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Influence of phenol on cultures of acetate-fed aerobic granular sludge.

AIMS: This paper attempts to investigate the inhibition of phenol on the acetate utilization in acetate-fed aerobic granular sludge culture. METHODS AND RESULTS: Acetate-fed aerobic granules with a mean diameter of 1.0 mm were predeveloped in a column sequencing aerobic sludge blanket reactor. The present study looked into the utilization kinetics of acetate by acetate-fed aerobic granules in the presence of different phenol concentrations ranging from 0 mg l(-1) to 50 mg l(-1). For this purpose, batch experiments were conducted at 25 degrees C, while the initial biomass and acetate concentrations were in a range of 109-186 mg mixed liquor suspended solids (MLSS) l(-1) and 185-300 mg acetate-chemical oxygen demand (COD) l(-1). Results showed that the utilization of acetate in the presence of phenol was subject to a zero-order reaction kinetics. The relative phenol concentration in terms of the ratio of initial phenol concentration (C(p)) to initial biomass concentration (X(0)) was used to describe the real inhibitory strength of phenol imposed on acetate-fed aerobic granules. When the C(p)/X(0) ratio increased from 0 to 0.19 mg phenol mg(-1) MLSS, the zero-order reaction rate constant of acetate dropped from 1.15 mg l(-1) min(-1) to 0.38 mg l(-1) min(-1), and a similar trend was also observed in specific oxygen utilization rate. As compared to the control test without addition of phenol, the acetate-COD removal efficiency was reduced by nearly 50% at a C(p)/X(0) value of 0.19 mg phenol mg(-1) MLSS. It was found that biodegradation of phenol was negligible in acetate-fed aerobic granular sludge batch culture. CONCLUSIONS: It appears that phenol can seriously repress the utilization of acetate in the acetate-fed aerobic granular sludge batch cultures. A simple zero-order reaction model could adequately describe the utilization of acetate by acetate-fed aerobic granules in the presence of phenol. SIGNIFICANCE AND IMPACT OF THE STUDY: It is expected that this study would lead to a better understanding of the behaviour of acetate-fed aerobic granules in the presence of inhibitory organic compounds.

Acetates↗

The cellular mechanism of the antiandrogenic action of nomegestrol acetate, a new 19-nor progestagen, on the rat prostate.

Nomegestrol acetate, like other synthetic progestins such as medroxyprogesterone acetate (MPA), chlormadinone acetate, megestrol acetate and cyproterone acetate, is able to modify the physiological actions of androgens. In the present study, the effects of nomegestrol acetate and other antiandrogens on the binding of androgen to the androgen receptor (AR) and on the 'activation' of this receptor were investigated, using rat ventral prostate as target model. Relative binding affinities (RBA) for AR were first estimated in vitro with respect to [3H]testosterone for a series of structurally-related compounds. The values obtained ranged as follows: dihydrotestosterone (DHT) much greater than megestrol acetate greater than or equal to testosterone (T) greater than nomegestrol acetate greater than 19-nor progesterone (19NP) greater than progesterone (P). An assay was established, using two different incubation times (3 h and 24 h) to further investigate relationships between binding affinity and androgenic, or antiandrogenic, activity. The following order (as %) was obtained for progestins as against [3H]mibolerone (DMNT): 1) DMNT (100) much greater than nomegestrol acetate (42) greater than megestrol acetate (29) greater than chlormadinone acetate (9) greater than MPA (8) greater than cyproterone acetate (6) after 3 h and 2) DMNT (100) much greater than MPA (53) much greater than nomegestrol acetate (19) greater than megestrol acetate (12) greater than chlormadinone acetate (14) and cyproterone acetate (8) after 24 h. Since the RBA of nomegestrol acetate declined with time, these results indicate that this substance may act like an antiandrogen rather than an androgen, while the contrary prevails concerning MPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgen Antagonists↗

