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Xeroderma pigmentosum--biochemical and therapeutic aspects. Case report.

Four patients with Xeroderma pigmentosum are reported: 2 diagnosed following the development of multiple cutaneous tumours, and 2 at an earlier state. The repair synthesis of DNA after ultraviolet radiation was reduced in 3 and normal in 1 patients. Para-aminobenzoic acid (PABA) was used topically as sunscreen; for those intolerant to PABA, alternatives are given. 5-fluoro-uracil had satisfactory effect against actinic keratoses. Two patients had associated neurologic and mental abnormalities compatible with deSanctis-Cacchione syndrome, a Xeroderma pigmentosum variant.

4-Aminobenzoic Acid↗

A novel concept for photovoltaic cells: clusters of titanium dioxide encapsulated within zeolites as photoactive semiconductors.

Discrete clusters of TiO(2) (of only a few titanium atoms) are prepared within the internal micropore space of zeolite Y (4.8 wt % Ti loading) and characterized by Raman spectroscopy (rutile- and anatase-like structures), electron microscopy combined with elemental analyses (coincident Si and Ti spatial distribution), and X-ray diffraction (minor zeolite crystallinity decrease). The parent TiO(2)@Y sample is modified either by adsorption of acid-organic compounds (benzoic and 4-aminobenzoic acids or catechol) or by nitrogen doping. After modification, the optical UV/Vis spectrum of the parent TiO(2)@Y (onset of the absorption band at wavelengths <300 nm and bandgap of 4.2 eV) changes, and the appearance of new bands expanding to the visible region is observed. In contrast to the inactive zeolite Y matrix, all the zeolite-encapsulated TiO(2) species exhibit a photovoltaic response. The influence of the I(2)/I(3) (-) concentration in the electrolyte solution on the temporal profile of the photovoltage clearly shows that I(2)/I(3) (-) is also a suitable carrier for the positive charge in zeolite-based photovoltaic devices. The photocurrent response and the efficiency of the photovoltaic cell based on zeolite-encapsulated TiO(2) materials depend on the nature of the organic modifier and on the N-doping. The most efficient photovoltaic cell is that based on N-doped TiO(2)@Y, which exhibits a V(OC) (voltage at open circuit) of 270 mV, an I(SC) of 5.8 muA (current at short circuit), and a fill factor (FF) of 0.4. Although these values are low compared to current dye-sensitized TiO(2) solar cells, our findings could open up a promise for a stimulating research on the photovoltaic activity of zeolite-based host-guest solids.

Journal Article↗

Chemically defined media for the cultivation of Naegleria: pathogenic and high temperature tolerant species.

Chemically defined minimal media for the cultivation of high temperature tolerant and pathogenic Naegleria spp. have been developed. A defined minimal medium, identical for N. fowleri and N. lovaniensis, consists of eleven amino acids (arginine, glycine, histidine, isoleucine, leucine, methionine, phenylalanine, proline, threonine, tryptophan, and valine), six vitamins (biotin, folic acid, hemin, pyridoxal, riboflavin, and thiamine), guanosine, glucose, salts, and metals. Three of the four strains of Naegleria fowleri tested (ATCC 30100, ATCC 30863, and ATCC 30896) and two strains of N. lovaniensis (ATCC 30467 and ATCC 30569) could be cultured beyond ten subcultures on this medium. For N. fowleri ATCC 30894 diaminopimelic acid, or lysine, or glutamic acid was also required. Mean generation time was reduced and population density increased for all strains with the introduction of glutamic acid. Glucose could be eliminated from the minimal medium only if glutamic acid was present. Without glucose, mean generation time increased and population density decreased. Diaminopimelic acid could substitute for lysin for ATCC 30894, indicating that Naegleria species may synthesize their lysine via the DAP pathway. Naegleria fowleri ATCC 30100 could be adapted to grow without serine or glycine in the minimal medium with glutamic acid added, but with mean generation time increased and population density decreased. The strain could be grown in the minimal medium in the absence of metals. For growth of N. australiensis ATCC 30958, modification of the medium by increasing metals ten-fold, substituting guanine for guanosine and adding lysine, glutamic acid, and six vitamins (p-aminobenzoic acid, choline chloride, inositol, vitamin B12, nicotinamide, and Ca pantothenate) was required.

