Induction of maturation (meiosis) in Xenopus laevis oocytes by three organomercurials.
Three organomercurials, p-hydroxymercuribenzoate, p-hydroxymercuriphenylsulfonate, and mersalyl, induce maturation (meiosis) in a large percentage (20-100 percent) of Xenopus laevis oocytes. Maturation takes place even when the follicle cells which surround the oocytes have been withdrawn. Organomercurial- and progesterone-induced maturations have many features in common: they do not occur when the inducer is injected into the oocytes, they require the presence of Ca++ in the medium, they are inhibited by cycloheximide but not by actinomycin D. In both cases, the maturation producing factor and the pseudomaturation inducing factor are produced. Organomercurial-treated oocytes react normally to activating stimuli; their protein synthesis increases, but uptake of amino acids is strongly inhibited. Progesterone and p-hydroxymercuriphenyl-sulfonate act synergically in inducing maturation. The main difference between the two agents is that p-hydroxymercuriphenylsulfonate must act for several hours, whereas, short contact with progesterone is sufficient to induce maturation. (+info)
Fish as an indicator of eco-system contamination with mercury.
AIM: To compare the total and organic mercury content in sea-fish samples from Croatia, where fishing occurs in a closed part of the Mediterranean Sea, and from other countries fishing mostly in the oceans. METHOD: During 1997, we collected at the Zagreb fish market a total of 115 samples of fifteen kinds of fish including bathypelagic, pelagic and elasmobranch fish, caught in the wider coastal areas of Netherlands, Germany, Spain, Argentina, Belgium, and Croatia. Total mercury and organic methyl-mercury in the fish were determined at the laboratory for testing of food and other common use material at the Zagreb Institute of Public Health. Total mercury was determined by the method of atomic absorption spectrometry. Methyl-mercury was determined by the method of gas chromatography. The mean annual fish consumption in each country was used to calculate the mean weekly intake of mercury and methyl-mercury in each individual country relative to the recommended values. RESULTS: The mean content of total mercury and organic mercury in pooled samples was 111+100 ug/kg and 95+87 ug/kg (85.6%), respectively. The highest values were found in the fish from Croatia (170+124 ug/kg and 150+107 ug/kg; 88.2%, respectively). This concentration did not exceed the maximal allowed level of 500 ug/kg for total and 400 ug/kg for organic mercury in any of the samples examined. The highest values of total mercury (119+111 ug/kg) and organic mercury (103+96 ug/kg; 86.6%) were found in bathypelagic fish. According to the mean annual per capita fish consumption in each country, the mean weekly mercury intake was highest in Spain (49.8 ug) and lowest in Croatia (19.0 ug. CONCLUSION: At present conditions of mercury content and its mean annual consumption, dietary use of sea-fish can still be recommended, even from the seas with closed circulation, such as Adriatic. (+info)
Activation and inhibition of purified skeletal muscle calcium release channel by NO donors in single channel current recordings.
The actions of the nitric oxide (NO) donors 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3 methyl-1-triazine (NOC-7), S-nitrosoacetylcysteine (CySNO) and S-nitrosoglutathione (GSNO) on the purified calcium release channel (ryanodine receptor) of rabbit skeletal muscle were determined by single channel current recordings. In addition, the activation of the NO donor modulated calcium release channel by the sulfhydryl oxidizing organic mercurial compound 4-(chloromercuri)phenylsulfonic acid (4-CMPS) was investigated. NOC-7 (0.1 and 0.3 mM) and CySNO (0.4 and 0.8 mM) increased the open probability (P(o)) of the calcium release channel at activating calcium concentrations (20-100 microM Ca(2+)) by 60-100%, with no effect on the current amplitude; this activation was abolished by the specific sulfhydryl reducing agent DTT. High concentrations of CySNO (1.6-2 mM) decreased P(o). Activation by GSNO (1 mM) was observed in two thirds of the experiments, but 2 mM and 4 mM GSNO markedly reduced P(o) at activating Ca(2+) (20-100 microM). In contrast to 4-CMPS, NOC-7 or GSNO had no effect at subactivating free Ca(2+) (0.6 microM). 4-CMPS further increased the open probability of NOC-7- or CySNO-stimulated channels and reversed transiently the reduced open probability of CySNO or GSNO inhibited channels at activating free Ca(2+). High concentrations of GSNO did not prevent channel activation of 4-CMPS at subactivating free Ca(2+). The NOC-7-, CySNO- or GSNO-modified channels were completely blocked by ruthenium red. It is suggested that nitrosylation/oxidation of sulfhydryls by NO donors and oxidation of sulfhydryls by 4-CMPS affect different cysteine residues essential in the gating of the calcium release channel. (+info)
Mercury(II) binding to s4U in E. coli tRNA(Val).