NTP Toxicology and Carcinogenesis Studies of Benzyl Acetate (CAS No. 140-11-4) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Benzyl acetate, a water-white liquid with a pear-like odor, is a natural constituent of several essential oils and flower absolutes extracted from jasmine, hyacinth, gardenia, tuberose, ylang-ylang, cananga, and neroli. Commercial benzyl acetate, a liquid prepared synthetically from benzyl chloride, acetic acid, and triethylamine is used primarily as a component of perfumes for soaps and as a flavoring ingredient. This compound is practically insoluble in water but is miscible in alcohol and ether and soluble in benzene and chloroform. Toxicology and carcinogenesis studies of benzyl acetate (>99% pure) were conducted by administering benzyl acetate in corn oil gavage to groups of 50 male and 50 female F344/N rats at doses of 0, 250, or 500 mg/kg body weight and to groups of 50 male and 50 female B6C3F1 mice at doses of 0, 500, or 1,000 mg/kg once daily five days per week for 103 weeks. Dose selection for the 2-year study was based on mean body weight gain depression and decreased survival observed at higher doses in 13 week studies. The absence of any observable adverse effect of benzyl acetate on the survival or mean body weight gains of the rats or mice in the 2-year studies suggests that both the rats and the mice of each sex could have tolerated higher doses. An infection in the genital tract was probably responsible for the deaths of 26/35 control, 14/32 low-dose, and 8/20 high-dose female mice before the end of the study. Acinar-cell adenomas in the pancreas of male rats occurred with a positive trend (P<0.01), and the incidence in the high-dose group (37/49, 76%) was significantly (P<0.01) higher than in the vehicle controls (22/50, 40%). The incidence of these tumors in the low-dose group (27/50, 54%) was comparable to that in the gavage controls. Acinar-cell hyperplasia of the pancreas was observed in 37/50 control, 34/50 low-dose, and 36/49 high-dose male rats. No acinar-cell hyperplasia or adenoma of the pancreas was observed in female rats. The incidence of retinopathy and cataracts in the high-dose male rats was increased compared with the controls (retinopathy: 1/50; 0/50; 20/50; cataracts: 0/50; 0/50; 13/50). Low-dose female rats had an increased incidence of retinopathy (18/50). Retinopathy and cataracts in rats have been associated with proximity to fluorescent light in this and previous studies. Preputial gland neoplasms occurred with a positive trend (P<0.05) in male rats (cystadenocarcinoma: 0/50; 0/50; 3/50; all adenocarcinoma: 0/50; 1/50; 4/50; adenocarcinoma or carcinoma combined: 1/50; 1/50; 6/50). However, the incidence of all preputial gland tumors was not significantly elevated (2/50; 1/50; 6/50). For female rats the incidence of clitoral gland neoplasms was marginally increased (2/50; 0/50; 5/50). Hepatocellular adenomas occurred in mice of each sex with statistically positive trends (males: 0/50; 5/49; 13/50; females: 0/50; 0/50; 6/50), and the incidences in the high-dose groups were greater than those in the controls (males: P<0.001; females: P<0.05). Hepatocellular carcinomas were marginally elevated in dosed male and high-dose female mice (males: 10/50; 14/49; 12/50; females: 1/50; 0/50; 4/50). Squamous cell papillomas or carcinomas of the forestomach (uncommon neoplasms) occurred with a positive trend (P<0.05) in male mice (4/49; 4/48; 11/49). The incidence of these tumors was also marginally (P=0.054) increased in the high-dose female mice (0/50; 0/50; 4/48). The incidences of these tumors in both the high-dose male and the high-dose female mice were considerably higher than the historical corn oil gavage control rates at this laboratory (males, 2/296, 0.7%; females, 2/297, 0.7%) and throughout the program (males, 14/1,070, 1.3%; females, 3/1,073, 0.3%). Forestomach hyperplasia occurred at increased incidences in dosed mice of either sex (males: 1/49, 7/48, 22/49; females: 1/50, 6/50, 17/48). The neoplasms and hyperplasia of the forestomach were probably related to administration of benzyl acetate. In a separate metabolism study, benzyl acetate was absorbed from the gastrointestinal traolism study, benzyl acetate was absorbed from the gastrointestinal tract of rats and mice, with approximately 90&percnt; of the administered dose recovered as various metabolites in the urine within 24 hr. The primary metabolite was hippuric acid, with minor amounts of a mercapturic acid, and one or more unidentified metabolites. This capacity for absorption, metabolism, and disposition was unaffected by the amount or number of doses administered. Benzyl acetate was not mutagenic in strains TA100, TA98, TA135, or TA137 of Salmonella typhimurium in the presence or absence of Aroclor 1254-induced Sprague-Dawley rat or Syrian hamster S9 when tested according to the preincubation protocol. Benzyl acetate did not induce sister-chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells in the presence or absence of Aroclor 1254-induced Sprague-Dawley rat liver S9. Benzyl acetate was mutagenic in the mouse lymphoma L5178Y/TK&plusmn; assay in the presence, but not in the absence, of Aroclor 1254-induced Fisher 344 rat liver S9. An audit was conducted on the experimental data and the draft technical report for these 2-year studies on benzyl acetate. Based on the results of this audit additional pathology examinations were conducted on all target organs in male rats and male and female mice. The Technical Report reflects these final pathology evaluations. The overall conclusions regarding the toxicology and carcinogenicity of benzyl acetate did not change as a result of this evaluation. Under the conditions of these gavage studies, benzyl acetate increased the incidence of acinar-cell adenomas of the exocrine pancreas in male F344/N rats; the gavage vehicle may have been a contributing factor. There was no evidence of carcinogenicity for female F344/N rats. For male and female B6C3F1 mice there was some evidence of carcinogenicity in that benzyl acetate caused increased incidences of hepatocellular adenomas and squamous cell neoplasms of the forestomach. Synonyms: alpha-acetoxytoluene; benzyl ethanoate; acetic acid, benzyl ester

Journal Article↗

Differential toxic effects of lactate and acetate on the metabolism of Streptococcus mutans and Streptococcus sanguis.

Experiments were conducted with Streptococcus mutans NCTC 10449 and Streptococcus sanguis ATCC 10556 to determine whether the acid end-products, lactate and acetate, were involved in the regulation of cellular growth and metabolism. The growth rate and culture biomass of both organisms was inhibited by the addition of lactate and acetate at concentrations as high as 200 mM to the cultures, although the final pH values of the lactate and acetate cultures were similar. In addition, the metabolic conversion of glucose to lactate was decreased by external lactate but stimulated by acetate. In spite of this, calculation of the yield of cell biomass per mole of ATP (YATP) showed that the yield of both organisms actually increased in the presence of added lactate, but decreased with acetate. This indicates that the two acids interacted with the cells of the organisms by different mechanisms. For both organisms, the final external undissociated lactic acid was relatively constant at concentrations between 0 and 200 mM added lactate, 24.9-32.5 mM for S. mutans and 8.0-11.5 mM for S. sanguis. On the other hand, the final concentration of undissociated acetic acid in the S. mutans cultures increased from 2.9 to 83.7 mM as the medium acetate concentration increased, and from 1.0 to 36.0 mM with the S. sanguis cultures. Counterflow experiments provided evidence for a lactate carrier in both S. mutans and S. sanguis, but an acetate carrier in these organisms could not be demonstrated. [14C]-lactate and [14C]-acetate were taken up into de-energized, chemostatgrown cells of S. mutans and S. sanguis in response to an artificially generated pH gradient but not by an imposed electrical gradient. Thus, under these conditions lactate uptake occurred via a symport process with only one proton. Growth of both organisms in the presence of increasing concentrations of acetate resulted in a small reduction (27%) in the transmembrane pH gradient (delta pH) as measured by the permeant acid, [14C]-salicylate. However, the uptake of [14C]-acetate for the estimation of delta pH revealed significant inhibition of the acetate concentration gradient in the presence external acetate, indicating that the cells expelled the acetate anion. The results indicate that, unlike acetate uptake, lactate transport by S. mutans and S. sanguis was strictly regulated via the lactate carrier in order to prevent excessive dissipation of the pH gradient. Clearly, the formation of acetate by oral streptococci is more problematic for cellular homeostasis than the formation of lactate.

