Comparison of temperature readings using infrared thermometers at three different sites: tympanic, forehead and temporal

The aim of this study was to compare the body temperature measurements at tympanic, forehead and temporal sites using infrared thermometers. A total of 1576 consecutive visitors to Singapore General Hospital at two entry locations were included in this study. Pearson correlation and Bland–Altman mean difference between sites (95% confidence interval for limits of agreement) were calculated for the relationship between the three different sites of temperatures recorded (i.e. temporal, forehead and tympanic). Of all the visitors, 27 (1.7%) had fever. Moderate positive correlation was found between temporal and forehead temperature readings ( r=0.602, mean difference (temporal – forehead), (95% limits of agreement) = 0.1 (−0.8, 0.7)), and there was very weak positive correlation between tympanic and temporal temperature readings ( r=0.177, mean difference (temporal – tympanic), (95% limits of agreement) = −0.3 (−1.7, 1.1)). Sensitivity for temporal temperature readings (⩾37.5°C) to detect febrile visitors was 3.7%, specificity was 99.6%, positive predictive value was 14.3% and negative predictive value was 98.3%. Our results demonstrate that tympanic temperature readings should be used for fever screening instead of temporal or forehead readings.

Arylamine N-acetyltransferases: from drug metabolism and pharmacogenetics to drug discovery

Arylamine N-acetyltransferases (NATs) are polymorphic drug-metabolizing enzymes, acetylating arylamine carcinogens and drugs including hydralazine and sulphonamides. The slow NAT phenotype increases susceptibility to hydralazine and isoniazid toxicity and to occupational bladder cancer. The two polymorphic human NAT loci show linkage disequilibrium. All mammalian Nat genes have an intronless open reading frame and non-coding exons. The human gene products NAT1 and NAT2 have distinct substrate specificities: NAT2 acetylates hydralazine and human NAT1 acetylates p-aminosalicylate (p-AS) and the folate catabolite para-aminobenzoylglutamate (p-abaglu). Human NAT2 is mainly in liver and gut. Human NAT1 and its murine homologue are in many adult tissues and in early embryos. Human NAT1 is strongly expressed in oestrogen receptor-positive breast cancer and may contribute to folate and acetyl CoA homeostasis. NAT enzymes act through a catalytic triad of Cys, His and Asp with the architecture of the active site-modulating specificity. Polymorphisms may cause unfolded protein. The C-terminus helps bind acetyl CoA and differs among NATs including prokaryotic homologues. NAT in Salmonella typhimurium supports carcinogen activation and NAT in mycobacteria metabolizes isoniazid with polymorphism a minor factor in isoniazid resistance. Importantly, nat is in a gene cluster essential for Mycobacterium tuberculosis survival inside macrophages. NAT inhibitors are a starting point for novel anti-tuberculosis drugs. Human NAT1-specific inhibitors may act in biomarker detection in breast cancer and in cancer therapy. NAT inhibitors for co-administration with 5-aminosalicylate (5-AS) in inflammatory bowel disease has prompted ongoing investigations of azoreductases in gut bacteria which release 5-AS from prodrugs including balsalazide.

Arylarnine N-acetyltransferase as a potential biornarker in bladder cancer: fluorescent in situ hybridization and irnmunohistochernistry studies

Abstract Arylamine N-acetyltransferase isoenzymes NAT1 and NAT2 are encoded at two polymorphic loci on human chromosome 8p22. The two loci have previously been identified using chimeric Yeast Artificial Chromosome (YAC) clones encoding either NAT1 or NAT2 as probes for metaphase chromosomes using fluorescent in situ hybridization. The 8p22 region has been demonstrated to be deleted in highly invasive bladder tumours and since NAT isoenzymes participate in the metabolism of arylamine bladder carcinogens, it is important to determine whether NAT1 and NAT2 gene loci are included in the region of deletion. We describe here the application of a cosmid clone for NAT2 as a biomarker for Fluorescent In Situ Hybridization (FISH) on interphase nuclei of exfoliated bladder cells. We also describe a 70kb probe for NAT1 which is a candidate for a suitable biomarker for use in similar FISH studies. lmmunohistochemical staining of bladder tumour sections with a polyclonal anti-peptide antibody specific for the NATl isoenzyme as a biomarker for NAT1 protein expression is also shown.

Disease patterns of rheumatology outpatients seen in a tertiary hospital serving a multi-ethnic, urban Asian population in Singapore

AIMS

To describe the spectrum of diseases seen in an outpatient setting in the Singapore General Hospital, the largest tertiary referral centre in Singapore.

METHODS

In this cross-sectional study, medical records of patients scheduled for an appointment at the rheumatology specialist outpatient clinics over a 4-month period (10 August 2010-31 December 2010) were reviewed. Primary diagnoses documented by the attending physician at the latest visit were recorded.

RESULTS

Among 4180 patients (29.5% male; mean [SD] age: 53.5 [15.1] years; 77.0% Chinese, 8.0% Malay, 8.8% Indian and 6.2% others), the spectrum of diseases seen was as follows [disease - definite n (%), probable n (%)]: Arthritis: rheumatoid arthritis - 958 (22.9%), 68 (1.6%); osteoarthritis - 452 (10.8%), 39 (0.9%); crystal arthritis - 417 (10.0%), 18 (0.4%); spondyloarthritis - 227 (5.4%), 61 (1.5%); psoriatic arthritis - 158 (3.8%), 9 (0.2%); other inflammatory arthritis - 153 (3.7%), 94 (2.2%); Connective tissues diseases: systemic lupus erythematosus - 412 (9.9%), 26 (0.6%); vasculitis - 105 (2.5%), 22 (0.5%); Sjögren's syndrome - 81 (1.9%), 32 (0.8%); overlap syndromes - 73 (1.8%); scleroderma - 50 (1.2%), 4 (0.1%); undifferentiated connective tissue diseases - 45 (1.1%), 106 (2.5%); myositis - 41 (1.0%), 12 (0.3%); antiphospholipid syndrome - 22 (0.5%), 7 (0.2%); polymyalgia rheumatica - 16 (0.4%); Others: soft tissue rheumatism - 155 (3.7%); osteoporosis - 61 (1.5%); other non-rheumatologic conditions - 189 (4.5%); other rheumatologic conditions - 67 (1.6%).

