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PubMed1978

Chemical structure and biodegradability of halogenated aromatic compounds. Two catechol 1,2-dioxygenases from a 3-chlorobenzoate-grown pseudomonad.

1. Two catechol 1,2-dioxygenases, pyrocatechase I and pyrocatechase II, were found in 3-chlorobenzoate-grown cells of Pseudomonas sp. B 13. The latter enzyme showed high relative activities with 3- and 4-chlorocatechol compared with catechol. 2. In benzoate-grown cells, only pyrocatechase I was induced. It was purified 29-fold with a final specific activity of 20 mumol of catechol oxygenated/min per mg of protein and an overall yield of 22%. Because of the instability of pyrocatechase II on chromatography and dialysis, no increase of specific activity was obtained during the purification experiments. 3. Molecular weights of pyrocatechase I and pyrocatechase II were 82000 and 67000 respectively. 4. For both pyrocatechases the pH optimum was found to be at 8.0.5. Inhibitions of the two pyrocatechases by Cu2+ and Hg2+ ions and p-chloromercuribenzoate were different. The effect on pyrocatechase I after incubation for 20 h with the heavy metals was decreased by addition of 1 mM-2-mercaptoethanol to the reaction mixture. The inhibition of pyrocatechase II was even enhanced under these conditions. 6. Extradiol cleavage of 3-methylcatechol in addition to intradiol fission at a ratio of 1:14 was observed only with pyrocatechase I.

Benzoates↗
PubMed1980

Erythrocytes catechol-O-methyltransferase activity and indices of sympathetic activity in man.

1. Erythrocyte catechol-O-methyltransferase was studied in a population sample of 147 subjects. 2. There was a wide interindividual variability of catechol-O-methyltransferase activity, which was not unimodally distributed. Catechol-O-methyltransferase activity was not influenced by blood pressure, age or sex, nor was it related to plasma noradrenaline or urinary catecholamines or metanephrines. 3. It is not likely that inactivation of noradrenaline by O-methylation at least by erythrocytes is an important mechanism determining plasma noradrenaline, let alone arterial pressure.

Adolescent↗
PubMed2002

Brain catecholamine metabolism in catechol-O-methyltransferase (COMT)-deficient mice.

Catechol-O-methyltransferase (COMT) catalyses the O-methylation of compounds having a catechol structure and its main function involves the elimination of biologically active or toxic catechols and their metabolites. By means of homologous recombination in embryonic stem cells, a strain of mice has been produced in which the gene encoding the COMT enzyme is disrupted. We report here the levels of catecholamines and their metabolites in striatal extracellular fluid in these mice as well as in homogenates from different parts of the brain, under normal conditions and after acute levodopa administration. In immunoblotting studies, COMT-knockout mice had no COMT protein in brain or kidney tissues but the amounts of catecholamine synthesizing and other metabolizing enzyme proteins were normal. Under normal conditions, COMT deficiency does not appear to affect significantly brain dopamine and noradrenaline levels in spite of relevant changes in their metabolites. This finding is consistent with previous pharmacological studies with COMT inhibitors and confirms the pivotal role of synaptic reuptake processes and monoamine oxidase-dependent metabolism in terminating the actions of catecholamines at nerve terminals. In contrast, when COMT-deficient mice are challenged with l-dihydroxyphenylalanine, they show an extensive accumulation of 3,4-dihydroxyphenylacetic acid and dihydroxyphenylglycol and even dopamine, revealing an important role for COMT under such situations. Notably, in some cases these changes appear to be Comt gene dosage-dependent, brain-region specific and sexually dimorphic. Our results may have implications for improving the treatment of Parkinson's disease and for understanding the contribution of the natural variation in COMT activity to psychiatric phenotypes.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1999

Rapid evaluation of biocidal activity using a transposon-encoded catechol 2,3-dioxygenase from Pseudomonas putida.

