Effect of free radicals on adenosine A(2A) and dopamine D2 receptors in the striatum of young adult and aged rats

Parkinson's disease (PD) is a prevalent age-related motor dysfunction resulting from the hyperactivity of the indirect striatal pathway, which is controlled in an antagonistic manner by inhibitory dopamine D2 and facilitatory adenosine A(2A) receptors. Thus, dopamine precursors like l-DOPA are the standard therapy and A(2A) antagonists are now tested as anti-parkinsonians. Increased free radicals levels occur on aging and are proposed to be a contributing factor for PD. We now tested if free radicals affected A(2A) and D2 receptors in striatal membranes of young adult (2 months) and old (24 months) rats. The A(2A) receptor antagonist [3H]SCH 58261 bound to striatal membranes with a KD of 0.9 nM and a Bmax of 953 fmol/mg protein in young rats and with a KD of 0.8 nM and a Bmax of 725 fmol/mg protein in aged rats (24% decrease). The D2 receptor antagonist [3H]raclopride bound to striatal membranes with a KD of 4.0 nM and a Bmax of 598 fmol/mg protein in young rats and with a KD of 4.3 nM and a Bmax of 368 fmol/mg protein in aged rats (38% decrease). Exposure of striatal membranes to a free radical generation system (2 mM FeSO4 and 4 mM ascorbate) caused a similar decrease of [3H]SCH 58261 (35%) and [3H]raclopride (37%) binding in young adult rats but caused a greater decrease of [3H]SCH 58261 (49%) than of [3H]raclopride (20%) binding in aged rats. Thus, in aged rats, there is an unbalance of A(2A)/D2 receptor density favouring A(2A) receptors, which is restored on exposure to free radicals. This supports the hypothesis that the effectiveness of A(2A) receptor antagonists as anti-parkinsonians, demonstrated in young adult animals, may not be affected by a modified A(2A)/D2 receptor density in aged individuals suffering from exposure to increased free radical levels, as occurs in PD.     

Antioxidant activity of leaf extracts from Bauhinia monandra

Bauhinia monandra Kurz. is used in Brazil for the treatment of diabetes. Since this activity may be correlated with the presence of antioxidant compounds, leaf extracts of B. monandra were evaluated for their radical scavenging capacity (RSC). An ethanolic extract was taken up in aqueous methanol and partitioned with hexane, chloroform, ethyl acetate to yield three organic extracts together with remaining aqueous extract. The RSC was determined spectrophotometrically using 1,1-diphenylpicrylhydrazyl free radical (DPPH). The chloroform and ethyl acetate extracts were the most appropriate as sources of antioxidant compounds as shown by their inhibition concentration (IC50) and inhibition percentage (IP) values. The antioxidant activity of such extracts was attributed to the presence of three compounds of different polarities (flavonoids and steroids). The chloroform and ethyl acetate extracts exhibited an IC50 of approximately 2 mg/g DPPH and IP values in the range of 60-65%. The results indicate that the extracts of B. monandra have a very potent antioxidant activity, compared with the pure catechins used as positive controls and with other plant extracts.     

Simultaneous production of triploid and haploid eggs by triploid Squalius alburnoides (Teleostei: Cyprinidae)

The hybrid minnow Squalius alburnoides comprises diploid and polyploid forms with altered modes of reproduction. In the present paper, we report a cross where a triploid female generated both large, triploid and small, haploid eggs simultaneously, which were fertilized with S. pyrenaicus sperm. Although the large eggs were rarer (15%), they originated offspring with higher survivorship, so that tetraploids were dominant among the surviving siblings. The cross yielded apparently all female progeny. Inheritance patterns were inferred using four microsatellite markers and NORs (Nucleolus Organizer Regions) phenotypes, and suggested that haploid eggs were probably produced by an atypical hybridogenesis, in which the elimination of the unmatched genome permitted random segregation and recombination between the homospecific genomes, while the triploid eggs were clonal. The present results suggest that the occurrence of triploid unreduced eggs may be a new route for the natural tetraploidization in the complex.     

Enantioselective pharmacokinetics of lercanidipine in healthy volunteers

OBJECTIVE: The enantioselective kinetic disposition of lercanidipine, a dihydropyridine type of third-generation calcium antagonist, was investigated in six healthy male volunteers following a single 20 mg racemic oral dose. METHODS: Serial plasma samples were obtained from 0 to 24 h after drug administration. Lercanidipine enantiomers were analysed using a chiral LC-MS-MS method. RESULTS: The following differences (p < 0.05, Wilcoxon test) between (S) and (R) enantiomers were found (median): C(max) 2.071 ng mL(-1) versus 1.681 ng mL(-1); AUC(0-24)12.352 ng h mL(-1) versus 10.063 ng h mL(-1) and Cl/f 732.16 L h(-1) versus 1891.84 L h(-1). The AUC(0-infinity) values for (S)-LER were 1.21-fold higher than those for (R)-LER. CONCLUSION: The pharmacokinetics of LER was enantioselective in healthy volunteers following a single dose of 20 mg of the unlabeled racemic drug.     

