Search PubMed⌕ Search

Biomedical subjects

C K Lee

Publications and source records attributed to C K Lee.

At least 127 records · Page 7Linked to original sources
PubMed1999

Langerhans' cell histiocytosis of the spine. Analysis of twenty-three cases.

STUDY DESIGN: Retrospective review of clinical and radiologic data in four major tertiary referral centers. OBJECTIVES: To report clinical and roentgenographic findings, to evaluate the results of various treatment methods, and to propose a protocol for management. SUMMARY OF BACKGROUND DATA: Langerhans' cell histiocytosis of the spine is a rare condition, and therefore, appropriate management is still controversial. METHODS: Clinical and roentgenographic findings of 38 vertebral lesions of 23 children, with average follow-up of 5.4 years, were investigated. This is the most extensive report apparent in the literature to date. The results of treatment were assessed clinically and radiologically. Anterior vertebral body height was measured sequentially to evaluate reconstitution of the vertebral body. RESULTS: The last follow-up examination demonstrated no clinical evidence of disease in all patients, regardless of treatment method. Neurologic deficits developed in four patients, but they completely disappeared. Satisfactory restoration of height was demonstrated in all except five vertebrae: one that had collapsed maximally when the patient was more than 15 years of age and four that had been fused anteriorly or posteriorly. Unsatisfactory results were also seen in a patient with progressive scoliosis and in one with an irregular endplate with disc space narrowing. Both of these complications developed after curettage. CONCLUSIONS: For treatment of single or dual spinal lesions, observation with or without bracing seems to be sufficient. In patients with multifocal lesions, chemotherapy produces good results. For treatment of neurologic deficit, low-dose radiotherapy is favored. Patients who underwent surgery--especially curettage and anterior fusion--had the worst outcome.

Adolescent↗
PubMed1999

Immunization of rhesus monkeys with a mucosal prime, parenteral boost strategy protects against infection with Helicobacter pylori.

Rhesus monkeys were immunized with recombinant Helicobacter pylori urease vaccine given solely by the parenteral route or preceded by a priming dose given by the oral route. Two groups of monkeys received parenteral urease with either a synthetic glycolipid adjuvant (Bay) or aluminum hydroxide (alum) as adjuvants. A third group of monkeys received a priming dose of oral urease given with the mucosal adjuvant LT (Escherichia coli heat labile enterotoxin), followed by parenterally administered booster doses of urease adsorbed to alum. Monkeys receiving placebo served as controls. The monkeys received a total of 4 doses of vaccine with the first 3 doses given every 3 weeks and the last booster dose administered 14 weeks later. The monkeys were challenged orally with H. pylori one week after the last vaccine dose and euthanized 10 weeks after challenge, at which time, their stomachs were collected for determination of bacterial colonization and histopathology. Monkeys primed with the oral vaccine and boosted with the parenteral vaccine showed a statistically significant reduction in bacterial colonization when compared to sham-immunized control animals (P = 0.05; Wilcoxon rank sums test). Monkeys receiving parenteral only regimes of urease plus Bay or alum showed no difference in bacterial colonization compared with sham-immunized controls (P = 1.00 and P = 0.33, respectively). The mucosal prime-parenteral boost regime did not cause gastropathy. There was no difference in any of the 3 treatment groups with respect to gastric epithelial changes compared to control animals. There was also no difference in the type and extent of gastric inflammatory cell infiltrates between animals vaccinated by the mucosal prime-parenteral boost strategy and sham immunized controls. However, monkeys receiving the two parenteral-only regimens had slightly elevated gastritis scores.

Adjuvants, Immunologic↗
PubMed1999

Immunization with recombinant Helicobacter pylori urease decreases colonization levels following experimental infection of rhesus monkeys.

Rhesus monkeys, naturally colonized with H. pylori as indicated by culture and histology were immunized with either 40 mg recombinant H. pylori urease administered orally together with 25 microg Escherichia coli heat-labile enterotoxin (LT) or immunized with LT alone. An initial 6 doses were administered over an 8 week period. All five vaccinated monkeys had a greater than two-fold rise in urease-specific serum IgG and IgA level and urease-specific salivary IgA was induced in 3 of 5 vaccinated animals after 6 or 7 doses of vaccine. Vaccination had no measurable therapeutic effect on H. pylori colonization. H. pylori was eradicated from these monkeys with a course of antimicrobials plus omeprazole, a 7th vaccine dose was given (10 months after the 6th dose) and they were rechallenged with H. pylori. Necropsy was performed 23 weeks after rechallenge and H. pylori colonization was determined by histological examination of 12 individual gastric sites. A significant reduction in colonization (p < or = 0.0001; Friedman's analysis of variance) was found in the vaccinated animals. Histopathologic examination of necropsy tissues also revealed a trend towards reduced gastritis and epithelial alterations in the vaccinated group compared to animals receiving LT alone. This study provides the first evidence for effective vaccination of nonhuman primates against H. pylori, and preliminary evidence that a reduction in bacterial density attributable to immunization may lessen gastric inflammation.

