Biomedical subjects

M Chan

Publications and source records attributed to M Chan.

168 records · Page 10Linked to original sources

PubMedDate not supplied

Characterization of ATP-dependent Ca2+ transport in the basolateral membrane vesicles from proximal and distal tubules of the rabbit kidney.

Basolateral membrane vesicles were prepared from purified proximal and distal tubules of the rabbit kidney. The properties of the ATP-dependent Ca2+ transport were investigated. In both membranes, there was a high affinity, ATP-dependent Ca2+ transport system (Km = 0.1 microM). The optimal concentration of Mg2+ was 0.5 mM and the optimal concentration of ATP was 1 mM. The nucleotide specificity and pH dependence of the Ca2+ transport in both membranes were similar. In basolateral membrane vesicles, calmodulin had no effect on Ca2+ transport. However, in basolateral membrane vesicles depleted of calmodulin, exogenous calmodulin increased the Ca2+ transport by increasing maximal velocity. There were no major differences in the properties of the ATP-dependent Ca2+ transport system in these two membranes. These findings are discussed in relation to why parathyroid hormone differentially modulates Ca2+ transport in these two segments of the nephron.

Adenosine Triphosphate↗

PubMedDate not supplied

What determines survival duration in hepatocellular carcinoma treated with intraarterial Yttrium-90 microspheres?

BACKGROUND/AIMS: The survival duration of patients with nonresectable hepatocellular carcinoma confined to the liver and treated with intraarterial yttrium-90 microspheres was highly variable. METHODOLOGY: Eighty-two patients treated by this method were analyzed. Thirty-one patients who lived for one year or longer from the date of first treatment were classified as 'long survivors' and 51 patients who died within 1 year were classified as 'short survivors'. RESULTS: Comparison between the 2 categories suggested that lower pretreatment level of alpha-fetoprotein and higher tumor-to-normal uptake ratio of yttrium-90 microspheres favored longer survival. Results also indicated that the treatment was effective even for large tumors and for postoperative recurrence. Repeated treatment of viable residual or recurrent tumors offered further palliation and prolongation of survival. CONCLUSIONS: Pretreatment alpha-fetoprotein level, tumor-to-normal uptake ratio of yttrium-90 microspheres and the number of treatments determine survival duration.

Adult↗

PubMedDate not supplied

Presence of p53 mutation in human cervical carcinomas associated with HPV-33 infection.

In this present study, we report the mutation of the p53 gene in vivo in human primary carcinomas of cervix and cervical intraepithelial neoplasia (CIN). The association of the HPV subtypes with the tumors was determined by multiplex primer polymerase chain reaction (PCR) amplification. The mutation of the p53 gene was detected using PCR amplification of the p53 exons followed by SSCP (single strand conformation polymorphism) and DNA sequencing analysis. The p53 mutation was detected in two out of two HPV-33 positive carcinomas but was absent in the HPV-16/-18 positive carcinomas (0 out of 8 cases). The p53 mutation was also detected in one out of four HPV-negative cervical carcinomas. No mutation of the p53 gene was detected in the CIN specimens (0 out of 7 cases). The two mutations in the HPV-33 associated cervical carcinoma were detected at codon 273 (CGT to TGT; arginine to cysteine) and intron 5 (24 base pair downstream of the 3' end of exon 5). The p53 mutation at codon 273 has been previously reported in one of the HPV-negative cervical carcinoma cell line (C33A). Our results indicate that mutation of the p53 gene is not a common event in human cervical cancers (3/14), and may be related to the infection of HPV-16/18 in the tumor. However, mutation of the p53 gene was detected in cervical carcinomas associated with HPV-33 and may be an important genetic event in this subgroup of carcinomas.

Amino Acid Sequence↗

PubMedDate not supplied

Positioning effects on arterial oxygen and relative pulmonary shunt in patients receiving mechanical ventilation after CABG.

OBJECTIVE: To examine the effects of three different positions on arterial oxygen and relative pulmonary shunt in patients after coronary artery bypass graft (CABG) who are receiving mechanical ventilation with an effective tidal volume of 15 ml/kg and a minimum of 5 cm H2O positive end-expiratory pressure. DESIGN: Repeated measures, counterbalanced. SETTING: Adult cardiovascular intensive care unit in a major tertiary referral hospital. SUBJECTS: Convenience sample of 30 patients who had undergone CABG, 90% of whom had postoperative atelectasis. OUTCOME MEASURES: Partial pressure arterial oxygen (PaO2) and relative pulmonary shunt (areas of low ventilation-perfusion ratio). INTERVENTION: Supine, right lateral, and left lateral positions with head of bed elevated 30 degrees. RESULTS: No statistically significant differences in arterial oxygen and relative pulmonary shunt were found among the three positions. CONCLUSIONS: For a selected cohort, positioning may not be an important consideration in arterial oxygenation in patients who have undergone CABG and are receiving mechanical ventilation with a high tidal volume and positive end-expiratory pressure.

Adult↗

PubMedDate not supplied

Evaluation of a competitive ELISA for detection of antibodies against avian influenza virus nucleoprotein.

A competitive enzyme-linked immunosorbent assay (C-ELISA) employing a baculovirus-expressed recombinant nucleoprotein and a monoclonal antibody was developed for the detection of antibodies to type A influenza virus nucleoprotein. The performance of the C-ELISA was evaluated by testing 756 chickens, 1123 turkeys, 707 emus, and 1261 ostriches, for a total of 3847 serum samples. Relative to the agar gel immunodiffusion (AGID) test, the C-ELISA had a sensitivity of 100% for all four species. The C-ELISA's sensitivity relative to the hemagglutination-inhibition (HI) test results was 100% for chicken, turkey, and emu and 96.2% for the ostrich serum samples. More than 90% of the AGID-negative/C-ELISA-positive serum samples were found positive by HI for at least one influenza serotype. The specificity of C-ELISA relative to AGID ranged from 85.5% to 99.8% for sera collected from these species. These results indicated that the C-ELISA was more sensitive and more specific than the AGID test and as sensitive and as specific as the HI test. The C-ELISA has the potential to replace the AGID test for screening sera from avian species, including ratites, for detection of antibodies to type A influenza virus.

Animals↗

PubMedDate not supplied

Evaluation of antibody responses of emus (Dromaius novaehollandiae) to avian influenza virus infection.

Emu antibody responses to avian influenza virus (AIV) infection were evaluated by the competitive enzyme-linked immunosorbent assay (C-ELISA), agar gel immunodiffusion (AGID) and hemagglutination inhibition (HI) tests. All birds infected with AIV H5N1, H5N3, or H7N7 developed antinucleoprotein (NP) antibodies as early as 7 days postinfection as detected by the C-ELISA. The responses lasted 49 days for the emus receiving H5N3 and at least 56 days for emus receiving the other two viruses. By evaluating 50 emu field serum samples, the C-ELISA was found more sensitive than the AGID test for the detection of anti-NP antibodies. This study indicates that emus experimentally infected with AIV developed antibody responses that can be detected by C-ELISA, AGID, and HI tests. The results from this and our previous studies demonstrate the use of the C-ELISA as a substitute for the AGID test in a routine serodiagnostic screening for detection of antibodies to AIV infection in multiple avian species.

Animals↗