Zoledronic acid is synergic with vinblastine to induce apoptosis in a multidrug resistance protein-1 dependent way: an in vitro study

We have explored the action of zoledronic acid, which has an apoptotic effect and is used as an agent for treating skeletal metastases and osteoporosis, in the presence of vinblastine, and whether this effect is associated with MRP-1 (multidrug resistance protein-1) expression. HEK (human embryonic kidney) 293 cells were transfected to form the multidrug resistant cell line designated 293MRP (MRP-1 expressing HEK293 cells). Both lines were treated with varying concentrations of vinblastine and zoledronic acid. Apoptosis was determined by the TUNEL (deoxyuridine triphosphate nick end-labeling) method. The type of treatment, MRP-1 expression status, and the type of treatment with respect to MRP-1 expression status significantly affected (P < 0.001) the degree of apoptosis. The largest increase in cytotoxicity was noted in HEK293 cells, when 100 micromol zoledronic acid was added to 4 microg/ml vinblastine (an increment of 80.3%, P < 0.001). This preliminary work shows that zoledronic acid acts synergistically with vinblastine to induce apoptosis in an MRP-1 dependent way.     

Joint analysis of the DRD5 marker concludes association with attention-deficit/hyperactivity disorder confined to the predominantly inattentive and combined subtypes

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable, heterogeneous disorder of early onset, consisting of a triad of symptoms: inattention, hyperactivity, and impulsivity. The disorder has a significant genetic component, and theories of etiology include abnormalities in the dopaminergic system, with DRD4, DAT1, SNAP25, and DRD5 being implicated as major susceptibility genes. An initial report of association between ADHD and the common 148-bp allele of a microsatellite marker located 18.5 kb from the DRD5 gene has been followed by several studies showing nonsignificant trends toward association with the same allele. To establish the postulated association of the (CA)(n) repeat with ADHD, we collected genotypic information from 14 independent samples of probands and their parents, analyzed them individually and, in the absence of heterogeneity, analyzed them as a joint sample. The joint analysis showed association with the DRD5 locus (P=.00005; odds ratio 1.24; 95% confidence interval 1.12-1.38). This association appears to be confined to the predominantly inattentive and combined clinical subtypes.     

Strongyloidiasis associated with amebiasis and giardiaisis in an immunocompetent boy presented with acute abdomen

Strongyloides stercoralis (SS) is an intestinal nematode that is mainly endemic in tropical and subtropical regions and sporadic in temperate zones. SS infection frequently occurs in people who have hematologic malignancies, HIV infection and in individuals undergoing immunosuppressive therapy. In this study, we report a 12- year-old immunocompetent boy who was admitted to our hospital with acute abdomen. Laboratory evaluation showed strongyloidiasis, amebiasis and giardiasis. Clinical and laboratory findings immediately improved with albendazole therapy. Therefore, when diarrhea with signs of acute abdomen is observed, stool examinations should be done for enteroparasitosis. This approach will prevent misdiagnosis as acute abdomen. Complete clinical improvement is possible by medical therapy without surgical intervention.     

Linkage of the efflux-pump expression level with substrate extrusion rate in the MexAB-OprM efflux pump of Pseudomonas aeruginosa

The amount of the subunit proteins of the MexAB-OprM efflux pump in Pseudomonas aeruginosa was quantified by the immunoblotting method. A single cell of the wild-type strain contained about 2500, 1000, and 1200 copies of MexA, MexB, and OprM, respectively, and their stoichiometry therefore was 2:1:1. The mexR mutant produced an eightfold higher level of these proteins than did wild-type cells. Assuming that MexB and OprM exist as a trimer in a pump assembly, the total number of MexAB-OprM per wild-type cell was calculated to be about 400 assemblies. The substrate efflux rate of MexAB-OprM was calculated from the fluorescent intensity of ethidium in intact cells that a single cell extruded ethidium at a maximum of about 3 x 10(-19) mol s(-1) and, therefore, the turnover rate of a single pump unit was predicted to be about 500 s(-1).     

