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Biomedical subjects

W Lam

Publications and source records attributed to W Lam.

At least 19 recordsLinked to original sources
PubMed2005

Concurrent translocation of BCL2 and MYC with a single immunoglobulin locus in high-grade B-cell lymphomas.

B-cell leukaemia or lymphoma with a combination of t(8;14)(q24;q32) of Burkitt leukaemia/lymphoma and t(14;18)(q32;q21) of follicular lymphoma may present clinically as de novo acute lymphoblastic leukaemia or transformation of follicular lymphoma to aggressive histology diffuse lymphoma. A number of cell lines have been reported with a complex t(8;14;18) with fusion of MYC, IGH and BCL2 on the same derivative 8 chromosome. The objective of this study was to determine the frequency and chromosomal features of this der(8)t(8;14;18) in a series of acute leukaemias and malignant lymphomas. A database of 1350 leukaemia and lymphoma karyotypes was searched for cases with structural alterations affecting both 8q24 and 18q21. A total of 55 cases were identified, of which eight revealed a complex der(8)t(8;14;18) with an MYC-IGH-BCL2 rearrangement resulting from translocation of BCL2 and MYC with a single disrupted IGH allele. Molecular cytogenetic investigation is essential to identify cases of high-grade leukaemia/lymphoma with concurrent translocations affecting the BCL2 and MYC loci.

Adult↗
PubMed2004

Magnetic resonance screening of iron status in transfusion-dependent beta-thalassaemia patients.

The clinical utility of dual sequence (T1- and T2-weighted) magnetic resonance (MR) imaging in estimating liver iron concentration (LIC) in 32 transfusion-dependent beta-thalassaemia major (24 females; age 18.5+/-5.9 years) patients on desferrioxamine was evaluated. Signal intensity ratios (SIR) between liver, spleen and pancreas to psoas muscle were determined on both sequences. Relationships between clinical and MR parameters, and accuracy of SIR thresholds in determining adequacy of chelation from LIC were analysed. Liver T1- and T2-SIR were related to LIC (P < 0.001). T1-SIR < 0.60 predicted severe iron overload (LIC > 15 mg/g) with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%, 87%, 33% and 100% respectively. T2-SIR < 0.1 yielded 100% sensitivity, 93% specificity, 50% PPV and 100% NPV. T1-SIR > or = 1.1 predicted LIC < 7 mg/g with 69% sensitivity, 88% specificity, 85% PPV and 74% NPV. T2-SIR > or = 0.20 yielded 56.5% sensitivity, 94% specificity, 90% PPV and 71% NPV. LIC correlated with liver T1-SIR, liver T2-SIR and serum ferritin (r = -0.76, -0.65, 0.47, respectively; P < 0.01). Serum ferritin was inversely related to liver T1-SIR, liver T2-SIR and spleen T2-SIR (r = -0.35, -0.43, -0.40, respectively; P < 0.05). Mean total transfusion burden was not related to any MR parameter. Although neither MR sequence was a highly accurate predictor of LIC, SIR thresholds are useful to determine presence of iron overload and adequacy of chelation treatment.

Adolescent↗
PubMed2004

Benefits of oral supplementation with and without synbiotics in young children with acute bacterial infections.

Acutely ill children (n = 129) aged 1-6 years receiving antibiotic therapy were randomized to receive a nutritional supplement with (PS) or without (P) synbiotics or a fruit-flavored drink (D) with their medications. Group PS had significantly greater weight gains (versus D) following antibiotic therapy. The percentages of subjects without bacterial illnesses 14 days following antibiotic therapy were as follows: 94.3% (PS), 87.8% (D), and 80.6% (P). PS (vs D) significantly increased fecal Lactobacillus in a subset of subjects. Oral supplements increase energy intake and promote weight gain in acutely ill children receiving antibiotics; synbiotics may confer additional benefits by increasing bifidobacteria levels.

Acute Disease↗
PubMed2003

Optical systems for in vivo molecular imaging of cancer.

Progress toward a molecular characterization of cancer would have important clinical benefits; thus, there is an important need to image the molecular features of cancer in vivo. In this paper, we describe a comprehensive strategy to develop inexpensive, rugged and portable optical imaging systems for molecular imaging of cancer, which couples the development of optically active contrast agents with advances in functional genomics of cancer. We describe initial results obtained using optically active contrast agents to image the expression of three well known molecular signatures of neoplasia: including over expression of the epidermal growth factor receptor (EGFR), matrix metallo-proteases (MMPs), and oncoproteins associated with human papillomavirus (HPV) infection. At the same time, we are developing inexpensive, portable optical systems to image the morphologic and molecular signatures of neoplasia noninvasively in real time. These real-time, portable, inexpensive systems can provide tools to characterize the molecular features of cancer in vivo.