Pseudomonas putida (UWC1), containing a genetically-engineered plasmid (pQM899), that encodes for the production of catechol 2,3-dioxygenase (C230), was used as a potential means of rapidly estimating bactericidal activity of chlorhexidine diacetate (CHA), phenol, cetylpyridinium chloride (CPC) and phenylmercuric nitrate (PMN). Enzyme C230 converts catechol to 2-hydroxymuconic semialdehyde (2-HMS), which is yellow in colour, via a meta cleavage pathway. Ideal conditions for production and measurement spectrophotometrically of 2-HMS were determined. However, the correlation between this method and viable plate counts was not sufficiently accurate to enable 2-HMS production to provide a sufficiently sensitive determination of biocidal activity. An alternative method, synchronous scanning fluorimetry, in which the decrease in catechol concentration was measured under standardized conditions, provided a good dose-response histogram for all the biocides tested. Although, in comparison with plate counts, there was an underestimation of the bactericidal effects of phenol an PMN, the results of this study suggest that this method has potential in determining the bactericidal efficacy of agents such as CHA and CPC.

Catechol 2,3-Dioxygenase↗
PubMed1994

Striatal transporter for dopamine: catechol structure-activity studies and susceptibility to chemical modification.

The apparent second-order association rate constant of dopamine binding to the striatal transporter (approximately 1 x 10(6) M-1 s-1) as well as the transporter turnover number (approximately 1.5 s-1) was estimated using rotating disk electrode voltammetry to monitor apparent zero trans entry of dopamine into striatal suspensions. The substrate specificity of the transporter was also assessed using catechol derivatives. Dopamine and norepinephrine were transported, whereas epinephrine and the acidic metabolites of dopamine were not transported. The metabolite, 3-methoxytyramine, was transported with a Km seven times greater than and a Vmax close to that for dopamine. 4-Methoxytyramine was transported more facilely than the 3-methoxy derivative. N-Alkylation of the amine side chain of dopamine reduced transport dramatically. 4-Ethylcatechol and 3,4-dihydroxybenzylamine were transported with velocities 79 and 91% less than that for dopamine, respectively. The rigid analogue 6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene was transported with a greater velocity than the 5,7-dihydroxy derivative. Finally, the apparent Km values for 4-ethylcatechol, 1-amino-2-phenylethane, tyramine, and m-tyramine as cosubstrates with dopamine were 1.1, 11, 17, and 2.6 microM, respectively. Pretreatments of striatal suspensions with chloroethylnorapomorphine, N-ethylmaleimide, Hg2+, 4,5-dihydroxy-4,5-dioxo-1H-pyrrolo[2,3-f] quinoline-2,7,9-tricarboxylic acid (a redox modulator of receptors in neuronal as well as other tissues), and neuraminidase reduced the velocity of transport of dopamine, whereas N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline had no effect. Thus, the dopamine transporter requires an intact catechol with a primary ethylamine side chain for optimal activity relative to shorter side chain derivatives (side chains longer than two carbons were not tested), the 3-hydroxyl group of dopamine is the more critical hydroxyl group, and the beta rotamer of the extended conformation of dopamine is transported preferentially. The catechol appears to mediate the recognition of the substrate, whereas the amine side chain apparently facilitates the conformational change of the transporter that results in movement of dopamine into or across the membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2001

Catechol-O-Methyltransferase (COMT) gene polymorphism and breast cancer risk in young women.

Oestrogen exposure has long been considered to be a main risk factor of breast cancer. More recently, interest has also focused on the possible carcinogenic influence from oestrogen metabolites, such as catechol oestrogens. O-methylation, catalysed by Catechol-O-Methyltransferase (COMT), is one pathway by which the potentially carcinogenic catechol oestrogens can be inactivated. The gene coding for COMT protein contains a single-nucleotide polymorphism (SNP), resulting in an amino acid shift Val-->Met, which has been shown to determine high- and low-activity configuration of the enzyme. We hypothesized that the low-activity allele, COMT(Met), may be implicated in early onset breast cancer. In the present case-control study, including 126 young breast cancer patients (<or= 36 years) and 117 healthy female blood donors, we analysed the association between COMT(Met) genotype and risk of breast cancer. No significant difference in the frequency of low-/high-activity alleles was found between cases and controls, indicating that the polymorphism, as a single factor, may not contribute to breast carcinogenesis in young women.

Adolescent↗
PubMed1991

Human catechol-O-methyltransferase: cloning and expression of the membrane-associated form.

