Molecular cytogenetics of introgressive hybridization in plants

Introgressive hybridization (introgression) is genetic modification of one species by another through hybridization and repeated backcrossing. Introgression is important in the evolution of flowering plants. It is also important in plant breeding where a desirable trait can be transferred from wild to crop species. One of the most recent advances in molecular techniques for studying hybridization and introgression is in situ hybridization of genomic probes to cytological preparations (GISH, genomic in situ hybridization). The present paper describes a successful GISH protocol for detection of intergenomic introgression in breeding materials and in allopolyploid species. In addition, the paper introduces a new possibility of using dispersed repeats to detect introgression and to gain insights into its molecular basis. The approach is referred to as dFISH for dispersed fluorescence in situ hybridization, and the best candidate for this type of probes is probably a retroelement. Southern hybridization data are also presented to support the effectiveness of GISH and dFISH for introgression mapping.     

Development of oral pharmaceutical formulation of standardized crude ethanolic extract of Atractylodes lancea (Thunb) DC.

Cholangiocarcinoma (CCA), the adenocarcinoma of the biliary duct, is commonly reported in Asia with the highest incidence in northeastern Thailand. Chemotherapy of this type of cancer is limited due to the lack of effective chemotherapeutic drugs. A series of previous studies support further research and development of Atractylodes lancea (Thunb) DC. (AL) as a potential candidate for the treatment of CCA as a crude ethanolic extract. In the present study, we aimed to develop an oral pharmaceutical formulation (capsule) of the standardized AL crude ethanolic extract for further clinical development in patients with CCA. Major steps included macroscopic and microscopic authentication of the AL rhizomes, preparation of standardized AL extract, preparation of oral pharmaceutical formulation (capsule) of the standardized AL extract, quantitative and qualitative analysis of the marker compound (atractylodin) in the formulated AL extract, evaluation of contaminations of heavy metals, pesticides residues, and microorganisms in the ground AL rhizomes and the formulated (capsule) powder of AL, physicochemical and pharmaceutical properties of the formulatedAL extract/capsule, and cytotoxicity evaluation of the formulated AL extract. Results of all evaluations confirmed satisfactory pharmaceutical properties of oral (capsule) formulation of the standardized AL extract.     

Therapeutic potential and pharmacological activities of Atractylodes lancea (Thunb.) DC.

The rhizome of Atractylodes Iancen(A.lancea)(Thunb.) DC.(AL)is extensively used in Chinese,Thai,and Japanese traditional medicines as crude extracts/decoctions or a component in various herbal formulations.Various pharmacological activities of Al.and its major constituents have been demonstrated in ritro.ex ciro.and in animal models.Results from the toxicity studies in animal models suggest safety profile of AL,and its active constituents.Despite extensive use with positive impression in many diseases,there has not been a clinical study that can conclusively support its efficacy and safely profile in human.This review comprehensively summarizes current information on the pharmacological activities of AL and their active constituents including anticancer,anti-inflammatory,antimicrobial and antipyretic activities,as well as activities on central nervous,cardiovascular,and gastrointestinal systems.     

Anticancer activity using positron emission tomography‐computed tomography and pharmacokinetics of β‐eudesmol in human cholangiocarcinoma xenografted nude mouse model