Biomarkers, Tumor↗
PubMed2002

Identification of genes differentially expressed in V79 cells grown as multicell spheroids.

PURPOSE: Growth of Chinese hamster V79 cells as multicell spheroids leads to an increase in resistance to killing by ionizing radiation and etoposide. Differential display was used to identify changes in gene expression that occur when cells are grown as spheroids. MATERIALS AND METHODS: Differential display was performed using exponentially growing Chinese hamster V79 cells and the outer cell layer of V79 spheroids. Using six different pairs of primers, 20 altered bands were selected. Eight genes, confirmed using reverse Northerns, showed a match in a GenBank search. Antibodies against a calcium-binding protein, mts1, confirmed differential expression of this protein. Intracellular free calcium levels were measured using fluo-3 fluorescence, and the effect of a calcium-binding agent on etoposide resistance was examined using the comet assay. RESULTS: Genes upregulated in the outer cell layer of spheroids relative to monolayers included: (1) mts1 (S100A4), a calcium binding protein implicated in proliferation, metastasis, cell adhesion, and angiogenesis; (2) cytochrome c oxidase II; (3) B-ind1, a mediator of Rac-1 signaling; (4) TRAM, an endoplasmic reticulum protein. Genes downregulated in spheroids were: (5) phosphoglycerate kinase; (6) ARL-3, a ras-related GTP binding protein; (7) MHC class III complement 4A; and (8) 2,4-dienoyl-CoA. Immunohistochemistry confirmed overexpression of mts1 and another calcium-binding protein, calreticulin, in V79 outer spheroid cells relative to monolayers. C6 rat glioma and SiHa human cervical carcinoma cells that demonstrate a contact effect also showed upregulation of mts1 or calreticulin, while WiDr colon carcinoma cells that lack contact resistance showed no change in expression of either calcium binding protein. Intracellular free calcium levels were found to be almost two times lower in the outer cells of V79 spheroids compared to monolayers. V79 monolayer and outer spheroid cells treated with the calcium chelating agent BAPTA-AM showed a similar level of DNA damage by etoposide. CONCLUSIONS: Expression of genes involved in calcium binding, signaling and metabolism are differentially expressed when V79 cells are grown as spheroids. Differences in the levels of intracellular calcium may underlie the contact effect.

Animals↗
PubMed2001

PKCdelta-dependent deubiquitination and stabilization of Gadd45 in A431 cells overexposed to EGF.

Epidermal growth factor (EGF) receptor-overexpressing p53-deficient A431 cells response to toxic dose of EGF by G1 arrest and apoptosis was studied. We previously reported an increased expression of growth arrest and DNA-damage-inducible gene, Gadd45, in EGF-overexposed A431 cells. The mechanism for this induction was increased half-lives of mRNA and protein. In this study, using phorbol ester (a PKC activator) and specific inhibitors of PKC isoforms, we showed that protein kinase C-delta (PKCdelta) was involved in the increase of Gadd45 protein stability. We further demonstrated that Gadd45 is ubiquitinated and is regulated by proteolysis. While EGF induced ubiquitination of total cellular proteins, there was a decrease in Gadd45 ubiquitination, which could be inhibited by Rottlerin, a PKCdelta-specific inhibitor. These results suggest that an increase in Gadd45 stability may involve PKCdelta-dependent ubiquitin-proteasome pathway.

Acetophenones↗
PubMed2001

Epidermal growth factor induces Gadd45 (growth arrest and DNA damage inducible protein) expression in A431 cells.

Epidermal growth factor (EGF) receptor over-expressing, p53-deficient A431 cells response to toxic dose of EGF by G1 arrest and apoptosis. Applying cDNA expression array technology we demonstrated that EGF increased the levels of Gadd45 mRNA. Northern blot and Western blot analyses confirmed that both Gadd45 mRNA and protein were increased. Concurrently half-lives of Gadd45 mRNA and protein also increased. Nuclear run-on experiments did not show a large increase of Gadd45 mRNA transcription rate. Gadd45 mRNA and protein started to increase after 1 h of EGF treatment and remained high for up to 10 h. We have also confirmed previous studies which showed that in EGF-stimulated A431 cells p21(Cip1/Waf1) (cyclin-dependent kinase interacting protein 1) was up-regulated within the same time frame. Thus it appears that in addition to inducing G2 arrest by directly disrupting Cdc2/Cyclin B1 complex in genotoxic-stressed cells, Gadd45 may also participate in G1 arrest in growth factor overexposed cells.

