Greg Pahel - Academia.edu (original) (raw)

Papers by Greg Pahel

Biochemical and Biophysical Research Communications, 2005

We investigated the effect of peroxisome proliferator-activated receptor gamma (PPARc) agonists o... more We investigated the effect of peroxisome proliferator-activated receptor gamma (PPARc) agonists on serum vascular endothelial growth factor (VEGF) in diet-induced insulin resistant SD rats and ZDF rats. SD rats fed a high fat/sucrose diet showed increases in serum insulin and VEGF (both p < 0.01). Treatment with a PPARc agonist GI262570 normalized the diet-elevated insulin and VEGF (both p < 0.01). There was a positive correlation between serum insulin and VEGF (p < 0.05) in SD rats. ZDF rats had higher serum glucose, insulin, and VEGF than Zucker lean rats (all p < 0.01). Treatment of ZDF rats with PPARc agonist pioglitazone decreased serum glucose and VEGF (both p < 0.01). There was a positive correlation between glucose and VEGF in ZDF rats (p < 0.05). In 3T3-L1 adipocytes, GI262570 did not affect insulin-stimulated VEGF secretion. These studies demonstrated that hyperinsulinemia in SD rats and hyperglycemia in ZDF rats were associated with increased serum VEGF; PPARc agonists normalized serum insulin, glucose, and VEGF, but did not affect VEGF secretion in vitro.

Biochemical and Biophysical Research Communications, 2006

The current study examined the relationship between skeletal muscle levels of adiponectin and par... more The current study examined the relationship between skeletal muscle levels of adiponectin and parameters of insulin sensitivity. A high fat/sucrose diet (HFD) for 20 weeks resulted in significant increases in body weight, serum insulin, triglycerides (TG), and free fatty acids (FFA) (all p < 0.01). Interestingly, this diet leads to a slight increase in serum adiponectin, but significant decreases in gastrocnemius muscle and white adipose adiponectin (all p < 0.05). HFD for 4 weeks also resulted in a significant decrease in muscle adiponectin, which correlated with serum insulin, TG, and FFA (all p < 0.05). Treatment of the 4-week HFD rats with a PPARc agonist GI262570 ameliorated the diet-induced hyperinsulinemia and dyslipidemia, and effectively restored muscle adiponectin (all p < 0.05). This study demonstrated that HFD-induced hyperinsulinemia and dyslipidemia appeared without changes in serum adiponectin, but were associated with decreased tissue adiponectin. This provides the first evidence for a connection between tissue adiponectin and diet-induced hyperinsulinemia and dyslipidemia.

LPS exposure time was 90 minutes. * p < 0.05 vs no-LPS. ** p < 0.01 vs no-LPS. + p < 0.0... more LPS exposure time was 90 minutes. * p < 0.05 vs no-LPS. ** p < 0.01 vs no-LPS. + p < 0.05 vs no-RU486.Copyright information:Taken from "RU486 did not exacerbate cytokine release in mice challenged with LPS nor in db/db mice"http://www.biomedcentral.com/1471-2210/8/7BMC Pharmacology 2008;8():7-7.Published online 12 May 2008PMCID:PMC2396158.

LPS dose in (b) and (d) was 0.5 mg/kg.Copyright information:Taken from "R... more LPS dose in (b) and (d) was 0.5 mg/kg.Copyright information:Taken from "RU486 did not exacerbate cytokine release in mice challenged with LPS nor in db/db mice"http://www.biomedcentral.com/1471-2210/8/7BMC Pharmacology 2008;8():7-7.Published online 12 May 2008PMCID:PMC2396158.

db/db-V: db/db mice treated with Vehicle. db/db-RU 2.5: db/db mice treated with RU486 2.5 mg/kg. ... more db/db-V: db/db mice treated with Vehicle. db/db-RU 2.5: db/db mice treated with RU486 2.5 mg/kg. db/db-RU 7: db/db mice treated with RU486 7 mg/kg. db/db-RU 20: db/db mice treated with RU486 20 mg/kg. db/db-RU 50: db/db mice treated with RU486 50 mg/kg. Serum corticosterone and ACTH were presented as ng/ml. PEPCK and G6Pase were normalized with cyclophilin.Copyright information:Taken from "RU486 did not exacerbate cytokine release in mice challenged with LPS nor in db/db mice"http://www.biomedcentral.com/1471-2210/8/7BMC Pharmacology 2008;8():7-7.Published online 12 May 2008PMCID:PMC2396158.

