Fungal products. Part XVII. Microbiological hydroxylation of gibberellin A9 and its methyl ester

Angiotensin II (A II) and analogues were tested for their ability to restore electrical and mechanical activity to cardiac muscle preparations in which the fast Na+ channels had been inactivated by partial depolarization (22-27 mM K+) or by tetrodotoxin (TTX). The partially depolarized or TTX-blocked preparations were chosen because under these conditions electrical and mechanical responses are primarily Ca2+ -dependent. In depolarized rabbit right atria, A II restored spontaneous mechanical and electrical activity (measured by both intracellular and extracellular recording techniques). The frequency of action potential discharge was concentration-dependent; the threshold concentration of A II was 10(-10) M, the ED50 was 8 X 10(-9) M, and the maximum effect was observed at 5 X 10(-8) M. In contrast, depolarized guinea pig atria were insensitive to A II, Sar1-angiotensin II, and des-Asp1-angiotensin II, even at concentrations as high as 10(-5) M. Rabbit papillary muscle (TTX-blocked), embryonic (18-day) chick heart (partially depolarized) and chick heart reaggregates (TTX-blocked) responded similarly to rabbit atria in that A II (9.6 X 10(-7) M) restored both electrical and mechanical activity. We found that in these preparations the action of A II was unaffected by propranolol (5.0 X 10(-6) M to 5.0 X 10(-5) M) but was blocked by Mn2+ (10(-3) M), D-600 (1 X 10(-7) g/ml) and the specific A II antagonists Sar1-Ala8-angiotensin II (P-113) (5.0 X 10(-5) M) and Sar1-Ile8-angiotensin II (5.28 X 10(-5) M). We conclude that the positive inotropic effect of A II on the myocardium is due to its ability to increase transmembrane ion movements in or through the cell membrane. The ability of Mn2+ and D-600 to block this effect suggests that this ion movement is via the so-called "slow channels."     

Corrosion resistance of D16 alloy depending on the salinity and meteorological parameters of coastal atmosphere

Results of two-year-long atmospheric corrosion tests of D16 alloy in representative coastal regions under natural field conditions and during artificial sedimentation of sea sal that corresponded to a salinity range of 0?C300 mg Cl^?/(m² day) are discussed.     

Characteristics of radiation porosity and structural phase state of reactor austenitic 07C–16Cr–19Ni–2Mo–2Mn–Ti–Si–V–P–B Steel after neutron irradiation at a temperature of 440–600°C to damaging doses of 36–94 dpa

The phase composition and the characteristics of vacancy voids in cold-worked steel 07C–16Cr–19Ni–2Mo–2Mn–Ti–Si–V–P–B (CW EK164-ID) after neutron irradiation at damaging doses of 36–94 dpa and temperatures of 440–600°C are investigated. In the entire range of damaging doses and temperatures, voids with different sizes are observed in the material. The maximum void size increases with irradiation temperature up to ~550°C, whereas their concentration decreases. At higher irradiation temperatures, almost no coarse voids are observed. The concentration of fine voids (to 10 nm in size) sharply increases with temperature from 440 to 480°C. Further increases in the temperature do not result in the noticeable concentration growth. In the irradiation temperature range of 440–515°C, second phases precipitate (G phase, γ’ phase, and complex fcc carbides). At higher irradiation temperatures, there are Laves-phase particles, fine second carbides of the MC type, and needle shape precipitates identified as phosphides in the material.     

Nano- and microparticles of iron with a modified surface and prospects for their application. Part II: Chemical and galvanic methods of treatment of iron particles

The possibility of the application of nano- and microparticles of iron as the carriers for palladium and platinum catalysts are shown. An increase in the efficiency of the catalytic activity by 2–5 times is found to be reached by way of microstirring of the reaction medium using magnetic fields with a variable direction of the intensity gradient. The possibility of manufacturing composite materials of iron-silver and iron-gold is also shown, which can be used in electric engineering. The techniques for producing catalytic and conducting materials based on the chemical depositing of certain metals on iron particles are described. Galvanic methods were shown to be used for the development of metal shells on the particles of magnetic current-conducting materials. The copper sliding contacts with microinclusions of graphite and iron manufactured using the proposed methods are characterized by a specific electric resistance of ρ = 2–3 × 10⁻⁶ Ohm cm (for comparison, the specific electric resistance of graphite sliding contacts is ρ = 800 × 10⁻⁶ Ohm cm) at a simultaneous increase in the wear resistance and, as a consequence, in the service life by 12–15 times. The possibility of the chemical passivation of the surface of nano- and microparticles of iron is shown to prevent their reacting with diluted nitric acid. Iron particles were studied to be used for obtaining contrasting X-ray anatomical specimens of the intraosteal blood-vascular system. A technological application of a magnetic field with a variable direction of the intensity gradient was proposed to increase the density of filling the capillary network with contrasting particles, which allows increasing the density of the filling of the intraosteal capillary network by up to 75% with respect to the volume.     

Marine Corrosion Tests of Galvanic Coatings for Ship Instruments. XI. Gold and Palladium Coatings on Brass

The corrosion peculiarities and the protective and decorative characteristics of gold and palladium coatings were investigated in containers simulating the casings for ship's equipment of watertight and splashproof types. The coatings (3 and 6 m thick) were applied to 62 brass specimens either directly or with a 12 m-thick silver sublayer (Ag12/Au3, Ag12/Pd 2, m). The specimens plated were tested by exposure for 14–20 years at coastal corrosion stations in cold (Murmansk), moderately humid (Vladivostok), and humid subtropical (Batumi) climates. The dezincification products of the brass substrate emerging through the pores of the coating form stains and salt films on its surface. Clogging the pores, the products become responsible for the blistering of the plate. The corrosion weight loss linearly correlate with the surface accumulation of chlorides; the thicker the coating, the smaller the damaged area of the substrate, but the deeper the corrosion centers. The technical service life of protective coatings is refined.     

Repeated dosing with the peroxisome proliferator clofibrate decreases the toxicity of model hepatotoxic agents in male mice

Pretreatment of mice with clofibrate (CFB) has been shown to protect against acetaminophen (APAP) hepatotoxicity. To determine if pretreatment with CFB prevents the toxicity of other model hepatotoxicants, male C57BL6J or CD-1 mice received 500 mg CFB/kg, i.p., daily for 10 days, and then were challenged with either 250 mg bromobenzene (BrB)/kg, 0.025 ml carbon tetrachloride (CCl4)/kg or 0.5 ml chloroform (CHCl3)/kg. Liver and kidney injury was assessed by plasma sorbitol dehydrogenase activity (SDH) and blood urea nitrogen (BUN), respectively and histopathology. Challenge with BrB significantly elevated plasma SDH activity in C57Bl6J mice. This was prevented in CFB pretreated mice receiving the same dose of BrB. Changes in BUN were not detected in either group of BrB treated mice. Similarly, pretreatment of male CD-1 mice with CFB significantly reduced CCl4-induced elevation in plasma SDH activity, with no BUN elevation detected in either group. CFB pretreatment also diminished elevation in plasma SDH activity produced by CHCl3 in CD-1 mice, while BUN was significantly elevated in both groups, indicating that CFB did not protect against CHCl3-induced nephrotoxicity. Histopathological examination of liver and kidney sections confirmed these results. This study shows that mice pretreated with CFB were protected from toxicity at 24 h after challenge with other model hepatotoxic agents besides APAP.