Antiparasitic Effects of Asteraceae Species Extracts on Echinococcus granulosus s.s.

Cystic echinococcosis is a zoonotic disease caused by the parasite Echinococcus granulosus sensu lato (s.l.), which is worldwide distributed and causes long-lasting infections in animals and humans. The existing treatment is limited to the use of benzimidazoles, mainly albendazole (ABZ). However, it has unwanted side effects and its efficacy is about 50%. The Asteraceae family includes plants that have therapeutic applications (medicinal species) and has an important role in new drug development. The species belonging to a different genus of this family show a wide range of anti-inflammatory, antimicrobial, antioxidant, hepatoprotective, and antiparasitic activities, among others. The aim of the present study was to evaluate the in vitro efficacy of extracts of four Asteraceae species against protoscoleces of E. granulosus sensu stricto (s.s.). On the other hand, the Stevia aristata extract was assessed on the murine cyst of E. granulosus (s.s.) and the efficacy of S. aristata extract was investigated in a murine model of CE. Stevia satureiifolia, S. aristata, Grindelia pulchella, and G. chiloensis extracts at 100 µg/mL caused a decrease in protoscoleces viability; however, S. aristata extract produced the greatest in vitro protoscolicidal effect. After 20 days of treatment with the highest concentration (100 µg/mL) of S. aristata extract, protoscoleces viability decreased to 0%. The tegumental changes observed by scanning electron microscopy were consistent with the reduction in vitality. The collapse of the germinal layer was registered in 60 ± 5.8% and 83.3 ± 12.0% of cysts treated during 4 days with 50 and 100 µg/ml, respectively. The half maximal effective concentration (EC50) value of the S. aristata extract against E. granulosus (s.s.) cysts was 47.86 µg/mL (96 h). The dosage of infected animals with the 50 mg kg-1 dose of S. aristata extract resulted in a significant reduction in cyst weight in comparison with the control group. In conclusion, S. aristata extract was demonstrated to exert a marked effect, both in vitro and in the murine model.

Anthelmintic activity of Stevia multiaristata extract against Echinococcus granulosus sensu stricto.

Cystic echinococcosis is a zoonotic disease caused by the larval stage of the parasite Echinococcus granulosus sensu lato. The available anti-parasitic treatment is mostly limited to a continuous administration of albendazole. However, due to its numerous side-effects and efficacy of around 50%, there is a need to find new drugs to improve the treatment for this disease. In the current study, the in vitro and in vivo efficacy of a Stevia multiaristata extract against E. granulosus sensu stricto (s.s.) was demonstrated. Stevia multiaristata extract (100 and 50 µg mL−1) caused a quick viability decrease on protoscoleces which was consistent with the observed tegumental alterations. Loss of turgidity was detected in 95 ± 3.4% of cysts incubated with S. multiaristata extract during 2 days (100 µg mL−1) and the collapse of the germinal layer was observed in 60 ± 9.3% of cysts treated with 100 µg mL−1 of the S. multiaristata extract during 4 days. The half maximal effective concentration value was 69.6 µg mL−1 and the selectivity index for E. granulosus s.s. cysts was 1.9. In this clinical efficacy study, the treatment of infected mice with the S. multiaristata extract (50 mg kg−1) caused a significant decrease in the weight of the cysts compared with the control group. These results coincided with the tissue damage observed in the cysts at the ultrastructural level. In conclusion, we observed high protoscolicidal and cysticidal effects, and significant reduction in the weight of the cysts in experimentally infected mice following treatment with the S. multiaristata extract.

Climatic variables drive temporal patterns of α and ß diversities of dung beetles.

