Search PubMed⌕ Search

Biomedical subjects

C Lee

Publications and source records attributed to C Lee.

At least 577 records · Page 32Linked to original sources
PubMed1995

Regulation of proliferation and production of prostate-specific antigen in androgen-sensitive prostatic cancer cells, LNCaP, by dihydrotestosterone.

LNCaP is an androgen-sensitive human prostatic cancer cell line. The effect of androgen on these cells is characterized by a bell-shaped growth response and a dose-dependent induction of prostate-specific antigen (PSA) production. The present study was carried out to gain further insight into the effect of androgen on LNCaP. Cells were cultured in phenol red-free RPMI-1640 supplemented with 10% charcoal-stripped fetal bovine serum, with concentrations of dihydrotestosterone (DHT) ranging from 0-10(-7) M, in a 4-day culture system. A bell-shaped growth response was reproduced with a peak level of cell count at 10(-10) M DHT. PSA secretion from these cells did not increase significantly until the DHT level in the medium reached 10(-9) M. A progressive increase in PSA secretion was observed at higher DHT concentrations accompanied with a progressive decline in cellular proliferation. The results of immunocytochemical analysis of PSA localization indicated that the proportion of cells with positive staining for PSA also increased with increasing concentrations of DHT. Analysis of androgen receptors, as determined by both immunocytochemistry and Western blot analysis, showed a decline in nuclear androgen receptor at low concentrations of DHT and an increase in the amount of receptor protein at high concentrations. These results indicated that the androgen-induced bell-shaped growth response in LNCaP cells represented the manifestation of two different cellular events in dose-related manner: cellular proliferation at low DHT concentrations and increased production of PSA at high DHT concentrations.

Androgens↗
PubMed1995

Homolog-scanning mutagenesis of the parathyroid hormone (PTH) receptor reveals PTH-(1-34) binding determinants in the third extracellular loop.

To identify determinants in the rat PTH receptor critical for binding the agonist peptide, PTH-(1-34), we systematically replaced 12 segments (5-33 residues) of the receptor's extracellular surface with the corresponding segments of the homologous rat secretin receptor and screened the resulting mutants in COS-7 cells for altered PTH-(1-34) binding properties. Surface expression of mutant receptors was assessed by the binding of monoclonal antibody 12CA5 to the epitope (HA)-tagged receptors. Of the nine well expressed and therefore informative receptor mutants, four bound radiolabeled PTH-(1-34) at levels that were proportional to the corresponding levels of surface expression, whereas five mutants bound [125I]PTH-(1-34) to levels that were lower than predicted from the cell surface expression levels. These five mutations occurred at the extracellular (EC) end of transmembrane domain 1, the carboxy-terminal portion of the first EC loop, the second EC loop, and the third EC loop. We selected for further fine structure analysis the third EC loop; two specific residues, Trp-437 and Gln-440, were identified at which mutations caused 9- to 16-fold reductions in PTH-(1-34)-binding affinity. The same mutations had little or no effect on the binding affinity of PTH-(3-34). This study provides new information on the location of PTH receptor regions important for high affinity agonist binding and identifies two residues in the third extracellular loop which may contribute to interactions involving the hormone's critical amino terminus.

Amino Acid Sequence↗
PubMed1995

Hydroxyl radical-mediated reduction of Ca(2+)-ATPase activity of masseter muscle sarcoplasmic reticulum.

To understand the effect of oxygen free radicals on Ca(2+)-ATPase, we used sarcoplasmic reticulum (SR) microsomes of canine masseter muscle as a model system in which to explore the effects of oxidation on a biological membrane, and we investigated the effect of hydroxyl radicals (.OH) generated from Fenton's reagent (H2O2/FeSO4). H2O2 (10 mM) alone had no effect on Ca(2+)-ATPase activity; in the presence of FeSO4 (0.2 mM), H2O2 inhibited the enzyme activity. Oxygen free radical species generated from H2O2/FeSO4 under the conditions employed in the Ca(2+)-ATPase assay were verified by highly sensitive electron spin resonance spectroscopy and the spin-trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) in the absence of SR vesicles; the 1:2:2:1 quartet (AN = A beta H = 1.49 mT), characteristic of the DMPO-OH spin adduct, was observed. The Ca(2+)-ATPase activity was inversely correlated with the calculated signal intensity of DMPO-OH, which is indicative of the amount of .OH radical generated. The effect of Fenton's reagent was effectively inhibited by catalase, dimethylsulfoxide, and dimethylthiourea; the effect was also inhibited by sulfhydryl (SH) group reducing agents, cysteine and dithiothreitol. The SH group modifying agents, p-chloromercuric benzoate and 5,5'-dithiobis(2-nitrobenzoic acid) depressed Ca(2+)-ATPase activity; the effects of the SH group modifying agents used were potentiated in the presence of Fenton's reagent. It is suggested that .OH radical-induced oxidant injury may be caused primarily by modification of the key SH group(s) on the ATPase molecule of masseter muscle SR vesicles.