Adjuvants, Immunologic↗
PubMed1999

Oral immunization with recombinant Helicobacter pylori urease confers long-lasting immunity against Helicobacter felis infection.

Recombinant Helicobacter pylori urease (rUre) has been shown to confer protection against challenge with Helicobacter felis in mice. The purpose of the present study was to examine duration of the immune response and long-term protective efficacy of immunization with rUre. Swiss Webster mice were orally immunized four times at weekly intervals with 100 microg rUre plus 5 microg heat-labile enterotoxin of Escherichia coli (LT) adjuvant, or with LT only. At 4, 10, 20 or 40 weeks post immunization, 25 rUre-immunized mice and control mice were challenged with H. felis and sacrificed at 2 or 10 weeks post-challenge. H. felis infection was assessed by gastric urease assay and by histology. Anti-H. pylori urease specific antibody levels were measured in serum and saliva both pre- and post-challenge. Over the 40 week time period, the infection rates in rUre-immunized mice were significantly lower than those in controls (p < 0.05) as assessed by gastric urease activity. Protection ranged from 79 100% at 2 weeks post-challenge and 63-78% at 10 weeks post-challenge. Gastric bacterial density in rUre-immunized mice was significantly lower than that of controls (p < 0.03) as determined by histologic assessment. Anti-urease antibody levels remained elevated in the serum and mucosal compartments at 39 weeks following immunization. This study shows that immunization with rUre plus LT results in long-lasting protective immunity against challenge with H. felis.

Adjuvants, Immunologic↗
PubMed1999

Essential role of STAT3 for embryonic stem cell pluripotency.

Propagation of mouse embryonic stem (ES) cells in vitro requires exogenous leukemia inhibitory factor (LIF) or related cytokines. Potential downstream effectors of the LIF signal in ES cells include kinases of the Src, Jak, and mitogen-activated protein families and the signal transducer and transcriptional activator STAT3. Activation of nuclear STAT3 and the ability of ES cells to grow as undifferentiated clones were monitored during LIF withdrawal. A correlation was found between levels of STAT3 activity and maintenance of an undifferentiated phenotype at clonal density. In contrast, variation in STAT3 activity did not affect cell proliferation. The requirement for STAT3 was analyzed by targeted mutagenesis in ES cell lines exhibiting different degrees of LIF dependency. An insertional mutation was devised that abrogated Stat3 gene expression but could be reversed by Cre recombination-mediated excision. ES cells heterozygous for the Stat3 mutation could be isolated only from E14 cells, the line least dependent on LIF for self-renewal. Targeted clones isolated from other ES cell lines were invariably trisomic for chromosome 11, which carries the Stat3 locus, and retained normal levels of activated STAT3. Cre-regulated reduction of Stat3 gene copy number in targeted, euploid E14 clones resulted in dose-dependent losses of STAT3 activity and the efficiency of self-renewal without commensurate changes in cell cycle progression. These results demonstrate an essential role for a critical amount of STAT3 in the maintenance of an undifferentiated ES cell phenotype.

Animals↗
PubMed1999

Cloning thymic precursor cells: demonstration that individual pro-T1 cells have dual T-NK potential and individual pro-T2 cells have dual alphabeta-gammadelta T cell potential.

Thymic progenitors have the capacity to generate alphabeta T cells, gammadelta T cells, and NK cells. To determine whether these three lineages derive from a single precursor cell or from different precursors, a procedure was developed for cloning precursor cells from mouse embryonic thymus. The progeny of each pro-T cell clone were then tested for the potential to generate alphabeta, gammadelta, and NK cells. Of these precursor clones, about half displayed dual potential, developing into either T cells or NK cells, demonstrating the existence of a common T/NK precursor cell in the thymus. The other half of the clones were restricted to T cell development. No precursor clones were restricted to NK development. The common T/NK precursors were shown to be of the pro-T1 (CD25(-)) stage whereas the T-restricted precursors were shown to be of the later pro-T2 (CD25(+)) stage. Both alphabeta and gammadelta T cells were generated from all clones derived from either pro-T1 or -T2 precursors. This shows that commitment of a cell to the alphabeta versus gammadelta lineages does not precede rearrangement of the TCR genes (which occurs immediately after the pro-T2 stage).