Understanding the mechanisms underpinning spatiotemporal diversity patterns of biological communities is a major goal of ecology. We aimed to test two ecological hypotheses: (i) temporal patterns of ß-diversity will mostly be driven by nestedness, with a loss of species from summer to winter, and (ii) nestedness values will correlate with climatic variables instead of turnover values, indicating either a loss of species during winter or a gain of species during summer. We sampled dung beetles using standardized sampling protocols along a year in four Atlantic forest sites: two at the northwest and two at the central region of Rio Grande do Sul state, southern Brazil. We partitioned temporal patterns of ß-diversity into turnover and nestedness in order to investigate if community changes are driven by species substitution or gain/loss across time. Our results highlighted five main findings: (i) dung beetle composition varied more with sites than site geographic position; (ii) there was almost one and a half 'true' dung beetle assemblages regarding the spatial distribution of species weighed by abundance; (iii) we found a positive influence of mean temperature and a negative influence of relative humidity on both species richness and abundance; (iv) both spatial and temporal dissimilarity among sites were dominated by species replacement, while the relative importance of nestedness was higher in temporal than spatial patterns; (v) there was an effect of precipitation and relative humidity on temporal patterns of ß-diversity components, but these effects were site-dependent. Contrary to our expectations, the ß-diversity component of turnover dominated both spatial and temporal patterns in dung beetle dissimilarity among sites and months. Distinct climatic variables affected differently the α-diversity and ß-diversity components of dung beetle assemblages. Partitioning ß-diversity into temporal components is a promising approach to unveil patterns of the community dynamics and to produce insights on mechanisms underlying such patterns.

Reports of new wing color polymorphism and taxonomic information to cercopids (Auchenorrhyncha: Cercopidae) from upland rice crop, Pará State, Brazil / Registro de novos polimorfismos de cores de asas e informações taxonômicas para cercopídeos (Auchenorrhyncha: Cercopidae) com potencial importância econômica na cultura de arroz de terras altas, Estado do Pará, Brasil

Abstract Cercopidae is one of the largest families of the spittlebug superfamily Cercopoidea. Most spittlebugs species are characterized by bright color patterns. Thus, this study evaluated for the first time the Cercopidae species collected in rice crops, Novo Progresso, Pará state, Brazil. Insects were collected weekly between November/2010 and March/2011 from areas without (WA) and with agrochemical applications (AA). Four species were recorded: Deois incompleta (Walker, 1851) (71 specimens in WA area and 50 in AA area); Mahanarva spectabilis (Distant, 1909) (39 specimens in WA area and 39 in AA area); Mahanarava tristis (Fabricius, 1803) (26 specimens in WA area and 20 in AA area); Zulia pubescens (Fabricius, 1803) (11 specimens in WA area and four in AA area). The species collected displayed pronounced color polymorphism when compared with the color patterns of the same species from other regions. This makes correct identification more difficult for these species. Therefore, taxonomic and diagnostic informations provided in this study will help in the correct identification, control and monitoring of these insects in future studies. Besides that, we recommend monitoring in rice fields and further study of the biology and ecology of cercopids in Brazil to assess the potential of these species as rice pests.

Resumo Cercopidae é uma das maiores famílias de cigarrinhas dentro da superfamília Cercopoidea. A maioria das espécies de cigarrinhas é caracterizada pelos padrões de cores brilhantes. Deste modo, este estudo avaliou pela primeira vez, as espécies de Cercopidae coletados em cultura de arroz, Novo Progresso, Pará, Brasil. Os insetos foram coletados semanalmente entre novembro/2010 e março/2011 em áreas de arroz de terras altas sem (SA) e com aplicações de agroquímicos (CA). Quatro espécies foram registradas: Deois incompleta (Walker, 1851) (71 espécimes na área SA e 50 na área CA); Mahanarva spectabilis (Distant, 1909) (39 exemplares na área SA e 39 na área CA); Mahanarava tristis (Fabricius, 1803) (26 espécimes na área SA e 20 na área CA); Zulia pubescens (Fabricius, 1803) (11 espécimes na área SA e quatro na área CA). As espécies coletadas exibiram um polimorfismo de cor pronunciado quando comparadas com os padrões de cores das mesmas espécies de outras regiões. Isso torna mais difícil a identificação correta dessas espécies. Portanto, as informações taxonômicas e de diagnóstico fornecidas neste estudo ajudarão na identificação, controle e monitoramento desses insetos em estudos futuros. Além disso, recomendamos o monitoramento em campos de arroz e estudos posteriores de biologia e ecologia de cercopídeos no Brasil para avaliar o potencial dessas espécies como pragas de arroz.

