Identification and activation of mitogen-activated protein (MAP) kinase in normal human osteoblastic and bone marrow stromal cells: Attenuation of MAP kinase activation by cAMP,parathyroid hormone and forskolin

The mitogen-activated protein (MAP) kinases (p44^mapk and p42^mapk), also known as extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2), are activated in response to a variety of extracellular signals, including growth factors, hormones and, neurotransmitters. We have investigated MAP kinase signal transduction pathways in normal human osteoblastic cells. Normal human bone marrow stromal (HBMS), osteoblastic (HOB), and human (TE85, MG-63, SaOS-2), rat (ROS 17/2.8, UMR-106) and mouse (MC3T3-E1) osteoblastic cell lines contained immunodetectable p44^mapk/ERK1 and p42^mapk/ERK2. MAP kinase activity was measured by 'in-gel' assay myelin basic protein as the substrate. Mainly ERK2 was rapidly activated (within 10 min) by bFGF, IGF-I and PDGF-BB in normal HOB, HBMS and human osteosarcoma cells, whereas both ERK1 and ERK2 were activated by growth factors in rat osteoblast-like cell lines, ROS 17/2.8 and UMR-106. The ERK1 activation was greater than the ERK2 in ROS 17/2.8 cells. Furthermore, ERK2 was also activated by bFGF and PDGF-BB in the mouse osteoblastic cell line, MC3T3-E1. This is the first demonstration of inter-species differences in the activation of MAP kinases in osteoblastic cells. Cyclic AMP derivatives or cAMP generating agents such as PTH and forskolin inhibited ERK2 activation by bFGF and PDGF-BB suggesting a 'cross-talk' between the two different signalling pathways activated by receptor tyrosine kinases and cAMP-dependent protein kinase. The accumulated results also suggest that the MAP kinases may be involved in mediating mitogenic and other biological actions of bFGF, IGF-I and PDGF-BB in normal human osteoblastic and bone marrow stromal cells.     

Use of Polyelectrolytes and Electron Microscopy for Detection of Viruses from Stool

Insoluble polyelectrolytes (PE60) were used for the concentration of viruses from stool specimens, confirming the results of Wallis et al. (1969). Ten percent suspensions inoculated with poliovirus type 3 were used in these experiments. A small number of stool specimens from patients naturally infected with enteroviruses were also tested. Preferential adsorption of viruses to PE60 was maximum at a pH range of 4.5 to 6.0. The elution of the adsorbed viruses was optimal at pH 8.5. Other parameters were also investigated. Electron microscopy was used successfully to detect the eluted viruses.     

Design issues for a high-performance distributed shared memory on symmetrical multiprocessor clusters

Clusters of Symmetrical Multiprocessors (SMPs) have recently become the norm for high-performance economical computing solutions. Multiple nodes in a cluster can be used for parallel programming using a message passing library. An alternate approach is to use a software Distributed Shared Memory (DSM) to provide a view of shared memory to the application programmer. This paper describes Strings, a high performance distributed shared memory system designed for such SMP clusters. The distinguishing feature of this system is the use of a fully multi-threaded runtime system, using kernel level threads. Strings allows multiple application threads to be run on each node in a cluster. Since most modern UNIX systems can multiplex these threads on kernel level light weight processes, applications written using Strings can exploit multiple processors on a SMP machine. This paper describes some of the architectural details of the system and illustrates the performance improvements with benchmark programs from the SPLASH-2 suite, some computational kernels as well as a full fledged application. It is found that using multiple processes on SMP nodes provides good speedups only for a few of the programs. Multiple application threads can improve the performance in some cases, but other programs show a slowdown. If kernel threads are used additionally, the overall performance improves significantly in all programs tested. Other design decisions also have a beneficial impact, though to a lesser degree. This revised version was published online in July 2006 with corrections to the Cover Date.     

