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PubMed1997

Contact sensitization to sunscreens.

BACKGROUND: Para aminobenzoic acid (PABA) derivatives and cinnamate are chemical sunscreens that protect against UVB (290 to 320 nm). They may occasionally produce contact and photocontact sensitization. OBJECTIVE: To report a sensitization to octyl-dimethyl-PABA and photosensitization to 2-ethylhexyl-p-metossicinnamate in a 31-year-old man. METHODS: A patient with a 3-year history of a relapsing dermatitis involving the face, neck, legs, and knees is reported. The eruption had recurred every summer after sunlight exposure. Patch tests with International Contact Dermatitis Research Group (IC-DRG) standard series and the photopatch series (Hermal-Trolab, Reinbek, Germany) using Finn chambers on Scanpor (Norgesplaster A/S, Oslo, Norway) were carried out. RESULTS: We found a positive reaction to Balsam of Peru, fragrance mix, Escalol 507, and Parsol MCX (Hermal-Trolab, Reinbek, Germany). Photopatch test revealed a positive reaction only for Parsol MCX. CONCLUSION: The incidence of allergic contact dermatitis to sunscreens is considered low. Recently sunscreens patch test concentrations have been increased from 2% to 10%. These higher percentages will probably permit the identification of more cases of sunscreens allergy in the near future.

4-Aminobenzoic Acid↗
PubMed1988

Clinical and experimental study of pancreatic exocrine function after pancreaticoduodenectomy for periampullary carcinoma.

The residual pancreatic exocrine function before and after pancreaticoduodenectomy (PD) for periampullary carcinoma was studied clinically as well as experimentally. In clinical instances (n = 35), the N-Benzoyl-L-Tyrosil-p-Aminobenzoic Acid test (BTPABA test) before and within two months after PD revealed reduction of the function compared with those in the control study. However, the test result one year after PD was improved compared with those before and within two months after operation, without differences from that of the control group. In new canine PD models in which drainage of the pancreatic duct, 50 per cent pancreatectomy and duodenojejunectomy were performed after three months of pancreatic duct obstruction, fibrosis surrounding the pancreatic duct was disclosed. However, the results of examination five months after PD revealed a milder degree of pancreatic fibrosis without aggravation of the lesion. The aforementioned findings indicated that the exocrine pancreas before PD was impaired due to obstructive pancreatitis and that the postoperative pancreatic function was well preserved at the level close to that in the control group even after approximately 50 per cent resection of the pancreas, if pancreatic duct drainage was effectively performed.

4-Aminobenzoic Acid↗
PubMed2000

The effect of side-chain, para-aminobenzoyl region, and B-ring modifications on dihydrofolate reductase binding, influx via the reduced folate carrier, and cytotoxicity of the potent nonpolyglutamatable antifolate N(alpha)-(4-amino-4-deoxypteroyl)-N(delta)-hemiphthaloyl-L- ornithine.

N(alpha)-(4-Amino-4-deoxypteroyl)-N(delta)-hemiphthaloyl-L-o rnithine (PT523) is an unusually tight-binding dihydrofolate reductase (DHFR) inhibitor and is efficiently taken up into cells via the reduced folate carrier (RFC). Unlike classical DHFR inhibitors with a glutamate side chain, such as methotrexate and aminopterin, PT523 cannot form polyglutamates. Thus, it resembles lipophilic antifolates such as trimetrexate in not requiring metabolic activation by folylpolyglutamate synthetase in order to produce its antifolate effect. However, in contrast to trimetrexate, PT523 retains growth inhibitory activity in cells with the multidrug resistance phenotype. As part of the preclinical development of this drug, we have performed systematic modification of several regions of the PT523 molecule, with the aim of defining the optimal structural features for DHFR binding, influx into cells via the RFC, and the ability to inhibit cell growth. The following structure-activity correlations have emerged from this ongoing investigation, and are discussed: (1) the hemiphthaloylornithine side chain has the optimal length; (2) the preferred location of the aromatic carboxyl group is the ortho position; and (3) replacement of the phenyl ring of the para-aminobenzoic acid moiety by naphthalene, of nitrogen at the 10-position of the bridge by carbon, and of nitrogen at the 5- and/or 8-position of the B-ring by carbon are all well tolerated. Several of the second generation analogs of PT523 are more potent DHFR inhibitors and better RFC substrates than PT523 itself, and are more potent inhibitors of tumor cell growth in culture.

