Chiral lumazines: Preparation,properties, enantiomeric separation

Optically active lumazines (biolumazine, dictyolumazine, monalumazine, and neolumazine) are prepared from the corresponding pterins by enzymatic reaction, using pterin deaminase excreted by Dictyostelium discoideum. The fluorescence properties, circular dichroism spectra, and chromatographic behavior of these lumazines are studied. D - and L -enantiomers of biolumazine, dictyolumazine, and monalumazine are separated using a chiral flavoprotein column. This column also separates the enantiomeric pterins of the threo form: monapterin and dictyopterin. However, the column does not separate the enantiomeric pterins of the erythro form: neopterin and biopterin. By coupling a reverse-phase column to the flavoprotein column, the separation of pterins and lumazines in function of their hydrophobicity, as well as the separation of the diastereomers, is achieved. This coupled achiral/chiral high-performance liquid chromatography method enables determination of the stereoconfiguration of natural lumazines by comparison with optically pure compounds. A lumazine derivative, present in the extracellular medium of Dictyostelium discoideum, is identified as D -dictyolumazine, i.e., 6-(D -threo-1,2-dihydroxypropyl)-lumazine. © 1994 Wiley-Liss, Inc.     

Inhibition of urea synthesis by pent-4-enoic acid: potentiation by ammonia

Pent-4-enoic acid inhibited ureagenesis approximatively 90% in rat hepatocytes incubated with pyruvate, ammonia and ornithine. Inhibition of ureagenesis was much less with alanine as substrate (approximatively 10%). The addition of ammonia led to a drastic dose-dependent inhibition of ureagenesis by pent-4-enoate. Half-maximum effect of ammonia was observed at 0.2 mM concentration. Concomitant cellular concentrations of N-acetylglutamate were also drastically modified by the addition of ammonia as was the accumulation of citrulline. These data suggest that ammonia may seriously interfere with the metabolism of pent-4-enoic acid and leads to a dramatic potentiation of its toxicity.     

Chymotrypsin — Eudragit® complex formation

Eudragit® L100 (EuL) and Eudragit® S100 (EuS) are synthetic polyanions differing on their electric charge density. They interact with chymotrypsin (ChTRP), a basic protein forming soluble and non-soluble complexes. The complex formation was studied by dynamic light scattering, isothermal titration calorimetry, native fluorescence emission, circular dichroism and thermodynamical thermal stability of the enzyme. EuS was able to bind 33 ChTRP molecules while EuL, 60. The binding of ChTRP to both Eu was slightly endothermic and the entropic factor was responsible for the soluble complexes formation. The ChTRP-Eu size increases with pH and the binding of ChTRP to Eu modifies the Eu hydrodynamic radium. The interaction of ChTRP with Eu did not modify its secondary or tertiary structure. The thermal stability of ChTRP was increased when it interacted with both Eu.     

The invasive macrophyte Hydrilla verticillata causes taxonomic and functional homogenization of associated Chironomidae community

Limnology - Exotic species have invaded freshwater ecosystems, causing biodiversity loss of associated communities. We investigated the influence of the invasive macrophyte Hydrilla verticillata on...     

Ultrastructure variation in the spermatozoa of Pseudopaludicola frogs (Amphibia,Anura, Leptodactylidae), with brief comments on its phylogenetic relevance

The taxonomic history of the small frogs of the genus Pseudopaludicola from South America has been controversial. Phylogenetic inferences based on molecular data have identified four Pseudopaludicola clades, correlating with the known variation in karyotypes (2n = 22, 20, 18, and 16). In this study, the ultrastructure of the spermatozoa was analyzed in 12 species of the Pseudopaludicola, with the aim of describing their morphology and identifying characters that may contribute to a better understanding of the phylogenetic relationships. The spermatozoa presented marked differences in tail structures. The tails of the spermatozoa of the species with 2n = 22 chromosomes (Pseudopaludicola sp. 1 [P. pusilla group], Pseudopaludicola falcipes, P. mineira, and Pseudopaludicola saltica), as well as Pseudopaludicola ameghini and Pseudopaludicola ternetzi (2n=20), have juxta‐axonemal fibers, undulating membranes and axial fibers. In contrast, in the species with 2n = 18 (P. facureae, P. giarettai, Pseudopaludicola canga, P. atragula, and Pseudopaludicola sp. 2) and 2n = 16 (Pseudopaludicola mystacalis), there are no evident axial or juxta‐axonemal fibers, but a paraxonemal rod with a thick undulating membrane, which is shorter than that found among Pseudopaludicola species. The ultrastructural morphological differences observed in the spermatozoa of these species may be phylogenetically informative, given that they coincide with the consensus phylogeny of the group and appear to represent a progressive simplification of the spermatozoon. J. Morphol. 276:1495–1504, 2015. © 2015 Wiley Periodicals, Inc.     

