Comment on “Updated meta-analysis of pancreatic stent placement in preventing post-endoscopic retrograde cholangiopancreatography pancreatitis”

I read with interest an article “Updated meta-analysis of pancreatic stent placement in preventing post-endoscopic retrograde cholangiopancreatography pancreatitis” by Fan and colleagues in World J Gastroenterol 2015; 21(24): 7577-7583. Although I appreciate their work, I have found problems with the data extracted and analyzed by the authors, and will give my comment in this letter. It would be valuable if the authors could provide an accurate estimation of their extracted data.

Dexamethasone suppresses apoptosis in a human gastric cancer cell line through modulation of bcl-x gene expression

Treatment of human gastric cancer TMK-1 cells with transcription and translation inhibitors rapidly triggered cell apoptosis. Along with cell apoptosis, the Bcl-xS level was markedly upregulated suggesting a crucial role of this protein in promoting the apoptotic process. In the presence of dexamethasone, however, cell apoptosis was greatly attenuated as demonstrated by DNA histogram shift and DNA fragmentation. Studies using the glucocorticoid receptor antagonist RU486 indicated that attenuation of apoptosis was mediated through glucocorticoid receptors. Dexamethasone not only suppressed the apoptosis-associated upregulation of Bcl-xS but also enhanced the basal level of Bcl-xL in the cells. In addition, bcl-x mRNA stability was significantly extended in the presence of dexamethasone. These results indicate that dexamethasone exerted a protective effect and delayed apoptosis of TMK-1 cells by modulating bcl-x gene expression.

Effects of transcription and translation inhibitors on a human gastric carcinoma cell line. Potential role of Bcl-X(S) in apoptosis triggered by these inhibitors

The effects of the macromolecular synthesis inhibitors 5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole (DRB), actinomycin D, and cycloheximide on the human gastric cancer TMK-1 cell line were studied. These agents inhibited DNA, RNA, or protein synthesis efficiently and induced cell death rapidly in a wide range of concentrations. After 8 hr of exposure to these agents, the cells exhibited morphological features of apoptosis, including cell shrinkage, nuclear condensation, DNA fragmentation, and formation of apoptotic bodies. Western blot analysis revealed that these inhibitors altered the protein levels of apoptosis-related gene products such as c-Myc, Bcl-X(S), and the mutant p53 (mp53) in TMK-1 cells markedly. The c-myc mRNA and protein levels were decreased initially and were then induced markedly to a new level after 4 hr of exposure to DRB, a RNA polymerase II inhibitor. The Bcl-X(S) levels were increased rapidly after treatment with all of these agents, whereas the levels of Bcl-X(L) and Bax remained largely unchanged. Northern blot analysis indicated that the c-myc overexpression is concomitant to DRB-induced DNA fragmentation and that the increased mp53 protein level was mainly a posttranscriptional event. Our observations suggest that the up-regulation of Bcl-X(S) may serve as an important mechanism for the apoptosis triggered by these inhibitors. This study also provides evidence for the notion that interference with the cellular survival pathway may lead to apoptosis.

Approximations of bayes and minimax risks and the least favorable distribution

In this paper we present a method for approximating the risks and Bayes risk associated with a Bayes decision procedure. Additionally, our method leads to approximating the least favorable distribution and the risk associated with the minimax decision procedure. We assume two states of nature (or classes of patterns) and multivariate probability density functions. Taylor series expansions are used, and an nth-order polynomial equation derived from such expansions provides an approximation to one of the least favorable probabilities. An application to a normally distributed random vector of observables is presented with numerical comparisons. The method can be generalized to cases having more than two states of nature by using Taylor series expansions in several variables.

The relationship of the bayes risk to certain separability measures in normal classification

For the problem of classifying an element (e.g., an unknown pattern) into one of two given categories where the associated observables are distributed according to one of two known multivariate normal populations having a common covariance matrix, it is shown that the minimum Bayes risk is a strict monotonic function of certain separability or statistical distance measures regardless of the a priori probabilities and the assigned loss function. However, for the associated conditional expected losses, strict monotonicity holds, if and only if a certain condition dependent on these probabilities and the given loss function is satisfied. These results remain valid for classification problems in which the observable can be transformed by a one-to-one differentiable mapping to normality.