Protein Expression and Purification, 2000

Replication of human papillomavirus type11 (HPV11) requires both the E1 and the E2 proteins. E1 i... more Replication of human papillomavirus type11 (HPV11) requires both the E1 and the E2 proteins. E1 is structurally and functionally similar to SV40 large T-antigen and is a DNA helicase/NTPase that binds to the origin of replication and initiates viral DNA replication. The biochemical characterization of HPV E1 is incompletely documented in the literature in part because of difficulties in expressing and purifying the protein. Herein, we report a method for the overexpression of full-length, untagged E1 (73.5 kDa) in baculovirus-infected Trichoplusia ni insect cells and the purification to homogeneity using a two-step procedure. The purified protein is a nonspecific NTPase that hydrolyzes ATP, dATP, UTP, or GTP equally well. Point mutations were made in the putative NTPase domain to verify that the activities observed were encoded by E1. Purified mutant D523N had negligible ATPase and helicase activities but retained DNA-binding activity. Sedimentation equilibrium ultracentrifugation and glycerol gradient centrifugation demonstrated that the wild-type protein is primarily a hexamer in its purified form. Secondary structure determination by circular dichroism revealed a large percentage of ␣-helical structure consistent with secondary structure predictions. These data define a fundamental set of biochemical and kinetic parameters for HPV E1 which are a critical prerequisite to future mechanistic studies of the enzyme.

BMC Pharmacology, 2008

Background: Glucocorticoids down-regulate cytokine synthesis and suppress inflammatory responses.... more Background: Glucocorticoids down-regulate cytokine synthesis and suppress inflammatory responses. The glucocorticoid receptor (GR) antagonist RU486 may exacerbate the inflammatory response, and concerns over this exacerbation have limited the development and clinical use of GR antagonists in the treatment of diabetes and depression. We investigated the effects of RU486 on serum cytokines in db/db mice and on lipopolysaccharide (LPS)-induced circulating TNFα levels in both normal AKR mice and diet-induced obese (DIO) C57BL/6 mice. Results: Chronic treatment of db/db mice with RU486 dose-dependently decreased blood glucose, increased serum corticosterone and ACTH, but did not affect serum MCP-1 and IL-6 levels. LPS dose-dependently increased serum TNFα in both AKR and C57BL/6 DIO mice, along with increased circulating corticosterone and ACTH. Pretreatment of the mice with RU486 dosedependently suppressed the LPS induced increases in serum TNFα and further increased serum corticosterone. Conclusion: RU486 at doses that were efficacious in lowering blood glucose did not exacerbate cytokine release in these three mouse models. RU486 actually suppressed the lower dose LPSmediated TNFα release, possibly due to the increased release of glucocorticoids.

Proceedings of the National Academy of Sciences, 1979

Mutations in the glnA region of the Escherichia coli chromosome due to Mu prophage insertion resu... more Mutations in the glnA region of the Escherichia coli chromosome due to Mu prophage insertion result in two phenotypic classes. One class is Gln- and does not synthesize glutamine synthetase[L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] under any growth condition. The other class produces a low level of glutamine synthetase under all growth conditions and is uncoupled from the regulatory effects of mutations in the glnF and glnD genes. Complementation analysis demonstrates that these two classes of insertions are in different cistrons. From these data we suggest that a regulatory gene, glnG, tightly linked to glnA, mediates both activation and repression of glutamine synthetase synthesis. An analysis of the evidence accumulated to date makes it unlikely that glnG is the only gene in the glnA region involved in the complex system of nitrogen regulation.

Journal of Biological Chemistry, 1993

Glutamine: Metabolism, Enzymology, and Regulation, 1980

Journal of bacteriology, 1985

We have isolated insertion and deletion mutants in glnB, the structural gene of PII, a member of ... more We have isolated insertion and deletion mutants in glnB, the structural gene of PII, a member of the adenylylation system for glutamine synthetase of Escherichia coli, to study the role of PII in the regulation of the synthesis of glutamine synthetase and of histidase in response to nitrogen deprivation or excess. We have studied the effects of this mutation alone and combined with null mutations resulting from the insertion of transposons or from a deletion in the other genes affecting this regulation, glnD, glnF (ntrA), glnG (ntrC), and glnL (ntrB). Our results confirm that only the products of glnF and glnG are essential for this regulation. In cells of the wild type, the response is mediated by the products of glnD and glnB via the product of glnL. In the condition of nitrogen excess, PII, the product of glnB, appears to convert the product of glnL to a form that prevents the activation of transcription of the structural genes for glutamine synthetase and for histidase by the pr...