Animals↗
PubMed1999

Outcome of Chinese patients with chronic myeloid leukaemia (CML) underwent allogeneic bone-marrow transplantation (BMT).

UNLABELLED: Clinical studies have shown that patients with chronic myeloid leukaemia (CML) treated with allogeneic bone-marrow transplantation (BMT) experience not only prolonged disease-free survival but also complete cure in some. Therefore, we followed a cohort of 81 Chinese patients who received allogeneic BMT. PATIENTS AND METHODS: The donors were either relatives (65 siblings, 1 parent) or unrelated volunteers (15). BMT was performed at a median interval of 11.6 months from diagnosis of CML, and the stages of disease before BMT were: first chronic phase (60 patients), accelerated or second chronic phase in (10 patients), and blastic crisis (11 patients). Three conditioning regimens were employed: Bu-Cy, Cy-TBI, or Bu-Cy-TBI. Standard cyclosporin and short methotrexate protocol were used for acute graft-versus-host disease (GvHD) prophylaxis. RESULTS: There were five graft failures with three after related BMT. Patients after related or unrelated BMT had a comparable rate of neutrophil recovery (median = 22 days), but significant delay in platelet recovery occurred after unrelated BMT (median = 34 vs. 20 days, P < 0.05). The latter also had higher incidence of acute GvHD (73% vs. 41%, P < 0.05), although the incidence of chronic GvHD was not different between groups. At a median follow-up of 43.5 months, patients after related BMT had a significantly better rate of disease-free survival (68% vs. 37.3%, P < 0.05) and overall survival (81% vs. 38.9%, P < 0.05) at 4 years. Subgroup analysis of patients after related BMT showed the outcome was better when they were transplanted at first chronic phase. Multivariate analysis showed that advanced disease (RR = 2.01, 95% CI = 1.48-2.73) significantly worsened the outcome of BMT, whereas the presence of chronic GvHD had a protective effect against relapse and survival (RR = 0.09, 95% CI = 0.02-0.38). CONCLUSION: Allogeneic BMT is a curative form of treatment for patients with CML. Treatment outcome is best for those who undergo transplants from HLA-matched siblings during the first chronic phase.

Acute Disease↗
PubMed1999

Advanced stage and unfavorable Hodgkin's disease in the Chinese-a 20-year experience.

We retrospectively analyzed 57 patients with advanced stage (stage III/IV) or unfavorable (presence of B symptoms or bulky disease) Hodgkin's disease from January 1977 to December 1997. There were 29 male and 28 female patients. The median age was 27 years old (range, 13-59). Lactate dehydrogenase levels ranged from 104 units/l to 2320 units/l (median, 433). Eighteen (31.6%), 13 (22.8%), and 26 (45.6%) patients had stage II bulky, stage III, and stage IV disease, respectively. Twenty-five (44%) patients had B symptoms. One (1.8%), 3 (5.3%), 36 (63.2%), and 17 (29.8%) had lymphocyte predominant, lymphocyte depleted, nodular sclerosis, and mixed cellularity histology, respectively. Chemotherapy regimens included mechlorethamine, vincristine, procarbazine, prednisone (MOPP) (n = 9), adriamycin, bleomycin, vinblastine, dacarbazine (ABVD) (n = 23), MOPP alternating with ABVD (n = 13), and COPP-ABV hybrid (n = 12). Complete remission was achieved in 47 (82.4%) patients. Eleven patients (23%) relapsed after the first complete remission and four (36%) attained a second complete remission with salvage chemotherapy. Projected overall survival was 69.0% at 10 years and 20 years. Disease-free survival rates were 71% at 10 years and 20 years. Of the potential prognostic factors analyzed (age, sex, stage, lactate dehydrogenase, serum albumin level, regimen, B symptoms and bulky disease) by using the Cox regression model, only a low albumin level was found to adversely affect overall survival (P = 0.003). In conclusion, despite the relative low incidence of Hodgkin's disease in Hong Kong Chinese, the treatment outcomes in patients with advanced stage or unfavorable Hodgkin's disease is comparable to Caucasian patients.

Adolescent↗
PubMed1999

An antiviral furanoquinone from Paulownia tomentosa Steud.

