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(1/4452) The direct spectrophotometric observation of benzo(a)pyrene phenol formation by liver microsomes.

Optical spectral repetitive scan analysis during the oxidative metabolism of benzo(a)pyrene by liver microsomal suspensions reveals the time-dependent formation of an intermediate(s) of which the visible spectra resemble those of several benzo(a)pyrene phenols. Liver microsomes from 3-methylcholanthrene-treated rats showed a greater rate of formation of the phenols than did microsomes from control animals; the rate of formation catalyzed by liver microsomes from phenobarbital-pretreated rats was intermediate. When 3-hydroxybenzo(a)pyrene was used as a standard for comparison of activity, the rates of formation of phenols were compared when measured by fluorometric, spectrophotometric, or high-pressure liquid chromatographic analytical techniques. An epoxide hydrase inhibitor, 1,1,1-trichloropropene-2,3-oxide, enhanced phenol formation regardless of the source of liver microsomes, and 7,8-benzoflavone inhibited control and 3-methylcholanthrene-induced microsomal metabolism of benzo(a)pyrene, 7,8-Benzoflavone did not effect benzo(a)pyrene metabolism by liver microsomes from phenobarbital-pretreated rats. The effect of inhibitors on the spectrophotometric assay correlates well with the results obtained from benzo(a)pyrene metabolite analysis using high-pressure liquid chromatography.  (+info)

(2/4452) Hierarchical cluster analysis applied to workers' exposures in fiberglass insulation manufacturing.

The objectives of this study were to explore the application of cluster analysis to the characterization of multiple exposures in industrial hygiene practice and to compare exposure groupings based on the result from cluster analysis with that based on non-measurement-based approaches commonly used in epidemiology. Cluster analysis was performed for 37 workers simultaneously exposed to three agents (endotoxin, phenolic compounds and formaldehyde) in fiberglass insulation manufacturing. Different clustering algorithms, including complete-linkage (or farthest-neighbor), single-linkage (or nearest-neighbor), group-average and model-based clustering approaches, were used to construct the tree structures from which clusters can be formed. Differences were observed between the exposure clusters constructed by these different clustering algorithms. When contrasting the exposure classification based on tree structures with that based on non-measurement-based information, the results indicate that the exposure clusters identified from the tree structures had little in common with the classification results from either the traditional exposure zone or the work group classification approach. In terms of the defining homogeneous exposure groups or from the standpoint of health risk, some toxicological normalization in the components of the exposure vector appears to be required in order to form meaningful exposure groupings from cluster analysis. Finally, it remains important to see if the lack of correspondence between exposure groups based on epidemiological classification and measurement data is a peculiarity of the data or a more general problem in multivariate exposure analysis.  (+info)

(3/4452) Complete sequence of a 184-kilobase catabolic plasmid from Sphingomonas aromaticivorans F199.

The complete 184,457-bp sequence of the aromatic catabolic plasmid, pNL1, from Sphingomonas aromaticivorans F199 has been determined. A total of 186 open reading frames (ORFs) are predicted to encode proteins, of which 79 are likely directly associated with catabolism or transport of aromatic compounds. Genes that encode enzymes associated with the degradation of biphenyl, naphthalene, m-xylene, and p-cresol are predicted to be distributed among 15 gene clusters. The unusual coclustering of genes associated with different pathways appears to have evolved in response to similarities in biochemical mechanisms required for the degradation of intermediates in different pathways. A putative efflux pump and several hypothetical membrane-associated proteins were identified and predicted to be involved in the transport of aromatic compounds and/or intermediates in catabolism across the cell wall. Several genes associated with integration and recombination, including two group II intron-associated maturases, were identified in the replication region, suggesting that pNL1 is able to undergo integration and excision events with the chromosome and/or other portions of the plasmid. Conjugative transfer of pNL1 to another Sphingomonas sp. was demonstrated, and genes associated with this function were found in two large clusters. Approximately one-third of the ORFs (59 of them) have no obvious homology to known genes.  (+info)

(4/4452) Isolation from estuarine sediments of a Desulfovibrio strain which can grow on lactate coupled to the reductive dehalogenation of 2,4, 6-tribromophenol.