4-Aminobenzoic Acid↗
PubMed1998

Enantioselective N-acetylation of N-desisopropylpropranolol by rat liver acetyltransferase.

The enantioselective N-acetylation of N-desisopropylpropranolol (NDP), one of the main metabolites of propranolol (PL), by rat liver acetyltransferase (AT), was investigated. R(+)-NDP or S(-)-NDP was used as a substrate at concentrations ranging from 10 to 200 microM. The cytosol fraction of a rat liver containing 3.93 mg protein/ml served as the source of AT. For 1-amino-3-(1-naphthyloxy)-2-propanol (AcNDP) formation from R(+)-NDP or S(-)-NDP in the presence of infinite AcCoA (250 microM), the Km value was calculated to be 67.5 or 62.4 microM, and the Vmax value was 0.462 or 0.205 nmol/min/mg protein. Based on these findings, the enantioselective N-acetylation of NDP was proved, i.e., AcNDP formation from R(+)-NDP was found to take place more easily than that from S(-)-NDP. Furthermore, AcNDP formation from NDP was competitively inhibited by the exogenous arylamine, p-aminobenzoic acid (PABA), which is well-known to be a typical substrate of AT. The presence of enantioselective inhibition for AcNDP formation was thus confirmed based on the Ki values, 440 microM in the case of R(+)-NDP and 250 microM in the case of S(-)-NDP, respectively, i.e. two-fold enantioselective inhibition was demonstrated based on the Ki values in S(-)-enantiomer in comparison with R(+)-enantiomer.

4-Aminobenzoic Acid↗
PubMed1996

New sensitive method for the determination of hydrochlorothiazide in human serum by high-performance liquid chromatography with electrochemical detection.

A HPLC method with a very sensitive electrochemical detection has been developed for determining the diuretic agent hydrochlorothiazide (HCT) in serum of volunteers to whom a single dose of the fixed combination of 12.5 mg HCT and 25 mg triamterene was administered. In the present method samples (0.2 ml serum, pH 7) were purified by extraction of HCT into 5 ml tert.-butyl-methyl ether. The separated organic phase was spiked with p-aminobenzoic acid (PABA) standard. The separation was performed on a reversed-phase C18 column using phosphate buffer-acetonitrile (90:10). A coulometric cell was used to measure HCT and an ultraviolet detector for PABA. The limit of quantitation for serum samples of only 200 microliters was 5 ng/ml (i.e. 60 pg HCT/injection) with a good reproducibility (1-8%). Short retention times were found: 1.2 min for PABA and 5.8 min for HCT.

4-Aminobenzoic Acid↗
PubMedDate not supplied

PCR and flow cytometric analysis of paclitaxel-inhibited arylamine N-acetyltransferase activity and gene expression in human osteogenic sarcoma cells (U-2 OS).

Human epidemiological studies suggest an association between N-acetyltransferase (NAT) activity and the incidence of bladder and colorectal cancers. In this study, paclitaxel was selected to examine the inhibition of arylamine NAT activity, gene expression and 2-aminofluorene-DNA adduct formation in a human osteogenic sarcoma cell line (U-2 OS). The activity of NAT was determined by high performance liquid chromatography (HPLC) assay for the amounts of acetylated 2-aminofluorene (AF) and p-aminobenzoic acid (PABA) and nonacetylated AF and PABA. Human osteogenic sarcoma cell cytosols and intact cells were used to examine the NAT activity, gene expression and AF-DNA adduct formation. The results demonstrated that NAT activity percent of NAT in examined cells, gene expression (NAT1 mRNA) and AF-DNA adduct formation in human osteogenic sarcoma cells were inhibited and decreased by paclitaxel in a dose-dependent manner. The results also demonstrated that paclitaxel decreased the apparent values of Km and Vmax from intact human osteogenic sarcoma cells (U-2 OS). Thus, paclitaxel is an uncompetitive inhibitor of the NAT enzyme.