Amino Acids↗

Development of a microtitre ELISA to quantify development of Cryptosporidium parvum in vitro.

An in situ enzyme-linked immunosorbent assay (ELISA) was developed to evaluate growth of Cryptosporidium parvum in vitro. Ninety-six-well tissue culture microtitre plates were each seeded with 4.0 x 10(4) human ileocecal adenocarcinoma (HCT-8) cells, then infected with CsCl-purified oocysts 24 h later. The growth medium consisted of RPMI 1640 supplemented with 10% fetal bovine serum, 15 mM HEPES (N-2-hydroxyethylpiperazine N'-2-ethanesulfonic acid), 50 mM glucose, 1 microgram ml-1 folic acid, 4 micrograms ml-1 4-aminobenzoic acid, 2 micrograms ml-1 pantothenic acid and 35 micrograms ml-1 ascorbic acid. Incubation conditions were at 37 degrees C in a 5% CO2/95% humidified air incubator. Oocysts were allowed to excyst in situ so that sporozoites could infect cells directly. Monolayers were then washed, new medium added, and infected cells re-incubated. Levels of infection were assessed 48 h later using a rat anti-C. parvum polyvalent antiserum directed against purified parasite membranes, followed by a goat anti-rat IgG conjugated to horseradish peroxidase and 3,3',5,5'-tetramethyl-benzidine as substrate. Using various parasite inoculating doses and incubation times, optimal results were obtained using a 90-min exposure of host cells to 2.5-3.0 x 10(4) oocysts/well. Evaluation of various concentrations of four anti-microbials (monensin, lasalocid, paromomycin and sulfadimethoxine) in the system resulted in the acquisition of precise dose-response curves for each compound.

Animals↗

Nutritional Features of Syntrophomonas wolfei.

Syntrophomonas wolfei subsp. wolfei grew poorly in a defined medium with crotonate as the energy source in the absence of rumen fluid. Thiamine, lipoic acid, biotin, cyanocobalamin, and para-aminobenzoic acid were required for growth comparable to that obtained with the rumen fluid-based medium. Iron and cobalt were also required for the growth of S. wolfei in the chemically defined medium.

Journal Article↗

[Effect of human serum albumin on transport of drugs through human erythrocyte membranes].

The binding properties to human serum albumin (HSA) and the transport of drugs through human erythrocyte membranes were examined with benzoic acid or its twenty-five derivatives (o-, m-, or p-hydroxybenzoic acid, o-, m-, or p-aminobenzoic acid, o-, m-, or p-nitrobenzoic acid, o-, m-, or p-toluic acid, o-, m-, or p-fluorobenzoic acid, o-, m-, or p-chlorobenzoic acid, o-, m-, or p-bromobenzoic acid, aspirin, salicyluric acid, alpha-resorcylic acid and gamma-resorcylic acid) and with glycosides (arbutin, salicin, glycyrrhizin and four p-nitrophenylglycosides) or their aglycons (hydroquinone, saligenin, glycyrretinic acid and p-nitrophenol). The drugs having hydroxyl group and amino group to o-site and those having nitro group, methyl group and halogen group to m- or p-site showed higher affinity with HSA and the plasma hindered the permeability of these drugs. The glycosides bind to each site (1, 2, and 3) of HSA more weakly than do their aglycons and they were difficult for plasma to hinder membrane permeation. The binding constants of each drug to HSA (Kb-site 1, Kb-site 2, Kb-site 3 and Kb-total) and the inhibition ratio (IR) related to the partition coefficient (P): Kb-site 1 (M-1) = 2.1479 x 10(3).square root of P - 5.2824.P + 2.0985 x 10(3) (R = 0.9371), Kb-site 2 (M-1) = 4.3741 x 10(3).square root of P - 15.2068.P + 6.5660 x 10(3) (R = 0.6788), Kb-site 3 (M-1) = 2.2176 x 10(4).log P + 1.2022 x 10(4) (R = 0.5227), Kb-total (M-1) = 1.0214 x 10(4).square root of P - 33.3721.P + 1.6919 x 10(4) (R = 0.7413), IR (%) = 19.885.log P + 17.916 (R = 0.8605). IR obtained from predictive equations (IR = 17.837.log P - 13.286. log Kb-site 1 + 0.175.square root of Kb-site 2 + 0.074.square root of K b-site 3 + 37.355, R = 0.9642, F = 71.4937***, ***; p < 0.001) by multiple regression analysis was compatible with experimental IR.

