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E Sim

Publications and source records attributed to E Sim.

At least 55 records · Page 3Linked to original sources
PubMed1996

Immunochemical detection of arylamine N-acetyltransferase in normal and neoplastic bladder.

The N-acetyltransferase (NAT) phenotype is an important determinant of individual susceptibility to occupational bladder cancer. N-Acetyltransferases arc known to metabolize aromatic amine bladder carcinogens, but the functional significance of NAT expression in the target organ is unclear. To resolve this issue, polygonal antisera against purified recombinant enzymes and C-terminal peptides of human NAT Type 1 (NAT1) and Type 2 (NAT2) were generated. Western blot analysis of exfoliated cells from human urine, pig bladder homogenate, and human bladder tumor-derived cell lines showed that NAT1 was expressed in all three systems, whereas NAT2 did not appear to be expressed in the bladder. Immunohistochemical analysis of human bladder tumor sections indicated that well-differentiated tumor cells expressed NAT1, with the highest level of expression being found in the umbrella cells that line the bladder lumen. Poorly differentiated tumor regions appeared to express NAT1 at lower levels than did well-differentiated areas. These findings support the hypothesis that aromatic amines are metabolized in the bladder epithelium by NAT1.

Amino Acid Sequence↗
PubMed1995

Enzyme kinetic properties of human recombinant arylamine N-acetyltransferase 2 allotypic variants expressed in Escherichia coli.

Arylamine N-acetyltransferase (NAT2) catalyses the N-acetylation of primary arylamine and hydrazine drugs and chemicals. N-Acetylation is subject to polymorphism, and humans can be categorized as either fast or slow acetylators according to their ability to N-acetylate certain arylamine substrates in vivo. Genetic variants at the polymorphic NAT2 locus have been described. We expressed five of the most common NAT2 variants (NAT2 4, NAT2 5A, NAT2 5B, NAT2 6A and NAT2 7B) in Escherichia coli as a convenient source of the human variants. The apparent Km values (at 100 microM acetyl CoA as co-substrate) of the different NAT2 variants for sulphamethazine, dapsone, p-anisidine, 2-aminofluorene, procainamide and isoniazid were determined. Data show that the apparent Km of the slow variant NAT2 7B for the arylamine sulphamethazine was 10-fold lower than all the other allotypes. The apparent Km for the structurally related sulphone antibiotic dapsone was 5-fold lower for the slow variant NAT2 7B when compared with the wild-type NAT2 4. These results indicate that the NAT2 7B specific amino acid substitution, Gly286-Glu, is important in promoting the binding of sulphamethazine and dapsone to the active site.

Arylamine N-Acetyltransferase↗
PubMed1995

Purification of recombinant human N-acetyltransferase type 1 (NAT1) expressed in E. coli and characterization of its potential role in folate metabolism.

Human arylamine N-acetyltransferase type 1 (NAT1) has been cloned from human genomic DNA, into the vector pET(5a) and expressed in Escherichia coli. The recombinant protein has been purified to apparent homogeneity using anion exchange chromatography. The arylamine acceptor specificity, and the effect of potential NAT1 inhibitors has been investigated using purified recombinant protein. The Km of the recombinant NAT1 protein for the substrates para-aminobenzoate (p-aba) and 4-aminosalicylate are 14.3 and 11.8 microM, respectively. Folate and amethopterin were found to be potent competitive inhibitors of p-aba acetylation, with Ki values of 13.3 and 9.5 microM, respectively. The pteroate moiety of folate, in contrast is a poor inhibitor, with 100 microM pteroate inhibiting only 40% of NAT1 activity. A catabolite of folate para-aminobenzoly-L-glutamate has also been shown to be a NAT1 substrate with a Km value of 263 microM.

Arylamine N-Acetyltransferase↗
PubMed1995

Finite element analysis of the stress distributions in the proximal end of the femur after stabilization of a pertrochanteric model fracture: a comparison of two implants.

The study investigated the influence of two different implants--the dynamic hip screw (AOR) 135 degrees with 2-hole-plate and the 135 degrees gamma-nail (HowmedicaR)--on the resulting stress and strain distributions in the proximal femur after stabilization of an idealized trochanteric fracture under typical physiological loading conditions. Data recorded for the uninjured femur were used for comparison. Two-dimensional plane stress finite element models of the femur and the implants were used for the calculations. The three-dimensional nature of this problem was approximated by an appropriate distribution of element thickness according to the real geometry in combination with an overlay technique, superimposing special finite element layers for each constituent of the bone-implant system (i.e. steel, cortical and cancellous bone). Three variations of the idealized fracture were introduced, i.e. free, with callous and bony bridging, the screw being modelled in a movable ('dynamic') as well as in a locked state. As far as the resulting stress distributions are concerned, neither of the two implants proved to be significantly superior to the other for stabilization of the idealized fracture selected.

