Disruption of a Plasmodium falciparum gene linked to male sexual development causes early arrest in gametocytogenesis

A male gametocyte defect in the Plasmodium falciparum Dd2 parasite was previously discovered through the observation that all progeny clones in a Dd2 x HB3 genetic cross were the result of fertilization events between Dd2 female and HB3 male gametes. A determinant linked to the defect in Dd2 was subsequently mapped to an 800-kb segment on chromosome 12. Here, we report further mapping of the determinant to an 82-kb region and the identification of a candidate gene, P. falciparum male development gene 1 (pfmdv-1), that is expressed at a lower level in Dd2 compared with the wild-type normal male gametocyte-producing ancestor W2. Pfmdv-1 protein is sexual-stage specific and is located on the gametocyte plasma membrane, parasitophorous vacuole membrane, and the membranes of cleft-like structures within the erythrocyte. Disruption of pfmdv-1 results in a dramatic reduction in mature gametocytes, especially functional male gametocytes, with the majority of sexually committed parasites developmentally arrested at stage I. The pfmdv-1-knockout parasites show disturbed membrane structures, particularly multimembrane vesicles/tubes that likely derive from deformed cleft-like structures. Mosquito infectivity of the knockout parasites was also greatly reduced but not completely lost. The results suggest that pfmdv-1 plays a key role in gametocyte membrane formation and integrity.     

Changes in the breath sound spectrum with bronchodilation in children with asthma

Background

Breath sound parameters have been suggested to be new biomarkers of airway function in patients with asthma.

Species assignation of Leishmania from human and canine American tegumentary leishmaniasis cases by multilocus enzyme electrophoresis in North Argentina

Sixteen Leishmania stocks, 15 isolated from patients with cutaneous (CL), mucocutaneous (MCL), or recurrent cutaneous leishmaniasis, plus one from a dog with CL in Salta and Corrientes Provinces, Argentina, were studied by multilocus enzyme electrophoresis. Thirteen of the stocks from humans were grouped in two zymodemes; nine termed as KMS 1, four as KMS 2, and assigned to Leishmania (Viannia) braziliensis. Two additional stocks from CL cases expressed a KMS 4 enzyme profile, corresponding to L. (V.) guyanensis. Although the parasites from the dog were also assigned to L. (V.) braziliensis, its zymodeme, KMS 3, was not expressed in any of the current human isolates. The characterization of Leishmania from a dog was done for the first time in Argentina. The importance of the intraspecific polymorphism in the induction of clinical forms and in the host-reservoir concept is briefly discussed, based on the zymodeme data of isolates from humans and dogs. The presence of L. (V.) guyanensis was confirmed in the country.     

Use of urine samples from healthy humans, nephritis patients or other animals as an alternative to foetal calf serum in the culture of Leishmania (L.) donovani in vitro

The effect of supplementing in-vitro cultures of Leishmania donovani with urine was investigated. The parasites were isolated from Bangladeshi patients with visceral leishmaniasis. The urine samples used were collected from healthy human donors, patients with nephrotic syndrome, diabetic nephritis (DN) or diabetes mellitus, a dog and a cow. Promastigotes from blood-agar cultures were inoculated into RPMI-1640 basal medium with 10% heat-inactivated foetal calf serum (FCS) and/or 1%-20% urine. The parasites were then counted in a haemocytometer, on days 2, 4, 5, 6, 7, 8, 10, 12 and 14 post-inoculation. From day 4, the numbers of parasites/ml in cultures containing 5% healthy-human urine but no FCS were at least as high as those in cultures containing 10% FCS but no urine (P = 0.191). The wet weights of parasites harvested from mass cultures of the parasites in RPMI-1640 plus 5% healthy-human urine and in RPMI-1640 plus 10% FCS were practically the same. Multiplication of the parasites in the presence of 5% urine from a DN patient was significantly greater (P < 0.01) than that seen with other urine samples at the same concentration or with 10% FCS. The multiplication seen with 8% canine urine was almost the same as with 5% healthy-human urine. Parasites could be maintained in RPMI-1640 plus 5% healthy-human urine for at least 40 days, sub-culturing every 4 days. Urine may be a better and much cheaper stimulant of Leishmania multiplication in vitro than FCS.     

Enhanced calcium-sensitivity of erythrocytes in hypertension--calcium-induced changes of erythrocyte osmotic fragility in essential hypertension

To investigate the Ca-sensitivity of the erythrocyte membrane in hypertension, the changes of the osmotic fragility of erythrocytes by Ca-loading and the effects of Ca-channel blockers or calmodulin-antagonist were observed in patients with essential hypertension. Erythrocytes were obtained from untreated patients with essential hypertension and age-matched normotensive subjects. Treatment of erythrocytes with Ca-ionophore A23187 and Ca in bathing medium caused the reduction of the osmotic fragility of erythrocytes dose-dependently on Ca-concentration. The degree in alteration of the osmotic fragility of erythrocytes was greater in essential hypertension than that in normotensive controls. In addition, Ca-induced changes of erythrocyte osmotic fragility was inversely correlated with the plasma renin activity in essential hypertension. In the presence of Ca-antagonists (verapamil, diltiazem) or calmodulin-antagonist (trifluoperazine), the reduction of the osmotic fragility of erythrocytes by Ca-loading was inhibited, and the differences of the osmotic fragility of erythrocytes between the hypertensives and the normotensive controls were abolished by these drugs. These results suggest that the greater changes of the osmotic fragility of the erythrocytes by Ca-loading in essential hypertension might be due to the abnormality of Ca-handling of the cell membranes causing an increase in the intracellular Ca concentration, contributing at least partially to the pathogenesis of hypertension.     

Air exposure causes oxidative stress in cultured bovine tracheal epithelial cells and produces a change in cellular glutathione systems

An air-liquid interface culture system accelerates cell differentiation and growth in airway epithelial cells. In this study, the authors investigated whether glutathione (GSH) affects cell growth in an air-liquid interface culture. Various components of the cellular GSH system were measured and the number of cells was counted after conversion from an immersed feeding to an air-liquid interface. The effect of medium supplementation with cystine, a precursor of GSH, on cell growth was also examined. After conversion to an air-liquid interface, the cellular GSH level increased by 4 to 5-fold. The increase in GSH preceded the rise in cell number. The glutathione disulfide (GSSG)/total GSH ratio (an indicator of oxidative stress) increased initially and reached a plateau (time 0: 0.379%+/-0.054%; day 2: 0.824%+/-0.063%; day 6: 0.806%+/-0.093%). The level of glutathione reductase activity in the cells increased in a time-dependent manner, whereas the glutathione peroxidase activity level declined. When the amount of cystine in the medium was varied after conversion, the cellular GSH level was closely correlated with the rate of cell growth. In conclusion, air exposure causes oxidative stress in cultured cells and produces a change in the cellular glutathione system, resulting in the promotion of cell growth.