Benzoates↗

Further studies on the urinary metabolites of 2,4-dinitrotoluene and 2,6-dinitrotoluene in the male Wistar rat.

1. Conjugates of 2,4-dinitrobenzyl alcohol (2,4-DNB) and 2,6-dinitrobenzyl alcohol (2,6-DNB), which were major urinary metabolites of the male Wistar rat dosed orally with 2,4-dinitrotoluene (2,4-DNT) or 2,6-dinitrotoluene (2,6-DNT), were examined by hplc using potassium 2,4-dinitrobenzyl glucuronide (2,4-DNB-G), potassium 2,6-dinitrobenzyl glucuronide (2,6-DNB-G), pyridinium 2,4-dinitrobenzyl sulphate (2,4-DNB-S), and pyridinium 2,6-dinitrobenzyl sulphate (2,6-DNB-S) as authentic compounds. Other metabolites were also examined by hplc. 2. Conjugates detected from urine following administration of 2,4-DNT and 2,6-DNT were 2,4-DNB-G and 2,6-DNB-G, which accounted for about 10.7 and 17.4% of the administered dose respectively. No peaks corresponding to pyridinium 2,4-DNB-S and pyridinium 2,6-DNB-S were detected in urine samples. 3. 2-Amino-4-nitrobenzoic acid (0.71%), 4-amino-2-nitrobenzoic acid (0.52%) and 4-acetylamino-2-nitrobenzoic acid (3.9%), in addition to known metabolites 4-amino-2-nitrotoluene (0.04%), 2,4-DNB (0.25%), 2,4-dinitrobenzoic acid (6.9%) and 4-acetylamino-2-aminobenzoic acid (3.4%), were detected in ether extracts of urine of rat given 2,4-DNT. 2,6-Dinitrobenzoic acid (0.17%) and two known metabolites, 2-amino-6-nitrotoluene (0.44%) and 2,6-DNB (0.53%), were detected in ether extracts of urine of rat given 2,6-DNT.

Animals↗

Design and structural requirements of potent peptidomimetic inhibitors of p21ras farnesyltransferase.

Cysteine farnesylation of the ras oncogene product, p21ras, on its carboxyl-terminal CA1A2X box (C = cysteine, A = aliphatic, and X = methionine or serine) is required for its transforming activity. p21ras farnesyltransferase (FTase), the enzyme responsible or this important posttranslational modification can be inhibited by simple CA1A2X peptides. We have synthesized a family of CA1A2X peptidomimetics where the central 2 aliphatic amino acids are replaced by a variety of spacer groups with different shapes and conformational characteristics to investigate the structural requirements of these inhibitors. The biological activities of CA1A2X peptidomimetics, where the dipeptide "A1A2" is replaced by 3- or 4-aminomethylbenzoic acid (AMBA) and 3- or 4-aminobenzoic acid (ABA), are evaluated in a p21ras FTase inhibitory assay. Peptidomimetics Cys-4-ABA-Met and Cys-3-AMBA-Met contain spacers that provide good distance correspondence of the carboxylate and ammonium separation with that of the parent KB p21ras tetrapeptide, Cys-Val-Ile-Met, and are as potent FTase inhibitors (IC50 values of 50 and 100 nM, respectively). In contrast, replacing the central dipeptide with 4-AMBA reduced FTase inhibitory activity by 17-fold whereas replacement by 3-ABA reduces inhibitory activity of the peptidomimetics by 43-fold. Cys-4-ABA-Met (IC50 = 50 nM) is 128 times more potent as a p21ras FTase inhibitor than Cys-3-ABA-Met (IC50 = 6400 nM), yet these two peptidomimetics differ only in the substitution pattern around the phenyl ring. These results coupled with computer modeling studies demonstrate that the interaction between FTase and the peptidomimetics requires precise structural and conformational characteristics; in particular, correct positioning of the Cys and Met must be respected. Furthermore, Cys-3-AMBA-Met and Cys-4-ABA-Met are true inhibitors of p21ras FTase since they are not farnesylated by this enzyme, in contrast to Cys-Val-Ile-Met, which inhibits the enzyme by acting as alternative substrate. Computer modeling studies of the potent FTase inhibitor Cys-4-ABA-Met show that a folded conformation, where the thiol and carboxylate groups are close, is not possible. Therefore a beta-turn conformation that would result in the simultaneous coordination of the Cys-thiol and Met-carboxylate to zinc ion is not important for inhibition of p21ras FTase, as previously suggested.