Bone Nails↗
PubMed1995

Influence of the apolipoprotein E genotype on amyloid deposition and neurofibrillary tangle formation in Alzheimer's disease.

The effect of the apolipoprotein E genotype on the development of late onset Alzheimer's disease is still debated. Neuropathological studies of Alzheimer's disease have found a great extent of amyloid deposition in cortex and blood vessel walls in association with the apolipoprotein E epsilon 4 genotype [Rebeck G. W. et al. (1993) Neuron 11, 575-580; Schmechel et al. (1993) Proc. natn. Acad. Sci. U.S.A. 90, 9649-9653]. In contrast, the relationship of apolipoprotein E genotype to neurofibrillary pathology in Alzheimer's disease has been less clear. In this study we present evidence on the influence of the apolipoprotein E genotype on Alzheimer's disease related pathology in a series of 76 autopsy cases that had pathology that fulfilled the CERAD criteria for Alzheimer's disease. We found that the presence of the apolipoprotein E epsilon 4 allele is correlated with increased amounts of both amyloid and neuritic pathology in the neocortex as determined using an image analysis system. Comparison of plaque and tangle densities with the allele doses of epsilon 2 and epsilon 4 revealed a striking parallelism, suggesting that the alleles exert their effects very early in the pathological process before deposition of plaques and tangles. Although the apolipoprotein E epsilon 2 allele had a protective effect against both amyloid deposition and neurofibrillary tangle formation, in the presence of the epsilon 4 allele this protective effect against neuritic pathology was less marked than against amyloid deposition. This differential effect on amyloid deposition and the accumulation of neuritic pathology suggests that different molecular mechanisms are involved in the effect of apolipoprotein E on amyloid deposition and on tau phosphorylation.

Aged↗
PubMed1995

Xenogenetics in multifactorial disease susceptibility.

Susceptibility to multifactorial disease includes both genetic and environmental components. These two aspects of susceptibility are interlinked through genetic control of an individual's response to the environment. As a first step in identifying disease susceptibility genes that influence the response of an individual to foreign compounds (xenobiotics), it is necessary to study disorders in which there is an identified environmental trigger. Establishing a DNA resource from individuals with known environmental exposure ('a xenogenetic register') for diseases with an established environmental aetiology is an essential step in beginning to understand how environmental factors contribute to the susceptibility to polygenic diseases. A complementary approach to identification of environmental factors is suggested using a comparison of genetically homogeneous subdivisions of individuals with polygenic diseases where there is no clue to the environmental trigger.

Animals↗
PubMed1995

Slow N-acetylation genotype is a susceptibility factor in occupational and smoking related bladder cancer.

Bladder cancer is a common multifactorial disease and is known to be associated with occupational exposure to arylamines. Smoking is also a recognised contributory environmental cause. Occupational bladder cancer has previously been associated with slow acetylation by N-acetyltransferase (NAT) in humans in phenotyping studies, but more recently there has been some controversy regarding this issue. NAT is an enzymic activity involved in the metabolism of arylamines, and its 'classical' polymorphism is due to multiple alleles at the NAT2 locus. A genotyping approach has been used to investigate NAT2 type in a population of 189 Caucasian bladder cancer patients attending a clinic at a hospital in Birmingham. Genomic DNA was prepared from a blood sample donated by each of the patients and was used in the polymerase chain reaction with primers specific for all NAT2 alleles. Restriction fragment length polymorphism analysis was used to determine which alleles were present. Results have been compared to those from an age-matched non-malignant Caucasian control population (59 individuals) from the same region. Occupational and smoking history was determined by questionnaire and a significant excess of genotypic slow acetylators is found in those groups of bladder cancer patients exposed to arylamines as a result of their occupation or who are cigarette smokers. A higher proportion of slow acetylators is also found in those bladder cancer patients without identified exposure to arylamines when compared to the non-malignant controls. Slow NAT genotype is therefore a contributory risk factor in bladder carcinogenesis which acts through influencing individual response to environmental carcinogens.

Acetylation↗
PubMed1995

Vertical facet splitting: a special variant of rotary dislocations of the cervical spine.

