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1.
Sci Rep ; 12(1): 7468, 2022 05 06.
Article in English | MEDLINE | ID: mdl-35523824

ABSTRACT

Late'iki (previously known as Metis Shoal) is a highly active volcano in the Tofua arc with at least four temporary island-building eruptions and one submarine eruption in the last 55 years. The most recent eruption, commencing in October 2019, resulted in lava effusion and subsequent phreatic explosions, the construction of a short-lived island that was quickly eroded by wave action and possibly further phreatic activity that continued into January 2020. The two-pyroxene dacite from the 2019 eruption is similar to the 1967/8 eruptions suggesting the magma is residual from earlier eruptions and has not undergone further differentiation in the last 50 years. New observations of the 2019 eruption site confirm the lava-dominant character of the volcano summit but a thin veneer of wave-reworked, finely fragmented lava material remains that is interpreted to have been produced by phreatic explosions from hot rock-water interactions during the effusive eruption. A notable absence of quench-fragmented hyaloclastite breccias suggests that non-explosive quench fragmentation processes were minimal at these shallow depths or that hyaloclastite debris has resedimented to greater depths beyond our summit survey area.


Subject(s)
Disasters , Volcanic Eruptions , Minerals , Tonga
3.
J Psychiatr Ment Health Nurs ; 20(3): 228-35, 2013 Apr.
Article in English | MEDLINE | ID: mdl-22632655

ABSTRACT

The early years of the 21st century have seen successful efforts in a number of countries to reduce the use of restraint in services for people with mental health problems. An underlying emphasis on 'cultural change' is characteristic of such initiatives reflecting, it appears, the re-emergence of interest in the therapeutic milieu. Such efforts have though lacked a comprehensive explanation of how organizational culture plays a role in the development of the excessive use of restraint, which seems to respond to such initiatives. This paper seeks to address that deficit and draws in particular on the concepts of corrupted culture, institutional violence, trauma, parallel processing and contemporary research on restraint and seclusion reduction. In doing so it examines whether restraint reduction initiatives represent part of the solution to the problem of corruption, which is intrinsically associated with the legitimatization of coercion.


Subject(s)
Hospitals, Psychiatric/ethics , Inpatients/psychology , Mental Disorders/nursing , Mental Disorders/psychology , Restraint, Physical/ethics , Restraint, Physical/psychology , Coercion , Humans , Organizational Culture
4.
Scott Med J ; 56(3): 164-6, 2011 Aug.
Article in English | MEDLINE | ID: mdl-21873723

ABSTRACT

A highly contagious behavioural affliction is now endemic in highland areas of Scotland. Pretravel advice ought to include a health warning to sport-lovers venturing north into wild, highlands of Gaeldom. It particularly affects young adults and predominates in men, although women are affected. The disorder can be acute or chronic and when severe, it can threaten one's life and limbs. Acute attacks may bring spontaneous recovery in months, but the chronic state can last for a life-time. Death will overtake some before it runs its inevitable course.


Subject(s)
Mountaineering/psychology , Humans , Mountaineering/injuries , Mountaineering/statistics & numerical data , Scotland
5.
Hum Genet ; 120(4): 501-18, 2006 Nov.
Article in English | MEDLINE | ID: mdl-16953426

ABSTRACT

Isolated oral clefts, including cleft lip with/without cleft palate (CL/P) and cleft palate (CP), have a complex and heterogeneous etiology. Case-parent trios from three populations were used to study genes spanning chromosome 2, where single nucleotide polymorphic (SNP) markers were analyzed individually and as haplotypes. Case-parent trios from three populations (74 from Maryland, 64 from Singapore and 95 from Taiwan) were genotyped for 962 SNPs in 104 genes on chromosome 2, including two well-recognized candidate genes: TGFA and SATB2. Individual SNPs and haplotypes (in sliding windows of 2-5 SNPs) were used to test for linkage and disequilibrium separately in CL/P and CP trios. A novel candidate gene (ZNF533) showed consistent evidence of linkage and disequilibrium in all three populations for both CL/P and CP. SNPs in key regions of ZNF533 showed considerable variability in estimated genotypic odds ratios and their significance, suggesting allelic heterogeneity. Haplotype frequencies for regions of ZNF533 were estimated and used to partition genetic variance into among-and within-population components. Wright's fixation index, a measure of genetic diversity, showed little difference between Singapore and Taiwan compared with Maryland. The tensin-1 gene (TNS1) also showed evidence of linkage and disequilibrium among both CL/P and CP trios in all three populations, albeit at a lower level of significance. Additional genes (VAX2, GLI2, ZHFX1B on 2p; WNT6-WNT10A and COL4A3-COL4A4 on 2q) showed consistent evidence of linkage and disequilibrium only among CL/P trios in all three populations, and TGFA showed significant evidence in two of three populations.


