1H dynamic nuclear polarization in supercritical ethylene at 1.4 T

(1)H dynamic nuclear polarization (DNP) has been measured in supercritical ethylene in the pressure range 60-300 bar in an external field of 1.4 T. A single-cell sapphire tube was used as a high-pressure cell, and powdered 1,3-bisdiphenylene-2-phenyl allyl (BDPA) free radicals were added and distributed at the wall of the cell. At all pressures the dominant DNP mechanism was a positive Overhauser enhancement, caused by proton-electron contact interactions at the fluid/solid radical interface. The observed enhancements varied from 12 at 60 bar to 17 at 300 bar. Besides the Overhauser enhancement, small solid state and thermal mixing enhancements also were observed, indicating that part of the ethylene was adsorbed at the radical surface for a prolonged time. The impacts of the experimental conditions on the Overhauser enhancement factors are discussed, and enhancements of at least 40-60 are estimated when the EPR saturation factor and the leakage factor become maximal. These data indicate that DNP-enhanced NMR has the potential of extending the impact of NMR in research areas involving supercritical fluids.

Localization of N-acetyltransferases NAT1 and NAT2 in human tissues

Human acetyl coenzyme A-dependent N-acetyltransferase (EC 2.3.1.5) (NAT) catalyzes the biotransformation of a number of arylamine and hydrazine compounds. NAT isozymes are encoded at 2 loci; one encodes NAT1, formerly known as the monomorphic form of the enzyme, while the other encodes the polymorphic NAT2, which is responsible for individual differences in the ability to acetylate certain compounds. Human epidemiological studies have suggested an association between the "acetylator phenotype" and particular cancers such as those of the bladder and colon. In the present study, NAT1- and NAT2-specific riboprobes were used in hybridization histochemistry studies to localize NAT1 and NAT2 mRNA sequences in formalin-fixed, paraffin-embedded human tissue sections. Expression of both NAT1 and NAT2 mRNA was observed in liver, gastrointestinal tract tissues (esophagus, stomach, small intestine, and colon), ureter, bladder, and lung. In extrahepatic tissues, NAT1 and NAT2 mRNA expression was localized to intestinal epithelial cells, urothelial cells, and the epithelial cells of the respiratory bronchioles. The observed heterogeneity of NAT1 and NAT2 mRNA expression between human tissue types may be of significance in assessing their contribution to known organ-specific toxicities of various arylamine drugs and carcinogens.

Modified spectral editing methods for (13)C CP/MAS experiments in solids

The spectral editing approach of Zilm and coworkers utilizes polarization, polarization inversion, and spin depolarization methods for enhancing or suppressing NMR spectral lines in solids. The proposed pulse sequences allow nonprotonated C, CH, CH(2), and CH(3) types of carbon resonances to be separated from one another and identified accordingly. The former method tentatively separates the nonprotonated C and CH(3) peaks with a cutoff shift of 35 ppm. This shift is a reasonable demarcation shift for a preponderance of organic molecules, but exceptions do exist that could constitute a serious drawback in a few instances. The new approach separates the nonprotonated C and CH(3) carbon peaks unequivocally using modified pulse sequences similar to those of Zilm. Further, both the CH only and CH(2) only spectra, respectively, can be acquired directly from combining so called (+) and (-) sequences using different spectral delay periods and pulse parameters. The (+) and the (-) pulse sequences produce signals for the nonprotonated and methyl carbons that have essentially the same amplitude but opposite phases. These spectra, combined with the previously reported CH(3) and nonprontonated C only spectra, offer a complete spectral editing technique for solid samples. Examples of these spectral editing methods are provided for 3-methylglutaric acid, fumaric acid monoethyl ester, and two complex natural products: methyl o-methylpodocarpate and 10-deacetylbaccatin III.

Impact of suppressive antiviral therapy on the health related quality of life of patients with recurrent genital herpes infection

OBJECTIVE

To investigate whether suppressive antiviral therapy improves health related quality of life in patients with recurrent genital herpes.

METHODS

Health related quality of life was measured using the disease specific recurrent genital herpes quality of life questionnaire (RGHQoL) as part of a randomized, double blind, 52 week, placebo controlled, dose ranging study of once and twice daily valaciclovir or aciclovir for the suppression of recurrent genital herpes in patients with six or more recurrences per year.

