Search PubMed⌕ Search

Biomedical subjects

C Y Tong

Publications and source records attributed to C Y Tong.

At least 37 records · Page 2Linked to original sources
PubMed1997

Evaluation of two simplified methods for genotyping hepatitis C virus.

A number of different approaches have been used for genotyping hepatitis C virus (HCV). Two simplified methods were evaluated, both of which used polymerase chain reaction (PCR) to amplify products from the 5' non-coding region of HCV: non-isotopic restriction fragment length polymorphism (RFLP) analysis and type-specific PCR. Sixty-four viraemic patients suffering from chronic HCV infection were studied using these two techniques; 25/64 samples were further tested with a commercial serotyping ELISA based on synthetic NS4 antigen (Murex, U.K.). The results of the three typing methods were generally in agreement with each other. When only the predominant genotype identified by each method was analysed, the 3 methods had 100% agreement. RFLP did not detect any mixed infections and it was unsuccessful in 16/64 (25%) samples. Both type-specific PCR and serotyping ELISA detected mixed infections. However, serotyping ELISA did not give typeable results in 7/25 (28%) samples, whereas type-specific PCR gave typeable results in all 64 samples. Type-specific PCR detected more mixed infections than serotyping ELISA. Direct sequencing of four PCR products with indeterminate RFLP confirmed changes in restriction enzyme recognition sites. The sequences also confirmed the validity of the predominant genotype in cases of apparent mixed infections. It is possible that some of these cases were artefacts as a result of quasispecies.

Base Sequence↗
PubMed1997

Hepatitis G virus RNA and its relation to hepatitis C infection in adult haemophilic patients.

The prevalence of hepatitis C virus (HCV) infection and hepatitis G virus (HGV) RNA were studied in 50 adult haemophilic patients who had received commercial clotting factors prior to 1980. HGV RNA was detectable in 6/ 50 patients (12%); 49/50 (98%) had antibody to HCV and 40/49 (82%) of these were viraemic with detectable HCV RNA; 5/6 patients with detectable HGV RNA had co-existing HCV infection and viraemia. The HGV PCR products from all six patients were directly sequenced and all were shown to be similar to that of HGV but more diverse from that of GB virus C. One patient who had persistent abnormal liver function tests had detectable HGV RNA but no evidence of hepatitis B or C. The presence of HGV RNA in the absence of hepatitis B and C infection indicates that this virus is capable of independent transmission. Independent response to interferon was demonstrated in one patient with co-infection who lost HGV but not HCV after interferon therapy.

Adolescent↗
PubMed1997

Impact of HIV on mortality from acute lower respiratory tract infection in rural Zambia.

AIMS: To establish the prevalence and clinical correlates of HIV among children with acute lower respiratory tract infection. METHODS: Children admitted to a rural Zambian hospital were studied over an eight month period. The diagnosis of acute lower respiratory tract infection was made clinically, according to World Health Organisation (WHO) criteria. Clinicians, who were unaware of the children's HIV status, prescribed antibiotic and supportive treatment according to WHO guidelines. HIV status was established using the polymerase chain reaction (Amplicor HIV1, Roche) applied to dried blood spots. RESULTS: Acute lower respiratory tract infection was diagnosed in 132 children (median age 8 months, range 1 month to 4 years). The WHO criteria for severe or very severe pneumonia were met by 96/132 patients (73%) and 21 patients (16%) died. HIV dried blood spot PCR was positive in 14 cases (11%), of whom four fulfilled the WHO clinical case definition for paediatric AIDS and five died. The group as a whole were malnourished, but the HIV positive children were more severely malnourished (mean z score for weight = -3.01) than the HIV negative children (mean z score = -1.73, p < 0.001). The relative risk of death was 2.6 in the HIV positive group but this was not significant (p = 0.079). CONCLUSIONS: An important minority of children with acute lower respiratory tract infection in rural Zambia will be infected with HIV. However, most HIV positive children presenting with respiratory infection will survive given simple antibiotic and supportive treatment.

AIDS-Related Opportunistic Infections↗
PubMed1997

Lowering the cut off value of an automated chlamydia enzyme immunoassay and confirmation by PCR and direct immunofluorescent antibody test.