Subject(s)
Chromosomes, Human, Pair 2 , Cleft Lip/genetics , Cleft Palate/genetics , Genetic Predisposition to Disease , Polymorphism, Single Nucleotide , Chromosome Mapping , Family Health , Female , Gene Frequency , Genetic Linkage , Genotype , Haplotypes , Humans , Linkage Disequilibrium , Male , Maryland , Multivariate Analysis , Nuclear Family , Singapore , Taiwan
6.
J Med Genet ; 43(7): 598-608, 2006 Jul.
Article in English | MEDLINE | ID: mdl-16415175

ABSTRACT

BACKGROUND: Recent work suggests that multiple genes and several environmental risk factors influence risk for non-syndromic oral clefts, one of the most common birth defects in humans. Advances in high-throughput genotyping technology now make it possible to test multiple markers in many candidate genes simultaneously. METHODS: We present findings from family based association tests of single nucleotide polymorphism (SNP) markers in 64 candidate genes genotyped using the BeadArray approach in 58 case-parent trios from Maryland (USA) to illustrate how multiple markers in multiple genes can be analysed. To assess whether these genes were expressed in human craniofacial structures relevant to palate and lip development, we also analysed data from the Craniofacial and Oral Gene Expression Network (COGENE) consortium, and searched public databases for expression profiles of these genes. RESULTS: Thirteen candidate genes showed significant evidence of linkage in the presence of disequilibrium, and ten of these were found to be expressed in relevant embryonic tissues: SP100, MLPH, HDAC4, LEF1, C6orf105, CD44, ALX4, ZNF202, CRHR1, and MAPT. Three other genes showing statistical evidence (ADH1C, SCN3B, and IMP5) were not expressed in the embryonic tissues examined here. CONCLUSIONS: This approach demonstrates how statistical evidence on large numbers of SNP markers typed in case-parent trios can be combined with expression data to identify candidate genes for complex disorders. Many of the genes reported here have not been previously studied as candidates for oral clefts and warrant further investigation.


Subject(s)
Cleft Lip/genetics , Cleft Palate/genetics , Mouth Abnormalities/genetics , Polymorphism, Single Nucleotide , Chromosome Mapping/methods , Craniofacial Abnormalities/genetics , DNA/genetics , DNA/isolation & purification , Humans , Linkage Disequilibrium , Maryland , Oligonucleotide Array Sequence Analysis , Reference Values
7.
Ann Hum Genet ; 69(Pt 4): 349-63, 2005 Jul.
Article in English | MEDLINE | ID: mdl-15996164

ABSTRACT

Nail Patella Syndrome (NPS; OMIM #161200) is a pleiotropic condition, with a classical clinical tetrad of involvement of the nails, knees, elbows and the presence of iliac horns. Kidney disease and glaucoma are now recognised as part of the syndrome. Fifty years ago, James Renwick chose NPS to develop methods of linkage analysis in humans and revealed the third linkage group identified in man--that between NPS and the ABO blood group loci. After a fallow period of some forty years, the gene mutated in NPS has been identified (LMX1B) and the condition serves as a model for understanding the complex relationships between disease loci, modifier genes and the resultant clinical phenotype.


