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Biomedical subjects

E Sim

Publications and source records attributed to E Sim.

At least 37 records · Page 2Linked to original sources
PubMed1998

Transforming growth factor-beta1 and lung allograft fibrosis.

OBJECTIVES: Transforming growth factor beta1 (TGF-beta1) is a potent immunosuppressive cytokine that promotes fibrosis by enhancing the synthesis of extracellular matrix components. The repair process following lung allograft injury is due to rejection or infection replaces lung parenchyma by fibrotic tissue, leading to pulmonary dysfunction. The role of TGF-beta1 in this excessive healing process and increasing the risk of infection is unknown. METHODS: We analysed our patient data to investigate the relevance of different factors on allograft fibrosis and its correlation with TGF-beta1. Fibrosis was graded in H and E stained sections. TGF-beta1 genotype was determined in all patients. RESULTS: Patients were aged between 16 and 62 years (mean age of 39.6 years). Procedures were heart/lung (n = 32), double lung (n = 18), and SLT (n = 41). A total of 46 patients had lung allograft fibrosis diagnosed in transbronchial biopsies sections. Patients who had developed interstitial fibrosis had significantly more acute rejection episodes (mean 3.4 +/- 2.8) compared with patients without fibrosis (mean 2.1 +/- 2.2) (P = 0.024). The presence of eosinophils in the interstitium preceded and were associated with the development of fibrosis regardless of the rejection grade (P = 0.0001). TGF-beta1 was heavily expressed in sections with fibrosis with a mean score of 6.8 +/- 2.9 compared with 2.4 +/- 0.6 in sections with no fibrosis (P < 0.0001). TGF-beta1 expression correlated positively with fibrosis grades (P < 0.0001). The mean survival for patients with a fibrosis score > 6 is 892.4 +/- 73 days compared with mean survival 427 +/- 78 in patients with scores < 6 (P = 0.0001). Patients who developed fibrosis had homozygous TGF-beta1 genotype that correlates with excessive TGF-beta1 expression (P = 0.01). The use of cardiopulmonary bypass was associated with the development of excessive fibrosis (P = 0.02), and 7 patients who had severe fibrosis died of septicaemia (17.5%). FEV1 (forced expiratory volume) was significantly higher in patients without fibrosis (1870 +/- 111 ml versus 1590 +/- 160; P = 0.02). CONCLUSIONS: The risks of lung allograft fibrosis increases with recurrent rejection, tissue eosinophilia, homozygous TGF-beta1 genotype and the use of bypass machine. Fibrosis was associated with higher mortality and morbidity might be explained by the TGF-beta1 immunosuppressive and fibrotic properties. Immunological strategies to down-regulate TGF-beta1 production might improve survival and function of lung allografts.

Adolescent↗
PubMed1998

Placental expression of arylamine N-acetyltransferases: evidence for linkage disequilibrium between NAT1*10 and NAT2*4 alleles of the two human arylamine N-acetyltransferase loci NAT1 and NAT2.

The study of placental xenobiotic metabolism is important for the determination of foetal exposure to environmental chemicals as placental metabolism influences the nature of chemicals reaching the foetus from its mother's blood. Arylamine N-acetyltransferases are drug metabolizing enzymes which N-acetylate hydrazines and arylamines, including carcinogenic arylamines and sulphonamide drugs. The two human arylamine N-acetyltransferase isoenzymes, NAT1 and NAT2, are encoded at multi-allelic loci. Here, we have determined N-acetyltransferase (NAT) activity in term placentas from normal, uncomplicated pregnancies. Both NAT1 and NAT2 enzyme activities were detectable. Placental NAT1 activity was at least 1000 fold greater than NAT2 activity. There was a 6 fold inter-placental variation in NAT1 activity. Mean placental NAT1 specific activity was 1.42 nmoles para-aminobenzoic acid N-acetylated.min-1.mg protein-1, which is comparable to NAT1 specific activities which have been measured in adult tissues. The NAT1, but not the NAT2, protein was detectable in placentas by Western blotting. Maternal and foetal NAT genotypes were determined from placenta, using placental blood clots and cord blood respectively, allowing NAT haplotype determination. There appeared to be linkage disequilbrium between NAT1* and NAT2* alleles such that the combination NAT1*10/NAT2*4 was found 3.5 times more frequently than would be expected.