RESULTS

Of 1479 participants, 1349 patients completed the baseline questionnaire. There were no significant baseline differences in RGHQoL score between any of the treatment groups. After 3 months there were significantly greater improvements in mean RGHQoL scores for all active treatment groups compared with placebo (p < 0.05). Mean RGHQoL score improvements from baseline remained significantly higher in the active treatment groups than in the placebo group after 6 and 12 months, indicating that the improved health related quality of life in patients receiving suppressive antiviral therapy was sustained over a prolonged period of time.

CONCLUSION

Suppressive antiviral therapy is an effective strategy for improving the quality of life of patients with recurrent genital herpes. These improvements in quality of life are sustained over time, thus enhancing the clinical benefit in the long term management of this condition.

Hydroxyapatite thin films deposited onto uncoated and (Ti,Al, V)N-coated Ti alloys

Plasma-sputtered hydroxyapatite (HA) thin coatings ( approximately 1 microm) were deposited onto uncoated and (TiAlV)N-coated Ti-6Al-4V-alloy substrates at low temperatures. The (TiAlV)N coating interlayer was deposited by reactive sputtering. Depositions were achieved by utilizing unbalanced and balanced magnetrons in a capacitively coupled RF plasma. Characterization of the thermostability, bioerosion resistance, and chemical composition of the coating layer was examined by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). The results show that for deposition temperatures as low as 67 degrees C, the crystalline phase of the HA coating still is clearly detectable and that the underlying (TiAlV)N coating can increase the crystallinity and thermostability of the HA coating before and after heat treatment. The thin ( approximately 1 microm) sputtered HA coating shows strong HA characteristic peaks in the FTIR spectra even after a 30-day dissolution test. The experimental results show that a multilayer structure comprised of a bioinert (TiAlV)N and bioactive HA coating has the potential to improve the biocompatibility of implant materials. The bioinert (TiAlV)N coating also may provide a long-term stable interface between bone tissue and an alloy implant after the bioactive HA coating is remodeled by the surrounding tissue.

Resolution enhancement in 13C and 15N magic-angle turning experiments with TPPM decoupling

Many solid-state spectra have been shown to have problems related to the poor proton decoupling of carbon nuclei in methylene groups under conditions of slow magic-angle turning. Two-pulse phase-modulation (TPPM) decoupling during the 2D PHORMAT chemical shift separation experiment is shown to be more effective in comparison to that obtainable at much higher spin rates using conventional CW decoupling. TPPM decoupling can also alleviate similar inadequacies when observing the 15N nucleus, particularly with NH2 groups. This is demonstrated in the 15N resonances of fully labeled l-arginine hydrochloride, where a line narrowing of about a factor of two was observed at moderate rotation rates. This significant advantage was also obtained at turning frequencies as low as 500 Hz.

NAD(P)H:quinone oxidoreductase: polymorphisms and allele frequencies in Caucasian, Chinese and Canadian Native Indian and Inuit populations

NAD(P)H:quinone oxidoreductase (NQO1) catalyses the two-electron reduction of quinone compounds. NQO1 is involved in the reductive bioactivation of cytotoxic antitumour quinones such as mitomycin C, but also plays a protective role against the carcinogenicity and mutagenicity of quinones, their precursors and metabolites. Three alleles have been identified in the human population: the functional Arg139/Pro187 allele (which we have termed NQO1*1); the nonfunctional allele Arg139/Ser187 (NQO1*2) and the Trp139/Pro187 allele (NQO1*3), which is associated with a diminished activity. We applied polymerase chain reaction-based genotyping assays to characterize interethnic variability in the frequency of NQO1 alleles in Caucasian (n = 575), Canadian Native Indian (n = 110), Canadian Inuit (n = 83) and Chinese (n = 86) populations. The NQO1*2 allele was found at significantly higher frequencies in Chinese (0.49) and Native North American populations (Inuit 0.46; Canadian Native Indians 0.40) compared with Caucasians (0.16). The NQO1*3 allele was not observed in Inuit individuals, and occurred at a lower frequency than the NQO*2 allele in Caucasians (0.05), Chinese (0.04) and Canadian Native Indians (0.01). Our results predict that a greater proportion of Orientals and related ethnic groups lack, or have reduced, NQO activity relative to Caucasians. Affected individuals may not only exhibit resistance to quinone-based cancer therapy because of a decreased production of cytotoxic drug metabolites, but may also be more susceptible to toxicities associated with toxicants.