Acetic Acid↗

Nutritive value of acetate in growing pigs.

Twelve crossbred barrows from four litters (average initial body weight of 21 kg) were used to examine the nutritive value of acetate in growing pigs. The treatments were the addition of acetate in the form of triacetin to the basal diet at 0, 5 and 10% of the metabolizable energy (ME) intake. Metabolism tests were conducted during wk 1 and 4 on acetate. The responses of weight gain and N retention to increasing levels of acetate were linear (P less than .001). Efficiency of acetate utilization for body weight gain was .90 g/g acetate, and the mean N-sparing effect of acetate was 32.9 mg N/g acetate. In the liver, heart and femoral muscle examined from d 36 to 47 on acetate, there was a linear increase in RNA content (P less than .05) and in protein content (P less than .01), as the level of acetate intake was increased. Digestible energy and N-corrected ME (MEn) of acetate found in the first week on acetate were not different from its heat of combustion. Those found in the fourth week on acetate, however, were larger (P less than .05) than the heat of combustion. It was considered that a nutritional adaptation to acetate utilization, or a synergistic action of acetate with other energy sources, occurred. The energetic efficiency of acetate utilization for growth was estimated to be 56 to 59%.

Acetates↗

Acetate binding at the photosystem II oxygen evolving complex: an S(2)-state multiline signal ESEEM study.

Previously, using acetate deuterated in the methyl hydrogen positions, we showed that acetate binds in close proximity to the Mn cluster/Y(.)(z) tyrosine dual spin complex in acetate-inhibited photosystem II (PSII) preparations exhibiting the "split" EPR signal arising from the S(2)-Y(.)(z) interaction [Force, D. A.; Randall, D. W.; Britt, R. D. Biochemistry 1997, 36, 12062-12070]. By using paramagnetic NO to quench the paramagnetism of Y(.)(z), we are able to observe the ESEEM spectrum of deuterated acetate interacting with only the Mn cluster. A good fit of the ESEEM data indicates two (2)H dipolar hyperfine couplings of 0.097 MHz and one of 0.190 MHz. Modeling of these dipolar interactions, using our "dangler" 3 + 1 model for the S(2)-state of the Mn cluster, reveals distances consistent with direct ligation of acetate to the Mn cluster. As acetate inhibition is competitive with the essential cofactor Cl(-), this suggests that Cl(-) ligates directly to the Mn cluster. The effect of acetate binding on the structure of the Mn cluster is investigated by comparing the Mn-histidine coupling in NO/acetate-treated PSII and untreated PSII using ESEEM. We find that the addition of acetate and NO does not affect the histidine ligation to the Mn cluster. We also investigate the ability of acetate to access Y(.)(z) in Mn-depleted PSII, a PSII preparation expected to be more solvent accessible than intact PSII. We detect no coupling between Y(.)(z) and acetate. We have previously shown that small alcohols such as methanol can ligate to the Mn cluster with ease, while larger alcohols such as 2-propanol, as well as DMSO, are excluded [Force, D. A.; Randall, D. W.; Lorigan, G. A.; Clemens, K. L.; Britt, R. D. J. Am. Chem. Soc. 1998, 120, 13321-13333]. We probe the effect of acetate binding on the ability of methanol and DMSO to bind to the Mn cluster. We find that methanol is able to bind to the Mn cluster in the presence of acetate. We detect no DMSO binding in the presence of acetate. Thus, acetate binding does not increase the affinity or accessibility for DMSO binding at the Mn cluster. We also explore the possibility that the acetate binding site is also a binding site for substrate water. By comparing the ratioed three-pulse ESEEM spectra of a control, untreated PSII sample in 50% D(2)O to an NO/acetate-treated PSII sample in 50% D(2)O, we find that the binding of acetate to the oxygen evolving complex of photosystem II displaces deuterons bound very closely to the Mn cluster.

Acetates↗

Acetate clearance rate as a potential index of the availability of glucogenic precursors in ruminants fed on roughage-based diets.

Three experiments were conducted to investigate interactions between acetate and glucose metabolism in sheep fed on roughage-based diets, and to establish whether the clearance rate of an intravenous acetate load would provide a valid index of the dietary acetate:glucogenic precursors ratio. In Expt 1 lambs were fed on a basal diet of wheat straw and supplemented with propionate and protein. Both supplements increased glucose irreversible loss rate (ILR) although not to the same degree. Acetate clearance rates were increased by protein and propionate supplementation and were positively related to glucose ILR irrespective of precursor. In Expt 2 the effects of an increased dietary load of acetate given with or without propionate were investigated. Glucose ILR did not respond to acetate supplementation, but was increased when propionate was fed in addition to acetate. This was reflected in an unchanged ability to clear an intravenous acetate load from the blood when acetate alone was added, but an increased acetate clearance rate when propionate was fed in addition to acetate. In Expt 3 the effects of supplementation with various propionate:acetate ratios were investigated. Acetate clearance was consistently increased by an increased propionate:acetate ratio. These results show that the metabolism of excess acetate is responsive to the dietary supply of glucose precursors, and provide support for the concept that additional glucose precursors are necessary for the efficient utilization of acetate when roughage diets low in protein are fed.