AIMS: To increase the sensitivity of an automated chlamydia enzyme immunoassay by significantly lowering its cut off value, and to maintain specificity by confirmation with polymerase chain reaction (PCR) and direct immunofluorescent antibody test (DFA). METHODS: Over five months, the cut off value of the enzyme immunoassay used to screen urogenital samples for chlamydia antigen was reduced from 80 to 10. Samples with a test value of 10 or above were further tested with a commercial PCR assay. All samples during the first three months and discrepant samples during the last two months of the study were also tested with the DFA. RESULTS: 3250 urogenital swabs (1246 urethral, 1335 endocervical, 669 pooled urethral/endocervical) from 1246 males and 2004 females were processed. Using the manufacturer's recommended cut off of 80, the enzyme immunoassay identified chlamydia antigen in 134 samples (4.1%). Using the lower cut off value of 10 and either PCR or DFA as the confirmatory test, Chlamydia trachomatis was identified in 178 samples (5.5%). Thus, 45 additional positive samples were identified and the confirmed detection rate was increased by 33.8% (45/133). Excluding equivocal PCR results, the concordance between DFA and PCR was 91.8%. This strategy increased the detection rate by 2.1% in men and 0.9% in women (significant only in men). In female patients, pooled urethral/endocervical swabs as a specimen gave a significantly higher yield than endocervical swabs regardless of whether the lower cut off strategy was used. CONCLUSIONS: This strategy of significantly lowering the cut off test value with confirmation on the same specimen by either PCR or DFA is feasible and cost effective. The use of pooled urethral/ endocervical specimens in females should be considered routinely as detection rate was significantly improved.

Chlamydia Infections↗
PubMed1996

Comparison of an automated enzyme immunoassay with a direct fluorescent antibody test and polymerase chain reaction for the detection of Chlamydia trachomatis in diagnostic specimens from male patients.

Endourethral swabs and first-pass urine (FPU) samples from 148 male patients were tested for Chlamydia trachomatis by an automated enzyme immunoassay (EIA) (Vidas; bioMérieux, France), a direct fluorescent antibody (DFA) test (MicroTrak; Syva, USA) and two polymerase chain reaction (PCR) methods. Chlamydia trachomatis was considered present if a specimen was positive by at least two methods. This expanded criterion identified 27 patients (18%) as truly infected. One of the PCR methods was most sensitive for both types of specimen. When the recommended cut-off value of Vidas was reduced by 50%, its sensitivity on endourethral swabs was comparable to that of the DFA test, but the DFA test performed better with FPU. In general, FPU was suitable only for PCR.

Chlamydia Infections↗
PubMed1996

The occurrence of hepatitis B and C viruses in Pakistani patients with chronic liver disease and hepatocellular carcinoma.

To study the occurrence of hepatitis B virus (HBV) and hepatitis C virus (HCV) in patients with chronic liver disease (CLD) and hepatocellular carcinoma (HCC) in Pakistan, blood samples from 105 sequential patients with biopsy-proven CLD (n = 82) and HCC (n = 23) were tested for HBV and HCV markers. Of the 105, 87 (83%) had evidence of hepatitis B exposure, 58 (55%) were positive for hepatitis B surface antigen (HBsAg), 23 (22%) had hepatitis C antibodies and 25 (24%) had detectable HCV RNA. Significantly more patients with HCC had evidence of HBV exposure in the absence of HCV markers (49/82 vs. 20/23, odds ratio 4.49, 95% CI 1.17-25.16). The proportion of patients positive for HBsAg with no HCV markers was also significantly higher in the HCC group (34/82 vs. 18/23, odds ratio 5.08, 95% CI 1.59-18.96). There were more patients with only HCV markers in the CLD group than the HCC group but the difference was not statistically significant (19/82 vs. 1/23, odds ratio 6.63, 95% CI 0.93-288.01). A modified non-isotopic restriction fragment length polymorphism study on PCR products was used to investigate the epidemiology of HCV genotypes in Pakistan. Due to depletion of the initial samples, a second series of specimens collected one year afterwards was used. Fifteen out of 40 samples had amplifiable product and all were identified as type 3. A commercial serological typing method on the same samples also confirmed that type 3 was the predominant HCV genotype in Pakistan.

Adolescent↗
PubMed1995

Effect of respiratory virus infections including rhinovirus on clinical status in cystic fibrosis.

One hundred and eight patients with cystic fibrosis were investigated over one year to determine whether an association existed between rhinovirus or other respiratory virus infection and clinical status. Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), Shwachman score, Chrispin-Norman chest radiograph score, and percentage weight for height were recorded at the beginning and end of the study; days of intravenous antibiotics were noted. Nasopharyngeal aspirates were taken for viral studies during respiratory exacerbations. Serum was collected at enrollment and 2-6 weeks after each respiratory exacerbation. One hundred and fifty seven exacerbations occurred in 76 patients. Respiratory virus infection was detected in 44 exacerbations and rhinovirus was present in 16% (25/157) of exacerbations. Patients with one or more respiratory virus infections were compared with those who had none. When all respiratory virus infections were considered, patients had a significantly greater deterioration in Shwachman score and received significantly more days of intravenous antibiotics. When rhinovirus was considered separately, patients received significantly more days of intravenous antibiotics, but showed no deterioration in clinical status. However, patients infected with another respiratory virus had a significant decline in FEV1, with trends towards significance for decline in FVC and Shwachman score.

