Structure-activity analysis suggests an olfactory function for the unique antennal delta glutathione transferase of Apis mellifera

Glutathione transferases (GST) are detoxification enzymes that conjugate glutathione to a wide array of molecules. In the honey bee Apis mellifera, AmGSTD1 is the sole member of the delta class of GSTs, with expression in antennae. Here, we structurally and biochemically characterized AmGSTD1 to elucidate its function. We showed that AmGSTD1 can efficiently catalyse the glutathione conjugation of classical GST substrates. Additionally, AmGSTD1 exhibits binding properties with a range of odorant compounds. AmGSTD1 has a peculiar interface with a structural motif we propose to call 'sulfur sandwich'. This motif consists of a cysteine disulfide bridge sandwiched between the sulfur atoms of two methionine residues and is stabilized by CH…S hydrogen bonds and S…S sigma-hole interactions. Thermal stability studies confirmed that this motif is important for AmGSTD1 stability and, thus, could facilitate its functions in olfaction.

Exploring Bifidobacterium species community and functional variations with human gut microbiome structure and health beyond infancy

Aim: The human gut Bifidobacterium community has been studied in detail in infants and following dietary interventions in adults. However, the variability of the distribution of Bifidobacterium species and intra-species functions have been little studied, particularly beyond infancy. Here, we explore the ecology of Bifidobacterium communities in a large public dataset of human gut metagenomes, mostly corresponding to adults. Methods: We selected 9.515 unique gut metagenomes from curatedMetagenomicData. Samples were partitioned by applying Dirichlet's multinomial mixture to Bifidobacterium species. A functional analysis was performed on > 2.000 human-associated Bifidobacterium metagenome-assembled genomes (MAGs) paired with participant gut microbiome and health features. Results: We identified several Bifidobacterium-based partitions in the human gut microbiome differing in terms of the presence and abundance of Bifidobacterium species. The partitions enriched in both B. longum and B. adolescentis were associated with gut microbiome diversity and a higher abundance of butyrate producers and were more prevalent in healthy individuals. B. bifidum MAGs harboring a set of genes potentially related to phages were more prevalent in partitions associated with a lower gut microbiome diversity and were genetically more closely related. Conclusion: This study expands our knowledge of the ecology and variability of the Bifidobacterium community, particularly in adults, and its specific association with the gut microbiota and health. Its findings may guide the rational selection of Bifidobacterium strains for gut microbiome complementation according to the individual's endogenous Bifidobacterium community. Our results also suggest that gut microbiome stratification for particular genera may be relevant for studies of variations of species and associations with the gut microbiome and health.

[Acute electrophysiologic and echocardiographic changes induced by xamoterol in chronic chagasic patients with sinus node dysfunction]

PURPOSE

To evaluate xamoterol (Corwin)--a partial beta-adrenergic receptor agonist--in long-term chagasic patients with symptomatic sinus node dysfunction previously treated with permanent atrial pacemaker.

METHODS

Ten patients with permanent AAI pacing were studied. Initially, in spontaneous rhythm (sinus rhythm due to inhibition of the pacemaker) and under atrial pacing with rate of 60, 80 and 100ppm with temporary external programming of the pulse generator were evaluated. Basic heart rate, maximal sinus node recovery time and the point at which Wenckebach AV block was achieved were recorded. After that, echocardiographic evaluation was performed to analyze the left ventricular performance with ejection fraction calculation and the percentage of the fractional shortening during spontaneous rhythm and under atrial pacing with rate of 60, 80 and 100ppm. This protocol was repeated after 5mg of intravenous xamoterol.

RESULTS

Five men and 5 women (mean age of 46) were studied. Xamoterol increased the basic heart rate, the rate at which the Wenckebach AV block was achieved and shortened the maximal sinus node recovery time (statistically significant) suggesting a beta-adrenergic agonist action of the drug. Left ventricular performance showed significant improvement only when the values in sinus rhythm (during inhibition of the pulse generator) were compared. Under atrial pacing, left ventricular function was consistently improved in all patients but with no significance.

CONCLUSION

Xamoterol showed to be a beta-adrenergic receptors agonist in long-term chagasic patients with sinus node dysfunction at rest, when the simpatic tone was low, with evident action on the electrophysiologic parameters.

[Regression of tachycardiomyopathy after implant of pacemaker with antitachycardial function]

A 27-year-old woman with systemic lupus erythematosus and Wolff-Parkinson-White syndrome complicated with refractory tachycardia and class III heart failure treated with pacemaker implantation was described. She had cardiomyopathy that could be due to lupus erythematosus or tachycardia-induced. Nonpharmacologic therapeutic alternative was used and a universal DDD pulse generator with selected programming was chosen. Twenty-four months follow-up showed tachycardia control and regression of symptoms of heart failure to class I as well as improvement of left ventricular function evaluated by echocardiographic method. Thus, pacemaker implant may be an useful alternative approach in patients with tachycardiomyopathy in whose other nonpharmacologic therapeutic options could not be performed.