Subject(s)
ABO Blood-Group System/history , Genetic Linkage , Nail-Patella Syndrome/history , ABO Blood-Group System/genetics , Amino Acid Sequence , Animals , History, 20th Century , History, 21st Century , Humans , Molecular Sequence Data , Nail-Patella Syndrome/genetics
8.
Genetics ; 171(1): 259-67, 2005 Sep.
Article in English | MEDLINE | ID: mdl-15965248

ABSTRACT

Analysis of haplotypes based on multiple single-nucleotide polymorphisms (SNP) is becoming common for both candidate gene and fine-mapping studies. Before embarking on studies of haplotypes from genetically distinct populations, however, it is important to consider variation both in linkage disequilibrium (LD) and in haplotype frequencies within and across populations, as both vary. Such diversity will influence the choice of "tagging" SNPs for candidate gene or whole-genome association studies because some markers will not be polymorphic in all samples and some haplotypes will be poorly represented or completely absent. Here we analyze 11 genes, originally chosen as candidate genes for oral clefts, where multiple markers were genotyped on individuals from four populations. Estimated haplotype frequencies, measures of pairwise LD, and genetic diversity were computed for 135 European-Americans, 57 Chinese-Singaporeans, 45 Malay-Singaporeans, and 46 Indian-Singaporeans. Patterns of pairwise LD were compared across these four populations and haplotype frequencies were used to assess genetic variation. Although these populations are fairly similar in allele frequencies and overall patterns of LD, both haplotype frequencies and genetic diversity varied significantly across populations. Such haplotype diversity has implications for designing studies of association involving samples from genetically distinct populations.


Subject(s)
Asian People/genetics , Genetic Predisposition to Disease/ethnology , Haplotypes/genetics , Polymorphism, Single Nucleotide , White People/genetics , Analysis of Variance , Cleft Lip/ethnology , Cleft Lip/genetics , Cleft Palate/ethnology , Cleft Palate/genetics , Female , Gene Frequency , Genetic Variation/genetics , Humans , India/ethnology , Linkage Disequilibrium , Malaysia/ethnology , Male , Maryland , Singapore , Taiwan/ethnology
9.
Ann Hum Genet ; 69(Pt 1): 1-8, 2005 Jan.
Article in English | MEDLINE | ID: mdl-15638822

ABSTRACT

The genetic bases underlying the range and severity of phenotypes in Mendelian disorders is poorly understood; however, improvements in this area have the potential to facilitate analysis of oligogenic disorders. The nail dysplasia observed in Nail Patella Syndrome (NPS) was selected as a quantifiable variable within a Mendelian disorder, for which data could be readily obtained, to allow investigation of the genetic basis of variation. Analysis of SNP haplotypes across the LMX1B gene demonstrated association between the haplotype of the mutant allele and the variability in the nail score (p = 0.024). These results are in contrast to those obtained previously, which supported a modifying role for the wild-type allele. Since there is no evidence that particular mutations, or classes of mutation, are associated with the variation (p > 0.5), further work is required to identify the elements associated with the LMX1B gene that mediate phenotypic severity.


Subject(s)
Genetic Variation , Haplotypes/genetics , Homeodomain Proteins/genetics , Nail-Patella Syndrome/genetics , Nails, Malformed , Polymorphism, Single Nucleotide/genetics , DNA Mutational Analysis , Female , Genetic Linkage , Genotype , Humans , LIM-Homeodomain Proteins , Male , Mutation , Phenotype , Transcription Factors
10.
J Med Genet ; 40(3): 153-62, 2003 Mar.
Article in English | MEDLINE | ID: mdl-12624132

ABSTRACT

Nail patella syndrome (NPS) is an autosomal dominant condition affecting the nails, skeletal system, kidneys, and eyes. Skeletal features include absent or hypoplastic patellae, patella dislocations, elbow abnormalities, talipes, and iliac horns on x ray. Kidney involvement may lead to renal failure and there is also a risk of glaucoma. There is marked inter- and intrafamilial variability. The results of a British study involving 123 NPS patients are compared with previously published studies and it is suggested that neurological and vasomotor symptoms are also part of the NPS phenotype. In addition, the first data on the incidence of glaucoma and gastrointestinal (GI) symptoms in NPS are presented. NPS is caused by loss of function mutations in the transcription factor LMX1B at 9q34. The expansion of the clinical phenotype is supported by the role of LMX1B during development.


