The effect of UV-B radiation on Bufo arenarum embryos survival and superoxide dismutase activity.

The exposure of Bufo arenarum embryos to 300-310 nm UV-B at a dose of 4,104 Joule/m(2) resulted in 100% lethality within 24 hr while 820 Joule/m(2) was the NOEC value for short-term chronic (10 days) exposure. The dose response curves show that lethal effects are proportional with the dose and achieve its highest value within 48 hr post exposure. The superoxide dismutase (SOD) activity in amphibian embryos for sublethal UV-B exposures was evaluated by means of UV-B treatments with 273 (A), 820(B), 1368(C) and 1915(D) Joule/m(2) at 2 and 5 hours post irradiation. The SOD activity in units/mg protein in A, B, C and D at 2 hr after treatments were 80.72 +/- 14.29, 74.5 +/- 13.19, 39.5 +/- 6.99 and 10.7 +/- 1.89 respectively while for control embryos it was 10.88 +/- 1.31. At 5 hr after treatments the SOD values were similar to those found in control embryos. The results confirm the high susceptibility of amphibian embryos to UV-B and point out that the SOD activity is enhanced by low doses of UV-B irradiation achieving significantly higher values than in control embryos at 2 hr post exposure.

Metallothionein induction and cadmium uptake in Bufo arenarum embryos following an acclimation protocol.

Bufo arenarum embryos at the end of their embryonic development were acclimated to cadmium (Cd) by means of a 10-day treatment protocol. Embryos were processed for metallothionein (Mt) isolation and Cd and zinc (Zn) contents were measured. The results showed that: (1) the uptake of Cd in the experimental embryos was 7 microg/g embryo (wet weight) representing a bioaccumulation of Cd 255 times higher than in the maintaining medium; (2) a major Mt-like fraction was Cd-induced 7.8 times that in control embryos; two other protein fractions also bound Cd and Zn but were induced by Cd only about 2 and 1.4 times; (3) the Zn concentration was about 44 microg Zn/g embryo (wet weight) and did not change significantly (p>0.01) in the experimental embryos with respect to controls, but in acclimated embryos the essential metal was released from the Mts. The enhanced Mt synthesis and release of Zn from the native Mts are discussed in relation to the acclimation phenomenon.

Total homocysteine levels in plasma: high-performance liquid chromatographic determination with electrochemical detection and glassy carbon electrode.

An isocratic high-performance liquid chromatography with electrochemical detection (HPLC-ED) method for the determination of total plasma homocysteine [H(e)] has been developed. The electrochemical detection is performed using a glassy-carbon electrode that is not specific for thiol groups. We have tried to solve the problem of specificity focusing our work on chromatographic resolution and have obtained good results without coelution of other thiol compounds or any substances mentioned as common interferences for carbon electrode methods: uric acid, ascorbic acid and salicylates. Thirty samples a day can be assayed for total homocysteine with a lower limit of detection of 2 pmol, and a limit of quantification of 1.0 micromol/l, with a coefficient of variation (C.V.) <20%. For a concentration of total plasma homocysteine of 9.36 micromol/l, the intra- and inter-assay C.V.s were of 3.86% and 5.55% respectively. The analytical recovery achieved in the preparation of the samples ranged from 85.0% to 98.3% and the electrochemical response was linear up to 100 micromol/l.

Homocisteína plasmática: factor de riesgo independiente de afecciones vasculares oclusivas / Plasma homocysteine: independent risk factor for occlusive vascular disease

La determinación de los niveles de homocisteína plasmática total se ha convertido en un estudio de gran utilidad debido a que los valores moderadamente elevados de homocisteína circulantes pueden causar aterosclerosis y obstrucción de las arterias coronarias. Se sabe que son varios los factores que causan el aumento de homocisteína plasmática; éstos incluyen afecciones metabólicas hereditarias, estado nutricional y el tratamiento con ciertos fármacos. Los posibles mecanismos por los cuales los niveles elevados de homocisteína causan afecciones vasculares incluyen efectos sobre las plaquetas, los factores de coagulación y el endotelio. Las lesiones ateroscleróticas y la trombosis relacionadas con la hiperhomocisteinemia podrían ser prevenidas con una dieta rica en vitaminas, aunque esto hasta el presente no ha sido comprobado

Metallothioneins and cadmium uptake by the liver in Bufo arenarum.

