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Biomedical subjects

C Wong

Publications and source records attributed to C Wong.

At least 127 records · Page 7Linked to original sources
PubMed1998

Induction of primary, human antigen-specific cytotoxic T lymphocytes in vitro using dendritic cells pulsed with peptides.

Using a murine metastasis model, we have previously shown that antigen-presenting cells (APC) loaded with unfractionated peptides derived from poorly immunogenic, highly metastatic tumor cells represent a potent form of tumor vaccine. The antimetastatic effect of peptide pulsed APC could be further enhanced by pretreating the cells with antisense oligonucleotides directed against the TAP-2 gene to increase the density of specific peptide-major histocompatibility complex (MHC) class I complexes and thereby improve the APC function of the treated cells (Nair SK et al., J Immunol 1996;156:1772). In this study, we investigated whether similar strategies can be used to enhance the potency of human dendritic cells (DC) to present antigen. We show that human DC pulsed with peptides encoding known cytotoxic T-lymphocyte (CTL) epitopes stimulate both memory and primary CTL responses in vitro after two cycles of stimulation with the peptide-pulsed DC. Two approaches were used to increase the density of specific peptide-MHC complexes on the surface of DC. One approach was to inhibit transporter associated with antigen presentation (TAP) function using TAP antisense oligonucleotides. The second approach was to inhibit the endogenous generation of the peptide epitopes by pretreating the DC with a proteasome inhibitor. Treatment of DC with either TAP antisense oligonucleotides or with a proteasome inhibitor resulted in a dramatic enhancement of primary CTL induction.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

A survey of depressive symptoms among Vietnamese-American men in three locales: prevalence and correlates.

Vietnamese are one of the fastest growing ethnic minority groups in the United States. The purpose of this study was to determine the prevalence and correlates of high depression scores among Vietnamese men in three locales. Computer assisted telephone interviews were conducted with adult Vietnamese men in San Francisco/Alameda Counties, Santa Clara County, and the city of Houston. Telephone numbers of households with Vietnamese surnames were chosen randomly from area telephone books. Depression was assessed using a previously validated Vietnamese language depression screening instrument with 86% sensitivity and 96% specificity for major depression. Between 8.2% and 9.8% of the men scored above the cut-off. Logistic regression analysis revealed that men who were the least proficient in English, poorer, unemployed or disabled, veterans, and those living in Houston were more likely to have a high depression score. Based on the characteristics of the screening instrument, rates of clinical depression among Vietnamese men may be modestly higher than rates for men in the general population. However, high-risk subgroups identified by our analyses may suffer from substantially higher rates of clinical depression. To our knowledge, ours is the first study to show that community context or locale is an independent predictor of high depressive symptoms in this population. These findings have important implications for prevention and intervention approaches to depression among Vietnamese men.

Adult↗
PubMed1998

Genetically modified ruminal bacteria protect sheep from fluoroacetate poisoning.

Four strains of Butyrivibrio fibrisolvens, transformed with a gene encoding fluoroacetate dehalogenase, maintained a combined population of 10(6) to 10(7) cells ml-1 in the rumens of test sheep. Five inoculated sheep showed markedly reduced toxicological symptoms after fluoroacetate poisoning when behavioral, physiological, and histological effects were compared with those of five uninoculated control sheep.

Animals↗
PubMed1998

Natural isolates of simian virus 40 from immunocompromised monkeys display extensive genetic heterogeneity: new implications for polyomavirus disease.

