PubMed Health⌕ Search

Biomedical subjects

E Lee

Publications and source records attributed to E Lee.

At least 19 recordsLinked to original sources
PubMed1995

Allelotype analysis of childhood acute lymphoblastic leukemia.

To identify the genetic events that may play an important role in leukemogenesis of childhood ALL, we report for the first time the allelotyping of childhood ALL. Twenty-four cases of childhood ALL were screened for loss of heterozygosity (LOH) using 101 highly polymorphic microsatellite markers, which are distributed among all autosomal chromosomes. For LOH analysis on both chromosomes 9 and 12, 54 childhood ALL samples were examined. The most frequent allelic loss was found on chromosomal arm 9p, where 20 of 50 (40%) informative samples showed LOH. Moreover, nearly 30% of samples that did not have either homozygous deletions or point mutations of the putative tumor suppressor genes CDKN2/INK4A/p16 and INK4B/p15 on chromosomal arm 9p had LOH at D9S171. Loss of chromosomal arm 12p was also frequent (26%). Mutational analysis suggested that the altered gene on 12p is not the cyclin-dependent kinase inhibitor p27/Kip1, which is also on 12p. Several other regions that had LOH included 1p, 4q, 5p, 6q, 7p, 8p, 9q, 10q, 13q, 17p, 17q, 18q, 19q, and 22q. Of 24 patients, 19 (79%) showed allelic loss on at least one chromosomal arm. Samples of two patients (8%) showed LOH on almost all chromosomes. Fractional allelic loss, calculated for each sample as the total number of chromosomal arms lost/total number of arms with information, showed a median value of 0.04 and a mean of 0.123 (range, 0 to 0.95). This fractional allelic loss is lower than those reported for many solid tumors. This analysis shows the extreme power of LOH analysis using microsatellite markers in childhood ALL.

Adolescent↗
PubMed1995

Tertiary and quaternary structural changes in Gi alpha 1 induced by GTP hydrolysis.

Crystallographic analysis of 2.2 angstrom resolution shows that guanosine triphosphate (GTP) hydrolysis triggers conformational changes in the heterotrimeric G-protein alpha subunit, Gi alpha 1. The switch II and switch III segments become disordered, and linker II connecting the Ras and alpha helical domains moves, thus altering the structures of potential effector and beta gamma binding regions. Contacts between the alpha-helical and Ras domains are weakened, possibly facilitating the release of guanosine diphosphate (GDP). The amino and carboxyl termini, which contain receptor and beta gamma binding determinants, are disordered in the complex with GTP, but are organized into a compact microdomain on GDP hydrolysis. The amino terminus also forms extensive quaternary contacts with neighboring alpha subunits in the lattice, suggesting that multimers of alpha subunits or heterotrimers may play a role in signal transduction.

Binding Sites↗
PubMed1995

Murray valley encephalitis virus envelope protein antigenic variants with altered hemagglutination properties and reduced neuroinvasiveness in mice.

Neutralization escape variants of Murray Valley encephalitis virus were selected using a type-specific, neutralizing, and passively protective anti-envelope protein (E) monoclonal antibody (4B6C-2) which defines epitope E-1c. Nucleotide sequence analysis revealed single nucleotide changes in the E genes of 15 variants resulting in nonconservative amino acid substitutions in all cases. One variant had a three-nucleotide deletion in the E gene which resulted in loss of serine at residue 277. Changes were clustered into two separate regions of the E polypeptide (residues 126-128 and 274-277), indicating that E-1c is a discontinuous epitope. One variant (BHv1), altered at residue 277 (Ser-->Ile), failed to hemagglutinate across the pH range 5.5-7.5, in contrast to parental virus and the other escape variants which hemagglutinated at an optimal pH of 6.6. BHv1 was also of reduced neuroinvasiveness in 21-day-old mice following intraperitoneal inoculation compared to the other viruses. Parental virus and the neutralization escape variants grew equally well in both vertebrate and invertebrate cell cultures, indicating that the reduced neuroinvasiveness of BHv1 was not due to a major abnormality of replication.

