Polycystin-1 activates and stabilizes the polycystin-2 channel

Autosomal dominant polycystic kidney disease (ADPKD) is a prevalent genetic disorder largely caused by mutations in the PKD1 and PKD2 genes that encode the transmembrane proteins polycystin-1 and -2, respectively. Both proteins appear to be involved in the regulation of cell growth and maturation, but the precise mechanisms are not yet well defined. Polycystin-2 has recently been shown to function as a Ca(2+)-permeable, non-selective cation channel. Polycystin-2 interacts through its cytoplasmic carboxyl-terminal region with a coiled-coil motif in the cytoplasmic tail of polycystin-1 (P1CC). The functional consequences of this interaction on its channel activity, however, are unknown. In this report, we show that P1CC enhanced the channel activity of polycystin-2. R742X, a disease-causing polycystin-2 mutant lacking the polycystin-1 interacting region, fails to respond to P1CC. Also, P1CC containing a disease-causing mutation in its coiled-coil motif loses its stimulatory effect on wild-type polycystin-2 channel activity. The modulation of polycystin-2 channel activity by polycystin-1 may be important for the various biological processes mediated by this molecular complex.     

Effect of phosphocreatine on H+ extrusion,pHi and dimorphism in Candida albicans

Candida albicans is an opportunistic pathogen. Its proliferation in human hosts is believed to be controlled by immunologic mechanisms. The plasma membrane of the fungus possesses an H(+)-ATPase (PM-ATPase) which actively extrudes protons to generate an electrochemical gradient which is used in co-transport of nutrients. This ATPase is associated with the growth, dimorphism and pathogenicity of the fungus. The physiological concentration of phosphocreatine (PCr) is 20-35 mM in skeletal muscles. H(+)-extrusion in Candida cells was strongly inhibited by PCr; 44% at 20 mM and 69% at 40 mM. H(+)-extrusion was stimulated 6.2-fold in the presence of 10 mM glucose. This glucose stimulated extrusion was inhibited significantly by PCr; 36% at 20 mM and 53% at 40 mM. The intracellular pH pattern of cells destined to differentiate was greatly altered in the presence of PCr. Evagination time for control cells was between 90-120 min. PCr, delayed dimorphism, reduced the population of cells differentiating to hyphae and also reduced the length of hyphae after each time interval. Only 60% differentiation was observed with 10 mM PCr and 40% for higher PCr concentration even after 210 min. Direct interaction of PM-ATPase and PCr has been demonstrated by difference spectrum measurement employing stopped flow spectrophotometer. It can be concluded that PCr may be playing a significant role in checking growth and pathogenesis of C. albicans.     

Coming to grips with integrin binding to ligands

Integrins are alphabeta heterodimeric cell-surface receptors that are vital to the survival and function of nucleated cells. They recognize aspartic-acid- or a glutamic-acid-based sequence motifs in structurally diverse ligands. Integrin recognition of most ligands is divalent cation dependent and conformationally sensitive. In addition to this common property, there is an underlying binding specificity between integrins and ligands for which there has been no structural basis. The recently reported crystal structures of the extracellular segment of an integrin in its unliganded state and in complex with a prototypical Arg-Gly-Asp (RGD) ligand have provided an atomic basis for cation-mediated binding of aspartic-acid-based ligands to integrins. They also serve as a basis for modelling other integrins in complex with larger physiologic ligands. These models provide new insights into the molecular basis for ligand binding specificity in integrins and its regulation by activation-driven tertiary and quaternary changes.     

Pharmacological comparison of rat and human melanocortin 3 and 4 receptors in vitro

The melanocortin 3 and 4 receptors are G-protein-coupled receptors found in the hypothalamus with important role in regulation of the energy balance. In this study, we performed pharmacological comparison of the rat and human melancortin (MC) 3 and MC4 receptors. We transiently expressed the genes for these receptors individually in a mammalian cell line and determined the binding affinities to several MSH peptides. The results showed no major difference between the rat and human MC3 receptors while the rat MC4 receptor had higher affinity to several peptides compared with the human MC4 receptor. NDP-, alpha-, beta-, gamma-MSH, ACTH(1-24), HS014 and MTII had from 5- to 34-fold higher affinity for the rat MC4 receptor, while SHU9119, HS024 and HS028 had similar affinity for both the MC4 receptors. Pharmacological species difference have earlier been reported for the MC1 and MC5 receptors but this is the first report showing important differences between the rat and human MC4 receptors.     