Simian virus 40 (SV40) DNAs in brain tissue and peripheral blood mononuclear cells (PBMCs) of eight simian immunodeficiency virus-infected rhesus monkeys with SV40 brain disease were analyzed. We report the detection, cloning, and identification of five new SV40 strains following a quadruple testing-verification strategy. SV40 genomes with archetypal regulatory regions (containing a duplication within the G/C-rich regulatory region segment and a single 72-bp enhancer element) were recovered from seven animal brains, two tissues of which also contained viral genomes with nonarchetypal regulatory regions (containing a duplication within the G/C-rich regulatory region segment as well as a variable duplication within the enhancer region). In contrast, PBMC DNAs from five of six animals had viral genomes with both regulatory region types. It appeared, based on T-antigen variable-region sequences, that nonarchetypal virus variants arose de novo within each animal. The eighth animal exclusively yielded a new type of SV40 strain (SV40-K661), containing a protoarchetypal regulatory region (lacking a duplication within the G/C-rich segment of the regulatory region and containing one 72-bp element in the enhancer region), from both brain tissue and PBMCs. The presence of SV40 in PBMCs suggests that hematogenous spread of viral infection may occur. An archetypal version of a virus similar to SV40 reference strain 776 (a kidney isolate) was recovered from one brain, substantiating the idea that SV40 is neurotropic as well as kidney-tropic. Indirect evidence suggests that maternal-infant transmission of SV40 may have occurred in one animal. These findings provide new insights for human polyomavirus disease.

Amino Acid Sequence↗
PubMed1998

Human cyclin K, a novel RNA polymerase II-associated cyclin possessing both carboxy-terminal domain kinase and Cdk-activating kinase activity.

The gene coding for human cyclin K was isolated as a CPR (cell-cycle progression restoration) gene by virtue of its ability to impart a Far- phenotype to the budding yeast Saccharomyces cerevisiae and to rescue the lethality of a deletion of the G1 cyclin genes CLN1, CLN2, and CLN3. The cyclin K gene encodes a 357-amino-acid protein most closely related to human cyclins C and H, which have been proposed to play a role in regulating basal transcription through their association with and activation of cyclin-dependent kinases (Cdks) that phosphorylate the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase II (RNAP II). Murine and Drosophila melanogaster homologs of cyclin K have also been identified. Cyclin K mRNA is ubiquitously expressed in adult mouse and human tissues, but is most abundant in the developing germ cells of the adult testis and ovaries. Cyclin K is associated with potent CTD kinase and Cdk kinase (CAK) activity in vitro and coimmunoprecipitates with the large subunit of RNAP II. Thus, cyclin K represents a new member of the "transcription" cyclin family which may play a dual role in regulating Cdk and RNAP II activity.

Amino Acid Sequence↗
PubMed1998

Treatment of acute asthmatic exacerbations with an increased dose of inhaled steroid.

OBJECTIVE: To investigate the efficacy of an increased dose of inhaled steroid used within the context of an asthma self management plan for treating exacerbations of asthma. DESIGN: Randomised, double blind, placebo controlled, crossover trial. METHODS: Twenty eight children aged 6-14 years with asthma of mild to moderate severity were studied for six months. Eighteen pairs of exacerbations were available for analysis, during which subjects took an increased dose of inhaled steroids or continued on the same dose. RESULTS: There was no significant difference between increasing inhaled steroids or placebo on morning or evening peak expiratory flow rates (PEFRs), diurnal peak flow variability, or symptom scores in the two weeks following an asthma exacerbation. Difference (95% confidence intervals) in baseline PEFR on days 1-3 were 3.4% (-3.5% to 10.4%) and -0.9% (-4.7% to 2.9%) for inhaled steroid and placebo, respectively. Spirometric function and the parents' opinion of the effectiveness of asthma medications at each exacerbation were also not significantly different between inhaled steroid or placebo. CONCLUSION: This study suggests that increasing the dose of inhaled steroids at the onset of an exacerbation of asthma is ineffective and should not be included in asthma self management plans.

Acute Disease↗
PubMed1998

The clinical value of digene hybrid capture HPV DNA testing in a referral-based population with abnormal pap smears.