Blotting, Western↗
PubMed2001

Exhaled nitric oxide: the effects of age, gender and body size.

Since little is known of the effects of age, gender, and body size on exhaled nitric oxide (NO) production, we have conducted a prospective study to examine these factors in a healthy nonsmoking women (mean age +/- SD 47.7 +/- 15.8, range 20-79 years). Exhaled NO was measured by an automatic chemiluminescence analyzer (Sievers NO Analyser 280) at steady expiration. Men had significantly higher exhaled NO levels than women (p = 0.001). Although exhaled NO levels did not correlate with age (r = 0.12, p = 0.17), it correlated significantly with height (r = 0.23, p = 0.02), weight (r = 0.34, p

Adult↗
PubMed2000

Low-level doxorubicin resistance in benzo[a]pyrene-treated KB-3-1 cells is associated with increased LRP expression and altered subcellular drug distribution.

The P-glycoprotein (P-gp)-negative epidermoid pharyngeal carcinoma cells KB-3-1 were grown in 0.25 mM benzo[a]pyrene (BaP) for 3 months and increased resistance to doxorubicin, but not to vinblastine, colchicine, or cisplatin, was found. Doxorubicin resistance was not altered by cyclosporin, the P-gp inhibitor. Intracellular accumulation of BaP or calcein, a substrate for P-gp and multidrug resistance protein (MRP), was not altered by inhibitors of the P-gp and MRP. The expression of cytochrome P450 (CYP) 1A1, lung-resistance-related protein (LRP), P-gp, and MRP was investigated. Overexpression of CYP1A and LRP, on the mRNA and protein levels, was found. BaP-treated KB-3-1 cells remained P-gp negative while the level of MRP was not altered. Subcellular accumulation of BaP was found to be localized in the cytoplasm and minimal in the nuclei in BaP treated cells. In contrast, even penetration of BaP to the nuclei and cytoplasm was found in untreated cells. Subcellular distribution of doxorubicin was altered following BaP treatment with localized accumulation of the cancer drug in cytoplasmic organelles but not in the nuclei. Our data suggested that LRP might play a protective role against toxic compounds. The correlation of increased expression of LRP, but not P-gp nor MRP, with decreased doxorubicin accumulation in the nuclear target suggests a pivotal role of this perinuclear transporter in the MDR phenotype of P-gp-negative cancer cells. These results also propose an alternative mechanism of cancer drug resistance emergence, namely, induction of LRP activity following treatment with BaP, an environmental toxicant and a carcinogen.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Transcranial Doppler ultrasonography (TCD) in ventilated head injured patients: correlation with stable xenon-enhanced CT.

Disturbance of cerebral vasomotor regulation has been shown to be associated with the severity of traumatic brain injury (TBI). The transient hyperaemic response (THR) test is a test of the pressure autoregulatory response in terms of cerebral blood flow velocity after a brief carotid artery compression. Correlating with the test of cerebral vascular reactivity (CVR) to carbon dioxide by means of passive hyperventilation suggested that the THR test is a simple clinical test for the assessment of cerebral haemodynamic status in head-injured patients.

Adolescent↗
PubMed2000

Characterisation of multiple trypsins from the midgut of Locusta migratoria.

Three isoforms of trypsin were identified in midgut preparations from Locusta migratoria. Ammonium-sulphate-fractionated luminal contents of midguts were subjected to benzamidine affinity chromatography; proteins eluted by benzamidine were then separated by anion-exchange chromatography. Cationic (TRY 1) and anionic (TRY 2) trypsin activities were eluted from the DEAE column. TRY 1 was homogeneous, producing a single band of Mr 23,000 on SDS-PAGE. TRY 2 comprised two trypsins, TRY 2A (Mr 27,000) and TRY 2B (Mr 29,000). Following a subsequent chromatography step using a Bio-Rad UNO Q column, TRY 2A and TRY 2B were resolved to homogeneity. When homogenates of midgut caecae were the starting material for chromatography, SDS-PAGE of benzamidine-eluted proteins revealed an additional putative trypsin of Mr 17,000 (termed SERP 17) which had been absent from luminal enzyme preparations. Determination of the N-terminal 11 amino acid residues of each protein revealed unique, but similar sequences. The four sequences all began with IVGG, a motif which signifies all four proteins are serine proteases. TRY 1, TRY 2A and TRY 2B were shown to contain only trypsin activity and the preparations were sensitive to inhibition by AEBSF, PMSF, TLCK, benzamidine, leupeptin, SBTI, BPTI and E64.

