Comparison of hematin-targeting properties of pynacrine,an acridine analog of the benzonaphthyridine antimalarial pyronaridine

The hematin-targeting properties of pynacrine, an acridine analog of the schizontocidal antimalarial drug, pyronaridine, were evaluated to probe the role of the latter's benzonaphthyridine moiety. Pynacrine was as active as pyronaridine in inhibiting glutathione-induced hematin degradation and in enhancing hematin-mediated membrane lysis. It formed a 1:2 complex with hematin but was 50-fold less effective in inhibiting β-hematin formation. However, pynacrine was as potent as pyronaridine in inhibiting intra-erythrocytic Plasmodium falciparum growth in culture, suggesting that it has other off-target(s) effects.     

Robust colorimetric detection based on the anti-aggregation of gold nanoparticles for bromide in rice samples

Inorganic bromide (Br⁻) is an important contaminant ion as it can originate from the overuse of illegal methyl bromide as a fumigant in stored rice samples. Herein, we developed a simple and highly sensitive colorimetric sensor for bromide ion detection in rice samples. The sensor is based on the anti-aggregation of gold nanoparticles (AuNPs) by Br⁻ in the presence of Cr³⁺, which made the method more selective than other typical aggregations of nanoparticles. The AuNPs underwent an aggregation process as a result of the coordination of Cr³⁺ and the carboxylate group of a citrate ion stabilized the AuNPs, resulting in a red-to-blue color change. When Br⁻ was pre-mixed with the AuNPs and Cr³⁺ was added, the solution color changed from blue to red with an increase in the Br⁻ concentration. The anti-aggregation process can be detected with the naked eye and monitored using UV-vis spectrophotometry. The linear calibration curve ranged between 0.31 and 3.75 μM Br⁻ with a low LOD and LOQ of 0.04 and 0.13 μM. The recovery was excellent, ranging from 79.9–92.2% with an RSD of less than 4.0%. The good inter-day and intra-day precisions were 2.9–6.4% and 3.1–7.1%, respectively. The developed sensor has proved to provide a robust method for Br⁻ detection in rice samples.

In this work, we developed a AuNP colorimetric sensor for the facile, sensitive and selective detection of bromide ions in rice samples.     

Immunophenotypic discrepancies between granulocytic and erythroid lineages in peripheral blood of patients with paroxysmal nocturnal haemoglobinuria

Abstract: In paroxysmal nocturnal haemoglobinuria (PNH), somatic mutation of the PIG‐A gene is thought to result in altered expression of glycosylphosphatidylinositol (GPI)‐anchored proteins. This study was performed to determine if there were any heterogeneities of cellular phenotypes between two major peripheral blood cells, erythrocytes and granulocytes. Using CD59‐based immunocytometry, the patterns of CD59 expression were shown to be conserved in the circulating erythroid cells (reticulocytes and mature erythrocytes) in all 29 patients with PNH. Twenty‐one patients had distinct combinations of PNH type I, II, and III cells in different lineages. Only eight patients exhibited similar patterns of CD59 expression between the two lineages. Approximately one third of the patients had PNH type II cells in either or both of the two lineages indicating variable lineage involvement. The proportion of abnormal granulocutes was higher than those of abnormal reticulocytes and erythrocytes. In patients with appropriate erythropoietic responses to haemolysis (RPI>2.0), shift reticulocytes display predominantly PNH phenotypes. These immature erythroid cells with altered expression of GPI‐anchored proteins may dominate the peripheral blood during periods of increased marrow activity resulting in greater phenotypic mosaicism in such patients. Discrepancies in expression of GPI‐anchored proteins in PNH which are highly variable between the two lineages may be the result of their different life spans and the influence of complement‐mediated cytolysis. The phenomena also indicated the possible occurrence of more than one PNH clones with variable clonal dominance.     

Cyquant cell proliferation assay as a fluorescence-based method for in vitro screening of antimalarial activity

The appearance of drug resistant parasites and the absence of an effective vaccine have resulted in the need for new effective antimalarial drugs. Consequently, a convenient method for in vitro screening of large numbers of antimalarial drug candidates has become apparent. The CyQUANT cell proliferation assay is a highly sensitive fluorescence-based method for quantitation of cell number by measuring the strong fluorescence produced when green GR dye binds to nucleic acids. We have applied the CyQUANT assay method to evaluate the growth of Plasmodium falciparum D6 strain in culture. The GR-nucleic acid fluorescence linearly correlated with percent parasitemia at both 0.75 or 1 percent hematocrit with the same correlation coefficient of r2 = 0.99. The sensitivity of P. falciparum D6 strain to chloroquine and to 3,6-bis-omega-diethylaminoamyloxyxanthone, a novel antimalarial, determined by the CyQUANT assay were comparable to those obtained by the traditional [3H]-ethanolamine assay: IC50 value of chloroquine was 54 nM and 51 nM by the CyQUANT and [3H]-ethanolamine assay, respectively; IC50 value for 3,6-bis-omega-diethylaminoamyloxyxanthone was 254 nM and 223 nM by the CyQUANT and [3H]-ethanolamine assay, respectively. This procedure requires no radioisotope, uses simple equipment, and is an easy and convenient procedure, with no washing and harvesting steps. Moreover, all procedures can be set up continuously and thus, the CyQUANT assay is suitable in automatic high through-put drug screening of antimalarial drugs.     

