PubMed Health⌕ Search

Biomedical subjects

Ka-Fai To

Publications and source records attributed to Ka-Fai To.

At least 37 records · Page 2Linked to original sources
PubMed2005

Coronaviral hypothetical and structural proteins were found in the intestinal surface enterocytes and pneumocytes of severe acute respiratory syndrome (SARS).

Severe acute respiratory syndrome (SARS) is a newly emerging infectious disease that haunted the world from November 2002 to July 2003. Little is known about the biology and pathophysiology of the novel coronavirus that causes SARS. The tissue and cellular distributions of coronaviral hypothetical and structural proteins in SARS were investigated. Antibodies against the hypothetical (SARS 3a, 3b, 6, 7a and 9b) and structural proteins (envelope, membrane, nucleocapsid and spike) of the coronavirus were generated from predicted antigenic epitopes of each protein. The presence of these proteins were first verified in coronavirus-infected Vero E6 tissue culture model. Immunohistochemical studies on different human tissues, including a cohort of nine autopsies, two liver biopsies and intestinal biopsies of SARS patients, further confirmed the existence of coronaviral hypothetical and structural proteins in the cytoplasm of pneumocytes and small intestinal surface enterocytes in SARS patients. With this vast array of antibodies, no signal was observed in other cell types including those organs in which reverse transcriptase-polymerase chain reactions were reported to be positive. Structural proteins and the functionally undefined hypothetical proteins were expressed in coronavirus-infected cells with distinct expression pattern in different organs in SARS patients. These antipeptide antibodies can be useful for the diagnosis of SARS at the tissue level.

Animals↗
PubMed2005

Long-term outcome of Helicobacter pylori-negative idiopathic bleeding ulcers: a prospective cohort study.

BACKGROUND & AIMS: Helicobacter pylori-negative idiopathic ulcers are increasingly recognized. The secular trend and long-term outcome of this condition are unknown. METHODS: We prospectively studied consecutive patients with bleeding gastroduodenal ulcers from January to December 2000. The incidence and etiology of ulcers during this period were compared with that between September 1997 and August 1998. H. pylori-negative idiopathic ulcers were defined as negative tests for H. pylori, no exposure to analgesics within 4 weeks, and absence of other risk factors for ulcers. After the ulcers had healed, patients with H. pylori-negative idiopathic ulcers and patients with H. pylori ulcers who received eradication therapy were followed up for 12 months without anti-ulcer drugs. RESULTS: Six hundred thirty-eight patients had bleeding ulcers: 213 (33.4%) were H. pylori ulcers, and 120 (18.8%) were H. pylori-negative idiopathic ulcers (vs 480 [50.3%] H. pylori ulcers and 40 [4.2%] H. pylori-negative idiopathic ulcers in 1997-1998; P < .001). H. pylori-negative idiopathic ulcers accounted for 16.1% of patients who were admitted for bleeding and 42.4% of patients who bled while in the hospital (P < .0001); 28.3% of patients with H. pylori-negative idiopathic ulcers had histologic evidence of past H. pylori infection. The probability of recurrent ulcer complications in 12 months was 13.4% (95% CI: 7.3%-19.5%) in patients with H. pylori-negative idiopathic ulcers and 2.5% (95% CI: 0.4%-4.6%) in patients with H. pylori ulcers who received eradication therapy (P = .0002). CONCLUSIONS: The incidence of H. pylori-negative idiopathic bleeding ulcers is rising. These ulcers are prone to recurrent complications.

Adult↗
PubMed2005

The 3a protein of severe acute respiratory syndrome-associated coronavirus induces apoptosis in Vero E6 cells.

An outbreak of severe acute respiratory syndrome (SARS) occurred in China and the first case emerged in mid-November 2002. The aetiological agent of this disease was found to be a previously unknown coronavirus, SARS-associated coronavirus (SARS-CoV). The detailed pathology of SARS-CoV infection and the host response to the viral infection are still not known. The 3a gene encodes a non-structural viral protein, which is predicted to be a transmembrane protein. In this study, it was shown that the 3a protein was expressed in the lungs and intestinal tissues of SARS patients and that the protein localized to the endoplasmic reticulum in 3a-transfected monkey kidney Vero E6 cells. In vitro experiments of chromatin condensation and DNA fragmentation suggested that the 3a protein may trigger apoptosis. These data showed that overexpression of a single SARS-CoV protein can induce apoptosis in vitro.

