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PubMed2002

Study of Nd3+, Pd2+, Pt4+, and Fe3+ dopant effect on photoreactivity of TiO2 nanoparticles.

The metallorganic chemical vapor deposition method was successfully used to synthesize pure TiO(2) and Nd(3+)-, Pd(2+)-, Pt(4+)-, and Fe(3+)-doped TiO(2) nanoparticles. Polycrystalline TiO(2) structure was verified with x-ray diffraction, which showed typical characteristic anatase reflections without any separate dopant-related peaks. Transmission electron microscopy observations confirmed the existence of homogeneously distributed 22 +/- 3 nm TiO(2) nanoparticles. The particle size remained the same for the doped samples. The doping level of transition metals was kept at approximately 1 atomic percent, which was determined by x-ray photoelectron spectra and energy dispersive x-ray spectroscopy. The effects of different types of dopants on the photocatalytic activity were revealed by the degradation of 2-chlorophenols with an UV light source. The photocatalytic efficiency was remarkably enhanced by the introduction of Pd(2+) and Nd(3+). Nd(3+)-doped TiO(2) showed the largest enhancement. However, Pt(4+) changed the 2-chlorophenol degradation rate only slightly, and Fe(3+) was detrimental to this process. These effects were related to the position of the dopants in the nanoparticles and the difference in their ionic radii with respect to that of Ti(4+).

Journal Article↗
PubMed2001

Organic pollutants in surface waters from Portugal using chemometric interpretation.

Surface water samples from 45 sampling points across Portugal have been analyzed monthly by automated Solid Phase Extraction (SPE) and Gas Chromatography-Mass Spectrometry (GC/MS) in SIM and SCAN modes. Sampling was carried out during a period of six months (April-September, 1999), in order to determine the levels of contamination of 72 organic compounds mainly selected from the EC Council Directive list (CEC 76/464/EEC). Atrazine, simazine, deethylatrazine, alachlor, metolachlor, Irgarol, terbuthylazine, tributhylphosphate, 2,4,6-trichlorophenol, 2-chlorophenol, 3-chlorophenol, pentachlorophenol, dimethoate, lindane, linuron, propanil, o,p'-DDD, o,p'-DDT, o,p'-DDE and malathion were the main detected compounds. Although Irgarol, terbuthylazine, deethylatrazine and deisopropylatrazine are not listed in the EC Directive, these herbicides and transformation products are currently in use and they were also included in the monitoring program and detected at some sites. Fifty-nine percent of the samples were below 0.1 microg l(-1), the detection limit required the EEC Drinking Water Directive (DWD). Some compounds were detected at values higher than the DWD, e.g. atrazine (2.7 microg l(-1)) and alachlor (5.43 microg l(-1)) in April. Simazine was also present with a high value (2.3 microg l(-1)) in September. Tributhylphosphate (5.40 microg l(-1)) and 2,4,6-trichlorophenol (2.31 microg l(-1)) were also found at high concentrations near industrial sites. Chemometric interpretation of the more representative contaminants was performed by means of Principal Component Analysis, allowing the resolution of the more relevant contamination sources and the description of their temporal and spatial (geographical) distributions.

Environmental Monitoring↗
PubMed2006

Photocatalytic degradation of p-halophenols in TiO2 aqueous suspensions: halogen effect on removal rate, aromatic intermediates and toxicity variations.

