Biomedical subjects

J Lee

Publications and source records attributed to J Lee.

At least 793 records · Page 44Linked to original sources

PubMed1998

Unveiling two distinct ribonuclease activities and a topoisomerase activity in a site-specific DNA recombinase.

The site-specific DNA recombinase Flp shows two types of RNA cleavage activities on hybrid DNA-RNA substrates. One targets the phosphodiester position involved in DNA recombination and follows a related mechanistic path. In this two-step reaction, first-strand scission is mediated by a nucleophilic attack of the scissile phosphodiester bond by the active site tyrosine of Flp. The resultant 3'-O-phosphoryl tyrosine bond is then attacked by the adjacent 2'-hydroxyl group. The second activity targets the immediately adjacent phosphodiester bond to the 3' side using a distinct mechanism. In this reaction, the vicinal 2'-hydroxyl directly attacks the phosphate group in a manner that is reminiscent of the pancreatic RNase mechanism. The Flp protein can also be shown to possess a topoisomerase-like activity.

Base Sequence↗

PubMed1998

Coordinated leading and lagging strand DNA synthesis on a minicircular template.

The coordinated synthesis of both leading and lagging DNA strands is thought to involve a dimeric DNA polymerase and a looping of the lagging strand so that both strands can be synthesized in the same direction. We have constructed a minicircle with a replication fork that permits an assessment of the stoichiometry of the proteins and a measurement of the synthesis of each strand. The replisome consisting of bacteriophage T7 DNA polymerase, helicase, primase, and single-stranded DNA-binding protein mediates coordinated replication. The criteria for coordination are fulfilled: (1) a replication loop is formed, (2) leading and lagging strand synthesis are coupled, (3) the lagging strand polymerase recycles from one Okazaki fragment to another, and (4) the length of Okazaki fragments is regulated. T7 single-stranded DNA-binding protein is essential for coordination.

Bacteriophage T7↗

PubMed1998

Anthropometric predictors of breast cancer incidence and survival in a multi-ethnic cohort of female residents of Hawaii, United States.

OBJECTIVES: The purpose of the study was to describe the associations between height and body mass index (BMI) (wt/ht2) and breast cancer incidence and survival among female residents of Hawaii. METHODS: The study sample is a randomly-selected, multi-ethnic cohort of 17,628 women. A total of 378 incident breast cancer cases were identified via linkage to the Hawaii Tumor Registry over an average follow-up period of 14.9 years. Using age 50 as a cut-point, 86 were considered premenopausal cases, and 292 were postmenopausal. Proportional hazards analysis was used to describe the risks associated with height and BMI, after adjustment for age, education, race/ethnicity, and drinking status. For mortality analyses, there were 34 breast cancer deaths among the 365 breast cancer cases for which staging information was available. RESULTS: The risk of postmenopausal breast cancer was found to increase progressively across approximate tertiles of the distribution of height (P = 0.02 for trend test), with a significantly excess risk among women in the tallest tertile (risk ratio [RR] = 1.5, 95 percent confidence interval [CI] = 1.1-2.1). Baseline levels of BMI were related positively to breast cancer incidence among postmenopausal women, after control for the above covariates (P = 0.01 for trend test). Among postmenopausal women in the highest quintile of the BMI distribution, the RR was 1.5 (CI = 1.0-2.3, P = 0.04). Further analyses indicated the association between BMI and postmenopausal breast cancer incidence was strongest among women aged 65 years and older. After statistical control for the above covariates and stage of disease, pre-morbid levels of BMI were significantly predictive of death from breast cancer, with an approximate nine percent increase in risk per unit increase in BMI (P = 0.01). Compared with women in the lowest two quartiles, the RR among the heaviest women was 2.2 (CI = 0.9-5.4,P = 0.08). Height was not associated with risk of breast cancer mortality. CONCLUSIONS: Relative weight may be an important modifiable risk factor for both breast cancer incidence and prognosis. The association between height and breast cancer incidence is more difficult to interpret, but may underscore the importance of early life exposures in the development of breast cancer.