Animals↗
PubMed2005

Quantitative detection of promoter hypermethylation in multiple genes in the serum of patients with colorectal cancer.

OBJECTIVES: While promoter hypermethylation is a common molecular alteration of human colorectal cancer that could be detected in the bloodstream, we tested the feasibility of quantitative detection of aberrant DNA methylation in multiple genes in the serum samples of colorectal cancer patients. METHODS: The pre-therapeutic serum samples of 49 colorectal cancer patients and 41 age-matched controls with normal colonoscopy were examined. The presence of methylated DNA in APC (adenomatous polyposis coli), hMLH1 (human MutL homolog 1), and HLTF (helicase-like transcription factor) was detected by quantitative methylation-specific PCR (MethyLight). RESULTS: There was a significant difference in the concentration of methylated serum DNA between cancer patients and controls for HLTF (p= 0.015) and hMLH1 (p= 0.0001) genes, but not for APC gene (p= 0.21). In total, 28 patients with colorectal cancer and 4 controls had methylated DNA detected in at least one marker, which gave a sensitivity of 57% and specificity of 90%. All patients with methylation in two methylation markers had advanced (stage III/IV) cancer (p= 0.006) and patients with methylation in at least one marker tended to have a lower probability of survival (p= 0.08). CONCLUSION: The quantitative detection of aberrant DNA methylation in serum may be a promising high-throughput approach for the noninvasive screening and monitoring of colorectal cancer.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Alveolar capillary dysplasia with congenital misalignment of pulmonary vessels.

Alveolar capillary dysplasia with misalignment of pulmonary vessels is an uncommon congenital cause of persistent pulmonary hypertension of the newborn. It is universally fatal, and diagnosis is entirely dependent upon surgical lung biopsy. We present a case of alveolar capillary dysplasia with misalignment of pulmonary vessels occurring in a full-term neonate, emphasizing that early involvement of the thoracic surgeon for a histological diagnosis allows expensive and ineffective treatments to be avoided.

Capillaries↗
PubMed2005

Epigenetic silencing of cellular retinol-binding proteins in nasopharyngeal carcinoma.

Aberrant retinoid signaling in human cancers is extending from the nucleus to the cytoplasm. Recently, we have demonstrated frequent epigenetic inactivation of a retinoic acid receptor (RAR), RARbeta2, in nasopharyngeal carcinoma (NPC). To further explore targets contributing to aberrant retinoid signaling in NPC, the expression of cellular retinol-binding proteins (CRBPs), cellular retinoic acid-binding proteins (CRABPs), RARs, and retinoid X receptors (RXRs) was examined. Apart from RARbeta2, transcriptional silencing of two CRBPs, CRBPI and CRBPIV, was observed in NPC cell lines and xenografts. Hypermethylation of CRBPI and CRBPIV CpG islands was found to be closely correlated with the loss of expression. Treatment with the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine, resulted in reexpression of CRBP1 and CRBPIV gene expression in NPC cell lines. Both CRBPI and CRBPIV hypermethylations were also observed in 43/48 (87.8%) and 26/48 (54.2%) primary NPC tumors, respectively. Here, we reported for the first time that CRBPIV was transcriptionally inactivated by promoter hypermethylation in human cancer. Simultaneous methylation of CRBPI, CRBPIV, and RARbeta2 was commonly found in NPC primary tumors. Our findings implied that epigenetic disruption of the CRBPs, CRBPI and CRBPIV, is important in NPC tumorigenesis and may contribute to the loss of retinoic acid responsiveness in cancer.

Adult↗
PubMed2005

Promoter hypermethylation of Death-associated protein-kinase gene associated with advance stage gastric cancer.