Cholangiocarcinoma (CCA) is an important public health problem in several parts of South East Asia, particularly in Thailand. The limited availability of effective diagnostic tools for early stage CCA, including chemotherapeutic options, constitutes a major problem for treatment and control of CCA. The aim of the present study was to assess the anti‐CCA activity and pharmacokinetics of β‐eudesmol in CCA‐xenografted nude mouse model and healthy mice. Positron emission tomography‐computed tomography (PET‐CT) with ¹⁸F‐fluorodeoxyglucose was used for detecting and monitoring tumour development, and PET‐CT with technetium‐99m was used to investigate its pharmacokinetics property. Results support the role of PET‐CT as a potential tool for detecting and monitoring the progress of lung metastasis. Tumour size and lung metastasis were significantly inhibited by 91.6% (of baseline) and 95% (of total lung mass), respectively, following treatment with high‐dose β‐eudesmol (100 mg/kg body weight for 30 days). Survival time was prolonged by 64.4% compared with untreated controls. Systemic clearance of the compound was rapid, particularly during the first 60 min. The compound was distributed to the vital organs at maximum levels 2 h after oral administration and 15 min after intravenous injection. Results from the present study suggest the potential of β‐eudesmol as a promising candidate for further development as an anti‐CCA drug with respect to its pharmacodynamics and pharmacokinetic properties. PET‐CT, with radiotracers ¹⁸F‐fluorodeoxyglucose and technetium‐99m, was shown to be a reliable tool in the investigation of anti‐CCA and pharmacokinetic properties of β‐eudesmol in CCA‐xenografted and healthy mice.     

Comparative study of the effectiveness and pharmacokinetics of two rectal artesunate/oral mefloquine combination regimens for the treatment of uncomplicated childhood falciparum malaria

BACKGROUND: Rectal artesunate has been shown to be an effective treatment for falciparum malaria and is useful in patients who cannot take medicine orally or when parenteral medication is inconvenient. A combination with mefloquine can decrease the duration of treatment, increase compliance and delay development of resistance. There are no clear data on whether a higher dosage of rectal artesunate results in a better clinical response. AIM: To assess two rectal artesunate/oral mefloquine regimens for treating uncomplicated multi-drug-resistant childhood falciparum malaria. METHODS: Seventy children aged 1-14 years with uncomplicated falciparum malaria were randomly assigned to receive either 10 (range 8-12) or 20 (range 16-24) mg/kg/day rectal artesunate for 3 days followed by 25 mg/kg oral mefloquine. The study endpoints were fever clearance time, parasite clearance time and proportion of patients with recrudescence. Serum levels of artesunate and dihydro-artemisinin were measured after the first dose of rectal artesunate in 16 subjects. RESULTS: Both regimens were safe and effective. The cure rate was 100% in the 53 patients who completed 28-day follow-up. All of the study endpoints were comparable between both treatment groups. CONCLUSION: A regimen of rectal artesunate 10 mg/kg/day for 3 days followed by mefloquine 25 mg/kg is optimal for the treatment of uncomplicated falciparum malaria. There was no definite benefit from increasing the dosage of rectal artesunate from 10 to 20 mg/kg/day.     

The pharmacokinetics,safety and tolerability of the co-administration of diethylcarbamazine and albendazole

The pharmacokinetics, safety and tolerability of single, oral doses of diethylcarbamazine (DEC) and albendazole, given alone or in combination, were investigated in a double-blind, randomized and placebo-controlled trial involving 42 amicrofilaraemic subjects living in an area of India where lymphatic filariasis is endemic. The subjects (34 males and eight females, aged 18-52 years and weighing 46-66.5 kg) were randomly allocated to one of the three drug groups. Fourteen were given just DEC (6 mg/kg), another 14 were given just albendazole (400 mg) and the remaining 14 were given both DEC (6 mg/kg) and albendazole (400 mg). Blood samples for pharmacokinetic study were collected at specified intervals before and after drug administration. Plasma concentrations of DEC and albendazole/albendazole sulphoxide were estimated using gas chromatography and HPLC, respectively. The safety and tolerability of the treatments were evaluated through clinical and laboratory assessments. Both the DEC and albendazole were well tolerated when given alone or in combination, no adverse events being observed. In all three treatment groups, the drugs were rapidly absorbed from the gastro-intestinal tract although there was marked inter-individual#10; variation. The pharmacokinetics of DEC, albendazole and albendazole sulphoxide were similar, whether each drug was given alone or in combination. These results indicate that there is no adverse pharmacokinetic or pharmacodynamic reason why DEC and albendazole should not be co-administered to control lymphatic filariasis.     