A cDNA clone for human catechol-O-methyltransferase (hCOMT; S-adenosyl-L-methionine:catechol O-methyltransferase; EC 2.1.1.6) was isolated from a human hepatoma cell line (Hep G2) cDNA library by hybridization screening with a porcine cDNA probe. The cDNA clone was sequenced and found to have an insert of 1226 nucleotides. The deduced primary structure of hCOMT is composed of 271 amino acid residues with the predicted molecular mass of 30 kDa. At its N terminus it has a hydrophobic segment of 21 amino acid residues that may be responsible for insertion of hCOMT into the endoplasmic reticulum membrane. The primary structure of hCOMT exhibits high homology to the porcine partial cDNA sequence (93%). The deduced amino acid sequence contains two tryptic peptide sequences (T-22, T-33) found in porcine liver catechol-O-methyltransferase (COMT). The coding region of hCOMT cDNA was placed under the control of the cytomegalovirus promoter to transfect human kidney 293 cells. The endogenous COMT activity, which was approximately 9.98 units per mg of protein in the untransfected cells, increased to 206 units per mg of protein upon transfection with a plasmid containing the COMT cDNA. The COMT activity of recombinant protein was inhibited competitively (IC50 = 700 nM) by the selective COMT inhibitor Ro 40-7592. An anti-COMT monoclonal antibody recognized, on immunoblots, a major polypeptide with apparent molecular mass of 29 kDa, in reasonable agreement with the predicted molecular mass. The recombinant hCOMT was shown by immunoblot analysis to be mainly associated with the membrane fraction. RNA blot analysis revealed one COMT mRNA transcript of 1.4 kilobases in Hep G2 poly(A)+ RNA.

Amino Acid Sequence↗
PubMed1998

A novel -2Fe-2S- ferredoxin from Pseudomonas putida mt2 promotes the reductive reactivation of catechol 2,3-dioxygenase.

Catechol 2,3-dioxygenase (XylE) is a component of the TOL plasmid-encoded pathway for the degradation of toluene and xylenes and catalyzes the dioxygenolytic cleavage of the aromatic ring. Purified XylE is oxygen-sensitive and unstable in vitro, particularly in the presence of substituted catechol substrates, but it is stabilized in vivo by another protein, XylT, encoded by the xylT gene located just upstream of xylE. In this study, we have purified to homogeneity the XylT product from a recombinant Escherichia coli strain containing a hyperexpressible xylT gene and characterized it as a novel [2Fe-2S] ferredoxin. It is the first example of a soluble ferredoxin with a net positive charge at neutral pH. The EPR signal of the iron sulfur cluster has rhombic symmetry as is the case for plant-type ferredoxins, but the XylT absorbance spectrum resembles more closely that of adrenodoxin. The midpoint redox potential was determined to be -373 +/- 6 mV, at pH 8. 5. XylT was unusually unstable for a [2Fe-2S] ferredoxin, with half-lives of 69 min at 25 degrees C in air and 70 min at 37 degrees C in argon. With photochemically reduced 5-deazaflavin for the controlled generation of reductant, it was demonstrated that XylT mediates the rapid reactivation of purified inactive catechol 2,3-dioxygenase in vitro. Inactivation of XylE by 4-methylcatechol resulted in oxidation of the active site iron to a high spin ferric state that was detectable by EPR. Spectroscopic evidence presented here demonstrates that XylT reactivates XylE through reduction of the iron atom in the active site of the enzyme. It is the first instance of a ferredoxin-mediated reactivation of an enzyme. The level of expression of XylT in Pseudomonas putida mt2 cells is low and the calculated XylT/XylE molar ratio is consistent with the proposal that XylE reactivation involves catalytic nonstoichiometric amounts of XylT.

Bacterial Proteins↗
PubMed2005

Catechol oxidase-like oxidation chemistry of the 1-20 and 1-16 fragments of Alzheimer's disease-related beta-amyloid peptide: their structure-activity correlation and the fate of hydrogen peroxide.