Reports of new wing color polymorphism and taxonomic information to cercopids (Auchenorrhyncha: Cercopidae) from upland rice crop, Pará State, Brazil / Registro de novos polimorfismos de cores de asas e informações taxonômicas para cercopídeos (Auchenorrhyncha: Cercopidae) com potencial importância econômica na cultura de arroz de terras altas, Estado do Pará, Brasil

Cercopidae is one of the largest families of the spittlebug superfamily Cercopoidea. Most spittlebugs species are characterized by bright color patterns. Thus, this study evaluated for the first time the Cercopidae species collected in rice crops, Novo Progresso, Pará state, Brazil. Insects were collected weekly between November/2010 and March/2011 from areas without (WA) and with agrochemical applications (AA). Four species were recorded: Deois incompleta (Walker, 1851) (71 specimens in WA area and 50 in AA area); Mahanarva spectabilis (Distant, 1909) (39 specimens in WA area and 39 in AA area); Mahanarava tristis (Fabricius, 1803) (26 specimens in WA area and 20 in AA area); Zulia pubescens (Fabricius, 1803) (11 specimens in WA area and four in AA area). The species collected displayed pronounced color polymorphism when compared with the color patterns of the same species from other regions. This makes correct identification more difficult for these species. Therefore, taxonomic and diagnostic informations provided in this study will help in the correct identification, control and monitoring of these insects in future studies. Besides that, we recommend monitoring in rice fields and further study of the biology and ecology of cercopids in Brazil to assess the potential of these species as rice pests.(AU)

Cercopidae é uma das maiores famílias de cigarrinhas dentro da superfamília Cercopoidea. A maioria das espécies de cigarrinhas é caracterizada pelos padrões de cores brilhantes. Deste modo, este estudo avaliou pela primeira vez, as espécies de Cercopidae coletados em cultura de arroz, Novo Progresso, Pará, Brasil. Os insetos foram coletados semanalmente entre novembro/2010 e março/2011 em áreas de arroz de terras altas sem (SA) e com aplicações de agroquímicos (CA). Quatro espécies foram registradas: Deois incompleta (Walker, 1851) (71 espécimes na área SA e 50 na área CA); Mahanarva spectabilis (Distant, 1909) (39 exemplares na área SA e 39 na área CA); Mahanarava tristis (Fabricius, 1803) (26 espécimes na área SA e 20 na área CA); Zulia pubescens (Fabricius, 1803) (11 espécimes na área SA e quatro na área CA). As espécies coletadas exibiram um polimorfismo de cor pronunciado quando comparadas com os padrões de cores das mesmas espécies de outras regiões. Isso torna mais difícil a identificação correta dessas espécies. Portanto, as informações taxonômicas e de diagnóstico fornecidas neste estudo ajudarão na identificação, controle e monitoramento desses insetos em estudos futuros. Além disso, recomendamos o monitoramento em campos de arroz e estudos posteriores de biologia e ecologia de cercopídeos no Brasil para avaliar o potencial dessas espécies como pragas de arroz.(AU)

Reports of new wing color polymorphism and taxonomic information to cercopids (Auchenorrhyncha: Cercopidae) from upland rice crop, Pará State, Brazil.

Cercopidae is one of the largest families of the spittlebug superfamily Cercopoidea. Most spittlebugs species are characterized by bright color patterns. Thus, this study evaluated for the first time the Cercopidae species collected in rice crops, Novo Progresso, Pará state, Brazil. Insects were collected weekly between November/2010 and March/2011 from areas without (WA) and with agrochemical applications (AA). Four species were recorded: Deois incompleta (Walker, 1851) (71 specimens in WA area and 50 in AA area); Mahanarva spectabilis (Distant, 1909) (39 specimens in WA area and 39 in AA area); Mahanarava tristis (Fabricius, 1803) (26 specimens in WA area and 20 in AA area); Zulia pubescens (Fabricius, 1803) (11 specimens in WA area and four in AA area). The species collected displayed pronounced color polymorphism when compared with the color patterns of the same species from other regions. This makes correct identification more difficult for these species. Therefore, taxonomic and diagnostic informations provided in this study will help in the correct identification, control and monitoring of these insects in future studies. Besides that, we recommend monitoring in rice fields and further study of the biology and ecology of cercopids in Brazil to assess the potential of these species as rice pests.