CONCLUSION

Rheumatoid arthritis, osteoarthritis and crystal arthritis were the three most common rheumatological diseases seen in a tertiary referral centre serving a multi-ethnic urban Asian population in Singapore.

Dose-dependent systolic contribution of differentiated stem cells in post-infarct ventricular function

BACKGROUND

Differentiation of bone marrow stem cells toward cardiomyocytes has been widely reported in vitro. However, optimum cell types and mechanisms leading to functional improvement in cardiac cell therapy remain unresolved. There is limited evidence showing a dose-dependent effect of transplanted cells in contributing to functional recovery. This study showed that cell transplantation of differentiated cardiomyocyte-like cells (CLCs) and undifferentiated mesenchymal stem cells (MSCs) dose-dependently improved left ventricular function in a rat myocardial infarction model.

METHODS

At 1 week after infarction in Wistar rats, 1 × 10(6) MSCs (n = 9) or CLCs (n = 9) and 5 × 10(6) MSCs (n = 18) or CLCs (n = 15) were injected into peri-infarcted myocardium to study their effect after 6 weeks.

RESULTS

High-dose CLCs exhibited a dose-response that was significantly more effective than MSCs in recovering cardiac contractility. Superiority of CLCs over MSCs was demonstrated in load-independent measurement of the end-systolic pressure-volume relationship and pre-load recruitable stroke work, but not in the end-diastolic pressure-volume relationship. These findings showed a unique systolic role of CLCs in contractility recovery. Functional improvement mediated by MSCs was mainly derived from preservation of endogenous myocyte function and restriction of chamber dilatation by enhancing intramyocardial angiogenesis during post-infarct ventricular remodeling. Engrafted CLCs showed better survival, were strategically integrated into myofiber-associated collagen V matrix, and exhibited mature sarcomeric cross-striations. Vascular differentiation, but not cardiac, was observed with MSCs.

CONCLUSION

These cell type-specific effects suggest that committing stem cells to a cardiac phenotype ex vivo promoted mechanical and functional integration of CLCs into the myofibrillar syncytium of infarcted myocardium.

Differential effect of myocardial matrix and integrins on cardiac differentiation of human mesenchymal stem cells

Dysregulation of matrix synthesis during myocardial fibrosis in post-infarct ventricular remodeling contributes to ventricular dysfunction. Bone marrow stem cell transplantation prevents functional deterioration following myocardial infarction. However, effect of myocardial extracellular matrix (ECM) on stem cell differentiation is poorly understood. We investigate the role of collagen matrices and integrin system in cardiac differentiation and engraftment of stem cells in infarcted myocardium. Sternum-derived bone marrow mesenchymal stem cells (MSCs) were differentiated into cardiomyocyte-like cells (CLCs). They were characterized using RT-PCR, immunofluorescence, flow cytometry and functional integrin neutralization assays. CLCs were injected into peri-infarct borders of injured myocardium of Wistar rats one week following left anterior descending (LAD) artery ligation. Cardiac function was analyzed via pressure-volume relationships. Cardiac differentiated CLCs displayed collagen V specificity, which was absent in undifferentiated MSCs. Collagen V, but not collagen I matrix, promoted attachment, proliferation and cardiac differentiation of CLCs. In contrast to beta(1), alpha(v) integrin contributed minimally in the attachment of CLCs on collagen matrices. However, inhibition of alpha(v)beta(3,) but not alpha(2)beta(1) integrin, selectively attenuated troponin T, sarcomeric alpha-actin and ryanodine 2 receptor gene expression in CLCs. Both MSC and CLC transplantation prevented chamber dilatation and improved contractile function. However, systolic activity in MSC transplanted animals was accompanied by heightened wall stress as demonstrated by elevated myocardial end-diastolic pressure and prolonged tissue relaxation time. Localization of CLCs in the vicinity of collagen V-expressing myofibers promoted their integration into cardiac syncytium. CLCs may facilitate hemodynamic recovery by preserving tissue elasticity in the peri-infarct borders that sustains contractile efficiency for functional recovery in an actively remodeling infarcted myocardium.

Structure and Mechanism of Arylamine N-Acetyltransferases

Arylamine N-acetyltransferases (NATs) are a family of phase II drug-metabolising enzymes which are important in the biotransformation of various aromatic and heterocyclic amines and hydroxylamines, arylhydrazines and arylhydrazides. NATs are present in a wide range of eukaryotes and prokaryotes. Humans have two functional NAT isoforms, both of which are highly polymorphic. The pharmacogenetics of NATs is an area which has been extensively studied. The determination of the X-ray crystal structure of NAT from Salmonella typhimurium led to the identification of the catalytically essential triad of residues: Cys-His-Asp, which is present in all functional NAT enzymes. Recent co-crystallisation data and in silico docking studies of NAT from Mycobacterium smegmatis with substrates and inhibitors have aided the identification of important contact residues within the active site. The X-ray crystal structures of four prokaryotic NAT proteins have now been determined, and these have been used to generate structural models of eukaryotic NATs, providing valuable insight into their active-site architecture. In addition to aiding crystallographic experiments, recent progress in the production of recombinant prokaryotic and eukaryotic NATs has allowed comparative studies of the kinetics and activity profiles of these enzymes. In this review we present an overview of recent structural and activity studies on NAT enzymes, and we outline how in silico methods may be used to predict NAT protein-ligand interactions based on the current knowledge.