Adolescent↗
PubMed1993

Techniques for the measurement of the local myocardial extraction efficiency for inert diffusible contrast agents such as gadopentate dimeglumine.

We have previously shown that the concentration of Gd-DTPA as a function of time ([Gd-DTPA]t(t)) in the myocardium following an intravenous bolus injection of Gd-DTPA can be modeled using the Modified Kety Equation. Fitting this model to measurements of [Gd-DTPA]t(t) in a region of myocardium would allow the determination of myocardial distribution volume (lambda) and the product of flow (F) and extraction efficiency (E), i.e., FE. Thus, to measure F, E must be known. We describe here techniques developed to measure local values of E in normal and diseased myocardium. These techniques are valid for any inert diffusible MR contrast agent.

Animals↗
PubMed1993

Measurement of the extraction efficiency and distribution volume for Gd-DTPA in normal and diseased canine myocardium.

We have previously shown that the myocardial Gd-DTPA concentration ([Gd-DTPA]t(t)) after a bolus injection of Gd-DTPA can be predicted by the Modified Kety Equation (MKE). If [Gd-DTPA]t(t) can be determined by MRI and the data fit to the MKE, then the distribution volume (lambda) of Gd-DTPA and the myocardial flow (F) times the extraction efficiency (E), i.e., the FE product, can be determined. Therefore F can only be quantified if E is known. We measured the global E in vivo in normal canine myocardium, and measured E and lambda, in vitro, locally in normal, acute ischemic (n = 5; coronary artery occlusion < 4 h), infarcted (n = 4; coronary artery occlusion, 6 days) and reperfused (n = 4; coronary artery occlusion 2 h, and reperfusion 2 h and 6 days) myocardium. Results indicate that E differs with F and with individuals and consequently, F cannot be quantified using the MKE unless the local E is also determined in vivo.

Animals↗
PubMed1993

Detection of Chlamydia pneumoniae and Chlamydia psittaci in sputum samples by PCR.

AIMS: To use the polymerase chain reaction (PCR) to detect Chlamydia pneumoniae and Chlamydia psittaci in sputum samples. METHODS: A nested PCR was developed, the first stage of which amplified DNA from both C pneumoniae and C psittaci while the second stage targeted specifically at C pneumoniae, allowing the two species to be differentiated. The primers were designed not to amplify sequences from C trachomatis. A panel of 26 sputum samples from patients with community acquired pneumonia evaluated previously by enzyme linked immunosorbent assay (ELISA), direct immunofluorescence (DIF), and culture was tested blind by PCR. Most of these specimens also had accompanying serial serum samples which were tested for species specific antibodies using microimmunofluorescence (micro-IF). RESULTS: PCR detected C pneumoniae DNA in 10 of the 26 samples and C psittaci DNA in four. There was good concordance between ELISA, DIF, micro-IF and PCR in the C pneumoniae group. Two of the C psittaci identified by PCR were labelled C pneumoniae by DIF but the PCR results were supported by serology or a history of bird contact. Of the PCR negative group: six were true negative results; two contained C trachomatis. There were four discrepant results. CONCLUSIONS: The data suggest that PCR is effective in the detection of C pneumoniae. The sensitivity for C psittaci is inevitably lower due to the strategy taken but specificity seemed to be good.

Bacterial Outer Membrane Proteins↗
PubMed1991

Site of hemodynamic effects of intrathecal alpha 2-adrenergic agonists.

Intrathecally administered alpha 2-adrenergic agonists produce analgesia in humans but may also produce hypotension and bradycardia. To further characterize hemodynamic depression produced by intrathecally administered alpha 2-adrenergic agonists, clonidine (100-1,500 micrograms) was injected into the cervical, thoracic, or lumbar intrathecal space of conscious sheep. Only thoracic intrathecal clonidine injection (100 or 300 micrograms) decreased blood pressure, whereas these doses did not affect blood pressure when injected at other sites. A greater clonidine dose (1,500 micrograms) increased blood pressure to a similar degree at all sites. Hypotension after thoracic intrathecal clonidine injection was inhibited by pretreatment with the alpha 2-adrenergic antagonist idazoxan (1 mg, intrathecally) or the depleter of acetylcholine stores hemicholinium-3 (2 mg, intrathecally), suggesting an action at alpha 2-adrenoceptors on cholinergic preganglionic sympathetic neurons. ST-91, a polar clonidine analog, did not decrease blood pressure after thoracic intrathecal injection. Intrathecal injection of the muscarinic receptor agonist carbamylcholine increased blood pressure. These data describe a complex action of intrathecal alpha 2-adrenergic agonists on hemodynamic parameters that is dependent on site of injection, drug dose, and drug lipophilicity; that can be explained by anatomic factors; and that may possibly be exploited to minimize hemodynamic depression from these agents.

Adrenergic alpha-Agonists↗