Reports of new wing color polymorphism and taxonomic information to cercopids (Auchenorrhyncha: Cercopidae) from upland rice crop, Pará State, Brazil

Abstract Cercopidae is one of the largest families of the spittlebug superfamily Cercopoidea. Most spittlebugs species are characterized by bright color patterns. Thus, this study evaluated for the first time the Cercopidae species collected in rice crops, Novo Progresso, Pará state, Brazil. Insects were collected weekly between November/2010 and March/2011 from areas without (WA) and with agrochemical applications (AA). Four species were recorded: Deois incompleta (Walker, 1851) (71 specimens in WA area and 50 in AA area); Mahanarva spectabilis (Distant, 1909) (39 specimens in WA area and 39 in AA area); Mahanarava tristis (Fabricius, 1803) (26 specimens in WA area and 20 in AA area); Zulia pubescens (Fabricius, 1803) (11 specimens in WA area and four in AA area). The species collected displayed pronounced color polymorphism when compared with the color patterns of the same species from other regions. This makes correct identification more difficult for these species. Therefore, taxonomic and diagnostic informations provided in this study will help in the correct identification, control and monitoring of these insects in future studies. Besides that, we recommend monitoring in rice fields and further study of the biology and ecology of cercopids in Brazil to assess the potential of these species as rice pests.

Resumo Cercopidae é uma das maiores famílias de cigarrinhas dentro da superfamília Cercopoidea. A maioria das espécies de cigarrinhas é caracterizada pelos padrões de cores brilhantes. Deste modo, este estudo avaliou pela primeira vez, as espécies de Cercopidae coletados em cultura de arroz, Novo Progresso, Pará, Brasil. Os insetos foram coletados semanalmente entre novembro/2010 e março/2011 em áreas de arroz de terras altas sem (SA) e com aplicações de agroquímicos (CA). Quatro espécies foram registradas: Deois incompleta (Walker, 1851) (71 espécimes na área SA e 50 na área CA); Mahanarva spectabilis (Distant, 1909) (39 exemplares na área SA e 39 na área CA); Mahanarava tristis (Fabricius, 1803) (26 espécimes na área SA e 20 na área CA); Zulia pubescens (Fabricius, 1803) (11 espécimes na área SA e quatro na área CA). As espécies coletadas exibiram um polimorfismo de cor pronunciado quando comparadas com os padrões de cores das mesmas espécies de outras regiões. Isso torna mais difícil a identificação correta dessas espécies. Portanto, as informações taxonômicas e de diagnóstico fornecidas neste estudo ajudarão na identificação, controle e monitoramento desses insetos em estudos futuros. Além disso, recomendamos o monitoramento em campos de arroz e estudos posteriores de biologia e ecologia de cercopídeos no Brasil para avaliar o potencial dessas espécies como pragas de arroz.

Reports of new wing color polymorphism and taxonomic information to cercopids (Auchenorrhyncha: Cercopidae) from upland rice crop, Pará State, Brazil

Abstract Cercopidae is one of the largest families of the spittlebug superfamily Cercopoidea. Most spittlebugs species are characterized by bright color patterns. Thus, this study evaluated for the first time the Cercopidae species collected in rice crops, Novo Progresso, Pará state, Brazil. Insects were collected weekly between November/2010 and March/2011 from areas without (WA) and with agrochemical applications (AA). Four species were recorded: Deois incompleta (Walker, 1851) (71 specimens in WA area and 50 in AA area); Mahanarva spectabilis (Distant, 1909) (39 specimens in WA area and 39 in AA area); Mahanarava tristis (Fabricius, 1803) (26 specimens in WA area and 20 in AA area); Zulia pubescens (Fabricius, 1803) (11 specimens in WA area and four in AA area). The species collected displayed pronounced color polymorphism when compared with the color patterns of the same species from other regions. This makes correct identification more difficult for these species. Therefore, taxonomic and diagnostic informations provided in this study will help in the correct identification, control and monitoring of these insects in future studies. Besides that, we recommend monitoring in rice fields and further study of the biology and ecology of cercopids in Brazil to assess the potential of these species as rice pests.