Alkyl and Aryl Transferases↗

A parallel processing solid phase extraction protocol for the determination of whole blood folate.

We describe an improved whole blood folate analysis method that facilitates increased throughput compared to our previous method (Dueker et al. (2000) Anal. Biochem. 283, 266). Improvements include three items: first, a buffered solvent exchange to remove interfering amino acids, especially phenylalanine whose esters may interfere with the analysis because their retention times on the gas chromatography are close to those of the para-aminobenzoic acid (pABA) isotopomers; second, substituting an NH2 solid phase extraction step for an HPLC step permits the batch parallel processing of samples; third, replacing trifluoroacetyl derivatives of ethyl-esterified pABA isotopomers with heptafluorobutyl derivatives, which are better resolved on the GC column. The method measures pABA, a stable degradation product of folate. This simplifies sample handling and purification. Relative standard deviations are typically 5% or less and a single operator can process samples in batches of 40. Results from our GCMS method correlate (R = 0.98) with the Lactobacillus casei assay for whole blood folate. The modifications will facilitate the development of high throughput methods for whole blood folate. Our method holds promise for epidemiological and clinical studies, where accurate whole blood folate concentrations are needed. Because it is internally standardized, interlaboratory variation should be minimal.

4-Aminobenzoic Acid↗

Simultaneous determination of HIV-protease inhibitors lamivudine and zidovudine in pharmaceutical formulations by micellar electrokinetic chromatography.

A micellar electrokinetic chromatographic (MEKC) method for the simultaneous separation and determination of lamivudine (LMV) and zidovudine (ZDV) in pharmaceutical formulation has been developed. Factors that affect the separation, such as buffer pH, surfactant concentration (sodium dodecyl sulfate, SDS), organic solvents and applied voltage were optimized. Buffer consisting of 12.5 mM sodium tetraborate decahydrate and 15 mM boric acid adjusted at pH 10.8, containing 90 mM SDS and 5% (v/v) acetonitrile (ACN) was found to be suitable for the separation of the drugs. p-Aminobenzoic acid (PABA) was used as internal standard (I.S.). Detection of analytes and I.S. was performed at a wavelength of 210 nm. It was observed that both the drugs and I.S. were migrated within 20 min at the applied voltage of +10 kV. Validation of the method was performed in terms of linearity, accuracy, precision, limit of detection (LOD) and quantification (LOQ). An excellent linearity was obtained in the concentration range 10-80 microg/ml for LMV and 10-100 microg/ml for ZDV. The detection limits for LMV and ZDV were found to be 2.5 and 2.0 microg/ml, respectively. The optimized method was applied to the simultaneous determination of LMV and ZDV in pharmaceutical formulation and human plasma (spiked) samples. Recovery of both the drugs in tablet dosage form and spiked drugs in plasma were > or =99.72% (relative standard deviation (R.S.D.)< or =1.84%) and > or =80.4% (R.S.D.< or =5.4%), respectively. In the electropherogram no interfering peaks were observed in the region of analytes and I.S. due to inactive ingredients in the tablets and matrices in plasma.

4-Aminobenzoic Acid↗

Pancreatic function testing: serum PABA measurement is a reliable and accurate measurement of exocrine function.