The Cu2+ complexes of the 1-16 and the 1-20 fragments of the Alzheimer's disease-related beta-amyloid peptide (CuAbeta) show significant oxidative activities toward a catechol-like substrate trihydroxylbenzene and plasmid DNA cleavage. The latter reflects possible oxidative stress to biological macromolecules, yielding supporting data to the pathological role of these soluble Abeta fragments. The former exhibits enzyme-like kinetics and is dependent on [H2O2], exhibiting k(cat) of 0.066 s-1 (6000-fold higher than the reaction without CuAbeta) and k(cat)/Km of 37.2 m-1s-1 under saturating [H2O2] of approximately 0.24%. This kinetic profile is consistent with metal-centered redox chemistry for the action of CuAbeta. A mechanism is proposed by the use of the catalytic cycle of dinuclear catechol oxidase as a working model. Trihydroxylbenzene is also oxidized by CuAbeta aerobically without H2O2, affording rate constants of 6.50x10(-3) s-1 and 3.25 m-1s-1. This activity is also consistent with catechol oxidase action in the absence of H2O2, wherein the substrate binds and reduces the Cu2+ center first, followed by O2 binding to afford the mu-eta2:eta2-peroxo intermediate, which oxidizes a second substrate to complete the catalytic cycle. A tetragonally distorted octahedral metal coordination sphere with three coordinated His side chains and some specific H-bonding interactions is concluded from the electronic spectrum of CuAbeta, hyperfine-shifted 1H NMR spectrum of CoAbeta, and molecular mechanics calculations. The results presented here are expected to add further insight into the chemistry of metallo-Abeta, which may assist better understanding of the neuropathology of Alzheimer's disease.

Alzheimer Disease↗
PubMed2005

Probing the beta2 adrenoceptor binding site with catechol reveals differences in binding and activation by agonists and partial agonists.

The beta(2) adrenergic receptor (beta(2)AR) is a prototypical family A G protein-coupled receptor (GPCR) and an excellent model system for studying the mechanism of GPCR activation. The beta(2)AR agonist binding site is well characterized, and there is a wealth of structurally related ligands with functionally diverse properties. In the present study, we use catechol (1,2-benzenediol, a structural component of catecholamine agonists) as a molecular probe to identify mechanistic differences between beta(2)AR activation by catecholamine agonists, such as isoproterenol, and by the structurally related non-catechol partial agonist salbutamol. Using biophysical and pharmacologic approaches, we show that the aromatic ring of salbutamol binds to a different site on the beta(2)AR than the aromatic ring of catecholamines. This difference is important in receptor activation as it has been hypothesized that the aromatic ring of catecholamines plays a role in triggering receptor activation through interactions with a conserved cluster of aromatic residues in the sixth transmembrane segment by a rotamer toggle switch mechanism. Our experiments indicate that the aromatic ring of salbutamol does not activate this mechanism either directly or indirectly. Moreover, the non-catechol ring of partial agonists does not interact optimally with serine residues in the fifth transmembrane helix that have been shown to play an important role in activation by catecholamines. These results demonstrate unexpected differences in binding and activation by structurally similar agonists and partial agonists. Moreover, they provide evidence that activation of a GPCR is a multistep process that can be dissected into its component parts using agonist fragments.

Albuterol↗
PubMed1976

The benzenediols: catechol, resorcinol and hydroquinone--a review of the industrial toxicology and current industrial exposure limits.

A review of the published industrial toxicology for the benzenediols, catechol, resorcinol and hydroquinone was made to evaluate their proposed or established occupational exposure levels. Acute animal toxicity data for catecholand resorcinol are presented, along with that for phenol because of its analogous signs of illness and intoxication. The comparative acute toxicity data for catechol and phenol are anomalous, but suggest a TLV for catechol similar to that of phenol. The comparative acute toxicity data for resorcinol and phenol clearly show that resorcinol is significantly less toxic than phenol which has a 5 ppm TLV. These data, along with production plant exposures as high as 9.6 ppm without reported effects, suggest an industrial exposure level (TLV) for resorcinol of at least 10 ppm, perhaps 20 ppm or higher. The established 2 mg/M3 TLV for hydroquinone appears to be proper.

Administration, Oral↗
PubMed1996

Characterization of the rat catechol-O-methyltransferase gene proximal promoter: identification of a nuclear protein-DNA interaction that contributes to the tissue-specific regulation.