Resumo Cercopidae é uma das maiores famílias de cigarrinhas dentro da superfamília Cercopoidea. A maioria das espécies de cigarrinhas é caracterizada pelos padrões de cores brilhantes. Deste modo, este estudo avaliou pela primeira vez, as espécies de Cercopidae coletados em cultura de arroz, Novo Progresso, Pará, Brasil. Os insetos foram coletados semanalmente entre novembro/2010 e março/2011 em áreas de arroz de terras altas sem (SA) e com aplicações de agroquímicos (CA). Quatro espécies foram registradas: Deois incompleta (Walker, 1851) (71 espécimes na área SA e 50 na área CA); Mahanarva spectabilis (Distant, 1909) (39 exemplares na área SA e 39 na área CA); Mahanarava tristis (Fabricius, 1803) (26 espécimes na área SA e 20 na área CA); Zulia pubescens (Fabricius, 1803) (11 espécimes na área SA e quatro na área CA). As espécies coletadas exibiram um polimorfismo de cor pronunciado quando comparadas com os padrões de cores das mesmas espécies de outras regiões. Isso torna mais difícil a identificação correta dessas espécies. Portanto, as informações taxonômicas e de diagnóstico fornecidas neste estudo ajudarão na identificação, controle e monitoramento desses insetos em estudos futuros. Além disso, recomendamos o monitoramento em campos de arroz e estudos posteriores de biologia e ecologia de cercopídeos no Brasil para avaliar o potencial dessas espécies como pragas de arroz.

Ozone and UV radiation over southern South America: climatology and anomalies.

Ozone and UV radiation were analyzed at eight stations from tropical to sub-Antarctic regions in South America. Ground UV irradiances were measured by multichannel radiometers as part of the Inter American Institute for Global Change Radiation network. The irradiance channels used for this study were centered at 305 nm (for UV-B measurements) and 340 nm (for UV-A measurements). Results were presented as daily maximum irradiances, as monthly averaged, daily integrated irradiances and as the ratio of 305 nm to 340 nm. These findings are the first to be based on a long time series of semispectral data from the southern region of South America. As expected, the UV-B channel and total column ozone varied with latitude. The pattern of the UV-A channel was more complex because of local atmospheric conditions. Total column ozone levels of < 220 Dobson Units were observed at all sites. Analysis of autocorrelations showed a larger persistence of total column ozone level than irradiance. A decreasing cross-correlation coefficient between 305 and 340 nm and an increasing cross-correlation coefficient between 305 nm and ozone were observed at higher latitudes, indicating that factors such as cloud cover tend to dominate at northern sites and that ozone levels tend to dominate at southern sites. These results highlight the value of long-term monitoring of radiation with multichannel radiometers to determine climatological data and evaluate the combination of factors affecting ground UV radiation.

Molecular modeling and QSAR analysis of the interaction of flavone derivatives with the benzodiazepine binding site of the GABA(A) receptor complex.

A large number of structurally different classes of ligands, many of them sharing the main characteristics of the benzodiazepine (BDZ) nucleus, are active in the modulation of anxiety, sedation, convulsion, myorelaxation, hypnotic and amnesic states in mammals. These compounds have high affinity for the benzodiazepine binding site (BDZ-bs) of the GABA(A) receptor complex. Since 1989 onwards our laboratories established that some natural flavonoids were ligands for the BDZ-bs which exhibit medium to high affinity in vitro and anxiolytic activity in vivo. Further research resulted in the production of synthetic flavonoid derivatives with increased biochemical and pharmacological activities. The currently accepted receptor/pharmacophore model of the BDZ-bs (Zhang, W.; Koeler, K. F.; Zhang, P.; Cook, J. M. Drug Des. Dev. 1995, 12, 193) accounts for the general requirements that should be met by this receptor for ligand recognition. In this paper we present a model pharmacophore which defines the characteristics for a ligand to be able to interact and bind to a flavone site, in the GABA(A) receptor. closely related to the BDZ-bs. A model of a flavone binding site has already been described (Dekermendjian, K.; Kahnberg, P.; Witt, M. R.; Sterner, O.; Nielsen, M.; Liljerfors, T. J. Med. Chem. 1999, 42, 4343). However, this alternative model is based only on graphic superposition techniques using as template a non-BDZ agonist. In this investigation all the natural and synthetic flavonoids found to be ligands for the BDZ-bs have been compared with the classical BDZ diazepam. A QSAR regression analysis of the parameters that describe the interaction demonstrates the relevance of the electronic effects for the ligand binding, and shows that they are associated with the negatively charged oxygen atom of the carbonyl group of the flavonoids and with the nature of the substituent in position 3'.