Adult↗

PubMed1998

Serum vitamin D metabolite levels and the subsequent development of prostate cancer (Hawaii, United States)

OBJECTIVES: Because several serum studies of vitamin D metabolites have produced equivocal results on their relation to prostate cancer risk, the purpose of this study is to evaluate this association further. METHODS: A nested case-control study in a cohort of 3,737 Japanese-American men examined from 1967 to 1970 was conducted in Hawaii (United States). At the time of examination, a single blood specimen was obtained, and the serum was frozen. After a surveillance period of over 23 years, 136 tissue-confirmed incident cases of prostate cancer were identified. Their stored sera and those of 136 matched controls were measured for the following: 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, calcium, phosphorus, and parathyroid hormone. RESULTS: There were no notable differences between cases and controls in their median serum levels of the five laboratory measurements. Odds ratios (OR) for prostate cancer, based on the quartiles of serum levels in controls, were also determined. The ORs for the highest quartiles relative to the lowest were 0.8 (95 percent confidence interval [CI] = 0.4-1.8) for 25-hydroxyvitamin D and 1.0 (CI = 0.5-2.1) for 1,25-dihydroxyvitamin D. CONCLUSION: It is possible that the lack of sufficient numbers of study subjects with low vitamin D levels affected the results. Nonetheless, the findings suggest that there is a lack of a strong association between vitamin D and prostate cancer.

Age Distribution↗

PubMed1998

Diabetes induced by Coxsackie virus: initiation by bystander damage and not molecular mimicry.

Viral induction of autoimmunity is thought to occur by either bystander T-cell activation or molecular mimicry. Coxsackie B4 virus is strongly associated with the development of insulin-dependent diabetes mellitus in humans and shares sequence similarity with the islet autoantigen glutamic acid decarboxylase. We infected different strains of mice with Coxsackie B4 virus to discriminate between the two possible induction mechanisms, and found that mice with susceptible MHC alleles had no viral acceleration of diabetes, but mice with a T cell receptor transgene specific for a different islet autoantigen rapidly developed diabetes. These results show that diabetes induced by Coxsackie virus infection is a direct result of local infection leading to inflammation, tissue damage, and the release of sequestered islet antigen resulting in the re-stimulation of resting autoreactive T cells, further indicating that the islet antigen sensitization is an indirect consequence of the viral infection.

Amino Acid Sequence↗

PubMed1998

Screening for Helicobacter pylori in young dyspeptic patients referred for investigation--endoscopy for those who test negative.

BACKGROUND: Studies in young dyspeptic patients have suggested that screening strategies based on non-invasive H. pylori testing can reduce endoscopy workload by 25-40%. Such strategies usually propose that only H. pylori-positive individuals should undergo endoscopy. This approach may fail to diagnose idiopathic ulcers, ulcers in patients whose screening test is falsely negative and reflux disease. AIM: To investigate a hypothetical screening strategy in which endoscopy is initially performed only in H. pylori-negative dyspeptics. METHODS: Seventy-two consecutive patients under 45 years of age undergoing investigation for 'ulcer-like' dyspepsia had invasive and non-invasive determination of H. pylori status. Individuals found to be H. pylori-positive at endoscopy received 1 week of proton pump inhibitor-based triple therapy. H. pylori-negative individuals received therapy tailored to their diagnosis. Endoscopy was repeated in the positive group to confirm successful eradication. Results were analysed according to our strategy, i.e. serologically-positive patients would have received eradication therapy without endoscopy, but patients found to be negative would have been referred for endoscopy. RESULTS: According to the serology test there were 39 positive and 33 negative results. Symptoms failed to resolve during follow-up in nine of the serological positives despite successful eradication. There were also five false positives who were deemed likely treatment failures. Thus according to our strategy, these 14 serologically-positive patients would ultimately have required an endoscopy and the other 25 serologically-positive patients would have avoided an endoscopy, resulting in a 35% reduction in endoscopy usage in this population. In the serologically-negative group there were three cases of peptic ulcer disease where the test was falsely negative, but they were detected by the strategy. No cases of gastric malignancy were detected at endoscopy. Thus our strategy would have reduced initial endoscopy referrals by 35% in this selected population. CONCLUSION: A strategy of empirical H. pylori eradication therapy can safely reduce the requirement for endoscopy in young dyspeptic patients without sinister symptoms.