Amino Acid Sequence↗
PubMed1995

The modulation of phosphatidylinositol biosynthesis in hamster hearts by methyl lidocaine.

Methyl lidocaine is an experimental anti-arrhythmic drug which has been shown to enhance the biosynthesis of phosphatidyl-inositol (PI) in the hamster heart. In this study, the effect of methyl lidocaine on enzymes involved in the biosynthesis of PI in the heart was examined. When the hamster heart was perfused with labelled methyl lidocaine, the majority of the compound was not metabolized after perfusion. The direct action of methyl lidocaine on an enzyme was studied by the presence of the drug in enzyme assays, whereas its indirect action was studied by assaying the enzyme activity in the heart after methyl lidocaine perfusion. CTP:phosphatidic acid cytidylyl-transferase, a rate-limiting enzyme in PI biosynthesis, was stimulated by methyl lidocaine in a direct manner. Kinetic studies revealed that methyl lidocaine caused a change in the affinity between the enzyme and phosphatidic acid and resulted in the enhancement of the reaction. Alternatively, acyl-CoA:lysophosphatidic acid acyltransferase, another key enzyme for PI biosynthesis, was not activated by the presence of methyl lidocaine. However, the enzyme activity was stimulated in hearts perfused with methyl lidocaine. The enhancement of the acyl-transferase by methyl lidocaine perfusion was found to be mediated via the adenylate cyclase cascade with the elevation of the cyclic AMP level. The stimulation of protein kinase A activity by cyclic AMP resulted in the phosphorylation and activation of the acyltransferase. Interestingly, the activity of protein kinase C was not stimulated by methyl lidocaine perfusion. We conclude that the enhancement of PI biosynthesis by methyl lidocaine in the hamster heart resulted from the direct activation of the cytidylyltransferase, as well as the phosphorylation and subsequent activation of the acyltransferase.

Acyltransferases↗
PubMed1995

Site-specific cleavage of chromosomes in vitro through Cre-lox recombination.

Site-specific recombination systems are useful tools for chromosome engineering in vivo and site-specific DNA cleavage methods have applications in genome analysis and gene isolation. Here, we report a new method to fragment chromosomes in vitro using the Cre-lox site-specific recombination system. Two lox sites were targeted into the 5.7 Mb chromosomes I of Schizosaccharomyces pombe. In vitro recombination between chromosomal lox sites and exogenously provided lox oligonucleotides 'cleaved' the chromosome at the defined lox sequences. Site-specific cleavage of lox sites in the tobacco genome was also demonstrated. This recombination-based cleavage method provides a novel approach for structural and functional analyses of eukaryotic chromosomes as it allows direct isolation of chromosome regions that correspond to phenotypes revealed through Cre-lox mediated chromosome rearrangements in vivo. Moreover, recombination with end-labeled lox oligonucleotides would permit the specific end-labeling of chromosome segments to facilitate the long range mapping of chromosomes.

Base Sequence↗
PubMed1995

Lead-induced nephropathy: relationship between various biological exposure indices and early markers of nephrotoxicity.