Adenosine Triphosphatases↗
PubMed1995

Association of Bacteroides fragilis with childhood diarrhea.

Enterotoxigenic strains of Bacteriodes fragilis (ETBF) have recently been found to be associated with diarrheal illness in Apache and Bangladeshi children. This study was conducted to define the role of ETBF in diarrhea of children in an urban setting. Fecal specimens from 991 children with diarrhea and 581 asymptomatic age-matched controls were cultured for B. fragilis (BF). The isolates were tested for enterotoxin production using a human colonic epithelial cell line. BF was isolated from 318 (32.1%) of the patients and 123 (21.2%) of the controls (p < 0.001). In children < 1 year old which comprised about 50% of both patients and controls, the BF isolation rates were comparable (26.5% vs 25.7%; p = 0.812), contrasting with the significant difference in isolation rates for children > or = 1 year (37.6% vs 16.5%; p = < 0.001). Overall, ETBF were identified in 4.4% of patients and 3.1% of controls (p = 0.2). However, ETBF were significantly associated with diarrheal disease in children 1-5 years (5.4% vs 1.8%; p = 0.033) and 1-10 years (4.8% vs 1.5%; p = 0.021) in age. ETBF were isolated the year round and comprised 14.4% and 15% of the BF isolated from the patients and controls, respectively, suggesting that part of the indigenous BF are inherently enterotoxin producers. In this study, BF and ETBF were associated with diarrheal illness in children 1-10 years old.

Age Distribution↗
PubMed1995

Multiplicative factors for estimation of daily milk and component yields from single morning or afternoon tests.

Prediction of daily yield from single a.m. or p.m. milkings requires factors that are the reciprocal of the proportion of total yield expected from single milkings given the milking interval. Further adjustments to estimated milk yield account for DIM. Factors used by the Cornell Dairy Records Processing Lab were estimated from data collected from August 1983 to November 1984. These factors appear to be biased. Inconsistent estimates of daily yield were observed monthly. New factors were developed using recent data. Factors from a.m. milkings for milk and protein yield were smaller than those currently in use. The reverse was true for fat yield. Covariants for DIM were larger than those currently used. Differences were observed when factors using data with known and assumed milking intervals were compared. Factors for a.m. milkings with known intervals were smaller than those from p.m. milkings with the same known intervals. Use of covariants for DIM were compared with covariants for single milk yield. The latter explained more variation in yield. Factors were tested on independent data. New factors with covariants for single milk yield performed best for estimation of total daily yield.

Animals↗
PubMed1995

Alveolar cleft bone grafts: results and imprecisions of the dental radiograph.

Alveolar cleft bone grafts customarily have been evaluated by one-dimensional dental radiographic measurements. Based on the dental radiograph, remarkable successes with just a single bone graft have been reported in the literature. At the Montreal Children's Hospital, the experience with 101 alveolar bone grafts in 62 cleft lip and palate patients was retrospectively reviewed to determine (1) the precision of dental radiographs at evaluating the clinical outcome, (2) the effect of dental maturation on alveolar bone grafts, and (3) the effect of augmentation bone grafts. The dental radiograph significantly overestimated the number of clefts that could be managed orthodontically (p < 0.01, McNemar's test) and thus poorly prognosticated the ability to achieve bony obliteration of the alveolar cleft and orthodontic closure of the dental gap. Bone grafts performed during the preeruptive canine dentition yielded significantly better results (p < 0.05, chi-squared test). With each subsequent augmentation bone-graft procedure performed, there existed a trend toward improved dental arch stability and radiographic and clinical outcomes.

Adolescent↗
PubMed1995

Etiology of benign prostatic hyperplasia.

Benign Prostatic Hyperplasia (BPH) is the most common neoplastic condition that afflicts men, and it constitutes a major factor impacting the health of the American male. This article reviews voiding dysfunction and the role of aging, the testis, and androgen in the development of BPH. Emphasis is placed on new concepts in the basic aspects of BPH etiology as a result of recent investigations.

Aging↗
PubMed1995

Screening for hepatocellular carcinoma in chronic carriers of hepatitis B virus: incidence and prevalence of hepatocellular carcinoma in a North American urban population.