The influence of the halogen upon the TiO(2) photocatalytic degradation of p-halophenols in water has been investigated. Phenol was used as the reference compound. Compared with its value for phenol, the apparent first-order rate constant of removal, k, was slightly but significantly higher for p-fluorophenol and p-chlorophenol, and slightly but significantly lower for p-bromophenol. For p-iodophenol, k was about half that of phenol. The relative values confirm that k is roughly correlated to the Hammett constant; this constant reflects the electron density on the aromatic ring and, accordingly, the reactivity towards electrophilic species generated by UV-irradiation of TiO(2). All compounds were found to be poorly adsorbed on TiO(2). Accordingly, k was not related to the differences observed in the very low adsorbed amounts. The detected aromatic intermediate products included hydroquinone (HQ), benzoquinone (BQ) and various halodihydroxybenzenes. HQ, BQ, 4-chloro-1,2 (and 1,3)-dihydroxybenzenes and 4-bromo-1,3-dihydroxybenzene were quantified. Mechanisms are tentatively suggested to interpret the differences in the degradation pathways of the p-halophenols. The organic intermediate products accounted for only a few percents of the total carbon during the degradation. The toxicity (1/EC50) measured by the Microtox test almost did not vary in the course of the degradation of phenol, p-chlorophenol and p-bromophenol until complete removal of these compounds. By contrast, the value of 1/EC50 was multiplied by ca. 2.5 when ca. 45% of p-iodophenol had been removed; concentrations of BQ higher than with the other p-halophenols are tentatively suggested to be at the origin of this increase. Interpretation of a surprising substantial increase in the 1/EC50 value when the removal of p-fluorophenol increased from 80 to 95% requires further investigation.

Adsorption↗
PubMedDate not supplied

Oxygen-enhanced biodegradation of phenoxy acids in ground water at contaminated sites.

The effects of adding oxygen to anaerobic aquifer materials on biodegradation of phenoxy acid herbicides were studied by laboratory experiments with aquifer material from two contaminated sites (a former agricultural machinery service and an old landfill). At both sites, the primary pollutants were phenoxy acids and related chlorophenols. It was found that addition of oxygen enhanced degradation of the six original phenoxy acids and six original chlorophenols. Inverse modeling on 14C 4-chloro-2-methylphenoxypropanoic acid (MCPP) degradation curves revealed that increasing the oxygen concentrations from <0.3 mg/L up to 7 to 8 mg/L shortened the lag phases (from approximately 150 d to 5 to 25 d) and increased first-order degradation rate constants by 1 order of magnitude (from approximately 5 x 10(-2) d(-1) to up to 30 x 10(-2) d(-1)). Additionally, the degree of MCPP mineralization was increased (30% to 50% mineralized at low oxygen concentrations and 50% to 70% mineralized at high oxygen concentrations, based on 14CO2 recovery). These positive effects on degradation were observed even at relatively low oxygen concentrations (2 mg/L). Furthermore, effects related to the addition of oxygen on the general geochemistry were studied. An oxygen consumption of 2.2 to 2.6 mg O2/g dw was observed due to oxidation of solid organic matter and, to some extent (0.5% to 11% of the total oxygen consumption), water-soluble compounds such as Fe2+, dissolved Mn, nonvolatile organic carbon, and NH4+. Overall, the results suggest that stimulated biodegradation by addition of oxygen might be a feasible remediation technology at herbicide-contaminated sites, although oxygen consumption by the sediment could limit the applicability.

Aerobiosis↗
PubMed1980

On the metabolism of clofibride, a hypolipaemic drug.

The absorption and metabolism of clofibride, a new hypolipaemic drug of p-chlorophenoxyisobutyric type, were investigated in the CD rat, the beagle and the olive baboon monkey. Clofibride is rapidly and massively resorbed and hydrolysed into 4-chlorophenoxyisobutyric acid (CPIB) and 4-hydroxy-N-dimethylbutyramide (HMB). CPIB, in free and glucuroconjugated form, and its metabolite, 4-chlorophenol, in the form of the glucuronate ether, are found in the serum of the rat. HMB is rapidly metabolized. The half-life of CPIB, the main active metabolite, in the serum is about 12 h in the rat, 43 +/- 9 h in the dog and 6 +/- 1 h in the baboon. In the rat, peak hypocholesterolaemic activity occurs late--24 h after administration of the drug and 20 h after peak concentration of CPIB in the blood. The half-life of 4-chlorophenol glucuronate ether in the serum is about 4 h whereas that of HMB is about 3 h. In the rat, the elimination of clofibride takes place mainly via the urine since 70% of the dose administered is found in the form of free or conjugated CPIB, 10% in the form of HMB or one of its metabolites, in 48 h samples of urine. Over the same period, faecal elimination accounts for no more than 2% of the dose ingested. In addition, in this species, the CPIB, 30% of which is secreted via the biliary route without being eliminated in the faeces, undergoes an enterohepatic circulation.