Acetates↗

Metabolites of lynestrenol acetate in the bile of rats after intravenous administration; a comparison with lynestrenol.

Some aspects of the metabolism of lynestrenol acetate, an orally active contraceptive compound, were studied in female rats. Lynestrenol acetate is stable in gastric and intestinal juice in vitro. After intravenous administration of lynestrenol acetate and lynestrenol with a -14C label in the nucleus approximately 40% of the administered radioactivity was excreted in the bile within 90 min. After administration of lynestrenol acetate labelled in the ester group, 6% of the radioactivity was found in the bile. This means that the greater part of the lynestrenol acetate had lost its acetate group during the process of metabolism. There was an important difference between the autoradiograms of the thin layer patterns of post-hydrolysis extracts after administration of [4-14C]lynestrenol acetate and those after administration of [1'-14C]lynestrenol acetate and [4-14C]lynestrenol: the major metabolite of [4-14C]lynestrenol acetate did not appear on the autoradiograms of [1'--14C]lynestrenol acetate and [4-14C]lynestrenol. This indicates that lynestrenol acetate was altered in the nucleus in the presence of the acetate group. The acetate group itself was removed, either when the alterations took place, or after it had been completed. The results of IR, NMR and mass spectrometry analysis indicate the introduction of a 15alpha hydroxyl group. Results of gas-liquid chromatography and thin layer chromatography indicate that a second important metabolic is 19-nor-17alpha-pregn-20-yne-3alpha, 17beta-diol. The main conclusions are: 1. A part of the lynestrenol acetate is metabolized and excreted in the bile, the acetate group still being present. 2. Lynestrenol acetate is to some extent metabolized via another pathway than lynestrenol. This indicates that esterification of a steroid can lead to deviation from the metabolic pathway of the free original steroid.

Acetates↗

Cytotoxicity and DNA-protein crosslink formation in rat nasal tissues exposed to vinyl acetate are carboxylesterase-mediated.

Vinyl acetate is used in the paint, adhesive, and paper board industries. Vinyl acetate is a nasal carcinogen in rats exposed by inhalation for 2 years to 200 and 600 ppm, but not 50 ppm. Previous studies from our laboratory suggest that rat liver microsome-activated vinyl acetate induces plasmid DNA-histone crosslinks, in vitro, through esterase-mediated metabolism. Since nasal tissues contain high levels of carboxylesterase, tumorigenesis may be related to in situ production of the hydrolysis products acetaldehyde and acetic acid. Vinyl acetate was cytotoxic to both respiratory and olfactory tissues in vitro at 50-200 mM, but not 25 mM, after 2 hr exposure. Pretreatment of rats with the carboxylesterase inhibitor, bis-(p-nitrophenyl) phosphate (BNPP), attenuated the cytotoxic effects and metabolism of vinyl acetate in both tissue types. Semicarbazide, an aldehyde scavenger, was unable to protect the tissues from vinyl acetate-induced cytotoxicity. When the metabolites were tested, acetic acid, but not acetaldehyde, was cytotoxic to both tissues. The induction of DNA-protein crosslink (DPXL) formation by acetaldehyde and vinyl acetate in rat nasal epithelial tissues was detected using a sodium dodecyl sulfate/KCl precipitation technique. Endogenous crosslink levels ranged from 0.5 to 2.0% of total DNA and were considered background. Epithelial cells isolated from both olfactory and respiratory turbinates exhibited dose- and time-dependent increases in DPXL formation when exposed to 10-150 mM acetaldehyde for 1-2 hr at 37 degrees C. Similarly, respiratory and olfactory epithelial cells exposed to 5-75 mM vinyl acetate for 1-2 hr accumulated up to 12- and 15-fold higher crosslink levels than untreated cells, respectively. However, vinyl acetate appears to induce much higher levels of DPXLs at equimolar doses than acetaldehyde. This is thought to be related to stimulation of acetaldehyde-induced DPXL formation by the pH lowering effect of acetic acid production (via vinyl acetate hydrolysis). Pretreatment of the nasal turbinates with 1 mM BNPP reduced 25 mM vinyl acetate-induced DPXL formation by over 75% in both tissues. These data support a hypothesis that carboxylesterase-mediated hydrolysis of vinyl acetate is necessary to generate the active intracellular cross-linking agent, acetaldehyde, and the cytotoxic metabolite, acetic acid.

Acetaldehyde↗

Measurement of monosaccharides and conversion of glucose to acetate in anoxic rice field soil

Degradation of glucose has been implicated in acetate production in rice field soil, but the abundance of glucose, the temporal change of glucose turnover, and the relationship between glucose and acetate catabolism are not well understood. We therefore measured the pool sizes of glucose and acetate in rice field soil and investigated the turnover of [U-14C]glucose and [2-14C]acetate. Acetate accumulated up to about 2 mM during days 5 to 10 after flooding of the soil. Subsequently, methanogenesis started and the acetate concentration decreased to about 100 to 200 &mgr;M. Glucose always made up >50% of the total monosaccharides detected. Glucose concentrations decreased during the first 10 days from 90 &mgr;M initially to about 3 &mgr;M after 40 days of incubation. With the exception at day 0 when glucose consumption was slow, the glucose turnover time was in the range of minutes, while the acetate turnover time was in the range of hours. Anaerobic degradation of [U-14C]glucose released [14C]acetate and 14CO2 as the main products, with [14C]acetate being released faster than 14CO2. The products of [2-14C]acetate metabolism, on the other hand, were 14CO2 during the reduction phase of soil incubation (days 0 to 15) and 14CH4 during the methanogenic phase (after day 15). Except during the accumulation period of acetate (days 5 to 10), approximately 50 to 80% of the acetate consumed was produced from glucose catabolism. However, during the accumulation period of acetate, the rate of acetate production from glucose greatly exceeded that of acetate consumption. Under steady-state conditions, up to 67% of the CH4 was produced from acetate, of which up to 56% was produced from glucose degradation.