The methylating enzyme catechol-O-methyltransferase (COMT) is an important inactivator of substrates containing catechol-structure, such as catechol neurotransmitters and hormones. In previous studies, the rat COMT gene has been cloned and characterized, and it has been shown that the two COMT polypeptides, S- and MB-COMT, are expressed from one gene by cooperation of two separate promoters. One promoter, P2, functions constitutively, whereas the other, the proximal P1 promoter, is regulated in a tissue-specific manner. In this report, a more detailed analysis of the rat P1 promoter is presented. By using reporter gene constructs, it is shown that upstream sequences of the P1 promoter contain several regions that modulate the expression either positively or negatively. These experiments also show that the region between the MB- and S-ATG translation initiation codons is indispensable for the activity of this promoter. Analysis of this region by DNase I footprinting and gel retardation assays identified the presence of several DNA elements with SP1 and NF1 recognition site homologies that bound both liver and brain nuclear proteins. However, one 11-nucleotide-long DNA region containing an overlapping consensus binding sequence for CREB and C/EBP-like factors reacted only with the liver nuclear lysate. Supershift experiments suggest that the transcription factor C/EBPalpha mediates the tissue-specific expression of the rat COMT P1 promoter.

Animals↗
PubMed1993

Carcinogenicity of catechol in F344 rats and B6C3F1 mice.

Carcinogenicity of catechol, a naturally occurring and industrial chemical which has been shown to have strong cell proliferating potential on rat glandular stomach epithelium, was investigated in male and female F344 rats and B6C3F1 mice. Groups of 30 male and female F344 rats and B6C3F1 mice were treated with 0.8% catechol in powdered diet continuously for 104 weeks (rats) or 96 weeks (mice). At necropsy, neoplastic lesions were observed mainly in the glandular stomach of both species. Adenomas were found in all rats and in the majority of mice: 29 out of 30 (97%) in males and 21 out of 29 (72%) females. In addition 15 out of 28 (54%) and 12 out of 28 (43%) of the male and female rats respectively, had well differentiated adenocarcinomas. No adenocarcinomas were found in mice of either sex. In the forestomach epithelium, although significant increase in papilloma development was not evident, incidences of squamous cell hyperplasia were significantly increased in rats and mice of both sexes. In other organs examined, incidence and numbers of liver hyperplastic foci per cm2 liver section were significantly lower in male rats. Although the incidence was not different, the numbers of hyperplastic foci were also significantly reduced in female rats. Thus the present experiment clearly demonstrated that catechol exerts carcinogenic activity in rodent glandular stomach epithelium.

Adenocarcinoma↗
PubMed1998

Induction of nuclear catechol-O-methyltransferase by estrogens in hamster kidney: implications for estrogen-induced renal cancer.

Catecholestrogens are postulated to contribute to carcinogenesis by causing DNA damage mediated by reactive oxygen species generated during redox cycling between catechol and quinone estrogens, and by quinone estrogens that can form depurinating adducts. The above hypothesis is based principally on studies of the cancers that develop in renal cortex of hamsters treated with primary estrogens: Hamster kidney can catalyze 2- and 4-hydroxylation of estrogens and support their redox cycling, and the kidneys of estradiol-treated hamsters show evidence of oxidative cellular and DNA damage. Here we used immunocytochemisty to test the postulate that catechol-O-methyltransferase (COMT), the enzyme that can prevent oxidation of catecholestrogens to their quinone derivatives, would be induced in renal cortex of hamsters treated with estradiol or ethinyl estradiol. In kidneys of control hamsters, COMT was localized in cytoplasm of epithelial cells of proximal convoluted tubules, predominantly in the juxtamedullary region where the estrogen-induced cancers arise. After 2- or 4-weeks of treatment with either estrogen, COMT was seen in epithelial cells of proximal convoluted tubules throughout the cortex, and many cells also showed intense nuclear COMT immunoreactivity. Estradiol-induced renal cancers were negative for COMT, but were surrounded by tubules with intense cytoplasmic and nuclear immunostaining. The nucleus-associated COMT was shown by immunoblot analysis to be the soluble form of the enzyme. Using reverse transcription-polymerase chain reaction amplification, hamster kidney COMT was shown to lack the putative nuclear localization signal sequence present in human COMT. A second phase II enzyme, CuZn-superoxide dismutase (CuZnSOD), was shown by immunocytochemistry to remain extranuclear in proximal convoluted tubules of estrogen-treated hamsters, which indicates entry of COMT into the nucleus to be selective. The findings are consistent with the catechol/quinone estrogen hypothesis of estrogen-induced cancer, while the translocation of the enzyme to the nucleus following estrogen treatment suggests a response to a threat to the genome by electrophilic products of catechols.