Administration, Oral↗
PubMed1993

Biodegradation and biotransformation of groundwater pollutant mixtures by Mycobacterium vaccae.

Mycobacterium vaccae can catabolize a number of major groundwater pollutants. When added singly, acetone, cyclohexane, styrene, benzene, ethylbenzene, propylbenzene, dioxane, and 1,2-dichloroethylene can be catabolized by M. vaccae. Catabolism of a number of these chemicals was monitored by gas-chromatographic analysis. Gas-chromatographic analysis indicated that the products of benzene degradation are phenol and hydroquinone. The products of chlorobenzene and ethylbenzene degradation are 4-chlorophenol and 4-ethylphenol. The extent that some compounds were catabolized when present as mixtures was also investigated. When toluene and benzene were present concomitantly, toluene was catabolized and benzene oxidation was delayed. Although toluene promoted the degradation of styrene, a lower rate of toluene degradation occurred when styrene was present. Both 4-chlorophenol and 4-ethylphenol had an antagonistic effect on the ability of M. vaccae to degrade other aromatic compounds. Studies with [14C]benzene indicated that M. vaccae can mineralize small amounts of this compound. These results suggest that components in mixtures may have a positive or a negative effect on the rates of biodegradation of other pollutants.

Acetone↗
PubMed1993

Microbial degradation of chlorinated acetophenones.

A defined mixed culture, consisting of an Arthrobacter sp. and a Micrococcus sp. and able to grow with 4-chloroacetophenone as a sole source of carbon and energy, was isolated. 4-Chlorophenyl acetate, 4-chlorophenol, and 4-chlorocatechol were identified as metabolites through comparison of retention times and UV spectra with those of standard substances. The proposed pathway was further confirmed by investigation of enzymes. The roles of the two collaborating strains were studied by growth experiments and on the level of enzymes. If transient accumulation of 4-chlorophenol was avoided either by the use of phenol-absorbing substances or by careful supplement of 4-chloroacetophenone, the Arthrobacter sp. was able to grow as a pure culture with 4-chloroacetophenone as a sole source of carbon and energy. Several mono-, di-, and trichlorinated acetophenones were mineralized by the Arthrobacter sp.

Acetophenones↗
PubMed1995

Degradation of Monochlorinated and Nonchlorinated Aromatic Compounds under Iron-Reducing Conditions.

The capacity for Fe(sup3+) to serve as an electron acceptor in the microbial degradation of monochlorinated and nonchlorinated aromatic compounds was investigated in anoxic sediment enrichments. The substrates tested included phenol, benzoate, aniline, their respective monochlorinated isomers, o-, m-, and p-cresol, and all six dimethylphenol isomers. Phenol and 2-, 3-, and 4-chlorophenol were utilized by anaerobic microorganisms, with the concomitant reduction of Fe(sup3+) to Fe(sup2+). The amount of Fe(sup2+) produced in the enrichments was 89 to 138% of that expected for the stoichiometric degradation of these substrates to CO(inf2), suggesting complete mineralization at the expense of Fe reduction. Under Fe-reducing conditions, there was initial loss of benzoate and 3-chlorobenzoate but not of 2- or 4-chlorobenzoate. In addition, there was initial microbial utilization of aniline but not of the chloroaniline isomers. There was also initial loss of o-, m-, and p-cresol in our enrichments. None of the dimethylphenol isomers, however, was degraded within 300 days. Furthermore, we tested the capacity of an Fe-reducing, benzoate-grown culture of Geobacter metallireducens GS-15 to utilize monochlorinated benzoates and phenols. G. metallireducens was able to degrade benzoate and phenol but none of their chlorinated isomers, suggesting that the degradation of chlorophenols in our sediment enrichments may be due to novel Fe-reducing organisms that have yet to be isolated.

