Troglitazone but not metformin restores insulin-stimulated phosphoinositide 3-kinase activity and increases p110beta protein levels in skeletal muscle of type 2 diabetic subjects.

Insulin stimulation of phosphatidylinositol (PI) 3-kinase activity is defective in skeletal muscle of type 2 diabetic individuals. We studied the impact of antidiabetic therapy on this defect in type 2 diabetic subjects who failed glyburide treatment by the addition of troglitazone (600 mg/day) or metformin (2,550 mg/day) therapy for 3-4 months. Improvement in glycemic control was similar for the two groups, as indicated by changes in fasting glucose and HbA(1c) levels. Insulin action on whole-body glucose disposal rate (GDR) was determined before and after treatment using the hyperinsulinemic (300 mU x m(-2) x min(-1)) euglycemic (5.0-5.5 mmol/l) clamp technique. Needle biopsies of vastus lateralis muscle were obtained before and after each 3-h insulin infusion. Troglitazone treatment resulted in a 35 +/- 9% improvement in GDR (P < 0.01), which was greater than (P < 0.05) the 22 +/- 13% increase (P < 0.05) after metformin treatment. Neither treatment had any effect on basal insulin receptor substrate-1 (IRS-1)-associated PI 3-kinase activity in muscle. However, insulin stimulation of PI 3-kinase activity was augmented nearly threefold after troglitazone treatment (from 67 +/- 22% stimulation over basal pre-treatment to 211 +/- 62% post-treatment, P < 0.05), whereas metformin had no effect. The troglitazone effect on PI 3-kinase activity was associated with a 46 +/- 22% increase (P < 0.05) in the amount of the p110beta catalytic subunit of PI 3-kinase. Insulin-stimulated Akt activity also increased after troglitazone treatment (from 32 +/- 8 to 107 +/- 32% stimulation, P < 0.05) but was unchanged after metformin therapy. Protein expression of other key insulin signaling molecules (IRS-1, the p85 subunit of PI 3-kinase, and Akt) was unaltered after either treatment. We conclude that the mechanism for the insulin-sensitizing effect of troglitazone, but not metformin, involves enhanced PI 3-kinase pathway activation in skeletal muscle of obese type 2 diabetic subjects.     

RU486 increases radiosensitivity and restores apoptosis through modulation of HPV E6/E7 in dexamethasone-treated cervical carcinoma cells

OBJECTIVE: Cervical carcinoma tumors containing radioresistant cells are associated with decreased local control and survival. Therefore, strategies to increase cell kill during radiotherapy have a clear rationale. It was previously determined that treatment with the corticosteroid dexamethasone increased radioresistance and decreased apoptosis in C4-1 cervical carcinoma cells. The goal of this study was to determine whether hormone antagonists, specifically Mifepristone (RU486), could reverse the effects of dexamethasone on clonogenic survival and apoptosis following gamma-irradiation. METHODS: Cervical carcinoma cell line C4-1 cells were exposed to 1 microM dexamethasone in the presence or absence of 1 microM Mifepristone (RU486), a hormone antagonist, and irradiation. Cells were analyzed for steroid-dependent HPV E6/E7 mRNA expression (by Northern blot analysis), clonogenic survival, and apoptosis (by Annexin V staining and the DNA fragmentation assay). In addition, p53 protein levels were determined by Western blot analysis. RESULTS: The hormone antagonist RU486 reversed dexamethasone-dependent upregulation of E6/E7 mRNA and restored radiation-induced p53 expression, apoptosis, and clonogenic survival to levels similar to those observed following irradiation alone. CONCLUSION: RU486 reverses glucocorticoid-dependent upregulation of HPV E6/E7, which corresponds to restoration of p53 expression, and restores radiosensitivity and apoptosis following gamma-irradiation. Therefore, it appears that along with radiation, RU486 may be a beneficial agent in the treatment of hormone-reactive cervical tumors.     

Is an 192Ir permanent seed implant feasible for prostate brachytherapy?

PURPOSE: (125)I permanent seed brachytherapy for prostate cancer produces good clinical outcomes and limits radiation exposure to medical staff and patients' families. However, (125)I seeds cost thousands of dollars per implant. An encapsulated (192)Ir permanent seed possibly could cost less than 10 dollars. Could inexpensive permanent (192)Ir seeds be used for prostate implants? METHODS AND MATERIALS: We review the radiobiology of permanent implants, calculate the (192)Ir permanent seed air kerma strength (activity) required, simulate (125)I and (192)Ir seed implants and mixtures thereof, calculate exposure rates near simulated (192)Ir prostate patients, calculate potential radiation exposure to medical staff and family members, review patient release regulations, and analyze the potential cost benefits of using (192)Ir permanent seed implants. RESULTS: Low air kerma strength (<0.4 microGy m(2)/h/seed) [activity < 0.1-mCi/seed; <0.0558 mg Ra eq/seed] permanent (192)Ir seed implants yield more uniform prostate doses than (125)I seed implants and acceptable urethra, bladder, and rectal doses. The (192)Ir 73.83-day half-life allows mixing (192)Ir seeds and (125)I seeds. CONCLUSIONS: We believe medical staff could safely implant 40 microGy m(2)/h [10-mCi; 5.58 mg Ra eq] (192)Ir per case. Occupancy factors (1/8, 1/16) could acceptably limit families' exposures. Seed costs could be reduced markedly. With adequate protection of medical staff and proper instructions to patients post-implant, low air kerma strength (<0.4 microGy m(2)/h/seed) [activity <0.1-mCi/seed; <0.0558 mg Ra eq/seed] (192)Ir permanent seed implants are feasible in large patients, with mixed ((125)I, (92)Ir) seed implants feasible for modest size patients. Such implants could be useful in populous countries (China, India, Brazil) and for others who find (125)I seed implants too expensive to perform.     