6,3'-dibromoflavone and 6-nitro-3'-bromoflavone: new additions to the 6,3'-disubstituted flavone family of high-affinity ligands of the brain benzodiazepine binding site with agonistic properties.

6,3'-dibromoflavone and 6-nitro-3'-bromoflavone inhibited [(3)H]flunitrazepam binding to the benzodiazepine binding site of the gamma amino butyric acid receptor complex with K(i) values between 17 and 36 nM in different brain regions. Their gamma amino butyric acid ratio for [(3)H]flunitrazepam binding to cerebral cortex membranes indicated partial agonistic properties. Both compounds had similar pharmacological effects: they produced anxiolytic-like effects at low doses but did not alter locomotor activity or muscle tonicity; sedation was caused only at doses higher than 30 mg/kg in mice. These synthetic flavone derivatives join an existing family of 6,3'-disubstituted flavone compounds with high affinity for the benzodiazepine binding site and partial agonistic profiles.

6-Chloro-3'-nitroflavone is a potent ligand for the benzodiazepine binding site of the GABA(A) receptor devoid of intrinsic activity.

6-Chloro-3'-nitroflavone integrates a list of nearly 70 flavone derivatives synthesized in our laboratories. The effects of 6-chloro-3'-nitroflavone on the benzodiazepine binding sites (BDZ-BSs) of the GABA(A) receptor were examined in vitro and in vivo. 6-Chloro-3'-nitroflavone inhibited the [3H]flunitrazepam ([3H]FNZ) binding to rat cerebral cortex membranes with a Ki of 6.68 nM and the addition of GABA to extensively washed membranes did not modify its affinity for the BDZ-BSs (GABA-shift = 1.16+/-0.12). The binding assays performed in rat striatal and cerebellar brain membranes showed that this compound has similar affinity to different populations of BDZ-BSs. Electrophysiological experiments revealed that 6-chloro-3'-nitroflavone did not affect GABA(A)-receptors (GABA(A)-Rs) responses recorded in Xenopus oocytes expressing alpha1beta2gamma2s subunits, but blocked the potentiation exerted by diazepam (DZ) on GABA-activated chloride currents. In vivo experiments showed that 6-chloro-3'-nitroflavone did not possess anxiolytic, anticonvulsant, sedative, myorelaxant actions in mice or amnestic effects in rats; however, 6-chloro-3'-nitroflavone antagonized diazepam-induced antianxiety action, anticonvulsion, short-term, and long-term amnesia and motor incoordination. These biochemical, electrophysiological, and pharmacological results suggest that 6-chloro-3'-nitroflavone behaves as an antagonist of the BDZ-BSs.

6-Methyl-3'-bromoflavone, a high-affinity ligand for the benzodiazepine binding site of the GABA(A) receptor with some antagonistic properties.

6-Methyl-3'-bromoflavone inhibited [(3)H]flunitrazepam binding to the benzodiazepine binding site of the GABA(A) receptor (BDZ-bs) with Ki values between 10 and 50 nM in different brain regions. The GABA ratio of 1.03 for [(3)H]flunitrazepam binding to cerebral cortex, 0.76 for cerebellum, 0.7 for hippocampus, 0.7 for striatum, and 0.8 for spinal cord indicated an antagonistic or weak inverse agonistic profile of 6-methyl-3'-bromoflavone on BDZ-bs. Unlike classical benzodiazepines, it had no anticonvulsant, anxiolytic, myorelaxant, sedative, amnestic or motor incoordination effects. However, it antagonized the muscle relaxant, the sedative effect, and the changes in locomotor activity induced by diazepam. Taken together, these findings suggest that 6-methyl-3'-bromoflavone has an antagonistic profile on the BDZ-bs.