Journal Article↗
PubMed1998

Spectrum of the reductive dehalogenation activity of desulfitobacterium frappieri PCP-1

Desulfitobacterium frappieri PCP-1 was induced for ortho- and para-dechlorinating activities by different chlorophenols. Dehalogenation rates ranging from 25 to 1,158 nmol/min/mg of cell protein were observed according to the chlorophenol tested and the position of the chlorine removed. D. frappieri shows a broad substrate specificity; in addition to tetrachloroethylene and pentachloropyridine, strain PCP-1 can dehalogenate at ortho, meta, and para positions a large variety of aromatic molecules with substituted hydroxyl or amino groups. Reactions of O demethylation and reduction of nitro to amino substituents on aromatic molecules were also observed.

Journal Article↗
PubMed1999

Thermal gradient gel electrophoresis analysis of bioprotection from pollutant shocks in the activated sludge microbial community.

We used a culture-independent approach, namely, thermal gradient gel electrophoresis (TGGE) analysis of ribosomal sequences amplified directly from community DNA, to determine changes in the structure of the microbial community following phenol shocks in the highly complex activated sludge ecosystem. Parallel experimental model sewage plants were given shock loads of chlorinated and methylated phenols and simultaneously were inoculated (i) with a genetically engineered microorganism (GEM) able to degrade the added substituted phenols or (ii) with the nonengineered parental strain. The sludge community DNA was extracted, and 16S rDNA was amplified and analyzed by TGGE. To allow quantitative analysis of TGGE banding patterns, they were normalized to an external standard. The samples were then compared with each other for similarity by using the coefficient of Dice. The Shannon index of diversity, H, was calculated for each sludge sample, which made it possible to determine changes in community diversity. We observed a breakdown in community structure following shock loads of phenols by a decrease in the Shannon index of diversity from 1.13 to 0.22 in the noninoculated system. Inoculation with the GEM (Pseudomonas sp. strain B13 SN45RE) effectively protected the microbial community, as indicated by the maintenance of a high diversity throughout the shock load experiment (H decreased from 1.03 to only 0.82). Inoculation with the nonengineered parental strain, Pseudomonas sp. strain B13, did not protect the microbial community from being severely disturbed; H decreased from 1.22 to 0.46 for a 3-chlorophenol-4-methylphenol shock and from 1.03 to 0.70 for a 4-chlorophenol-4-methylphenol shock. The catabolic trait present in the GEM allowed for bioprotection of the activated sludge community from breakdown caused by toxic shock loading. In-depth TGGE analysis with similarity and diversity algorithms proved to be a very sensitive tool to monitor changes in the structure of the activated sludge microbial community, ranging from subtle shifts during adaptation to laboratory conditions to complete collapse following pollutant shocks.

Bacteria↗
PubMed1999

Effect of aromatic compounds on cellular fatty acid composition of Rhodococcus opacus.

In cells of Rhodococcus opacus GM-14, GM-29, and 1CP, the contents of branched (10-methyl) fatty acids increased from 3% to 15 to 34% of the total fatty acids when the cells were grown on benzene, phenol, 4-chlorophenol, chlorobenzene, or toluene as the sole source of carbon and energy, in comparison with cells grown on fructose. In addition, the content of trans-hexadecenoic acid increased from 5% to 8 to 18% with phenol or chlorophenol as the carbon source. The 10-methyl branched fatty acid content of R. opacus GM-14 cells increased in a dose-related manner following exposure to phenol or toluene when toluene was not utilized as the growth substrate. The results suggest that 10-methyl branched fatty acids may participate in the adaptation of R. opacus to lipophilic aromatic compounds.

Journal Article↗
PubMed2001

Isolation and characterization of a novel As(V)-reducing bacterium: implications for arsenic mobilization and the genus Desulfitobacterium.