The accessibility of the s(4)U base in native tRNA(Val) from E.coli was monitored by studying the binding of various mercurials. The relative binding order HgBr(2)[unk]HgCl(2)>>CH(3)HgOAc[unk]CH(3)HgCl[unk]PCMB parallels approximately the steric requirements of linear HgX(2) or RHgX compounds for S(N)2 displacement by sulfur, although other factors are operative. Para-chloromercuri-benzoate (PCMB) does not bind the thiolated nucleotide unless the tertiary structure of the tRNA is opened up by removal of Mg(2+) ions and heating to 40 degrees . Under these conditions, equilibrium dialysis measurements using (14)C-labeled PCMB showed one binding site (n = 0.93) with an association constant, K(1), of 9 x 10(4)M(-1). (+info)
Effect of organic mercurials and sulfhydryl compounds on the urease activity of Proteus: inhibition by urine and ascorbic acid.
Meralluride, mercaptomerin, ethacrynic acid, and penicillamine inhibited urease activity of Proteus mirabilis. The activity of the organic mercurials and ethacrynic acid was markedly inhibited by human and dog urine. Antiurease activity could not be detected in the urine of a human and a dog given meralluride by injection. Urine from patients receiving penicillamine also failed to inhibit urease activity. Ascorbic acid inhibited, whereas dehydroascorbic acid enhanced, the activity of the mercurials, but neither agent altered the inhibitory effect of urine. The lethal effect of meralluride against Proteus occurred at the same concentration at which urease activity was inhibited, but penicillamine inhibited the enzymatic activity without affecting viability of the organism. The data suggest that these sulfhydryl-reactive compounds will not be useful against Proteus infections of the urinary tract. (+info)
Environmental contamination by mercury in Iraq.
Following the outbreak of organomercury poisoning in Iraq, an investigation was carried out during the spring and summer of 1972 to evaluate environmental contamination by organomercury.Analyses were performed on fish of several species (not typical predators) and on a few specimens of aquatic birds (not fish-eating). Most fish samples contained concentrations in muscle ranging from 0.01 to 0.15 mg/kg. These concentrations are within the range found in tropical rivers. Higher figures, 0.3-0.5 mg/kg, were found downstream from a caustic soda plant south of Baghdad. A few cases of very high mercury concentrations (25-30 mg/kg) were reported from an area where fish kills had occurred. Aquatic birds (ducks and waders) contained low concentrations of mercury (900-2750 ng/g). Tail feathers of seed-eating birds were found to contain 13 500-21 000 ng/g of mercury, which is about 10 times higher than values reported from Ethiopia and within the range found in Sweden and Canada. Insect-eating birds contained 1850-5200 ng/g, which is thought to be slightly elevated. Extremely high concentrations of mercury were found in muscle tissue of dead seed-eating birds (15 000-40 000 ng/g), while feathers contained similar concentrations (9000-52 000 ng/g). These extremely high concentrations were found only in the vicinity of storehouses where treated seed was kept. No birds of prey could be caught and analysed. (+info)
Chemical type of mercury in patients in the outbreak of organomercury poisoning in Iraq.
Gas chromatography was employed to identify the mercurial compound involved in the Iraq outbreak of organomercury poisoning. Only methylmercury was detected in human blood, hair, and tissues. The quantity of methylmercury present correlates well with the quantity of organic mercury determined by selective atomic absorption. (+info)
Poisoning caused by the consumption of organomercury-dressed seed in Iraq.
In 1971-72, a large outbreak of poisoning caused by the consumption of seed dressed with organomercury compound occurred in Iraq. International assistance was requested by the Government of Iraq in investigating this outbreak. The results of the investigations to date were presented at the Conference on Intoxication due to Alkylmercury Treated Seed, held in Baghdad, Iraq on 9-13 November 1974. This paper summarizes the main findings and recommendations of the Conference. (+info)