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Direct Study (direct + study)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Documentary Evidence of an Economic Character as a Source for the Study of Meteorological and Hydrological Extremes and their Impacts on Human Activities

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2006
Rudolf Brázdil
Abstract This paper deals with documentary evidence of an economic character as a proxy for direct study of meteorological and hydrological extremes. Taxation records and reports of those who administrated domains and estates are described with respect to information about meteorological and hydrological extremes. Based on data from eight domains or estates from Moravia (in the Czech Republic), frequency series of floods and convective storms (including hailstorms) were developed for the period 1650,1849. One example of disastrous weather, which took place on 10 August 1694 in the Pern,tejn domain, is used to demonstrate the potential for such studies of the intensity of extremes and their impact on human activities. The importance of economic evidence in the instrumental period is shown through tax rebate data contingent upon hailstorm damage in Moravia (1896,1906). The benefits of employing documentary economic evidence for historical climatology and the study of the impact of meteorological and hydrological extremes on human activities are discussed. [source]

Statistical analysis of amplified fragment length polymorphism data: a toolbox for molecular ecologists and evolutionists

MOLECULAR ECOLOGY, Issue 18 2007
A. Bonin
Abstract Recently, the amplified fragment length polymorphism (AFLP) technique has gained a lot of popularity, and is now frequently applied to a wide variety of organisms. Technical specificities of the AFLP procedure have been well documented over the years, but there is on the contrary little or scattered information about the statistical analysis of AFLPs. In this review, we describe the various methods available to handle AFLP data, focusing on four research topics at the population or individual level of analysis: (i) assessment of genetic diversity; (ii) identification of population structure; (iii) identification of hybrid individuals; and (iv) detection of markers associated with phenotypes. Two kinds of analysis methods can be distinguished, depending on whether they are based on the direct study of band presences or absences in AFLP profiles (,band-based' methods), or on allelic frequencies estimated at each locus from these profiles (,allele frequency-based' methods). We investigate the characteristics and limitations of these statistical tools; finally, we appeal for a wider adoption of methodologies borrowed from other research fields, like for example those especially designed to deal with binary data. [source]

Large-scale extraction and characterization of CD271+ multipotential stromal cells from trabecular bone in health and osteoarthritis: Implications for bone regeneration strategies based on uncultured or minimally cultured multipotential stromal cells,

ARTHRITIS & RHEUMATISM, Issue 7 2010
E. Jones
Objective To test the hypothesis that CD45lowCD271+ bone marrow multipotential stromal cells (MSCs) are abundant in the trabecular bone niche and to explore their functional "fitness" in health and osteoarthritis (OA). Methods Following enzymatic extraction, MSC release was evaluated using colony-forming unit,fibroblast (CFU-F) and colony-forming unit,osteoblast assays, flow cytometry, and confocal microscopy. CD45lowCD271+ cells isolated by fluorescence-activated cell sorting were enumerated and expanded under standard and clonal conditions. Their proliferative and osteogenic potencies were assessed in relation to donor age and compared with those of aspirated CD45lowCD271+ cells. In vitro and in vivo MSC "aging" was measured using quantitative polymerase chain reaction,based telomere length analysis, and standard differentiation assays were utilized to demonstrate multipotentiality. Results Cellular isolates from trabecular bone cavities contained ,65-fold more CD45lowCD271+ cells compared with aspirates (P < 0.0001) (median 1.89% [n = 39] and 0.029% [n = 46], respectively), concordant with increased CFU-F release. Aspirated and enzymatically released CD45lowCD271+ cells had identical MSC phenotypes (,100% CD73+CD105+CD13+, ,50,60% CD146+CD106+CD166+) and contained large proportions of highly clonogenic multipotential cells. In vitro osteogenic potency of freshly isolated CD45lowCD271+ cells was comparable with, and often above, that of early-passage MSCs (8,14%). Their frequency and in vivo telomere status in OA bone were similar to those in bone from age-matched controls. Conclusion Our findings show that CD45lowCD271+ MSCs are abundant in the trabecular bone cavity and indistinguishable from aspirated CD45lowCD271+ MSCs. In OA they display aging-related loss of proliferation but no gross osteogenic abnormality. These findings offer new opportunities for direct study of MSCs in musculoskeletal diseases without the requirement for culture expansion. They are also relevant for direct therapeutic exploitation of prospectively isolated, minimally cultured MSCs in trauma and OA. [source]

Calcium sensing and cell signaling processes in the local regulation of osteoclastic bone resorption

BIOLOGICAL REVIEWS, Issue 1 2004
Mone Zaidi
ABSTRACT The skeletal matrix in terrestrial vertebrates undergoes continual cycles of removal and replacement in the processes of bone growth, repair and remodeling. The osteoclast is uniquely important in bone resorption and thus is implicated in the pathogenesis of clinically important bone and joint diseases. Activated osteoclasts form a resorptive hemivacuole with the bone surface into which they release both acid and osteoclastic lysosomal hydrolases. This article reviews cell physiological studies of the local mechanisms that regulate the resorptive process. These used in vitro methods for the isolation, culture and direct study of the properties of neonatal rat osteoclasts. They demonstrated that both local microvascular agents and products of the bone resorptive process such as ambient Ca2+ could complement longer-range systemic regulatory mechanisms such as those that might be exerted through calcitonin (CT). Thus elevated extracellular [Ca2+], or applications of surrogate divalent cation agonists for Ca2+, inhibited bone resorptive activity and produced parallel increases in cytosolic [Ca2+], cell retraction and longer-term inhibition of enzyme release in isolated rat osteoclasts. These changes showed specificity, inactivation, and voltage-dependent properties that implicated a cell surface Ca2+ receptor (CaR) sensitive to millimolar extracellular [Ca2+]. Pharmacological, biophysical and immunochemical evidence implicated a ryanodine-receptor (RyR) type II isoform in this process and localized it to a unique, surface membrane site, with an outward-facing channel-forming domain. Such a surface RyR might function either directly or indirectly in the process of extracellular [Ca2+] sensing and in turn be modulated by cyclic adenosine diphosphate ribose (cADPr) produced by the ADP-ribosyl cyclase, CD38. The review finishes by speculating about possible detailed models for these transduction events and their possible interactions with other systemic mechanisms involved in Ca2+ homeostasis as well as the possible role of the RyR-based signaling mechanisms in longer-term cell regulatory processes. [source]