A comparison between the NBT-PABA/14C-PABA test (NBT-PABA, n-benzoyl-tyrosyl para-aminobenzoic acid) using the PABA excretion index (PEI) and serum PABA estimation at 90 minutes has been made in 42 consecutive subjects attending for investigation of possible pancreatic disease to a District General Hospital (DGH). The PEI was unobtainable or incorrect on 38% of occasions compared with 9% for the serum test. Sensitivity, specificity, and efficiency for the PEI (n = 33 valid results) were 71%, 88%, and 79% respectively and for the serum PABA (n = 41 valid results), 95%, 90%, and 93% respectively. These results confirm that measurement of serum PABA is a simpler, more reliable, and a more accurate method of assessing pancreatic function.

4-Aminobenzoic Acid↗

The diagnostic value of the oral pancreatic function test.

An oral pancreatic function test (PFT) using the synthetic peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid can assess pancreatic exocrine function, since urinary recovery of the ingested dose is an indirect index of chymotryptic activity. We have studied 34 subjects using this oral PFT, which correctly distinguished the control group (8 subjects) from the pancreatitis group (10 patients), results correlating well with Lundh test findings. However, the test was falsely abnormal on 9 out of 16 occasions in patients with bowel or liver disease. We therefore conclude that the present test cannot distinguish small-bowel disease from pancreatic disease, which is often the diagnostic problem, and is also frequently falsely abnormal in the presence of chronic liver disease.

4-Aminobenzoic Acid↗

Inhibition of the conjugation of PABA with glycine in vitro by sulfamoyl benzoic acids, sulfonamides, and penicillins and its relation to tubular secretion.

Elimination of drug molecules via tubular secretion is an important pharmacokinetic parameter especially for oral dosage forms where an extremely short half-life would prevent their application. We have studied the inhibition in vitro of the glycination of p-aminobenzoic acid (PABA) using rat liver microsomal preparations. The I50 values, the concentration of the inhibitor that leads to 50% inhibition of glycine conjugation of PABA as compared to the control, have been determined for sulfamoyl benzoic acids, sulfonamides, and penicillins. Statistically significant regression equations were derived explaining the observed variation in I50 values as a function of lipophilicity and steric bulk of the substituents for the combined set of sulfamoyl benzoic acids and sulfonamides (n = 33). For the penicillins studied, only steric effects seem to be important for the explanation of the I50 values. Finally, regression analysis and the use of neural networks allowed the classification of compounds by their in vitro I50 values as being tubular secreted or not. Therefore, it can be concluded that the inhibition in vitro of the glycine conjugation of PABA is a useful model for the estimation of tubular secretion and drug interaction potential of acidic drug molecules in this process in vivo.

4-Aminobenzoic Acid↗

Differentiation of isomeric N-glycan structures by normal-phase liquid chromatography-MALDI-TOF/TOF tandem mass spectrometry.

The detailed characterization of protein N-glycosylation is very demanding given the many different glycoforms and structural isomers that can exist on glycoproteins. Here we report a fast and sensitive method for the extensive structure elucidation of reducing-end labeled N-glycan mixtures using a combination of capillary normal-phase HPLC coupled off-line to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and TOF/TOF-MS/MS. Using this method, isobaric N-glycans released from honey bee phospholipase A2 and Arabidopsis thaliana glycoproteins were separated by normal-phase chromatography and subsequently identified by key fragment ions in the MALDI-TOF/TOF tandem mass spectra. In addition, linkage and branching information were provided by abundant cross-ring and "elimination" fragment ions in the MALDI-CID spectra that gave extensive structural information. Furthermore, the fragmentation characteristics of N-glycans reductively aminated with 2-aminobenzoic acid and 2-aminobenzamide were compared. The identification of N-glycans containing 3-linked core fucose was facilitated by distinctive ions present only in the MALDI-CID spectra of 2-aminobenzoic acid-labeled oligosaccharides. To our knowledge, this is the first MS/MS-based technique that allows confident identification of N-glycans containing 3-linked core fucose, which is a major allergenic determinant on insect and plant glycoproteins.

Amination↗

Targeting the shikimate pathway in the malaria parasite Plasmodium falciparum.