Strain TBP-1, an anaerobic bacterium capable of reductively dehalogenating 2,4,6-tribromophenol to phenol, was isolated from estuarine sediments of the Arthur Kill in the New York/New Jersey harbor. It is a gram-negative, motile, vibrio-shaped, obligate anaerobe which grows on lactate, pyruvate, hydrogen, and fumarate when provided sulfate as an electron acceptor. The organism accumulates acetate when grown on lactate and sulfate, contains desulfoviridin, and will not grow in the absence of NaCl. It will not utilize acetate, succinate, propionate, or butyrate for growth via sulfate reduction. When supplied with lactate as an electron donor, strain TBP-1 will utilize sulfate, sulfite, sulfur, and thiosulfate for growth but not nitrate, fumarate, or acrylate. This organism debrominates 2-, 4-, 2,4-, 2,6-, and 2,4,6-bromophenol but not 3- or 2,3-bromophenol or monobrominated benzoates. It will not dehalogenate monochlorinated, fluorinated, or iodinated phenols or chlorinated benzoates. Together with its physiological characteristics, its 16S rRNA gene sequence places it in the genus Desulfovibrio. The average growth yield of strain TBP-1 grown on a defined medium supplemented with lactate and 2,4,6-bromophenol is 3.71 mg of protein/mmol of phenol produced, and the yield was 1.42 mg of protein/mmol of phenol produced when 4-bromophenol was the electron acceptor. Average growth yields (milligrams of protein per millimole of electrons utilized) for Desulfovibrio sp. strain TBP-1 grown with 2,4,6-bromophenol, 4-bromophenol, or sulfate are 0.62, 0.71, and 1.07, respectively. Growth did not occur when either lactate or 2,4,6-bromophenol was omitted from the growth medium. These results indicate that Desulfovibrio sp. strain TBP-1 is capable of growth via halorespiration.  (+info)

(5/4452) In vivo demonstration of H3-histaminergic inhibition of cardiac sympathetic stimulation by R-alpha-methyl-histamine and its prodrug BP 2.94 in the dog.

1. The aim of this study was to investigate whether histamine H3-receptor agonists could inhibit the effects of cardiac sympathetic nerve stimulation in the dog. 2. Catecholamine release by the heart and the associated variation of haemodynamic parameters were measured after electrical stimulation of the right cardiac sympathetic nerves (1-4 Hz, 10 V, 10 ms) in the anaesthetized dog treated with R-alpha-methyl-histamine (R-HA) and its prodrug BP 2.94 (BP). 3. Cardiac sympathetic stimulation induced a noradrenaline release into the coronary sinus along with a tachycardia and an increase in left ventricular pressure and contractility without changes in mean arterial pressure. Intravenous administration of H3-receptor agonists significantly decreased noradrenaline release by the heart (R-HA at 2 micromol kg(-1) h(-1): +77 +/- 25 vs +405 +/- 82; BP 2.94 at 1 mg kg(-1): +12 +/- 11 vs +330 +/- 100 pg ml(-1) in control conditions, P < or = 0.05), and increases in heart rate (R-HA at 2 micromol kg(-1) h(-1): +26 +/- 8 vs +65 +/- 10 and BP 2.94 at 1 mg kg(-1): +30 +/- 8 vs 75 +/- 6 beats min(-1), in control conditions P < or = 0.05), left ventricular pressure, and contractility. Treatment with SC 359 (1 mg kg(-1)) a selective H3-antagonist, reversed the effects of H3-receptor agonists. Treatment with R-HA at 2 micromol kg(-1) h(-1) and BP 2.94 at 1 mg kg(-1) tended to decrease, while that with SC 359 significantly increased basal heart rate (from 111 +/- 3 to 130 +/- 5 beats min(-1), P < or = 0.001). 4. Functional H3-receptors are present on sympathetic nerve endings in the dog heart. Their stimulation by R-alpha-methyl-histamine or BP 2.94 can inhibit noradrenaline release by the heart and its associated haemodynamic effects.  (+info)

(6/4452) Antioxidative and chelating activities of phenylpropanoid glycosides from Pedicularis striata.

