Search

On November 20, 2008, the Buzzard Coulee H4 chondrite fell to Earth outside of Lloydminster, Alberta, Canada. Eighteen fresh samples obtained by the National Meteorite Collection of Canada, ranging from 8.80 to 109.14 g, were investigated in this study. Physical properties of the samples were first obtained using a suite of nondestructive techniques. The bulk density (Archimedean bead method: 3.48 ± 0.04 g cm−3; 3-D laser imaging: 3.46 ± 0.03 g cm−3; micro-computed tomography: 3.44 ± 0.03 g cm−3), porosity (6.2 ± 0.1%), bulk magnetic susceptibility (log χ: 5.364 ± 0.056 × 10−9 m3 kg−1 at 825 Hz; 5.329 ± 0.052 × 10−9 m3 kg−1 at 19,000 Hz), and other derived magnetic properties (frequency dependence: 8.7 ± 6.2%; degree of anisotropy A%: 22.0 ± 2.0%; ellipsoid shape B%: −18.7 ± 8.7%) are typical of H chondrites. The coefficient of variation associated with the properties measured directly was low (0.10-1.15%), indicating that the samples are homogenous at the interfragment scale. The study then proceeded with detailed analyses at the intrafragment scale. Visual inspection of micro-computed tomographic images allowed the identification of an anomalous large clast with low metal content in a fragment. Another fragment exhibited macroscopic shock veins that warranted further examination. These fragments were cut and polished thin sections prepared for petrological analysis by optical and scanning electron microscopy. Based on mineralogical and textural similarities with several chondrules, the large clast was interpreted to be a macrochondrule. In a larger context, this study proposes a protocol for the systematic investigation of extraterrestrial material that can be exported to other new meteorite falls and finds, and specimens from sample return mission. [ABSTRACT FROM AUTHOR]

When artichoke tuber tissue was cultured in mineral salts, the induction of DNA synthesis and subsequent cell division was dependent upon the presence of auxin in the incubation medium. Evidence is provided that an obligatory set of metabolic events precedes auxin-induced DNA synthesis, and previous work has associated these with protein synthesis. As a consequence the auxin-induced changes in nuclear and cytoplasmic proteins have been investigated. Using 2D gel electrophoresis, qualitative alterations in nuclear non-histone proteins have been detected from the earliest treatment times with auxin. These changes were progressive, starting with four novel proteins after 3 h auxin treatment and ending with about forty when DNA synthesis commences some 18-21 h later. Qualitative alterations in phosphorylated nuclear proteins due to auxin treatment were only detectable when DNA synthesis commenced. In contrast, few qualitative alterations in cytoplasmic proteins were detectable, with the major change being in phosphorylated proteins at the onset of DNA synthesis. A possible model of auxin action is outlined which involves sequential and progressive changes in the synthesis of nuclear proteins and the control of gene expression eventually leading to DNA synthesis. [ABSTRACT FROM AUTHOR]