Adult↗

PubMed1998

Epoetin alfa and beta differ in their erythropoietin isoform compositions and biological properties.

Epoetin alfa and beta are the two forms of recombinant DNA-derived erythropoietin (rEPO), both synthesized in Chinese hamster ovary cells, which are used for the treatment of erythropoietin (EPO)-responsive anaemias. Several batches of each of these rEPOs were compared for differences in their EPO isoform compositions by isoelectric focusing (IEF) and in a range of lectin-binding assays, and for differences in their EPO activities by in-vivo and in-vitro mouse bioassays and by immunoassay. Epoetin beta was found to differ from epoetin alfa in containing: (a) a greater proportion of more basic isoforms, (b) a greater proportion of EPO binding to Erythrina cristagalli agglutinin (which binds N-glycans with nonsialylated outer Gal beta1-4GlcNAc moieties), and (c) isoforms with higher in-vivo:in-vitro bioactivity ratios. Epoetin beta also contained slightly more than epoetin alfa of EPO binding to Lycopersicon esculentum agglutinin (which binds N-glycans containing repeating Gal beta1-4GlcNAc sequences), to the leucoagglutinin of Phaseolus vulgaris (which binds tetraantennary and 2,6-branched triantennary N-glycans) and to Agaricus bisporus agglutinin (which binds Gal beta1-3GalNAc containing O-glycans). No differences were found between the two rEPOs in their binding to a further five lectins. The differences between the isoform composition of epoetin alfa and beta, and the smaller inter-batch differences appear to be due to differences in glycosylation. The higher murine in-vivo:in-vitro bioactivity ratio of epoetin beta compared to epoetin alfa could not be explained in terms of differences in their degrees of sialylation, but was consistent with differences in their pharmacokinetics and pharmacodynamics observed in human subjects. There have been no reports that epoetin alfa differs from epoetin beta in its clinical efficacy, but the differences between epoetin alfa and beta in some analytical systems suggest that there might be a need for separate international standards for these two types of rEPO.

Animals↗

PubMed1998

Communication about parental illness with children who have learning disabilities and behavioural problems: three case studies.

Parental illness can have a profound impact on family relationships and children's behaviour. The amount and nature of communication between parents and children about the illness can play an important role, both positively and negatively, in mediating the outcomes. When children have a disability, families can be reluctant to communicate with them about family difficulties. They are often concerned about the impact that parental unavailability may have on their child's life. This paper reports on three families in which the mother was diagnosed with breast cancer and one child in the family had a disability. The extent and specific characteristics of their communication about the maternal illness with their children, behavioural changes in the children, explanations of communication strategies and attributions of behavioural changes are described. Family coping strategies are examined with reference to Lazarus's process model of stress and coping and the use of either problem-focused or emotion-focused strategies. Implications for possible clinical interventions are proposed. In particular it is suggested that families be offered consultation about: what children might understand; ways in which to communicate effectively; and strategies for coping with the long-term implications of serious parental illness.

Adolescent↗

PubMed1998

Injection of T-cell receptor peptide reduces immunosenescence in aged C57BL/6 mice.

Previous studies established that retrovirally infected young mice produced large amounts of autoantibodies to certain T-cell receptor (TCR) peptides whose administration diminished retrovirus-induced immune abnormalities. C57BL/6 young (4 weeks) and old (16 months) female mice were injected with these same synthetic human TCR V beta 8.1 or 5.2 peptides. Administration of these autoantigenic peptides to old mice prevent immunosenescence, such as age-related reduction in splenocyte proliferation and interleukin-2 (IL-2) secretion. TCR V beta peptide injection into young mice had no effect on T- or B-cell mitogenesis and IL-4 production while modifying tumour necrosis factor-alpha (TNF-alpha), IL-6, and interferon-gamma (IFN-gamma) secreted by mitogen-stimulated spleen cells. TCR V beta injection also retarded the excessive production of IL-4, IL-6 and TNF-alpha induced by ageing. These data suggest that immune dysfunction and abnormal cytokine production, induced by the ageing process, were largely prevented by injection of selected TCR V beta CDR1 peptides.

