Shoot and root biomass production in semi-arid shrublands exposed to long-term experimental N input.

Anthropogenic nitrogen (N) deposition has affected the primary production of terrestrial ecosystems worldwide; however, ecosystem responses often vary over time because of transient responses, interactions between N, precipitation, and/or other nutrients, and changes in plant species composition. Here we report N-induced changes in above- and below-ground standing crop and production over an 11-year period for two semi-arid shrublands, chaparral and coastal sage scrub (CSS), of Southern California. Shrubs were exposed to 50 kgN ha-1 in the fall of each year to simulate the accumulation of dry N deposition, and shoot and root biomass and leaf area index (LAI) were measured every 3 months to assess how biomass production responded to chronic, dry N inputs. N inputs significantly altered above- and below-ground standing crop, production, and LAI; however, N impacts varied over time. For chaparral, N inputs initially increased root production but suppressed shoot production; however, over time biomass partitioning reversed and plants exposed to N had significantly more shoot biomass. In CSS, N inputs caused aboveground production to increase only during wet years, and this interaction between added N and precipitation was due in part to a highly flexible growth response of CSS shrubs to increases in N and water availability and to a shift from slower-growing native shrubs to fast-growing introduced annuals. Together, these results indicate that long-term N inputs will lead to complex, spatially and temporally variable growth responses for these, and similar, Mediterranean-type shrublands.

Neuroprotective effects of gabaergic phenols correlated with their pharmacological and antioxidant properties.

AIMS: Various investigations have demonstrated the protective capacity of general anesthetics as neuroprotective agents. The effects of propofol against ischemia are known to reside in its antioxidant properties and its GABAergic activity. Other aromatic alcohols have also been reported as able to protect neurons against oxidative damage. The aim of this work is to evaluate the potential neuroprotective effect of some phenols, structurally analogues of propofol, with proven GABAergic activity. These phenols include the naturally occurring compounds thymol, carvacrol and eugenol, the synthetic product chlorothymol, and the most widely used intravenous anesthetic, propofol, as a reference compound. MATERIALS AND METHODS: Taking primary cultures of cortical neurons as a suitable model to evaluate cellular protection against oxidative damage, we developed an injury model to test potential neuroprotective activity. The intracellular hydroperoxides were also determined. KEY FINDINGS: The results showed that no compound decreased cell viability at concentrations where they were active on the GABAA receptor. In neuroprotection tests, some phenols and Vit E showed a partial protective effect against the oxidative injury. These compounds induced a clear tendency to reduce H2O2 damage, comparing production of hydroperoxides, although these last changes were statistically non-significant. SIGNIFICANCE: Testing the intracellular oxidation levels suggests that this partial protection exerted by propofol, thymol and chlorothymol may be mediated in some way by their antioxidant activities. However, this neuroprotection is not completely correlated with the antioxidant capacity, but it approaches their relative pharmacological potency, which could be interpreted as a final effect that would involve both activities.

Effects of Insecticidal Ketones Present in Mint Plants on GABAA Receptor from Mammalian Neurons.

BACKGROUND: The genus Mentha, an important member of the Lamiaceae family, is represented by many species commonly known as mint. The insecticidal activity of Mentha oil and its main components has been tested and established against various insects/pests. Among these, the ketone monoterpenes that are most common in different Mentha species demonstrated insect toxicity, with pulegone being the most active, followed by carvone and menthone. Considering that the GABAA receptor (GABAA-R) is one of the main insecticide targets on neurons, and that pulegone would modulate the insect GABA system, it may be expected that the insecticidal properties of Mentha ketones are mediated by their interaction with this receptor. OBJECTIVE: In order to discern the pharmacological actions of these products when used as insecticides on mammalian organisms, we evaluated the pharmacologic activity of ketones, commonly present in Mentha plants, on native GABAA-R from rats. MATERIALS AND METHODS: Determination of ketones effects on allosterically enhanced benzodiazepine binding, using primary cultures of cortical neurons, which express functional receptors and MTT assay to evaluate their cell toxicity. RESULTS: Our results seem to indicate that ketone components of Mentha, with proven repellent or insecticide activity, were able to behave as GABAA-R negative allosteric modulators in murine cells and consequently could exhibit convulsant activity in mammalians. Only pulegone at the highest assayed concentration (2 mM) showed a significant reduction in cell viability after exposure for 24 hr. CONCLUSION: The present results strongly suggest that the ketone components of Mentha are able to exhibit convulsant activity in mammalian organisms, but functional assays and in vivo experiments would be necessary to corroborate this proposed action. SUMMARY: The pharmacological activity of insecticide ketones, commonly present in Mentha plants, was evaluated on native GABAA receptor from mammalian neurons.All studied compounds: pulegone, menthone and dihydrocarvone, were able to behave as negative allosteric modulators and could exhibit convulsant activity in mammalian organisms.Citotoxicity assays demonstrated that only pulegone affected the cell viability. Abbreviations used: GABA: gamma aminobutyric acid, GABAA-R: GABAA receptor, MTT: 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazam, DMEM: Dulbecco's modified minimum essential mèdium, [3H]TBOB: [3H] t-Butylbicycloorthobenzoate.

Inhibitory effects of carvone isomers on the GABAA receptor in primary cultures of rat cortical neurons.