Subject(s)
Nail-Patella Syndrome/genetics , Nail-Patella Syndrome/pathology , Adolescent , Adult , Age Factors , Aged , Aged, 80 and over , Ankle Joint/abnormalities , Ankle Joint/physiopathology , Back Pain/pathology , Child , Child, Preschool , Elbow/abnormalities , Elbow/physiopathology , Family Health , Female , Finger Joint/abnormalities , Finger Joint/physiopathology , Homeodomain Proteins/genetics , Humans , Infant , Knee Joint/abnormalities , Knee Joint/physiopathology , LIM-Homeodomain Proteins , Male , Middle Aged , Movement/physiology , Mutation , Nails, Malformed , Phenotype , Transcription Factors
11.
Vertex ; 13(49): 177-81, 2002.
Article in Spanish | MEDLINE | ID: mdl-12404018

ABSTRACT

Elderly adults are appropriate targets for objective memory assessment and cognitive testing in the promotion of earlier recognition of people with symptoms of a dementing process. The major change in memory with age is the decline in ability to recall things explicitly. There is a need for education of the general public and health professionals about memory impairment and its relationship with stress, depression, anxiety and dementia.


Subject(s)
Memory Disorders/epidemiology , Adult , Aged , Aged, 80 and over , Cohort Studies , Humans , Memory Disorders/diagnosis , Memory Disorders/etiology , Middle Aged , Pilot Projects , Severity of Illness Index , Stress, Psychological/psychology , Surveys and Questionnaires
12.
Genet Epidemiol ; 22(1): 1-11, 2002 Jan.
Article in English | MEDLINE | ID: mdl-11754469

ABSTRACT

Markers in five candidate genes were examined on 269 case-parent trios ascertained through a child with an isolated, non-syndromic oral cleft (cleft lip, CL; cleft palate, CP; or cleft lip and palate, CLP). Cases and their parents were ascertained through treatment centers in Maryland. Markers at two of the five candidate genes, transforming growth factor beta3 (TGFbeta3) and MSX1, showed consistent evidence of linkage and disequilibrium due to linkage using several statistical tests (e.g., the global chi-square for TGFbeta3 was 21.1 with 12 df, P = 0.03; that for MSX1 was 8.7 with 3 df, P = 0.03). There was little evidence of heterogeneity in the role of TGFbeta3 between different types of oral clefts, but MSX1 did yield marginal evidence for such heterogeneity. MSX1 also showed evidence for interaction between infant's genotype and maternal smoking, giving a likelihood ratio test for heterogeneity between smoker and non-smoker mothers of 7.16 (2 df, P = 0.03). Using a conditional logistic model to test for gene-gene interaction showed no evidence of interaction between TGFbeta3 and MSX1, with both seeming to contribute independently to risk of isolated, non-syndromic oral clefts.


Subject(s)
Cleft Lip/genetics , Cleft Palate/genetics , Linkage Disequilibrium , Transcription Factors , Adult , Alleles , Case-Control Studies , Chi-Square Distribution , Cleft Lip/epidemiology , Cleft Palate/epidemiology , Female , Genetic Markers , Genotype , Homeodomain Proteins/genetics , Humans , Infant , Infant, Newborn , Logistic Models , MSX1 Transcription Factor , Male , Maryland/epidemiology , Nuclear Family , Research Design , Transforming Growth Factor beta/genetics
13.
Vertex rev. argent. psiquiatr ; 13(49): 177-81, 2002 Sep-Nov.
Article in Spanish | LILACS-Express | BINACIS | ID: biblio-1176671

ABSTRACT

Elderly adults are appropriate targets for objective memory assessment and cognitive testing in the promotion of earlier recognition of people with symptoms of a dementing process. The major change in memory with age is the decline in ability to recall things explicitly. There is a need for education of the general public and health professionals about memory impairment and its relationship with stress, depression, anxiety and dementia.