Aging↗

PubMed1998

HREM and STEM of intergranular films at zinc oxide varistor grain boundaries.

Grain boundaries in model ZnO-Bi2O3 and ZnO-Bi2O3-CoO varistors and a commercial multicomponent varistor have been characterized by high-resolution electron microscopy (HREM) and scanning transmission electron microscopy (STEM), in order to determine the relationship between Bi grain boundary segregation and formation of thin intergranular films. By controlling Bi2O3 content, applied pressure and temperature, the grain boundary Bi excess has been systematically varied from nearly zero to GammaBi = 1 x 1015 cm-2 ( approximately 1 monolayer), as measured by HB 603 STEM using an area-scan method. HREM shows that intergranular amorphous films are clearly distinguishable in samples with GammaBi > 8 x 1014 cm-2. These films range in thickness, depending on the Bi excess, from 0.6 to 1.5 nm. Similar films of approximately 1 nm thickness are widely observed in the commercial varistor. The composition of the films is a ZnO-Bi2O3 solid solution, which is in all cases more enriched in ZnO than the bulk eutectic liquid. The Bi-doped grain boundaries in ZnO varistors therefore contain an intergranular amorphous film which has not only an equilibrium thickness, but also a distinct equilibrium composition.

Journal Article↗

PubMed1998

A role for the Pcl9-Pho85 cyclin-cdk complex at the M/G1 boundary in Saccharomyces cerevisiae.

PHO85 is a cyclin-dependent kinase (CDK) with roles in phosphate and glycogen metabolism and cell cycle progression. As a CDK, Pho85 is activated by association with Pho85 cyclins (Pcls), of which 10 are known. PCL1, PCL2 and PCL9 are the only members of the Pho85 cyclin family that are expressed in a cell cycle-regulated pattern. We found that PCL9 is expressed in late M/early G1 phase of the cell cycle and is activated by the transcription factor, Swi5. This pattern of regulation is different from PCL1 and PCL2, which are expressed later in G1 phase and are regulated primarily by the transcription factor SBF. Co-immunoprecipitation experiments using in vitro translated proteins showed that Pcl9 and Pho85 form a complex. Furthermore, immunoprecipitated Pcl9 complexes from yeast lysates were capable of phosphorylating the exogenous substrate Pho4. The Pcl9-associated kinase activity was dependent on PHO85, showing that Pcl9 and Pho85 form a functionally active kinase complex in vivo. Deletion of PCL9 in diploid cells caused random, rather than bipolar, budding in 18% of cells. In contrast, deletion of PCL2, the closest relative of PCL9, had no effect on the budding pattern. Deleting more members of the PCL1,2 subfamily (which includes PCL9) increased the percentage of random budding in the cell population. When all members of the PCL1,2 subfamily were deleted, 73% of cells budded randomly, a value similar to that obtained when the CDK partner PHO85 was deleted. Our results show that PCL9 and PHO85 form a functional kinase complex and suggest a role for Pho85 CDKs at the M/G1 boundary.

Blotting, Northern↗

PubMed1998

Inhibitory effect of sesquiterpene lactones from Saussurea lappa on tumor necrosis factor-alpha production in murine macrophage-like cells.

