Intracellular Serotonin Modulates Insulin Secretion from Pancreatic β-Cells by Protein Serotonylation

While serotonin (5-HT) co-localization with insulin in granules of pancreatic β-cells was demonstrated more than three decades ago, its physiological role in the etiology of diabetes is still unclear. We combined biochemical and electrophysiological analyses of mice selectively deficient in peripheral tryptophan hydroxylase (Tph1−/−) and 5-HT to show that intracellular 5-HT regulates insulin secretion. We found that these mice are diabetic and have an impaired insulin secretion due to the lack of 5-HT in the pancreas. The pharmacological restoration of peripheral 5-HT levels rescued the impaired insulin secretion in vivo. These findings were further evidenced by patch clamp experiments with isolated Tph1−/− β-cells, which clearly showed that the secretory defect is downstream of Ca²⁺-signaling and can be rescued by direct intracellular application of 5-HT via the clamp pipette. In elucidating the underlying mechanism further, we demonstrate the covalent coupling of 5-HT by transglutaminases during insulin exocytosis to two key players in insulin secretion, the small GTPases Rab3a and Rab27a. This renders them constitutively active in a receptor-independent signaling mechanism we have recently termed serotonylation. Concordantly, an inhibition of such activating serotonylation in β-cells abates insulin secretion. We also observed inactivation of serotonylated Rab3a by enhanced proteasomal degradation, which is in line with the inactivation of other serotonylated GTPases. Our results demonstrate that 5-HT regulates insulin secretion by serotonylation of GTPases within pancreatic β-cells and suggest that intracellular 5-HT functions in various microenvironments via this mechanism in concert with the known receptor-mediated signaling.     

Upper and lower eyelid reconstruction

Reconstruction of the eyelids can range from simple repair to the integration of multiple complex procedures. Knowledge of eyelid anatomy, adequate preoperative planning, and meticulous surgical technique will optimize the anatomical and functional result. The purpose of this article is to review the relevant anatomy for eyelid reconstruction, to simplify defect analysis and preoperative planning, and to provide options for reconstruction of this complex area.     

Extensive diversity and inter-genepool introgression in a world-wide collection of indeterminate snap bean accessions

Common bean can be grown as a grain crop (dry beans) or as a fresh vegetable (snap beans/green beans), both items being important in nutritional terms for providing essential minerals and vitamins to the diet. Snap beans are thought to be derived predominantly from dry beans of the Andean genepool and to be of a recent European origin; however, the existence of Mesoamerican genepool characteristics especially in traditional indeterminate growth habit snap beans indicates a wider origin. The objective of this study was to evaluate genetic diversity within a set of 120 indeterminate (pole type) snap beans and 7 control genotypes representing each genepool using amplified fragment length polymorphism (AFLP) and simple sequence repeat or microsatellite (SSR) markers. The genotypes were predominantly from Asia, Europe and the United States but included some varieties from Latin America and Africa. AFLP polymorphism ranged from 53.2 to 67.7% while SSR polymorphism averaged 95.3% for the 32 fluorescent and 11 non-fluorescent markers evaluated and total expected heterozygosity was higher for SSR markers (0.521) than for AFLP markers (0.209). Both marker systems grouped the genotypes into two genepools with Andean and Mesoamerican controls, respectively, with the Mesoamerican group being predominant in terms of the number of genotypes assigned to this genepool. Phaseolin alleles were not tightly associated with genepool assignment indicating that introgression of this locus had occurred between the genepools, especially with phaseolin “S” in the Andean group (23.5%) and phaseolins “T” and “C” in the Mesoamerican group (12.2 and 8.2%, respectively). The implications of these results on the origin of pole type snap beans and on breeding strategies for this horticultural crop are discussed.     

3-Alkynyl selenophene protects against carbon-tetrachloride-induced and 2-nitropropane-induced hepatic damage in rats

The aim of this study was to investigate the protective effect of 3-alkynyl selenophene (3-ASP) on acute liver injury induced by carbon tetrachloride (CCl₄) and 2-nitropropane (2-NP) in rats. On the first day of treatment, the animals received 3-ASP (25 mg/kg, p.o.). On the second day, the rats received CCl₄ (1 mg/kg, i.p.) or 2-NP (100 mg/kg, p.o.). Twenty-four hours after CCl₄ or 2-NP administration, the animals were euthanized, and their plasma and liver were removed for biochemical and histological analyses. The histological analysis revealed extensive injury in the liver of CCl₄-exposed and 2-NP-exposed rats, which was attenuated by 3-ASP. 3-ASP significantly attenuated (1) the increase in plasmatic aspartate and alanine aminotransferase activities and lipid peroxidation levels induced by CCl₄ and 2-NP; (2) the inhibition of δ-aminolevulinic dehydratase activity caused by 2-NP; and (3) the decrease in ascorbic acid (AA) levels and catalase (CAT) activity caused by CCl₄. AA levels and CAT activity remained unaltered in the liver of rats exposed to 2-NP. The protective effect of 3-ASP on acute liver injury induced by CCl₄ and 2-NP in rats was demonstrated.     

