Ligand-selective activation of mu-oid receptor: demonstrated with deletion and single amino acid mutations of third intracellular loop domain

The mechanism for the differential regulation of the mu-opioid receptor by agonists is investigated by identifying the receptor domains used to define the relative efficacies of three mu-opioid receptor-selective agonists: [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO), morphine, and [N-MePhe3,D-Pro4]-morphiceptin (PL017) to inhibit forskolin-stimulated intracellular cAMP production in human embryonic kidney 293 cells. This was accomplished by systematically deleting four to five amino acids clusters within the third intracellular loop of rat mu-opioid receptor, Arg258 to Arg280, followed by Ala substitution and scanning studies of the 276RRITR280 sequence, the putative G protein-coupling motif. Deletion of the four to five amino acid clusters resulted in differential effects on the affinities of the agonists and antagonists, and also on the potencies and coupling efficiencies of the three opioid agonists. Ala scanning studies of the 276RRITR280 sequence revealed also the differences between [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO), morphine, and PL017. Substitution of Arg276 or Ile278 with Ala reduced the potency of DAMGO but not that of morphine PL017. Meanwhile, mutation of Thr279 to Ala increased the potencies of morphine and PL017 but not that of DAMGO. The I278A mutation decreased the DAMGO coupling efficiency but increased the PL017 coupling efficiency. The R280A mutation resulted in the increase in PL017 potency and coupling efficiency without altering those of DAMGO and morphine. Thus, these mutation studies suggested that the activation of mu-opioid receptor and interaction between the critical domains such as RRITR within third intracellular loop and the G proteins are agonist-selective.     

Viral hepatitis infections among dialysis patients: Thailand registry report

BACKGROUND: Patients on dialysis are at high risk of acquiring viral hepatitis infections. However, there were only few data from Thailand. The aim of the present study was to assess the prevalence, incidence and associated risk factors of viral hepatitis infections among dialysis patients. METHODS: A retrospective study was conducted to evaluate 5179 medical records of dialysis patients from the Thailand Renal Replacement Therapy Registry. RESULTS: In 2002, the seroprevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections were 6.3% (n = 2454) and 4.8% (n = 2167), respectively. HBV and HCV seroprevalence became 6.5% (n = 2585) and 4.3% (n = 2399) in 2003. The incidence of HBV and HCV infections were 1.5 and 2.4 cases per 1000 patient-years, respectively. Logistic regression analysis showed that age and gender were significant risk factors for HBV infection, but not for HCV infection. CONCLUSION: In Thailand, it was not uncommon for dialysis patients to acquire viral hepatitis infections. However, our prevalence is similar to reports from some other South-East Asian countries.     

Antihypertensive effect of BS 100–141, a new central acting antihypertensive agent

A double-blind comparison between BS 100–141 and placebo in 36 hypertensive patients of Thai or Thai-Chinese origin revealed that the preparation lowers the elevated blood pressure within the first week of treatment in most patients. The drug was relatively well tolerated and caused mild side effects only. After a sudden discontinuation of the drug, the blood pressure in four of the 19 patients increased within a few days to pretreatment values or slightly above. The occurrence of rebound hypertension cannot be excluded. Interruption of treatment, therefore, should be made gradually.     

HIV-1 drug resistance in Thailand: before and after National Access to Antiretroviral Program.

BACKGROUND: The Ministry of Public Health (Thailand), MoPH, has had a program called National Access to Antiretroviral Program for People who have AIDS (PHA) or "NAPHA", to offer free antiretroviral drugs (ARV), which are locally produced in Thailand, to any HIV-1 infected patients with CD4<200 since 2002. This program may increase usage of ARV therapy and the emergence of HIV-1 drug resistance. OBJECTIVES: To monitor HIV-1 ARV drug resistant codon mutation in Thailand before and after the "NAPHA" program. MATERIALS AND METHODS: EDTA blood samples were collected from 542 HIV-1 infected subjects, who received ARV therapy in 1999 and 2001-2003, and perinatal chemoprophylaxis in 1998 and 2000. HIV-1 pol nucleotide sequences were analyzed. RESULTS: The percentage of drug resistant detection from the ARV therapy group in 1999 and 2001-2003 were 12.14 (34/280), 10.23 (9/88), 86.96 (20/23) and 57.55 (61/106), respectively. Of 332 NRTI drug resistant codon mutation, 226 (68.07%) were thymidine analogue mutations (TAMs). The percentage of TAMs detection in 1999 and 2001-2003 were 7.14 (20/280), 9.09 (8/88), 56.52 (13/23) and 43.34 (46/106), respectively. Of 105 NNRTI drug resistant codon mutation, 95 (90.48%) were related to nevirapine drug resistance. CONCLUSION: Thailand may need more appropriate monitoring of drug resistance in the free ARV therapy program to protect the future usage of drugs by minimizing the emergence of drug resistance.     

