Biomedical subjects

Gregory G Freund

Publications and source records attributed to Gregory G Freund.

26 records · Page 2Linked to original sources

PubMed2003

Effectiveness of the SurePath liquid-based Pap test in automated screening and in detection of HSIL.

We have shown that SurePath when compared to conventional Paps fails to increase HSIL detection. In this study, assessment of test performance characteristics for the FocalPoint showed that sensitivity was 96% when manual screening was used as the "gold standard." When cervical biopsy, however, was used as the "gold standard" FocalPoint sensitivity decreased to 93%, which was the same as manual screening. Examination of the FocalPoint "no further review" cases showed that 4/296 were SIL. To understand better the implication of an SIL diagnosis, cervical biopsies generated from SurePath and conventional Paps were compared. Conventional Paps diagnosed as LSIL had a biopsy LSIL:HSIL ratio of 3.1/1, while SurePath Paps had a biopsy LSIL:HSIL ratio of 1.5/1. These results indicate that when cervical biopsy is used as the "gold standard," FocalPoint and manual screening of SurePath Paps have similar test performance but that the FocalPoint can fail to detect LSIL. Importantly, LSIL in a SurePath Pap is 1.6 times more likely to be HSIL on biopsy than LSIL in a conventional Pap.

False Negative Reactions↗

PubMed2003

Vanadate and rapamycin synergistically enhance insulin-stimulated glucose uptake.

Tyrosine dephosphorylation, serine phosphorylation, and proteasomal degradation of insulin receptor substrates (IRSs) are implicated in the negative regulation of insulin action. Here we show that simultaneous inhibition of IRS-1 tyrosine dephosphorylation and proteasomal degradation synergistically augments insulin-responsive glucose uptake. L6 skeletal muscle cells (L6 cells) were treated with inhibitors of protein-tyrosine phosphatases, proteasomal degradation, and mammalian target of rapamycin (mTOR), and the effects of insulin on glucose uptake, IRS-1 tyrosine phosphorylation, phosphatidylinositol (PI) 3-kinase activity, and IRS-1 mass were examined. Pretreatment of L6 cells with sodium orthovanadate (Na(3)VO(4)) plus the mTOR inhibitor rapamycin caused a 5-fold increase in insulin-responsive glucose uptake at 2 hours when compared to insulin alone. Evaluation of IRS-1 associated PI 3-kinase activity, IRS-1-associated p85 mass, and IRS-1 tyrosine phosphorylation showed that 2 hours after insulin addition they were reduced by 70% from maximal activity. Likewise, IRS-1 mass was reduced by 50%. When L6 cells were pretreated with Na(3)VO(4) plus the proteasome inhibitor MG-132 or the mTOR inhibitor rapamycin prior to insulin addition, IRS-1 mass loss as well as IRS-1/PI-3 kinase complex decay was blocked at 2 hours and PI 3-kinase activity was increased 2.5-fold and 4-fold, respectively, over insulin alone. Finally, treatment of L6 cells with subtherapeutic amounts of vanadyl sulfate and rapamycin induced a synergistic 3-fold increase in insulin-induced glucose uptake at 2 hours. These findings indicate that vanadium and rapamycin synergize to enhance glucose uptake by preventing IRS-1 mass loss and IRS-1/PI 3-kinase complex decay and may offer a new approach to enhance glucose transport in diabetes.

Animals↗

PubMed2003

Cytokine-hormone interactions: tumor necrosis factor alpha impairs biologic activity and downstream activation signals of the insulin-like growth factor I receptor in myoblasts.