Comparison of colorimetry and electrothermal atomic absorption spectroscopy for the quantification of non-transferrin bound iron in human sera

This paper describes a comparison of two analytical techniques, one employing bathophenanthrolinedisulfonate (BPT), a most commonly-used reagent for Fe (II) determination, as chromogen and an electrothermal atomic absorption spectroscopy (ETAAS) for the quantification of non-transferrin bound iron (NTBI) in sera from thalassemic patients. Nitrilotriacetic acid (NTA) was employed as the ligand for binding iron from low molecular weight iron complexes present in the serum but without removing iron from the transferrin protein. After ultrafiltration the Fe (III)-NTA complex was then quantified by both methods. Kinetic study of the rate of the Fe (II)-BPT complex formation for various excess amounts of NTA ligand was also carried out. The kinetic data show that a minimum time duration (> 60 minutes) is necessary for complete complex formation when large excess of NTA is used. Calibration curves given by colorimetric and ETAAS methods were linear over the range of 0.15-20 microM iron (III). The colorimetric and ETAAS methods exhibited detection limit (3sigma) of 0.13 and 0.14 microM, respectively. The NTBI concentrations from 55 thalassemic serum samples measured employing BPT as chromogen were statistically compared with the results determined by ETAAS. No significant disagreement at 95% confidence level was observed. It is, therefore, possible to select any one of these two techniques for determination of NTBI in serum samples of thalassemic patients. However, the colorimetric procedure requires a longer analysis time because of a slow rate of exchange of NTA ligand with BPT, leading to the slow rate of formation of the colored complex.     

In vitro susceptibility of Trichomonas vaginalis to AT-specific minor groove binding drugs

Trichomoniasis is one of the most common sexually transmitted diseases, with around 120 million world-wide suffering from Trichomonas vaginalis-induced vaginitis every year. Although trichomoniasis can be treated with metronidazole, the prevalence of metronidazole-resistant T. vaginalis seems to be increasing. Since the percentage of AT base pairs in T. vaginalis DNA (71%) is very much higher than in human cells, in this study a series of bisquaternary quinolinium salt compounds with high AT-binding specificity were tested for their antitrichomonal activities. Minimum inhibitory concentrations (MICs) were determined for these compounds against a local strain of T. vaginalis in culture. Among 14 bisquaternary quinolinium compounds tested, an N-ethyl derivative was the most effective drug against T. vaginalis, being nearly as potent (MIC = 0.16 microM) as metronidazole (MIC = 0.096 microM), and with low toxicity towards human cells. The nature of the substitution at the quinolinium quaternary centre appears to be important in terms of effectiveness of bisquaternary compounds against the parasite. In contrast, no clear relationships could be seen for substituents on the quinolinium ring; Me and Cl substituted analogues showed higher activity against trichomonads, whereas OMe, NHMe and NH2 substituents decreased activity.     

Alteration in bone marrow RNA of vitamin E-deficient monkey, Macaca fascicularis.

In anemic crab-eating monkeys, Macaca fascicularis, there is an alteration in the bone marrow RNA species resulting from early vitamin E deficiency, when compared with those from normal simian bone marrow or from phenylhydrazine-induced anemic bone marrow of rabbit. Anemia of vitamin E deficiency is specifically associated with a reduction in the ribosomal RNA content.     

Targeting of hematin by the antimalarial pyronaridine

Pyronaridine, 2-methoxy-7-chloro-10[3',5'-bis(pyrrolidinyl-1-methyl-)4'hydroxyphenyl]aminobenzyl-(b)-1,5-naphthyridine, a new Mannich base schizontocide originally developed in China and structurally related to the aminoacridine drug quinacrine, is currently undergoing clinical testing. We now show that pyronaridine targets hematin, as demonstrated by its ability to inhibit in vitro beta-hematin formation (at a concentration equal to that of chloroquine), to form a complex with hematin with a stoichiometry of 1:2, to enhance hematin-induced red blood cell lysis (but at 1/100 of the chloroquine concentration), and to inhibit glutathione-dependent degradation of hematin. Our observations that pyronaridine exerted this mechanism of action in situ, based on growth studies of Plasmodium falciparum K1 in culture showing antagonism of pyronaridine in combination with antimalarials (chloroquine, mefloquine, and quinine) that inhibit beta-hematin formation, were equivocal.