Acetyltransferases↗
PubMed1998

Expression of arylamine N-acetyltransferase in human intestine.

BACKGROUND: Arylamine N-acetyltransferases in humans (NAT1 and NAT2) catalyse the acetylation of arylamines including food derived heterocyclic arylamine carcinogens. Other substrates include the sulphonamide 5-aminosalicylic acid (5-ASA), which is an NAT1 specific substrate; N-acetylation of 5-ASA is a major route of metabolism. NAT1 and NAT2 are both polymorphic. AIMS: To investigate NAT expression in apparently healthy human intestines in order to understand the possible role of NAT in colorectal cancer and in the therapeutic response to 5-ASA. METHODS: The intestines of four organ donors were divided into eight sections. DNA was prepared for genotyping NAT1 and NAT2 and enzymic activities of NAT1 and NAT2 were determined in cytosols prepared from each section. Tissue was fixed for immunohistochemistry with specific NAT antibodies. Western blotting was carried out on all samples of cytosol and on homogenates of separated muscle and villi after microdissection. RESULTS: NAT1 activity of all cytosols was greater than NAT2 activity. NAT1 and NAT2 activities correlated with the genotypes of NAT1 and NAT2 and with the levels of NAT1 staining determined by western blotting. The ratio of NAT1:NAT2 activities showed interindividual variations from 2 to 70. NAT1 antigenic activity was greater in villi than in muscle. NAT1 was detected along the length of the villi in the small intestine. In colon samples there was less NAT1 at the base of the crypts with intense staining at the tips. CONCLUSIONS: The interindividual variation in NAT1 and NAT2 in the colon could affect how individuals respond to exposure to specific NAT substrates including carcinogens and 5-ASA.

Arylamine N-Acetyltransferase↗
PubMed1998

Technique for dissecting the cervical vertebral column.

Dissecting the cervical vertebral column usually is presumed in the course of a routine autopsy to be difficult and time-consuming. Additionally, most techniques described in the literature lead to extensive mutilation of the corpse. We present a method which can be performed quickly and is learned easily. The major advantage of our technique is that the integrity of the corpse, in particular of the facial surface, is maintained.

Autopsy↗
PubMed1997

A fragment consisting of the first 204 amino-terminal amino acids of human arylamine N-acetyltransferase one (NAT1) and the first transacetylation step of catalysis.

Human arylamine N-acetyltransferase 1 (NAT1) has 290 amino acids and acetylates arylamines from acetyl coenzyme A. The acetyl group forms a thiolester with Cys 68 in the enzyme, and the acetyl group is then transferred to the arylamine. When NAT1 is expressed using the pGEX vector, the glutathione S-transferase (GST)-NAT1 fusion protein catalyses the acetylation of the NAT1 substrate p-aminobenzoic acid from acetyl CoA. Neither GST alone, nor a fusion protein of GST with the N-terminal 204 amino acids of NAT, catalyses the acetylation of p-aminobenzoic acid from acetyl CoA. Using [3H]acetyl CoA as substrate, it is shown that the full-length NAT1 and the N-terminal 204 amino acids of NAT1 each form an acetylated intermediate on reaction with acetyl CoA.

Acetyl Coenzyme A↗
PubMed1997

Joint salvaging surgery for an extensive giant cell tumor of the proximal femur complicated by a transcervical fracture.

The case of a 20-year-old man with an unusually large giant-cell tumor of the proximal right femur complicated by a transcervical fracture is presented. In view of the patient's age, stabilization with a dynamic hip screw combined with valgus osteotomy, curettage and bone grafting was preferred to total hip replacement. Femoral head salvage has been successful to date.

Adult↗
PubMed1997

Localization of polymorphic N-acetyltransferase (NAT2) in tissues of inbred mice.

