Suppression of A-type potassium current in pyramidal neurons of the rat hippocampus, induced by pinacidil and its fluorine derivatives

With the use of a patch-clamp technique in the whole-cell configuration, we studied the effects of pinacidil and its fluorine derivatives on A-type potassium current (I _A) through the membrane of pyramidal neurons of the rat hippocampus. Hydrogen peroxide (10 mM) exerted no influence on the rate of inactivation ofI _A; therefore, this current is probably mediated by Shal Kv4.2 potassium channels. Pinacidil demonstrated the properties of a weakI _A blocker: in the 500 μM concentration it blocked about 45% of the current, while 50 μM of pinacidil fluorine derivatives were capable of blocking up to 30% ofI _A. The effects of pinacidil and its derivatives showed no dependence on the stimulating potential. A similar pattern of the effects of pinacidil fluorine derivatives, which are an order of magnitude stronger than those of pinacidil itself, allows us to suppose that the imine nitrogen of the tested compounds is significantly more involved in the molecular interaction with the site of an A-type potassium channel than the pyridine nitrogen.     

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.     

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.     

MV-mimicking micelles loaded with PEG-serine-ACP nanoparticles to achieve biomimetic intra/extra fibrillar mineralization of collagen in vitro

Since their discovery, matrix vesicles (MVs) containing minerals have received considerable attention for their role in the mineralization of bone, dentin and calcified cartilage. Additionally, MVs' association with collagen fibrils, which serve as the scaffold for calcification in the organic matrix, has been repeatedly highlighted. The primary purpose of the present study was to establish a MVs–mimicking model (PEG-S-ACP/micelle) in vitro for studying the exact mechanism of MVs-mediated extra/intra fibrillar mineralization of collagen in vivo. In this study, high-concentration serine was used to stabilize the amorphous calcium phosphate (S-ACP), which was subsequently mixed with polyethylene glycol (PEG) to form PEG-S-ACP nanoparticles. The nanoparticles were loaded in the polysorbate 80 micelle through a micelle self-assembly process in an aqueous environment. This MVs–mimicking model is referred to as the PEG-S-ACP/micelle model. By adjusting the pH and surface tension of the PEG-S-ACP/micelle, two forms of minerals (crystalline mineral nodules and ACP nanoparticles) were released to achieve the extrafibrillar and intrafibrillar mineralization, respectively. This in vitro mineralization process reproduced the mineral nodules mediating in vivo extrafibrillar mineralization and provided key insights into a possible mechanism of biomineralization by which in vivo intrafibrillar mineralization could be induced by ACP nanoparticles released from MVs. Also, the PEG-S-ACP/micelle model provides a promising methodology to prepare mineralized collagen scaffolds for repairing bone defects in bone tissue engineering.