2-Acetylaminofluorene↗
PubMedDate not supplied

Microbial receptor assay for rapid detection and identification of seven families of antimicrobial drugs in milk: collaborative study.

A microbial competitive receptor assay for detecting residues of antibiotic families in milk was studied collaboratively by 13 laboratories. The drugs and levels (ppb) tested in this study include penicillin G, 4.8; cephapirin, 5.0; cloxacillin, 100; tetracycline, 2000; chlortetracycline, 2000; oxytetracycline, 2000; erythromycin, 200; lincomycin, 400; clindamycin, 400; sulfamethazine, 75; sulfamethoxazole, 50; sulfisoxazole, 50; streptomycin, 1000; novobiocin, 50; and chloramphenicol, 800. In this method, microbial cells added to a milk sample provide specific binding sites for which 14C or 3H labeled drug competes with drug residues in the sample. The 14C or 3H binding to the specific binding sites is measured in a scintillation counter and compared with a zero standard milk. If the sample is statistically different from the zero standard, it is positive. The assay takes about 15 min. The binding reaction occurs between the receptor site and the drug functional group, so all members of a drug family are detected. In this case, beta-lactams, tetracyclines, macrolides, aminoglycosides, novobiocin, chloramphenicol, and sulfonamides, including p-aminobenzoic acid (PABA) and its other analogs, are detectable. The incidence of false negative determinations among samples is about 1%; the incidence of false positives is about 3%. For negative cases, the relative standard deviations for repeatability ranged from 0 to 5% and for reproducibility from 0 to 6%. For positive cases, relative standard deviations ranged from 0 to 13% for repeatability and from 0 to 14% for reproducibility. The method has been adopted official first action.

4-Aminobenzoic Acid↗
PubMed1998

Short-term and long-term pancreatic exocrine and endocrine functions after pancreatectomy.

Exocrine and endocrine functions of the pancreas were assessed in 44 Japanese patients who underwent pancreatic head resection. Functions were analyzed comparing levels before surgery, at a short-term follow-up (<2 months), and at a long-term follow-up (12-31 months). The N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) excretion test, fasting blood sugar (FBS) level, and oral glucose tolerance test (OGTT) were used to determine pancreatic function. The patients were divided into three groups according to the size of the main pancreatic duct: group 1, 15 patients with a normal sized duct (< or =3 mm); group 2, 20 with a moderately dilated duct (>3 mm, <10 mm); and group 3, 9 with a markedly dilated duct (> or =10 mm). The mean BT-PABA value (6-hr urinary PABA recovery rate) in group 1 showed no change during the postoperative period. In contrast, the BT-PABA values in groups 2 and 3 had dropped by the short-term follow-up and returned to the preoperative level by the long-term examination. FBS and 120-min OGTT levels were not different between the three groups preoperatively. Although these values showed no change in all the three groups at the short-term measurements, the FBS in group 3 and 120-min levels in all the three groups had increased at the long-term. These findings suggest that exocrine pancreatic function shows a short-term deterioration in patients with a dilated pancreatic duct but recovers to the preoperative level over the long term after pancreatic head resection. Endocrine insufficiency, however, may occur at a long-term point after surgery irrespective of the preoperative pancreatic ductal dilatation.

4-Aminobenzoic Acid↗
PubMed1989

Photoallergy to benzophenone.

Incorrect diagnosis of photoallergy to sunscreen products represents a unique clinical dilemma. Increasing sunscreen usage for suspected idiopathic photosensitivity or a change to a sunscreen containing the same photoallergen only worsens the problem. While photoallergy to p-aminobenzoic acid and its esters is well known by dermatologists and the lay public, benzophenone photoallergy is not well appreciated. We report herein the cases of four individuals with photoallergy to oxybenzone in sunscreens. It is likely that such reactions will become more commonplace since oxybenzone is by far the most frequently used agent in modern, high sun protection factor sunscreens (greater than 8 sun protection factor) being marketed today.