Journal Article↗

The ability of Escherichia coli O157:H7 to decrease its intracellular pH and resist the toxicity of acetic acid.

Batch cultures of Escherichia coli K-12 grew well in an anaerobic glucose medium at pH 5.9, but even small amounts of acetate (20 mM) inhibited growth and fermentation. E. coli O157:H7 was at least fourfold more resistant to acetate than K-12. Continuous cultures of E. coli K-12 (pH 5.9, dilution rate 0.085 h-1) did not wash out until the sodium acetate concentration in the input medium was 80 mM, whereas E. coli O157:H7 persisted until the sodium acetate concentration was 160 mM. E. coli K-12 cell accumulated as much as 500 mM acetate, but the intracellular acetate concentration of O157:H7 was never greater than 300 mM. Differences in acetate accumulation could be explained by intracellular pH and the transmembrane pH gradient (delta pH). E. coli K-12 maintained a more or less constant delta pH (intracellular pH 6.8), but E. coli O157:H7 let its delta pH decrease from 0.9 to 0.2 units as sodium acetate was added to the medium. Sodium acetate increased the rate of glucose consumption, but there was little evidence to support the idea that acetate was creating a futile cycle of protons. Increases in glucose consumption rate could be explained by increases in D-lactate production and decreases in ATP production. Intracellular acetate was initially lower than the amount predicted by delta pH, but intracellular acetate and delta pH were in equilibrium when the external acetate concentrations were high. Based on these results, the acetate tolerance of O157:H7 can be explained by fundamental differences in metabolism and intracellular pH regulation. By decreasing the intracellular pH and producing large amounts of D-lactate, O157:H7 is able to decrease delta pH and prevent toxic accumulations of intracellular acetate anion.

Acetic Acid↗

Degradation of vinyl acetate by soil, sewage, sludge, and the newly isolated aerobic bacterium V2.

Vinyl acetate is subject to microbial degradation in the environment and by pure cultures. It was hydrolyzed by samples of soil, sludge, and sewage at rates of up to 6.38 and 1 mmol/h per g (dry weight) under aerobic and anaerobic conditions, respectively. Four yeasts and thirteen bacteria that feed aerobically on vinyl acetate were isolated. The pathway of vinyl acetate degradation was studied in bacterium V2. Vinyl acetate was degraded to acetate as follows: vinyl acetate + NAD(P)+----2 acetate + NAD(P)H + H+. The acetate was then converted to acetyl coenzyme A and oxidized through the tricarboxylic acid cycle and the glyoxylate bypass. The key enzyme of the pathway is vinyl acetate esterase, which hydrolyzed the ester to acetate and vinyl alcohol. The latter isomerized spontaneously to acetaldehyde and was then converted to acetate. The acetaldehyde was disproportionated into ethanol and acetate. The enzymes involved in the metabolism of vinyl acetate were studied in extracts. Vinyl acetate esterase (Km = 6.13 mM) was also active with indoxyl acetate (Km = 0.98 mM), providing the basis for a convenient spectrophotometric test. Substrates of aldehyde dehydrogenase were formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde. The enzyme was equally active with NAD+ or NADP+. Alcohol dehydrogenase was active with ethanol (Km = 0.24 mM), 1-propanol (Km = 0.34 mM), and 1-butanol (Km = 0.16 mM) and was linked to NAD+. The molecular sizes of aldehyde dehydrogenase and alcohol dehydrogenase were 145 and 215 kilodaltons, respectively.

Acetates↗

Comparison of unitrophic and mixotrophic substrate metabolism by acetate-adapted strain of Methanosarcina barkeri.

We examined the unitrophic metabolism of acetate and methanol individually and the mixotrophic utilization of these compounds by using detailed (14)C-labeled tracer studies in a strain of Methanosarcina barkeri adapted to grow on acetate as the sole carbon and energy source. The substrate consumption rate and methane production rate were significantly lower on acetate alone than during the unitrophic or mixotrophic metabolism of methanol. Cell yields (in grams per mole of substrate) were identical during exponential growth on acetate and exponential growth on methanol. During unitrophic metabolism of acetate, the methyl moiety accounted for the majority of the CH(4) produced, but 14% of the CO(2) generated originated from the methyl moiety. This correlated with the concurrent reduction of equivalent amounts of the C-1 of acetate to CH(4). (14)CH(4) was also produced from added (14)CO(2), although to a lesser extent than from reduction of the C-1 of acetate. During mixotrophic metabolism, methanol and acetate were catabolized simultaneously. The rates of (14)CH(4) and (14)CO(2) generation from [2-(14)C]acetate were logarithmic and higher in mixotrophic than in unitrophic cultures at substrate concentrations of 50 mM. A comparison of the oxidoreductase activities in cell extracts of the acetate-adapted strain grown on acetate and of strain MS grown on methanol or on H(2) plus CO(2) indicated that the pyruvate, alpha-ketoglutarate, and isocitrate dehydrogenase activities remained constant, whereas the CO dehydrogenase activity was significantly higher (5,000 nmol/min per mg of protein) in the acetate-adapted strain. These results suggested that a significant intramolecular redox pathway is possible for the generation of CH(4) from acetate, that energy metabolism from acetate by M. barkeri is not catabolite repressed by methanol, and that the acetate-adapted strain is a metabolic mutant with derepressed CO dehydrogenase activity.

Acetates↗

Plasma acetate turnover and oxidation.

