Characterization and identification of an iron-oxidizing,Leptospirillum-like bacterium,present in the high sulfate leaching solution of a commercial bioleaching plant

Most copper bioleaching plants operate with a high concentration of sulfate salts, caused by the continuous addition of sulfuric acid and the recycling of the leaching solution. Since the bacteria involved in bioleaching have been generally isolated at low sulfate concentrations, the bacterial population present in the high-sulfate (150 gl(-1)) leaching solution, employed in a copper production plant, was investigated. The iron-oxidizing bacteria able to grow in the leaching solution were enriched by several batch cultivations and, after serial dilution, an abundant bacterial strain was isolated. This strain, called LA, exhibited a relatively constant rate of iron-oxidation in media containing sulfate ions at concentrations ranging from 10 to 150 gl(-1). Culture collection strains of Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans showed limited abilities to grow at sulfate ion concentrations higher than 70 gl(-1). In spite of its tolerance to high sulfate concentrations, strain LA was as sensitive to NaCl as A. ferrooxidans. Comparative sequence analysis of the 16S rRNA gene of strain LA indicated that it is phylogenetically related to strains described as Leptospirillum ferrooxidans. Bacterial community DNA restriction patterns of 16S rRNA genes suggested that strain LA was a minor component of the bacterial population present in leaching solution, but is abundant in ore leached with this solution.     

Mechanisms of polyploidization of mouse cardiomyocytes

Most ventricular cardiomyocytes in mice aged 5–6 days are polyploid cells. By this time 60% of the cardiomyocytes have become binuclear and a further 10% have become mononuclear polyploid cells. Binuclear cardiomyocytes are formed as a result of acytokinetic mitosis, mononuclear tetraploid cells as a result of termination of mitosis in the initial phases.Laboratory of Cytology, N. K. Kol'tsov Institute of Developmental Biology, Academy of Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 89, No. 2, pp. 219–222, February, 1980.     

The involvement of glutamatergic transmission in the mechanism of movement disorders induced by reversive rotation of white mice

The ability of the selective non-competitive NMDA receptor blocker MK-801 and a series of new glutamate antagonists—the adamantane derivatives IEM-1754 and IEM-1857 and phencyclidine (IEM-1925)—to prevent movement disorders induced by reversive rotation in mice was studied. I.p. MK-801 at a dose of 0.15 ml and IEM-1754 at a dose of 5.0 mg/kg prevented the development of akinesia in response to reversive rotation, as effectively as scopolamine, a known agent which provides effective prophylaxis for movement diseases. IEM-1857, the quaternary analog of IEM-1754, was not effective. IEM-1925 significantly increased the responses of mice to reversive rotation, possibly because of its high activity in relation to other subtypes of glutamate receptors. These data provide evidence for the involvement of glutamatergic transmission in the mechanism of movement disorders of vestibular origin. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 85, No. 4, pp. 497–501, May, 1999.     

Certain characteristics of myocardial contractility of isovolumic dog heart at randomly variable heart rhythm

Summary The relationship heart rate-left ventricular pressure was investigated in the isolated canine heart perfused with constant pressure at different preloads. Rhythmical stimulation was performed with constant stimulus interval duration and with stimulus intervals randomly changed near the average value (150–200 stimuli in series).Correlation and dispersion function analysis show that rhythm dispersion had a negative inotropic effect which was independent of the preload of the ventricle in the range of 120–180 beat/min, but this dependence occurred with low rates of stimulation.This method is proposed for the assessment of contractility under conditions of heart rate variations (physiological and pathological arrhythmias).