Berberine has been shown to have antidiabetic properties, although its mode of action is not known. Here, we have investigated the metabolic effects of berberine in two animal models of insulin resistance and in insulin-responsive cell lines. Berberine reduced body weight and caused a significant improvement in glucose tolerance without altering food intake in db/db mice. Similarly, berberine reduced body weight and plasma triglycerides and improved insulin action in high-fat-fed Wistar rats. Berberine downregulated the expression of genes involved in lipogenesis and upregulated those involved in energy expenditure in adipose tissue and muscle. Berberine treatment resulted in increased AMP-activated protein kinase (AMPK) activity in 3T3-L1 adipocytes and L6 myotubes, increased GLUT4 translocation in L6 cells in a phosphatidylinositol 3 kinase-independent manner, and reduced lipid accumulation in 3T3-L1 adipocytes. These findings suggest that berberine displays beneficial effects in the treatment of diabetes and obesity at least in part via stimulation of AMPK activity.

The open inflation model recently proposed by Hawking and Turok is investigated in scalar-tensor gravity context. If the dilaton-like field has no potential, the instanton of our model is singular but has a finite action. The GibbonsHawking surface term vanishes and hence, can not be used to make Ω 0 nonzero.To obtain a successful open inflation one should introduce other matter fields or a potential for the dilaton-like fields.PACS numbers: 98.80.Cq 1

We construct the mass spectrum of primordial black holes ͑PBH's͒ using the Press-Schechter formalism and study the contribution of PBH's to the density of the universe, ⍀ BH , when the power spectrum of the density fluctuation is a simple power-law spectrum. From the condition ⍀ BH Ͻ1, the constraints on the spectral index n are found for both cases of possible end states of black hole evaporation, one in which black holes evaporate completely without relics and the other in which black hole evaporation ends with relics with mass of the order of M Pl . With the normalization of the fluctuation amplitude to COBE's quadrupole anisotropy measurement, we find that the upper limit of n is somewhat largely deviated from the Harrison-Zel'dovich spectrum. ͓S0556-2821͑96͒05122-3͔PACS number͑s͒: 97.60. Lf, 98.70.Vc, 98.80.Cq

We calculate the flux of ␥ rays emitted from primordial black holes ͑PBHs͒ which are formed by a ''blue'' power-law spectrum of density fluctuations in the early universe. Gamma-ray emission from such PBHs may contribute significantly to the observed extragalactic diffuse ␥-ray background ͑DGB͒. Using the observed DGB flux from the imaging Compton Telescope ͑COMPTEL͒ and the Energetic Gamma Ray Experiment Telescope ͑EGRET͒ as the upper limit of ␥-ray flux from PBHs, we derive the upper limit on the spectral index n of the density fluctuations. The range of initial PBH masses which can contribute to the DGB is 2 ϫ10 13 gϪ5ϫ10 14 g, corresponding to a cosmic reheating temperature of 7ϫ10 7 GeVϪ4ϫ10 8 GeV. In this range, we find the upper limit to be nՇ1.23Ϫ1.25. This limit is stronger than those derived from the energy density in PBHs or PBH relics and matches the value of n required to explain the cosmic microwave background anisotropy. ͓S0556-2821͑99͒05804-X͔ PACS number͑s͒: 95.85.Pw, 97.60.Lf, 98.80.Es

We consider 1 + 4 dimensional black string solutions which are invariant under translation along the fifth direction. The solutions are characterized by the two parameters, mass and tension, of the source. The Gregory-Laflamme solution is shown to be characterized by the tension whose magnitude is one half of the mass per unit length of the source. The general black string solution with arbitrary tension is presented and its properties are discussed. *