14.
Vertex ; 13(49): 177-81, 2002 Sep-Nov.
Article in Spanish | BINACIS | ID: bin-39128

ABSTRACT

Elderly adults are appropriate targets for objective memory assessment and cognitive testing in the promotion of earlier recognition of people with symptoms of a dementing process. The major change in memory with age is the decline in ability to recall things explicitly. There is a need for education of the general public and health professionals about memory impairment and its relationship with stress, depression, anxiety and dementia.

15.
Hum Mutat ; 18(5): 458, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11668639

ABSTRACT

We report twenty-two novel mutations in the gene encoding the transcription factor LMX1B, previously shown to be mutated in persons with Nail Patella Syndrome (NPS). The mutations comprised eight missense, one splice-site, three insertion/deletion and ten nonsense or frameshift mutations. A sub-set of five recurrent mutations within the homeodomain represents over one-quarter of the described NPS mutations. The type and distribution of the mutations is consistent with the hypothesis that NPS is the result of haploinsufficiency for LMX1B.


Subject(s)
Homeodomain Proteins/genetics , Mutation/genetics , Nail-Patella Syndrome/genetics , Codon, Nonsense/genetics , DNA Mutational Analysis , Frameshift Mutation/genetics , Homeodomain Proteins/chemistry , Humans , LIM-Homeodomain Proteins , Mutation, Missense/genetics , Protein Structure, Tertiary , Transcription Factors
16.
Am J Hum Genet ; 69(5): 951-60, 2001 Nov.
Article in English | MEDLINE | ID: mdl-11555794

ABSTRACT

X inactivation is the mammalian method for X-chromosome dosage compensation, but some features of this developmental process vary among mammals. Such species variations provide insights into the essential components of the pathway. Tsix encodes a transcript antisense to the murine Xist transcript and is expressed in the mouse embryo only during the initial stages of X inactivation; it has been shown to play a role in imprinted X inactivation in the mouse placenta. We have identified its counterpart within the human X inactivation center (XIC). Human TSIX produces a >30-kb transcript that is expressed only in cells of fetal origin; it is expressed from human XIC transgenes in mouse embryonic stem cells and from human embryoid-body-derived cells, but not from human adult somatic cells. Differences in the structure of human and murine genes indicate that human TSIX was truncated during evolution. These differences could explain the fact that X inactivation is not imprinted in human placenta, and they raise questions about the role of TSIX in random X inactivation.


Subject(s)
Dosage Compensation, Genetic , RNA, Antisense/genetics , RNA, Untranslated/genetics , Transcription Factors/genetics , Aging/genetics , Animals , Cell Line , Embryo, Mammalian/metabolism , Evolution, Molecular , Fetus/metabolism , Genomic Imprinting/genetics , Humans , Mice , Molecular Sequence Data , Open Reading Frames/genetics , Placenta/metabolism , RNA, Antisense/analysis , RNA, Antisense/biosynthesis , RNA, Antisense/isolation & purification , RNA, Long Noncoding , RNA, Untranslated/analysis , RNA, Untranslated/biosynthesis , RNA, Untranslated/isolation & purification , Sequence Deletion/genetics , Sequence Homology, Nucleic Acid , Species Specificity , Stem Cells/metabolism , Transcription Initiation Site , Transcription, Genetic , Transgenes/genetics
17.
Ann Epidemiol ; 11(6): 434-42, 2001 Aug.
Article in English | MEDLINE | ID: mdl-11454503