Plasma acetate turnover and oxidation were determined in 11 healthy subjects by the constant infusion of a trace amount of [1-14C]acetate for 6 h. The subjects ages ranged from 22 to 57 yr. There was a positive correlation (P less than 0.001) between plasma acetate concentration and turnover rate, and a negative correlation (P less than 0.001) between turnover and age. The plasma acetate concentration in the subjects 22--28 yr old was 0.17 vs. 0.13 mM (P less than 0.02) in subjects 40--57 yr old. The plasma acetate turnover rate was also greater in the younger age group (8.23 +/- 0.66 vs. 4.98 +/- 0.64 mumol/min . kg, P less than 0.01). Approximately 90% of the plasma acetate turnover was immediately oxidized to CO2 in both age groups, however, 13.2 +/- 0.89% of the CO2 output in the younger group was derived from plasma acetate oxidation compared to 7.9 +/- 0.94% in the older group (P less than 0.01). The mean plasma acetate concentration, turnover, and oxidation in six cancer patients 47--63 yr old were similar to the values observed in the age-matched healthy subjects. Uptake or output of acetate by various tissues was measured by arterial-venous plasma acetate concentration differences. In seven of eight subjects undergoing elective surgery, the arterial-portal venous concentration difference was negative, which indicated that the gastrointestinal tract can contribute to plasma acetate production. Uptake of plasma acetate by both the leg and liver appeared to be dictated by the arterial acetate concentration. Net production of acetate by both the leg and liver was most often observed at arterial plasma acetate concentrations less than 0.08 mM.

Acetates↗

Preferential labeling of glial and meningial brain tumors with [2-(14)C]acetate.

UNLABELLED: Acetate is preferentially transported into and metabolized by astrocytes, rather than synaptosomes or neurons, and labeled acetate is used as a glial reporter molecule to assess glial metabolism and glial-neuronal interactions. Because monocarboxylic acid transporter specificity might confer a phenotype to help localize, detect, and characterize brain tumors of glial origin, use of [2-(14)C]acetate and [(14)C]deoxyglucose (a glucose analog metabolized by all brain cells) was compared in rat and human brain tumors. METHODS: Cultured C6 glioma or U-373 glioblastoma/astrocytoma tumor cells were injected into the caudate nucleus of anesthetized CDF Fisher rats; 2--3 wk later, an intravenous pulse of [2-(14)C]acetate or [(14)C]deoxyglucose was given, and timed blood samples were drawn during the 5- or 45-min experiment, respectively. Local (14)C levels in the brain were assayed by quantitative autoradiography, and acetate uptake or glucose use was calculated. Uptake and metabolism of the [(14)C]acetate was also assayed in C6 glioma and human surgical tumor samples in vitro. RESULTS: [(14)C]Acetate uptake into rat brain C6 tumors was 9.9 +/- 2.1 mL/100 g/min, compared with 3.9 +/- 1.0 mL/100 g/min in contralateral tissue (n = 6; P < 0.001), and was much higher than that into other brain structures (e.g., 5:1 for white matter and 2:1 for cortical gray matter). Glucose use in C6 tumors was 111 +/- 34 micromol/100 g/min, versus 81 +/- 5 micromol/100 g/min in contralateral tissue (n = 6; P = 0.08); no left-right differences in glucose use or acetate uptake were seen in other brain structures. The tumor-to-contralateral-tissue ratio for acetate (2.3 +/- 0.3) exceeded that for deoxyglucose (1.4 +/- 0.5) (P < 0.05), indicating that acetate is a sensitive C6 glioma marker. [(14)C]Acetate uptake also demarcated a few 3-wk-old C6 tumors that had unlabeled necrotic cores. U-373 tumors were smaller than C6 tumors in rat brain and were detected equally well with [(14)C]acetate and [(14)C]deoxyglucose. In vitro uptake of [(14)C]acetate into human glioblastoma or meningioma tumors was higher than uptake into pituitary adenoma. Rat C6 and human tumors with high uptake metabolized acetate to acidic compounds and amino acids. CONCLUSION: Tumor imaging with radiolabeled acetate can help to localize and classify brain tumors. Transporter and metabolic substrate specificity are traits that can be exploited further for in vivo imaging of brain glial tumors.

Acetic Acid↗

[Biocompatibility of the acetate in the dialysis fluid].

PURPOSE: Dialytic vasculopathy is a major morbidity and mortality risk factor in patients undergoing chronic dialysis treatment. Among the pathogenetic factors some are related to the uremic condition, others are due to biocompatible reactions to dialytic materials. Endothelial cells (EC) are the target of the mediators released during bioincompatible reactions, and the related effects could be considered the initial event eliciting the vasculopathy pathogenesis. Among the others, we focused our attention on the role played in this process by the inducible isoform of nitric oxide (NO) synthase (iNOS). In previous studies we demonstrated that bioincompatible membranes, as well as acetate-containing dialysis buffers stimulate iNOS gene expression and activity in endothelial cells in culture. In this study, we planned to evaluate the potential role of a new dialysis buffer in which acetate has been substituted with HCl as a stabilizer. METHODS: ECs were incubated for 12 h at 37 degrees C with different dialysis buffers: acetate (Acet), standard bicarbonate (Bic), acetate-free buffer (AF) and HCl-bicarbonate (BicHCl). We evaluated in reverse transcriptase polymerase chain reaction (RT-PCR) the gene transcription for iNOS, the NOS activity (as the production of H3 citrulline from H3 arginine by ionic exchange chromatography), EC proliferative (H3 thymidine incorporation) and pro-apoptotic rate (TUNEL analysis) and the nuclear translocation of the transcriptional factor NF-kappaB (EMSA). RESULTS: Acetate, even in the low concentration present in Bic was able to induce a significant iNOS gene transcription (results expressed as relative units and referred to basal values: Acet 1.9 +/- 0.01 fold increase, p<0.01; Bic 1.45 +/- 0.03 p<0.05; BicHCl 1.24 +/- 0.01; AF 1.17 +/- 0.02) and translation. Acetate at concentrations both of 3 mmoL and 38 mmoL (present in the bicarbonate buffer) significantly increased the enzymatic NOS activity vs unconditioned ECs: Acet 3.46 +/- 0.3, p<0.0005; Bic 1.69 +/- 0.2, p<0.005; BicHCl 1.24 +/- 0.15; AF 1.17 +/- 0.05. The EC proliferative index was significantly depressed by acetate containing dialysis buffers (unconditioned ECs 100%, Acet 38 +/- 15%, p<0.01; Bic 65 +/- 6%, p<0.05; AF 87 +/- 8%; BicHCl 75 +/- 6%). The percentage of apoptotic ECs was significantly increased by buffers contain-ing Acet vs BicHCl and AF. Finally, acetate at the concentrations present in Acet and Bic activated and promoted the nuclear translocation of the transcriptional factor NF-kappaB in ECs (p<0.01 vs unconditioned cells). CONCLUSIONS: The acetate-free dialysis buffers have better biocompatibility and potentially down-modulate the flogistic and sclerotic processes responsible for dialytic vasculopathy.

