GEMS: Gossip-Enabled Monitoring Service for Scalable Heterogeneous Distributed Systems

Gossip protocols have proven to be effective means by which failures can be detected in large, distributed systems in an asynchronous manner without the limitations associated with reliable multicasting for group communications. In this paper, we discuss the development and features of a Gossip-Enabled Monitoring Service (GEMS), a highly responsive and scalable resource monitoring service, to monitor health and performance information in heterogeneous distributed systems. GEMS has many novel and essential features such as detection of network partitions and dynamic insertion of new nodes into the service. Easily extensible, GEMS also incorporates facilities for distributing arbitrary system and application-specific data. We present experiments and analytical projections demonstrating scalability, fast response times and low resource utilization requirements, making GEMS a potent solution for resource monitoring in distributed computing.     

Differentiation-promoting effect of 1-O (2 methoxy) hexadecyl glycerol in human colon cancer cells

Alkylglycerols are naturally occurring bioactive ether lipids found in great abundance in the livers of many marine species. In this study, we evaluated the differentiation-promoting potential of a methoxy substituted alkylglycerol--1-O (2 methoxy) hexadecyl glycerol (MHG)--to promote a more benign or differentiated phenotype in human colon cancer cells. Three cell lines with different biological and phenotypic properties were used. They were the moderately differentiated and growth factor-responsive Moser, the growth factor-unresponsive and malignant HT29, and the poorly differentiated and growth factor-unresponsive HCT116. Treatment of these cell lines with MHG resulted in a downmodulation of cellular proliferation, a reduced propensity for anchorage-independent growth, and a reduced capacity in cellular invasion. Induction of the colon-associated and differentiation-related molecule carcinoembryonic antigen was also observed in the three cell lines. Induction of the transformation-sensitive and differentiation-related glycoprotein fibronectin was observed in the HT29 cells. It is concluded that MHG was biologically active and promoted a more benign or differentiated phenotype in these colon cancer cells. Since differentiation-inducing agents may possess chemoprevention properties, the use of MHG and the alkylglycerols in inducing differentiation or in chemoprevention of malignant diseases warrants further investigation.     

Quenching of excited states of chlorophyll molecules in submembrane fractions of Photosystem I by exogenous quinones

The ability of three substituted quinones, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), 2,6-dichloro-p-benzoquinone (DCBQ), and tetramethyl-p-benzoquinone (duriquinone) to quench the excited states of chlorophyll (Chl) molecules in Photosystem I (PSI) was studied. Chl fluorescence emission measured with isolated PSI submembrane fractions was reduced following the addition of exogenous quinones. This quenching progressively increased with rising concentrations of the exogenous quinones according to the Stern-Volmer law. The values of Stern-Volmer quenching coefficients were found to be 3.28 x 10(5) M(-1) (DBMIB), 1.31 x 10(4) M(-1) (DCBQ), and 3.7 x 10(3) M(-1) (duroquinone). The relative quenching capacities of the various exogenous quinones in PSI thus strictly coincided to those found for the quenching of Fo level of Chl fluorescence in isolated thylakoids, which is emitted largely by Photosystem II (PSII) [Biochim. Biophys. Acta (2003) 1604, 115-123]. Quenching of Chl excited states in PSI submembrane fractions by exogenous quinones slowed down the rate of P700, primary electron donor of PSI, photooxidation measured at limiting actinic light irradiances thus revealing a reduced photochemical capacity of absorbed quanta. The possible involvement of non-photochemical quenching of excited Chl states by oxidized phylloquinones, electron acceptors of PSI, and oxidized plastoquinones, mobile electron carriers between PSII and the cytochrome b(6)/f complex, into the control of photochemical activity of PSI is discussed.     