Dissimilatory arsenate-reducing bacteria have been implicated in the mobilization of arsenic from arsenic-enriched sediments. An As(V)-reducing bacterium, designated strain GBFH, was isolated from arsenic-contaminated sediments of Lake Coeur d'Alene, Idaho. Strain GBFH couples the oxidation of formate to the reduction of As(V) when formate is supplied as the sole carbon source and electron donor. Additionally, strain GBFH is capable of reducing As(V), Fe(III), Se(VI), Mn(IV) and a variety of oxidized sulfur species. 16S ribosomal DNA sequence comparisons reveal that strain GBFH is closely related to Desulfitobacterium hafniense DCB-2(T) and Desulfitobacterium frappieri PCP-1(T). Comparative physiology demonstrates that D. hafniense and D. frappieri, known for reductively dechlorinating chlorophenols, are also capable of toxic metal or metalloid respiration. DNA-DNA hybridization and comparative physiological studies suggest that D. hafniense, D. frappieri, and strain GBFH should be united into one species. The isolation of an Fe(III)- and As(V)-reducing bacterium from Lake Coeur d'Alene suggests a mechanism for arsenic mobilization in these contaminated sediments while the discovery of metal or metalloid respiration in the genus Desulfitobacterium has implications for environments cocontaminated with arsenious and chlorophenolic compounds.

Arsenates↗
PubMed2003

Characterization of the corrinoid iron-sulfur protein tetrachloroethene reductive dehalogenase of Dehalobacter restrictus.

The membrane-bound tetrachloroethene reductive dehalogenase (PCE-RDase) (PceA; EC 1.97.1.8), the terminal component of the respiratory chain of Dehalobacter restrictus, was purified 25-fold to apparent electrophoretic homogeneity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a single band with an apparent molecular mass of 60 +/- 1 kDa, whereas the native molecular mass was 71 +/- 8 kDa according to size exclusion chromatography in the presence of the detergent octyl-beta-D-glucopyranoside. The monomeric enzyme contained (per mol of the 60-kDa subunit) 1.0 +/- 0.1 mol of cobalamin, 0.6 +/- 0.02 mol of cobalt, 7.1 +/- 0.6 mol of iron, and 5.8 +/- 0.5 mol of acid-labile sulfur. Purified PceA catalyzed the reductive dechlorination of tetrachloroethene and trichloroethene to cis-1,2-dichloroethene with a specific activity of 250 +/- 12 nkat/mg of protein. In addition, several chloroethanes and tetrachloromethane caused methyl viologen oxidation in the presence of PceA. The K(m) values for tetrachloroethene, trichloroethene, and methyl viologen were 20.4 +/- 3.2, 23.7 +/- 5.2, and 47 +/- 10 micro M, respectively. The PceA exhibited the highest activity at pH 8.1 and was oxygen sensitive, with a half-life of activity of 280 min upon exposure to air. Based on the almost identical N-terminal amino acid sequences of PceA of Dehalobacter restrictus, Desulfitobacterium hafniense strain TCE1 (formerly Desulfitobacterium frappieri strain TCE1), and Desulfitobacterium hafniense strain PCE-S (formerly Desulfitobacterium frappieri strain PCE-S), the pceA genes of the first two organisms were cloned and sequenced. Together with the pceA genes of Desulfitobacterium hafniense strains PCE-S and Y51, the pceA genes of Desulfitobacterium hafniense strain TCE1 and Dehalobacter restrictus form a coherent group of reductive dehalogenases with almost 100% sequence identity. Also, the pceB genes, which may code for a membrane anchor protein of PceA, and the intergenic regions of Dehalobacter restrictus and the three desulfitobacteria had identical sequences. Whereas the cprB (chlorophenol reductive dehalogenase) genes of chlorophenol-dehalorespiring bacteria are always located upstream of cprA, all pceB genes known so far are located downstream of pceA. The possible consequences of this feature for the annotation of putative reductive dehalogenase genes are discussed, as are the sequence around the iron-sulfur cluster binding motifs and the type of iron-sulfur clusters of the reductive dehalogenases of Dehalobacter restrictus and Desulfitobacterium dehalogenans identified by electron paramagnetic resonance spectroscopy.

Bacteria, Anaerobic↗
PubMed2005

Desulfitobacterium hafniense is present in a high proportion within the biofilms of a high-performance pentachlorophenol-degrading, methanogenic fixed-film reactor.