A methanol extract of the stem bark of Paulownia tomentosa showed antiviral activity against poliovirus types 1 and 3. Sequential liquid-liquid extraction with n-hexane, chloroform and water, and a silicagel column chromatography resulted in the purification of a compound. The compound was identified as methyl-5-hydroxy-dinaphthol[1,2-2',3']furan-7,12-dione-6-carbox yla te on the basis of spectroscopic data. The component caused a significant reduction of viral cytopathic effect when it was subjected to a standard antiviral assay by using HeLa cells. The EC(50) of the compound against poliovirus type 1 strain Brunhilde, and type 3 strain Leon were 0.3 microg/mL and 0.6 microg/mL, respectively.

Antiviral Agents↗
PubMed1999

Direct ex vivo analysis of hepatitis B virus-specific CD8(+) T cells associated with the control of infection.

BACKGROUND & AIMS: Cytotoxic T cells have been suggested to be responsible for lysis of hepatitis B virus (HBV)-infected hepatocytes and control of virus infection. The frequency, kinetics, phenotype, and capacity for clonal expansion of circulating HBV-specific CD8 cells were analyzed directly in patients with acute HBV infection to clarify their pathogenetic role. METHODS: Three HLA-A2 peptide tetramers able to visualize HBV core, envelope, and polymerase epitope-specific cytotoxic T lymphocytes were synthesized and used for flow cytometric analysis of antigen-specific populations. RESULTS: Tetramer-positive cells specific for the core 18-27 epitope were found at a higher frequency than those specific for polymerase 575-583 and envelope 335-343 epitopes in most patients with acute HBV. The number of HBV-specific CD8 cells was highest during the clinically acute stage of infection and decreased after recovery. These cells expressed an activated phenotype and had an impaired capacity to expand in vitro and to display cytolytic activity in response to peptide stimulation. Recovery of these functions was observed when the frequency of specific CD8 cells decreased, coincident with a progressive decrease in their expression of activation markers. CONCLUSIONS: This study provides the first ex vivo evidence that the highest frequency of circulating HBV-specific CD8 cells coincides with the clinically acute phase of hepatitis B. These cells exhibit an activated phenotype with limited further proliferative capacity that is restored during recovery.

Adult↗
PubMed1999

Prevention of ultraviolet radiation-induced suppression of contact hypersensitivity by Aloe vera gel components.

We have recently reported that Aloe vera gel contains small molecular weight immunomodulators, G1C2F1, that restore ultraviolet B (UVB)-suppressed accessory cell function of epidermal Langerhans cells (LC) in vitro. In the present study we evaluated the UVB-protective activity of G1C2F1 in vivo. Exposure of the shaved abdominal skin of mice to 2.4 KJ/m2 of UVB radiation resulted in suppression of contact sensitization through the skin to 41.1%, compared to normal unirradiated skin. Topical application of G1C2F1 immediately after irradiation reduced this suppression significantly. The percentage recovery of UVB-suppressed contact hypersensitivity (CHS) response was 52.3, 77.3, and 86.6% when the irradiated skin was treated once with 0.1, 0.5, and 2.5 mg/ml of G1C2F1-containing cream, respectively. G1C2F1 did not show nonspecific stimulatory activity on CHS response. The present study, together with the previous observation, show that Aloe vera gel contains small molecular weight immunomodulators that prevent UVB-induced immune suppression in the skin by restoration of UVB-induced damages on epidermal LC.

Adjuvants, Immunologic↗
PubMed1999

Outcome of epithelial ovarian cancer in women under 40 years of age treated with platinum-based chemotherapy.

We retrospectively investigated the outcome of ovarian cancer in women aged less than 40 years treated in three randomised phase III studies of platinum-based chemotherapy. 624 patients had invasive epithelial ovarian cancer. A Cox proportional hazard model was used to study prognostic variables. 29 women (5%) were under 40 years of age. Stage, histological grade and amount of residual disease were significantly worse in women aged > or = 40 years. Median follow-up was 66.7 months. At 5 years 65% of women below 40 years of age were alive compared with 20% of older women (95% confidence interval (CI) of the difference 27.1-63.0). The progression-free interval was 59% versus 16% (95% CI 24.3-60.8). No patient under 40 years of age relapsed after 18 months. Age > or = 40 years was a poor prognostic variable, particularly for serous tumours, the commonest subtype in younger women (hazard ratio (HR): 3.33). Other prognostic factors were Eastern Cooperative Oncology Group (ECOG) performance status (HR: 1.25), presence of residual disease (HR: 1.43), histological grade (HR: 1.36) and International Federation of Gynaecology and Obstetrics (FIGO) stage (HR: 1.47). These results suggest that there are biological differences in the behaviour of serous carcinoma of the ovary in women of reproductive age compared with older women.