Flavonoids and the central nervous system: from forgotten factors to potent anxiolytic compounds.

The list of activities of plant flavonoids did not include effects on the central nervous system (CNS) up to 1990, when our laboratory described the existence of natural anxiolytic flavonoids. The first of these was chrysin (5,7-dihydroxyflavone), followed by apigenin (5,7,4'-trihydroxyflavone) and flavone itself. Semisynthetic derivatives of flavone obtained by introducing halogens, nitro groups or both in its molecule, give rise to high affinity ligands for the benzodiazepine receptor, active in-vivo; 6,3'-dinitroflavone, for example, is an anxiolytic drug 30 times more potent than diazepam. The data collected in this paper make clear that some natural flavonoids are CNS-active molecules and that the chemical modification of the flavone nucleus dramatically increases their anxiolytic potency.

Pharmacological characterization of 6-bromo-3'-nitroflavone, a synthetic flavonoid with high affinity for the benzodiazepine receptors.

6-Bromo-3'-nitroflavone is a synthetic flavone derivative that selectively recognizes benzodiazepine receptors and has potent anxiolytic-like effects. Here, we describe in detail its pharmacological characterization. When i.p. injected in mice, 6-bromo-3'-nitroflavone (0.01-0.3 mg/kg) had an anxiolytic-like effect in the elevated plus-maze test. This effect was blocked by the specific benzodiazepine receptor antagonist, flumazenil. In addition, it exhibited anxiolytic-like actions when given orally (1 mg/kg). 6-Bromo-3'-nitroflavone did not exhibit myorelaxant effects (up to 30 mg/kg, i.p.). Unlike diazepam, this flavonoid produced no anterograde amnesia in a one-trial inhibitory avoidance learning. On the other hand, 6-bromo-3'-nitroflavone possessed mild anticonvulsant activity (0.1 mg/kg, i.p.) and provoked sedative-depressant actions only at doses 100-1000 times higher than those producing anxiolytic-like effects. 6-Bromo-3'-nitroflavone (0.1-1 mM) produced a lower potentiation of gamma-amino-butyric acid (GABA)-stimulated 36Cl- influx (126-138%) in comparison to diazepam (0.1 mM: 166%) in cerebral cortical membrane vesicles. Taken together, these findings suggest that 6-bromo-3'-nitroflavone has anxiolytic-like action possibly behaving as a partial agonist of the benzodiazepine receptors.

Detection of benzodiazepine receptor ligands in small libraries of flavone derivatives synthesized by solution phase combinatorial chemistry.

Solution phase combinatorial synthesis of flavone derivatives and evaluation of their affinity for the central benzodiazepine receptors is described. The libraries preparation is simple and provides a convenient method for rapid compound generation and screening. Thirty one new compounds were obtained of which the most promising, as high affinity benzodiazepine receptor ligands, were 6-bromo-3'-fluoroflavone; 6,3'-dichloroflavone; 6-bromo-3'-chloroflavone and 6-chloro-3'-bromoflavone.

Dose-dependence of the effects of corticosterone and the non-glucocorticoid, 18-hydroxycorticosterone, on the brush-border Na+/K+ exchanger.

Up to now, only glucocorticoids were thought to act on the renal proximal Na+/H+ exchanger. Using fluorimetric techniques we studied the kinetics of Na+/H+ exchange in brush border vesicles from ADX rats treated with increasing doses of corticosterone (B) and 18-hydroxycorticosterone (18OHB). Significant linear correlations were obtained when the Vmax of each treatment were plotted against log doses. 18OHB exhibits a slightly higher sensitivity than B and log-dose responses were steeper for 18OHB than for B treated rats. Differences between both treatments were highly significant at the 4.8 microg/100 g level, corresponding to the physiological blood level of 18OHB. Physiological doses of both steroids elicited equal Na+/H+ exchange-responses. 18OHB is not a glucocorticoid since even 88 microg/100 g did not promote hepatic glycogen deposition while the same dose of B increases glycogen deposits 3.5-fold. These results demonstrate the importance of the Na+/H+ exchanger as a mediator between corticoid action and H+ transport and that of the non-glucocorticoid 18OHB in this process.