Lead nephropathy in adults is silent and insidious, characterized by the absence of proteinuria in its early phase. Of the early markers of nephrotoxicity, urinary N-acetyl-beta-D-glucosaminidase (NAG) appears to be the only one that is elevated in early lead nephropathy. However, the elevation in urinary NAG activity may be a response to a sharp increase in renal burden of lead. Its usefulness as a marker of chronic lead nephropathy is thus in doubt. There is a need, then, to identify a reliable early biological indicator of lead-induced kidney damage. Furthermore, there is also a need to identify suitable markers of chronic exposure to describe meaningful dose-response and dose-effect relationships. Traditionally, blood lead (PbB) was used, but the current blood lead level (PbBrec) is more an indicator of recent exposure. Time-integrated blood lead indices (PbBint) derived from repeated serial PbB measurements can be used as indices of chronic exposure. In 128 lead-exposed workers, the PbBint was the most important exposure variable in describing the variability in urinary alpha 1-microglobulin (U alpha 1 m), urinary beta 2-microglobulin (U beta 2m), and urinary retinol binding protein (URBP). U alpha 1m was the only marker that was significantly higher in the exposed group, with a good dose-response and dose-effect relationship with PbBint. The lack of dose-response and dose-effect relationships in other studies may be due to inappropriate exposure markers as well as less sensitive response markers. PbBint has a better correlation than PbBrec. Furthermore, U alpha 1m may be the most sensitive of the markers because of its higher molecular weight.

Adolescent↗
PubMed1995

Glomerular function of lead-exposed workers.

Among lead-exposed workers, there is evidence of increased mortality from chronic renal diseases (nephritis and nephrosis). Epidemiological studies using early markers of nephropathy among lead-exposed workers failed to demonstrate early renal changes. This study is aimed at assessing the glomerular function of 137 lead-exposed subjects and at evaluating whether changes in markers of glomerular function are related to exposure indices derived from longitudinal blood lead data. A control group of 153 postal workers was also investigated. Several exposure indices were derived for the exposed workers, including a time-integrated index Pb in blood (PbB)int and the number of times the PbB was above critical values (PbB400, PbB500, PbB600). Through multiple linear regression analysis, PbBint was the best predictor of variation in serum beta 2-microglobulin (S beta 2m) and alpha 1-microglobulin (S alpha 1m) and urinary albumin (UA1b). A small but statistically significant difference in the mean beta 2m was found. S beta 2m was also the only marker showing a significantly higher prevalence rate ratio (PRR) of abnormalities among lead-exposed workers. Though there was no clear dose-response relationship with PbBint as the index of dose, all the 15 subjects with abnormal S beta 2m in the older age group were found in the highest PbBint group. Furthermore, of the 8 subjects with low 4-h creatinine clearance (CrCl4h), 6 had abnormal levels of beta 2m. Two subjects with CrCl4h of less than 75 ml/min/1.74 m2 had high PbBint values, thus suggesting that high blood lead levels over a prolonged time may be associated with decreased CrCl4h. Though the long-term significance of elevated S beta 2m and UA1b is unclear, their association with high PbBint and decreasing CrCl4h indicate a potentially adverse effect. Their relationship with PbB400 and PbB600 suggests that the threshold of 700 micrograms/l for PbB may not prevent the occurrence of lead nephropathy.

Adolescent↗
PubMed1995

Human vascular smooth muscle cell-monocyte interactions and metalloproteinase secretion in culture.

Degradation of the atherosclerotic plaque extracellular matrix could destabilize the lesion, rendering it more prone to rupture. Both macrophages and vascular smooth muscle cells (SMCs) are potential sources of matrix metalloproteinases (MMPs), secreted enzymes that can digest vascular matrix. We explored interactions between human vascular SMCs and human monocytes that result in the secretion of interstitial collagenase (MMP-1) and stromelysin (MMP-3). Monocytes alone or those treated with SMC-conditioned media did not secrete these metalloproteinases as detectable by Western blot analysis. SMCs increased secretion of both MMP-1 and MMP-3 greater than 20-fold when cocultured with monocytes or when treated with monocyte-conditioned media. Addition of macrophage colony stimulating factor (< or = 1000 U/mL) to cocultures of monocytes and SMCs did not affect metalloproteinase secretion. Recombinant interleukin (IL)-1 receptor antagonist inhibited MMP-1 and MMP-3 induction in SMC cultures treated with monocyte-conditioned media (94% and 96% reduction, respectively), while a neutralizing antibody to tumor necrosis factor-alpha had no significant effect on metalloproteinase secretion. In contrast to the induction by monocyte-conditioned media of MMP-1 and MMP-3 secretion by SMCs, monocyte-conditioned media did not increase secretion of 72-kD gelatinase (MMP-2). Thus, monocytes induce MMP-1 and MMP-3 secretion by vascular SMCs through an IL-1-dependent mechanism. This response of SMCs to a defined macrophage product may contribute to plaque destabilization by mononuclear phagocytes in the lesion.