The shikimate pathway presents an attractive target for malaria chemotherapy. Three shikimic acid analogs exhibited different effects on Plasmodium falciparum growth. (6R)-6-Fluoro-shikimate and (6S)-6-fluoro-shikimate inhibited growth (50% inhibitory concentrations, 1.5 x 10(-5) and 2.7 x 10(-4) M, respectively), whereas 2-fluoro-shikimate had no effect. para-Aminobenzoic acid abrogated the inhibition, demonstrating that the shikimate pathway was specifically targeted.

4-Aminobenzoic Acid↗

Clinical and laboratory characterization of Basenjis with immunoproliferative small intestinal disease.

Eleven adult Basenji dogs with immunoproliferative small intestinal disease (IPSID) were studied. Two items of history related to the digestive tract were characteristic: (i) chronic intractable diarrhea in most dogs, and (ii) progressive emaciation. Anorexia was intermittent in only a few dogs. In addition, skin lesions of various degrees of severity were observed, including alopecia of pinnae and ventrum, hyperpigmentation and hyperkeratosis of pinnae, and necrosis and ulcerations of margins of pinnae. The cause of the skin lesions was not determined; however, hypothyroidism did not appear to contribute to the skin changes. Standard hematologic and serum chemical values were not consistently abnormal. However, a poorly regenerative anemia, mild neutrophilia, and increased aspartate aminotransferase and alanine aminotransferase activities were generally observed in severely affected dogs. The Pelger-Huet anomaly was identified in dog 3. Maldigestion and malabsorption as determined by the N-benzoyl-L-tyrosyl-p-aminobenzoic acid and d-xylose test was documented to varying degrees in dogs with IPSID. Maldigestion was correlated with functional pancreatic exocrine insufficiency. Severe malabsorption was documented in only 3 dogs. Serum gastrin values were evaluated in these dogs because of a prior observation of parietal cell hyperplasia and gastric ulceration. Hypergastrinemia was documented in 3 dogs. Additional studies will be necessary to determine whether an acid hypersecretory state contributes to the pathogenesis of IPSID in Basenjis.

4-Aminobenzoic Acid↗

Surface-enhanced-Raman-scattering-inducing nanoprobe for spectrochemical analysis.

This paper describes a new nanoprobe that induces the surface-enhanced Raman scattering (SERS) effect when brought into contact with chemicals on any type of surface. The SERS-inducing probe was fabricated from an optical fiber that was tapered to a tip 100 nm in diameter. A thin layer of silver islands was applied to the tip of the tapered fiber via thermal evaporation to induce the SERS effect. The small scale of the tip may be amenable to localized, nondestructive SERS-based analyses of surfaces with high spatial selectivity. Because the contact probe itself induces the SERS effect, no modification of the sample is required. Direct analysis at submicrometer spatial selectivity is therefore possible for analyte compounds on any type of surface. Various optimization studies and preliminary evaluations were performed. A 10-nm silver thickness was determined to yield the optimum SERS effect. A 25% relative standard deviation in SERS signal was observed for five different probe tips. As a demonstration of the SERS-inducing capability of the probe, Raman spectra were recorded for glass surfaces coated with brilliant cresyl blue and p-aminobenzoic acid before and during contact with the SERS-inducing nanoprobe.

4-Aminobenzoic Acid↗

Characterization of mutationally altered dihydropteroate synthase and its ability to form a sulfonamide-containing dihydrofolate analog.

Among spontaneous mutants of Escherichia coli selected for resistance against sulfonamides, thermosensitive strains were found. These were shown to possess a changed dihydropteroate synthase (EC 2.5.1.15), which had a substantially higher Km value for its normal substrate, p-aminobenzoic acid, and an about 150-fold higher Km for sulfonamides. The mutationally changed dihydropteroate synthase was found to be thermosensitive by in vitro assays. The thermosensitivity was used as an enzyme marker to demonstrate the complex formation between 2-amino-4-hydroxy-6-pyrophosphorylmethyl pteridine and sulfonamides by partially purified dihydropteroate synthase. The formation of folate from 2-amino-4-hydroxy-6-pyrophosphorylmethyl pteridine and p-aminobenzoylglutamic acid by dihydropteroate synthase was found to be very sensitive to inhibition by sulfonamides and very inefficient with the mutationally changed enzyme.

4-Aminobenzoic Acid↗