Ex vivo differentiation of human adult bone marrow stem cells into cardiomyocyte-like cells

Bone marrow mesenchymal stem cells have been shown to transdifferentiate into cardiomyocytes after 5-azacytidine treatment or co-culturing with rodent cardiomyocytes. We investigate if adult human bone marrow stem cells can be differentiated ex vivo into cardiomyocyte-like cells (CLCs) independent of cytotoxic agents or co-culturing technique. Sternal bone marrow was collected from 16 patients undergoing coronary artery bypass surgery. Mesenchymal stem cells were differentiated in a cardiomyogenic differentiation medium containing insulin, dexamethasone, and ascorbic acid. Differentiation towards CLCs was determined by induced expression of cardiomyocyte-specific proteins. Differentiated CLCs expressed multiple structural and contractile proteins that are associated with cardiomyocytes. Thin filament associated myofibrillar proteins were detected early in the cells, with cardiac troponin I, sarcomeric tropomyosin, and cardiac titin among the first expressed. Some CLCs were found to develop into a nascent cardiomyocyte phenotype with cross-striated myofibrils characterized by alpha-actinin-positive Z bands after 4-5 passages in differentiated culture. These lineage-defined CLCs may be potentially useful for repairing damaged myocardium.

Human VEGF165-myoblasts produce concomitant angiogenesis/myogenesis in the regenerative heart

Bioengineering the regenerative heart may provide a novel treatment for heart failure. On May 14, 2002, a 55-year-old man suffering from ischemic myocardial infarction received 25 injections carrying 465 million cGMP-produced pure myoblasts into his myocardium after coronary artery bypass grafting. As on August 28, 2002, his EKG was normal and showed no arrhythmia. His ejection fraction increased by 13%. He no longer experienced shortness of breath and angina as he did before the treatment. Three myogenesis mechanisms were elucidated with 17 human/porcine xenografts using cyclosporine as immunosuppressant. Some myoblasts developed to become cardiomyocytes. Others transferred their nuclei into host cardiomyocytes through natural cell fusion. As yet others formed skeletal myofibers with satellite cells. De novo production of contractile filaments augmented the heart contractility. Human myoblasts transduced with VEGF165 gene produced six times more capillaries in porcine myocardium than in placebo. Xenograft rejection was not observed for up to 20 weeks despite cyclosporine discontinuation at 6 weeks. Pros and cons of autografts vs. allografts are compared to guide future development of heart cell therapy.

Generation and analysis of mice with a targeted disruption of the arylamine N-acetyltransferase type 2 gene

Arylamine N-acetyltransferases (NATs) are polymorphic xenobiotic metabolising enzymes, linked to cancer susceptibility in a variety of tissues. In humans and in mice there are multiple NAT isoforms. To identify whether the different isoforms represent inbuilt redundancy or whether they have unique roles, we have generated mice with a null allele of Nat2 by gene targeting. This mouse line conclusively demonstrates that the different isoforms have distinct functions with no compensatory expression in the Nat2 null animals of the other isoforms. In addition, we have used the transgenic line to show the pattern of Nat2 expression during development. Although Nat2 is not essential for embryonic development, it has a widespread tissue distribution from at least embryonic day 9.5. This mouse line now paves the way for the teratological role of Nat2 to be tested.

Feasibility of using low-volume tissue samples for gene expression profiling of advanced non-small cell lung cancers

PURPOSE

The majority of patients with non-small cell lung cancer (NSCLC) present at an advanced clinical stage, when surgery is not a recommended therapeutic option. In such cases, tissues for molecular research are usually limited to the low-volume samples obtained at the time of diagnosis, usually via fine-needle aspiration (FNA). We tested the feasibility of performing gene expression profiling of advanced NSCLCs using amplified RNA from lung FNAs.

EXPERIMENTAL DESIGN AND RESULTS

A total of 46 FNAs was tested, of which 18 yielded RNA of sufficient quality for microarray analysis. Expression profiles of these 18 samples were compared with profiles of 17 pairs of tumor and normal lung tissues that had been surgically obtained. Using a variety of unsupervised and supervised analytical approaches, we found that the FNA profiles were highly distinct from the normal samples and similar to the tumor profiles.

CONCLUSIONS

We conclude that when RNA amplification is successful, gene expression profiles from NSCLC FNAs can determine malignancy and suggest that with additional refinement and standardization of sample collection and RNA amplification protocols, it will be possible to conduct additional and more detailed molecular analysis of advanced NSCLC using lung FNAs.