Adolescent↗
PubMed1999

Prevalence of suicide ideation and suicide attempts in nine countries.

BACKGROUND: There are few cross-national comparisons of the rates of suicide ideation and attempts across diverse countries. Nine independently conducted epidemiological surveys using similar diagnostic assessment and criteria provided an opportunity to obtain that data. METHODS: Suicide ideation and attempts were assessed on the Diagnostic Interview Schedule in over 40000 subjects drawn from the United States, Canada, Puerto Rico, France, West Germany, Lebanon, Taiwan, Korea and New Zealand. RESULTS: The lifetime prevalence rates/100 for suicide ideation ranged from 2.09 (Beirut) to 18.51 (Christchurch, New Zealand). Lifetime prevalence rates/100 for suicide attempts ranged from 0.72 (Beirut) to 5.93 (Puerto Rico). Females as compared to males had only marginally higher rates of suicidal ideation in most countries, reaching a two-fold increase in Taiwan. Females as compared to males had more consistently higher rates for suicide attempts, reaching a two- to three-fold increase in most countries. Suicide ideation and attempts in most countries were associated with being currently divorced/separated as compared to currently married. CONCLUSIONS: While the rates of suicide ideation varied widely by country, the rates of suicide attempts were more consistent across most countries. The variations were only partly explained by variation in rates of psychiatric disorders, divorce or separation among countries and are probably due to cultural features that we do not, as yet, understand.

Adolescent↗
PubMed1999

Donor lymphocyte infusion induced molecular remission in relapse of acute myeloid leukaemia after allogeneic bone marrow transplantation.

Donor lymphocyte infusion (DLI) has been used successfully to induce remissions in relapse of acute myeloid leukaemia (AML) after bone marrow transplantation (BMT), but molecular eradication of leukaemia has rarely been documented. A patient with AML-M4Eo relapsed after HLA-identical sibling BMT in first complete remission (CR). Cytogenetic and molecular genetic investigations confirmed inv(16) and CBFbeta/MYH11 fusion characteristic of M4Eo. A second remission was obtained with chemotherapy. Full donor chimerism was demonstrated by fluorescence in situ hybridisation. However, molecular evidence of minimal residual disease still persisted, and donor lymphocyte infusion (DLI) was administered. This resulted in molecular eradication, and the patient remained in clinical and molecular remission 16 months from DLI. Our observations showed that, for AML relapse after BMT, molecular leukaemia eradication could be achieved by DLI so that, in cases where genetic markers are available, molecular monitoring should be performed to assess the efficacy of treatment.

Adult↗
PubMed1999

Prophylactic reinfusion of T cells for T cell-depleted allogeneic bone marrow transplantation.

To increase the graft-vs.-leukemia (GVL) effect while maintaining a low mortality from graft-vs.-host disease (GVHD), we conducted a prospective study of T cell titration for 144 patients (90 related, 54 unrelated) between June 1994 and June 1997. Following infusion of a T cell-depleted marrow graft, predetermined doses of T cells, based on the risk factors for GVHD, were administered up to 3 times if greater than a grade II acute GVHD was not seen. Graft failure occurred in three unrelated recipients (2%). Cumulative grades II-IV acute GVHD were seen in 58 +/- 9% of all recipients; 52 +/- 11% related and 75 +/- 13% unrelated. The incidence of grades II-IV acute GVHD following the third add-back (AB) of T cells 78 median days after marrow infusion was lower than that of the earlier ABs: first AB, 36 +/- 8%; second AB, 32 +/- 11%; third AB, 15 +/- 12% (p < 0.05). Chronic GVHD occurred in 56 +/- 12% of related and 79 +/- 16% of unrelated patients. Six died of acute GVHD and two died of chronic GVHD, with an overall GVHD mortality of 6 +/- 4%. In multivariate analyses, unrelated recipients and patients at low risk for GVHD who received a larger number of T cells were identified as patient groups with significant risk for acute and chronic GVHD (both p < 0.05). Unrelated transplant is also shown to be significant for GVHD-related death (p < 0.01). Relapse-free survival of patients with leukemia was shown to be most dependent on chronic GVHD and grades II-IV acute GVHD (both p < 0.01). Anti-leukemic activity independent of GVHD was not observed.

Acute Disease↗