Cells, Cultured↗
PubMed1995

Alterations of the p16 (MTS1) gene in testicular, ovarian, and endometrial malignancies.

PURPOSE: The p16 (MTS1) gene codes for a cyclin-dependent kinase inhibitor and may be a new tumor suppressor gene. It is frequently mutated in a variety of cell lines established from tumors. This is the first report of screening for alteration of the p16 gene in testicular, ovarian and endometrial malignancies. MATERIALS AND METHODS: We examined alterations of p16 in 78 primary genital tumors (42 testicular, 21 ovarian and 15 endometrial cancers) and mononuclear cells from 2 patients with Lynch syndrome II as well as 5 testicular tumor cell lines by single-strand conformation polymorphism (SSCP) and Southern blot hybridization. RESULTS: The DNA from the p16 gene of 2 testicular tumors (5%), an ovarian cancer (4%) and a testicular tumor cell line (20%) had altered migration in gel electrophoresis as shown by SSCP. Analysis of DNA sequence of these samples revealed a polymorphism at codon 140. Southern blot hybridization detected neither deletions nor rearrangements of the p16 gene in any of the samples. CONCLUSIONS: Taken together, these results suggest that p16 alterations probably are not important for tumorigenesis of testicular, ovarian and endometrial tumors.

Base Sequence↗
PubMed1994

Role of TCR zeta chain in T cell development and selection.

Signals mediated by the T cell receptor (TCR) are required for thymocyte maturation and selection. To examine the role of TCR zeta chain signals in development, TCR expression was restored in zeta-deficient mice with transgenic zeta chains that partially or completely lacked sequences required for signal transduction. The zeta chain played a role in thymic development by promoting TCR surface expression, but zeta-mediated signals were not essential because TCRs that contained signaling-deficient zeta chains promoted T cell maturation and transduced signals associated with thymic selection.

Amino Acid Sequence↗
PubMed1994

Metaanalysis of prophylactic drug treatment in the prevention of postoperative bleeding.

Prophylactic drug treatment is one of several strategies to reduce postoperative blood loss and potentially limit homologous blood use in open heart surgery. A computerized MEDLINE search supplemented with manual bibliography reviews was performed for randomized clinical trials published in peer-reviewed English-language journals from January 1980 to June 1993. A metaanalysis was conducted of trials evaluating desmopressin (group DD, n = 13), epsilon-aminocaproic acid or tranexamic acid (group EA, n = 4), and aprotinin (group AP, n = 16). Eligible studies used placebo controls and administered the drug in a prophylactic manner. The primary study end point was postoperative chest tube loss (mL, mean +/- standard deviation). There was a significant reduction in postoperative chest tube loss detected for each of the active treatments versus the placebo (DD versus controls: percent reduction 0.11, p = 0.0021; EA versus controls: percent reduction 0.30, p < 0.0001; and AP versus controls: percent reduction 0.36, p < 0.0001). Therapy with EA or AP was associated with a greater reduction in chest tube loss than DD (EA versus DD, p = 0.0033, and AP versus DD, p < 0.0001). Secondary study end points were transfusion requirements, chest reexploration, and perioperative mortality. The volume of postoperative red cell transfusion (mean +/- standard deviation) was reduced with EA (p < 0.0001) or AP treatment (p < 0.0001) compared with a placebo or DD, whereas the proportion of patients given transfusions was limited only in the AP-treated patients (odds ratio 0.23; 95% confidence interval, 0.16 to 0.33; p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminocaproic Acid↗
PubMed1993

Field molecular epidemiology. Feasibility of monitoring for the malignant bladder cell phenotype in a benzidine-exposed occupational cohort.