Death-associated protein kinase (DAP-kinase) is a serine/threonine kinase and a positive mediator of apoptosis. Down-regulation of DAP-kinase was associated with increased metastatic potential of tumors. Gene promoter hypermethylation could lead to down-regulation of DAP-kinase. We aimed to investigate the frequency of gene promoter methylation of DAP-kinase in gastric carcinoma (GCA) and assessed its association with clinicopathological features. One hundred and seven cases of gastric carcinoma were examined. The relevant clinical and pathological features, including survival data were reviewed. Methylation status was assessed by methylation-specific PCR (MSP). Seventy-four cases (69.2%) of GCA demonstrated promoter methylation of DAP-kinase. Methylation of DAP-kinase was observed in intestinal, diffuse and mixed type of GCA. It also occurred in similar frequency among antral, body and cardiac gastric cancer. No association between methylation status and age or gender was demonstrated. However, the methylated cases correlated with the presence of nodal metastasis (p=0.041), advance stage of disease (p=0.029) and a poorer event-free survival (log-rank test p=0.0141). DAP-kinase promoter methylation as a potential prognostic marker for gastric cancer patients deserved further evaluation.

Apoptosis Regulatory Proteins↗
PubMed2004

Detection and quantitation of human papillomavirus DNA in primary tumour and lymph nodes of patients with early stage cervical carcinoma.

Fifteen Chinese women with early stage cervical squamous cell carcinoma (14 stage IB, one stage IIA) were retrospectively analysed for the correlation between human papillomavirus (HPV) load in primary tumour and the presence of HPV DNA in histologically tumour-free pelvic lymph nodes. HPV16 DNA was detected from majority (12/15) of primary tumours, with a viral load ranging from 12 to 1800 copies per cell. Of the 156 histologically tumour-free pelvic lymph nodes, 41 (26.3%) were positive for HPV DNA. The levels of viral load detected in histologically tumour-free lymph nodes were low and most were not detectable by the less sensitive consensus PCR GP5+/6+. Among patients without histological evidence of nodal involvement, the presence of HPV DNA in lymph nodes was associated with a significantly higher viral load in primary tumour (mean [interquartile range]=800 [600-1450] versus 40 [19-70] copies per cell, P=0.016). Three of the four patients with recurrence had histological evidence of lymph node metastases. In contrast, none of the seven patients with HPV DNA-positive lymph nodes but without histologically evidence of nodal involvement developed recurrence. The results of this study suggest that the presence of HPV DNA in histologically tumour-free lymph nodes do not have prognostic significance. The HPV DNA detected from lymph nodes may have originated from circulating necrotic tumour cells or those internalized by scavengers, which was easier to be detected when the viral load per tumour cell was high.

Adult↗
PubMed2004

Promoter hypermethylation of tumor-related genes in the progression of colorectal neoplasia.

Gene promoter hypermethylation is increasingly recognized to play an important role in cancer development through silencing of gene transcription. This study determined the methylation profiles of primary colorectal cancers and adenomas to elucidate the role of epigenetic changes in different stages of colorectal carcinogenesis. We examined the methylation profiles of 47 sporadic colorectal cancers, 36 colonic adenomas from patients without cancer and 34 colonic biopsies from patients without colonic lesions. Paired adjacent dysplasia tissues obtained from 17 cancer patients were also examined. Promoter hypermethylation in 10 tumor-related genes (APC, ATM, GSTP1, HLTF, MGMT, hMLH1, p14, p15, SOCS-1 and TIMP-3) were studied by methylation-specific PCR. Promoter hypermethylation was frequently detected in more than 40% of colonic cancers and adenomas in APC, ATM, HLTF, MGMT and hMLH1 genes (p < 0.0001 vs. normal). While low level of methylation was detected in p14, p15 and TIMP-3, there was no methylation detected in GSTP1 and SOCS-1. The frequencies of methylation were comparable between tumors and adenomas, and advanced and nonadvanced adenoma. In contrast, K-ras mutation was only detected in advanced adenomas and cancers. Concurrent methylation in >/= 3 genes was found in 66.7% adenomas and 68.1% cancers but not in normal colonic tissues. Methylation was associated with reduced protein expressions in colorectal adenomas and cancers. Moreover, methylation in ATM was more common in older cancer patients (p = 0.002), but there was no significant association between promoter hypermethylation and other clinicopathologic characteristics of cancer. Our study demonstrated the early and specific involvement of promoter hypermethylation in the colorectal adenoma-carcinoma sequence.