Carvone is a natural terpene which can be purified as R-(-) or S-(+) enantiomers. There are many reports about its antibacterial, antifungal, and insecticide activities, and also of some effects on the nervous system, where both enantiomers showed different potencies. Considering that the GABA(A) receptor is a major insecticide target, we studied the pharmacological activity of both carvone enantiomers, and of thujone as a reference compound acting on the receptor, on native GABA(A) by determining their effects on benzodiazepine recognition sites using primary neuronal cultures. Both isomers were able to inhibit the GABA-induced stimulation of [(3)H]flunitrazepam binding, suggesting their interaction with the GABA(A) receptor as negative allosteric modulators. Their activity was comparable to that described for thujone in the present article, with the R-(-)-carvone being the more similar and potent stereoisomer. The different configuration of the isopropenyl group in position 5 thus seems to be significant for receptor interaction and the bicycle structure not to be critical for receptor recognition. The concentrations necessary to induce negative modulation of the receptor were not cytotoxic in a murine neuron culture system. These results confirm that, at least partially, the reported insecticidal activity of carvones may be explained by their interaction with the GABA(A) receptor at its noncompetitive blocker site.

Comparative antioxidant properties of some GABAergic phenols and related compounds, determined for homogeneous and membrane systems.

Some phenols, like propofol, thymol and related compounds, have been shown to act on the GABA(A) receptor. Several compounds with GABAergic activity have displayed neuroprotective effects attributed mainly to the potentiation of GABA(A)-mediated inhibition of synaptic transmission. It has also been found that compounds containing a phenolic OH group can scavenge reactive oxygen species, as in the case of propofol, among others. Thus, the neuroprotective action mechanism of GABAergic phenols would involve both effects, their pharmacological activity on GABA(A) and their intrinsic antioxidant ability. In this context, the study of the antioxidant properties of phenolic compounds included in the present work will enable these capacities to be correlated with their eventual pharmacological activities. The assays chosen in this study included determination of antioxidant ability in homogeneous isotropic systems (DPPH reduction, FRAP and hydrogen peroxide scavenging) and in heterogeneous membrane systems (inhibition of lipid peroxidation of phospholipid SUVs). The comparative evaluation of the results showed some differences between the relative order of antioxidant potency among all assayed compounds determined by using both types of systems. This analysis supports the conclusion that the antioxidant values obtained in homogeneous non-membrane systems, for phenols or other lipophilic compounds, should be revised according to their capacity of interaction with membranes (i.e. Log P in membrane-buffer system) in order to obtain antioxidant potency values more approximate to those actually occurring in biological systems. These results are essential to understand the actual neuroprotective action mechanism exerted by phenolic compounds involving a pharmacological activity, an antioxidant effect or both actions exerted mutually.

A atualidade dos acidentes de trânsito na era da velocidade: uma visäo geral / Car accidents in the age of speed: an overview

Focaliza, numa perspectiva interdisciplinar, os estudos sobre acidentes de trânsito em escala nacional e internacional. Ele começa analisando o aumento da produçäo e consumo de veículos motorizados em todo o mundo e as transformaçöes sociais que esse fato acarretou. Atençäo especial é dada à degradaçäo do meio ambiente urbano e ao enorme custo social representado pelos acidentes de trânsito. Em seguida, é apresentado um panorama epidemiológico sobre as vítimas do trânsito. A relaçäo entre personalidade e acidente de trânsito mereceu atençäo especial, principalmente no que se refere ao comportamento infrator e ao consumo de bebidas alcoólicas e de outras drogas. Conclui enfatizando a necessidade de o Estado implementar políticas públicas específicas consistentes, a fim de se poder controlar o problema.

Aposentadoria, envelhecimento, condiçöes de trabalho e desemprego / Retirement, ageing, working conditions and unemployment

Em tempos de reformas previdenciárias, quando se discutem modificações dos benefícios securitários, em particular os relacionados com a aposentadoria, considera-se importante refletir sobre alguns aspectos. O envelhecimento desigual da população, as cicatrizes do tempo e do trabalho sobre o seu corpo, o atual contexto econômico e social, em especial o desemprego e a difícil recolocação dos trabalhadores em envelhecimento, num contexto de grandes impactos tecnológicos e organizacionais, num país com baixo grau de escolaridade, exigem uma discussão aprofundada sobre os critérios que contemplem a situação dos trabalhadores, e não simplesmente reformas com redução dos benefícios por razão da crise financeira institucional, como historicamente tem ocorrido no Brasil.

Aporte metodológico al conocimiento de la alienación psicosocial / A methodological contribution to psychosocial alienation knowledge

La presente comunicación informa respecto de una aproximación metodológica al estudio de la alienación a nivel psicológico. El propósito de la experiencia orientó la atención de los investigadores hacia el hecho de que los ítems del cuestionario utilizado habían sido redactados en primera persona: se trabajó entonces sobre la hipótese de la implicancia personal en el contenido de los ítens: se llegó a la conclusión de que ése es un factor que mueve a los respondientes a no contestar cómo piensan y sienten en realidad, sino a dar respuestas teñidas de "deseabilidad social"

Aporte metodológico al conocimiento de la alienación psicosocial / A methodological contribution to psychosocial alienation knowledge

La presente comunicación informa respecto de una aproximación metodológica al estudio de la alienación a nivel psicológico. El propósito de la experiencia orientó la atención de los investigadores hacia el hecho de que los ítems del cuestionario utilizado habían sido redactados en primera persona: se trabajó entonces sobre la hipótese de la implicancia personal en el contenido de los ítens: se llegó a la conclusión de que ése es un factor que mueve a los respondientes a no contestar cómo piensan y sienten en realidad, sino a dar respuestas teñidas de "deseabilidad social" (AU)