Acetates↗

NTP Technical Report on the comparative toxicity studies of allyl acetate (CAS No. 591-87-7), allyl alcohol (CAS No. 107-18-6) and acrolein (CAS No. 107-02-8) administered by gavage to F344/N rats and B6C3F1 mice.

Allyl acetate, allyl alcohol, and acrolein are used in the manufacture of detergents, plastics, pharmaceuticals, and chemicals and as agricultural agents and food additives. Male and female F344/N rats and B6C3F(1) mice received allyl acetate, allyl alcohol, or acrolein by gavage for 14 weeks. Genetic toxicology studies were conducted in Salmonella typhimurium, Drosophila melanogaster, cultured Chinese hamster ovary cells, rat bone marrow erythrocytes, and mouse peripheral blood erythrocytes. Groups of 10 male and 10 female rats were administered 0, 6, 12, 25, 50, or 100 mg allyl acetate/kg body weight, 0, 1.5, 3, 6, 12, or 25 mg/kg allyl alcohol, or 0, 0.75, 1.25, 2.5, 5, or 10 mg/kg acrolein in 0.5% methylcellulose by gavage, 5 days per week for 14 weeks. Groups of 10 male and 10 female mice were administered 0, 8, 16, 32, 62.5, or 125 mg/kg allyl acetate, 0, 3, 6, 12, 25, or 50 mg/kg allyl alcohol, or 0, 1.25, 2.5, 5, 10, or 20 mg/kg acrolein in 0.5% methylcellulose by gavage, 5 days per week for 14 weeks. In the allyl acetate rat study, all males and females in the 100 mg/kg groups died or were killed moribund by day 8; there were no other deaths. In the allyl alcohol study, all rats survived to the end of the study except one 6 mg/kg female. In the acrolein rat study, eight males and eight females in the 10 mg/kg groups died by week 9 of the study. Two males in the 2.5 and 5 mg/kg groups and one or two females in the 1.25, 2.5, and 5 mg/kg groups also died early; two of these deaths were gavage accidents. In the allyl acetate mouse study, all males and females in the 125 mg/kg group died during the first week of the study. All other early deaths, except five 62.5 mg/kg males and one 32 mg/kg female, were gavage accidents. In the allyl alcohol mouse study, one 50 mg/kg female died due to a gavage accident; all other animals survived to the end of the study. In the acrolein mouse study, all males and females administered 20 mg/kg died during the first week of the study. All other early deaths, except one male and one female administered 10 mg/kg, were unrelated to chemical administration. The concentration of 3-hydroxypropyl mercapturic acid (3-HPM) in the urine of rats and mice was determined after the first dose of chemical and at the end of the 14-week study. At both time points, the concentrations of 3-HPM in the urine of animals that received allyl acetate or allyl alcohol increased linearly with dose. In animals dosed with acrolein, the concentrations of 3-HPM exhibited a nonlinear increase with dose at the first time point. At the end of the study, the concentration of 3-HPM in the urine of animals dosed with acrolein was linear with dose except at the highest concentration administered. Since urine volumes were not recorded during the urine collection, complete quantitation of these data was not possible. The final mean body weights and mean body weight gains of male rats administered 12 or 50 mg/kg allyl acetate and of male and female rats administered 10 mg/kg acrolein were significantly less than those of the vehicle controls. The mean body weight gain of male mice in the 50 mg/kg group in the allyl alcohol study was also less than that of the vehicle controls. Final mean body weights and mean body weight gains of dosed female rats and male and female mice in the allyl acetate studies, male and female rats and female mice in the allyl alcohol studies, and male and female mice in the acrolein studies were generally similar to those of the respective vehicle controls. Clinical findings related to allyl acetate administration included pallor, eye or nasal discharge, ruffled fur, lethargy, diarrhea, and thinness among rats in the 100 mg/kg groups and lethargy, abnormal breathing, thinness, and ruffled fur among mice that died early. In the acrolein study, clinical findings included abnormal breathing, eye or nasal discharge, ruffled fur, thinness, and lethargy in rats in the 10 mg/kg groups. The liver weights of male rats administered 25 mg/kg allyl alcohol, female rats administered 50 mg/kg allyl acetate or 5 or 10 mg/kg acrolein, and male mice administered 10 mg/kg acrolein were significantly greater than those of the vehicle controls. Female rats administered 10 mg/kg acrolein had significantly lower absolute and relative thymus weights than did the vehicle controls. Female rats administered 25 mg/kg allyl alcohol spent more time in diestrus and less time in metestrus than the vehicle controls. The estrous cycles of female mice dosed with 16 or 32 mg/kg allyl acetate were significantly longer than that of the vehicle controls. Gross lesions related to allyl acetate treatment were observed in the liver, forestomach, and thorax/abdomen of male and female rats in the 100 mg/kg groups. Microscopically, the incidences of forestomach squamous epithelial hyperplasia were significantly increased in male rats administered 12 mg/kg or greater, female rats administered 25 or 50 mg/kg, male mice administered 32 or 62.5 mg/kg, and female mice administered 16, 32, or 62.5 mg/kg. Forestomach necrosis, hemorrhage, and inflammation were present in most rats in the 100 mg/kg groups, and the incidence of hemorrhage in 125 mg/kg male mice was increased; male mice in the 62.5 and 125 mg/kg groups and 125 mg/kg female mice had significantly increased incidences of glandular stomach hemorrhage. Increased incidences of several liver lesions occurred in male or female rats administered 50 or 100 mg/kg, and to a lesser extent in 25 mg/kg rats, 62.5 mg/kg male mice, and 125 mg/kg male and female mice. Bone marrow hyperplasia, hemorrhage or depletion in the mediastinal, mandibular, and mesenteric lymph nodes, hemorrhage and necrosis of the thymus, and hematopoietic cell proliferation of the red pulp were also observed in 100 mg/kg rats. Increased incidences of necrosis in the mandibular and mesenteric lymph nodes, spleen, and thymus were observed in 62.5 and 125 mg/kg mice. Male and female rats administered 6 mg/kg allyl alcohol or greater and male and female mice administered 12 mg/kg allyl alcohol or greater had significantly increased incidences of squamous hyperplasia of the forestomach epithelium. Female rats in the 25 mg/kg group had significantly increased incidences of bile duct hyperplasia and periportal hepatocyte hypertrophy in the liver. Incidences of portal cytoplasmic vacuolization were significantly increased in 50 mg/kg male mice and female mice in the 25 and 50 mg/kg groups. Gross lesions related to acrolein treatment were observed in the forestomach and glandular stomach of male and female rats in the 10 mg/kg groups and 20 mg/kg female mice. Microscopically, the incidences of squamous hyperplasia of the forestomach epithelium were significantly increased in male rats in the 5 and 10 mg/kg groups, female rats administered 2.5 mg/kg or greater, and male and female mice administered 2.5, 5, or 10 mg/kg. Male and female rats in the 10 mg/kg groups and 20 mg/kg male and female mice had significantly increased incidences of glandular stomach hemorrhage. Female mice in the 20 mg/kg group also had significantly increased incidences of glandular stomach inflammation and epithelial necrosis. Allyl acetate was mutagenic in S. typhimurium strains TA100 and TA1535, in the absence of S9 activation. With S9, no mutagenicity was detected in these two strains; negative results were obtained in strains TA97 and TA98, with and without S9. Allyl alcohol was not mutagenic in four strains of S. typhimurium, with or without S9 metabolic activation. Acrolein, tested in a preincubation protocol, was weakly mutagenic in S. typhimurium strain TA100 in the presence of 10% induced rat liver S9. Equivocal results were obtained in strains TA100 and TA1535 with 10% induced hamster liver S9. Negative results were obtained with TA97, TA98, and TA1538 under all test conditions, and acrolein gave negative results in all four S. typhimurium strains tested for mutation induction under a vapor protocol. No induction of micronuclei was noted in bone marrow erythrocytes of male rats administered allyl acetate by gavage three times at 24-hour intervals. No significant increases in micronucleated erythrocytes were noted in bone marrow samples from male rats administered allyl alcohol by intraperitoneal injection for 3 days. A small, but significant increase in the frequency of micronucleated normochromatic erythrocytes was observed in the peripheral blood of female mice administered allyl acetate by gavage for 14 weeks; no increase was observed in male mice. No increases in the frequencies of micronucleated normochromatic erythrocytes were observed in the peripheral blood of male or female mice administered allyl alcohol or acrolein by gavage for 14 weeks. Acrolein induced sister chromatid exchanges in cultured Chinese hamster ovary cells in the absence, but not the presence, of S9; it did not induce chromosomal aberrations, with or without S9. Results of three independent Drosophila melanogaster sex linked recessive lethal tests in which acrolein was administered to adult flies via feeding or injection and to larvae via feeding were negative.

