Shedding of peripheral cytoplasm - a mechanism of liver cell atrophy in human amyloidosis.

A liver biopsy specimen from a case of primary amyloidosis was investigated by electron microscopy. The cytoplasmic periphery of the hepatocytes showed degenerativechanges which are interpreted as indicating shedding of peripheral parts of the cytoplasm. Two main variants of this process could be discerned: 1) Protrusion and sequestration of hernia-like blebs of cytoplasm, and 2) shedding of vesicles derived from degenerated endoplasmic reticulum. In the latter case transient defects of the plasma membrane seem to be relevance. Endoplasmic reticulum and cytoplasmic ground substance appeared to be shed preferentially, whereas mitochondria are retained within the cell. As a consequence the fractional volume of the mitochondria in the cytoplasm of atrophic cells is markedly increased. Shedding of peripheral cytoplasm, therefore, seems to be an effective mechanism enabeling the cell to adapt the mass and the composition of its cytoplasm to an unfavourable environment.     

Statistical learning of peptide retention behavior in chromatographic separations: a new kernel-based approach for computational proteomics

Background  

High-throughput peptide and protein identification technologies have benefited tremendously from strategies based on tandem mass spectrometry (MS/MS) in combination with database searching algorithms. A major problem with existing methods lies within the significant number of false positive and false negative annotations. So far, standard algorithms for protein identification do not use the information gained from separation processes usually involved in peptide analysis, such as retention time information, which are readily available from chromatographic separation of the sample. Identification can thus be improved by comparing measured retention times to predicted retention times. Current prediction models are derived from a set of measured test analytes but they usually require large amounts of training data.     

Comparison between filament lamps and compact fluorescent lamps

“Produktlinienanalyse” (PLA) and life cycle assessment are analytical approaches which are used as instruments to survey the life cycle of a product, but whose main purpose can be viewed as being the optimization of this life cycle. The lesser known instrument of PLA includes an appraisal of product utility, and assesses the life cycle not only according to environmental, but also according to economic and social impacts. Moreover, PLA involves the agents relevance to the life cycle. This case study, a comparison between filament lamps and compact fluorescent lamps, shows that the purely environmental perspective is insufficient and omits a series of relevant criteria. It illustrates that additional social and economic parameters, and the examination of the utility of a product, have a great impact upon this comparison. The method of product system improvement with agent cooperation is put forward as a technique for the transposition of the results into concrete action. This study was financed from own funds of the Öko-Institut e.V., Freiburg.     

Inhibition of cellular autophagy in kidney tubular cells stimulated to grow by unilateral nephrectomy

Cytoplasmic growth (hypertrophy) presupposes a positive metabolic balance brought about by increased anabolic and/or decreased catabolic processes. Degradation of cytoplasmic components takes place in autophagic vacuoles (AVs) whose volume fraction may be taken as a measure of the relative rate of degradation of cytoplasmic components. Male adult Sprague-Dawley rats (n = 80) were unilaterally nephrectomized (n = 40) or sham-operated (n = 40) and were killed 3.5-57.5 h p.o. The volume density of AVs in parenchymal cells of renal cortical convoluted tubules was determined morphometrically by systematic evaluation of large test fields in the electron microscope. During compensatory renal growth, the volume densities of autophagic vacuoles were reduced at day 0 (3.5-8 h p.o.), day 1 (20.5-33.5 h p.o.) and day 2 (44.5-57.5 h p.o.) by 49% (p less than 0.01), 43% (p less than 0.05), and 19% (n.s.), respectively, when compared with sham-operated controls. No decrease, and even an increase, in the AV-volume fraction was found in liver parenchymal cells of the unilaterally nephrectomized animals. This indicates that inhibition of autophagy is not a general response after unilateral nephrectomy, but is confined to the growing kidney, where it may represent a significant factor in the increase of cytoplasmic mass.     

Structure of mouse DNA (cytosine-5-)-methyltransferase

DNA (cytosine-5-)-methyltransferase was purified as a single polypeptide (190 kDa by SDS-PAGE) from mouse P815 mastocytoma cells. This enzyme transfers methyl groups to unmethylated as well as to hemimethylated DNA sites with a strong preference for the hemimethylated substrate. A structural analysis of the isolated enzyme by electron microscopical techniques was undertaken. On the basis of the results obtained, we propose a model for the enzyme structure. This model describes the enzyme as a hemi-elliptical globular structure with dimensions of 5.4-6.7 nm for the height h and 10.3-10.8 nm for the diameter d, respectively; this globular structure bears a small appendix at the flat side. A molecular mass of 235-250 kDa is calculated from the measured dimensions. Limited trypsin digestion of the enzyme led to a 160-kDa fragment which preserved the gross morphology of the original material. The possible structure function relationships are discussed.