PURPOSE OF INVESTIGATION: The hybrid capture human papillomavirus (HPV) DNA assay is offered by the manufacturer to assist clinicians with patients with ASCUS pap smear results to assess the risk factor and to potentially direct follow-up of these patients. In our practice, a gynecologic oncology practice that has a referral based population with abnormal pap smears, our purpose was to evaluate the patients referred with all grades of abnormal cervical cytology. METHODS: One hundred consecutive patients who were referred for evaluation of abnormal cervical cytology: atypical squamous cells of undetermined significance (ASCUS); low-grade squamous intraepithelial lesion (LGSIL); high-grade squamous intraepithelial lesion (HGSIL); or squamous cell carcinoma (SCC) were evaluated by repeat pap smear, hybrid capture HPV DNA analysis and colposcopy. Colposcopic findings were recorded, and if appropriate, cervical biopsies were performed. Hybrid capture results were correlated with histologic and cytologic findings. Using histopathologic diagnosis as the reference standard, the sensitivity and positive predictive value of pap smear and high risk HPV were calculated. The Kappa test was used to correlate colposcopic and histopathologic findings. RESULTS: Repeat pap smears at the time of initial consultation demonstrated 25 patients with normal results, 39 with LGSIL, 30 with HGSIL, 1 SCC and 5 ASCUS. Seventy-eight patients underwent cervical biopsy. Colposcopic findings correlated significantly with histopathologic findings (p<0.0001). Forty-four percent of patients tested positive for HPV DNA: 40 patients with high risk HPV, three patients with low risk HPV, and one patient with both high risk and low risk HPV. Sixteen of 39 patients (41%) with LGSIL on pap smear tested positive for high risk HPV; 37% of patients in this group required cervical conization because cervical biopsies demonstrated moderate/severe dysplasia. The diagnosis of moderate/severe dysplasia significantly correlated with the presence of high risk HPV [OR 78.9 (8.31-389.30)]. There was no significant correlation between the HPV DNA signal strengths and the histologic grade of dysplasia. The sensitivity and the positive predictive value of pap smear alone in identifying moderate/severe dysplasia was 62% and 96%, respectively. The combination of HGSIL pap smears and high risk HPV increased the sensitivity but not the positive predictive value for the detection of moderate/severe dysplasia to 77.7% and 95%, respectively (P=NS). CONCLUSIONS: Although in this setting, the use of hybrid capture DNA testing did not significantly improve the sensitivity or positive predictive value of the diagnosis of HGSIL cytology when compared to cytologically indicated plus colposcopically directed cervical biopsies in this population of women at high risk for the presence of disease, the combination of HGSIL pap smears and high-risk HPV did result in a clinically important increase in the diagnosis of moderate/severe dysplasia.

Adult↗
PubMed1997

Selective inhibition of the sperm-specific lactate dehydrogenase isozyme-C4 by N-isopropyl oxamate.

In the present study, we demonstrated that the attachment of the nonpolar isopropylic carbon chain in the nitrogen of oxamate, converted this competitive inhibitor of LDH isozymes into a powerful selective inhibitor of mouse LDH-C4. The comparative study of the inhibitory effect of oxamate and N-isopropyl oxamate on mouse LDH isozymes pointed out that the isopropylic carbon chain conferred upon N-isopropyl oxamate a high affinity for LDH-C4 and a marked decrease in the affinity for the other isozymes since oxamate showed more inhibitory effect on LDH-1 (Ki = 0.06 mM) and LDH-5 (Ki = 0.08 mM), and less inhibitory effect on LDH-C4 (Ki = 0.25 mM). On the other hand, N-isopropyl oxamate showed the highest inhibitory effect on LDH-C4 (Ki = 0.014 mM) and poor inhibitory effect on LDH-1 (Ki = 0.4 mM) and LDH-5 (Ki = 0.8 mM). Apparently, the enzymatic inactivation proceeded through a reversible binding of N-isopropyl oxamate, facilitated by nonpolar interactions with a hydrophobic region present only in the active site of mouse LDH-C4, resulting in a selective inhibition of this isozyme in comparison with the other LDH isozymes. N-isopropyl oxamate was also a powerful competitive inhibitor of LDH-C4 (Ki = 0.015 mM) compared with oxamate (Ki = 0.35 mM), using alpha-ketoisocaproate as a substrate.