Total methanol extract of Saussurea lappa radix (Compositae) showed potent inhibitory effect on the production of tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, in murine macrophage-like cell (RAW264.7 cells) in our previous screening studies on 120 Korean medicinal plants. The activity-guided purification of the plant resulted in the isolation of three components. The chemical structures of the components isolated were established by spectroscopic analyses as sesquiterpene lactones [cynaropicrin (1), reynosin (2), and santamarine (3)]. These three compounds inhibited TNF-alpha production in a dose-dependent manner. The molar concentrations of cynaropicrin, reynosin, and santamarine producing 50% inhibition (IC50) of TNF-alpha production were 2.86 micrograms/ml (8.24 microM), 21.7 micrograms/ml (87.4 microM), and 26.2 micrograms/ml (105 microM), respectively. However, treatment with sulphydryl (SH) compounds such as L-cysteine, dithiothreitol, and 2-mercaptoethanol abrogated the inhibitory effect of cynaropicrin on TNF-alpha production. Therefore, we conclude that the principal inhibitory component of Saussurea lappa is cynaropicrin and its inhibitory effect is mediated through conjugation with SH-groups of target proteins.

Animals↗

PubMed1998

The conditional binomial test revisited for clinical trials.

McNemar's test is used to test the hypothesis that one treatment is better than another in a matched-pair design for binary outcomes. The conditional binomial test in such a matched-pair design is the exact McNemar test. However, in many clinical trials, one wants to establish equivalency between two treatments. We discuss how to use a conditional binomial test to establish equivalency between two treatments in a matched-pair design. Sample size and power determination for each conditional binomial test are calculated. Some statistical properties of the tests are analyzed through Monte Carlo simulation.

Binomial Distribution↗

PubMed1998

Recovery of an oligonucleotide using silver ions immobilized onto paramagnetic particles.

A 3'-GCCCCTTTTTAAAAACCCCG-5' oligonucleotide can be recovered from aqueous solution using paramagnetic particles containing immobilized silver ions. Binding and elution experiments were conducted by attaching either fluorescein isothiocyanate (FITC) to the 3'-end or Texas Red or fluorescein phosphoramidite (FAM) to the 5'-end of the oligonucleotide. For the 5'-end FAM labeled oligonucleotide, a binding constant of 4.2 x 10(7) was measured at pH 7 using phosphate buffer. The percent of bound FAM labeled oligonucleotide eluted from the paramagnetic particles were found to be 97% using an aqueous solution of thiodiglycol. While the FAM molecule by itself does not bind to the silver activated paramagnetic particles, the choice of fluorescent label affects binding affinities and elution recoveries.

Adsorption↗

PubMed1998

Molecular analysis of the PDS gene in Pendred syndrome.

Pendred syndrome is an autosomal recessive disorder characterized by the association between sensorineural hearing loss and thyroid swelling or goitre and is likely to be the most common form of syndromic deafness. Within the thyroid gland of affected individuals, iodide is incompletely organified with variable effects upon thyroid hormone biosynthesis, whilst the molecular basis of the hearing loss is unknown. The PDS gene has been identified by positional cloning of chromosome 7q31, within the Pendred syndrome critical linkage interval and encodes for a putative ion transporter called pendrin. We have investigated a cohort of 56 kindreds, all with features suggestive of a diagnosis of Pendred syndrome. Molecular analysis of the PDS gene identified 47 of the 60 (78%) mutant alleles in 31 families (includes three homozygous consanguineous kindreds and one extended family segregating three mutant alleles). Moreover, four recurrent mutations accounted for 35 (74%) of PDS disease chromosomes detected and haplotype analysis would favour common founders rather than mutational hotspots within the PDS gene. Whilst these findings demonstrate molecular heterogeneity for PDS mutations associated with Pendred syndrome, this study would support the use of molecular analysis of the PDS gene in the assessment of families with congenital hearing loss.

DNA Mutational Analysis↗

PubMed1998

Genome-wide search for asthma susceptibility loci in a founder population. The Collaborative Study on the Genetics of Asthma.