Usage of dried blood spots for molecular diagnosis and monitoring HIV-1 infection

The usage of dried blood spots as specimens for diagnosis and monitoring of HIV-1 infection in Thailand was evaluated. EDTA blood samples, which were collected from 100 HIV seronegative and 109 HIV seropositive individuals, were tested on dried blood spots; Whatman, Schleicher and Schuell (S&S) No. 903 and S&S IsoCode filter paper. Nucleic acid was extracted and used as a template for HIV-1 proviral DNA detection by an "in-house" multiplex PCR and a commercial Amplicor HIV-1 PCR test (Roche, version 1.0). HIV-1 RNA qualitative (QL) and quantitative (QT) detection was determined by Nucleic Acid Sequence Based Amplification (NASBA). The average DNA per blood spot recovered from Whatman and S&S IsoCode was not statistically different (p = 0.512) with a range of 218.9+/-46.84 and 225.63+/-88.33 microg, respectively. The concordance of HIV-1 proviral DNA detection by PCR from dried blood spots Whatman and S&S IsoCode was 94% versus 89.4% for sensitivity and 100% versus 100% for specificity. The sensitivity and specificity of HIV-1 RNA QL detection in dried blood spots was 89.7 and 97.5%, respectively. The HIV-1 RNA QT from dried blood spots showed a good correlation in paired dried blood spots and plasma with Pearson correlation, r = 0.817 (R2 = 0.667, P < 0.05). The data showed that dried blood spots could be used for the diagnosis and monitoring of HIV-1 infection.     

Efficacy of Artequick versus artesunate-mefloquine in the treatment of acute uncomplicated falciparum malaria in Thailand

To determine the efficacy, safety and tolerability of an alternative short-course, artemisinin-based combination therapy for acute uncomplicated Plasmodium falciparum malaria, we compared Artequick--a fixed-dosed combination of artemisinin (80 mg), piperaquine (400 mg), and primaquine (4 mg), per tablet--with a standard regimen of artesunate-mefloquine. A total of 130 patients were randomly assigned to treatment with an orally administered, once-daily, 3-day regimen of either Artequick (Group A: 3.2 mg/Kg/day of artemisinin, 16 mg/Kg/day of piperaquine, and 0.16 mg/Kg/day of primaquine) or artesunate-mefloquine (Group B: artesunate, 4 mg/Kg/day, with mefloquine, 8 mg/Kg/day). Patients receiving each regimen had a rapid clinical and parasitological response. All treatments were well tolerated, and no serious adverse effects occurred. No significant differences were found in fever- and parasite-clearance times between the two study groups. The 28-day cure rates were similarly high, at 98.5% and 100%, in groups A and B, respectively. We conclude that Artequick was as effective and well tolerated as artesunate-mefloquine and could be used as an alternative treatment for multidrug-resistant Plasmodium falciparum malaria in Southeast Asia.     

Serotype distribution and antimicrobial susceptibility of S. pneumoniae causing invasive disease in Thai children younger than 5 years old, 2000-2005

In order to predict the potential benefit of pneumococcal conjugate vaccines (PCV), we evaluated the serotype coverage of the 7-, 9-, 11- and 13-valent PCV over the isolates causing invasive pneumococcal disease (IPD) in Thai children. One hundred and fifteen Streptococcus pneumoniae isolates from sterile sites in children younger than 5 years old between 2000 and 2005 were serotyped. The coverages of 7-, 9-, 11-, and 13-valent PCV were 69%, 73.8%, 73.8% and 85.7% in children younger than 2 years, and 73.9%, 77.4%, 77.4% and 87.8% in children younger than 5 years of age, respectively. 69.6% and 22.6% of the isolates were non-susceptible to penicillin and cefotaxime. 7-valent PCV covered 89% and 100% of penicillin and cefotaxime non-susceptible isolates.     

Dose ranging studies of new artemisinin-piperaquine fixed combinations compared to standard regimens of artemisisnin combination therapies for acute uncomplicated falciparum malaria

To determine the optimum dose of artemisinin-piperaquine combination therapies for acute uncomplicated Plasmodium falciparum malaria, we examined 7 candidate regimens in 411 patients admitted to the Bangkok Hospital for Tropical Diseases. The studies were performed from May 2005 to October 2005 and November 2005 to June 2006. We compared 3-day courses of artesunate-mefloquine, artemether-lumefantrine (Coartem) and of dihydroartemisinin-piperaquine (Artekin) as reference antimalarial treatments, with candidate regimens using 2-3 day courses of artemisinin-piperaquine, Artequick. Initially, patients receiving each of the regimens had a rapid clinical and parasitological response. All treatments were well tolerated and no serious adverse effects occurred. The 28-day cure rates were < 80% for the 2-day treatments with artemisinin-piperaquine at 2.4 mg/kg and 14.4 mg/kg, respectively, in the first study period and artemisinin-piperaquine at 3.2 mg/kg and 16.0 mg/kg, respectively, but > 98% for the 3-day regimens. These results suggest that a 3-day course of artemisinin-piperaquine at 3.2 mg/kg and 16.0 mg/kg, respectively, deserve further evaluation as an alternative treatment for multidrug-resistant P. falciparum malaria.