OBJECTIVE: To prospectively determine the prevalence and annual incidence of hepatocellular carcinoma in hepatitis B carriers in a heterogeneous urban North American population and to assess the diagnostic accuracy of tests used for screening for this cancer. DESIGN: Prospective cohort study of 1,069 chronic carriers of hepatitis B virus using screening with alpha-fetoprotein alone or in combination with ultrasonography every 6 months. RESULTS: The mean age of the cohort was 39 +/- 12 years (+/- SD), 65% were men, 71% were Asians. At the first screening visit, serum alpha-fetoprotein was > or = 20 micrograms/L in 4%. In those subjects who were also screened by ultrasonography during the first visit, 9% were found to have focal lesions. Only 3 subjects were found to have hepatocellular carcinoma at the first screening, giving a prevalence of 281/100,000 chronic carriers of hepatitis B virus. The cohort was followed for 2,340 person-years (mean, 26 months follow-up, with a range from 6 to 60 months). During this period, 11 more subjects, 10 men and 1 woman, were diagnosed to have hepatocellular carcinoma (annual incidence, 470/100,000). In men only, the annual incidence was 657/100,000. During the study, 5 subjects died from hepatocellular carcinoma (annual mortality rate, 214/100,000). Sensitivity and specificity of serum alpha-fetoprotein > 20 micrograms/L were 64.3% and 91.4%, respectively. For ultrasonography, sensitivity was 78.8% and specificity 93.8%. CONCLUSIONS: These data suggest that the incidence and prevalence of hepatocellular carcinoma in hepatitis B carriers in our area, an urban North American setting, are as high as in countries where hepatitis B is endemic. Current screening tests have significant false-positive and false-negative rates raising questions about the cost-benefit of screening for hepatocellular carcinoma in our study population.

Adult↗
PubMed1995

Disseminated disease due to Mycobacterium avium complex in AIDS.

We retrospectively analysed 46 cases of disseminated infection with Mycobacterium avium complex (MAC) within a cohort of 702 HIV-infected patients in Edinburgh. Clinical features were compared with case-matched controls (AIDS cases without disseminated MAC), and survival and progression times were controlled for confounding variables that influence survival. Disseminated MAC was diagnosed antemortem in 18% of AIDS patients, and was the AIDS-defining diagnosis in 6% of all AIDS cases. Concomitant colonization of respiratory and gastrointestinal tracts was common (61% and 48%, respectively). In 58% of cases, CD4+ counts were < 10 cells/mm3 (median 6 cells/mm3). Weight loss, anaemia, leucopenia, and elevated liver transaminases and alkaline phosphatase were significantly more common among cases than controls. Therapy was given in 74%, and not tolerated in 32%. Following AIDS diagnosis, disseminated MAC incidence was 14% at one year, 25% at 2 years and 36% at 3 years. Median survival after disseminated MAC diagnosis was 6 months, with shorter survival in untreated cases. However, overall survival from AIDS diagnosis was not significantly different between patients who did or did not develop disseminated MAC. Disseminated MAC contributes significantly to AIDS morbidity, and its incidence increases with prolonged AIDS survival. Although survival following diagnosis is short, the development of disseminated MAC in AIDS probably does not affect overall survival. In cohorts with a low incidence, an alternative to prophylaxis might be surveillance and early diagnosis.

AIDS-Related Opportunistic Infections↗
PubMed1995

The effects of theophylline on mucosal inflammation in asthmatic airways: biopsy results.

Theophylline, a nonspecific phosphodiesterase inhibitor, has only recently been reconsidered as a potential anti-inflammatory drug. Its ability to inhibit late asthmatic responses has pointed to possible inhibition of mechanisms regulating the influx and activity of inflammatory cells into the airways. Increasing evidence points to an anti-inflammatory action of theophylline at doses lower than those necessary for a bronchodilator effect. Withdrawal of theophylline from regular treatment results in an increase both in CD4+ and CD8+ T-cells in the bronchial mucosa and a concomitant decrease in the blood, suggesting that theophylline prevents T-cell trafficking from blood into the airways. Furthermore, pretreatment with theophylline significantly attenuates the influx of eosinophils into the airways associated with an allergen-induced late asthmatic response. In keeping with these observations, in a double-blind, placebo-controlled trial involving mild to moderately severe atopic asthmatics, treatment with theophylline resulted in a significant reduction in the numbers of epithelial CD8+ T-cells. In addition, the numbers of cells containing cytokines, interleukin 4 and 5 (IL-4 and IL-5), decreased in the theophylline-treated group and increased in the placebo-treated group, with the difference between the changes being significant. It would, therefore, appear that theophylline may contribute to asthma control due to its ability to reduce the suppressor/cytotoxic T-cells and cytokines which are relevant to allergic mucosal responses.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

Effects of CD34+ selection and T cell immunodepletion on cord blood hematopoietic progenitors: relevance to stem cell transplantation.