Association between the pfmdr1 gene and in vitro artemether and lumefantrine sensitivity in Thai isolates of Plasmodium falciparum

We evaluated the influence of pfmdr1 mutations and copy number on in vitro artemether and lumefantrine sensitivity in 101 laboratory and adapted Thai isolates of Plasmodium falciparum. Approximately one-fourth of these isolates exhibited reduced lumefantrine susceptibility. We found that both mutations and amplification of the pfmdr1 gene influenced in vitro artemether and lumefantrine sensitivity. Using multivariate analysis, 184F or 1042N alleles and a copy number of ≥ 4 were identified as the independent markers for decreased lumefantrine susceptibility. Separate analysis also indicated that parasites from different geographical areas were influenced by different genetic markers.     

CYP2A6 genotypes and coumarin-oxidation phenotypes in a Thai population and their relationship to tobacco smoking

Objective  To investigate the association between polymorphisms in the human CYP2A6 gene, CYP2A6 enzyme activity and the influence of cigarette smoking in a Thai population. Methods  Coumarin (5 mg capsule) was administered to 194 healthy Thai subjects. Genetic variation of the CYP2A6 gene was identified using PCR methods. The excreted dose of 7-hydroxycoumarin (as a percentage of the urine concentration) 2 h after administration was calculated as an index of coumarin metabolism. Results  The frequencies of CYP2A6 alleles *1A, *1B, *4C, *7, *8, *9 and *10 were 34.0, 35.3, 9.3, 6.4, 0.5, 12.1 and 2.4%, respectively. Of the 194 subjects tested, the number (percentages) of Thai participants classified as ultra-rapid, extensive, intermediate and poor metabolizers were 8 (4.1%), 159 (82.0%) 22 (11.3%) and five (2.6%), respectively. Conclusion  A relationship between the interindividual differences in coumarin metabolism and genetic polymorphisms of the CYP2A6 gene was observed.     

Clinical application of mefloquine pharmacokinetics in the treatment of P falciparum malaria

Summary— Malaria remains a major public health problem in large areas of the world. One of the major factors responsible for the resurgence is the emergence of Plasmodium falciparum, resistant to available antimalarials. An antimalarial, mefloquine, has been considered since its introduction as a promising alternative antimalarial drug to overcome the situation of widespread multidrug resistant P falciparum. Pharmacokinetic studies of mefloquine have been investigated in several groups of subjects either as mefloquine alone or as combined regimens. The oral absorption of mefloquine is relatively rapid, reaching peak concentrations within 24 hours. Metabolism takes place in the liver, with carboxymefloquine as a major metabolite. Mefloquine has a large apparent volume of distribution of 200 L and is highly bound (98%) to plasma proteins. The elimination is slow; the terminal half-life is 13 10 to 14 days in Thai patients with falciparum malaria. Vomiting within 1 hour of drug administration has an influence on blood concentrations of mefloquine and this may result in treatment failure. The whole blood concentrations of mefloquine on the first two days of treatment are important determinants of parasitological response. There appear to be no pharmacokinetic interactions between mefloquine and the other two components of Fansimef^R in patients with uncomplicated falciparum malaria. The advantage of this combination over mefloquine alone in multidrug resistant P falciparum is still debatable. However, recent data seem to support the higher efficacy of Fansimef^R over mefloquine alone. Concurrent administration of antibiotics, ie ampicillin and tetracycline with mefloquine results in a significant increase in maximum concentration, reduction of the apparent volume of distribution and shortening of the terminal elimination half-life of mefloquine. An antiemetic drug metoclopramide accelerates the absorption of mefloquine and increases the maximum concentration. In contrast, mefloquine concentrations are decreased in the presence of an antimalarial, artesunate. Primaquine has no effect on the pharmacokinetics of mefloquine when given concurrently.