Compartment modeling from tracer experiments

Anelementary system is defined as two compartments, one the immediate and unique precursor of the other. By synthesizing a number of elementary systems, we can obtain a system with any givenweight, transfer time anddispersion. A criterion is presented to choose the best model of a given system, i.e. a system with the same above parameters and composed of a minimum number of elementary systems. Supported in part by NIH grant NO. GM-572. Supported by PHS Training grant No. 2T01 HE05138-17 from the National Heart Institute.     

Inactivation of Influenza A Virus on Copper versus Stainless Steel Surfaces

Influenza A virus particles (2 × 10⁶) were inoculated onto copper or stainless steel and incubated at 22°C at 50 to 60% relative humidity. Infectivity of survivors was determined by utilizing a defined monolayer with fluorescent microscopy analysis. After incubation for 24 h on stainless steel, 500,000 virus particles were still infectious. After incubation for 6 h on copper, only 500 particles were active.     

Characterization of ochratoxin A-induced apoptosis in primary rat hepatocytes

The main target organ of the mycotoxin ochratoxin A (OTA) in mammals is the kidney but OTA has also been shown to be hepatotoxic in rats and to induce tumors in mouse liver. Even at very low concentrations, OTA causes perturbations of cellular signaling pathways as well as enhanced apoptosis. OTA has been extensively studied in kidney cell systems. Since this substance also affects liver health, we focused our work on apoptosis-related events induced by OTA in primary rat hepatocytes. We performed pathway-specific polymerase chain reaction arrays to assess the expression of genes involved in apoptosis. Treatment with 1 μM OTA for 24 h caused marked changes in apoptosis-related gene expression. Genes as apaf1, bad, caspase 7, polb (DNA polymerase beta, performs base excision repair), and p53, which are marker genes for DNA damage, were upregulated. FAS and faslg were also markedly induced by treatment with OTA. Treatment of hepatocytes with OTA led to a concentration-dependent inhibition of protein biosynthesis. Apoptosis-inducing factor was released from mitochondria following OTA treatment; the mycotoxin induced the activity of caspases 8, 9, and 3/7 and caused chromatin condensation and fragmentation. Caspase inhibition led to a significant but not complete reduction of OTA-induced apoptosis. Our data suggest that not only OTA leads to p53-dependent apoptosis in rat hepatocytes but it also hints to other mechanisms, independent of caspase activation or protein biosynthesis, being involved.     

Rewiring and regulation of cross-compartmentalized metabolism in protists

Plastid acquisition, endosymbiotic associations, lateral gene transfer, organelle degeneracy or even organelle loss influence metabolic capabilities in many different protists. Thus, metabolic diversity is sculpted through the gain of new metabolic functions and moderation or loss of pathways that are often essential in the majority of eukaryotes. What is perhaps less apparent to the casual observer is that the sub-compartmentalization of ubiquitous pathways has been repeatedly remodelled during eukaryotic evolution, and the textbook pictures of intermediary metabolism established for animals, yeast and plants are not conserved in many protists. Moreover, metabolic remodelling can strongly influence the regulatory mechanisms that control carbon flux through the major metabolic pathways. Here, we provide an overview of how core metabolism has been reorganized in various unicellular eukaryotes, focusing in particular on one near universal catabolic pathway (glycolysis) and one ancient anabolic pathway (isoprenoid biosynthesis). For the example of isoprenoid biosynthesis, the compartmentalization of this process in protists often appears to have been influenced by plastid acquisition and loss, whereas for glycolysis several unexpected modes of compartmentalization have emerged. Significantly, the example of trypanosomatid glycolysis illustrates nicely how mathematical modelling and systems biology can be used to uncover or understand novel modes of pathway regulation.     

Current density and conductivity dependent electroporation of Escherichia coli C600

Transformation and surviving of E. coli C600 have been evaluated in dependence on the electric field strength and current density by changing the conductivity of the bacteria suspension. In this context the impact of making bacteria electrocompetent and the addition of NaCl solution was examined.Transformation efficiency declines with increasing conductivity of the suspension. When washing bacteria differently, the transformation efficiency correlates with the number of survivors. In contrary, adding different concentrations of NaCl has no effect on the surviving of E. coli C600.In dependence on the electric field strength, the transformation efficiency shows no effect on changing the conductivity. Regarding the transformation efficiency in dependence of the current density, a clear shift of the transformation maximum was observed. For higher conductivities, higher current densities are needed to reach the transformation maximum.     

Automated region of interest retrieval and classification using spectral analysis

Efficient use of whole slide imaging in pathology needs automated region of interest (ROI) retrieval and classification, through the use of image analysis and data sorting tools. One possible method for data sorting uses Spectral Analysis for Dimensionality Reduction. We present some interesting results in the field of histopathology and cytohematology. In histopathology, we developed a Computer-Aided Diagnosis system applied to low-resolution images representing the totality of histological breast tumour sections. The images can be digitized directly at low resolution or be obtained from sub-sampled high-resolution virtual slides. Spectral Analysis is used (1) for image segmentation (stroma, tumour epithelium), by determining a "distance" between all the images of the database, (2) for choosing representative images and characteristic patterns of each histological type in order to index them, and (3) for visualizing images or features similar to a sample provided by the pathologist. In cytohematology, we studied a blood smear virtual slide acquired through high resolution oil scanning and Spectral Analysis is used to sort selected nucleated blood cell classes so that the pathologist may easily focus on specific classes whose morphology could then be studied more carefully or which can be analyzed through complementary instruments, like Multispectral Imaging or Raman MicroSpectroscopy.     

Metabolic aspects of glycosomes in trypanosomatidae - new data and views

The energy metabolism of Trypanosomatidae has been the subject of many reviews during the past decade. In recent years, however, new data have led to a more complete picture of trypanosomatid metabolism and a reappraisal of the role of some characteristic organelles in the energy supply of these parasites. For years, the glycosome was thought to be a peroxisome-like organelle that had evolved to allow the parasites to carry out glycolysis at a high rate using a relatively small amount of enzyme. However, the results of recent studies of trypanosomatid glycolysis and the detection of various other pathways and enzymes in the organelle necessitate a modification of this view. Here, Paul Michels, Véronique Hannaert and Frédéric Bringaud review the new data and discuss the possible implications for our view on the role of the glycosome.