Cord blood (CB) has been used recently for stem cell transplantation. We have investigated two different approaches to deplete CB samples of T cells capable of mounting graft-vs.-host disease (GVHD). The methods used were selection of CD34+ cells using avidin-biotin columns (CellPro) and T cell immunodepletion with T10B9 monoclonal antibody (mAb) plus complement. Using the avidin-biotin columns, 10.3% of the original CD34+ cells were recovered. Although this technique yielded a population containing 60 +/- 5.5% CD34+ cells, about 1 log of CFU-GM progenitors were lost. In contrast, after the T10B9 mAb and complement immunodepletion, 75 +/- 19% and 62 +/- 7% of the CD34+ cells and CFU-GM were recovered, respectively. T cell depletion was 3.6 logs using the CellPro columns and 2.2 logs after immunodepletion. To investigate whether cell losses following T cell depletion could be overcome by ex vivo expansion, cells were cultured in the presence of recombinant human interleukin-3 (rhIL-3) and recombinant human c-kit ligand (stem cell factor [rhSCF]) for 7 days. There were 14- and six-fold expansions in the number of progenitors recovered after CellPro and immunodepletion, respectively. To asses the engraftment potential of expanded cells, we used a murine transplantation model in which the presence of human cells was identified by the anti-CD45 mAb. Cells expanded in vitro engrafted in irradiated BNXid mice as efficiently as nonexpanded cells, suggesting that expansion did not affect their transplantability. This study shows that both techniques resulted in significant T cell depletion of CB. Furthermore, in vitro expansion could overcome cell losses sustained during the separation techniques without impairing the engraftment potential of the expanded cells.

Animals↗
PubMed1995

Modern treatment of haemophilia.

Many rapid advances have been made in the diagnosis and therapy of haemophilia. Nevertheless, the condition still poses problems and challenges (e.g., joint disease, transfusion-transmitted diseases, inhibitors, provision of care in developing countries, and education and cost issues). WHO and the World Federation of Hemophilia held a joint meeting in Geneva, on 21-23 March 1994, to discuss and review current and future approaches to the management of haemophilia and its complications, including prospects for genetic technology and gene therapy in developed and developing countries. The present review article summarizes the discussions and recommendations made by the participants.

Consumer Product Safety↗
PubMed1995

Testing homology modeling on mutant proteins: predicting structural and thermodynamic effects in the Ala98-->Val mutants of T4 lysozyme.

Backgound. Current approaches to homology modeling predict how amino acid substitutions will alter a protein's structure, primarily by modeling sidechain conformations upon essentially immobile backbone frameworks. However, recent crystal structures of T4 lysozyme mutants reveal significant shifts of the mainchain and other potentially serious problems for sidechain rotamer-based modeling. This paper evaluates the accuracy of structural and thermodynamic predictions from two common sidechain modeling approaches to measure errors caused by the fixed-backbone approximation. Results. Tested on a series of T4 lysozyme mutants, this sidechain rotamer library approach did not handle mainchain shifts well, correctly predicting the sidechain conformations of only two of six mutants. By contrast, allowing sidechains to move more flexibly appeared to compensate for the rigidity of the mainchain and gave reasonably accurate coordinate predictions (rms errors of 0.5-1.0 &angst; for each mutated sidechain), better on average than 90% of possible conformations. The calculated packing energies correlated well with experimental stabilities (r2=0.81) and correctly captured the cooperative interactions of several neighboring mutations. Conclusion. Mutant modeling can be relatively accurate despite the fixed-backbone approximation. Mainchain shifts (0.2-0.5 &angst;) cause increased sidechain coordinate errors of 0.1-0.8 &angst;, torsional errors of 10-30&deg;, and exaggerated strain energy for overpacked mutants, compared with the same calculations performed with the correct mutant backbones.

Journal Article↗
PubMed1994

Quantitative capillary gel electrophoresis assay of phosphorothioate oligonucleotides in pharmaceutical formulations.

Quantitative capillary gel electrophoresis (QCGE) has been developed for the accurate quantitation of a 21-mer phosphorothioate oligonucleotide, ISIS 2922, and its degradation products in an intravitreal formulation. The electrokinetic mode of injection employed by CGE necessitates formulation of the external reference standard in a sample matrix similar to that of the drug product and the use of an internal standard for improved accuracy and precision. The analytical method detailed in this paper has demonstrated the necessary accuracy, precision, linearity, range, selectivity and ruggedness for use in routine drug product analysis and stability monitoring of phosphorothioate oligonucleotides.

Capillary Action↗
PubMed1994

A brief introduction to the critical reading of the clinical literature.

Clinicians are bombarded by reports of new diagnostic tests or treatments for patients with spine problems. To provide the best possible patient care, clinicians need to be able to critically appraise the results of such studies for validity and relevance to patient care. Important questions to be asked of any description of diagnostic or treatment studies are the following questions: 1) Are the patients described in detail so that you can decide whether they are comparable to those that you see in your practice? 2) Are the treatments or assessments described well enough so that you could provide the same for your patients? 3) Was a clinically relevant endpoint measured? 4) Is there an appropriate comparison group? 5) Are potential sources of bias appropriately attended to? 6) Are the results clinically significant?

Humans↗