Bufo arenarum females were treated daily with 0.5 mg Cd kg(-1) during 10 days to evaluate the uptake of this heavy metal and the induction of metallothionein synthesis in the liver. The liver incorporated 26% of the Cd administered, about 6.5 times higher than the average uptake of the other tissues of B. arenarum. Three protein fractions from the B. arenarum liver bound Cd, and were induced by this xenobiotic up to approx. 24 times above the basal level of these proteins.

GnRH molecular variants in the brain and pituitary gland of pejerrey, Odontesthes bonariensis (Atheriniformes). Immunological and chromatographic evidence for the presence of a novel molecular variant.

Gonadotropin-releasing hormone (GnRH) molecular variants in the brain and pituitary gland of pejerrey, Odontesthes bonariensis (Atheriniformes), were characterized by gradient reverse phase high performance liquid chromatography (RP-HPLC). Eluted fractions were tested in radioimmunoassays with different antisera. The results show that the brain extract contains three forms of GnRH: one is immunologically and chromatographically similar to cIIGnRH (chicken II), and another is similar to sGnRH (salmon). A third GnRH appears to be chromatographic and immunologically different from the nine other known forms of the vertebrate hormone. This is the only variant present in the pituitary gland.

Rapid separation of gonadotropin-releasing hormone molecular forms by isocratic high-performance liquid chromatography on an ion-exchange column.

The purpose of the present work was to develop a chromatographic system for the separation of five molecular forms of the gonadotropin-releasing hormone (GnRH); mammalian GnRH (mGnRH) (LHRH), salmon GnRH (sGnRH), chicken I GnRH (cIGnRH), chicken II GnRH (cIIGnRH) and lamprey GnRH I (IGnRH-I). By using an ion-exchange HPLC column and isocratic elution, it was possible to separate properly the five peptides in approximately 20 min. The utility of the system in determining the GnRHs forms present in the brain of two species of vertebrates was examined.

Immunoreactive GnRH suggesting a third form of GnRH in addition to cIIGnRH and sGnRH in the brain and pituitary gland of Prochilodus lineatus (Characiformes).

Molecular variants of GnRH (gonadotropin-releasing hormone) in brain and pituitary extracts of the South American characiforme Prochilodus lineatus were studied using a combination of reverse-phase high-performance liquid chromatography and radioimmunoassay with different antisera. In brain extracts our study revealed that this fish has at least two different types of GnRH: cIIGnRH (chicken II) and sGnRH (salmon), and possibly a third variant of this molecule. In pituitary extracts we could find only two immunoreactive peaks corresponding to sGnRH and the possible third form.

Further evidence for endogenous hypothalamic serotonergic neurons involved in the cimetidine-induced prolactin release in the rat.

The aim of the present work was to further explore the possible relationship between the prolactin-releasing effect of cimetidine and hypothalamic serotonergic neurons controlling pituitary hormone secretion. In a first approach, the prolactin-releasing effect of the drug was determined in adult male rats with total deafferentation of the hypothalamus. Cimetidine injection (60 mg/kg) produced a significant rise in prolactin, but not in luteinizing hormone (LH), both in deafferented rat and in sham-operated controls; by 15 min there was a 5-6 fold increase in prolactin titers. Methysergide, a serotonin receptor blocker, used in a dose (2.5 mg/kg), route (i.p.) and time (50 min earlier) which did not modify the hormone basal level in rats with total deafferentation of the hypothalamus, was able to prevent completely the prolactin release evoked by cimetidine. The same preventive effect on prolactin release was observed with the serotonin receptor blocker ketanserin (5 mg/kg, i.p., 30 min earlier). It is concluded that the prolactin-releasing effect of cimetidine is located at a hypothalamic level related to serotonergic neurons.

Baclofen, a GABA derivative, inhibits stress-induced prolactin release in the rat.

The effect of baclofen, beta-(4-chlorophenyl)GABA, on prolactin secretion was investigated in rats under several experimental conditions. In adult male rats subjected either to immuobilization, ether, swimming or cold stress there was a rapid increase of serum prolactin levels; acute pretreatment with baclofen, 10 mg/kg i.p. inhibited the hormone response to all these stresses. The same blocking effect of the drug was observed in prepubertal male and female rats and in adult gonadectomized animals. In basal conditions, i.e. in undisturbed male rats, baclofen did not change the hormone titers significantly. Taken together our results indicate that baclofen blocks prolactin release when release of the hormone is dynamically stimulated by stress and this effect is relatively independent of the endocrine status of the rat.