M. G. Vendrell

c-fos and ornithine decarboxylase gene expression in brain as early markers of neurotoxicity

An increase of proto-oncogene c-fos expression in cerebral cortex of rats treated with subconvulsant doses of the pesticide organochlorine lindane (gamma-hexachlorocyclohexane) has been detected using Northern blots. Immunohistochemical studies show that Fos protein was already increased in neuronal nuclei 3 h after treatment. The administration of the benzodiazepine diazepam prior to lindane totally blocked the activation of this proto-oncogene expression. Parallel to this increased expression of c-fos an activation of the ornithine decarboxylase (ODC) gene and enzyme was also observed. High levels of ODC mRNA and increased enzyme activity in cortex were found in rats following lindane treatment. These changes were attenuated by prior treatment of animals with diazepam. The co-induction of c-fos and ODC suggests a potential link between the ODC/polyamine system and the short-acting proto-oncogenes in stimulus-transcription coupling events.

Lindane-induced convulsions in NMRI and OF1 mice : antagonism with (+)MK-801 and voltage-dependent calcium channel blockers

The convulsant profile of lindane was investigated in OF1 and NMRI mice lines in relation to other convulsants acting at the GABAA and NMDA receptor complexes. Thus, a specific GABA-gated chloride channel blocker, PTX, a GABAA receptor antagonist, PTZ, and an excitatory amino acid receptor agonist, NMDA, were used. Antagonism of the convulsant effects of each of these drugs was investigated with (+)MK-801, a blocker of the NMDA-operated cation channel, and with nifedipine, a voltage-dependent calcium channel antagonist. While no differences in potency for PTX or PTZ to induce seizures were observed between OF1 and NMRI mice, lindane was approximately 80 and 90% more potent in its ability to induce seizures and lethality, respectively, in OF1 than in NMRI mice. Brain lindane concentrations at the moment of convulsion, measured after ED100 doses of lindane (400 and 200 mg/kg for NMRI and OF1 mice, respectively), did not differ between OF1 and NMRI mice, suggesting that the different potency of lindane between these mouse lines is a consequence of pharmacokinetic factors. Furthermore, (+)MK-801 antagonized seizures induced by either lindane, PTX or PTZ with similar potencies in both mouse lines. These results, coupled with the different pharmacokinetics of lindane in OF1 and NMRI mice, suggest that the distinct effects of lindane in these mice are not mediated by different activities at either NMDA or GABAA receptor complexes. Nonetheless, nifedipine antagonized lindane-induced seizures with a three-fold higher potency in NMRI than in OF1 mice. In contrast, nifedipine failed to antagonize PTX and PTZ convulsions in both OF1 and NMRI mice. These results suggest that besides the GABAA receptor complex other mechanisms related to calcium mobilization may be involved in the convulsant action of lindane.

Behavioral and monoaminergic changes after lindane exposure in developing rats

The effects of lindane on behavior and central monoaminergic systems were studied in rat pups at 15 days of postnatal age. Pups were previously given nonconvulsant lindane PO doses, either a single 20 mg/kg or 7-day repeated 10 mg/kg doses. Both treatment schedules improved the passive avoidance acquisition but only the acute administration prolonged the step-through latency. Acute lindane decreased the motor activity, whereas the repeated dosing increased it. Increases of the ratio 5-HIAA/serotonin in several brain regions and of the ratio DOPAC/dopamine in the mesencephalon after a single dose of lindane suggest an enhanced monoaminergic turnover. In contrast, repeated lindane doses decreased monoamine/metabolite ratios excluding the striatum, where an increase of DOPAC/dopamine ratio correlates with the higher motor activity of these animals. It is postulated that both the imbalance of the central monoaminergic systems and the lindane-induced GABAergic blockade may be the basis of the behavioral alterations.

Presence of calmodulin and calmodulin-binding proteins in the nuclei of brain cells.

The nuclear calmodulin levels have been measured in rat neurons and glial cells. The values are 1.0 and 1.1 γg/ mg of protein, respectively. These levels are about threefold higher than those in the nuclei of rat liver cells. We have also investigated the presence of several calmodulin‐binding proteins in the nuclei of both brain cellular types. As similarly observed in the nuclei of liver cells, we detected the presence of a‐spectrin and a 62‐kDa calmodulin‐binding protein (p62) in the nuclei of neurons and glial cells by irnmunoblotting and immunocytochemical methods. Both proteins are enriched in the purified nuclear matrix samples from both cellular types. In contrast to that occurring in rat hepatocytes, we have not been able to detect, by irnmunoblotting methods, caldesmon in the nuclear matrices of neurons and glial cells. The immunocytochemical studies suggest, however, that caldesmon can be present in the nuclei but in a fraction distinct from the nuclear matrices.