Like humans, mice exhibit polymorphism in the N-acetylation of aromatic amines, many of which are toxic and/or carcinogenic. Mice have three N-acetyltransferase (Nat) genes, Nat1, Nat2 and Nat3, and Nat2 is known to be polymorphic. There is a dramatic difference in the acetylation of NAT2 substrates by blood from fast (C57BL/6J) compared with slow acetylator (A/J) mice. However, the acetylation of these substrates by liver cytosols from the two strains is very similar. In order to determine whether the expression of the NAT2 protein corresponded with the activities measured, a polyclonal antipeptide antisera was raised against the C-terminal decapeptide of NAT2 and characterized using recombinant murine NAT2 antigen. Enzyme-linked immunosorbent assays (ELISAs) demonstrated that the anti-NAT2 antiserum bound in a concentration-dependent fashion to recombinant NAT2. Immunochemical analysis of mouse liver cytosols from C57BL/6J or A/J livers indicated that the level of NAT2 protein expressed in the two strains was similar. Immunohistochemical staining of C57BL/6J liver with anti-NAT2 antiserum showed that NAT2 was expressed in hepatocytes throughout the liver although the intensity of staining in the perivenous (centrilobular) region was higher than that in the periportal region. NAT2 was also detected in epithelial cells in the lung, kidney, bladder, small intestine and skin as well as in erythrocytes and lymphocytes in the spleen and hair follicles and sebaceous glands in the skin. Characterization of the distribution of NAT2 will be of value in elucidating the role of polymorphic N-acetylation in protecting the organism from environmental insults as well as in endogenous metabolism.

Acetylation↗
PubMed1997

Mapping AAC1, AAC2 and AACP, the genes for arylamine N-acetyltransferases, carcinogen metabolising enzymes on human chromosome 8p22, a region frequently deleted in tumours.

Arylamine N-acetyltransferases (NATs) are encoded at two loci on 8p22, a region subject to deletions in bladder tumours. The two functional genes (AAC1 and AAC2 alias NAT1 and NAT2) without introns in the coding region, encode enzymes which metabolise carcinogens, including bladder carcinogens. They are both multi-allelic and certain alleles have been implicated as susceptibility factors in bladder cancer. There is a third N-acetyltransferase gene, a pseudogene, AACP alias NATP, which we show is also located on chromosome 8 at the p22 region. We have mapped a series of YAC clones (ICI and CEPH) containing the NAT genes and the markers D8S21, an RFLP marker, and D8S261, a microsatellite marker. We show that D8S21 is a portion of the coding region of AAC2. The order of genes in this region, covering some 2 Mb, is TEL-D8S261-AAC1-AACP-AAC2 (D8S21)-CEN. The restriction map also illustrates that there are likely to be other expressed genes in the region through the identification of CpG islands.

Arylamine N-Acetyltransferase↗
PubMed1996

Fatal transdental posterior rotary subluxation of the cervical spine. A case report.

STUDY DESIGN: The cervical spine of an 86-year-old man known to have a fracture of the odontoid process was removed at autopsy and dissected. OBJECTIVES: To establish the cause of death, which was not apparent. SUMMARY OF BACKGROUND DATA: Ruptures of the vertebral arteries in patients with fractures of the odontoid process are rare. Only a few reports are published in the literature. Those that address postmortem findings in patients with fractures of the odontoid process do not make any reference to associated capsular and ligamentous injuries and the resultant instabilities. METHODS: Because of legal constraints, the cervical spine was removed en bloc 1 week after the patient's death and carefully dissected. RESULTS: In addition to the known bony injury, rupture of the left vertebral artery, epidural hematoma, disruption of the posterior atlantoaxial ligaments, hemorrhage into the anterior ligamentous structures, rupture of the capsule of the right atlantoaxial joint, and stretching of the capsule of the left joint were found to be present. Displacement of the spinal cord by an epidural hematoma secondary to rupture of the left vertebral artery was recorded as the apparent cause of death. The rupture had obviously been caused by the abnormal rotation of the atlas on the axis in a clockwise direction. CONCLUSIONS: Both the fatal outcome and the pathologic examination showed that established management concepts, particularly screw fixation of a fractured odontoid process, should be reconsidered in light of the potential occurrence of transdental posterior rotary subluxation. Because the incidence of capsular, ligamentous, and vascular injuries associated with fractures of the odontoid process is still poorly understood, more autopsies would be needed. The case also raises the question of whether, in an elderly patient like ours, a fracture of the odontoid process should prompt immediate surgical stabilization.

