Growing momentum in the molecular study of ion channels.

Long the sole domain of physiologists and electrical engineers, ion channel biophysics is going molecular, and with a vengeance. This summary of a recent meeting devoted to ion channel biophysics shows that the integration of techniques, reinforced by active communication among scientists of diverse backgrounds, is extremely potent.     

Mitochondrial glutathione modulates TNF-alpha-induced endothelial cell dysfunction.

The effect of glutathione (GSH) depletion by L-buthionine-[S,R]-sulphoximine (BSO) on tumor necrosis factor-alpha (TNF-alpha)-induced adhesion molecule expression and mononuclear leukocyte adhesion to human umbilical vein endothelial cells (HUVECs) was investigated. Cells with marked depletion of cytoplasmic GSH, but with an intact pool of mitochondrial GSH, only slightly enhanced TNF-alpha-induced E-selectin and vascular cell adhesion molecule-1 (VCAM-1) expression, compared with the control. However, TNF-a-induced expression of both molecules was markedly enhanced when the mitochondrial GSH pool was diminished to <15% of the control. In contrast, TNF-alpha-induced intercellular adhesion molecule-1 (ICAM-1) expression was not affected by the depletion of either cytoplasmic or mitochondrial GSH. Marked enhancement of TNF-alpha-induced adhesion molecule expression by the depletion of mitochondrial GSH resulted in increased in mononuclear leukocyte adhesion to treated HUVECs, compared with the control. These effects parallel reactive oxygen species (ROS) formation by the depletion of mitochondrial but not cytoplasmic GSH. Our findings demonstrate that depletion of mitochondrial GSH renders more ROS generation in HUVECs, and mitochondrial GSH modulates TNF-alpha-induced adhesion molecule expression and mononuclear leukocyte adhesion in HUVECs.     

Phylogenetic revision of Agapophytinae subf.n. (Diptera: Therevidae) based on molecular and morphological evidence

Agapophytinae subf.n. is a highly diverse lineage of Australasian Therevidae, comprising eight described and two new genera: Agapophytus Guérin‐Méneville, Acupalpa Kröber, Acraspisa Kröber, Belonalys Kröber, Bonjeania Irwin & Lyneborg, Parapsilocephala Kröber, Acatopygia Kröber, Laxotela Winterton & Irwin, Pipinnipons gen.n. and Patanothrix gen.n. A genus‐level cladistic analysis of the subfamily was undertaken using sixty‐eight adult morphological characters and c. 1000 base pairs of the elongation factor‐1α (EF‐1α) protein coding gene. The morphological data partition produced three most parsimonious cladograms, whereas the molecular data partition gave a single most parsimonious cladogram, which did not match any of the cladograms found in the morphological analysis. The level of congruence between the data partitions was determined using the partition homogeneity test (HT_F) and Wilcoxon signed ranks test. Despite being significantly incongruent in at least one of the incongruence tests, the partitions were combined in a simultaneous analysis. The combined data yielded a single cladogram that was better supported than that of the individual partitions analysed separately. The relative contributions of the data partitions to support for individual nodes on the combined cladogram were investigated using Partitioned Bremer Support. The level of support for many nodes on the combined cladogram was non‐additive and often greater than the sum of support for the respective nodes on individual partitions. This synergistic interaction between incongruent data partitions indicates a common phylogenetic signal in both partitions. It also suggests that criteria for partition combination based solely on incongruence may be misleading. The phylogenetic relationships of the genera are discussed using the combined data. A key to genera of Agapophytinae is presented, with genera diagnosed and figured. Two new genera are described: Patanothrix with a new species (Pat. skevingtoni) and Pat. wilsoni (Mann) transferred from Parapsilocephala, and Pipinnipons with a new species (Pip. kroeberi). Pipinnipons fascipennis (Kröber) is transferred from Squamopygia Kröber and Pip. imitans (Mann) is transferred from Agapophytus. Agapophytus bicolor (Kröber) is transferred from Parapsilocephala. Agapophytus varipennis Mann is synonymised with Aga. queenslandi Kröber and Aga. flavicornis Mann is synonymised with Aga. pallidicornis (Kröber).     

Evidence that free GPI glycolipids are essential for growth of Leishmania mexicana.

The cell surface of the parasitic protozoan Leishmania mexicana is coated by glycosylphosphatidylinositol (GPI)-anchored glycoproteins, a GPI-anchored lipophosphoglycan and a class of free GPI glycolipids. To investigate whether the anchor or free GPIs are required for parasite growth we cloned the L.mexicana gene for dolichol-phosphate-mannose synthase (DPMS) and attempted to create DPMS knockout mutants by targeted gene deletion. DPMS catalyzes the formation of dolichol-phosphate mannose, the sugar donor for all mannose additions in the biosynthesis of both the anchor and free GPIs, except for a alpha1-3-linked mannose residue that is added exclusively to the free GPIs and lipophosphoglycan anchor precursors. The requirement for dolichol-phosphate-mannose in other glycosylation pathways in L.mexicana is minimal. Deletion of both alleles of the DPMS gene (lmdpms) consistently resulted in amplification of the lmdpms chromosomal locus unless the promastigotes were first transfected with an episomal copy of lmdpms, indicating that lmdpms, and possibly GPI biosynthesis, is essential for parasite growth. As evidence presented in this and previous studies indicates that neither GPI-anchored glycoproteins nor lipophosphoglycan are required for growth of cultured parasites, it is possible that the abundant and functionally uncharacterized free GPIs are essential membrane components.     

A Novel Flow Cytometric Hemozoin Detection Assay for Real-Time Sensitivity Testing of Plasmodium falciparum

Resistance of Plasmodium falciparum to almost all antimalarial drugs, including the first-line treatment with artemisinins, has been described, representing an obvious threat to malaria control. In vitro antimalarial sensitivity testing is crucial to detect and monitor drug resistance. Current assays have been successfully used to detect drug effects on parasites. However, they have some limitations, such as the use of radioactive or expensive reagents or long incubation times. Here we describe a novel assay to detect antimalarial drug effects, based on flow cytometric detection of hemozoin (Hz), which is rapid and does not require any additional reagents. Hz is an optimal parasite maturation indicator since its amount increases as the parasite matures. Due to its physical property of birefringence, Hz depolarizes light, hence it can be detected using optical methods such as flow cytometry. A common flow cytometer was adapted to detect light depolarization caused by Hz. Synchronized in vitro cultures of P. falciparum were incubated for 48 hours with several antimalarial drugs. Analysis of depolarizing events, corresponding to parasitized red blood cells containing Hz, allowed the detection of parasite maturation. Moreover, chloroquine resistance and the inhibitory effect of all antimalarial drugs tested, except for pyrimethamine, could be determined as early as 18 to 24 hours of incubation. At 24 hours incubation, 50% inhibitory concentrations (IC50) were comparable to previously reported values. These results indicate that the reagent-free, real-time Hz detection assay could become a novel assay for the detection of drug effects on Plasmodium falciparum.