Adenoma↗
PubMed2004

RASSF1A is a target tumor suppressor from 3p21.3 in nasopharyngeal carcinoma.

Deletion on the short arm of chromosome 3 is one of the most important genetic abnormalities in the tumorigenesis of nasopharyngeal carcinoma (NPC). Both physical mapping and functional studies have targeted an NPC-related tumor suppressor gene(s) to chromosome 3p21.3. We have reported recently that RASSF1A gene, located on a 120-kb minimal deletion region on 3p21.3, was frequently inactivated by promoter hypermethylation in NPC. We further confirmed that RASSF1A is the critical target tumor suppressor from 3p21.3, with the evidence that loss of expression and aberrant methylation of the other 8 candidate genes/transcripts (HYAL2, FUS1, RASSF1C, BLU, NPRL2, 101F6, PL6 and CACNA2D2) in this 120-kb region were rare in NPC samples. The contribution of RASSF1A in NPC tumorigenesis was investigated by restoring its expression in a RASSF1A deficient cell line, C666-1. Transient transfection of wild-type RASSF1A resulted in marked growth inhibition in NPC cells. Isolated stable clones expressing wild-type RASSF1A demonstrated retarded cell proliferation in vitro. Soft-agar assay also showed decreased number and sizes of colony formed in these clones. In vivo nude mice assay demonstrated the dramatic reduction of tumorigenic potential in the RASSF1A-transfected clones. Our results provide strong evidence to support RASSF1A as a target tumor suppressor gene on 3p21.3 in NPC.

Animals↗
PubMed2004

Persistent infection of SARS coronavirus in colonic cells in vitro.

Severe acute respiratory syndrome coronavirus (SARS-CoV) can produce gastrointestinal symptoms. The intestinal tract is the only extrapulmonary site where viable viruses have been detected. This study examined seven established human intestinal cell lines, DLD-1, HCT-116, HT-29, LoVo, LS-180, SW-480 and SW-620, for their permissiveness to SARS-CoV infection. The results showed that only LoVo cells were permissive to SARS-CoV infection as evident by positive findings from indirect immunofluorescence staining for intracellular viral antigens, in situ hybridization for intracellular viral RNA, and electron microscopy for intracellular viral particles. In contrast to Vero cells, SARS-CoV did not produce cytopathic effects on LoVo cells. However, LoVo cells were found to be highly permissive for productive infection with a high viral titre (>3 x 10(7) viral copies/ml) produced in culture supernatant following a few days of incubation. SARS-CoV established a stable persistent chronic infection that could be maintained after multiple passages. Being a cell line of human origin, LoVo cells could be a useful in vitro model for studying the biology and persistent infection of SARS-CoV. Our results on the expression of angiotensin-converting enzyme 2 (ACE2), a recently identified cellular receptor for SARS-CoV, in these cell lines indicated that it might not be the sole determinant for cells to be susceptible to SARS-CoV infection.

Angiotensin-Converting Enzyme 2↗
PubMed2004

Quantitative detection of methylated SOCS-1 , a tumor suppressor gene, by a modified protocol of quantitative real time methylation-specific PCR using SYBR green and its use in early gastric cancer detection.

Although methylation-specific PCR (MSP) is a sensitive technique in the detection of DNA hypermethylation, it is not quantitative. Here we described a modified PCR protocol to quantify methylated SOCS-1 gene by real time MSP using SYBR green, which involves an additional PCR step after the 72 degrees C extension step. This modified protocol is also useful in the quantitative detection of methylated SOCS-1 gene in serum samples of gastric cancer patients.

Adult↗
PubMed2004

Isolate diffuse thickening of glomerular capillary basement membrane: a renal lesion in prediabetes?

