CSF and urine biogenic amine metabolites in Rett syndrome

The metabolites of dopamine (homovanillic acid-HVA), noradrenaline (4-hydroxy-3-methoxy-phenylglycol-HMPG), and serotonin (5-hydroxyindoleacetic acid-5-HIAA) were measured in cerebrospinal fluid (CSF) from 38 patients and urine from 36 patients with typical Rett syndrome (RS) and compared with controls of similar age. CSF metabolite concentrations were the same in the patients and controls. Urinary metabolites expressed per mol creatinine were significantly higher in older RS patients. This difference is partly explained by lower urinary creatinine levels in older RS patients, due to their known reduction in muscle mass. Alterations in CSF or urine biogenic amine metabolite concentrations do not appear to represent the primary abnormality in RS, and their measurement cannot be regarded as a reliable means of diagnosis.     

Alteration of shivering threshold in cold-and warm-adapted guinea pigs following intrahypothalamic injections of noradrenaline and of an adrenergic alpha-receptor blocking agent

Summary The role of adrenergic receptors in the central thermoregulatory pathways controlling the shivering activity has been studied in groups of cold-adapted (CA), warm-adapted (WA) and newborn (NB) guinea pigs, which show quantitative differences in shivering threshold. In the CA and NB animals, which normally start to shiver at lower mean body temperature levels than the WA controls, microinjection of noradrenaline (1 g in 1 l) into the noradrenaline-sensitive area of the anterior hypothalamus elicited shivering at higher body temperatures at which normally only WA animals start to shiver. Similar injections into the hypothalamus of WA animals did not induce any further shift of the shivering threshold. Microinjections of the alpha-receptor blocking agent phentolamine into the same brain area shifted the shivering threshold in all groups of animals to lower body temperatures, the shift being proportional to the injected dose of phentolamine. The CA and NB animals required higher doses of phentolamine to produce a change in shivering threshold. It is concluded that adrenergic alpha receptors are involved in the central thermoregulatory mechanisms which adjust the thresholds for the thermoregulatory reactions.This study was supported by the Deutsche Forschungsgemeinschaft (SFB 122, Projekt B 1).     

Changes in biogenic amine content in various parts of the rat brain after administration of morphine and amobarbital

The effect of narcotics with different chemical structure (morphine and amobarbital) on the concentrations of dopamine, noradrenalin, serotonin, and its principal metabolite 5-hydroxyindoleacetic acid was investigated in various brain structures in rats. The effects of morphine and amobarbital on the biogenic amine system of the brain were found to depend on the time of their action. Changes produced by the narcotics in catecholamine and indoleamine metabolism differed in the hypothalamus, midbrain, and cortex. Responses of the biogenic amine systems were most marked 60 min after administration of the narcotics.Laboratory of Psychopharmacology, Professor V. P. Serbskii C entral Scientific-Research Institute of Forensic Psychiatry, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR G. V. Morozov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 8, pp. 168–170, August, 1979.     

Resolution of contradiction between in silico predictions and Ames test results for four pharmaceutically relevant impurities

The ICH M7 Guideline requires low level control of mutagenic impurities in pharmaceutical products to minimize cancer risk in patients (ICHM7, 2014). Bacterial mutagenicity (Ames) data is generally used to determine mutagenic and possible carcinogenic potential of compounds. Recently, a publication on experiences of using two in silico systems to identify potentially mutagenic impurities highlighted the importance of performing a critical review of published Ames data utilized as part of a mutagenicity assessment of impurities (Greene et al., 2015). Four compounds (2-amino-5-hydroxybenzoic acid, 2-amino-3-chlorobenzoic acid, methyl 2-amino-4-chlorobenzoate and 4-morpholinopyridine) reported mutagenic were identified in a two system in silico assessment and expert review of the structuresas non-mutagenic. Likely reasons for mutagenicity could not be identified and the purity of the compounds tested was proposed. In the current investigation, the purest available sample of the four compounds was tested in an OECD-compliant Ames test. The compounds were all found to be non-mutagenic. Possible reasons for the discrepancy between previously reported and current results are discussed. Additionally, important points to consider when conducting an expert review of available Ames data are provided particularly in cases where reported Ames results are discrepant with a two system in silico assessment.     