A special variant of rotary displacement of the cervical spine with vertical splitting of an inferior articular process by its articulating partner is reviewed. Eighteen patients with unilaterally locked facet joints confirmed by computerized tomography were seen between 1986 and 1991. Five patients presented with vertical split fractures of an inferior articular process by impaction of the superior process of the subjacent vertebra. This specific fracture pattern is not accounted for in current classifications. Four males and one female with a mean age of 31 years (range 16 to 49 years) were affected. Three of the patients showed no neurological deficits. One patient presented with cerebral contusion and paresis of the right upper extremity, and in one patient the posterior funiculus was involved. Three of the injuries had been sustained recently; the other two were of longer duration. Surgical treatment was chosen in the three cases of recent injury. In two cases surgery was prompted by neurological deficits; in the third case impaction was felt to be of inadequate depth. Surgery consisted in fracture reduction and interbody fusion using plates. The two cases of long-term fractures were treated conservatively, and ankylosis of the facet joints eventually provided adequate stability. If radicular or spinal symptoms are absent, this special variant of locked facet joints can successfully be treated conservatively leaving the rotary displacement uncorrected, provided impaction is adequately deep. The author's experience has shown that indications for surgical management are relative rather than absolute in this fracture variant and that use of computerized tomography is essential to establish the fracture pattern.

Adolescent↗
PubMed1995

Dapsone acetylation by human liver arylamine N-acetyltransferases and interaction with antiopportunistic infection drugs.

Dapsone is used in the treatment of Pneumocystis carinii pneumonia, an opportunistic infection that afflicts acquired immunodeficiency syndrome (AIDS) patients. Inhibition of N-acetyltransferase (NAT)-dependent acetylation of dapsone could increase peak plasma concentrations of dapsone and shift the biotransformation pathway to the P450-mediated formation of a toxic metabolite of dapsone, the hydroxylamine. Therefore, we have determined using human liver cytosol and bacterially expressed NATs, the NAT isoform responsible for acetylating dapsone and the potential for antiopportunistic infection drugs to inhibit this metabolic pathway. Formation of monoacetyldiaminodiphenylsulfone (MADDS) was quantitated by HPLC/UV detection at 270 nm after incubation of dapsone with 100 microM acetyl coenzyme A regenerating system and human liver cytosol. The mean +/- SD apparent KM for the formation of MADDS in three different human livers predicted to be fast acetylators based on genotyping was 98 +/- 17.6 microM, and the Vmax was 190 +/- 20 pmol/min/mg cytosol protein. Eadie-Hofstee transformation of the substrate velocity data was linear, indicating acetylation by a kinetically single enzyme. Sulfamethazine (250 microM) inhibited dapsone acetylation by 100% and 80%, respectively, at dapsone concentrations of 3 and 100 microM, in both fast- and slow-acetylating liver cytosol preparations, whereas para-amino-benzoic acid (100 microM) did not inhibit MADDS formation at either of these dapsone concentrations. Lineweaver-Burk plots of dapsone acetylation in the presence of 0, 25, and 50 microM sulfamethazine showed an increase in the apparent KM, with increase in sulfamethazine concentration with no change in the Vmax, indicating competitive inhibition of dapsone acetylation by sulfamethazine. The apparent KM of dapsone acetylation by bacterially expressed NAT1 and NAT2 enzymes was 687 and 136 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylation↗
PubMed1995

Repair of complete acromioclavicular separations using the acromioclavicular-hook plate.

Complete Tossy III acromioclavicular separations in 21 male patients (according to the Rockwood classification: 7 Type III and 14 Type V lesions) with a mean age of 31 years were treated by surgical repair with the acromicroclavicular-hook plate within a period of 6 years. The population consisted of 18 patients with acute injuries and 3 with old injuries. Six patients experienced infections and delayed wound healing; osteitis did not occur. In 1 case, delayed wound healing was combined with dislocation of the hook. Bending of the implant occurred in another patient. Sixteen patients underwent clinical and radiographic followup at a mean of 38 months. Four patients who had no complications and free mobility of the shoulder joint at the end of treatment after removal of the implant did not appear for followup. One patient died of a malignant brain tumor. According to a modified evaluation system by Poigenfürst et al, clinical and radiographic findings showed 8 excellent, 7 good, and 1 poor result. A secondary widening of the hook hole in the acromion was seen in 13 patients; this was related to the large range of motion of the acromioclavicular joint. Calcifications and ossifications in the coracoclavicular ligaments, diastases in the acromioclavicular joint, and redislocations were not significantly different when this method was compared with other surgical techniques as reported in the literature. Use of the acromioclavicular-hook plate permits retention in the transverse plane without impairing the joint itself, but the technique is challenging.

Acromioclavicular Joint↗
PubMed1995

Metabolic polymorphisms and cancer susceptibility.