ABSTRACT

PURPOSE: Isolated, nonsyndromic oral clefts cases (n = 171) and unaffected controls (n = 182) were used to identify both genetic and environmental risk factors. METHODS: Infants born in Maryland between 1992 to 1998 with an isolated, nonsyndromic oral cleft [cleft lip (CL), cleft lip and palate (CLP), or cleft palate (CP)] were recruited and exposure plus family history data were collected. Controls were unaffected infants. DNA was collected from all cases and their parents, plus controls. RESULTS: No statistically significant association was found between any of the following: maternal smoking, vitamin use, urinary tract infection, or recreational drug use in either univariate analysis or after adjusting for maternal age and education. More control mothers reported alcohol use during the critical time period of pregnancy (one month before conception through the first trimester) as compared to case mothers. There was a 10-fold increase in risk to siblings of cases as compared to siblings of controls. Markers at four candidate genes were examined: transforming growth factor alpha (TGF alpha), transforming growth factor beta 3 (TGF beta 3), MSX1, and BCL3. Only MSX1 showed significant differences in allele frequencies between CP cases and controls. MSX1 also showed significant evidence of linkage disequilibrium with a susceptibility gene controlling risk for CP. CONCLUSION: Most environmental risk factors examined here gave little evidence of association with risk to isolated, nonsyndromic oral clefts, although any alcohol consumption seemed protective. MSX1 showed evidence of linkage disequilibrium in both case-control and case-parent trio analysis.


Subject(s)
Cleft Lip/epidemiology , Cleft Palate/epidemiology , Case-Control Studies , Chi-Square Distribution , Cleft Lip/etiology , Cleft Lip/genetics , Cleft Palate/etiology , Cleft Palate/genetics , Genotype , Humans , Infant, Newborn , Logistic Models , Maryland/epidemiology , Monte Carlo Method , Risk Factors
18.
Drug Metab Dispos ; 29(6): 813-20, 2001 Jun.
Article in English | MEDLINE | ID: mdl-11353749

ABSTRACT

Etoricoxib, a potent and selective cyclooxygenase-2 inhibitor, was shown to be metabolized via 6'-methylhydroxylation (M2 formation) when incubated with NADPH-fortified human liver microsomes. In agreement with in vivo data, 1'-N'-oxidation was a relatively minor pathway. Over the etoricoxib concentration range studied (1-1300 microM), the rate of hydroxylation conformed to saturable Michaelis-Menten kinetics (apparent K(m) = 186 +/- 84.3 microM; V(max) = 0.76 +/- 0.45 nmol/min/mg of protein; mean +/- S.D., n = 3 livers) and yielded a V(max)/K(m) ratio of 2.4 to 7.3 microl/min/mg. This in vitro V(max)/K(m) ratio was scaled, with respect to yield of liver microsomal protein and liver weight, to obtain estimates of M2 formation clearance (3.1-9.7 ml/min/kg of b.wt.) that agreed favorably with in vivo results (8.3 ml/min/kg of b.wt.) following i.v. administration of [(14)C]etoricoxib to healthy male subjects. Cytochrome P450 (P450) reaction phenotyping studies-using P450 form selective chemical inhibitors, immunoinhibitory antibodies, recombinant P450s, and correlation analysis with microsomes prepared from a bank of human livers-revealed that the 6'-methyl hydroxylation of etoricoxib was catalyzed largely (approximately 60%) by member(s) of the CYP3A subfamily. By comparison, CYP2C9 (approximately 10%), CYP2D6 (approximately 10%), CYP1A2 (approximately 10%), and possibly CYP2C19 played an ancillary role. Moreover, etoricoxib (0.1-100 microM) was found to be a relatively weak inhibitor (IC(50) > 100 microM) of multiple P450s (CYP1A2, CYP2D6, CYP3A, CYP2E1, CYP2C9, and CYP2C19) in human liver microsomes.


Subject(s)
Cyclooxygenase Inhibitors/pharmacokinetics , Cytochrome P-450 Enzyme System/metabolism , Isoenzymes/metabolism , Microsomes, Liver/enzymology , Pyridines/pharmacokinetics , Sulfones/pharmacokinetics , Animals , Cell Line , Cyclooxygenase 2 , Cyclooxygenase 2 Inhibitors , Cytochrome P-450 Enzyme Inhibitors , DNA, Complementary , Etoricoxib , Humans , Isoenzymes/antagonists & inhibitors , Isoenzymes/drug effects , Male , Membrane Proteins , Prostaglandin-Endoperoxide Synthases/drug effects
19.
J Travel Med ; 8(2): 60-5, 2001.
Article in English | MEDLINE | ID: mdl-11285164

