The role of pyridoxine as a countermeasure for in-flight loss of lean body mass

Ground based and in flight research has shown that humans, under conditions of microgravity, sustain a loss of lean body tissue (protein) and changes in several biological processes including, reductions in red blood cell mass, and neurotransmitters. The maintenance of muscle mass, the major component of lean body mass, is required to meet the needs of space station EVAs. Central to the biosynthesis of amino acids, the building blocks of protein, is pyridoxine (vitamin B-6). Muscle mass integrity requires the availability of vitamin B-6 for protein metabolism and neurotransmitter synthesis. Furthermore, the formation of red blood cells require pyridoxine as a cofactor in the biosynthesis of hemoglobin, a protein that carries oxygen to tissues. In its active form, pyridoxal-5'-phosphate (PLP), vitamin B-6 serves as a link between amino acid and carbohydrate metabolism through intermediates of glycolysis and the tricarboxylic acid cycle. In addition to its role in energy metabolism, PLP is involved in the biosynthesis of hemoglobin and neurotransmitter which are necessary for neurological functions. Alterations in pyridoxine metabolism may affect countermeasures designed to overcome some of these biochemical changes. The focus of this research is to determine the effects of microgravity on the metabolic utilization of vitamin B-6, integrating nutrition as an integral component of the countermeasure (exercise) to maintain lean body mass and muscle strength. The objectives are: 1) to determine whether microgravity effects the metabolic utilization of pyridoxine and 2) to quantitate changes in B-6 vitamer distribution in tissue and excreta relative to loss of lean body tissue. The rationale for this study encompasses the unique challenge to control biochemical mechanisms effected during space travel and the significance of pyridoxine to maintain and counter muscle integrity for EVA activities. This experiment will begin to elucidate the importance of biochemical interactions between micronutrients and the homeostasis condition of biological processes in the space environment. To address this research topic a simulated microgravity model has been developed. The experiment uses radioisotopically labelled pyridoxine administered as an oral dose to rats which are maintained by tail suspension to simulate a microgravity environment. At the termination of the study, liver, muscle, blood and urine are collected and analyzed by reverse phase high pressure liquid chromatography to determine the quantity and distribution of the B-6 vitamers in tissue and excreta relative to lean body tissue loss. Earlier studies, published by this investigator, have shown that differences in vitamer distribution among samples from experimental versus control subjects indicate changes in metabolic utilization and storage of vitamin B-6

Searching for variable stars in Galactic Open Clusters

A long-term project, aiming at systematic search for variable stars in Galactic Open Clusters, was started at the Geneva Observatory in 2002. We have been observing regularly a sample of twenty-seven Galactic Open Clusters in the U, B, V Geneva filters. The goal is to identify and to study their variable stars, as well as the connection between the variable stars in a cluster and the cluster properties. We present the status of this work in progress, and show preliminary results for one of these clusters, IC 4651.Comment: To appear in the proceedings of Stellar Pulsation: Challenges for theory and observations Conference, Santa Fe, NM, US

Variability morphologies in the color-magnitude diagram. Searching for secular variability

This work is part of an effort to detect secular variable objects in large scale surveys by analysing their path in color-magnitude diagrams. To this aim, we first present the variability morphologies in the V/V-I diagram of several types of variable stars. They comprise both periodic and non periodic variable stars from the Large Magellanic Cloud, such as classical Cepheids, long period variables or Be and R Coronae Borealis stars, as well as two of the detected secular variable stars in the Galaxy, FG Sge and V4334 Sgr. The study of the different variability morphologies allows the identification of regions in the color-magnitude diagram where those secular variable stars could be detected. We also estimate the number of such secular variable stars expected in the Large Magellanic Cloud.Comment: To appear in the proceedings of the conference on Stellar Pulsation: Challenges for theory and observations, Santa Fe, NM, 31 may-5 june 200

Dissociation in a polymerization model of homochirality

A fully self-contained model of homochirality is presented that contains the effects of both polymerization and dissociation. The dissociation fragments are assumed to replenish the substrate from which new monomers can grow and undergo new polymerization. The mean length of isotactic polymers is found to grow slowly with the normalized total number of corresponding building blocks. Alternatively, if one assumes that the dissociation fragments themselves can polymerize further, then this corresponds to a strong source of short polymers, and an unrealistically short average length of only 3. By contrast, without dissociation, isotactic polymers becomes infinitely long.Comment: 16 pages, 6 figures, submitted to Orig. Life Evol. Biosp

Urban American Indian Community Health Beliefs Associated with Addressing Cancer in the Northern Plains Region

American Indians residing in the Northern Plains region of the Indian Health Service experience some of the most severe cancer-related health disparities. We investigated ways in which the community climate among an American Indian population in an urban community in the Northern Plains region influences community readiness to address cancer. A Community Readiness Assessment, following the Community Readiness Model, conducted semi-structured interviews with eight educators, eight students, and eight community leaders from the American Indian community in Omaha’s urban American Indian population and established the Northern Plains region community at a low level of readiness to address cancer. This study reports on a subsequent qualitative study that analyzed all 24 interview transcriptions for emergent themes to help understand the prevailing attitude of the community toward cancer. A synthesis of six emergent themes revealed that the community’s perceptions of high levels of severity and barriers, paired with perceptions of low levels of susceptibility and benefits, lead to low levels of self-efficacy, all of which are reflected in minimal cues to action and little effort to address cancer. These findings, interpreted through the lens of the Health Belief Model, can inform the development of more community-based, comprehensive, and culturally appropriate approaches to address the multilevel determinants of health behaviors in relation to cancer among American Indians in the Northern Plains region

Prospectus, August 27, 1990

https://spark.parkland.edu/prospectus_1990/1018/thumbnail.jp

The origin of life: chemical evolution of a metabolic system in a mineral honeycomb?