Variants of N-acetyltransferase NAT1 and a case-control study of colorectal adenomas

N-acetyltransferase NAT1, together with enzymes CYP1A2 and NAT2, helps convert heterocyclic amines to mutagens. Epidemiologic studies of the association of variants of these enzymes with colorectal cancer may provide indirect support for a heterocyclic amine mechanism. We used single strand conformation polymorphism and heteroduplex analysis to screen fro mutations in the NAT1 coding region in a case-control study (n = 932) of colorectal adenomas, which are precursors to cancer. Thirteen different single-base mutations were found: C97T, C190T, T402C, G445A-G459A-T640G ( a combination of three mutations), C559T, G560A, A613G, A752T, T777C, G781A, and A787G. Function of novel mutations was tested by bacterial production of enzymes and measurements of Km, Vmax, and stability. However, on 24-control individuals and 18 cases carried an inactivating NAT1 mutation. When combined with our data on the NAT2 acetylation polymorphism, we saw no evidence for an association between N-acetyltransferases and prevalence of adenomas. Larger sample sizes are required for further evaluation.

The role of cost-consequence analysis in healthcare decision-making

A greater understanding of value associated with new pharmaceutical products should lead to better decision-making. Most commonly cost-effectiveness ratios (CERs) are used to indicate value; however, researchers have recently shown that CER estimates are rarely used by decision-makers in making formulary decisions. In this article, a cost-consequence approach to estimating the value for money of a new treatment for a specific disease is described. Using a cost-consequence approach, the impact of the new treatment on lifetime resource use and costs (including specific healthcare service use and costs, and productivity losses) and health outcomes (including disease symptoms, life expectancy and quality of life) for an individual or group of individuals is estimated and presented in a tabular format. The cost-consequence format is more likely to be approachable, readily understandable and applied by healthcare decision-makers than a simple CER. The decision-maker may use selected items from the cost-consequence analysis to compute composite measures of drug value, such as cost per life-year gained or cost per quality-adjusted life-year (QALY) gained. In general, the cost-consequence approach, by making the impact of the new treatment as comprehensive and transparent as possible, will enable decision-makers to select the components most relevant to their perspective and will also give them confidence that the data are credible to use as the basis for resource allocation decisions.

Novel sulfotransferases cloned by RT-PCR: real proteins or PCR artifacts?

During studies designed to subclone human phenol sulfotransferase (STP and STM) sequences for use in heterologous E. coli-based expression systems, we designed two oligonucleotide primers that would allow for the simultaneous PCR amplification of expression cassettes containing the coding regions of the STP1, STP2 and STM cDNAs. Following total RNA isolation from human liver, reverse transcription of cDNA, PCR amplification under standard conditions, plasmid subcloning and restriction analysis to select for suitable ST recombinants, we recovered plasmids containing inserts corresponding to STP1, STP2 and STM. However, ten additional, closely related but apparently novel ST sequences were also isolated. Alignments of the three known ST sequences (and one published allelic variant) with these new clones revealed that each one appears to be a PCR-generated modular chimera possessing a combination of DNA segments derived from STP1, STP2 and STM. This observation should serve as an alert to the potential pitfalls of using PCR techniques for the cloning of highly related genes and their cDNA products, especially when PCR primer design allows for the amplification of multiple products in a single reaction.

Identification and characterization of variant alleles of human acetyltransferase NAT1 with defective function using p-aminosalicylate as an in-vivo and in-vitro probe