Modern molecular and cellular biology have provided powerful new approaches to study cancer in the research laboratory, but these techniques have not been used extensively in field studies or in screening of high-risk occupational cohorts. The primary objective of this study was to demonstrate the use of cellular and molecular methods in combination with medical and epidemiologic methods to identify cancer cases, risk factors, and markers in a previously identified and defined cohort of Chinese workers exposed to benzidine. The screening of exposed workers included occupational, medical, and smoking histories to identify exogenous risk factors, a limited physical examination, Papanicolaou (PAP) urinary cytology, measurement of urine pH, quantitative fluorescence image analysis (QFIA) cytology to detect DNA hyperploidy, and quantitative fluorescence to detect expression of a low-grade bladder tumor-associated antigen (p300) by exfoliated urothelial cells and elevated expression of the neu oncogene product (p185). Detailed analysis of the accuracy of epidemiologic data and the adequacy of samples and accuracy of molecular techniques was carried out. Three groups were included in this study: group 1 included 23 bladder cancer cases who had previously been exposed to benzidine and served as two surrogates for late-emerging disease; group 2 consisted of 20 subjects with previous exposure history but not previously diagnosed with bladder cancer; and group 0 was the nonexposure and nonbladder cancer controls. The results showed that accurate questionnaire data and urine samples can be obtained at remote sites. Among the 20 group 2 subjects, two displayed abnormal findings by both QFIA cytology and p300 expression and were later confirmed to have bladder cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzidines↗
PubMed1992

Factors influencing gastroduodenal mucosal prostaglandin concentrations: roles of smoking and aging.

OBJECTIVE: To evaluate behavioral, demographic, clinical, and histologic variables that independently influence gastroduodenal mucosal prostaglandin concentrations. DESIGN: Prospective study. SETTING: A clinical research laboratory located in a Department of Veterans Affairs hospital. PATIENTS: Fifty-two healthy adults who had no history of peptic ulcer disease and who were not receiving nonsteroidal anti-inflammatory drugs. MEASUREMENTS: Mucosal biopsy specimens were obtained endoscopically from the stomach (body and antrum) and the duodenum (bulb and postbulbar area). Mucosal extracts from each of these four regions were assessed by radioimmunoassay to determine prostaglandin E2 and prostaglandin F2 alpha concentrations. Specimens were also examined histologically for inflammation and the presence of Helicobacter pylori. A multivariate linear regression model was used to determine which behavioral, demographic, and histologic variables significantly and independently influenced gastroduodenal mucosal prostaglandin concentrations. RESULTS: Smoking and older age were independently associated with lower prostaglandin concentrations in all four mucosal regions (P = 0.0001 to P = 0.05). Compared with results in young nonsmokers, mucosal prostaglandin concentrations were reduced by 70% to 80% in older smokers. Gender, alcohol use, endoscopic appearance, dyspeptic symptoms, mucosal inflammation, and the presence of H. pylori had no consistent effect on prostaglandin content. CONCLUSION: Smoking and older age are associated with significantly reduced gastric and duodenal prostaglandin concentrations. These observations may help explain the predisposition to ulcer disease in smokers and older persons.

Adult↗
PubMed1992

Catalytic subunits of Aplysia neuronal cAMP-dependent protein kinase with two different N termini.

Previously, two forms of cAMP-dependent protein kinase catalytic subunit generated by mutually exclusive use of two internal exon cassettes (A1 and A2) were demonstrated in Aplysia neurons. Here, it is shown that there also exist catalytic subunits with alternative N termini derived from two exons, N1 and N2, expressed in combination with either of the internal cassettes. Processed transcripts including N1 or N2 sequences are of about equal abundance in the nervous system, arise through alternative promoter use, and encode catalytically active polypeptides. The N2 amino acid sequence is 21 residues longer than the N1 sequence and is homologous to the nonmyristoylated N terminus of the TPK1 gene product, a yeast catalytic subunit homolog. These data support the view that cAMP-dependent protein kinase activity in Aplysia neurons is produced by a complex array of regulatory and catalytic subunits that generate multiple holoenzymes with a spectrum of properties.