Amino Acid Sequence↗
PubMed2005

Association of the functional catechol-O-methyltransferase VAL158MET polymorphism with the personality trait of extraversion.

Across different personality theories, there is agreement that dopamine is the neurochemical basis of extraversion. However, evidence from molecular genetics for the validity of this hypothesis is far from convincing. The functional polymorphism of the catechol-O-methyltransferase gene (COMT VAL158MET) has not been related to extraversion before, although it is a promising candidate gene locus for extraversion because of its great influence on the catabolism of dopamine. In a sample of n=363 healthy study participants, the catechol-O-methyltransferase VAL158MET polymorphism was related to extraversion and novelty seeking.Results showed a significant association between catechol-O-methyltransferase, extraversion and the subscale exploratory excitement (NS1) of novelty seeking but not with the total novelty-seeking scale supporting the psychometric analyses of the personality scales. The findings support the hypothesis that the dopamine system is involved in positive emotionality and incentive motivation, which has implications for the understanding of the neurochemical correlates of normal and psychopathological behaviors.

Adult↗
PubMed1996

Human catechol-O-methyltransferase pharmacogenetics: description of a functional polymorphism and its potential application to neuropsychiatric disorders.

Catechol-O-methyltransferase (COMT) inactivates catecholamines and catechol drugs such as L-DOPA. A common genetic polymorphism in humans is associated with a three-to-four-fold variation in COMT enzyme activity and is also associated with individual variation in COMT thermal instability. We now show that this is due to G-->A transition at codon 158 of the COMT gene that results in a valine to methionine substitution. The two alleles can be identified with a PCR-based restriction fragment length polymorphism analysis using the restriction enzyme Nla III. The identification of a gentic marker associated with significant alterations in enzyme activity will facilitate the analysis of a possible role for the COMT gene in neuropsychiatric conditions in which abnormalities in catecholamine neurotransmission are believed to occur, including mood disorders, schizophrenia, obsessive compulsive disorder, alcohol and substance abuse, and attention deficit hyperactivity disorder. In addition, this polymorphism may have pharmacogenetic significance in that it will help make it possible to identify patients who display altered metabolism of catechol drugs.

Catechol O-Methyltransferase↗
PubMed2001

Crystallization and preliminary crystallographic characterization of catechol-O-methyltransferase in complex with its cosubstrate and an inhibitor.

Catechol-O-methyltransferase (COMT) is involved in the metabolism of catecholamines, catechol steroids and xenobiotic catechols. A precise knowledge of the enzyme-inhibitor structural interactions could help in the design of better inhibitors. Soluble rat COMT was expressed in Escherichia coli and the recombinant protein was crystallized with a new tight-binding inhibitor, BIA 3-335 [1-(3,4-dihydroxy-5-nitrophenyl)-3-(n-3'-trifluoromethylphenyl)piperazine-1-propanone dihydrochloride]. The crystals were obtained by the sitting-drop vapour-diffusion method using PEG 6K as a precipitant. These crystals diffracted to better than 1.9 A and belong to the trigonal space group P3(2)21. The unit-cell parameters for the crystal measured at room temperature were a = b = 51.5, c = 168.3 A; each shrank by about 1 A on freezing.

Animals↗
PubMed1989

Inductions of ornithine decarboxylase and replicative DNA synthesis but not DNA single strand scission or unscheduled DNA synthesis in the pyloric mucosa of rat stomach by catechol.

The possible tumor-promoting and genotoxic activities of catechol were examined. Administration of catechol by gastric intubation at doses of 10 to 90 mg/kg body weight to male F344 rats induced up to 19-fold increase in ornithine decarboxylase activity with a maximum after 8 h and up to 8-fold increase in replicative DNA synthesis with a maximum after 24 h in the pyloric mucosa of the stomach. These results suggest that catechol has tumor-promoting activity in the pyloric mucosa of rat stomach. However, its administration at doses of 37.5 to 90 mg/kg body weight did not induce DNA single strand scission in the pyloric mucosa as determined by the alkaline elution method after 2 and 6 h or unscheduled DNA synthesis examined after 2 and 12 h.

Animals↗