Mitochondrial apoptotic cell death and moderate superoxide generation upon selective activation of non-desensitizing AMPA receptors in hippocampal cultures

In the present work we investigated the effect of selective stimulation of non-desensitizing alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors in the intracellular processes leading to hippocampal neuronal death and production of reactive oxygen species (ROS). Activation of AMPA receptors in the presence of cyclothiazide (CYZ), a blocker of AMPA receptor desensitization, resulted in the death of approximately 25% of neurones, which was prevented by 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(f)quinoxaline (NBQX), an AMPA-preferring receptor antagonist. (+)-5-Methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801) protected the neurones from necrotic death induced by AMPA or NMDA receptor activation. Neurodegeneration caused by selective activation of non-desensitizing AMPA receptors, in the presence of AMPA, CYZ and MK-801, significantly decreased the number of Co2+-positive neurones, used as a cytochemical marker of Ca2+-permeable AMPA receptors, but maintained intracellular ATP/ADP. The AMPA-mediated apoptotic cell death involved mitochondrial cytochrome c release and the activation of caspases-1 and -3, which was prevented by NBQX. Interestingly, although selective activation of AMPA receptors was not associated with production of intracellular peroxides, a moderate increase in superoxide production was observed upon exposure to antimycin A (AA). Furthermore, increased activity of Mn- superoxide dismutase (SOD) was observed on selective activation of non-desensitizing AMPA receptors. Taken together, these data make important contributions to the elucidation of the downstream pathways activated in AMPA receptor-mediated excitotoxicity in cultured rat hippocampal neurones.     

Colitis induced by proteinase-activated receptor-2 agonists is mediated by a neurogenic mechanism

Proteinase-activated receptor-2 (PAR2) activation induces colonic inflammation by an unknown mechanism. We hypothesized that PAR2 agonists administered intracolonically in mice induce inflammation via a neurogenic mechanism. Pretreatment of mice with neurokinin-1 and calcitonin-gene-related peptide (CGRP) receptor antagonists or with capsaicin showed attenuated PAR2-agonist-induced colitis. Immunohistochemistry demonstrated a differential expression of a marker for the type-1 CGRP receptor during the time course of PAR2-agonist-induced colitis, further suggesting a role for CGRP. We conclude that PAR2-agonist-induced intestinal inflammation involves the release of neuropeptides, which by acting on their receptors cause inflammation. These results implicate PAR2 as an important mediator of intestinal neurogenic inflammation.     

Identification of PDZ5, a candidate universal minicircle sequence binding protein of Trypanosoma cruzi

The dodecamer universal minicircle sequence is a conserved sequence present in minicircles of trypanosomatid kinetoplast DNA studied so far. This sequence is recognised by a protein named universal minicircle sequence binding protein, described for Crithidia fasciculata, involved in minicircle DNA replication. We have identified a Trypanosoma cruzi gene homologue of the Crithidia fasciculata universal minicircle sequence binding protein. Similar to the Crithidia fasciculata universal minicircle sequence binding protein, the Trypanosoma cruzi protein, named PDZ5, contains five zinc finger motifs. Pulsed field gel electrophoresis indicated that the pdz5 gene is located in the chromosomal band XX of the Trypanosoma cruzi genome. The predicted amino acid sequence of PDZ5 shows a high degree of similarity with several trypanosomatid zinc finger proteins. Specific antibody raised against Crithidia fasciculata universal minicircle sequence binding protein recognises both the recombinant and endogenous PDZ5. The complete pdz5 coding sequence cloned in bacteria expresses a recombinant PDZ5 protein that binds specifically to the universal minicircle sequence dodecamer. These data strongly suggest that PDZ5 represents a Trypanosoma cruzi universal minicircle sequence binding protein.     

Production and characterization of a thermostable alpha-amylase from Nocardiopsis sp. endophyte of yam bean

Thermostable amylolytic enzymes have been currently investigated to improve industrial processes of starch degradation. Studies on production of alpha-amylase by Nocardiopsis sp., an endophytic actinomycete isolated from yam bean (Pachyrhizus erosus L. Urban), showed that higher enzyme levels were obtained at the end of the logarithmic growth phase after incubation for 72 h at pH 8.6. Maximum activity of alpha-amylase was obtained at pH 5.0 and 70 degrees C. The isolated enzyme exhibited thermostable properties as indicated by retention of 100% of residual activity at 70 degrees C, and 50% of residual activity at 90 degrees C for 10 min. Extracellular enzyme from Nocardiopsis sp. was purified by fractional precipitation with ammonium sulphate. After 60% saturation produced 1130 U mg-1 protein and yield was 28% with purification 2.7-fold. The enzyme produced by Nocardiopsis sp. has potential for industrial applications.     

Purification of a thermostable endochitinase from Streptomyces RC1071 isolated from a cerrado soil and its antagonism against phytopathogenic fungi

AIMS: The chitinolytic activity of an actinomycete, isolated from a tropical acidic ferrasol (FAO) under cerrado (savanna) vegetation, is reported. METHODS AND RESULTS: Selection of the strain was based on spot inoculation on solid colloidal chitin medium. The use of chemotaxonomic, morphological and physiological procedures placed it in the Streptomyces genus, but identification to species level could not be achieved. A protein with endochitinase activity was isolated and purified from the supernatant fluid by concentration, precipitation, hydrophobic interaction, gel filtration and adsorption procedures. The molecular size of the purified chitinase was estimated by gel filtration to be 70 kDa, and its pI was 6.1. The enzyme had temperature and pH optima of 40 degrees C and 8.0, respectively, and showed thermal (30-70 degrees C) and pH (4-9) stabilities. Antifungal activity of the selected strain was observed following in vitro experiments using growing cells, crude extract or the purified endochitinase, and by detecting growth inhibition of the tested phytopathogenic fungi. CONCLUSION: Strain Streptomyces RC 1071 could not be placed into any known species, suggesting a new taxon. The purified endochitinase presented similar molecular weight, optimum temperature and pH activity, and stability of other endochitinolytic enzymes reported in the literature. In all three in vitro experiments performed, inhibition of growth of the phytopathogenic fungi used as test organisms was observed. SIGNIFICANCE AND IMPACT OF THE STUDY: Some of the endochitinase characteristics such as thermal stability, as well as pH tolerance, are very interesting for biotechnological purposes. In addition, due to its antifungal activity, Streptomyces RC 1071 seems promising for use in biological control.