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PubMed2004

Efficacy of hydroquinone (2%) versus tretinoin (0.025%) as adjunct topical agents for chemical peeling in patients of melasma.

BACKGROUND AND OBJECTIVES: In recent years, chemical peels have become increasingly popular in the treatment of melasma. However, postpeel hyperpigmentation is a frequently encountered side effect, especially in dark-skinned individuals. The role of priming agents in preventing this complication has not been adequately evaluated. Hence, we studied the effect of hydroquinone versus tretinoin as priming agents in minimizing the incidence of this side effect in a double-blind, randomized clinical trial of 50 patients with melasma. METHODS: Of a total of 50 patients, 25 patients each with a similar skin phototype, the nature and severity of melasma were assigned to groups I and II. The patients were primed with 2% hydroquinone in group I, and in group II with 0.025% tretinoin once daily (night time) 2 weeks before starting trichloroacetic acid peels. Subsequently, all of them received trichloroacetic acid peels at intervals of 2 weeks for 12 weeks, followed by monthly peels for next 12 weeks during the follow-up period. Patients continued to use a sunscreen with an SPF of greater than 15 and the recommended priming agent during the follow-up. Final assessment was made at 6 months, based on the impression of the patient, clinical examination by the physician, and photographic analysis. RESULTS: A total of 50 patients (25 in each group) participated in the study. The predominant Fitzpatrick skin type observed among them was type IV (56%), and the type of melasma was mixed (44%). The final results at 12 weeks were comparable in two groups. However, a significant difference was seen in the two groups during the follow-up period, with continued improvement in 24% and worsening in 28% of patients in group I and continued improvement in only 16% and worsening in 40% in group II patients. CONCLUSIONS: Hydroquinone is superior to tretinoin as a priming agent in maintaining the results achieved with peels and in decreasing the incidence of postpeel reactive hyperpigmentation.

Administration, Topical↗
PubMed1975

Phosphorylation of ribosomal proteins in rat cerebral cortex in vitro.

Incubation of cerebral cortical tissue from immature rats in the presence of [32P]orthophosphate resulted in similar rates of incorporation of radioactivity into the proteins of free and membrane-bound ribosomes. Incorporation of label into ribosomal proteins of both species continued actively for at least 3 hours. Since recovery of membrane-bound ribosomes from rat cerebral cortex is quite low, further analyses of the radioactive phosphoproteins were restricted to the free ribosome population. A significant fraction of the radioactivity which was precipitated with trichloroacetic acid was not removed by heating in trichloroacetic acid at 90 degrees or extracted with organic solvents and therefore was presumed to be covalently bound to protein. The radioactive phosphoryl groups present in the ribosomal proteins were mainly in ester linkages since they were readily removed by exposure to 1 N NaOH, relatively unaltered by 1N HCl, and unaffected by hydroxylamine. This conclusion was supported by the isolation of labeled o-phosphoserine and o-phosphothreonine residues from hydrolysates of ribosomal proteins. A significant fraction of the labeled phosphoproteins in the purified ribosomes appeared to be bound tightly to the ribosome structure since only 40% of the radioactivity could be removed by extraction of these ribosomes with 1 M KCl. Phosphorylation of proteins of cerebral monoribosomes was more rapid than the same process in polyribosomes from the same source. Eight radioactive phosphoprotein bands could be detected by electrophoresis of proteins obtained from unfractionated cerebral ribosomes on unidimensional polyacrylamide gels containing sodium dodecyl sulfate. The protein nature of these materials was confirmed by pronase digestion. Proteins of subribosomal particles isolated from the total free ribosomal population were labeled differentially. When dissociation was carried out in the presence of EDTA, the small subunit contained four radioactive phosphoprotein bands, whereas the large subunit contained five. Three of the radioactive phosphoprotein components of the small subunit were removed when dissociation of cerebral ribosomes which were previously washed with high salt media was carried out in the presence of puromycin and high salt. However, only the largest labeled phosphoprotein band of the large subunit was removed by this procedure. This component exhibited the same electrophoretic mobility as one of the radioactive phosphoprotein bands which was removed from the small subunit by high salt treatment..

Animals↗
PubMed1985

Liquid-chromatographic measurement of riboflavin in serum and urine with isoriboflavin as internal standard.