A total of 23 patients with proteinuria and isolated ultrastructural diffuse thickening of the glomerular capillary basement membrane were studied, focusing on the possibility of diabetes mellitus, morphometry of the capillary basement membrane, and the comparison with three other groups of patients. These included 14 patients with minimal change nephropathy (MCN), 45 patients with type II diabetes arbitrarily divided into 11 early and 34 late diabetic patients, defined, respectively, as less than 3 and over 5 years history, and 13 patients biopsied for transient mild proteinuria or hematuria, with no evidence of renal disease on follow-up were used as controls. The level of proteinuria and prevalence of hematuria were similar in patients with isolated thick basement membrane and with diabetes. Diabetic retinopathy was present in 10% of early diabetes, 69% of late diabetes, but not in isolated thick basement membrane. Kimmelstiel-Wilson nodules were seen in late diabetes, and not in other patients. Hyaline arteriosclerosis was more common in late diabetes than in early diabetes or isolated thick basement membrane. The basement membrane thickness was similar between controls (371+/-17 nm) and MCN (345+/-16 nm), between patients with isolated thick basement membrane (482+/-69 nm) and early diabetes (457+/-64 nm), but significantly thicker in isolated thick basement membrane as compared to controls and MCN. In patients with isolated thick basement membrane, the basement membrane thickness was not correlated with age, smoking, body weight, hyaline arteriosclerosis, and hypertension. However, blood tests for diabetes were positive in 20% of patients at biopsy, in 44% at 6 months and 70% at 24 months follow-up, while seven patients showed no evidence of diabetes on follow-up. Patients with proteinuria and isolated thick glomerular basement membrane must be differentiated from MCN for therapeutic implications, and specifically managed for its strong association with prediabetes or early diabetes.

Adult↗
PubMed2004

Magnetic resonance colonography in the detection of colonic neoplasm in high-risk and average-risk individuals.

OBJECTIVES: Magnetic resonance colonography (MRC) is a new noninvasive diagnostic modality for colorectal cancer. However, the use of MRC in the detection of colorectal neoplasm in average-risk individuals remains unknown. This study determined the performance and the patient's preference of MRC in the detection of colorectal neoplasm. METHODS: Both high-risk (i.e., symptoms suggestive of colorectal neoplasm, positive fecal occult blood test, history of colorectal cancer in one or more first-degree relatives) and average-risk (i.e., asymptomatic individuals >50 yr) individuals were recruited. MRC was performed immediately prior to conventional colonoscopy (CC) by using air inflation without contrast. The finding on CC together with histology was used as a gold standard. Patients' pain and discomfort score were recorded immediately and 24 h after the procedure. They were also asked about their preferences for the two procedures. RESULTS: A total of 165 patients (79 average risk and 86 high risk) were recruited. Eight patients had incomplete MRC and one patient had failed CC. Of the remaining 156 patients, 4 were found to have colonic cancer and 31 were found to have 67 polyps. MRC correctly identified 3 cancers (sensitivity 75%, specificity 99.3%) and 4 patients with colonic polyps (sensitivity 12.9% and specificity 97.6%). Sensitivity of MRC tended to be lower in polyps <10 mm in size and in average-risk individuals. The mean procedure time of CC was significantly shorter than MRC (13.6 +/- 6.7 vs 20.6 +/- 2.7 min, p < 0.001). Although there was no significant difference in the pain and discomfort scores of the 2 procedures, 75% of patients preferred CC to MRC. CONCLUSIONS: The performance of MRC when used in the detection of colonic neoplasm in average-risk individuals is unsatisfactory.

Colon↗
PubMed2004

Human metapneumovirus-associated atypical pneumonia and SARS.

Acute pneumonia developed in a previously healthy man during the outbreak of severe acute respiratory syndrome (SARS) in southern China in March 2003. Antibiotic treatment was ineffective, and he died 8 days after illness onset. Human metapneumovirus was isolated from lung tissue. No other pathogen was found. Other etiologic agents should thus be sought in apparent SARS cases when coronavirus infection cannot be confirmed.

Adult↗