Acetates↗

Lipid extraction and iontophoretic transport of leuprolide acetate through porcine epidermis.

The purpose of this study was to explore the effect of lipid extraction by the simple alkyl acetates of increasing carbon chain lengths (e.g. methyl, ethyl, propyl, butyl, pentyl, hexyl, and octyl acetates) and iontophoresis on the in-vitro transport of leuprolide acetate through porcine epidermis. The extent of lipid extraction from the stratum corneum (SC) by alkyl acetates was studied by Fourier transform infrared (FT-IR) spectroscopy. Ethyl, propyl, pentyl, hexyl, and octyl acetates significantly increased (P < 0.05) the permeability of leuprolide acetate through the epidermis in comparison to the control (epidermis without alkyl acetate treatment). Iontophoresis further increased (P < 0.05) the permeability of leuprolide acetate for all the alkyl acetates studied, when compared to their corresponding passive permeability. Ethyl acetate produced the maximum passive (13.47 microg/cm(2)/h) and iontophoretic (89.79 microg/cm(2)/h) flux among all the alkyl acetates studied. The SC treated with alkyl acetates showed a decrease in peak heights and areas of asymmetric and symmetric C--H stretching absorbances in comparison to untreated SC. A greater percentage decrease in peak heights and areas was obtained by ethyl acetate. Chloroform:methanol(2:1) [C:M(2:1)] was used as a positive control for lipid extraction. Our findings provide evidence that alkyl acetates cause lipid extraction, which leads to an enhancement in the passive and iontophoretic permeability of leuprolide acetate.

Animals↗