Aged↗
PubMed1996

Long-time quantum simulation of the primary charge separation in bacterial photosynthesis.

Accurate quantum mechanical simulations of the primary charge transfer in photosynthetic reaction centers are reported. The process is modeled by three coupled electronic states corresponding to the photoexcited chlorophyll special pair (donor), the reduced bacteriopheophytin (acceptor), and the reduced accessory chlorophyll (bridge) that interact with a dissipative medium of protein and solvent degrees of freedom. The time evolution of the excited special pair is followed over 17 ps by using a fully quantum mechanical path integral scheme. We find that a free energy of the reduced accessory chlorophyll state approximately equal to 400 cm(-1) lower than that of the excited special pair state yields state populations in agreement with experimental results on wild-type and modified reaction centers. For this energetic configuration electron transfer is a two-step process.

Bacteriochlorophylls↗
PubMed1996

Augmentation of pulmonary blood flow with an axillary arteriovenous fistula after a cavopulmonary shunt.

Of 320 children with cyanotic congenital heart malformations who had previously undergone cavopulmonary shunt operations, 11 had increasing cyanosis and exercise intolerance and were considered unsuitable for definitive repair, a Fontan procedure, or other palliation. Eight had a previous Glenn shunt and three had a previous bidirectional cavopulmonary connection. To augment pulmonary blood flow, 10 patients underwent creation of an ipsilateral axillary arteriovenous fistula. Mean oxygen saturations were 80% +/- 2% before operation, 85% +/- 2% immediately after operation, and 84% +/- 3% at a mean follow-up interval of 7.4 years (range 0.1 to 15.5 years). Mean hemoglobin values were 202 +/- 10 gm/L before operation, 177 +/- 10 gm/L after operation, and 191 +/- 14 gm/L at latest review. The only complication was mild swelling of the arm distal to the fistula in one patient. All patients reported improvement in exercise tolerance. Eight patients have continued evidence of fistula patency. Development of ipsilateral pulmonary arteriovenous fistulas has not been observed in any patient. Creation of an axillary arteriovenous fistula to augment pulmonary blood flow after a cavopulmonary shunt provides useful palliation for complex cyanotic heart disease when other options are limited. Such additional sources of pulmonary blood flow may influence the development of pulmonary arteriovenous fistulas.

Arteriovenous Shunt, Surgical↗
PubMed1996

Arylamine N-acetyltransferase in erythrocytes of cystic fibrosis patients.

Sulphamethoxazole, a substrate of human arylamine N-acetyltransferase, is used in the treatment of cystic fibrosis patients, who metabolise the drug rapidly. Increased metabolic clearance of sulphamethoxazole has been suggested to account for this rapid metabolism. Arylamine N-acetyltransferase type 1 is expressed in erythrocytes and leucocytes and the activity in erythrocytes is shown to contribute approximately 99% of the activity of arylamine N-acetyltransferase type 1 in blood cells. Arylamine N-acetyltransferase type 1 activity in erythrocytes from 16 adult cystic fibrosis patients and 19 age-matched controls were compared. Although there is a variation in erythrocyte arylamine N-acetyltransferase type 1 activity within each group, no difference was found when the two groups were compared. All individuals from the cystic fibrosis and control groups were investigated for certain allelic variants of the arylamine N-acetyltransferase type 1 gene (NAT1). Only one copy of a mutant NAT1 allele (NAT1*11) was found. The heterozygous NAT1 individual is a cystic fibrosis patient with a low level of erythrocyte arylamine N-acetyltransferase type 1 activity. A second distinct arylamine N-acetyltransferase isozyme, arylamine N-acetyltransferase type 2, is encoded at the multi-allelic NAT2 locus. There was no correlation between erythrocyte arylamine N-acetyltransferase-1 activity and NAT2 alleles present in either the cystic fibrosis or control groups. The distribution of NAT2 alleles was very similar in the two groups. The increased clearance of sulphamethoxazole in cystic fibrosis patients appears unlikely to be due to erythrocyte arylamine N-acetyltransferase type 1 activity or to inheritance of alleles at either the NAT1 or NAT2 loci.

Adolescent↗
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↗