4-Aminobenzoic Acid↗
PubMed1986

Mechanisms of sulfadoxine resistance in Plasmodium falciparum.

Three possible mechanisms of resistance to sulfadoxine were investigated in resistant Plasmodium falciparum: drug uptake, metabolism and alternate pathways. Uptake of [35S] sulfadoxine was markedly reduced in resistant plasmodia. By Thin Layer Radiochromatography it could be demonstrated that plasmodia do not metabolize sulfadoxine to pharmacologically inactive forms. Metabolism of sulfadoxine to the toxic analog of dihydropteroate is reduced in resistant plasmodia. Para-aminobenzoic acid (pABA) is not an essential nutrient for sulfonamide-resistant plasmodia. Instead, they seem to be able to synthesize pABA de novo. Four enzymes of the respective biosynthetic chain were demonstrated in isolated plasmodia: 3-deoxy-D-arabino-heptulosonate-7-phosphate synthetase (EC 4.2.1.15), shikimate dehydrogenase (EC 1.1.1.25), shikimate kinase (EC 2.7.1.71) and pABA synthetase. We conclude that these three effects account for the reduced sulfonamide stress observed in the resistant parasite.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed2002

Spectrophotometric determination of some chemotherapeutic agents using acetyl acetone.

Acetyl acetone is introduced as a new coupling agent for the spectrophotometric determination of some chemotherapeutic agents, such as metoclopramide, dapsone, p-aminobenzoic acid, and cisapride in both pure and dosage forms. The method is based on the diazo-coupling reaction of these chemotherapeutic agents with a new coupling agent, acetyl acetone, in an alkaline medium. The optimum reaction conditions and other analytical parameters are evaluated. The influence of the substrates commonly employed as excipients with these chemotherapeutic agents has been studied. The method is simple, rapid, and sensitive. The results obtained compare favorably with those obtained with other reference methods.

4-Aminobenzoic Acid↗
PubMed1988

Sensitivity and specificity of radioimmunoassay of serum trypsin-like immunoreactivity for the diagnosis of canine exocrine pancreatic insufficiency.

Concentrations of serum trypsin-like immunoreactivity (TLI) measured by radioimmunoassay were low (less than 1.9 micrograms/L) in 25 dogs with exocrine pancreatic insufficiency (EPI), compared with 100 clinically normal (control) dogs (5.2 to 34.0 micrograms/L; P less than 0.001; sensitivity, 100%). Serum TLI concentrations (5.5 to 35.0 micrograms/L) in a group of 50 dogs with small intestinal disease (SID) were not significantly different from those of control dogs, values being greater than the lower limit of the control range in all cases (specificity, 100%). Results of bentiromide (N-benzoyl-L-tyrosyl-p-aminobenzoic acid [BT-PABA]) tests and fecal proteolytic activity (determined by use of an azocasein substrate) were abnormal in 21 of 22 dogs with EPI (sensitivity, 95%). Bentiromide test results were subnormal in 13 of 35 dogs with SID (specificity, 63%), whereas fecal proteolytic activity was subnormal in 7 of 34 dogs with SID (specificity, 79%). It was concluded that assay of serum TLI is a highly sensitive and specific test for the identification of dogs with EPI.

4-Aminobenzoic Acid↗
PubMed1984

Effects of trypsin inhibitor on the remnant pancreas after 85 percent pancreatectomy in rats.