Although several variant alleles at the human NAT1 gene locus have been reported, their relationship to phenotypic variations in NAT1 function remains unclear. We have used in-vivo and invitro phenotyping tests, along with PCR-based cloning and heterologous expression, to investigate the extent of variation in NAT1 function and to characterize novel allelic variants at the NAT1 gene locus. The NAT1-selective substrate p-aminosalicylic acid (PAS) was used as a probe for NAT1 function. In-vivo PAS acetylation rates were estimated by determining the ratio of PAS to N-acetylated PAS (AcPAS) in urine and plasma following the oral ingestion of Nemasol Sodium. Excluding outliers, a 65-fold variation in the urinary AcPAS:PAS ratio was observed (n = 144), while a 5.6-fold variation in the plasma AcPAS:PAS ratio was seen in a subset (n = 19) of this sample. Urinary and plasma ratios correlated moderately (r = 0.74, p < 0.0005). One individual (case 244) had a marked impairment of PAS N-acetylation, with 10-fold lower urinary and plasma AcPAS:PAS ratios compared with other subjects. Biochemical investigations in whole blood lysates from case 244 suggested a NAT1 kinetic defect, with a 20-fold increased apparent K(m) for PAS and a 90-fold decreased Vmax for AcPAS formation. We subcloned, sequenced and expressed the protein-coding regions of the NAT1 alleles from case 244 and from seven other selected probands. Sequence analysis revealed the presence of two new variant alleles, designated as NAT1 x 14 and NAT1 x 15, in case 244, as well as one variant, NAT1 x 11, which has been observed in previous investigations. NAT1 x 14 contained a missense mutation (G560-->A) that is predicted to change a single amino acid (Arg187-->Gln), as well as two 3' non-coding region mutations (T1088-->A and C1095-->A) that have previously been observed in the NAT1 x 10 allelic variant. NAT1 x 15 had a single nonsense mutation (C559-->T; Arg187-->stop) and, thus, encodes a truncated protein. The activity of recombinant NAT1 14 mirrored the defective enzyme function in whole blood lysates from case 244, while NAT1 15 was completely inactive. Expressed NAT1 11, on the other hand, had identical activity to the wild type NAT1 4 allele, suggesting that the coding region mutations in this variant are functionally silent. The frequencies of NAT1 x 11, NAT1 x 14 and NAT1 x 15 were 0.021, 0.028 and 0.014 (n = 288 alleles), respectively, suggesting that they are relatively rare in our predominantly Caucasian sample.

Technique for importing greater evolution resolution in multidimensional NMR spectrum

A very simple and general procedure that extracts constant-evolution-frequency data from a truncated multidimensional (2D, 3D, 4D, etc.) FID is described, generalized, analyzed, and illustrated. The method replaces Fourier transformation of the evolution dimension with a linear model created from a separate, high-quality 1D FID. The equivalent of high resolution in the evolution dimension can be achieved without obtaining an extensive multidimensional FID. The analysis of the 1D FID can also be used to predict the signal to noise ratio of the extracted slices that will result from various evolution dimension sampling protocols, making it possible to develop a priori an optimal sampling strategy for the multidimensional FID. The evolution dimension need not be sampled periodically. The procedure has a potential signal-to-noise ratio advantage because it extracts usable information from a multidimensional FID at short evolution times before the magnetization has decayed significantly.

Tissue-specific expression and alternative splicing of human microsomal epoxide hydrolase

Human microsomal epoxide hydrolase (HYL1) plays an important role in the detoxification of environmental compounds and drugs, such as the aromatic anticonvulsants phenytoin, carbamazepine, and phenobarbital, by converting their P450-generated epoxide metabolites into nontoxic diols. Recently, we have shown that a genetic defect altering the structure and function of the HYL1 protein is unlikely to be responsible for predisposing individuals to idiosyncratic hypersensitivity reactions from anticonvulsants. To evaluate the possible involvement of regulatory mechanisms, we used 5' rapid amplification of cDNA ends (RACE) and reverse transcription polymerase chain reaction (RT-PCR) to identify and characterize HYL1 5' cDNA ends. In addition to exon 1 (E1) previously isolated from a liver cDNA library, we isolated four new exons (E1-a, E1-c, E1-d, and E1-e) from various tissues. E1 was always directly connected to exon 2 (E2) where the translation start codon is located. E1-a, E1-c E1-d, and E1-e are alternatively spliced to E2, having either E1-a or E1-a' (a truncated form of E1-a) at the 5' end of their respective transcript. Genomic data indicate that exons E1-a and E1-c are located at least 7 kb upstream from E1. Furthermore, we demonstrated a tissue-specific expression pattern for E1-containing mRNA species, whereas E1-a-containing transcripts appear to be expressed ubiquitously. Our results provide evidence that microsomal epoxide hydrolase is regulated by multiple untranslated exons flanked by tissue-specific promoters.