Arylamine N-acetyltransferases: a pharmacogenomic approach to drug metabolism and endogenous function

The arylamine N-acetyltransferases (NATs) are a unique family of enzymes that catalyse the transfer of an acetyl group from acetyl-CoA to the terminal nitrogen of hydrazine and arylamine drugs and carcinogens. The NATs have been shown to be important in drug detoxification and carcinogen activation, with humans possessing two isoenzymes encoded by polymorphic genes. This polymorphism has pharmacogenetic implications, leading to different rates of inactivation of drugs, including the anti-tubercular agent isoniazid and the anti-hypertensive drug hydralazine. Mice provide a good model for human NAT, allowing genetic manipulation of expression to explore possible endogenous roles of these enzymes. The first three-dimensional NAT structure was resolved for NAT from Salmonella typhimurium, and subsequently the structure of NAT from Mycobacterium smegmatis has been elucidated. These identified a 'Cys-His-Asp' catalytic triad (conserved in all NATs), which is believed to be responsible for the activation of the active site cysteine residue. As more genomic data become available, NAT homologues continue to be found in prokaryotic species, many of which are pathogenic, including Mycobacterium tuberculosis. The discovery of NAT in M. tuberculosis is particularly significant, since this enzyme participates in inactivation of isoniazid in the bacterium, with implications for isoniazid resistance. Structural studies on NAT proteins and phenotypic analyses of organisms (both mice and prokaryotes) following genetic modifications of the nat genes are leading to an understanding of the potentially diverse roles of NAT in endogenous and xenobiotic metabolism. These studies have indicated that NAT, particularly in Mycobacteria, has the potential to be a drug target. Combinatorial chemical approaches, together with in silico structural studies, will allow for advances in the identification of NAT substrates and inhibitors, both as experimental tools and as potential drugs.

Electronic-topological study of structurally diverse cyclooxygenase-2 inhibitors

A large series of cyclooxygenase-2 (COX-2) inhibitors with diverse skeletons were investigated by means of the Electronic-Topological Method. A system for the COX-2 inhibitor activity prognostication was built with 6 pharmacophores and 6 anti-pharmacophores. The forecasting ability of the system was also tested on different structures, which differ from those that characterize the series studied.

Pharmacogenetics of the arylamine N-acetyltransferases

The arylamine N-acetyltransferases (NATs) are involved in the metabolism of a variety of different compounds that we are exposed to on a daily basis. Many drugs and chemicals found in the environment, such as those in cigarette smoke, car exhaust fumes and in foodstuffs, can be either detoxified by NATs and eliminated from the body or bioactivated to metabolites that have the potential to cause toxicity and/or cancer. NATs have been implicated in some adverse drug reactions and as risk factors for several different types of cancers. As a result, the levels of NATs in the body have important consequences with regard to an individual's susceptibility to certain drug-induced toxicities and cancers. This review focuses on recent advances in the molecular genetics of the human NATs.

Electronic-topological study of the structure-activity relationships in a series of piperidine morphinomimetics

Structure-activity relationships (SAR) are studied in the series of 4,4-disubstituted piperidine morphinomimetics (42 compounds) by means of the Electronic-Topological Method (ETM). In the frameworks of this approach, its input data were taken as the results of conformational and quantum-mechanical calculations. These calculations had been carried out for all compounds from the series under study, taking into account their neutral and protonated by the nitrogen of piperidine cycle forms. The ETM application resulted in a set of pharmacophores and anti-pharmacophores, which formed a basis of a system used to predict analgesic activity. First of all, the system was tested on known analgesics. Testing has shown a good agreement with the experimental data. Then, the system was applied to a few compounds with similar structures but unknown activity. The results of the study could be used for computer screening and design of novel compounds with analgesics properties as new potential drugs.

Genetic aberrations of NAT2 and chromosome 8: their association with progression in transitional cell carcinoma of the urinary bladder

INTRODUCTION/OBJECTIVE

N-acetyltransferase 2 (NAT2), mapped to 8p22, is a polymorphic enzyme which metabolizes aromatic amines. Loss of heterozygosity of 8p22 is associated with an increased risk of bladder cancer. This study evaluated NAT2 and chromosome 8 in sequential tumours from bladder cancer patients to determine if NAT2 alterations increase the risk of progression.

MATERIALS AND METHODS

Thirty-seven sequential carcinomas from 19 patients were assessed using fluorescence in situ hybridization.

RESULTS

Five carcinomas showed loss of NAT2; 4 of these were from pTa/pT1 tumours. Polysomy 8 was observed in 4 of 14 (29%) primary carcinomas (pTa/pT1), in 4 of 12 (33%) pTa/pT1 recurrences, and in 90% (9/10) of the detrusor muscle invasive tumours (pT2+). 6 of 8 (75%) locally invasive tumours with polysomy 8 were from patients who subsequently developed disease progression (pT2+). In total, 13.5% (5/37) of the carcinomas were abnormal for NAT2, and 46% (17/37) were abnormal for chromosome 8 copy number. Polysomy 8 was associated with high grade (p = 0.01) and stage (p = 0.03) and disease progression (p = 0.03).

CONCLUSION

Whilst there does not appear to be an association between loss of NAT2 and risk of progression in transitional cell carcinoma, the high rate of polysomy of chromosome 8 implies that other genes on this chromosome significantly influence disease progression.

Metabolic gene polymorphism frequencies in control populations

Using the International Project on Genetic Susceptibility to Environmental Carcinogens (GSEC) database containing information on over 15,000 control (noncancer) subjects, the allele and genotype frequencies for many of the more commonly studied metabolic genes (CYP1A1, CYP2E1, CYP2D6, GSTM1, GSTT1, NAT2, GSTP, and EPHX) in the human population were determined. Major and significant differences in these frequencies were observed between Caucasians (n = 12,525), Asians (n = 2,136), and Africans and African Americans (n = 996), and some, but much less, heterogeneity was observed within Caucasian populations from different countries. No differences in allele frequencies were seen by age, sex, or type of controls (hospital patients versus population controls). No examples of linkage disequilibrium between the different loci were detected based on comparison of observed and expected frequencies for combinations of specific alleles.