TNFalpha is elevated following damage to skeletal muscle. Here we provide evidence that TNFalpha acts on muscle cells to induce a state of IGF-I receptor resistance. We establish that TNFalpha inhibits IGF-I-stimulated protein synthesis in primary porcine myoblasts. Similar results were observed in C(2)C(12) murine myoblasts, where as little as 0.01 ng/ml TNFalpha significantly inhibits protein synthesis induced by IGF-I. TNFalpha also impairs the ability of IGF-I to induce expression of a key myogenic transcription factor, myogenin. The inhibition by TNFalpha of IGF-I-induced protein synthesis and expression of myogenin is not due to direct killing of myoblasts by TNFalpha. Although IGF-I induces an approximately 19-fold induction in tyrosine phosphorylation of the beta-chains of its receptor, TNFalpha does not inhibit this autophosphorylation. Instead, TNFalpha significantly reduces by approximately 50% IGF-I-stimulated tyrosine phosphorylation of two of the major downstream receptor docking molecules, insulin receptor substrate (IRS)-1 and IRS-2. These results establish that low picogram concentrations of TNFalpha acts on both porcine and murine myoblasts to impair tyrosine phosphorylation of both IRS-1 and IRS-2, but not the receptor itself. These data are consistent with the notion that very low physiological concentrations of TNFalpha interfere with both protein synthesis and muscle cell development by inducing a state of IGF-I receptor resistance.

Animals↗

PubMed2002

Proinflammatory cytokines block growth of breast cancer cells by impairing signals from a growth factor receptor.

Neutralization of endogenous growth factors and administration of exogenous bioactive cytokines are two distinct biological antitumor strategies that show promise for treatment of cancer patients. In this report, we provide evidence to link both strategies as an integrative approach to cancer therapy. We tested the hypothesis that proinflammatory cytokines block growth of transformed cells by inhibiting key intracellular signaling events after activation of the insulin-like growth factor-I (IGF-I) tyrosine kinase receptor. IGF-I stimulates DNA synthesis in MCF-7 cells by 15-fold. This increase is significantly inhibited by TNF (tumor necrosis factor) -alpha at 0.1 ng/ml and is reduced by 80% at 100 ng/ml. Similarly, both IL (interleukin) -1beta and IL-6 significantly reduce the ability of IGF-I to promote DNA synthesis. Flow cytometry confirmed that all three of the cytokines inhibit IGF-I-induced DNA synthesis by preventing cells from entering the S phase of the cell cycle, leading to G(0)/G(1) arrest. Although none of the cytokines alone are cytotoxic to transformed epithelial cells in the absence of serum, TNF-alpha significantly inhibits the antiapoptotic property of IGF-I in protecting MCF-7 cells from DNA fragmentation. TNF-alpha and IL-1beta act by inhibiting the IGF-I receptor from tyrosine phosphorylating insulin receptor substrate-1 without affecting tyrosine kinase activity of the IGF-IR itself. These data support the novel idea that the major inhibitory properties of proinflammatory cytokines on growth of breast cancer cells are manifested prominently in the presence of growth factors. These data also highlight growth factor receptor adaptor molecules, such as insulin receptor substrate-1, rather than the receptors themselves as targets for antitumor therapeutic strategies.

Adenocarcinoma↗

PubMed2002

IL-10 promotes survival of microglia without activating Akt.

IL-10 is an anti-inflammatory cytokine that has recently been shown to promote survival of neurons and glia. Here we establish that IL-10 induces phosphorylation of Stat3 on Tyr(705) and serves as a survival factor for N13 microglial cells. Recombinant IL-10 (10 ng/ml) decreases growth factor withdrawal-induced apoptosis by 50%, as assessed by TUNEL. In contrast to IL-10, IGF-I increases enzymatic activity of PI 3-kinase and causes phosphorylation on serine(473) of Akt but does not prevent microglial apoptosis. These data establish that IL-10 activates Stat3 and inhibits the mitochondrial pathway of cell death without activating the Akt cell survival pathway.

Animals↗

PubMed2002

Dual sampling of the endocervix and its impact on AutoCyte Prep endocervical adequacy.