We developed a pentachlorophenol (PCP)-degrading, methanogenic fixed-film reactor by using broken granular sludge from an upflow anaerobic sludge blanket reactor. This methanogenic consortium was acclimated with increasing concentrations of PCP. After 225 days of acclimation, the reactor was performing at a high level, with a PCP removal rate of 1,173 muM day(-1), a PCP removal efficiency of up to 99%, a degradation efficiency of approximately 60%, and 3-chlorophenol as the main chlorophenol residual intermediate. Analyses by PCR-denaturing gradient gel electrophoresis (DGGE) showed that Bacteria and Archaea in the reactor stabilized in the biofilms after 56 days of operation. Important modifications in the profiles of Bacteria between the original granular sludge and the reactor occurred, as less than one-third of the sludge DGGE bands were still present in the reactor. Fluorescence in situ hybridization experiments with probes for Archaea or Bacteria revealed that the biofilms were composed mostly of Bacteria, which accounted for 70% of the cells. With PCR species-specific primers, the presence of the halorespiring bacterium Desulfitobacterium hafniense in the biofilm was detected very early during the reactor acclimation period. D. hafniense cells were scattered in the biofilm and accounted for 19% of the community. These results suggest that the presence of PCP-dehalogenating D. hafniense in the biofilm was crucial for the performance of the reactor.

Anaerobiosis↗
PubMed2002

A new modified ortho cleavage pathway of 3-chlorocatechol degradation by Rhodococcus opacus 1CP: genetic and biochemical evidence.

The 4-chloro- and 2,4-dichlorophenol-degrading strain Rhodococcus opacus 1CP has previously been shown to acquire, during prolonged adaptation, the ability to mineralize 2-chlorophenol. In addition, homogeneous chlorocatechol 1,2-dioxygenase from 2-chlorophenol-grown biomass has shown relatively high activity towards 3-chlorocatechol. Based on sequences of the N terminus and tryptic peptides of this enzyme, degenerate PCR primers were now designed and used for cloning of the respective gene from genomic DNA of strain 1CP. A 9.5-kb fragment containing nine open reading frames was obtained on pROP1. Besides other genes, a gene cluster consisting of four chlorocatechol catabolic genes was identified. As judged by sequence similarity and correspondence of predicted N termini with those of purified enzymes, the open reading frames correspond to genes for a second chlorocatechol 1,2-dioxygenase (ClcA2), a second chloromuconate cycloisomerase (ClcB2), a second dienelactone hydrolase (ClcD2), and a muconolactone isomerase-related enzyme (ClcF). All enzymes of this new cluster are only distantly related to the known chlorocatechol enzymes and appear to represent new evolutionary lines of these activities. UV overlay spectra as well as high-pressure liquid chromatography analyses confirmed that 2-chloro-cis,cis-muconate is transformed by ClcB2 to 5-chloromuconolactone, which during turnover by ClcF gives cis-dienelactone as the sole product. cis-Dienelactone was further hydrolyzed by ClcD2 to maleylacetate. ClcF, despite its sequence similarity to muconolactone isomerases, no longer showed muconolactone-isomerizing activity and thus represents an enzyme dedicated to its new function as a 5-chloromuconolactone dehalogenase. Thus, during 3-chlorocatechol degradation by R. opacus 1CP, dechlorination is catalyzed by a muconolactone isomerase-related enzyme rather than by a specialized chloromuconate cycloisomerase.

4-Butyrolactone↗
PubMed1994

Cancer incidence and mortality among Swedish leather tanners.

OBJECTIVES: The aim was to study the incidence of cancer among Swedish leather tanners. METHODS: A cohort of 2026 subjects who had been employed for at least one year between 1900 and 1989 in three Swedish leather tanneries, was established. The cancer incidence and mortality patterns were assessed for the periods 1958-89 and 1952-89 respectively, and cause-specific standardised incidence and mortality ratios (SIRs and SMRs) were calculated. RESULTS: A significantly increased incidence of soft tissue sarcomas (SIR 4.27, 95% confidence interval (95% CI) 1.39-9.97) was found, based on five cases. Excesses, (not statistically significant) was also found for multiple myelomas (SIR 2.54, 95% CI 0.93-5.53), and sinonasal cancer (SIR 3.77, 95% CI 0.46-13.6). CONCLUSIONS: The increased incidence of soft tissue sarcomas adds support to previous findings of an excess mortality in this diagnosis among leather tanners. A plausible cause is exposure to chlorophenols, which had occurred in all three plants. The excess of multiple myelomas may also be associated with exposure to chlorophenol. The association between incidence of cancer and specific chemical exposure will be elucidated in a cohort-based case-referent study.