Amino Acid Sequence↗
PubMed2000

Toxicity and DNA binding of dextran-doxorubicin conjugates in multidrug-resistant KB-V1 cells: optimization of dextran size.

We previously showed that conjugating doxorubicin to very large 70-500 kDa dextran decreased its removal rate from P-glycoprotein (P-gp) over-expressing, multidrug-resistant KB-V1 cells. Furthermore these conjugates could act synergistically with other cancer drugs. In the drug-sensitive 3-1 clone, but not in the V1 subclone which was 300-fold more resistant to free doxorubicin, conjugation led to a size-related decrease in toxicity. Here we identified the optimal size of dextran for avoiding P-gp-mediated efflux and yet preserving as much as possible doxorubicin toxicity. Chemically reduced, intracellularly stable 3.4-10 kDa conjugates were prepared. Confocal microscopy and fluorescence quenching experiments showed that these conjugates entered nuclei and interacted with DNA. In 3-1 cells, but not in V1 cells, cytotoxicity of conjugates decreased 14- to 45-fold linearly related to log size of the carrier (r=0.95). In V1 cells toxicity of the 10 kDa conjugate exceeded that of free doxorubicin. After conjugation the equilibrium binding constant of the DNA-drug complex (KA) decreased only by up to 3-fold. In 3-1 cells, but not in VI cells, DNA binding kinetics was an important factor and toxicity could be linearly correlated to 1/KA of conjugate (r=0.94). Drug accumulation decreased with an increase in dextran size but drug removal was decreased only in V1 cells. It appeared that drug uptake was also sensitive to dextran conjugation. In Vl cells drug removal was sensitive to the P-gp inhibitor verapamil or energy starvation. Ratios of V1/3-1 toxicity, drug accumulation and drug removal correlated linearly with log dextran size. When these ratios equaled 1, dextran sizes were estimated to be 32, 103 and 21 kDa, respectively.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Sputum elastase in steady-state bronchiectasis.

STUDY OBJECTIVES: To study the correlations between sputum elastase output with clinical and sputum inflammatory and microbial factors in steady-state bronchiectasis. DESIGN: Prospective recruitment of patients with bronchiectasis (17 women; 48.5 +/- 16.5 years old; FEV(1)/FVC, 1.3 +/- 0.6/2.1 +/- 0.9) for assessment of 24-h sputum output of elastase, bacteria, leukocytes, interleukin (IL)-1beta, IL-8, tumor necrosis factor-alpha, and leukotriene B(4). Clinical variables assessed concomitantly included 24-h sputum volume, lung spirometry, number of lung lobes affected by bronchiectasis, and exacerbation frequency. SETTING: Consecutive recruitment of outpatients (n = 30) in steady-state bronchiectasis. MEASUREMENTS AND RESULTS: Twenty-four-hour sputum elastase output correlated with 24-h sputum volume (r = 0.79, p = 0.0001); number of bronchiectatic lung lobes (r = 0.54, p = 0.0026); percent predicted FEV(1) (r = -0. 48, p = 0.0068); percent predicted FVC (r = -0.49, p = 0.001); and leukocyte output (r = 0.75, p = 0.0001). There was no correlation between the sputum output of bacteria with either inflammatory or enzymatic factors (p > 0.05). CONCLUSION: Our data highlight the importance of elastase and the possibility of independent roles for enzymatic, inflammatory, and microbial components in the pathogenesis of bronchiectasis. Further research on novel therapy targeting each of these components should be pursued.

Adult↗
PubMed2000

Serum leptin and vascular risk factors in obstructive sleep apnea.