We compared satisfactory for evaluation but limited by (limited by) and unsatisfactory gynecologic cytologic diagnoses for samples collected by conventional smearing with those generated with the AutoCyte Prep in a population with a historic squamous intraepithelial lesion (SIL) rate of less than 1%. Results from 18,819 AutoCyte Preps were compared with 53,835 conventional cervical smears. Furthermore, 23 women ages 18 to 65 years undergoing annual Papanicolaou tests underwent sequential sampling with the AutoCyte Prep and the Surgipath C-E brush. Comparison of the AutoCyte Prep with conventional cytologic diagnoses revealed the following: unsatisfactory rate, down 97%; limited by rate, down 67%; low-grade SIL rate, up 86%; cervical cancer rate, up 300%; and high-grade SIL rate, unchanged. Examination of unsatisfactory and limited by cases for the AutoCyte Prep showed that 88% were due to absence of endocervical cells (ECs). Dual sampling showed no improvement in EC recovery over the AutoCyte collection device. Compared with conventional Papanicolaou smears, the AutoCyte Prep significantly decreased the rate of unsatisfactory and limited by specimens while increasing low-grade SIL and cancer detection and EC recovery. The majority of limited by specimens with the AutoCyte Prep were due to absence of ECs, but use of a brush-type device for better endocervical sampling did not enhance EC recovery.

Adolescent↗

PubMed2001

Methylglyoxal enhances cisplatin-induced cytotoxicity by activating protein kinase Cdelta.

The cytotoxic side effects of anti-neoplastic drugs are increased in patients with either type 1 or type 2 diabetes mellitus by a mechanism that is not clearly defined. We report that the circulating glucose metabolite, methylglyoxal (MGO), enhances cisplatin-induced apoptosis by activating protein kinase Cdelta (PKCdelta). We found that treatment of myeloma cells with the antioxidant N-acetylcysteine completely blocked cisplatin-dependent intracellular GSH oxidation, reactive oxygen species (ROS) generation, poly(ADP-ribose) polymerase cleavage, and apoptosis. Importantly, co-treatment of cells with the reactive carbonyl MGO and cisplatin increased apoptosis by 90% over the expected additive effect of combined MGO and cisplatin treatment. This same synergism was also observed when ROS generation was examined. MGO and cisplatin increased PKCdelta activity by 4-fold, and this effect was blocked by the PKCdelta inhibitor rottlerin but not by NAC. Furthermore, rottlerin blocked combined MGO and cisplatin-induced ROS generation and apoptosis. Finally, MGO and cisplatin induced c-Abl activation and c-Abl:PKCdelta association. Rottlerin blocked c-Abl activation, but the c-Abl inhibitor STI-571 increased MGO and cisplatin-induced apoptosis by 50%. Taken together these data indicate that MGO synergistically enhances cisplatin-induced apoptosis through activation of PKCdelta and that PKCdelta is critical to both cell death and cell survival pathways. These findings suggest that in the patient with diabetes mellitus heightened oxidative stress can enhance the cytotoxicity of agents that induce DNA damage.

Acetylcysteine↗

PubMedDate not supplied

New red blood cell lysing fixative for use in fine needle aspiration and fluid cytology.

OBJECTIVE: To describe a new red blood cell (RBC) lysing fixative, Devine's lysing solution (DLS), that increases the diagnostic utility of fine needle aspiration (FNA) and fluid cytology. STUDY DESIGN: Twenty bloody FNA cases were fixed with either DLS or 95% ethanol, and the ability to render a diagnosis on these materials was analyzed. DLS was compared to the red cell lysing fixative CytoRich Red (CRR) (TriPath Care Technologies, Burlington, North Carolina, U.S.A.) in its ability to lyse RBCs by mixing human RBCs with the U266 multiple myeloma cell line. DLS was compared to CRR in its ability to suitably preserve materials for Papanicolaou and immunocytochemical analysis. RESULTS: Comparison of DLS with 95% ethanol fixation in 20 bloody FNA cases prepared in duplicate showed that DLS reduced from 17 to 3 the number of cases that had RBCs obscuring > or = 25% of the diagnostic material. In 3 cases, DLS enabled the rendering of a definitive diagnosis of malignancy, which could not be made on the ethanol-fixed material. DLS was compared to CRR, and both fixatives were similarly effective at lysing RBCs, preserving the cellular morphology of diagnostic cells in FNA and fluid cytology, and preserving cells for use in immunocytochemistry. CONCLUSIONS: DLS increases the visualization of diagnostic cellular material when compared to ethanol fixation. DLS is comparable to CRR in RBC lysing ability, diagnostic cell preservation and preservation of materials for immunocytochemistry.

Artifacts↗