Survey of moss-dwelling bdelloid rotifers from middle Arctic Spitsbergen (Svalbard)

A survey of bdelloid rotifers from moss and lichen samples collected in the middle Arctic tundra subzone of Spitsbergen (Svalbard) revealed an unexpected high species richness of 52 taxa, of which 18 fully identified species are new for the region. About one-fifth of the European bdelloid species are present. Moisture regime and geographic localization of the moss appeared the most important ecological features driving differences in species composition between samples.     

Investigator activities reduce nest predation in blackbirds Turdus merula

The effect of investigator perturbance has been traditionally considered detrimental for avian nesting success in terms of enhanced nest predation. This conclusion was however based on a taxonomically biased group of species and, thus, the study of that effect in additional species was essential for reaching a more firm conclusion. Furthermore, although it has been suggested that the effect of nest visiting could also depend on nest predator community, no study has so far tested this hypothesis yet. Trying to detect possible influence of nest‐visiting rates and predator community on nesting success we visited European blackbird Turdus merula nests at two different experimental rates in two populations that considerably differ in the composition of their nest predator communities and natural nest predation rates. Contrary to the traditional ideas, our results not only show that investigator disturbance significantly reduces nest predation, but also that this reduction is maintained in both populations despite the difference in the community of nest predators. We discuss these findings and suggest that predators, especially mammals, might avoid places disturbed by investigators.     

Evaluation of holocellulase production by plant-degrading fungi grown on agro-industrial residues

Agaricus brasiliensis CS1, Pleurotus ostreatus H1 and Aspergillus flavus produced holocellulases when grown in solid and submerged liquid cultures containing agro-industrial residues, including sugar cane bagasse and dirty cotton residue, as substrates. These isolates proved to be efficient producers of holocellulases under the conditions used in this screening. Bromatological analysis of agro-industrial residues showed differences in protein, fiber, hemicellulose, cellulose and lignin content. Maximal holocellulase activity (hemicellulase, cellulase and pectinase) was obtained using solid-state cultivation with 10% substrate concentration. In this case, remarkably high levels of xylanase and polygalacturonase activity (4,008 and 4,548 IU/l, respectively) were produced by A. flavus when grown in media containing corn residue, followed by P. ostreatus H1 with IU/l values of 1,900 and 3,965 when cultivated on 5% and 10% sugar cane bagasse, respectively. A. brasiliensis CS1 showed the highest reducing sugar yield (11.640 mg/ml) when grown on medium containing sugar cane bagasse. A. brasiliensis was also the most efficient producer of protein, except when cultivated on dirty cotton residue, which induced maximal production in A. flavus. Comparison of enzymatic hydrolysis of sugar cane bagasse and dirty cotton residue by crude extracts of A. brasiliensis CS1, P. ostreatus H1 and A. flavus showed that the best reducing sugar yield was achieved using sugar cane bagasse as a substrate.     

The impact of urea-induced unfolding on the redox process of immobilised cytochrome c

We have studied the effect of urea-induced unfolding on the electron transfer process of yeast iso-1-cytochrome c and its mutant K72AK73AK79A adsorbed on electrodes coated by mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol self-assembled monolayers. Electrochemical measurements, complemented by surface enhanced resonance Raman studies, indicate two distinct states of the adsorbed proteins that mainly differ with respect to the ligation pattern of the haem. The native state, in which the haem is axially coordinated by Met80 and His18, displays a reduction potential that slightly shifts to negative values with increasing urea concentration. At urea concentrations higher than 6 M, a second state prevails in which the Met80 ligand is replaced by an additional histidine residue. This structural change in the haem pocket is associated with an approximately 0.4 V shift of the reduction potential to negative values. These two states were found for both the wild-type protein and the mutant in which lysine residues 72, 73 and 79 had been substituted by alanines. The analysis of the reduction potentials, the reaction enthalpies and entropies as well as the rate constants indicates that these three lysine residues have an important effect on stabilising the protein structure in the adsorbed state and facilitating the electron transfer dynamics.