Andrew Stadnyk - Academia.edu (original) (raw)

Papers by Andrew Stadnyk

Digestive Diseases and Sciences, Mar 2, 2012

Infection and Immunity, Nov 1, 2000

The Canadian journal of gastroenterology, 2002

Journal of the Canadian Association of Gastroenterology, Feb 1, 2018

Transplantation, Oct 1, 1998

We have found that feeding Brown Norway (BN) rat spleen cells to Lewis rats prior to transplantin... more We have found that feeding Brown Norway (BN) rat spleen cells to Lewis rats prior to transplanting BN kidneys prolongs allograft survival (mean: 8.8 days in unfed rats, 21 days in the BN cell-fed rats; longest survival: 11 days without allo-feeding vs. 37 days with feeding). We have also found that feeding BN cells both before and after transplantation further extends survival (mean: 38 days; longest survival: 105 days). We also examined the cells infiltrating the grafts during the early stages of the allograft response (day 5). Using flow cytometry, we found a significant decrease in the number of leukocytes infiltrating the transplanted kidneys of fed animals. This decrease was mainly due to a drop in the number of infiltrating T cells. We also found that cytokine mRNA production by the graft-infiltrating lymphocytes, assessed by reverse transcription polymerase chain reaction, showed a significant increase in interleukin-4 and transforming-growth factor-beta mRNA in the graft-infiltrating lymphocytes of fed animals compared with the controls.

Journal of Pediatric Gastroenterology and Nutrition, Jun 1, 2004

Inflammatory Bowel Diseases, Jun 1, 2010

Two articles in this edition of Inflammatory Bowel Diseases advance the debate over whether Fas/F... more Two articles in this edition of Inflammatory Bowel Diseases advance the debate over whether Fas/FasL interactions underlie intestinal epithelial cell apoptosis during colitis. Chen et al present a state-of-the-art opinion on the evidence for a role for Fas/FasL in apoptosis and cancer but also on other possible mechanisms. Then the same group provides an original research article suggesting that the Fas/FasL mechanism in the dextran sulfate sodium (DSS)-induced colitis model in mice is in fact cytoprotective for epithelial cells.

Pathology and Immunopathology Research, 1985

In considering the pathology associated with infectious diseases, the most common host response t... more In considering the pathology associated with infectious diseases, the most common host response to such infection is inflammation. The mechanism(s) whereby inflammation is initiated and the cell types involved will dictate the kinds of acute phase plasma changes that can be seen associated with the infection. Bacteria seem to initiate the classical type of inflammatory response and plasma protein changes similar to those seen in experimental inflammation induced by chemical means. Viruses, on the other hand, in the absence of cytopathology do not appear to induce the same kind of inflammatory changes and avoid the induction of the acute phase protein response since they may not initiate activation of monocytes and/or macrophages. Those viruses that do cause macrophage activation would be expected to have acute phase protein changes associated with that activation. Parasites, however, appear to initiate the acute phase plasma response only when their migration leads to tissue destruction and local inflammation such as caused by parasitemia with Trypanosoma cruzi in the mouse or with migration of Nippostrongylus brasiliensis in the rodent. Human parasitic diseases require much more investigation in order to clarify the role played by acute phase proteins in the subsequent establishment of the host-parasite relationship. We postulate that the macrophage or monocyte on interaction with the infectious pathogen becomes activated and secretes a number of factors, including interleukin 1 and hepatocyte-stimulating factor, which have a marked effect on the total acute phase reaction. In addition to an effect on phagocytic and immune systems, the mediators cause hepatocytes to markedly increase the secretion of plasma acute phase proteins. Some of these proteins return to the site of inflammation and interact with the infectious pathogen and/or cells and proteins of the host, thereby affecting the final outcome of inflammation. We also propose that the initial interaction of an organism such as a parasite and the mammalian host involves early recognition by the macrophage, thereby initiating both the humoral and cellular acute phase reactions and subsequently affects the immune response against the parasite. Variations in the acute phase reaction may help to explain differences in susceptibility to infectious organisms and the presence or lack of host killing mechanisms for the parasite.

Journal of Leukocyte Biology, Aug 27, 2007

Journal of Leukocyte Biology, Nov 1, 2012

Journal of Immunology, May 1, 2020

IL-10 is widely appreciated as a potent anti-inflammatory cytokine, acting on leukocytes in mucos... more IL-10 is widely appreciated as a potent anti-inflammatory cytokine, acting on leukocytes in mucosal immunity. Far less attention has been paid to the impact of IL-10 on epithelial cells, which make up the crucial barrier interface between the host mucosa and the external environment. Furthermore, most studies look into the effects of exogenous IL-10, disregarding the possible presence and function of endogenous IL-10 in the epithelium. Using ex vivo organoids we aimed to dissect any role for endogenous epithelial IL-10. We discovered that cells in small intestinal organoids (enteroids) derived from C57BL/6 mice produced IL-10 constitutively throughout development. IL-10 mRNA increased considerably on day 3, the time when enteroids begin “budding” to create crypt-like structures. In addition, a second IL-10 increase was detected at day 6 when enteroids are typically “mature”. Immunofluorescent staining for IL-10 on day 4 enteroids was localized to Paneth cells. As gut epithelial cells are constantly exposed to bacteria, we added LPS at the start of enteroid cultures and observed that IL-10 staining was significantly increased. To further investigate the role of endogenous IL-10, we grew enteroids from IL-10 gene knockout mice. IL-10 deficient enteroids develop to morphologically resemble wild-type enteroids. We are proceeding to examine any difference in permeability, cell lineages and apoptosis between the two enteroid genotypes. In conclusion, IL-10 is present in the developing small intestinal epithelium and while development is IL-10-independent, whether IL-10 impacts subcellular components is under investigation.

Leukemia & Lymphoma, Jul 19, 2021

Abstract Treatment of pediatric acute lymphoblastic leukemia (ALL) with pegaspargase exploits ALL... more Abstract Treatment of pediatric acute lymphoblastic leukemia (ALL) with pegaspargase exploits ALL cells dependency on asparagine. Pegaspargase depletes asparagine, consequentially affecting aspartate, glutamine and glutamate. The gut as a confounding source of these amino acids (AAs) and the role of gut microbiome metabolism of AAs has not been examined. We examined asparagine, aspartate, glutamine and glutamate in stool samples from patients over pegaspargase treatment. Microbial gene-products, which interact with these AAs were identified. Stool asparagine declined significantly, and 31 microbial genes changed over treatment. Changes were complex, and included genes involved in AA metabolism, nutrient sensing, and pathways increased in cancers. While we identified changes in a gene (iaaA) with limited asparaginase activity, it lacked significance after correction leaving open other mechanisms for asparagine decline, possibly including loss from gut to blood. Understanding pathways that change AA availability, including by microbes in the gut, could be useful in optimizing pegaspargase therapy.

The FASEB Journal, Mar 1, 2008