Light-induced trimer to monomer transition in the main light-harvesting antenna complex of plants: thermo-optic mechanism

The main chlorophyll a/b light-harvesting complex of photosystem II, LHCIIb, has earlier been shown to be capable of undergoing light-induced reversible structural changes and chlorophyll a fluorescence quenching in a way resembling those observed in granal thylakoids when exposed to excess light [Barzda, V., et al. (1996) Biochemistry 35, 8981-8985]. The nature and mechanism of this unexpected structural flexibility has not been elucidated. In this work, by using density gradient centrifugation and nondenaturing green gel electrophoresis, as well as absorbance and circular dichroic spectroscopy, we show that light induces a significant degree of monomerization, which is in contrast with the preferentially trimeric organization of the isolated complexes in the dark. Monomerization is accompanied by a reversible release of Mg ions, most likely from the outer loop of the complexes. These data, as well as the built-in thermal and light instability of the trimeric organization, are explained in terms of a simple theoretical model of thermo-optic mechanism, effect of fast thermal transients (local T-jumps) due to dissipated photon energies in the vicinity of the cation binding sites, which lead to thermally assisted elementary structural transitions. Disruption of trimers to monomers by excess light is not confined to isolated trimers and lamellar aggregates of LHCII but occurs in photosystem II-enriched grana membranes, intact thylakoid membranes, and whole plants. As indicated by differences in the quenching capability of trimers and monomers, the appearance of monomers could facilitate the nonphotochemical quenching of the singlet excited state of chlorophyll a. The light-induced formation of monomers may also be important in regulated proteolytic degradation of the complexes. Structural changes driven by thermo-optic mechanisms may therefore provide plants with a novel mechanism for regulation of light harvesting in excess light.     

The embryonic development and the thermal effects on the development of the mountain whitefish, Prosopium williamsoni (Girard)

The general development of the mountain whitefish was similar to other whitefishes. Mountain whitefish required more thermal units to reach corresponding stages of the lake whitefish, after the stage when the blastodisc was prominently raised on the yolk. The development process was greatly disrupted and a heavy mortality of eggs occurred when the temperature was raised to 9° C or higher. In hatched larvae abnormalities like monomicrophthalmia, agape jaws, and coloboma occurred when the temperature was raised to 9° C or higher, although the reported optimum temperature for growth of the post yolk sac larvae and juveniles was 9° C-12° C. The late spawned eggs exhibit adaptive mechanisms which enabled them to shorten the incubation time and hatch along with the early spawned eggs, when conditions for survival are at optimum.     

Paradoxes of Hymenoptera flight muscles,extreme machines

In the Carboniferous, insects evolved flight. Intense selection drove for high performance and approximately 100 million years later, Hymenoptera (bees, wasps and ants) emerged. Some species had proportionately small wings, with apparently impossible aerodynamic challenges including a need for high frequency flight muscles (FMs), powered exclusively off aerobic pathways and resulting in extreme aerobic capacities. Modern insect FMs are the most refined and form large dense blocks that occupy 90% of the thorax. These can beat wings at 200 to 230 Hz, more than double that achieved by standard neuromuscular systems. To do so, rapid repolarisation was circumvented through evolution of asynchronous stimulation, stretch activation, elastic recoil and a paradoxically slow Ca²⁺ reuptake. While the latter conserves ATP, considerable ATP is demanded at the myofibrils. FMs have diminished sarcoplasmic volumes, and ATP is produced solely by mitochondria, which pack myocytes to maximal limits and have very dense cristae. Gaseous oxygen is supplied directly to mitochondria. While FMs appear to be optimised for function, several unusual paradoxes remain. FMs lack any significant equivalent to the creatine kinase shuttle, and myofibrils are twice as wide as those of within cardiomyocytes. The mitochondrial electron transport systems also release large amounts of reactive oxygen species (ROS) and respiratory complexes do not appear to be present at any exceptional level. Given that the loss of the creatine kinase shuttle and elevated ROS impairs heart function, we question how do FM shuttle adenylates at high rates and tolerate oxidative stress conditions that occur in diseased hearts?