Cytoadherence and sequestration in Plasmodium falciparum: defining the ties that bind

Infected erythrocytes containing the more mature stages of the human malaria Plasmodium falciparum may adhere to endothelial cells and uninfected red cells. These phenomena, called sequestration and rosetting, respectively, are involved in both host pathogenesis and parasite survival. This review provides a critical summary of recent advances in the characterization of the molecules of the infected red blood cell involved in adhesion, i.e. parasite-encoded molecules (PfEMP1, MESA, rifins, stevor, clag 9, histidine-rich protein), a modified host membrane protein (band 3) and exofacial exposure of phosphatidylserine, as well as receptors on the endothelium, i.e. thrombospondin, CD36, ICAM-1 (intercellular adhesion molecule), and chondroitin sulfate.     

Symbiotic Bradyrhizobium japonicum Reduces N2O Surrounding the Soybean Root System via Nitrous Oxide Reductase

N₂O reductase activity in soybean nodules formed with Bradyrhizobium japonicum was evaluated from N₂O uptake and conversion of ¹⁵N-N₂O into ¹⁵N-N₂. Free-living cells of USDA110 showed N₂O reductase activity, whereas a nosZ mutant did not. Complementation of the nosZ mutant with two cosmids containing the nosRZDFYLX genes of B. japonicum USDA110 restored the N₂O reductase activity. When detached soybean nodules formed with USDA110 were fed with ¹⁵N-N₂O, they rapidly emitted ¹⁵N-N₂ outside the nodules at a ratio of 98.5% of ¹⁵N-N₂O uptake, but nodules inoculated with the nosZ mutant did not. Surprisingly, N₂O uptake by soybean roots nodulated with USDA110 was observed even in ambient air containing a low concentration of N₂O (0.34 ppm). These results indicate that the conversion of N₂O to N₂ depends exclusively on the respiratory N₂O reductase and that soybean roots nodulated with B. japonicum carrying the nos genes are able to remove very low concentrations of N₂O.     

Effects of gene dosage and sequence modification on the frequency and timing of transposition of the maize element Activator (Ac) in tobacco

The effect of Ac copy number on the frequency and timing of germinal transposition in tobacco was investigated using the streptomycin phosphotransferase gene (SPT) as an excision marker. The activity of one and two copies of the element was compared by selecting heterozygous and homozygous progeny of transformants carrying single SPT::Ac inserts. It was observed that increasing gene copy not only increases the transposition frequency, but also occasionally alters the timing of transposition such that earlier events are obtained. The result is that some homozygous plants generate multiple streptomycin resistant progeny carrying the same transposed Ac (trAc) element. We have also investigated the effect of modification of the sequence in the region around 82 bp downstream of the polyadenylation site and 177 bp from the 3 end of the element on germinal excision frequencies. Alteration of three bases to create a BglII site at this location caused a minor decrease in germinal excision events, but insertion of four bases to create a Cla I site caused a 10-fold decrease in the transposition activity of the Ac element.     

Direct participation of potassium ion in the catalysis of coenzyme B(12)-dependent diol dehydratase.

The direct ion-dipolar interactions between potassium ion (K(+)) and the two hydroxyl groups of the substrate are the most striking feature of the crystal structure of coenzyme B(12)-dependent diol dehydratase. We carried out density-functional-theory computations to determine whether K(+) can assist the 1,2-shift of the hydroxyl group in the substrate-derived radical. Between a stepwise abstraction/recombination reaction proceeding via a direct hydroxide abstraction by K(+) and a concerted hydroxyl group migration assisted by K(+), only a transition state for the latter concerted mechanism was found from our computations. The barrier height for the transition state from the complexed radical decreases by only 2.3 kcal/mol upon coordination of the migrating hydroxyl group to K(+), which corresponds to a 42-fold rate acceleration at 37 degrees C. The net binding energy upon replacement of the K(+)-bound water for substrate was calculated to be 10.7 kcal/mol. It can be considered that such a large binding energy is at least partly used for the substrate-induced conformational changes in the enzyme that trigger the homolytic cleavage of the Co-C bond of the coenzyme and the subsequent catalysis by a radical mechanism. We propose here a new mechanism for diol dehydratase in which K(+) plays a direct role in the catalysis.