Human acetyltransferase polymorphisms

Conjugation of primary amino and hydroxylamino groups with acetate, catalyzed by acetyl CoA-dependent arylamine acetyltransferase (NAT) enzymes, may play an important role in the intricate series of metabolic pathways that produce or prevent toxicity following exposure to homo- and heterocyclic arylamine and hydrazine xenobiotics. Two independently regulated and kinetically distinct human acetyltransferases are now known to exist, namely NAT1 and NAT2. Interindividual variation in NAT2 function is associated with the classical isoniazid acetylation polymorphism which was discovered over forty years ago. At last count, fifteen variant alleles at the NAT2 gene locus have been linked to the isoniazid 'acetylator phenotype', and each of these can be identified in population studies using specific PCR-based genotyping tests. On the other hand, NAT1 shows kinetic selectivity for compounds whose disposition is unrelated to the classical isoniazid acetylation polymorphism. NAT1 expression is also phenotypically variable in human populations, at least in part due to allelic differences at the NAT1 gene locus. Nine NAT1 variant alleles have been described to date, of which NAT1* 14 and NAT1* 15 clearly produce defective NAT1 proteins and lead to functional impairment in the metabolism of NAT1-selective substrates both in vivo and in vitro. On the other hand, it has been reported that the NAT1* 10 variant associates with elevated NAT1 activity and increased risk for cancers of the bladder and colon. Because of the important toxicologic consequences of allelic variation in NAT1 and NAT2 function for the metabolic activation of arylamine and heterocyclic amine procarcinogens, further studies are needed to improve our understanding of the extent of NAT allelic variation, to determine the functional capacity of each variant gene product, and to develop accurate methods of detecting them in population and epidemiological studies.

The role of xenobiotic metabolizing enzymes in arylamine toxicity and carcinogenesis: functional and localization studies

In both animal models and humans, the first and obligatory step in the activation of arylamines is N-hydroxylation. This pathway is primarily mediated by the phase-I enzymes CYP1A1, CYP1A2 and CYP4B1. In the presence of flavonoids such as alpha-naphthoflavone and flavone, both CYP3A4 and CYP3A5 have also been shown to play a minor role in the activation of food-derived heterocyclic amines. The further activation of N-hydroxyarylamines by phase-II metabolism can involve both N, O-acetylation and N, O-sulfonation catalyzed by N-acetyltransferases (NAT1 and NAT2) and sulfotransferases, respectively. Using an array of techniques, we have been unable to detect constitutive CYP1A expression in any segments of the human gastrointestinal tract. This is in contrast to the rabbit where CYP1A1 protein was readily detectable on immunoblots in microsomes prepared from the small intestine. In humans, CYP3A3/3A4 expression was detectable in the esophagus and all segments of the small intestine. Northern blot analysis of eleven human colons showed considerable heterogeneity in CYP3A mRNA between individuals, with the presence of two mRNA species in some subjects. Employing the technique of hybridization histochemistry (also known as in situ hybridization), CYP4B1 expression was observed in some human colons but not in the liver or the small intestine. Hybridization histochemistry studies have also demonstrated variable NAT1 and NAT2 expression in the human gastrointestinal tract. NAT1 and NAT2 mRNA expression was detected in the human liver, small intestine, colon, esophagus, bladder, ureter, stomach and lung. Using a general aryl sulfotransferase riboprobe (HAST1), we have demonstrated marked sulfotransferase expression in the human colon, small intestine, lung, stomach and liver. These studies demonstrate that considerable variability exists in the expression of enzymes involved in the activation of aromatic amines in human tissues. The significance of these results in relation to a role for heterocyclic amines in colon cancer is discussed.

A High-Resolution 3D Separated-Local-Field Experiment by Means of Magic-Angle Turning

A 3D separated-local-field (SLF) experiment based on the 2D PHORMAT technique is described. In the 3D experiment, the conventional 2D SLF powder pattern for each chemically inequivalent carbon is separated according to their different isotropic chemical shifts. The dipolar coupling constant of a C-H pair, hence the bond distance, and the relative orientation of the chemical-shift tensor to the C-H vector can all be determined for the protonated carbons with a single measurement. As the sample turns at only about 30 Hz in a MAT experiment, the SLF patterns obtained approach those of a stationary sample, and an accuracy in the measurement similar to that obtained on a stationary sample is expected. The technique is demonstrated on 2,6-dimethoxynaphthalene, where the 13 C-1 H separated-local-field powder patterns for the six chemically inequivalent carbons are clearly identified and measured. The observed dipolar coupling for the methoxy carbon is effectively reduced by the fast rotation of the group about its C3 symmetry axis. The average angle between the C-H bond direction and the C3 rotation axis in the OCH3 group is found to be about 66&deg;.

