Genetic interactions between a phospholipase A2 and the Rim101 pathway components in S. cerevisiae reveal a role for this pathway in response to changes in membrane composition and shape

Modulating composition and shape of biological membranes is an emerging mode of regulation of cellular processes. We investigated the global effects that such perturbations have on a model eukaryotic cell. Phospholipases A2 (PLA2s), enzymes that cleave one fatty acid molecule from membrane phospholipids, exert their biological activities through affecting both membrane composition and shape. We have conducted a genome-wide analysis of cellular effects of a PLA2 in the yeast Saccharomyces cerevisiae as a model system. We demonstrate functional genetic and biochemical interactions between PLA2 activity and the Rim101 signaling pathway in S. cerevisiae. Our results suggest that the composition and/or the shape of the endosomal membrane affect the Rim101 pathway. We describe a genetically and functionally related network, consisting of components of the Rim101 pathway and the prefoldin, retromer and SWR1 complexes, and predict its functional relation to PLA2 activity in a model eukaryotic cell. This study provides a list of the players involved in the global response to changes in membrane composition and shape in a model eukaryotic cell, and further studies are needed to understand the precise molecular mechanisms connecting them

Role of frozen section evaluation in patients with breast lumps: A study of 251 cases

Context: Frozen section is an invaluable intra-operative tool for evaluation of breast lumps. Aims: The aim of this study was to (1) calculate the overall accuracy, false positivity, false negativity for frozen section of breast lumps, (2) analyze the causes of discrepancies, and (3) compare the data with that of published literature on frozen section of breast lumps. Material and Methods: Two hundred and fifty one frozen sections comprising 237 breast lumps, 10 axillary nodes and 4 lumpectomy margins received for frozen section in 1997 were analyzed. Pathology reports and slides (of both frozen and paraffin sections) were reviewed. The values were calculated using paraffin slides as the gold standard. Results: The 237 lumps received for primary diagnosis comprised 157 malignant and 80 benign lesions. The false negativity rate was 0.42%, false positive rate 0%, deferral rate 0.84%, overall accuracy rate was 99.57%. The false negative diagnosis was an error of interpretation. False negativity rate for axillary nodes was 20% and accuracy was 80%. Accuracy for margins was 100%. Conclusion: Frozen section has a role despite the raging popularity of aspiration cytology in the following settings: (1) Difficult cytology (2) Evaluation of lumpectomy margins. (3) Intra-operative nodal status