We describe how riboflavin can be precisely and accurately measured in serum and urine. A structural analog, isoriboflavin, is used as an internal standard. Urine samples are prepared by adding the internal standard and trichloroacetic acid. For serum, proteins are denatured with trichloroacetic acid. A simple Sep-pak treatment of the supernate removes contaminating interferents. Within- and between-run precision is reflected by respective CVs of 2.2 and 4.9% for urine at 180 micrograms/L and 4.4 and 7.3% for serum at 10 micrograms/L. The standard curve is linear far beyond the concentrations encountered in serum and urine. The detection limit is estimated to be 10 micrograms/L and 1 microgram/L for urine and serum, respectively. The normal reference interval, as determined from 50 results for each matrix, is 36 to 349 micrograms/g of creatinine (mean 112 micrograms/g) for urine and 5.5 to 14.4 micrograms/L (mean 8.8 micrograms/L) for serum. Both distributions are skewed. The method is suited for routine use.

Adult↗
PubMed1996

N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine and 2,2,2-trichloroethanol: two novel metabolites of tetrachloroethene in humans after occupational exposure.

The excretion of tetrachloroethene metabolites in urine was studied in occupationally exposed workers to identify and quantify metabolites formed by glutathione conjugation and by cytochrome P450 oxidation of tetrachloroethene in humans. The glutathione conjugation pathway has been implicated in the chronic toxicity and possible tumorigenicity of tetrachloroethene to the kidney in rats. The biosynthesis of S-(1,2,2-trichlorovinyl)glutathione and N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine in humans had not been demonstrated. In this study, we investigated the biotransformation of tetrachloroethene in humans occupationally exposed during dry cleaning. Tetrachloroethene concentrations in the air of the dry cleaning shop were 50 +/- 4 ppm; two individuals were exposed for 8 hr daily and two individuals were exposed for 4 hr daily. In urine samples collected from the individuals at the beginning and at the end of the work week, N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine and 2,2,2-trichloroethanol as tetrachloroethene metabolites in humans were identified by GC/MS. The concentrations of N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine in the urine of the individuals were not significantly different at the start and at the end of the work week; however, concentrations of both N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine and 2,2,2-trichloro compounds (trichloroacetic acid and 2,2,2-trichloroethanol) as a marker for cytochrome P450-mediated metabolism were proportional to the length of daily tetrachloroethene exposure. A remarkable difference in the excretion pattern of 2,2,2-trichloro compounds, the major tetrachloroethene metabolites, was observed. Trichloroacetic acid and 2,2,2-trichloroethanol were present in the urine of two of the exposed individuals. Only 2,2,2-trichloroethanol was identified as a major urinary tetrachloroethene metabolite in two other individuals who did not excrete detectable amounts of trichloroacetic acid. The obtained results indicate that humans also have the ability to biosynthesize nephrotoxic glutathione S-conjugates from tetrachloroethene; however, when compared with rats, the human capacity for the biosynthesis of N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine seems to be lower.

Acetylcysteine↗
PubMed1981

Prostaglandin hydroperoxidase-mediated 2-amino-4-(5-nitro-2-furyl) [14C]thiazole metabolism and nucleic acid binding.

Prostaglandin hydroperoxide-mediated metabolism and binding of 2-amino-4-(5-nitro-2-furyl) [14C]thiazole ([14C]ANFT) metabolite to nucleic acids and proteins were investigated with rabbit bladder transitional epithelial and solubilized ram seminal vesicle microsomes. Metabolism was assessed by spectrophotometric and radiochemical techniques. Substrate and inhibitor studies are consistent with both metabolism and binding of [14C]ANFT occurring by the prostaglandin hydroperoxidase activity of prostaglandin endoperoxide synthetase. The ratio of the rates of [14C]ANFT product formation is approximately 3:7:10 (organic soluble:non-trichloroacetic acid precipitable: trichloroacetic acid precipitable) over a wide range of arachidonic acid concentrations. Approximately 2 and 1% of the total [14C]ANFT metabolized binds to transfer RNA and DNA, respectively. The metabolite isolated from the organic phase had a chromatographic profile and ultraviolet spectra different from authentic ANFT. If transfer RNA or DNA is added at the end of a 5-min incubation, no binding to nucleic acids was observed. The demonstration of prostaglandin hydroperoxidase-mediated covalent binding to nucleic acids is consistent with the involvement of this enzyme in 5-nitrofuran-induced bladder carcinogenesis.

Animals↗
PubMed1975

Ascorbate-synthesizing system in rat liver microsomes. II. A peptide-bound flavin as the prosthetic group of L-gulono-gamma-lactone oxidase.