Amino Acid Sequence↗
PubMed1992

The G226A mutant of Gs alpha highlights the requirement for dissociation of G protein subunits.

Adenylylcyclase cannot be activated by hormones or guanine nucleotide analogs in membranes from cells that express the G226A mutant form Gs alpha instead of the wild-type protein. The mutant Gs alpha protein appears incapable of undergoing the conformational change necessary for guanine nucleotide-induced dissociation of the G protein alpha subunit from the beta gamma subunit complex (Miller, R.T., Masters, S.B., Sullivan, K.A., Beiderman, B., and Bourne, H.R. (1988) Nature 334, 712-715). G226A Gs alpha was synthesized in Escherichia coli, purified, and characterized. Examination of the kinetics of dissociation of guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) suggests that G226A Gs alpha is incapable of assuming the conformation necessary for high affinity binding of Mg2+ to the alpha subunit-GTP gamma S complex. Associated changes include the failure of Mg2+ and GTP gamma S to confer resistance to tryptic proteolysis upon the protein, to enhance intrinsic tryptophan fluorescence, or to cause dissociation of alpha from beta gamma. However, the GTPase activity of the mutant protein is near normal (at high Mg2+ concentrations), and the protein is capable of activating adenylylcyclase. A similar defect is present in G49V Gs alpha. Failure of G protein subunit dissociation appears to be the explanation for the phenotypic properties of cells that express G226A Gs alpha, and this mutation thus highlights the crucial nature of this reaction as a component of G protein action.

Adenylyl Cyclases↗
PubMed1992

Importance of gastric acid in gastric ulcer formation in rabbits with antibody-induced prostaglandin deficiency.

The role of gastric acid in the development of gastroduodenal ulcers in prostaglandin-deficient conditions is unclear. In the current study, the effect of the proton pump inhibitor omeprazole on the formation of gastric ulcers was examined in a previously validated rabbit model of antibody-induced prostaglandin deficiency. Intragastric administration of 20 mg/kg omeprazole every 12 hours caused a profound suppression of gastric acidity (i.e., pH above 5 continuously). This same dose of omeprazole significantly reduced gastric ulcer formation induced by passive immunization with 6-keto-prostaglandin F1 alpha antibodies. It is concluded from these observations that gastric acid plays a critical role in the formation of gastric ulcers in rabbits with antibody-induced prostaglandin deficiency.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Subepithelial collagen table thickness in colon specimens from patients with microscopic colitis and collagenous colitis.

Microscopic colitis and collagenous colitis are similar conditions that are differentiated by the presence or absence of subepithelial collagen table thickening. To better understand the relationship between these two disorders and the role of collagen table thickening in the pathogenesis of diarrhea, colonic mucosal biopsy specimens from 24 patients with microscopic or collagenous colitis and 9 control subjects were analyzed using a computer-assisted morphometric method to evaluate the average thickness of the subepithelial collagen table. The collagen table thickness in colitis patients taken together formed a multimodal rather than a unimodal distribution. There was no tendency for collagen table thickening to increase with age or with duration of symptoms. In general, the types and distribution of inflammatory cells were similar in patients with normal and thickened collagen tables. Stool weight correlated with lamina propria cellularity but not with collagen table thickening. The multimodal distribution of collagen table thickening and the lack of correlation with age, duration of symptoms, or inflammation suggest that microscopic colitis and collagenous colitis are discrete conditions, although the inflammatory changes in the two conditions are similar. Moreover, because stool weight correlates with lamina propria cellularity but not with collagen table thickening, diarrhea probably is caused by the inflammatory changes and not by collagen table thickening per se.

Adult↗