Hormonal influence on lipid-protein interactions in biological membranes. Lactation effects on alkaline phosphatase activity and intestinal brush border membrane properties in rat.

It is known that prolactin modifies the fluidity of different biological membranes in rats and that the activity of intestinal alkaline phosphatase varies directly with the fluidity of the membranes in which it is found. Our objective was to study the intestinal alkaline phosphatase (IAP) activity, lipid composition and fluidity of the proximal small intestine brush border membranes under the influence of physiological high levels of prolactin, in rats with 15 days of lactating (Dams 15 days) compared with control virgin rats. The phenomenon was corroborated in dams from which the suckling pups had been withdrawn on the tenth day of lactation (Dams 10 days). The results showed a decrease on the IAP activity in dams in lactation with relation to control virgin and dams with withdrawal of pups. We found decreases in total phospholipids contents and fluidity and an increase in the microviscosity lipid membrane in dams with 15 days of lactating compared to virgins. In the same groups there were no differences in total lipids content and no modifications were observed in the quantity of total cholesterol and proteins. These results suggest that the changes produced by lactation could be one of the causes of alteration of brush border membranes properties by modifying the lipid-protein interactions and the alkaline phosphatase activity in the proximal small intestine.

Overview--flavonoids: a new family of benzodiazepine receptor ligands.

Benzodiazepines (BDZs) are the most widely prescribed class of psychoactive drugs in current therapeutic use, despite the important unwanted side-effects that they produce such as sedation, myorelaxation, ataxia, amnesia, ethanol and barbiturate potentiation and tolerance. Searching for safer BDZ-receptor (BDZ-R) ligands we have recently demonstrated the existence of a new family of ligands which have a flavonoid structure. First isolated from plants used as tranquilizers in folkloric medicine, some natural flavonoids have shown to possess a selective and relatively mild affinity for BDZ-Rs and a pharmacological profile compatible with a partial agonistic action. In a logical extension of this discovery various synthetic derivatives of those compounds, such as 6,3'-dinitroflavone were found to have a very potent anxiolytic effect not associated with myorelaxant, amnestic or sedative actions. This dinitro compound, in particular, exhibits a high affinity for the BDZ-Rs (Ki = 12-30 nM). Due to their selective pharmacological profile and low intrinsic efficacy at the BDZ-Rs, flavonoid derivatives, such as those described, could represent an improved therapeutic tool in the treatment of anxiety. In addition, several flavone derivatives may provide important leads for the development of potent and selective BDZ-Rs ligands.

Acute effects of two natural corticosteroids on the kinetics of the Na+/H+ exchanger in rat renal brush-border membranes.

We studied the effect of adrenalectomy and acute hormone replacement, using physiological doses of natural corticosteroids, on the kinetics of the Na+/H+ exchanger in brush border membrane vesicles. We collected the data using the acridine orange uptake technique. Adrenalectomized (ADX) rats presented a decreased maximal rate (Vmax) when compared with sham-operated animals (30,000 versus 41,000 fluorescent units/min, respectively). Administration of corticosterone (B) to ADX rats restored Vmax to values above control (up to 66,000 fluorescent units/min). Smaller doses of 18-OH-B led to similar results. K(m) (16 mM) remained the same for all the groups. Amiloride behaved as a pure competitive inhibitor, with a Ki = 0.02 mM and an I50 = 98 microM (in the presence of 50 mM sodium gluconate). The presence of sodium in the external buffer, before adding the vesicles, inhibited the exchange, with an I50 = 2 mM. We observed, a significant decrease in the Na+/H+ exchanger under non-acidotic conditions in response to adrenalectomy. Acute administration of physiological doses of natural occurring corticosteroids reversed the effect.