L-Gulono-gamma-lactone oxidase [EC 1.1.3.8] was purified 80-fold from rat liver microsomes. In confirmation of our previous finding with a cruder preparation, the purified enzyme was shown to contain an L-gulono-gamma-lactone-reducible pigment as a prosthetic group. This pigment was not liberated from the protein by acid ammonium sulfate, 10% trichloroacetic acid or 2 M area, but was effectively released by proteolytic digestion. The pigment thus released showed a reduced-minus-oxidized difference spectrum characteristic of a flavin compound. The pigment was liberated from a trichloroacetic acid-treated preparation of the enzyme by pronase digestion and purified by Florisil column chromatography and paper chromatography. The absorption spectrum as well as the fluorescence emission and excitation spectra of the purified pigment indicated that it was actually a flavin peptide. It was, however, different not only from FMN but also from flavin peptides isolated from other sources such as succinate dehydrogenase [EC 1.3.99.1] and monoamine oxidase [EC 1.4.3.4] as regards the pH dependence of fluorescence intensity and the Rf value on thin-layer chromatography. A preliminary analysis showed that the purified flavin compound contained several amino acid residues. Alkaline photolysis of the purified flavin peptide suggested that the isoalloxazine ring of the flavin is involved in its binding to the peptide. The hypsochromic shift of the absorption peak in the near-ultraviolet region suggested further that the linkage between the flavin and the peptide may be mediated by the 8-methyl group of the isoalloxazine nucleus. It can be concluded that the prosthetic group of gulonolactone oxidase is a flavin which is covalently bound to the enzyme protein.

Alcohol Oxidoreductases↗
PubMed1981

In perfused rat hearts ischaemia promotes the reversible conversion of appreciable quantities of soluble adenine nucleotides to a stable trichloroacetic acid-precipitable form.

Radioactivity from [14C] adenosine was linearly incorporated into tissue nucleotides in perfused rat hearts. All the TCA-extractable 14C was confined to the purine nucleoside phosphates for up to 1 h of perfusion. Radioactivity was also incorporated linearly into the TCA-insoluble fraction, which by 40 min accounted for 24% of the tissue 14 C. Estimates based on precursor specific radioactivity suggest that at least 0.6 micro mol/g of the mononucleotide is in this stable insoluble form. Following 2 min total ischaemia, the tissue nucleotide content and soluble radioactivity decreased while the insoluble radioactivity showed a corresponding increase to account now for 35% of the tissue radiolabel. This redistribution was rapidly reversed by post-ischaemic reperfusion. A possible function for the rapid reversible sequestration of adenine nucleotides in ischaemia is proposed.

Adenine Nucleotides↗
PubMed1968

The nature of human serum insulin-like activity (ILA)P Characterization of ILA in serum and serum fractions obtained by acid-ethanol extraction and adsorption chromatography.

Studies were undertaken in an attempt to clarify the apparent heterogeneous nature of human serum insulin-like activity. Methods of preparative zone electrophoresis on Pevikon, acid-ethanol extraction of trichloroacetic acid serum protein precipitates, adsorption chromatography on DEAE-cellulose and Dowex 50, gel filtration chromatography, and insulin antiserum immunoreactivity were used. The results establish the presence of a substance in serum with in vitro biological properties similar to insuln but with different physicochemical properties. The major portion of serum ILA measured by bioassay techniques can be attributed to the effects of this substance. Whereas the in vitro biological effects of this substance on muscle and adipose cells were similar to those of crystalline insulin, the substance is distinguished from insulin by: (1) the failure of insulin antiserum to inhibit its in vitro biological effect; (2) a slower electrophoretic mobility (in the gamma-beta globulin zone); and (3) a larger molecular weight, between 40,000 and 50,000 in these studies. It is similar to insulin since both are soluble in acid-ethanol. The results further indicate that previously described insulin-like activity in gamma-beta globulin preparations, the major portion of total serum insulin activity described in acid-ethanol extracts of serum, "bound" insulin, "atypical" insulin, and antibody nonsuppressible insulin-like activity bioassayed in diluted serum are all one and the same substance.

Adipose Tissue↗
PubMed1988

[Methoxydextran as an indicator of gastrointestinal transit in Japanese quail].

The recovery of polyethylene glycol, a substance frequently used as an indicator of the dynamics in the liquid phase of intestinal chyme, is considerably influenced by the presence of trichloroacetic acid in certain applications. The suitability of (methoxy-14C)methoxydextrane as an intestinal indicator in the Japanese quail was tested in the study. After the administration of this indicator, the bird expires less than 1% of the substance in form of 14CO2. The recovery of labelled methoxydextrane is 98 +/- 7%. The distribution of the indicator within the segments of the gastrointestinal tract does not differ significantly from the distribution of (14C)polyethylene glycol 4000, measured in the absence of trichloroacetic acid. The transit of the labelled methoxydextrane into the jejunum did not reduce the radio-chemical purity of the isotope, as compared with its original purity before administration. A slight decrease was only recorded during the measurement of the cumulative excretion of the indicator for 72 hours, but this decrease has no influence upon the suitability of methoxydextrane as an intestinal indicator. (Methoxy-14C)methoxydextrane does not interact with trichloroacetic acid, whereas when polyethylene glycol is used as an indicator, the substance precipitates from the liquid phase just at the concentration commonly used for the removal of protein from biological samples.