Variability of biogenic amine and free amino acid concentrations in regionally produced goat milk cheeses

The free amino acid composition and biogenic amine content were analysed in pasteurised goat milk cheeses produced in different regions in Spain. These goat cheeses are made with pasteurised milk to which a mesophilic starter culture is added; they are enzymatically coagulated, uncooked, pressed cheeses. They have a firm texture with a slight but typical goat milk aroma and flavour. The total free amino acids varied markedly among the samples, ranging from 1400 to 28,000 mg kg⁻¹ DM (dry matter). Of the 20 amino acids analysed, the most abundant were leucine, proline, valine, glutamic acid, lysine, glutamine, ornithine and γ-aminobutyric acid, which accounted for over 60% of the total free amino acids. The goat milk cheeses presented low concentrations of biogenic amines, the most abundant being tyramine and/or histamine, with values ranging from 4.2 to 50.7 and from 10.2 to 60.5 mg kg⁻¹ DM, respectively. Total biogenic amine content ranged between 26.4 mg kg⁻¹ DM and 175.1 mg kg⁻¹ DM, and was always below the level that is considered dangerous for humans. Therefore, taking into consideration the concentrations of BAs, these goat milk cheeses, produced under good hygienic conditions, can be considered safe for consumers.     

Specificity of base substitution mutations induced by the dietary carcinogens 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in Salmonella

The base pair substitution mutational profiles induced by the heterocyclic amine cooked food mutagens PhIP and IQ in Salmonella typhimurium strains TA100 and TA1535 were determined by colony hybridization analysis. Both PhIP and IQ induced predominantly G→TA transversions in strain TA100 (rfa,ΔuvrB/pKM101) with a pronounced preference for the second codon position (CC→CAC; 72% of total). PhIP also reverted strain TA1535 (rfa, ΔuvrB) efficiently at concentrations similar to those required for strain TA100. In contrast to the PhIP-induced mutational profile observed in strain TA100, in strain TA1535 PhIP induced exclusively G→AT transitions at the second codon position (CC→CTC; 96–99% of total). Base substitution mutagenesis induced by heterocyclic amines related to PhIP is generally SOS-dependent, requiring the presence of plasmid pKM101 in Salmonella hisG46 strains. Thus, the SOS dependent reversion of S. typhimurium strain TA100 probably reflects error-prone lesion bypass at the major PhIP- guanosine adduct at the C-8 position. The G→AT transition mutations induced by PhIP in strain TA1535 appear to be SOS-independent, however, suggesting that these mutations may arise from the formation of PhIP-DNA adducts other than the replication-blocking C8-dG lesion. Environ. Mol. Mutagen. 31:327–332, 1998 © 1998 Wiley-Liss, Inc.     

Induction of mouse cytochrome P450 2B enzymes by amine metabolites of musk xylene: Contribution of microsomal enzyme induction to the hepatocarcinogenicity of musk xylene