Evidence towards the role of arylamine N-acetyltransferase in Mycobacterium smegmatis and development of a specific antiserum against the homologous enzyme of Mycobacterium tuberculosis

Arylamine N-acetyltransferase (NAT) in humans inactivates the anti-tubercular drug isoniazid (INH). Homologues of human NAT are present in Mycobacterium tuberculosis and Mycobacterium smegmatis, where they can acetylate, and hence inactivate, INH. The in vivo role of mycobacterial NAT is not known but heterologous expression of the M. tuberculosis gene increases the INH resistance. The 0.85 kb nat gene is part of a gene cluster in M. smegmatis. The gene is transcribed as a large, 7.5 kb mRNA as demonstrated by Northern analysis. A nat knockout strain of M. smegmatis was generated by targeted disruption. The new strain was confirmed to be devoid of NAT activity. The growth of the knockout strain is considerably delayed compared with the wild-type, due to an extended lag phase. The knockout mutant has an increased sensitivity to INH as would be predicted. The NATs from M. smegmatis and M. tuberculosis have a high degree of homology, except in the region of the C terminus. A specific polyclonal antiserum raised against recombinant NAT protein from M. tuberculosis is described that recognizes a stretch of about twenty residues within the C terminus of M. tuberculosis NAT. This highly specific antiserum will enable comparison of nat expression between isolates of M. tuberculosis.

Current smoking, occupation, N-acetyltransferase-2 and bladder cancer: a pooled analysis of genotype-based studies

The aim of this study was to investigate the association of NAT2 gene polymorphism with bladder cancer using the data derived from the International Project on Genetic Susceptibility to Environmental Carcinogens. Four case control studies conducted in four European countries, plus two case series, one from England and one from Germany, for a total of 1530 cases and 731 controls (all Caucasian) were included. The interaction between NAT2 and bladder cancer considering smoking habits and occupational exposure was studied. There was a significant association between NAT2 and bladder cancer (odds ratio: 1.42, 95% confidence interval: 1.14-1.77), with a slightly significant heterogeneity among studies. However, heterogeneity disappeared when smokers were divided into current and ex-smokers. The risk of cancer was elevated in smokers and occupationally exposed subjects, with the highest risk among slow acetylators. The increase in risk was limited, in fact, to current smokers (odds ratio = 1.74, 95% confidence interval: 0.96-3.15). This analysis confirms that the NAT2 genotype is a risk factor for bladder cancer by interacting with smoking or occupational exposures. Our observation suggests that NAT2 is not a risk factors per se but modulates the effect of carcinogens contained in tobacco smoke (probably arylamines) or associated with occupational exposures.

Arylamine N-acetyltransferase of Mycobacterium tuberculosis is a polymorphic enzyme and a site of isoniazid metabolism

Arylamine N-acetyltransferases (NATs; E.C 2.3.1.5) N-acetylate arylhydralazine and arylamine substrates using acetyl coenzyme A. Human NAT2 acetylates and inactivates the antituberculosis drug, isoniazid (INH), and is polymorphic. We previously demonstrated that there is a homologue of human NAT2 in Mycobacterium tuberculosis, whose product N-acetylates INH in vitro. We now demonstrate that the nat gene is expressed in M. tuberculosis and M. bovis Bacille Calmette-Guerin (BCG), using reverse transcription-polymerase chain reaction and Western blotting. The NAT protein is active in M. bovis BCG in vivo, as detected by the presence of N-acetyl INH in M. bovis BCG lysates grown in INH. Sequence analysis of the M. tuberculosis nat coding region reveals a single nucleotide polymorphism in 18% of a random cohort of M. tuberculosis clinical isolates, conferring a G to R change. The recombinant mutant protein appears less stable than the wild type, and has an apparent affinity for INH of 10-fold less than the wild type. Modelling the change in M. tuberculosis NAT shows that the G to R change is close to the active site, and supports the experimental findings. Minimum inhibitory concentration data suggest that this polymorphism in nat is linked to low-level changes in the INH susceptibility of M. tuberculosis clinical isolates.

Thromboprophylaxis with 60 mg enoxaparin is safe in hip trauma surgery

BACKGROUND

Little information is available concerning dosage and optimal initiation of thromboprophylactic therapy with low-molecular-weight heparin (enoxaparin) in nonelective hip surgery. The aim of our prospective study was to evaluate the incidence of clinically apparent deep vein thrombosis (DVT), pulmonary embolism (PE), and major hemorrhage in patients receiving thromboprophylaxis with enoxaparin undergoing hip surgery after hip fracture.

METHOD

From 946 consecutive patients admitted with hip fractures, 897 were operated on and received enoxaparin according to the following regimen: Preoperative heparinization from time of admission onwards. Administration of 60 mg enoxaparin, in two doses (20 and 40 mg subcutaneously), during the first 5 days postoperatively. Prophylaxis for a minimum of 5 weeks (40 mg daily).

RESULTS

Clinical signs of DVT were present in 37 patients (4.2%), who all underwent venography. In five patients, DVT was confirmed (0.6%). None of these patients suffered from PE. Another four patients (0.4%) developed clinical signs of PE, and suspected diagnosis was confirmed by computed tomographic scan in two (0.2%). No deaths because of PE were observed. Major hemorrhage occurred in 42 patients (4.7%), there was one death from hemorrhage caused by an intracerebral event. No case of heparin-induced thrombocytopenia type II was observed.

CONCLUSION

Thromboprophylaxis with 60 mg enoxaparin daily, in split doses, starting before surgery, is safe and appropriate in patients with hip fractures. Clinically apparent DVT and PE are rarely observed, and bleeding complications are comparable to those occurring with a conventional thromboprophylactic regimen.