For the RNA-world hypothesis to be ecologically feasible, selection mechanisms acting on replicator communities need to be invoked and the corresponding scenarios of molecular evolution specified. Complementing our previous models of chemical evolution on mineral surfaces, in which selection was the consequence of the limited mobility of macromolecules attached to the surface, here we offer an alternative realization of prebiotic group-level selection: the physical encapsulation of local replicator communities into the pores of the mineral substrate. Based on cellular automaton simulations we argue that the effect of group selection in a mineral honeycomb could have been efficient enough to keep prebiotic ribozymes of different specificities and replication rates coexistent, and their metabolic cooperation protected from extensive molecular parasitism. We suggest that mutants of the mild parasites persistent in the metabolic system can acquire useful functions such as replicase activity or the production of membrane components, thus opening the way for the evolution of the first autonomous protocells on Earth

Origin of Life

The evolution of life has been a big enigma despite rapid advancements in the fields of biochemistry, astrobiology, and astrophysics in recent years. The answer to this puzzle has been as mind-boggling as the riddle relating to evolution of Universe itself. Despite the fact that panspermia has gained considerable support as a viable explanation for origin of life on the Earth and elsewhere in the Universe, the issue remains far from a tangible solution. This paper examines the various prevailing hypotheses regarding origin of life like abiogenesis, RNA World, Iron-sulphur World, and panspermia; and concludes that delivery of life-bearing organic molecules by the comets in the early epoch of the Earth alone possibly was not responsible for kick-starting the process of evolution of life on our planet.Comment: 32 pages, 8 figures,invited review article, minor additio

Midlands Cadences: Narrative Voices in the Work of Alan Sillitoe

This paper will examine excerpts from a range of Alan Sillitoe’s prose fiction, most notably Saturday Night and Sunday Morning (1958) and short stories from the collection The Loneliness of the Long-Distance Runner (1958), via a comparative exploration of the texts’ representations of Midlands English demotic. Both texts enact Bakhtin’s notion of novelistic dialogism and find much expressive capital in the tension between discourses: between the oral and the written. Indeed, it could be argued that much of Sillitoe’s work functions as a direct challenge to dominant notions of the literary. The narrative discourse attempts to trace a link between the quotidian experience of the Midlands English working classes represented and the demotic language which they speak. His technique also explores the link between language and sensibility; i.e. verbal articulacy need not be a limit to expression of a character’s distinctive identity. In contrast to the more radical techniques of novelists like James Kelman and Irvine Welsh, all instances of phonetically-rendered demotic remain imprisoned by what Joyce called ‘perverted commas’ – as direct speech. However, the diegetic narrative discourse itself is redolent of registers rooted in 1950s English working class life. The texts also contain different methods of representing their protagonists’ consciousness through their own idiolect. In Saturday Night and Sunday Morning, this is evidenced by the use of the second person ‘you’. It functions simultaneously as a representation of Seaton’s consciousness in the oral register which he might choose to articulate it, and as a dialogic ‘sideways glance’ at the reader and assumed shared experience. The second is more redolent of internal monologue, using the first-person form (as seen in the homodiegetic narration of the second novel); crucially, though, it remains in Standard English, if explicitly orientated towards oral register. Sillitoe’s is a novelistic discourse which refuses to normalise itself to accord with the conventions of classic realism, and as such prefigures the ambitions of many contemporary writers who incline their narrative voices towards the oral – asserting the right of a character’s dialect/idiolect to be the principal register of the narrative. The paper will demonstrate this thesis through the ideas of Bakhtin, and through an analytical taxonomy derived from literary stylistics. It aims to propose a model which can be used to analyse and explore any fiction which has been labelled as ‘working class’, and asserts that such an approach leads to a more principled characterisation of working class fiction (based on its use of language) than current literary-critical discussions based simply on cultural/social context and biography

Describing semigroups with defining relations of the form xy=yz xy and yx=zy and connections with knot theory

We introduce a knot semigroup as a cancellative semigroup whose defining relations are produced from crossings on a knot diagram in a way similar to the Wirtinger presentation of the knot group; to be more precise, a knot semigroup as we define it is closely related to such tools of knot theory as the twofold branched cyclic cover space of a knot and the involutory quandle of a knot. We describe knot semigroups of several standard classes of knot diagrams, including torus knots and torus links T(2, n) and twist knots. The description includes a solution of the word problem. To produce this description, we introduce alternating sum semigroups as certain naturally defined factor semigroups of free semigroups over cyclic groups. We formulate several conjectures for future research