Deciphering the mechanism behind the varied binding activities of COXIBs through Molecular Dynamic Simulations,MM-PBSA binding energy calculations and per-residue energy decomposition studies

COX-2 is a well-known drug target in inflammatory disorders. COX-1/COX-2 selectivity of NSAIDs is crucial in assessing the gastrointestinal side effects associated with COX-1 inhibition. Celecoxib, rofecoxib, and valdecoxib are well-known specific COX-2 inhibiting drugs. Recently, polmacoxib, a COX-2/CA-II dual inhibitor has been approved by the Korean FDA. These COXIBs have similar structure with diverse activity range. Present study focuses on unraveling the mechanism behind the 10-fold difference in the activities of these sulfonamide-containing COXIBs. In order to obtain insights into their binding with COX-2 at molecular level, molecular dynamics simulations studies, and MM-PBSA approaches were employed. Further, per-residue decomposition of these energies led to the identification of crucial amino acids and interactions contributing to the differential binding of COXIBs. The results clearly indicated that Leu338, Ser339, Arg499, Ile503, Phe504, Val509, and Ser516 (Leu352, Ser353, Arg513, Ile517, Phe518, Val523, and Ser530 in PGHS-1 numbering) were imperative in determining the activity of these COXIBs. The binding energies and energy contribution of various residues were similar in all the three simulations. The results suggest that hydrogen bond interaction between the hydroxyl group of Ser516 and five-membered ring of diarylheterocycles augments the affinity in COXIBs. The SAR of the inhibitors studied and the per-residue energy decomposition values suggested the importance of Ser516. Additionally, the positive binding energy obtained with Arg106 explains the binding of COXIBs in hydrophobic channel deep in the COX-2 active site. The findings of the present work would aid in the development of potent COX-2 inhibitors.     

Strategic mate‐guarding behaviour in ladybirds

Mate‐guarding behaviour is regarded as a means of increasing paternity share by reducing sperm competition. It is known to be a plastic response which varies with operational sex ratios and competitor presence in the vicinity. In a recent study, prolonged mating duration in Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae) has been found to incorporate mate‐guarding behaviour. The present investigation was conducted to assess its plasticity in the presence of competitors. The physical and chemical presence of competitors of both sexes at varying densities was provided to a pair of ladybirds, and their time to commence mating, latent period and mate‐guarding duration was observed. These were compared to a control treatment where other partners were absent. All treatments were conducted with sibling as well as non‐sibling competitors. It was our hypothesis that mate guarding would be increased in the presence of male competitors and would be reduced by female presence. The results revealed that while mate‐guarding duration was increased by the chemical presence of males it was decreased by their physical presence. The latter result was attributed to interference by other males who dislodge the mating male in order to access the female. Female chemical presence had no effect on mate guarding, while physical presence increased the duration of mate guarding. The reasons for the latter behaviour require further investigation. Responses were not significantly affected by the relationship between the focal pair and the competitor. The authenticity of the mate guarding in this ladybird is strongly affirmed by our results.     

Near Ambient Condition Hydrogen Storage in a Synergized Tricomponent Hydride System

Reversible hydrogen storage over hydrides of light elements (HLEs) under ambient condition has been pursued actively for nearly two decades. However, because of unfavorable thermodynamics and/or severe kinetic barrier of HLEs, limited progress has been made. Here, it is demonstrated that the interaction of LiBH₄ with Mg(NH₂)₂ and LiH, three of the most investigated HLEs, can lead to a fully reversible dehydrogenation/rehydrogenation cycle at temperatures below 373 K. More importantly, with the desorption enthalpy of 24 kJ (mol H₂)^?1 the dehydrogenation process at 1.0 bar H₂ is theoretically possible to be as low as 266 K. Characterization of this combination of HLEs shows that LiBH₄ serves as a reagent complexing with intermediates and products of the dehydrogenation of Mg(NH₂)₂‐LiH, and significantly alters the overall thermodynamic and kinetic properties of the system.