N-Acetyltransferases, sulfotransferases and heterocyclic amine activation in the breast

Heterocyclic amines are mammary carcinogens in rats and their N-hydroxy metabolites are substrates for subsequent metabolic activation by N-acetyltransferases (NAT) and sulfotransferases (SULT) in man. We investigated the expression of these enzymes in human breast tissue and the relationship between NAT genotype and NAT mRNA expression or enzyme activity. Immunohistochemical staining of sections of breast tissue identified expression of NAT1 and NAT2 protein in human mammary epithelial cells, but not in the stroma. We also measured the formation of DNA adducts of the heterocyclic amines 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in calf thymus DNA after incubation of their promutagenic N-hydroxy metabolites with mammary cytosols prepared from reduction mammoplasty tissue. Experimental observations gained from use of enzyme cofactors and NAT and/or SULT inhibitors on cytosolic enzyme activity, recombinant NAT1 activity and heterocyclic amine-DNA adduct formation suggest that both NAT1 and SULT1A enzymes contribute significantly to the activation of N-hydroxylated heterocyclic amines in mammary tissue. NAT1 mRNA transcript levels were found to be two- to three-fold higher than mRNA transcripts of the NAT2 gene in reduction mammoplasty tissue and mammary epithelial cells. NAT1-specific p-aminobenzoic acid acetylation activity, but not NAT2-specific sulfamethazine acetylation activity, was detectable in mammary cytosols. There was no association apparent between NAT genotype and the levels of NAT mRNA or NAT enzyme activity, or between NAT1 genotype and IQ-DNA adduct formation mediated by mammary cytosols. Western blot analysis of mammary cytosolic protein showed detectable levels of SULT1A1 and SULT1A3.

In vitro genesis of subaxial cervical unilateral facet dislocations through sequential soft tissue ablation

STUDY DESIGN

In vitro anatomic study investigating the degree of soft tissue disruption required to produce a subaxial cervical unilateral facet dislocation.

OBJECTIVES

To develop an understanding of the relative contributions to stability of the subaxial cervical soft tissues and to define an anatomic threshold of injury necessary to produce a unilateral cervical facet dislocation.

SUMMARY OF BACKGROUND DATA

The literature at this time is unclear regarding the precise pathomechanics of a cervical unilateral facet dislocation and the required threshold of soft tissue injury necessary for its genesis. Published clinical reports do not make any specific reference to these factors or are unclear in their objectivity.

METHODS

Two adjacent vertebra at a time in 10 fresh-frozen subaxial cervical spine specimens (C2-C3 to C6-C7) were transfixed in the coronal plane with 3.5-mm Schanz screws. A steady unilateral vertical distraction force resulting in lateral cervical flexion was applied to these screws as the surrounding cervical soft tissue structures were sequentially ablated. Four experimental models were developed, varying the order of soft tissue disruption.

RESULTS

The physiologic coupling of subaxial cervical unilateral distraction and rotation, because of the spatial orientation or inclination of the cervical facet joints, allowed the creation of a unilateral facet dislocation without an additional flexion moment. Disruption of the ipsilateral articular capsule, ligamentum flavum, and more than half of the anulus fibrosus was necessary for the genesis of a unilateral facet dislocation. Disruption of the supraspinous and interspinous ligaments was not necessary but appeared to facilitate or lessen the force required to dislocate a unilateral facet. Disruption of the anterior and posterior longitudinal ligaments and intertransverse ligaments was not necessary to create a unilateral facet dislocation.

CONCLUSION

This anatomic study further supports the theory that discontinuity of the anterior and posterior longitudinal ligaments is not necessary for a unilateral facet dislocation to occur. The ipsilateral facet capsule, anulus fibrosus, and ligamentum flavum appear to be the physical soft tissue restraints that need to be disrupted to produce a unilateral facet dislocation.

[Injuries of the thoracic vertebrae in head-first dive into water]

116 patients with cervical spine injuries due to water sport accidents treated in eight Austrian institutions from 1991 to 1998 were reviewed retrospectively. There were 93% male, 72% were 15 to 29 years of age. 93% had injuries from diving into swimming pools or into open water. At discharge 58 patients had Frankel A lesions, 39 had incomplete cord lesions Frankel B to D, and 19 patients had no neurological injury. This data suggest that in Austria approximately one person per one million inhabitants per year sustains a spinal cord injury in a diving accident in shallow water.

Fenestration of the extracranial vertebral artery: review of the literature

STUDY DESIGN

A case report on fenestration of the extracranial vertebral artery found at forensic autopsy.

OBJECTIVE

To describe an extracranial vertebral artery fenestration involving the subaxial cervical region, assessed radiographically and angiographically at forensic autopsy, in a young man.

SUMMARY OF BACKGROUND DATA

Duplications or fenestrations of the extracranial course of the vertebral artery are rare and seen almost exclusively as a coincidental finding in angiographic studies. The terms "fenestration" and "duplication" are often incorrectly used synonymously. The former describes the passage of the duplicated vessel within the vertebral foramen transversarium, whereas the latter refers to the duplicated vessel coursing additionally through the spinal canal. The reported cases describing duplication are more common. Only three cases of vertebral extracranial fenestrations, involving only the upper cervical spinal segments, have been described in the literature.

RESULTS

Angiography showed a fenestration of the vertebral artery localized between the intervertebral spaces of C2-C3 and C3-C4. At dissection, the vertebral artery appeared as a single vessel in the area of the fenestration. Histologically, a distinct difference in the thickness and composition of the vessel walls was found between the two vessel trunks. At autopsy, no further anomalies were observed in the vessels supplying the brain, which is contrary to the commonly held belief that fenestration is frequently associated with vascular malformations.

CONCLUSION

Fenestration of the extracranial course of the vertebral artery is a developmental or congenital anomaly. A review of the literature demonstrated that this is apparently only a coincidental finding and has no pathologic significance.