Post-1980 black population redistribution trends in the United States

"Using data from the 1990 Public Use Microdata Samples (PUMS) and other U.S. census documents, this paper demonstrates how three rather dramatic shifts in the migration behavior of blacks, which took shape during the 1970s, continued to contribute to the geographical redistribution of the black population down the urban hierarchy during the 1980s. Analyses of black migration flows into six metropolitan areas suggest that liberal welfare benefits play, at best, a minor role in contemporary black population redistribution trends, kinship ties (i.e., location-specific capital), the search for affordable housing, and employment in the hospitality services industry appear to be the dominant forces influencing black migration into the case-study communities."

Dynamic nuclear polarization of nitrogen-15 in benzamide

A 15N dynamic nuclear polarization (DNP) experiment is reported in which a 15N DNP enhancement factor of approximately 2.6 x 10(2) is obtained on free radical doped samples of 99% 15N labeled benzamide. The free radicals BDPA (1:1 complex of alpha, gamma-bisdiphenylene-beta-phenylallyl with benzene) and DPPH (2,2-Di(4-tert-octylphenyl)-1-picrylhydrazyl) are used as dopants and the spin relaxation effects of adding these dopants are studied by means of changes in proton and nitrogen T1 values of the samples. The combination in solids of a very low natural abundance, 0.37%, a small gyromagnetic ratio, and a long spin-lattice relaxation time for 15N nuclei create severe sensitivity problems that, in large part, are ameliorated by the signal enhancement observed in the 15N DNP experiment on samples containing free electrons.

Study of the role of the highly conserved residues Arg9 and Arg64 in the catalytic function of human N-acetyltransferases NAT1 and NAT2 by site-directed mutagenesis

The arylamine N-acetyltransferases (NATs) NAT1 and NAT2 are responsible for the biotransformation of many arylamine and hydroxylamine xenobiotics. It has been proposed that NATs may act through a cysteine-linked acetyl-enzyme intermediate in a general base catalysis involving a highly conserved arginine residue such as Arg64. To investigate this possibility, we used site-directed mutagenesis and expression of recombinant human NAT1 and NAT2 in Escherichia coli. Sequence comparison with NATs from other species indicated that Arg9 and Arg64 are the only invariant basic residues. Either mutation of the presumed catalytic Cys68 residue or the simultaneous mutation of Arg9 and Arg64 to Ala produced proteins with undetectable enzyme activity. NAT1 or NAT2 singly substituted at Arg9 or Arg64 with Ala, Met, Gln or Lys exhibited unaltered Km values for arylamine acceptor substrates, but a marked loss of activity and stability. Finally, double replacement of Arg9/Arg64 with lysine in NAT1 altered the Km for arylamine substrates (decreased by 8-14-fold) and for acetyl-CoA (elevated 5-fold), and modified the pH-dependence of activity. Thus, through their positively charged side chains, Arg9 and Arg64 seem to contribute to the conformational stability of NAT1 and NAT2 rather than acting as general base catalysts. Our results also support a mechanism in which Arg9 and Arg64 are involved in substrate binding and transition-state stabilization of NAT1.

Cloning, structural organization, and chromosomal mapping of the human phenol sulfotransferase STP2 gene

Phenol- and monoamine-metabolizing sulfotransferases (STP and STM, respectively) are members of a superfamily of enzymes that add sulfate to a variety of xenobiotics and endobiotics containing hydroxyl or amino functional groups. To characterize related sulfotransferase genes further, we used extra-long PCR (XL-PCR) to generate three distinct sizes of amplification products from human genomic DNA or from genomic phage library clones, each of which contained sulfotransferase gene sequences. One of the PCR fragments contained a new sulfotransferase gene, STP2, corresponding to a recently published cDNA clone that encodes a sulfotransferase with catalytic specificity distinct from that of the previously described STP1 and STM. Additional upstream sequence information was obtained using a second STP2-specific XL-PCR-based approach. The STP2 gene is composed of eight exons and seven introns, with exon sizes ranging from 95 to 181 bp. Protein-coding exon lengths and locations of the splice junctions were identical to those in both the STM gene and an STP2 gene published independently by another group recently. The STP2 gene maps to a chromosomal location (16p11.2-p12) that is the same as that previously determined for both STP1 and STM. The characterization of the STP2 gene provides further insight into the organization, regulation, and multiplicity of the sulfotransferase supergene family.