Cause of Death↗
PubMed2005

Changes in gut and Malpighian tubule transport during seasonal acclimatization and freezing in the gall fly Eurosta solidaginis.

Since few studies have examined cold tolerance at the organ level in insects, our primary objective was to characterize the functional responses of the gut and Malpighian tubules (MT) to seasonal acclimatization, chilling and freezing in larvae of the goldenrod gall fly Eurosta solidaginis Fitch (Diptera, Tephritidae). From September to December, hemolymph osmolality (455-926 mOsmol kg l(-1)) and freezing tolerance increased markedly in field-collected larvae. Chlorophenol Red was readily transported into the lumen of the foregut, the posterior portion of the midgut, the ureter, the proximal region of the anterior pair of MT, and entire posterior pair of MT. Ouabain and KCN inhibited transport of Chlorophenol Red in the gut and MT. Transport was readily detected at 0 degrees C and the rate of transport was directly related to temperature. The rate of fluid transport by the MT decreased steadily from a monthly high in September (10.7+/-0.8 nl min(-1) for the anterior pair; 12.7+/-1.0 nl min(-1) for the posterior pair) until secretion was no longer detectable in December; this decrease parallels entry into diapause for this species. Even in larvae that died following freezing for 40 days at -20 degrees C, individual organ function was retained to a limited extent. Through the autumn, cholesterol concentrations in the hemolymph increased nearly fourfold. In contrast, the ratio of cholesterol to protein content (nmol mg l(-1)) in the MT membrane remained relatively constant (22 approximately 24 nmol mg l(-1) protein) during this period. Freezing of larvae for 20 days at -20 degrees C caused a significant decrease in cholesterol levels in the hemolymph and the MT membranes compared to unfrozen controls. These results suggest that cholesterol plays a role in seasonal cold hardening and freeze tolerance in insects.

Acclimatization↗
PubMed2001

Relationship between effects of phenolic compounds on the generation of free radicals from lactoperoxidase-catalyzed oxidation of NAD(P)H or GSH and their DPPH scavenging ability.

The influence of various phenolic compounds on the lactoperoxidase (LPO)/hydrogen peroxide (H2O2)-catalyzed oxidation of biochemical reductants such as reduced beta-nicotinamide adenine dinucleotide (NADH), reduced beta-nicotinamide adenine dinucleotide phosphate (NADPH) or reduced glutathione (GSH) was investigated by electron spin resonance (ESR) spectroscopy. Micromolar quantities of phenolic compounds such as 17beta-estradiol, phenol, and p-chlorophenol enhanced the LPO/H2O2-catalyzed oxidation of NAD(P)H or GSH to generate a large amount of superoxide radical (O2*-) or glutathione thiyl radical (GS*), while, phenolic compounds such as quercetin and Trolox C greatly suppressed the generation of O2*- and GS*. In order to elucidate the effects of phenolic compounds on the generation of O2*- and GS*, their quenching activities for a stable radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH), were investigated by ESR spectroscopy. 17beta-Estradiol, phenol, and p-chlorophenol showed very weak scavenging activities for DPPH, but quercetin and Trolox C showed strong activities. This suggests that the ability of phenolic compounds to enhance LPO/H2O2-catalyzed oxidation of NAD(P)H or GSH relates inversely to their ability to quench DPPH. That is, phenolic compounds having weak quenching activity against DPPH may enhance the LPO/H2O2-catalyzed oxidation of NAD(P)H or GSH to generate a large amount of O2*- or GS*.

Bepridil↗