Animals↗
PubMed1994

A biphasic radiometric assay of glycogenin using the hydrophobic acceptor n-dodecyl-beta-D-maltoside.

Glycogenin is a self-glycosylating protein that catalyzes early glucosyl transfer steps in the biosynthesis of glycogen. In currently used assays of glycogenin activity, the enzyme is incubated with radioactive UDP-glucose, and the labeled reaction product is then isolated by precipitation with trichloroacetic acid. A new assay is reported here which is based on the observation that glycogenin is not only self-glycosylating but may also use exogenous alkyl maltosides as substrates. After incubation of the enzyme with n-dodecyl-beta-D-maltoside and UDP-[3H]glucose, the radioactivity in the resultant n-dodecyl-beta-D-[3H]maltotrioside is determined by any one of the following three procedures, which all rely on the hydrophobic properties conferred on the reaction product by the alkyl aglycone: (i) adsorption of the product to a Sep-Pak C18 cartridge and elution with 70% ethanol; (ii) biphasic liquid scintillation counting in ScintiLene/25% isoamyl alcohol, without isolation of the product, and (iii) precipitation with trichloroacetic acid in the presence of carrier protein. The Sep-Pak C18 procedure has the advantage that it allows essentially quantitative isolation of the reaction product, while, under the conditions chosen, only about 50% of the product is precipitated by trichloroacetic acid. For most applications, however, biphasic liquid scintillation counting is the method of choice, since close to 90% of the labeled product is extracted into the organic phase and can be counted directly without interference from the labeled nucleotide sugar which remains in the aqueous phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Chemexfoliation--indications and cautions.

Chemexfoliation (chemical peeling) is being used to obtain both therapeutic (e.g., actinic keratoses) and cosmetic (e.g., removal of fine facial rhytides) benefits. Phenol, one of the most widely used agents for inducing cutaneous exfoliation, may induce cardiac arrhythmias and is toxic to the liver and kidneys. Trichloroacetic acid is not significantly absorbed and therefore does not produce systemic complications. Both phenol and trichloroacetic acid may produce hypertrophic scars and/or keloids and pigmentation irregularities, may accentuate preexisting abnormalities (e.g., telangiectasias, nevi, and pores), and may be associated with a flare of latent herpesvirus infection. Prolonged erythema of the treated areas and persistent rhytids have been reported with both agents.

Arrhythmias, Cardiac↗
PubMed1977

Transfer of ADP-ribose from NAD to choleragen: a subunit acts as catalyst and acceptor protein.

Choleragen selectively incorporates 3H from [3H]NAD labeled on the adenosine moiety and not 14C from [14C]NAD labeled on the nicotinamide moiety. This reaction does not require protein in addition to choleragen. Incorporation of isotope does not proceed at 4 degrees, requires dithiothreitol, is stable after extensive washing with cold trichloroacetic acid, and is decreased 80% by boiling in trichloroacetic acid. Studies with the A and B subunits of choleragen show that the A subunit catalyzes ADP-ribosylation and serves as an acceptor protein. The B subunit does not show catalytic or acceptor activity. We conclude that choleragen and its A subunit catalyze the hydrolysis of NAD and the enzymatic transfer of ADP-ribose to the A subunit.

Adenosine Diphosphate Sugars↗
PubMed1979

Regular arrangement of wall polymers in staphylococci.

Concentric circular structures were observed on the newly exposed surface of the wall of Staphylococcus epidermidis and on its isolated cross-wall. These structures were removed by treatment with trichloroacetic acid. Chemical analysis revealed that after treatment with trichloroacetic acid most of the wall phosphorus was extracted but more than half of the N-acetylglucosamine remained associated with the wall. These observations suggest that polysaccharides are likely to be arranged circularly on the surface of the wall.

Carbohydrate Conformation↗
PubMed1975

Immunochemistry of purified polysaccharide type antigens of group B streptococcal types Ia, Ib, and Ic.