AIM: To study the antioxidative and iron chelating activities of phenylpropanoid glycosides (PPG) isolated from a Chinese herb Pedicularis striata. METHODS: Antioxidative effects of PPG on lipid peroxidation induced by FeSO4-edetic acid in linoleic acid were measured by thiobarbituric acid method. Chelating activities of PPG for Fe2+ were tested by differential spectrum method. RESULTS: The reaction rates (A532.min-1) of lipid peroxidation were 0.0046 in the control, 0.0021 in verbascoside group, and 0.0008 in isoverbascoside group. The chelating activity of isoverbascoside was 2-fold stronger than that of verbascoside. Permethyl verbascoside showed neither antioxidative nor chelating activities. CONCLUSION: The inhibitory effects of PPG with phenolic hydroxy groups on lipid peroxidation are owing to their chelating properties. Under physiological condition PPG-Fe2+ chelates are sufficiently stable. Thus PPG are able to inhibit the Fe(2+)-dependent lipid peroxidation in vivo through chelating Fe2+ and exhibit their therapeutic potential by the same mechanism in vitro.  (+info)

(7/4452) Developing hypothalamic dopaminergic neurones as potential targets for environmental estrogens.

Environmental chemicals which mimic the actions of estrogen have the potential to affect any estrogen responsive tissue. The aim of the present study was to investigate their potential to mimic the effects of 17beta-estradiol (E2) on developing primary rat hypothalamic dopaminergic (DA) neurones maintained in a chemically defined medium. We now show that both E2 and octylphenol (OP), but not the non-aromatizable androgen, dihydrotestosterone, enhanced the uptake of [3H]DA by the cultured cells, whereas they had no effect on the uptake of [14C]GABA. Although the sensitivity of responses may change with the age of the developing cultures, the dose response curves for E2 and OP were typically 'bell-shaped', with a rise in response followed by a decline to control levels with increasing concentrations. Effects were seen as low as 10(-14) M for E2 and 10(-11) M for OP. Responses to E2 (10(-12) M) and OP (10(-9) M) were reversed in the presence of the antiestrogen, ZM 182780 (10(-5) M). This study thus provides direct evidence, using a mechanistic rather than toxicological end-point, in support of the hypothesis that inappropriate exposure to environmental estrogens at critically sensitive stages of development, could potentially perturb the organisational activities of estrogen on selected neuronal populations in the CNS.  (+info)

(8/4452) Characterization of the pyoluteorin biosynthetic gene cluster of Pseudomonas fluorescens Pf-5.

Ten genes (plt) required for the biosynthesis of pyoluteorin, an antifungal compound composed of a bichlorinated pyrrole linked to a resorcinol moiety, were identified within a 24-kb genomic region of Pseudomonas fluorescens Pf-5. The deduced amino acid sequences of eight plt genes were similar to the amino acid sequences of genes with known biosynthetic functions, including type I polyketide synthases (pltB, pltC), an acyl coenzyme A (acyl-CoA) dehydrogenase (pltE), an acyl-CoA synthetase (pltF), a thioesterase (pltG), and three halogenases (pltA, pltD, and pltM). Insertions of the transposon Tn5 or Tn3-nice or a kanamycin resistance gene in each of these genes abolished pyoluteorin production by Pf-5. The presumed functions of the eight plt products are consistent with biochemical transformations involved in pyoluteorin biosynthesis from proline and acetate precursors. Isotope labeling studies demonstrated that proline is the primary precursor to the dichloropyrrole moiety of pyoluteorin. The deduced amino acid sequence of the product of another plt gene, pltR, is similar to those of members of the LysR family of transcriptional activators. pltR and pltM are transcribed divergently from the pltLABCDEFG gene cluster, and a sequence with the characteristics of a LysR binding site was identified within the 486-bp intergenic region separating pltRM from pltLABCDEFG. Transcription of the pyoluteorin biosynthesis genes pltB, pltE, and pltF, assessed with transcriptional fusions to an ice nucleation reporter gene, was significantly greater in Pf-5 than in a pltR mutant of Pf-5. Therefore, PltR is proposed to be a transcriptional activator of linked pyoluteorin biosynthesis genes.  (+info)