The human leulocyte test system. VII. Further investigations concerning micronucleus-derived premature chromosome condensation.

Premature chromosome condensation (PCC) from X-ray induced micronuclei shows a dose-effect relationship in human leukocytes in vitro. Preparations at different culture times without colcemide treatment reveal complex variations of the frequencies of micronuclei and PCC correlated with the fixation time. The positions of PCC patches in the metaphase plate and the frequencies of different PCC types (S and G2) ar independent on the X-ray dose. The latter indicates that the slowing down of the micronuclei in the cell cycle, which is the reason for the formation of PCC, may be an outcome rather of a regulatory phenomenon than of an unspecific physiological damage of the chromatin included in the micronuclei. This is especially evident from labeling experiments with tritiated thymidine, showing that the extent of asynchrony between main nuclei and micronuclei is independent on the X-ray dose. Labeling experiments with tritiated uridine reveal a X-ray dose dependent suppression of RNA synthesis in cells with main nuclei and micronuclei. THE S-phase nature of "pulverized" PCC patches could be verified by incorporation of tritiated thymidine in aound 50%. Staining of centromeric heterochromatin in micronuclei reveal a frequency of micronuclei with centromeric heterochromatin resembling the frequency of G2-phase PCC found in mitoses.     

Further investigations of the algae of pond margins

Summary There appears to be an association between the relative humidity of the atmosphere and the vertical distribution of certain diatoms in the uppermost few millimeters of leaf litter at pond margins. Cells tend to accumulate at the surface when the relative humidity exceeds 70% and below the surface at lower relative humidities.There are indications also that the vertical distribution of flagellates might be associated with relative humidity.Diatoms and other algae have been grown on a variety of media, particularly damp, sterile mud. Culture experiments indicate that the critical moisture content, below which cells of two diatoms, Pinnularia biceps f. minutissima and Navicula cryptocephala, tend to lose their viability, is in the region of 50% (of the wet weight).For these two species of diatoms, it would appear that cells which accumulate fat are more likely to survive drying than those which do not. The protoplast of certain cells of these two diatoms appeared to develop a fatty peripheral layer during drying. Pinnularia biceps f. minutissima remained viable after a further year of drying.     

Further investigations into hormone-directed transport in stems

Summary The effect of IAA and three synthetic auxins on the upward movement of ³²P-orthophosphate and ¹⁴C-sucrose has been investigated in decapitated stems of Phaseolus vulgaris L., Pisum sativum L., Coleus blumci L. and Helianthus annuus L. IAA greatly enhanced the accumulation of ³²P-orthophosphate in Phaseolus vulgaris and Pisum sativum, whereas in C. blumei and H. annuus it did not. 2,4-D like IAA, caused an increase in ¹⁴C-sucrose and ³²P-orthophosphate accumulation in Phaseolus vulgaris but, unlike IAA, caused no increase in Pisum sativum. The downward transport of ¹⁴C-IAA, ¹⁴C-NAA, ¹⁴C-2,4-D and ¹⁴C-2,4,5-T from the decapitated apex was also studied. Results are discussed in terms of current theories of hormone-directed transport.For abbreviations see Table 1.     

Design and analysis of quantitative differential proteomics investigations using LC-MS technology

Liquid chromatography-mass spectrometry (LC-MS)-based proteomics is becoming an increasingly important tool in characterizing the abundance of proteins in biological samples of various types and across conditions. Effects of disease or drug treatments on protein abundance are of particular interest for the characterization of biological processes and the identification of biomarkers. Although state-of-the-art instrumentation is available to make high-quality measurements and commercially available software is available to process the data, the complexity of the technology and data presents challenges for bioinformaticians and statisticians. Here, we describe a pipeline for the analysis of quantitative LC-MS data. Key components of this pipeline include experimental design (sample pooling, blocking, and randomization) as well as deconvolution and alignment of mass chromatograms to generate a matrix of molecular abundance profiles. An important challenge in LC-MS-based quantitation is to be able to accurately identify and assign abundance measurements to members of protein families. To address this issue, we implement a novel statistical method for inferring the relative abundance of related members of protein families from tryptic peptide intensities. This pipeline has been used to analyze quantitative LC-MS data from multiple biomarker discovery projects. We illustrate our pipeline here with examples from two of these studies, and show that the pipeline constitutes a complete workable framework for LC-MS-based differential quantitation. Supplementary material is available at http://iec01.mie.utoronto.ca/~thodoros/Bukhman/.     

Quantitative autoradiographic analysis of muscarinic receptors and quantitative histochemistry of acetylcholinesterase in the rat brain after trimethyltin intoxication

The influence of trimethyl tin (TMT) intoxication on muscarinic cholinergic receptors and histochemistry of acetylcholinesterase (AChE) in the rat brain 21 days after treatment was studied. The topographical distribution and reduction in muscarinic receptor sites were analysed by means of quantitative receptor autoradiography using [³H]quinuclidinyl benzilate (QNB). TMT treatment produced a decrease in cholinergic receptors in a large number of brain regions.

The quantitative distribution of AChE was examined in over 60 regions following TMT intoxication. The activity of AChE was significantly affected. Reduced AChE content was found in several brain regions following TMT intoxication. The effect on AChE content was confined to cholinergic terminal areas, e.g. the hippocampus, while in the area dentata a significant increase in AChE content was detected.

The results are interpreted in terms of TMT producing disruption of the cholinergic system with implications for a neuroanatomical basis of impaired memory mechanisms.