The vast majority of cancers arise as a consequence of exposure to environmental agents that are toxic or mutagenic. In response to this, all higher organisms have evolved complex mechanisms by which they can protect themselves from environmental challenge. In many cases, this involves an adaptive response in which the levels of expression of enzymes active in the metabolism and detoxification of the foreign chemical are induced. The best characterized of these enzyme systems are the cytochrome P450s, the GSTs and the NATs. An unfortunate consequence of many of these reactions, however, is the creation of a toxic or mutagenic reaction product from chemicals that require metabolic activation before realizing their full carcinogenic potential. Altered expression of one or more of these drug metabolizing enzymes can therefore be predicted to have profound toxicological consequences. Genetic polymorphisms with well defined associated phenotypes have now been characterized in P450, GST and NAT genes. Indeed, many of these polymorphisms have been associated with decreased or increased metabolism of many tumour promoters and chemical carcinogens and hence offer protection against or increased susceptibility to many distinct tumour types.

Animals↗
PubMed1994

Arylamine N-acetyltransferase in Balb/c mice: identification of a novel mouse isoenzyme by cloning and expression in vitro.

Three genes encoding arylamine N-acetyltransferase were identified in Balb/c mice. All three genes were cloned from genomic DNA, sequenced and expressed in a bacterial expression system. Two of the genes corresponded to Nat-1 and Nat-2 which have been previously identified in A/J and C57B1/6 strains of mice (Martell et al., 1991). The new gene, designated Nat-3, can be distinguished from the other mouse Nat genes both by specific amplification using PCR and by restriction-endonuclease digestion. The products of all three genes are demonstrated to catalyse acetylation of aminofluorene and anisidine following expression in Escherichia coli.

Acetylation↗
PubMed1994

Chromosomal localization of human genes for arylamine N-acetyltransferase.

Arylamine N-acetyltransferase is encoded at two loci, AAC-1 and AAC-2, on human chromosome 8. The products of the two loci are able to catalyse N-acetylation of arylamine carcinogens, such as benzidine and other xenobiotics. AAC-2 is polymorphic and individuals carrying the slow-acetylator phenotype are more susceptible to benzidine-induced bladder cancer. We have identified yeast artificial chromosome clones encoding AAC-1 and AAC-2 and have used the cloned DNAs as fluorescent probes for in situ hybridization. The hybridization patterns allow assignment of AAC-1 and AAC-2 to chromosome 8p21.3-23.1, a region in which deletions have been associated with bladder cancer [Knowles, Shaw and Proctor (1993) Oncogene 8, 1357-1364].

Arylamine N-Acetyltransferase↗
PubMed1994

[Intraoperative irrigation of the subdural space after traumatic spinal cord lesions (based on 4 case examples)].

In experimental investigations on primates it has been shown that after a standardized transverse lesion of the spinal cord subdural perfusion with an artificial liquor solution (Elliot's B solution) of the region of the injury improved the eventual motoric function achieved. We tried to reproduce these experimental results in the management of four patients with acute spinal cord injury after trauma of the vertebral column. Due to the difficulty of an exact evaluation in this initial study an objective positive effect of perfusion with Ringer solution (at 37 degrees C) could not be confirmed in these patients. Nevertheless, the possibility of a positive influence of this adjuvant operative treatment on spinal cord injuries should be studied in a greater collective of patients. A multicentre study would be essential because of the limited number of cases in a single hospital.

Adult↗
PubMed1994

Transcondylar reinsertion of femoral avulsions of the anterior cruciate ligament: evaluation of the position in 20 cases using three-dimensional computed tomographic reconstruction.

The position of transcondylar small-caliber drill tunnels after reinsertion of femoral avulsions of the anterior cruciate ligament (ACL) including avulsions with bone or cartilage fragments, which escape objective verification by conventional roentogenography, was determined in 20 patients by an examination procedure using computed tomography. Coronary tomograms were used for three-dimensional reconstruction of the distal end of the femur and assessment of the position of the perforation sites in the area of the medial aspect of the lateral condyle as well as the distance between them in patients in whom two Kirschner wires had been used (16 patients). A correct position had been achieved only in 4 of the 16 cases with double reinsertion and in one of four cases in which a single Kirschner wire had been used. With exception of one only partially correct placement, localization was found ventrally from the transition line with a predominantly caudally directed component. Assuming a mean thickness of the anterior cruciate ligament of 5 mm, the distance of the drill tunnels in five cases met the anatomic requirements, was too small in six cases, too large in three cases, and could not be evaluated adequately in two cases. The results of the present study illustrate vividly the problems of the surgical technique of Palmer.

Adolescent↗