Seismic structure of the Central Tyrrhenian basin: Geophysical constraints on the nature of the main crustal domains

In this work we investigate the crustal and tectonic structures of the Central Tyrrhenian back-arc basin combining refraction and wide-angle reflection seismic (WAS), gravity, and multichannel seismic (MCS) reflection data, acquired during the MEDOC (MEDiterraneo OCcidental)-2010 survey along a transect crossing the entire basin from Sardinia to Campania at 40°N. The results presented include a ~450 km long 2-D P wave velocity model, obtained by the traveltime inversion of the WAS data, a coincident density model, and a MCS poststack time-migrated profile. We interpret three basement domains with different petrological affinity along the transect based on the comparison of velocity and velocity-derived density models with existing compilations for continental crust, oceanic crust, and exhumed mantle. The first domain includes the continental crust of Sardinia and the conjugate Campania margin. In the Sardinia margin, extension has thinned the crust from ~20 km under the coastline to ~13 km ~60 km seaward. Similarly, the Campania margin is also affected by strong extensional deformation. The second domain, under the Cornaglia Terrace and its conjugate Campania Terrace, appears to be oceanic in nature. However, it shows differences with respect to the reference Atlantic oceanic crust and agrees with that generated in back-arc oceanic settings. The velocities-depth relationships and lack of Moho reflections in seismic records of the third domain (i.e., the Magnaghi and Vavilov basins) support a basement fundamentally made of mantle rocks. The large seamounts of the third domain (e.g., Vavilov) are underlain by 10–20 km wide, relatively low-velocity anomalies interpreted as magmatic bodies locally intruding the mantle.

Nuclear calmodulin-binding proteins in rat neurons.

Abstract: By using a 125I‐calmodulin overlay assay, three major high‐affinity calmodulin‐binding proteins, showing apparent molecular masses of 135, 60, and 50 kDa, have been detected in purified nuclear fractions isolated from rat neurons. It has been shown that after extraction of the nuclei with nucleases and high salt, all these proteins remain strongly associated with the nuclear matrix. The 60‐ and 50‐kDa proteins have been previously identified as subunits of the calmodulin‐dependent protein kinase II. We report here the immunoblot identification of the 135‐kDa cal modulin‐binding protein as myosin light chain kinase. We also show that the calmodulin‐dependent protein phosphatase calcineurin is present in the neuronal nuclei and associated with the nuclear matrix. The nuclear localization of both calcineurin and myosin light chain kinase has been confirmed by immunocytochemical studies.

Proto-oncogene c-fos induction in thiamine-deficient encephalopathy : protective effects of nicardipine on pyrithiamine-induced lesions

Treatment of rats with the central thiamine antagonist, pyrithiamine, results in severe neurological symptoms such as ataxia and convulsions. Induction of proto-oncogene c-fos expression, often related to seizure activity, has been detected in the brains of thiamine-deficient rats by means of Northern blot analysis and in situ hybridization. Region-selective increases of lactate observed following thiamine deficiency development are largely coincident with histologically vulnerable regions. When thiamine-deficient rats were treated with the calcium channel blocker, nicardipine, lesions associated with thiamine deficiency did not appear and there was no induction of c-fos mRNA expression. This suggests a neurocytoprotective role of nicardipine to neuronal cell damage in thiamine-deficient encephalopathy.

c‐fos Expression as a Model for Studying the Action of Hexachlorocyclohexane Isomers in the CNS

Abstract: The induction of protooncogene c‐fos in the CNS after administration of several convulsants has been studied. The organochlorine insecticide γ‐hexachlorocyclohexane (γ‐HCH, lindane) has been shown to induce c‐fos expression in different brain areas. Pentylenetetrazole and picrotoxin, a known γ‐aminobutyric acid‐receptor antagonist, have also been considered. The administration of two nonconvulsant isomers of γ‐HCH, α‐HCH, and δ‐HCH, before the mentioned toxicants, affects the protooncogene expression in different ways. The differential pattern of expression displayed by c‐fos after these treatments suggests the presence of diverse mechanisms of action for the compounds studied.

Compressional tectonic inversion of the Algero-Balearic basin: Latemost Miocene to present oblique convergence at the Palomares margin (Western Mediterranean)

Interpretation of new multichannel seismic reflection profiles indicates that the Palomares margin was formed by crustal-scale extension and coeval magmatic accretion during middle to late Miocene opening of the Algero-Balearic basin. The margin formed at the transition between thinned continental crust intruded by arc volcanism and back-arc oceanic crust. Deformation produced during the later positive inversion of the margin offshore and onshore is partitioned between ~N50°E striking reverse faults and associated folds like the Sierra Cabrera and Abubacer anticlines and N10–20°E sinistral strike-slip faults like Palomares and Terreros faults. Parametric subbottom profiles and multibeam bathymetry offshore, structural analysis, available GPS geodetic displacement data, and earthquake focal mechanisms jointly indicate that tectonic inversion of the Palomares margin is currently active. The Palomares margin shows a structural pattern comparable to the north Maghrebian margins where Africa-Eurasia plate convergence is accommodated by NE-SW reverse faults, NNW-SSE sinistral faults, and WNW-ESE dextral ones. Contractive structures at this margin contribute to the general inversion of the Western Mediterranean since ~7 Ma, coeval to inversion at the Algerian margin. Shortening at the Alboran ridge and Al-Idrisi faults occurred later, since 5 Ma, indicating a westward propagation of the compressional inversion of the Western Mediterranean.