ABSTRACT

BACKGROUND: Travelers' diarrhea is the most frequent health problem in those participating in international journeys, and is responsible for many consultations abroad and on return home. METHODS: A questionnaire assessing attitudes toward treatment and management of travel-related and nontravel-related diarrhea was administered to 542 GPs, nurses and pharmacists. RESULTS: Health professionals' attitudes to management of acute diarrhea are variable, with marked divergence regarding adherence to published "good practice" guidelines and recommendations. Inconsistencies exist in stated attitudes toward prescribing antispasmodics and antimotility agents and actual prescribing behavior. CONCLUSIONS: Current treatment guidelines may be outdated. Inappropriate or delayed treatment disadvantages the patient. Limiting the use of antidiarrheal agents can deny access, for those inflicted with diarrhea, to a medication which may shorten symptomatology and morbidity, and speed the return to normality. Review of guidelines for diarrhea management in adults is overdue, as is standardization of treatment response. Educational initiatives are required to encourage active intervention and improved provision of care.


Subject(s)
Attitude of Health Personnel , Diarrhea/prevention & control , Practice Patterns, Physicians' , Travel , Acute Disease , Antidiarrheals/therapeutic use , England , Humans , Practice Guidelines as Topic , Surveys and Questionnaires
20.
Chem Res Toxicol ; 14(1): 62-70, 2001 Jan.
Article in English | MEDLINE | ID: mdl-11170509

ABSTRACT

Therapy with the oral antidiabetic agent troglitazone (Rezulin) has been associated with cases of severe hepatotoxicity and drug-induced liver failure, which led to the recent withdrawal of the product from the U.S. market. While the mechanism of this toxicity remains unknown, it is possible that chemically reactive metabolites of the drug play a causative role. In an effort to address this possibility, this study was undertaken to determine whether troglitazone undergoes metabolism in human liver microsomal preparations to electrophilic intermediates. Following incubation of troglitazone with human liver microsomes and with cDNA-expressed cytochrome P450 isoforms in the presence of glutathione (GSH), a total of five GSH conjugates (M1-M5) were detected and identified tentatively by LC-MS/MS analysis. In two cases (M1 and M5), the structures of the adducts were confirmed by NMR spectroscopy and/or by comparison with an authentic standard prepared by synthesis. The formation of GSH conjugates M1-M5 revealed the operation of two distinct metabolic activation pathways for troglitazone, one of which involves oxidation of the substituted chromane ring system to a reactive o-quinone methide derivative, while the second involves a novel oxidative cleavage of the thiazolidinedione (TZD) ring, potentially generating highly electrophilic alpha-ketoisocyanate and sulfenic acid intermediates. When troglitazone was administered orally to a rat, samples of bile were found to contain GSH conjugates which reflected the operation of these same metabolic pathways in vivo. The finding that metabolism of the TZD ring of troglitazone was catalyzed selectively by P450 3A enzymes is significant in light of the recent report that troglitazone is an inducer of this isoform in human hepatocytes. The implications of these results are discussed in the context of the potential for troglitazone to covalently modify hepatic proteins and to cause oxidative stress through redox cycling processes, either of which may play a role in drug-induced liver injury.


Subject(s)
Chromans/pharmacokinetics , Hypoglycemic Agents/pharmacokinetics , Thiazoles/pharmacokinetics , Thiazolidinediones , Animals , Bile/metabolism , Biotransformation , Catalysis , Chromans/metabolism , Chromans/toxicity , Chromatography, Liquid , Cytochrome P-450 Enzyme Inhibitors , Cytochrome P-450 Enzyme System/metabolism , Glutathione/metabolism , Glutathione/pharmacology , Humans , Hypoglycemic Agents/metabolism , Hypoglycemic Agents/toxicity , Isoenzymes/antagonists & inhibitors , Isoenzymes/metabolism , Ketoconazole/pharmacology , Kinetics , Mass Spectrometry , Microsomes, Liver/drug effects , Microsomes, Liver/enzymology , Microsomes, Liver/metabolism , NADP/metabolism , Rats , Steroid Hydroxylases/antagonists & inhibitors , Steroid Hydroxylases/metabolism , Thiazoles/metabolism , Thiazoles/toxicity , Troglitazone
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