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Biomedical subjects

David McFadden

Publications and source records attributed to David McFadden.

7 recordsLinked to original sources
PubMed2006

Peptide YY attenuates STAT1 and STAT3 activation induced by TNF-alpha in acinar cell line AR42J.

BACKGROUND: STAT1 and STAT3, members of the cytoplasmic family of signal transducers and activators of transcription factors (STAT), have been associated with numerous inflammatory pathologies, including inflammatory bowel disease, hepatitis, and acute lung injury. But little is known about their role in the pancreas. Peptide YY (PYY), an inhibitory gastrointestinal hormone, ameliorates pancreatitis in vivo and in vitro. In addition, we have shown that PYY attenuates transcription factors, such as nuclear transcription factor (NF)-kappaB and Smad3/4, which mediate inflammation. We hypothesized that tumor necrosis factor (TNF)-alpha would induce STAT1 and STAT3, and PYY would attenuate their transcription factor binding. STUDY DESIGN: Rat pancreatic acinar cells were treated with recombinant TNF-alpha (200 ng/mL); PYY (3-36; 500 pM) was added 30 minutes post-TNF-alpha treatment. Cells were harvested at 2 hours, and nuclear protein and conditioned media were extracted. Levels of amylase secretion and cytokine production were measured using commercially available kits. STAT transcription factor binding was determined by protein/DNA array analysis and densitometry; results were verified again by electrophoretic mobility shift assay (EMSA) and ELISA-based assay. RESULTS: Amylase production was considerably increased (p < 0.05) as early as 5 minutes after addition of exogenous TNF-alpha and remained elevated for 24 hours. PYY decreased amylase production to control levels. A notable increase (p < 0.05) in the production of cytokines interleukin (IL)-1beta, IL-4, IL-6, IL-10, and TNF-alpha was observed with TNF-alpha treatment; production was reduced with PYY. TNF-alpha substantially upregulated STAT1 and STAT3 (two-fold or greater); PYY downregulated their binding activity to control levels. Results from both the electrophoretic mobility shift assay- and the ELISA-based assays verified STAT1 and STAT3 responses to TNF-alpha and PYY. CONCLUSIONS: In pancreatic acinar cells, TNF-alpha activated STAT1 and STAT3, known mediators of inflammatory cytokines. Interestingly, PYY attenuated their protein/DNA binding, which may have an impact on development of the disease. Additional investigation of STAT proteins and PYY could provide new therapeutic strategies for pancreatitis.

Amylases↗
PubMed2005

Effects of HIV-1 infection on lymphocyte phenotypes in blood versus lymph nodes.

Most immunopathogenesis studies of HIV-1 use peripheral blood. Most lymphocytes reside in lymphoid tissues, however, and the extent to which blood mirrors tissues is unclear. Here, we analyze lymphocytes in blood and lymph nodes of HIV-1-uninfected and -infected persons. Baseline comparison of node and blood lymphocytes in seronegative persons demonstrates a lower ratio of CD8+ versus CD4+ T lymphocytes, a lower number of effector cells (CD28-) within the CD8+ compartment, and greater activation (D-receptor [DR+]) within the CD4+ compartment. In infected versus uninfected persons, nodes exhibit elevated CD8+ T lymphocytes with an increased memory-effector phenotype (CD62L-/CD45RA-) and activation (CD38+ and DR+) but minimal differences in the CD4+ compartment. Changes attributable to HIV-1 infection are markedly greater in node lymphocytes than in blood. Comparisons of CD8+ T-lymphocyte parameters and viremia in infected persons reveal positive correlations of CD38+ expression on cells in blood and nodes and a negative correlation of terminal effector cells (CD62L-/CD45RA+) in the nodes to viremia. Multiple linear regression analysis indicates that CD38 expression on node (not blood) CD8+ T lymphocytes is the sole independent predictor for viremia. Thus, blood indirectly reflects processes in lymphoid tissues, and caution should be applied when interpreting immunopathogenesis studies of blood.

Adult↗
PubMed2005

Developing the young academic surgeon.

In the past, the process of developing the young academic surgeon was arguably less strategic, one that was often not deliberately managed and monitored, leading in some cases to academic drift and disillusionment. Once upon a time it was assumed that greatness was genetic and that the next triple threat would emerge when a pre-programmed set of genes was turned on. Today, as the complexities and vicissitudes of our work increase, it is practically impossible for even the most gifted young person to be successful without careful attention to career development. Faculty development must be deliberate and strategic--every junior faculty member is unique and will require a customized career development plan that is well thought out, linked to measurable goals, monitored routinely and buttressed by effective mentoring. This approach will require time and commitment--precious commodities that are in short supply as the demands on our time are only escalating. By recruiting the right people (those who fit with the organization's values and goals) and providing the right environment, we can optimize the growth and satisfaction of our young faculty and, in so doing, create departments that are leaders in carrying out our missions of research, education and patient care. We cannot afford to have our young people fail--it is simply too costly, both from a financial and a human perspective.

Academic Medical Centers↗
PubMed2004

Developing the young academic surgeon.