Founder populations offer many advantages for mapping genetic traits, particularly complex traits that are likely to be genetically heterogeneous. To identify genes that influence asthma and asthma-associated phenotypes, we conducted a genome-wide screen in the Hutterites, a religious isolate of European ancestry. A primary sample of 361 individuals and a replication sample of 292 individuals were evaluated for asthma phenotypes according to a standardized protocol. A genome-wide screen has been completed using 292 autosomal and three X-Y pseudoautosomal markers. Using the semi-parametric likelihood ratio chi2 test and the transmission-disequilibrium test, we identified 12 markers in 10 regions that showed possible linkage to asthma or an associated phenotype (likelihood ratio P < 0.01). Markers in four regions (5q23-31, 12q15-24.1, 19q13 and 21q21) showed possible linkage in both the primary and replication samples and have also shown linkage to asthma phenotypes in other samples; two adjacent markers in one additional region (3p24.2-22) showing possible linkage is reported for the first time in the Hutterites. The results suggest that even in founder populations with a relatively small number of independent genomes, susceptibility alleles at many loci may influence asthma phenotypes and that these susceptibility alleles are likely to be common polymorphisms in the population.

Adolescent↗

PubMed1998

Intakes of selected foods and beverages and the incidence of gastric cancer among the Japanese residents of Hawaii: a prospective study.

BACKGROUND: We report on the associations between the intake of certain foods and beverages and the incidence of gastric cancer in a cohort of 11,907 randomly selected Japanese residents of Hawaii (6297 women and 5610 men). METHODS: The daily intake of six beverages, cigarettes and alcohol and the weekly frequency of intake of 13 foods and food groups was estimated with a short food frequency questionnaire. Over an average follow-up period of 14.8 years, 108 cases of gastric cancer (44 women, 64 men) were identified via linkage to the Hawaii Tumor Registry. RESULTS: In gender-combined proportional hazards analyses, the consumption of fresh fruit seven or more times per week was associated with a significantly reduced risk of gastric cancer, compared to lower levels of consumption (relative hazard (RH): 0.6, 95% confidence interval (CI): 0.4-1.0, P = 0.03). The combined intake of fresh fruit and raw vegetables was inversely associated with the risk of gastric cancer in the total cohort, and among the men (P < 0.05). No significant relationships were found between gastric cancer incidence and the intake of pickled vegetables, miso soup, dried or salted fish, or processed meats among either gender. Compared to non-drinkers, men who drank one cup of coffee per day had a significantly elevated risk of gastric cancer (RH: 2.5, 95% CI: 1.0-6.1, P = 0.05), but there was no evidence of a dose-response relationship. Cigarette smoking and consumption of alcohol were not related to gastric cancer, in analyses restricted to the men. CONCLUSIONS: The results related to fruit and vegetable intake are consistent with an anti-nitrosating effect of these foods, while the unexpected association between coffee consumption and gastric cancer is difficult to explain and may represent a chance finding.

Beverages↗

PubMed1998

Multiple pigmented basal cell carcinomas.

Basal cell carcinoma is the most common of all skin cancers and the most prevalent one among Caucasians. Rarely, these tumors are seen in other races. We report a 77-year-old Korean woman who presented with multiple darkly pigmented enlarging nodules on her scalp, face, trunk, and extremities. The patient had first noted a 6-mm pigmented lesion on her left eyebrow 10 years previously. Since then, other lesions had appeared in many locations on her body. She had been otherwise healthy and without a history of exposure to arsenic or radiation. There was no family history of skin cancer, xeroderma pigmentosum, or basal cell nevus syndrome. On physical examination, multiple darkly pigmented dome-shaped papules and nodules were present on her scalp, face, right forearm, lower abdomen, and inguinal areas. They ranged in size from 0.5 mm to 2 cm. The larger ones showed central ulceration. Multiple biopsy specimens from different sites showed pigmented basal cell carcinomas. Clinically, there was no evidence of nevus sebaceus, xeroderma pigmentosum, basal cell nevus syndrome, or immunodeficiency. Clinical workup including chest radiography, abdominal ultrasound, bone scan, and brain computerized axial tomography scan did not demonstrate primary or secondary tumors. The results of serologic and hematologic tests were also within normal limits. This is an unusual case report of multiple pigmented basal cell carcinomas in an Asian woman without any predisposing risk factors.

Aged↗