Animals↗
PubMed1997

Method to screen for relevant yeast two-hybrid-derived clones by coimmunoprecipitation and colocalization of epitope-tagged fragments--application to Bcl-xL.

The yeast two-hybrid system is a powerful genetic method to screen cDNA libraries to identify protein-protein interactions. A screen with a typical bait may yield many clones, including ones that are not biologically relevant which need to be eliminated by evaluating each clone in an alternative assay to confirm the interaction with the bait protein. We have developed an efficient assay to quickly screen two-hybrid-derived clones for coimmunoprecipitation and colocalization with the bait protein in mammalian cells. Gene fragments derived from a two-hybrid screen are cloned into an epitope tagging vector that can generate high levels of epitope-tagged protein in mammalian cells. The vector expressing an epitope-tagged protein is then cotransfected into mammalian cells with an expression vector for the bait protein. Interaction between the bait protein and epitope-tagged protein is evaluated by coimmunoprecipitation and colocalization. We demonstrate the utility of this approach by applying it to clones isolated in a two-hybrid screen using Bcl-xL as bait, showing that two-hybrid-derived fragments of Bad and Bax, previously known to interact with Bcl-xL, both colocalize and coimmunoprecipitate with Bcl-xL.

Animals↗
PubMed1997

ICAP-1, a novel beta1 integrin cytoplasmic domain-associated protein, binds to a conserved and functionally important NPXY sequence motif of beta1 integrin.

The cytoplasmic domains of integrins are essential for cell adhesion. We report identification of a novel protein, ICAP-1 (integrin cytoplasmic domain- associated protein-1), which binds to the 1 integrin cytoplasmic domain. The interaction between ICAP-1 and beta1 integrins is highly specific, as demonstrated by the lack of interaction between ICAP-1 and the cytoplasmic domains of other beta integrins, and requires a conserved and functionally important NPXY sequence motif found in the COOH-terminal region of the beta1 integrin cytoplasmic domain. Mutational studies reveal that Asn and Tyr of the NPXY motif and a Val residue located NH2-terminal to this motif are critical for the ICAP-1 binding. Two isoforms of ICAP-1, a 200-amino acid protein (ICAP-1alpha) and a shorter 150-amino acid protein (ICAP-1beta), derived from alternatively spliced mRNA, are expressed in most cells. ICAP-1alpha is a phosphoprotein and the extent of its phosphorylation is regulated by the cell-matrix interaction. First, an enhancement of ICAP-1alpha phosphorylation is observed when cells were plated on fibronectin-coated but not on nonspecific poly-L-lysine-coated surface. Second, the expression of a constitutively activated RhoA protein that disrupts the cell-matrix interaction results in dephosphorylation of ICAP-1alpha. The regulation of ICAP-1alpha phosphorylation by the cell-matrix interaction suggests an important role of ICAP-1 during integrin-dependent cell adhesion.

3T3 Cells↗
PubMed1997

Conservation of the Chk1 checkpoint pathway in mammals: linkage of DNA damage to Cdk regulation through Cdc25.

In response to DNA damage, mammalian cells prevent cell cycle progression through the control of critical cell cycle regulators. A human gene was identified that encodes the protein Chk1, a homolog of the Schizosaccharomyces pombe Chk1 protein kinase, which is required for the DNA damage checkpoint. Human Chk1 protein was modified in response to DNA damage. In vitro Chk1 bound to and phosphorylated the dual-specificity protein phosphatases Cdc25A, Cdc25B, and Cdc25C, which control cell cycle transitions by dephosphorylating cyclin-dependent kinases. Chk1 phosphorylates Cdc25C on serine-216. As shown in an accompanying paper by Peng et al. in this issue, serine-216 phosphorylation creates a binding site for 14-3-3 protein and inhibits function of the phosphatase. These results suggest a model whereby in response to DNA damage, Chk1 phosphorylates and inhibits Cdc25C, thus preventing activation of the Cdc2-cyclin B complex and mitotic entry.