In the past, the process of developing the young academic surgeon was arguably less strategic, one that was often not deliberately managed and monitored, leading in some cases to academic drift and disillusionment. Once upon a time it was assumed that greatness was genetic and that the next triple threat would emerge when a pre-programmed set of genes was turned on. Today, as the complexities and vicissitudes of our work increase, it is practically impossible for even the most gifted young person to be successful without careful attention to career development. Faculty development must be deliberate and strategic--every junior faculty member is unique and will require a customized career development plan that is well thought out, linked to measurable goals, monitored routinely and buttressed by effective mentoring. This approach will require time and commitment--precious commodities that are in short supply as the demands on our time are only escalating. By recruiting the right people (those who fit with the organization's values and goals) and providing the right environment, we can optimize the growth and satisfaction of our young faculty and, in so doing, create departments that are leaders in carrying out our missions of research, education and patient care. We cannot afford to have our young people fail--it is simply too costly, both from a financial and a human perspective.

Academic Medical Centers↗
PubMed2004

Peptide YY attenuates transcription factor activity in tumor necrosis factor-alpha-induced pancreatitis.

BACKGROUND: Acute pancreatitis (AP) is a disease characterized by inflammation. Nuclear factor (NF)-kappaB, Smad proteins, and the steroid hormone family peroxisome proliferator-activated receptors (PPARs) are involved in regulation of gene transcription during the disease process. Peptide YY (PYY), a gastrointestinal hormone, inhibits NF-kappaB translocation to acinar nuclei in tumor necrosis factor (TNF)-alpha-induced AP. We investigated TNF-alpha induction of Smad proteins, PPARalpha/gamma, and NF-kappaB by TNF-alpha, and hypothesized that PYY would attenuate this effect. STUDY DESIGN: Rat acinar cells were treated with recombinant TNF-alpha (200 ng/mL). PYY (3 to 36) was added at 500 pM at 30 minutes after TNF-alpha treatment until cell harvest at 2 hours. Western blot analysis and intracellular staining of the p65 subunit of NF-kappaB were performed. NF-kappaB, Smad3/4, and PPARalpha/gamma binding activities were determined by protein/DNA array analysis and verified by electrophoretic-mobility shift assay and densitometry. RESULTS: Cellular localization of NF-kappaB p65 showed nuclear staining within 2 hours, with controls stained in the cytoplasm. With PYY, p65 stained in the cytoplasm. Nuclear p65 was increased significantly (p < 0.05) by TNF-alpha at 2 hours and PYY reduced it. Array analysis revealed upregulation of NF-kappaB, PPARalpha/gamma, and Smad3/4 with TNF-alpha. TNF-alpha stimulated NF-kappaB activation sevenfold, and binding was enhanced (p < 0.05). PYY reduced NF-kappaB binding to control levels. PPAR binding increased 51% after TNF-alpha treatment and was reduced to 33% with PYY. Smad3/4 binding was increased (p < 0.05) above controls with TNF-alpha and PYY reduced it by 40%. CONCLUSIONS: TNF-alpha increases early nuclear translocation of the p65 subunit of NF-kappaB in acinar cells. Exposure to TNF-alpha activates transcription factors NF-kappaB, Smad3/4, and PPARalpha/gamma. PYY reduces this activation. Treatment with PYY may have therapeutic potential in improving AP.

Acute Disease↗
PubMed2002

In vitro anticancer effects of a novel immunostimulant: keyhole limpet hemocyanin.

BACKGROUND: Keyhole limpet hemocyanin (KLH) is a recently described immune stimulant and hapten carrier derived from a circulating glycoprotein of the marine mollusk Megathura crenulata. It has been reported to be a potent form of intravesical immunotherapy for the treatment of transitional cell carcinoma of the bladder and has been used in a variety of genitourinary tumors. We hypothesized that KLH would be effective against other cancer cells in vitro. METHODS: Multiple cancer cell lines were tested, including estrogen-dependent breast (MCF-7), estrogen-independent breast (ZR75-1), pancreas (PANC-1, MIA-PaCa), and prostate (DU145). Serial twofold dilutions of KLH were prepared in sterile 96-well plates. Dose-response curves were performed beginning with a concentration of 100 microg of KLH/well and ending at a concentration of 0.8 ng/well. Cells were added at concentrations of 5 x 10(4) cells per well. Cell viability was evaluated at 24 and 72 h by MTT assay at an absorbance of 570 nm. RESULTS: Significant (P < 0.05) cancer cell growth inhibition was observed in four of the five cell lines tested at both time treatment intervals. The breast cancer line ZR75-1 exhibited a mean growth inhibition of 43 +/- 1.1% (range 37 to 59%) at 72 h, whereas treated MCF-7 cells had an average of 39 +/- 9.1% growth inhibition (range 35 to 44%) at these same concentrations. Treated PANC-1 cells had a mean growth inhibition of 19 +/- 0.8% (range 4 to 46%) at 72 h. The DU145 prostate cancer cell line averaged a 6 +/- 1.3% growth inhibition (range -19 to 55%) over the concentrations tested. CONCLUSIONS: The direct growth inhibition of multiple tumor cell-lines exhibited by KLH is significant and warrants further in vitro mechanistic studies and in vivo experiments. Investigation into the efficacy and mechanism of response could directly lead to more effective treatment regimens for patients suffering from these diseases.

Adjuvants, Immunologic↗