Lengthening the nose with a tongue-and-groove technique

Lengthening the short nose is often a major task. The ability to maintain proper alignment between the nasal base and dorsum may prove difficult without sacrificing the suppleness of the former. In this article, the authors introduce a technique of nose lengthening that ensures alignment of the tip with the rest of the nose yet avoids tip rigidity, unless a significant increase in tip projection is also planned. Two spreader grafts are placed, one on either side of the septum, and are extended beyond the caudal septal angle proportional to the planned nasal lengthening. A columella strut, with the cephalocaudal dimension equaling the combination of the width of the existing medial crura plus the amount of planned nasal lengthening, is placed between the medial crura in continuity with the caudal septum and is fixed to the medial crura using 5-0 clear nylon or polydioxanone suture. If additional projection beyond what is achievable by mere placement of a columella strut is required, the strut is fixed to the spreader grafts in a more projected position. Otherwise, the columella strut is simply positioned between the extensions of the spreader grafts. It is necessary to mobilize the lower lateral cartilages to prevent excessive columella show. This procedure has been performed on 23 patients over the past 12.5 years, with 20 patients enjoying good-to-excellent results. The advantages of this technique include its predictability and reproducibility, and the ability to elongate the nose with a mobile nasal base that is in line with the rest of the nose. If suture fixation is used to gain more projection, the technique proves dependable but the nose will become more rigid than is optimal. The requirement of three pieces of properly shaped septal cartilage, which might not be available when a secondary rhinoplasty is performed, is the major disadvantage of this operation. Furthermore, the procedure is, to some degree, labor-intensive.     

Syntheses and physical characterization of new aliphatic triblock poly(L-lactide-b-butylene succinate-b-L-lactide)s bearing soft and hard biodegradable building blocks

This study presents chemical syntheses and physical characterization of a new aliphatic poly(L-lactide-b-butylene succinate-b-L-lactide) triblock copolyester with soft and hard biodegradable building blocks. First, poly(butylene succinate) (PBS) prepolymers terminated with hydroxyl functional groups were synthesized through melt polycondensation from succinic acid and 1,4-butanediol. Further, a series of new PLLA-b-PBS-b-PLLA triblock copolyesters bearing various average PLLA block lengths were prepared via ring opening polymerization of L-lactide with the synthesized hydroxyl capped PBS prepolymer (Mn = 4.9 KDa) and stannous octanoate as the macroinitiator and catalyst, respectively. By means of GPC, NMR, FTIR, DSC, TGA, and wide-angle X-ray diffractometer (WAXD), the macromolecular structures and physical properties were intensively studied for these synthesized PBS prepolymer and PLLA-b-PBS-b-PLLA triblock copolyesters. 13C NMR and GPC experimental results confirmed the formation of sequential block structures without any detectable transesterification under the present experimental conditions, and the molecular weights of triblock copolyesters could be readily regulated by adjusting the feeding molar ratio of L-lactide monomer to the PBS macroinitiator. DSC measurements showed all single glass transitions, and their glass transition temperatures were found to be between those of PLLA and PBS, depending on the lengths of PLLA blocks. It was noteworthy that the segmental flexibilities of the hard PLLA blocks were found to be remarkably enhanced by the more flexible PBS block partner, and the PBS and PLLA building blocks were well mixed in the amorphous regions. Results of TGA analyses indicated that thermal degradation and stabilities of the PLLA blocks strongly depended on the average PLLA block lengths of triblock copolyesters. In addition, FTIR and WAXD results showed the coexistence of the assembled PLLA and PBS crystal structures when the average PLLA block length became larger than 7.8. These results may be beneficial for this new biodegradable aliphatic triblock copolyester to be applied as a potential biomaterial.     

Adhesion of high and low virulence Flavobacterium psychrophilum strains to isolated gill arches of rainbow trout Oncorhynchus mykiss

The ability of Flavobacterium psychrophilum to adhere to the gill tissue of rainbow trout Oncorhynchus mykiss was evaluated. A gill perfusion model was adopted, offering a number of advantages compared to other in vitro as well as in vivo models. A comparison between the adhesion capacity of a high and low virulence F. psychrophilum strain was made. Experiments were additionally carried out to assess the influence of water quality (organic material, nitrite) and temperature on the adhesion process of the bacterial cells. The high virulence strain attached more readily to the gill tissue than did the low virulence strain. Moreover, the adherence of the high virulence strain of F. psychrophilum was influenced by a number of factors. These were immersion of the gill arches in water to which organic material or nitrite were added, and elevated temperature. The former 2 increased the adhesion ability, while the latter had a negative influence on the adherence process.