Major resection of the pancreas leads to disorders of the endocrine and exocrine pancreas. The effect of a trypsin inhibitor on the remnant pancreas was studied in rats after 85 percent pancreatectomy. Impairments of the glucose elimination rate and the integrated insulin response after 85 percent pancreatectomy were improved by means of oral administration of a synthetic trypsin inhibitor for 4 and 12 weeks. The pancreatic insulin content in the animals treated with trypsin inhibitor for 13 weeks increased to about 1.3 times than that obtained in control animals. The exocrine pancreatic function in 85 percent pancreatectomized rats treated with trypsin inhibitor for 4 weeks and 12 weeks showed substantial improvement as shown by the test with N-benzoyl-L-tyrosil-p-aminobenzoic acid (BT-PABA). The pancreatic amylase, lipase, and protein contents in the animals treated with trypsin inhibitor were increased to 1.9, 1.7 and 2.1-fold, respectively, as compared to control animals for 13 weeks. Histologic examination showed a decrease in abnormal islets of Langerhans, and a tendency toward hypertrophy of the acinar cells. These results suggest that oral administration of a trypsin inhibitor to rats is effective in improving pancreatic endocrine and exocrine functions after 85 percent pancreatectomy.

4-Aminobenzoic Acid↗
PubMed2002

Influence of composition on rate of polymerization contraction of light-curing resin composites.

A slow contraction may result in reduced gap formation when a restorative resin polymerizes in a dental cavity. It was the aim in the present work to investigate the rate of contraction in relation to composition of experimental light-curing resin composites. The monomer of the resin composites consisted of mixtures of BisGMA, TEGDMA, and in one series HEMA. The resins contained varying amounts of initiators, co-initiators, and inhibitor, and were made composite by adding a silanized glass filler to a content of 74% by weight of the composite paste. The polymerization contraction up to 120 sec was determined by means of the bonded-disk method. Within the ranges studied, the concentration of initiator and co-initiator in the monomer mixture had only an insignificant influence on rate of polymerization. In comparison to camphorquinone, the initiators 1-phenyl-1,2-propanedione and benzil reduced the rate of polymerization without affecting the final contraction. In comparison to N,N-dimethyl-p-aminobenzoic acid ethyl ester, N,N-cyanoethyl methylaniline was as effective, while N,N-diethanol-p-toluidine was less effective as co-initiator. A relatively high content of the inhibitor methoxyhydroquinone reduced the initial rate but not the final polymerization contraction. The rate of polymerization increased with the level of HEMA and TEGDMA in the monomer mixture. It was concluded that intrinsic slow cure may be obtained with certain compositions of resin composites without impairing the final extent of polymerization.

4-Aminobenzoic Acid↗
PubMed1999

A method for genotyping murine arylamine N-acetyltransferase type 2 (NAT2): a gene expressed in preimplantation embryonic stem cells encoding an enzyme acetylating the folate catabolite p-aminobenzoylglutamate.

Mice have three arylamine N-acetyltransferase (NAT) isoenzymes (NAT1, NAT2, and NAT3) of which NAT2 is known to be polymorphic. Humans have two polymorphic isoenzymes, NAT1 and NAT2. The isoenzymes mouse NAT1 and human NAT2 are expressed predominantly in the liver and intestine and are involved in drug and xenobiotic metabolism. Mouse NAT2 and human NAT1 have a widespread tissue distribution and the folate catabolite p-aminobenzoylglutamate (pAB-Glu) has been proposed as a candidate endogenous substrate. All mice have detectable NAT2 activity, although inbred mouse strains have either a fast or slow acetylator phenotype conferred by the presence of either NAT2*8 (fast) or NAT2*9 (slow) alleles at the NAT2 locus. In this report, we describe a simple method for distinguishing these murine alleles by polymerase chain reaction followed by restriction fragment length polymorphism analysis. We compared the tissue distribution of the acetylation activity found in both fast (C57BL/6J) and slow (A/J) acetylating strains of mice using pAB-Glu and p-aminobenzoic acid as probe substrates. It has previously been demonstrated that murine NAT2 is expressed in the neural tube prior to closure (Stanley L, Copp A, Rolls S, Smelt V, Perry VH and Sim E, Teratology 58: 174-182, 1998). We demonstrate here that murine NAT2 is expressed in preimplantation embryonic stem cells. Murine NAT2 is likely to be expressed prior to neurulation and this may be important in view of the protective role of folate in neural tube development.

4-Aminobenzoic Acid↗
PubMed2005

Quantitation of total folate in whole blood using LC-MS/MS.