The HCl-extracted purified polysaccharide type antigens of group B Streptococcus types Ia and Ib were composed of galactose and N-acetylglucosamine in a molar ratio of 3:1 for the Ia antigen and 2:1 for the Ib antigen. Immunochemical data were the same for the Ia antigens of type Ia, purified in this study, and type Ic, purified earlier. Glucosamine inhibited the Ib quantitative precipitin reactions more effectively than did N-acetylglucosamine, whereas the reverse was true of the Ia reaction. Ouchterlony studies were consistent with these observations and also revealed two type-specific precipitin bands with the HCl-extracted Ia antigens. All saline-extracted type antigens, however, formed single Ouchterlony bands that were only partially identical to the corresponding HCl antigens. Purification of the saline antigens was accomplished by treatment with cold trichloroacetic acid and by fractional ethanol precipitation. Immunoelectrophoresis experiments showed that the saline antigens were more negatively charged than the HCl antigens. The presence of sialic acid in the saline antigens probably accounted for their net negative charge and the fact that they were partially degraded by mild acid hydrolysis. The same serological specificities were observed with saline- and with HCl-extracted antigens.

Absorption↗
PubMed1997

The role of mouse intestinal microflora in the metabolism of trichloroethylene, an in vivo study.

1. Both trichloroethylene and its metabolite, dichloroacetic acid, produce liver tumors peroxisome proliferation and other adverse cellular alterations in rodents. 2. The hepatic mechanism by which dichloroacetic acid is formed is not conclusively demonstrated, but pharmacokinetic models have successfully associated its formation with trichloroacetic acid as immediate precursor. 3. Previous investigations have shown that dichloroacetic acid is formed from trichloroacetic acid by gut microflora isolated in vitro. 4. To determine the impact of gut microflora on dichloroacetic acid formation from a trichloroethylene dose in vivo, we developed a procedure which reduced gut microflora some 3 orders of magnitude below published levels. 5. The administration of trichloroethylene to control mice and to mice whose gut was practically sterile resulted in equivalent concentrations of dichloroacetic acid and other metabolites in blood and liver, but significantly different content of these metabolites in cecum contents. 6. These data indicate that gut microflora contribute minimally, if at all, to the formation of circulating dichloroacetic acid under these conditions.

Animals↗
PubMed1998

Partial characterization of the epitope on excretory-secretory products of Fasciola hepatica recognized by monoclonal antibody ES78.

This report contains a partial characterization of the epitope recognized by monoclonal antibody (MAb) ES78 produced against excretory-secretory (ES) antigens of Fasciola hepatica. ES78 is currently used for the detection of ES antigens in serum and stool samples of cattle and humans with fasciolosis, using a highly sensitive and specific sandwich enzyme-linked immunosorbent assay (ELISA). The epitope was characterized by periodate oxidation, alkaline borohydride reduction, trichloroacetic acid precipitation, beta-mercaptoethanol treatment, and enzymatic proteolysis. These results, together with those of the 2-site ELISA, lectin immunoassays, and beta-galactosidase digestion, showed that MAb ES78 reacts with a partly protein/partly carbohydrate antigenic determinant that is found on several ES molecules of adult specimens of F. hepatica and contains at least 1 disulfide bond and beta-galactose probably as galactose-beta(1-3)-N-acetylgalactosamine disaccharide.

Animals↗
PubMed1999

Measurement of muscle protein synthesis by positron emission tomography with L-[methyl-11C]methionine: effects of transamination and transmethylation.

BACKGROUND: Positron emission tomography with L-[methyl-11C]methionine provides a measure of regional protein synthesis rate (PSR) in skeletal muscle. However, the validity of the method depends on incorporation of methionine into protein with minimal transamination, transmethylation, or both. To test directly these assumptions, uptake of L-[methyl-14C]methionine in skeletal muscle was measured in control and cycloheximide-treated rats. METHODS: Normal and cycloheximide-treated rats (n = 8/group) were injected with 50 microCi of L-[methyl-14C]methionine and arterial blood sampled over 90 minutes. After killing, thigh muscle was homogenized, centrifuged, and treated with trichloroacetic acid. PSR from circulating methionine was estimated from trichloroacetic acid-precipitable radioactivity, arterial time-activity curves, and plasma methionine concentrations. RESULTS: In normal rats, approximately 70% of the tissue radioactivity was precipitated with trichloroacetic acid. In normal animals, PSR was 0.22 nmoles x min(-1) x g(-1), in excellent agreement with previous results. In the cycloheximide-treated group, PSR was 0.0032 nmoles x min(-1) x g(-1); approximately 98% reduction compared with controls. CONCLUSION: These studies support the hypothesis that L-[methyl-11(14C]methionine accumulates in skeletal muscle as 11(14)C-labeled protein.

Amination↗