STUDY OBJECTIVES: To define the metabolic profile relevant to vascular risks in obstructive sleep apnea (OSA) and the role of leptin resistance in this risk profile. DESIGN: Case control study. SETTING: Sleep Laboratory, Queen Mary Hospital, University of Hong Kong, China. METHODS: Thirty OSA subjects were matched with 30 non-OSA subjects for body mass index (BMI), age, sex, and menopausal status. Neck, waist, and hip girth, skinfold thickness, and fasting serum levels of lipids, glucose, insulin, and leptin were compared between these two groups. RESULTS: Compared with control subjects with a similar BMI but without OSA, the OSA group had a significantly more adverse vascular risk factor profile, including dyslipidemia, higher diastolic BP, insulin resistance, and greater adiposity reflected by skinfold thickness. OSA subjects also had higher circulating leptin levels (9.18+/-4.24 ng/mL vs 6.54+/-3.81 ng/mL, mean +/- SD, p = 0.001). Serum leptin levels correlated positively with BMI, skinfold thickness, serum cholesterol, low-density lipoprotein cholesterol, insulin, insulin/glucose ratio, apnea-hypopnea index, and oxygen desaturation time; multiple stepwise regression analysis identified skinfold thickness, waist/hip ratio, serum low-density lipoprotein cholesterol, and diastolic BP as independent correlates, while only serum insulin and diastolic BP were independent correlates in OSA subjects. After treatment with nasal continuous positive airway pressure for 6 months, there was a significant decrease in circulating leptin (p = 0.01) and triglyceride levels (p = 0.02) without change in other parameters. CONCLUSION: Despite controlling for BMI, OSA subjects showed distinct profiles with clustering of vascular risk factors. Hyperleptinemia was present in the OSA subjects, but it can be normalized by treatment with nasal continuous positive airway pressure, suggesting that increased leptin resistance was not the cause of OSA or its associated vascular risks.

Adult↗
PubMed1999

Medical data mining using evolutionary computation.

In this paper, we introduce a system for discovering medical knowledge by learning Bayesian networks and rules. Evolutionary computation is used as the search algorithm. The Bayesian networks can provide an overall structure of the relationships among the attributes. The rules can capture detailed and interesting patterns in the database. The system is applied to real-life medical databases for limb fracture and scoliosis. The knowledge discovered provides insights to and allows better understanding of these two medical domains.

Algorithms↗
PubMed1999

Synergism of energy starvation and dextran-conjugated doxorubicin in the killing of multidrug-resistant KB carcinoma cells.

Here we report that 2-deoxyglucose/Na azide treatment and free/conjugated doxorubicin are synergistic in cell killing. As demonstrated by fluorescence confocal microscopy, KB-V1 cells retained more conjugated doxorubicin than free doxorubicin. Verapamil or 2-deoxyglucose/Na azide enhanced only the retention of the free drug and the small (<70 kDa) conjugates, indicating that P-glycoprotein (P-gp) is not effective against large conjugates. Conjugated doxorubicin was excluded from nuclei. Initially both free and conjugated doxorubicin accumulated in cytoplasmic organelles. Upon 2-deoxyglucose/Na azide treatment, fluorescence labeling of organelles dissipated. Prolonged (24 h) incubation of conjugate-preloaded cells resulted in redistribution of some of the organelle-associated fluorescence to nuclei, suggesting decoupling. The appearance of free doxorubicin was confirmed by capillary electrophoresis. 2-Deoxyglucose/Na azide treatment also retarded decoupling. Our results suggest that energy starvation, in addition to increasing cellular retention of P-gp substrates, may affect cellular fate of conjugated drugs with a possible enhancing effect in cancer cell killing.

Antineoplastic Agents↗
PubMed1998

Cytotoxicity and DNA binding characteristics of dextran-conjugated doxorubicins.

The antitumor antibiotic doxorubicin was conjugated with polymeric dextrans of various molecular weights and the cytotoxicity of the conjugates against human carcinoma KB-3-1 cells and its multidrug-resistant subclone KB-V-1 cells was measured by tetrazolium salt MTT assay. The conjugates were much less toxic to the KB-3-1 cells than the free doxorubicin but exhibited similar toxicity to the KB-V-1 cells. The conjugate-DNA interactions were monitored in real-time using an optical biosensor based on evanescent wave detection to obtain the association (ka) and dissociation (kd) rate constants as well as the equilibrium binding constants (KA) of the bindings. Both ka and kd values for the conjugates are more than three magnitudes smaller than those for free doxorubicin, while the KA values of the conjugate-DNA complexes are only about 10 times smaller than that of the free doxorubicin-DNA complex. The results indicate that the cytotoxicity and the DNA-binding kinetics of doxorubicin may be modified with dextran conjugation. The KA values obtained from the biosensor measurements were in close agreement with those determined in solution by fluorescent titration method, verifying the utility of the label-free biosensing measurements as an efficient method for studying ligand-DNA interactions.

Binding Sites↗