Musk xylene (MX) is a synthetic nitromusk perfume ingredient that, although uniformly negative in genotoxicity testing, causes liver tumors in B6C3F1 mice. MX is also capable of inducing cytochrome P450 enzymes in a manner similar to that of phenobarbital (PB), which suggests that epigenetic mechanisms may be involved in the carcinogenic response. At the same time, MX is metabolized in vivo by nitroreduction, a reaction catalyzed by intestinal flora that yields aromatic amine metabolites. These amine metabolites are also capable of inactivating CYP2B10, the major cytochrome P450 enzyme induced by MX treatment. In the study reported here, the monoamine metabolites of MX, o- and p-NH₂-MX, were evaluated for their potential to induce CYP2B10 and CYP1A2 mRNAs. Northern blot analyses indicated that both amines markedly induced CYP2B10 mRNA, whereas CYP1A2 mRNA, the enzyme implicated in the bioactivation of aromatic amines and frequently induced by aromatic amines, was induced only slightly, a response that was not different from that seen with PB. Induction of CYP2B10 mRNA suggested that the amine metabolites may contribute to the enzyme induction profile seen with MX treatment. To test this hypothesis, mice were treated with broad-spectrum antibiotics (neomycin, tetracycline, and bacitracin) to eliminate the intestinal flora and prevent formation of o- and p-NH₂-MX. In antibiotic-treated mice treated with MX (200 mg/kg) for 4 d, no evidence of microsomal enzyme induction was observed, including no increases in liver weight, total cytochrome P450 content, or CYP2B protein levels. These results indicate that the amine metabolites of MX are responsible for the enzyme induction seen after MX administration. Thus, the biochemical and molecular effects of amine metabolites of MX are markedly different from those of other aromatic amines but very similar to those of PB. Therefore, it appears that MX is a non-genotoxic chemical that may cause mouse liver tumors in a manner analogous to that of PB. Mol. Carcinog. 20:308–316, 1997. © 1997 Wiley-Liss, Inc.     

Work-related asthma and respiratory symptoms among workers exposed to metal-working fluids

The objective of this work was to determine whether the prevalence of respiratory symptoms differed among workers exposed to different types of metal-working fluids. As part of a mandatory surveillance system for occupational illness, from 1988-1994, the Michigan Department of Public Health received, 86 occupational disease reports of work-related asthma secondary to exposure to metal-working fluids. As part of a public health program, follow-up industrial hygiene inspections, including medical interviews of the workforce, were performed at companies where the reported cases had become ill. Metal-working fluids were the second most common cause of work-related asthma reported in the state. Most of the reports were from the automobile industry. Follow-up inspections were conducted at 37 facilities where the individuals with work-related asthma had worked. Seven hundred and fifty-five workers at these facilities were interviewed. Only one facility was above the allowable oil mist standard. Despite the exposure levels being within the legal limits, approximately 20% of the fellow workers of the reported cases had daily or weekly respiratory symptoms suggestive of work-related asthma. Workers exposed to emulsified, semisynthetic, or synthetic machining coolants were more likely to have chronic bronchitis; to have visited a doctor for shortness of breath; to have visited a doctor for a sinus problem; to be bothered at work by nasal stuffiness, runny nose, or sore throat; and to have an increased prevalence of respiratory symptoms consistent with work-related asthma, compared to workers exposed to mineral oil metal-working fluids. These findings were found in individuals who currently smoked, had never smoked or were ex-cigarette smokers. Further research to determine the chemical components or microbial contaminants responsible for these findings is needed. Am. J. Ind. Med. 32:325–331, 1997. © 1997 Wiley-Liss, Inc.     

The effects of capsaicin on the metabolic activation of heterocyclic amines and on cytochrome P450 1A2 activity in hamster liver microsomes

Capsaicin, the principal component of Capsicum fruits, strongly inhibited the in vitro mutagenic activity of five heterocyclic amines (HCAs) in Salmonella typhimurium strain TA98 by hamster liver microsomes. This correlated with the inhibition of microsome associated demethylation of methoxyresorufin (MROD) by capsaicin. MROD activity is mediated by cytochrome P450 1A2 and CYP450 1A2 mediates the metabolic activation of HCAs. Enzyme kinetics studies indicated a noncompetitive type of inhibition by capsaicin. Liver microsomes prepared from hamsters 6 h and 24 h after administration of a single oral dose of capsaicin in olive oil at either 2 mg/kg or 10 mg/kg body weight expressed a small but statistically significant inhibition of MROD activity compared with microsomes from control (untreated) animals. These results suggest that capsaicin can modulate the activity of cytochrome P450 1A2. © 1997 John Wiley & Sons, Ltd.