Exposure to 1-bromopropane induces microglial changes and oxidative stress in the rat cerebellum

1-Bromopropane (1-BP), an alternative to ozone-depleting solvents, is reported to exhibit neurotoxicity and reproductive toxicity in animals and humans. However, the underlying mechanism of the toxicity remains elusive. This study was designed to identify the microglial changes and oxidative stress in the central nervous system (CNS) after 1-BP exposure. Four groups of Wistar-ST rats (n=12 each) were exposed to 0, 400, 800 and 1000ppm of 1-BP, 8h/day for 28 consecutive days. The cerebellum was dissected out in 9 rats of each group and subjected to biochemical analysis, while the brains of the remaining 3 rats were examined immunohistochemically. Exposure to 1-BP increased the levels of oxidative stress markers [thiobarbituric acid reactive substances (TBARS), protein carbonyl and reactive oxygen species (ROS)] in a dose-dependent manner. Likewise, there was also 1-BP dose-dependent increase in nitric oxide (NO) and dose-dependent decrease in protein concentrations in the cerebellum. Immunohistochemical studies showed 1-BP-induced increase in cd11b/c-positive microglia area in the white matter of the cerebellar hemispheres. The results showed that exposure to 1-BP induced morphological change in the microglia and oxidative stress, suggesting that these effects are part of the underlying neurotoxic mechanism of 1-BP in the CNS.     

Proteomic analysis of hippocampal proteins of F344 rats exposed to 1-bromopropane

1-Bromopropane (1-BP) is a compound used as an alternative to ozone-depleting solvents and is neurotoxic both in experimental animals and human. However, the molecular mechanisms of the neurotoxic effects of 1-BP are not well known. To identify the molecular mechanisms of 1-BP-induced neurotoxicity, we analyzed quantitatively changes in protein expression in the hippocampus of rats exposed to 1-BP. Male F344 rats were exposed to 1-BP at 0, 400, or 1000 ppm for 8 h/day for 1 or 4 weeks by inhalation. Two-dimensional difference in gel electrophoresis (2D-DIGE) combined with matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) were conducted to detect and identify protein modification. Changes in selected proteins were further confirmed by western blot. 2D-DIGE identified 26 proteins with consistently altered model (increase or decrease after both 1- and 4-week 1-BP exposures) and significant changes in their levels (p < 0.05; fold change ≥ ± 1.2) at least at one exposure level or more compared with the corresponding controls. Of these proteins, 19 were identified by MALDI-TOF-TOF/MS. Linear regression analysis of 1-BP exposure level identified 8 differentially expressed proteins altered in a dose-dependent manner both in 1- and 4-week exposure experiments. The identified proteins could be categorized into diverse functional classes such as nucleocytoplasmic transport, immunity and defense, energy metabolism, ubiquitination-proteasome pathway, neurotransmitter and purine metabolism. Overall, the results suggest that 1-BP-induced hippocampal damage involves oxidative stress, loss of ATP production, neurotransmitter dysfunction and inhibition of ubiquitination-proteasome system.     

Femoral cement pressurization in hip arthroplasty: a comparison of 3 systems

Cement pressurization is critical to achieving optimal results in cemented arthroplasty of the hip. An in vitro experiment using plastic femoral models (10 per group) was undertaken to measure the pressures developed by 3 cementing systems: the Howmedica Mark 1 (Stryker Howmedica, Limerick, Ireland) and DePuy Cemvac retrograde cementation systems (DePuy CMW, Blackpool, UK), and a novel antegrade system consisting of a 60-mL catheter-tipped syringe and a Miller proximal femoral seal (Zimmer Ltd, Swindon, UK). The mean pressure was higher for the syringe system (161.45 +/- 28.9 kPa) than the Mark 1 (103.51 +/- 22.0 kPa) or Cemvac (92.65 +/- 30.7 kPa) systems (P = .0001). In addition, fewer cement mantle defects were seen with the syringe system (1, interquartile range [IQR] 1-2) than the Mark 1 (3, IQR 2-4) or Cemvac (3, IQR 1-3) systems (P = .0256).