The 5-HT2B receptor: a main cardio-pulmonary target of serotonin

In agreement with previous data in the literature, our results indicate that serotonin, a monoamine neurotransmitter, can also regulate cell proliferation, cell movements and cell differentiation. We have recently shown that serotonin is required for embryonic heart development. Genetic ablation of the 5-HT2B receptor leads to partial embryonic and postnatal lethality with abnormal heart development. Similar molecular mechanisms seem to be involved in adult cardiomyocytes since mutant mice surviving to adulthood display a dilated cardiomyopathy. Furthermore this receptor appears to be involved in survival of cardiomyocytes. The 5-HT2B receptor is also implicated in systemic hypertension. Furthermore, mice with pharmacological or genetic ablation of 5-HT2B receptor are totally resistant to hypoxia-induced pulmonary hypertension, indicating that this receptor is regulating the pathologic vascular proliferation leading to this disease. Underlying mechanisms are still to be discovered.     

Molecular and Biochemical Characterization of a β-Fructofuranosidase from Xanthophyllomyces dendrorhous

An extracellular β-fructofuranosidase from the yeast Xanthophyllomyces dendrorhous was characterized biochemically, molecularly, and phylogenetically. This enzyme is a glycoprotein with an estimated molecular mass of 160 kDa, of which the N-linked carbohydrate accounts for 60% of the total mass. It displays optimum activity at pH 5.0 to 6.5, and its thermophilicity (with maximum activity at 65 to 70°C) and thermostability (with a T₅₀ in the range 66 to 71°C) is higher than that exhibited by most yeast invertases. The enzyme was able to hydrolyze fructosyl-β-(2→1)-linked carbohydrates such as sucrose, 1-kestose, or nystose, although its catalytic efficiency, defined by the k_cat/K_m ratio, indicates that it hydrolyzes sucrose approximately 4.2 times more efficiently than 1-kestose. Unlike other microbial β-fructofuranosidases, the enzyme from X. dendrorhous produces neokestose as the main transglycosylation product, a potentially novel bifidogenic trisaccharide. Using a 41% (wt/vol) sucrose solution, the maximum fructooligosaccharide concentration reached was 65.9 g liter⁻¹. In addition, we isolated and sequenced the X. dendrorhous β-fructofuranosidase gene (Xd-INV), showing that it encodes a putative mature polypeptide of 595 amino acids and that it shares significant identity with other fungal, yeast, and plant β-fructofuranosidases, all members of family 32 of the glycosyl-hydrolases. We demonstrate that the Xd-INV could functionally complement the suc2 mutation of Saccharomyces cerevisiae and, finally, a structural model of the new enzyme based on the homologous invertase from Arabidopsis thaliana has also been obtained.The basidiomycetous yeast Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) produces astaxanthin (3-3′-dihydroxy-β,β-carotene-4,4 dione [17, 25]). Different industries have displayed great interest in this carotenoid pigment due to its attractive red-orange color and antioxidant properties, which has intensified the molecular and genetic study of this yeast. As a result, several genes involved in the astaxanthin biosynthetic pathway have been cloned and/or characterized, as well as some other genes such as those encoding actin (60), glyceraldehyde-3-phosphate dehydrogenase (56), endo-β-1,3-glucanase, and aspartic protease (4). In terms of the use of carbon sources, a β-amylase (9), and an α-glucosidase (33) with glucosyltransferase activity (12), as well as a yeast cell-associated invertase (41), have also been reported.Invertases or β-fructofuranosidases (EC 3.2.1.26) catalyze the release of β-fructose from the nonreducing termini of various β-d-fructofuranoside substrates. Yeast β-fructofuranosidases have been widely studied, including that of Saccharomyces cerevisiae (11, 14, 45, 46), Schizosaccharomyces pombe (36), Pichia anomala (40, 49), Candida utilis (5, 8), or Schwanniomyces occidentalis (2). They generally exhibit strong similarities where sequences are available, and they have been classified within family 32 of the glycosyl-hydrolases (GH) on the basis of their amino acid sequences. The catalytic mechanism proposed for the S. cerevisiae enzyme implies that an aspartate close to the N terminus (Asp-23) acts as a nucleophile, and a glutamate (Glu-204) acts as the acid/base catalyst (46). In addition, the three-dimensional structures of some enzymes in this family have been resolved, such as that of an exoinulinase from Aspergillus niger (var. awamori; 37) and the invertase from Arabidopsis thaliana (55).As well as hydrolyzing sucrose, β-fructofuranosidases from microorganisms may also catalyze the synthesis of short-chain fructooligosaccharides (FOS), in which one to three fructosyl moieties are linked to the sucrose skeleton by different glycosidic bonds depending on the source of the enzyme (3, 52). FOS are one of the most promising ingredients for functional foods since they act as prebiotics (44), and they exert a beneficial effect on human health, participating in the prevention of cardiovascular diseases, colon cancer, or osteoporosis (28). Currently, Aspergillus fructosyltransferase is the main industrial producer of FOS (15, 52), producing a mixture of FOS with an inulin-type structure, containing β-(2→1)-linked fructose-oligomers (¹F-FOS: 1-kestose, nystose, or ¹F-fructofuranosylnystose). However, there is certain interest in the development of novel molecules that may have better prebiotic and physiological properties. In this context, β-(2→6)-linked FOS, where this link exits between two fructose units (⁶F-FOS: 6-kestose) or between fructose and the glucosyl moiety (⁶G-FOS: neokestose, neonystose, and neofructofuranosylnystose), may have enhanced prebiotic properties compared to commercial FOS (29, 34, 54). The enzymatic synthesis of 6-kestose and other related β-(2→6)-linked fructosyl oligomers has already been reported in yeasts such as S. cerevisiae (11) or Schwanniomyces occidentalis (2) and in fungi such as Thermoascus aurantiacus (26) or Sporotrichum thermophile (27). However, the production of FOS included in the ⁶G-FOS series has not been widely reported in microorganisms, probably because they are not generally produced (2, 15) or because they represent only a minor biosynthetic product (e.g., with baker''s yeast invertase) (11). Most research into neo-FOS production has been carried out with Penicillium citrinum cells (19, 31, 32, 39). In this context, neokestose is the main transglycosylation product accumulated by whole X. dendrorhous cells from sucrose (30), although the enzyme responsible for this reaction remained uncharacterized.Here, we describe the molecular, phylogenetic, and biochemical characterization of an extracellular β-fructofuranosidase from X. dendrorhous. Kinetic studies of its hydrolytic activity were performed using different substrates, and we investigated its fructosyltransferase capacity. The functionality of the gene analyzed was verified through its heterologous expression, and a structural model of this enzyme based on the homologous invertase from A. thaliana has also been obtained.     