An accurate method for measuring whole blood total folate using liquid chromatography with tandem mass spectrometry is described and compared to GC/MS and a chemiluminescence assay. Whole blood from normal adults (n = 15) was fortified with a [(13)C(6)]para-aminobenzoic acid (pABA) internal standard and treated with 12.1 N hydrochloric acid at 110 degrees C for 4 h to hydrolyze all folates to pABA. Contaminants in the hydrolysate were adsorbed onto a C18 SPE cartridge. The eluate containing the folate catabolite pABA was partitioned into ethyl acetate and methylesterified with trimethylsilyldiazomethane. The methyl-pABA derivatives were quantified by positive-ion atmospheric pressure chemical ionization (APCI)LC-MS/MS. An isocratic mobile phase of acetonitrile-water (70:30) (v/v) on a C18 analytical column was used with a postcolumn reagent of 0.025% formic acid. The limit of quantitation for folate was 56.6 nmol/L RBC, and the limit of detection was 22.6 nmol/L RBC. Folate levels as determined by LC-MS/MS correlated well with the chemiluminescence assay and a GC/MS method. This new LC-MS/MS method provides enhanced sample throughput (n = 36 per day) as compared to GC/MS methods. LC-MS/MS will enable accurate measurements of red blood cell (RBC) folate in nutrition surveys and clinical trials.

4-Aminobenzoic Acid↗
PubMed2004

Value of magnetic resonance cholangiopancreatography with secretin stimulation in the evaluation of pancreatic exocrine function after pancreaticogastrostomy.

BACKGROUND/PURPOSE: The aim of this study was to assess the value of magnetic resonance cholangiopancreatography with secretin stimulation (secretin-MRCP) in evaluating the remnant pancreatic exocrine reserve after pancreaticogastrostomy with pancreaticoduodenectomy. METHODS: Forty-three patients who had undergone pancreaticoduodenectomies and who were given pancreaticogastrostomies for reconstruction were studied. Dynamic MRCPs, using a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence were obtained before and up to 10 min after secretin administration. The morphologic features and diameter of the main pancreatic duct were monitored and graded before and after secretin stimulation. The results were compared with those of endoscopic findings, secretin stimulation testing with a collection of pancreatic fluid, N-benzoyl- L-tyrosyl-p-aminobenzoic acid (BT-PABA) excretion testing, and fecal chymotrypsin concentration. RESULTS: The results of secretin-MRCP were classified into three distinct groups: a good-secretion group (group 1; n=22; 51%), a moderate-secretion group (group 2; n=10; 23%), and a poor-secretion group (group 3; n=11; 26%). This MRCP classification correlated significantly with the concentrations of the pancreatic enzymes p-type amylase, lipase, and trypsin in the gastric juice. The BT-PABA test value was 59.8% in group 1, 46.1% in group 2, and 46.5% in group 3, and was significantly higher in group 1 than in groups 2 or 3. The fecal chymotrypsin concentration was 20.5 U/g in group 1, 14.5 U/g in group 2, and 0.7 U/g in group 3, and there was a significant correlation between the MRCP classification and fecal chymotrypsin concentration. CONCLUSIONS: MRCP with secretin stimulation favorably reflected the presence of remnant pancreatic exocrine function. Therefore, secretin-MRCP is a feasible and effective follow-up examination method to evaluate remnant pancreatic exocrine function after pancreaticogastrostomy.

4-Aminobenzoic Acid↗
PubMed1990

The effect of mafenide on dihydropteroate synthase.

Using intact bacterial cells, it was found that Pseudomonas aeruginosa was more susceptible to mafenide than Escherichia coli, that p-aminobenzoic acid (pABA) did not reverse or prevent inhibition by mafenide and that pABA itself was inhibitory. Under the experimental conditions used in these studies, pABA was more inhibitory to E. coli than to P. aeruginosa. It is proposed that pABA could be of use in the topical treatment of burn wounds. At the enzyme level, it was shown that mafenide did not inhibit dihydropteroate synthase. Thus, mafenide appeared not to exert its inhibitory effects in the same manner as the structurally related sulphonamides.

4-Aminobenzoic Acid↗