Beta-globin gene cluster haplotype distribution in five Brazilian Indian tribes

Haplotypes derived from five polymorphic restriction sites in the beta-globin gene cluster were investigated in 139 individuals from five different Brazilian Indian tribes by the polymerase chain reaction (PCR). Eight haplotypes were identified. Haplotypes 2 (+????) and 6 (?++?+) were the most frequent and were common to all tribes. Their prevalences ranged from 60% to 93% and from 3% to 18%, respectively. Average heterozy-gosity measured by the Gini-Simpson index is markedly reduced among these Brazilian Indians when compared with Europeans (56%), but much less (8%) in relation to Asiatics, suggesting the absence of an important bottleneck effect in the early colonization of South America. The coefficient of gene differentiation (GST′) was estimated as 0.082 among six Brazilian Indian tribes, but when only three Tupi-Mondé-speaking tribes were considered, this estimate was reduced to 0.030. © 1995 Wiley-Liss, Inc.     

Effect of progesterone on the expression of GABAA receptor subunits in the prefrontal cortex of rats: implications of sex differences and brain hemisphere

Progesterone is a neuroactive hormone with non‐genomic effects on GABA_A receptors (GABA_AR). Changes in the expression of GABA_AR subunits are related to depressive‐like behaviors in rats. Moreover, sex differences and depressive behaviors have been associated with prefrontal brain asymmetry in rodents and humans. Thus, our objective was to investigate the effect of progesterone on the GABA_AR α1 and γ2 subunits mRNA expression in the right and left prefrontal cortex of diestrus female and male rats exposed to the forced swimming test (FST). Male and female rats (n = 8/group) were randomly selected to receive a daily dose of progesterone (0·4 mg·kg^–1) or vehicle, during two complete female estrous cycles (8–10 days). On the experiment day, male rats or diestrus female rats were euthanized 30 min after the FST. Our results showed that progesterone significantly increased the α1 subunit mRNA in both hemispheres of male and female rats. Moreover, there was an inverse correlation between depressive‐like behaviors and GABA_AR α1 subunit mRNA expression in the right hemisphere in female rats. Progesterone decreased the GABA_AR γ2 mRNA expression only in the left hemisphere of male rats. Therefore, we conclude that the GABA_A system displays an asymmetric distribution according to sex and that progesterone, at lower doses, presents an antidepressant effect after increasing the GABA_AR α1 subunit expression in the right prefrontal cortex of female rats. Copyright © 2012 John Wiley & Sons, Ltd.     

Nuclear and Wolbachia-based multimarker approach for the rapid and accurate identification of tsetse species

Background

Tsetse flies (Diptera: Glossinidae) are solely responsible for the transmission of African trypanosomes, causative agents of sleeping sickness in humans and nagana in livestock. Due to the lack of efficient vaccines and the emergence of drug resistance, vector control approaches such as the sterile insect technique (SIT), remain the most effective way to control disease. SIT is a species-specific approach and therefore requires accurate identification of natural pest populations at the species level. However, the presence of morphologically similar species (species complexes and sub-species) in tsetse flies challenges the successful implementation of SIT-based population control.

Results

In this study, we evaluate different molecular tools that can be applied for the delimitation of different Glossina species using tsetse samples derived from laboratory colonies, natural populations and museum specimens. The use of mitochondrial markers, nuclear markers (including internal transcribed spacer 1 (ITS1) and different microsatellites), and bacterial symbiotic markers (Wolbachia infection status) in combination with relatively inexpensive techniques such as PCR, agarose gel electrophoresis, and to some extent sequencing provided a rapid, cost effective, and accurate identification of several tsetse species.

Conclusions

The effectiveness of SIT benefits from the fine resolution of species limits in nature. The present study supports the quick identification of large samples using simple and cost effective universalized protocols, which can be easily applied by countries/laboratories with limited resources and expertise.

     

Developmental changes of citrullinogenesis, mitochondrial N-acetylglutamate content and N-acetylglutamate synthetase in fetal and neonatal rats

A low citrullinogenesis (less than 60 per cent of the adult value) was observed throughout the suckling period when mitochondria isolated from newborn rat liver were incubated in vitro with L-glutamate or succinate as oxidizable substrates. The adult value was reached after weaning. From birth to weaning, intact mitochondria synthesized more citrulline when supplemented with L-glutamate than with succinate. The low citrullinogenesis could not be explained by low carbamoylphosphate synthetase-I and ornithine transcarbamoylase activities that reached adult values at birth. The decreased citrullinogenesis seen for the first three days of life seemed to be related to the low intramitochondrial concentration of N-acetylglutamate, an activator of the carbamoylphosphate synthetase-I. The concentration of this activator did not differ from that reported for adult rat liver mitochondria after the fourth day of life. The discrepancy between the normal value of N-acetylglutamate concentration and the low activity of the N-acetylglutamate synthetase (15 to 30 per cent of the adult activity) is discussed on the basis of acetyl-CoA or L-glutamate availability in mitochondria isolated from newborn or young rats.