14-3-3 Proteins↗
PubMed1997

Application of asthma action plans to childhood asthma: a national survey.

AIM: To determine the frequency of asthma action plan use by doctors in the management of childhood asthma in New Zealand, and their recommendations about the application of an increased dose of inhaled steroids in those plans. METHODS: A postal survey was sent to all 236 paediatricians and paediatric registrars and to a random sample of 500 general practitioners (GPs) in New Zealand. Questions related to asthma action plan use, the inclusion of an increased dose of inhaled steroid in those plans and details of the way the inhaled steroid dose is adjusted. RESULTS: Valid responses were received from 168 (71%) paediatricians and paediatric registrars and 340 (68%) GPs. The majority (92.6%) of GPs and paediatricians and paediatric registrars used action plans and 83.6% included a step involving an increased dose of inhaled steroids. Compared with paediatricians and paediatric registrars, GPs gave action plans to a smaller proportion of asthmatic children in their care and included an increased dose of inhaled steroid more often (GPs = 94.5%, paediatricians and paediatric registrars = 57%). CONCLUSION: In New Zealand the use of asthma action plans is inconsistent with the recommendations contained in published consensus documents in that not all asthmatic children are advised about an action plan. Specific issues relating to this and to the use of an increased dose of inhaled steroids in action plans require clarification and further research.

Administration, Inhalation↗
PubMed1997

Occupational asthma and other nonasbestos occupational respiratory diseases notified between 1993 and 1996.

AIM: To review notifications to the Occupational Safety and Health Service of the Department of Labour Notifiable Occupational Disease System since its inception until June 1996. METHODS: All notifications received for non asbestos related occupational respiratory disease were reviewed to evaluate the outcome of the notification and to identify the causative agent where possible. RESULTS: There were 277 cases notified and investigated including worksite investigations. Of these 73 cases were confirmed as having occupational asthma, 35 by the asthma validation panel. Nineteen cases of other occupational respiratory disease were notified of which 11 were reviewed by the panel. Extrinsic allergic alveolitis secondary to organic dusts was the most common such notification. CONCLUSIONS: Isocyanates are well recognised as a cause of occupational asthma in New Zealand. It is suspected that occupational asthma and other occupational respiratory diseases are poorly notified to this system. Better mechanisms are needed to identify occupational causes of respiratory (and other) disease.

Asthma↗
PubMed1997

Neuronal localization of presenilin-1 and association with amyloid plaques and neurofibrillary tangles in Alzheimer's disease.

Mutations in the presenilin-1 (PS1) gene is a cause of early- onset familial Alzheimer's disease (AD). Endogenous PS1 is associated with the endoplasmic reticulum in the cell body of undifferentiated SH-SY5Y neuroblastoma cells. At early stages of neuronal differentiation in rat hippocampal culture, PS1 appears in all neuritic processes and in growth cones. In mature differentiated neurons, PS1 is concentrated in the somatodendritic compartment but is also present at lower levels in axons. A similar localization of PS1 is observed in vivo in neurons of the adult human cerebral cortex. In sporadic AD, PS1 appears in the dystrophic neurites of mature amyloid plaques and co-localizes with a subset of intraneuronal neurofibrillary tangles (NFTs). About 30% of hippocampal NFTs are labeled with a highly specific antibody to the PS1 C-terminal loop domain but not with an antibody to the PS1 N terminus. This observation is consistent with a potential association of the PS1 C-terminal fragment with NFTs, because PS1 is constitutively cleaved to N- and C-terminal fragments in neurons. These results suggest that PS1 is highly expressed and broadly distributed during early stages of neuronal differentiation, consistent with a role for PS1 in neuronal differentiation. Furthermore, the co-localization of PS1 with NFTs and plaque dystrophic neurites implicates a role for PS1 in the diverse pathological manifestations of AD.

Alzheimer Disease↗