Arylamine N-acetyltransferases - of mice, men and microorganisms

Arylamine N-acetyltransferases (NATs) catalyse the transfer of an acetyl group from acetyl CoA to the terminal nitrogen of hydrazine and arylamine drugs and carcinogens. These enzymes are polymorphic and have an important place in the history of pharmacogenetics, being first identified as responsible for the polymorphic inactivation of the anti-tubercular drug isoniazid. NAT has recently been identified within Mycobacterium tuberculosis itself and is an important candidate for modulating the response of mycobacteria to isoniazid. The first three-dimensional structure of the unique NAT family shows the active-site cysteine to be aligned with conserved histidine and aspartate residues to form a catalytic triad, thus providing an activation mechanism for transfer of the acetyl group from acetyl CoA to cysteine. The unique fold could allow different members of the NAT family to play a variety of roles in endogenous and xenobiotic metabolism.

Chromosome mapping of the genes for murine arylamine N-acetyltransferases (NATs), enzymes involved in the metabolism of carcinogens: identification of a novel upstream noncoding exon for murine Nat2

Arylamine N-acetyltransferases (NATs) catalyse acetylation reactions which can result in either detoxification or activation of arylamine carcinogens. The human NAT loci (NAT1, NAT2, and a pseudogene, NATP) have been mapped to human chromosome 8p22, a region frequently deleted in tumours. There are three functional genes in mice (Nat1, Nat2, and Nat3) encoding for three NAT isoenzymes. Different alleles at the Nat2 locus are responsible for the acetylation polymorphism identified in different mouse strains. We show that Nat3 is close to Nat1 and Nat2, by screening of a P1 artificial chromosome (PAC) library and provide cytogenetic evidence for co-localisation of the three genes in chromosome region 8 B3.1-B3.3. The Nat region of mouse and human is homologous. We also provide sequence information and a restriction map in the vicinity of Nat1 and Nat2 and describe a noncoding exon located 6 kb upstream of the Nat2 coding region.

Placental arylamine N-acetyltransferase type 1: potential contributory source of urinary folate catabolite p-acetamidobenzoylglutamate during pregnancy

Human arylamine N-acetyltransferase type 1 (NAT1), better known as a drug-metabolising enzyme, has been proposed to acetylate the folate catabolite p-aminobenzoylglutamate (p-abaglu) to N-acetamidobenzoylglutamate (ap-abaglu) which is a major urinary folate catabolite. Using mass spectroscopic analysis, we demonstrate the formation of ap-abaglu by recombinant human NAT1 and human placental homogenates. Using density gradient centrifugation the placental enzymic activity which acetylates p-aba and the placental enzymic activity acetylating p-abaglu both have an S(20,w) value of 3.25 S. This is the expected value for a monomer of human NAT1 (33 kDa). The specific NAT1 inhibitor 5-iodosalicylate inhibits acetylation of both p-aba and p-abaglu catalysed by either recombinant human NAT1 or placental samples as the source of enzyme. These data demonstrate that NAT1 is the major placental enzyme involved in acetylating p-abaglu.

Mechanical factors responsible for the obstruction of the gliding mechanism of a dynamic hip screw for stabilizing pertrochanteric femoral fractures

BACKGROUND

In treatment of pertrochanteric femoral fractures with dynamic hip screws (DHSs) (135-degree, Synthes, Bettlach, Switzerland), damage was observed in removed lag screws, leading to the conclusion that the gliding mechanism must have been obstructed as a result of either inappropriate position of the implant or insufficient medial support in the fracture zone.

METHODS

The forces and moments transmitted in the screw socket are calculated using a mathematical model to find the optimal position of the implant.

RESULTS

The forces and moments depend on the position and orientation of the lag screw as well as on the position of the contact point between the two main fragments. By changing the point of contact, a better decrease of the load to the DHS can be achieved than by changing the position and orientation of the screw. For a low contact point, the model shows the lowest values for the forces in the socket.

CONCLUSION

Complete agreement was found between the results of the presented calculations and our own clinical experience in removed DHSs.

Association analysis of drug metabolizing enzyme gene polymorphisms in HIV-positive patients with co-trimoxazole hypersensitivity

The use of co-trimoxazole in HIV-positive patients has been associated with a high frequency (40-80%) of hypersensitivity reactions. This has been attributed to the bioactivation of the sulphonamide component, sulphamethoxazole (SMX), to its toxic hydroxylamine and nitroso metabolites. The aim of this study was to determine whether functionally significant polymorphisms in the genes coding for enzymes involved in SMX metabolism influence susceptibility to SMX hypersensitivity. HIV-positive patients with (n = 56) and without (n = 89) SMX hypersensitivity were genotyped for allelic variants in CYP2C9, GSTM1, GSTT1, GSTP1 and NAT2 using polymerase chain reaction (PCR) and/or PCR-restriction fragment length polymorphism analysis. The CYP2C9*2/*3 genotype and CYP2C9*3 allele frequencies were nine- and 2.5-fold higher in the hypersensitive group compared to non-sensitive patients, respectively, although they were not statistically significant when corrected for multiple testing. There were no differences in the frequencies of the GSTM1 and GSTT1 null genotypes, and the slow acetylator genotype, between hypersensitive and non-sensitive patients, while GSTP1 frequency was lower (although non-significant) in the hypersensitive group [21% versus 32%, odds ratio (OR) = 0.5, Pc = 0.24]. Comparison of the genotype frequencies in HIV-positive and -negative patients showed that the NAT2 slow acetylator genotype frequency in the HIV-positive patients (74%) was significantly (Pc = 0.0003, OR = 2.3) higher than in control subjects (56%). Our results show that genetic polymorphisms in drug metabolizing enzymes are unlikely to be major predisposing factors in determining individual susceptibility to co-trimoxazole hypersensitivity in HIV-positive patients.

