Comparative effects of organic and inorganic mercury on in vivo dopamine release in freely moving rats

The present study was carried out in order to compare the effects of administration of organic (methylmercury, MeHg) and inorganic (mercury chloride, HgCl 2 ) forms of mercury on in vivo dopamine (DA) release from rat striatum. Experiments were performed in conscious and freely moving female adult Sprague-Dawley (230-280 g) rats using brain microdialysis coupled to HPLC with electrochemical detection. Perfusion of different concentrations of MeHg or HgCl 2 (2 muL/min for 1 h, N = 5-7/group) into the striatum produced significant increases in the levels of DA. Infusion of 40 muM, 400 muM, or 4 mM MeHg increased DA levels to 907 ± 31, 2324 ± 156, and 9032 ± 70 percent of basal levels, respectively. The same concentrations of HgCl 2 increased DA levels to 1240 ± 66, 2500 ± 424, and 2658 ± 337 percent of basal levels, respectively. These increases were associated with significant decreases in levels of dihydroxyphenylacetic acid and homovallinic acid. Intrastriatal administration of MeHg induced a sharp concentration-dependent increase in DA levels with a peak 30 min after injection, whereas HgCl 2 induced a gradual, lower (for 4 mM) and delayed increase in DA levels (75 min after the beginning of perfusion). Comparing the neurochemical profile of the two mercury derivatives to induce increases in DA levels, we observed that the time-course of these increases induced by both mercurials was different and the effect produced by HgCl 2 was not concentration-dependent (the effect was the same for the concentrations of 400 muM and 4 mM HgCl 2 ). These results indicate that HgCl 2 produces increases in extracellular DA levels by a mechanism differing from that of MeHg.

Kinetic studies on the membrane form of intestinal alkaline phosphatase

We have purified different membrane and soluble forms of alkaline phosphatase from human placenta and bovine intestine. The enzymes will be used as markers in immunoconjugates and/or as model for membrane enzyme studies. The membrane formof alkaline phosphatase extracted from bovine intestine was purified on Q-Sepharose and on L-histidyldiazobenzylphosphonic acid-agarose columns to remove phosphodiesterase activity. The purified enzyme had a molecular mass of 61 kDa, Km of 1208 µM, and Vmax 240 µmol pNP/min when assayed in 1 M diethanolamine, 0.5 mM MgCl2 buffer, pH 9.8, containing 10 to 2250 µM of pNPP at 37§C. In the present investigation we studied the effect of salts and inositol derivatives on this enzyme activity, which was found to depend on 0.5 mM Mg2+, and to be fully inhibited by 1.2 mM Hg2+. Vanadate (0.5 mM) and Zn2+ (0.5 mM) reduced the Km value by 43 percent and 84 percent, respectively. Inositol (2 mM) and inositol-2-monophosphate (2 mM) reduced the activity by 23 percent and 17 percent. Inositol-1-monophosphate (0.5 mM) and cyclic-inositol-(1:2)-monophosphate (0.5 mM) enhanced their Km value by at least 30 percent compared to p-nitrophenylphosphate

Antimicrobial resistance and plasmid detection in strains of the Bacteroides fragilis group

Resistant populations of the Bacteroides fragilis group bacteria (two reference ones and two isolated from human and Callithrix penicillata marmoset) were obtained by the gradient plate technique, to clindamycin, penicillin G, metronidazole and mercuric chloride. All the four tested strains were originally susceptible to the four antimicrobial drugs at the breakpoint used in this study. MICs determination for the four cultures gave constant values for each antimicrobial, on the several steps by the gradient plate technique. The intestinal human B. fragilis strains showed three DNA bands, that could be representative of only two plasmids in the closed covalently circular (CCC) form with molecular weights of approximately 25 and 2.5 Md. The results do not permit an association between the presence of plasmid in the human strain with the susceptibility to the studied drugs. The four strains were beta-lactamase negative in the two methods used, and no particular chromosomal genetic resistance marker was demonstrated. The resistance (MIC) observed, after contact with penicillin G and mercuric chloride, were two-fold in the four tested strains.

Effects of mercury on the contractility of isolated rat cardiac muscle

The effects of increasing concentrations of mercury (Hg2+) chloride (1, 2.5, 5 and 10 microM) were studied on isometrically contracting papillary muscles from female rats (Wistar, EPM strain) weighing 150 to 180 g. Hg2+ promoted an increase of 12.7 +/- 2.2% in the developed force at 1 microM. At 2.5 microM, force values were similar to control, decreasing progressively as Hg2+ concentration increased to 5 (-13 +/- 6.4%) and 10 microM (-37 +/- 12.3%). Potentiated post-rest contractions (PRC) were also determined after 15-, 30- and 60-s pauses. There was a progressive reduction of the potentiated PRCs relative to their respective steady-state control contractions with increasing concentrations of HgCl2. Since in several tissues including myocardium Hg2+ inhibits the activity of Ca2+ and Na(+)-K(+)-ATPases the results described here suggest that Hg2+, at lower concentrations, could increase force by inhibiting Na(+)-K(+)-ATPase, while at higher concentrations Hg2+ would decrease relative PRC potentiation by inhibiting sarcoplasmic reticulum Ca(2+)-ATPase

Aspectos epidemiológicos de Staphilococcus isolados no Hospital das Clínicas UFMG: resistência ao cloreto mercúrico, conjugada ao antibiograma na identificaçäo de amostras hospitalares / Epidemiological aspects of Staphylococcus isolated in the Hospital das Clínicas UFMG: resistence to mercuric chloride, conjugated to the antibiogram in the identificatión of hospitalar samples

Um total de 113 amostras de S. aureus foram isoladas de pacientes, profissionais e do ambiente de um Hospital Geral em Belo Horizonte, Minas Gerais (Hospital das Clínicas da UFMG) entre junho de 1980 e novembro de 1981. As amostras foram estudadas quanto à sua sensibilidade ao íon mercúrio (Prova de MOORE, de 1960), conjugada aos modelos de susceptibilidade a drogas antibacterianas de BARBER & BURSTON (1955). Com base na correlaçäo destes testes, que permitem o reconhecimento de amostras potencialmente perigosas, parecem ocorrer neste hospital amostras de estafilococos bem adaptadas e facilmente disseminadas