Comparison of valaciclovir and acyclovir for the treatment of herpes zoster in immunocompetent patients over 50 years of age: a cost-consequence model

A method was developed for modeling the costs and consequences of treating varicella zoster viral infections to clinical data generated in a pivotal phase III clinical trial of valaciclovir versus acyclovir for the treatment of acute herpes zoster in immunocompetent patients over 50 years of age. Direct medical costs and indirect costs (productivity losses) were modeled using unit costs applicable in the United States. Compared with acyclovir, valaciclovir reduced average direct medical costs per patient by 17% ($60.01) and indirect costs by an average of 25% ($46.54). Median duration of pain was reduced by 13 days for valaciclovir compared with acyclovir in the intent-to-treat population or by 19 days in patients with pain after rash healing. The cost variables described in the model (drug costs, cost of treating long-term pain, physician visits, hospitalization, treatment of severe ocular involvement, productivity losses) were tested by sensitivity analysis. Total costs associated with valaciclovir treatment remained lower than those with acyclovir over the range of the analysis.

Genotyping of the polymorphic N-acetyltransferase (NAT2*) gene locus in two native African populations

The hepatic N-acetyltransferase enzyme encoded by the NAT2* gene locus is responsible for the human polymorphic acetylation of numerous arylamine or hydrazine-containing drugs and xenobiotics including AIDS-related therapeutic agents such as isoniazid and sulphonamides. The genetic basis underlying the human acetylation polymorphism has been extensively studied in several populations but native African populations were poorly documented. In the present study, 117 unrelated black Africans, namely Dogons from Mali and Gabonese, were investigated for NAT2* allelic variability and genotype distribution. Thirteen NAT2* alleles were unambiguously identified by combined use of allele-specific reamplifications and restriction endonuclease digestions. Our results confirm the African origin of G191->A substitution in the NAT2* coding region which was previously associated with slow acetylation in African-Americans. The finding of high allelic diversity in the studied populations is consistent with the hypothesis of a single African origin for NAT2*-associated polymorphism. Finally, no excess of the slow acetylator phenotype is predicted in these populations, implying no need for fitting NAT2* polymorphism-sensitive therapies to black Africans, compared to Caucasians.

Covalent binding of sulfamethoxazole reactive metabolites to human and rat liver subcellular fractions assessed by immunochemical detection

Potentially serious idiosyncratic reactions associated with sulfamethoxazole (SMX) include systemic hypersensitivity reactions and hepatotoxicity. Covalent binding of SMX to proteins subsequent to its N-hydroxylation to form N4-hydroxysulfamethoxazole (SMX-HA) is thought to be involved in the pathogenesis of these reactions. A polyclonal antibody was elicited in rabbits against a SMX--keyhole limpet hemocyanin conjugate that recognized covalent protein adducts of SMX in microsomal protein and was used to characterize the covalent binding of SMX and its putative reactive metabolites to hepatic protein in vivo and in vitro. In vitro covalent binding of SMX to rat and human liver microsomal protein was NADPH-dependent, while binding of SMX-HA was not dependent on NADPH. SMX and SMX-HA produced similar patterns of covalent binding, with major protein targets in the region of 150, 100 (two bands), 70 (two bands), and 45-55 kDa. The pattern of covalent binding to human and rat liver microsomal protein was similar. Binding of SMX-HA was completely eliminated by GSH or by addition of cytosolic fractions and acetylcoenzyme A. The acetoxy metabolite of SMX also led to covalent binding, but it was primarily attributable to the formation of SMX-HA from acetoxySMX. In vivo exposure of rats to SMX did not result in detectable covalent binding by the methods employed. When rat liver slices were incubated with 2 mM SMX or 500 microM SMX-HA, no toxicity was observed and yet covalent binding of SMX-HA to 130, 100, 70, and 55 kDa proteins could be detected. These results confirm that covalent binding of SMX occurs via the formation of SMX-HA and that covalent binding of SMX-HA in vitro results from its conversion to the more reactive nitroso metabolite. Acetylation of SMX-HA protected against its covalent binding. Further studies are required to determine how this in vitro covalent binding relates to in vivo covalent binding in humans and to either direct or immune-mediated cytotoxicity in SMX idiosyncratic drug reactions.