyl transferase (NAPRTase) and nicotinamide deamidase activities from Salmonella typhimurium were examined regarding their regulation by either feedback inhibition or repression mechanisms. The results indicate that neither enzyme is subject to feedback inhbition. Nicotinamide deamidase does not appear to be under repression control. NAPRTase, however, is repressed when cells are grown in minimal medium supplemented with various intermediates of the pyridine nucleotide cycle. The concentration of exogenously supplied pyridine nucleotide necessary to effect repression of NAPRTas was found to be that concentration which will result in a nadA mutant generation time of less than 60 min. Furthermore, the results presented indicate that nicotinamide adenine dinucleotide is the actual corepressor molecule. The analogs 6-aminonicotinic acid and 6-aminonicotinamide were also capable of repressing NAPRTase, but only when an intact pyridine nucleotide cycl permitted conversion to 6-aminonicotinamide adenine dinucleotide. The role of a repressible NAPRTase is discussed in relation to the overall functioning of the pyridine nucleotide cycle.

The effect of a high level of dietary leucine on the niacin status of chicks and rats.

Baby chicks were fed purified diets containing 90 g/kg casein and 100 g/kg gelatin. With low levels of niacin and tryptophan, niacin deficiency resulted: this was not exacerbated by the addition of supplementary leucine (17.4 g/kg). With levels of niacin and tryptophan that supported rapid growth the further addition of supplementary leucine depressed food consumption and weight gain; in most instances this was statistically significant. No evidence was obtained to indicate that a high level of dietary leucine could result in niacin deficiency in chicks. Comparable experiments were carried out with weanling rats given a basal diet containing 60 g/kg casein and 60 g/kg gelatin. Adding 15 g/kg L-leucine gave results similar to those obtained with chicks and the same conclusions were drawn.

The effect of a high level of dietary leucine on the niacin status of dogs.

Two feeding trials were designed to precipitate niacin deficiency in puppies receiving low levels of niacin by adding 15 g/kg supplementary l-leucine to a diet containing 180 g/kg casein. We failed to produce such an effect and, as niacin levels were gradually reduced, the times at which control dogs became deficient (and then responded to injections of the vitamin) were not significantly different from those for dogs receiving the leucine supplement. Differences between the conditions of our experiments and of the experiment in which this effect was found are discussed. Two pairs of littermates in trial 2 died suddenly while apparently in fairly good condition, but revealing fatty livers and/or changes in heart muscle on autopsy. Similar observations have been reported by others using purified diets with dogs over long periods; there is no certain explanation.

Effect of nicotinic acid on catecholamine synthesis in rat brain.

Effect of nicotinic acid on the formation of catecholamine has been studied. Norepinephrine and dopamine concentrations in brain were 30 per cent higher and brain catecholamine formation was 50 per cent higher in the nicotinic acid-supplemented rats than the nicotinic acid-deficient rats. However, these catecholamine levels of the nicotinic acid-deficient rats were recovered by the administration of nicotinic acid. The concentration of brain tyrosine was unaltered after administration of nicotinic acid to the nicotinic acid-deficient rats. Therefore, the changes catecholamine formation by the nicotinic acid supplementation were not due to the difference of tyrosine concentration in the brain which is the precursor for catecholamine biosynthesis. As the difference of catecholamine concentration between the nicotinic acid deficient and the nicotinic acid supplemented group was smaller than that of catecholamine formation of these groups, the turnover of catecholamine was supposed to be decreased in nicotinic acid deficiency.