An update on genetic, structural and functional studies of arylamine N-acetyltransferases in eucaryotes and procaryotes

Arylamine N:-acetyltransferase (NAT) was first identified as the inactivator of the anti-tubercular drug isoniazid. The enzyme was shown to catalyse the transfer of an acetyl group from acetyl-CoA to the terminal nitrogen of the hydrazine drug. The rate of inactivation of isoniazid was polymorphically distributed in the population and was one of the first examples of pharmacogenetic variation. NAT was identified recently in Mycobacterium tuberculosis and is a candidate for modulating the response to isoniazid. Genome sequences have revealed many homologous members of this unique family of enzymes. The first three-dimensional structure of a member of the NAT family identifies a catalytic triad consisting of aspartate, histidine and cysteine proposed to form the activation mechanism. So far, all procaryotic NATs resemble the human enzyme which acetylates isoniazid (NAT2). Human NAT2 is characteristic of drug-metabolizing enzymes: it is found in liver and intestine. In humans and other mammals, there are up to three different isoenzymes. If only one isoenzyme is present, it is like human NAT1. Human NAT1 and its murine equivalent specifically acetylate the folate catabolite p-aminobenzoylglutamate. NAT1 and its murine homologue each have a ubiquitous tissue distribution and are expressed early in development at the blastocyst stage. During murine embryonic development, NAT is expressed in the developing neural tube. The proposed endogenous role of NAT in folate metabolism, and its multi-allelic nature, indicate that its role in development should be assessed further.

The effects of staged static cervical flexion-distraction deformities on the patency of the vertebral arterial vasculature

STUDY DESIGN

Thirty-five fresh frozen cervical spine specimens underwent vertebral artery cannulization and angiography to determine the static influence of the four stages of subaxial flexion-distraction injuries as described by Allen et al on vertebral artery patency.

OBJECTIVES

To evaluate the degree of vertebral vessel deformation and potential injury in staged static flexion-distraction deformities of the cervical spine.

SUMMARY AND BACKGROUND DATA

Asymptomatic vertebral artery injury is found in up to 19% of all patients who incur trauma to the lower cervical spine. This incidence increases in flexion-distraction deformities. It is unclear as to the individual contributions of various force loads and resultant deformity on the etiology of these injuries.

RESULTS

No significant deformation in vertebral artery flow was noted in the flexion-distraction Stage I injuries within the physiologic range of cervical flexion. Flexion-distraction Type II and III injuries (unilateral and bilateral facet dislocations, respectively) demonstrated considerable impairment to vertebral artery dye flow in proportion to the degree of vertebral deformity. Manipulating the dislocated vertebral segments into a localized lordosis (flexion-distraction Stage II) further impaired vertebral vessel patency. Coexistent rupture of the vertebral radicular vessels was a constant finding in Stage II and III injuries. Longitudinal stretch deformities of the vertebral artery were limited primarily to the injured vertebral segment. Stage IV injuries resulted in irreversible disruption of vertebral dye flow.

CONCLUSION

The static deformity of flexion-distraction Stage II to IV subaxial cervical injuries results in significant objective compression of the vertebral vasculature. The precise contribution of static cervical malalignment related to advanced staged flexion distraction injuries on irreversible vertebral vessel flow disruption is presently uncertain.

Structure of arylamine N-acetyltransferase reveals a catalytic triad

Enzymes of the arylamine N-acetyltransferase (NAT) family are found in species ranging from Escherichia coli to humans. In humans they are known to be responsible for the acetylation of a number of arylamine and hydrazine drugs, and they are strongly linked to the carcinogenic potentiation of certain foreign substances. In prokaryotes their substrate specificities may vary and members of the gene family have been linked to pathways including amide synthesis during rifamycin production. Here we report the crystal structure at 2.8 A resolution of a representative member of this family from Salmonella typhimurium in the presence and absence of a covalently bound product analog. The structure reveals surprising mechanistic information including the presence of a Cys-His-Asp catalytic triad. The fold can be described in terms of three domains of roughly equal length with the second and third domains linked by an interdomain helix. The first two domains, a helical bundle and a beta-barrel, make up the catalytic triad using a structural motif identical to that of the cysteine protease superfamily.

Expression of arylamine N-acetyltransferases in pre-term placentas and in human pre-implantation embryos

Arylamine N -acetyltransferases (NATs) catalyse the acetylation from acetyl-CoA of arylamines and hydrazines. There are two human isoenzymes which show polymorphism, and both enzymes are involved in the activation and detoxification of environmental carcinogens and teratogens. The two human isoenzymes NAT1 and NAT2 show different tissue distribution, with human NAT2 being found in liver and intestine whilst human NAT1 is expressed in many tissues including erythrocytes, bladder, lymphocytes and neural tissue, as well as liver and intestine. It has been proposed that NAT1 has an endogenous role in the acetylation of the folate catabolite p -aminobenzoyl-L-glutamate (pABGlu) to produce the major urinary product, N -acetyl-pABGlu. The murine homologue of human NAT1 is known to be concentrated in the neural tube during development. We show here that human NAT1 but not human NAT2 is expressed in pre-implantation embryos at the blastocyst stage and show that NAT1 is also expressed in early human placenta at the earliest available stage, 5.5 weeks. We demonstrate that there is inter-individual variation in NAT1 expression. In view of the role of folate in protecting against neural tube defects, we propose that NAT1 is a candidate risk factor for susceptibility to neural tube defects.