Interactions between land use,habitat use,and population increase in greater snow geese: what are the consequences for natural wetlands?

The North American greater snow goose population has increased dramatically during the last 40 years. We evaluated whether refuge creation, changes in land use on the wintering and staging grounds, and climate warming have contributed to this expansion by affecting the distribution, habitat use, body condition, and migration phenology of birds. We also reviewed the effects of the increasing population on marshes on the wintering grounds, along the migratory routes and on the tundra in summer. Refuges established before 1970 may have contributed to the initial demographic increase. The most important change, however, was the switch from a diet entirely based on marsh plants in spring and winter (rhizomes of Scirpus/Spartina) to one dominated by crops (corn/young grass shoots) during the 1970s and 1980s. Geese now winter further north along the US Atlantic coast, leading to reduced hunting mortality. Their migratory routes now include portions of southwestern Québec where corn production has increased exponentially. Since the mid‐1960s, average temperatures have increased by 1–2.4°C throughout the geographic range of geese, which may have contributed to the northward shift in wintering range and an earlier migration in spring. Access to spilled corn in spring improved fat reserves upon departure for the Arctic and may have contributed to a high fecundity. The population increase has led to intense grazing of natural wetlands used by geese although these habitats are still largely undamaged. The foraging in fields allowed the population to exceed limits imposed by natural marshes in winter and spring, but also prevented permanent damage because of their overgrazing.     

Release of arachidonic acid by NMDA-receptor activation in the rat hippocampus

In hippocampal slices arachidonic acid released after NMDA post-synaptic receptor activation is thought to act as a retrograde trans-synaptic messenger which facilitates the pre-synaptic release of L-glutamate to be involved in the expression of long-term synaptic potentiation (LTP). We measured the mass amount of arachidonic acid released from hippocampal slices incubated under conditions which maintain the electrophysiological responsiveness of the slice. Melittin released arachidonic, oleic and docosahexaenoic acids by phospholipase A₂ activation but not palmitic or stearic acids. Of greater interestl-glutamate, N-methyl-d-aspartate and incubation conditions known to induce LTP selectively and rapidly increased the release of archidonic acid in amounts over basal levels of 200–300 ng/mg protein. This is the first direct determination of the mass amount of arachidonic acid released following NMDA receptor activation in the hippocampus.Special issue dedicated to Dr. Louis Sokoloff.     

Uncertainty quantification and sensitivity analysis of COVID-19 exit strategies in an individual-based transmission model

Many countries are currently dealing with the COVID-19 epidemic and are searching for an exit strategy such that life in society can return to normal. To support this search, computational models are used to predict the spread of the virus and to assess the efficacy of policy measures before actual implementation. The model output has to be interpreted carefully though, as computational models are subject to uncertainties. These can stem from, e.g., limited knowledge about input parameters values or from the intrinsic stochastic nature of some computational models. They lead to uncertainties in the model predictions, raising the question what distribution of values the model produces for key indicators of the severity of the epidemic. Here we show how to tackle this question using techniques for uncertainty quantification and sensitivity analysis. We assess the uncertainties and sensitivities of four exit strategies implemented in an agent-based transmission model with geographical stratification. The exit strategies are termed Flattening the Curve, Contact Tracing, Intermittent Lockdown and Phased Opening. We consider two key indicators of the ability of exit strategies to avoid catastrophic health care overload: the maximum number of prevalent cases in intensive care (IC), and the total number of IC patient-days in excess of IC bed capacity. Our results show that uncertainties not directly related to the exit strategies are secondary, although they should still be considered in comprehensive analysis intended to inform policy makers. The sensitivity analysis discloses the crucial role of the intervention uptake by the population and of the capability to trace infected individuals. Finally, we explore the existence of a safe operating space. For Intermittent Lockdown we find only a small region in the model parameter space where the key indicators of the model stay within safe bounds, whereas this region is larger for the other exit strategies.     

Rapid detection of avian influenza H5N1 virus using impedance measurement of immuno-reaction coupled with RBC amplification

Avian influenza virus (AIV) subtype H5N1 was first discovered in the 1990 s and since then its emergence has become a likely source of a global pandemic and economic loss. Currently accepted gold standard methods of influenza detection, viral culture and rRT-PCR, are time consuming, expensive and require special training and laboratory facilities. A rapid, sensitive, and specific screening method is needed for in-field or bedside testing of AI virus to effectively implement quarantines and medications. Therefore, the objective of this study was to improve the specificity and sensitivity of an impedance biosensor that has been developed for the screening of AIV H5. Three major components of the developed biosensor are immunomagnetic nanoparticles for the separation of AI virus, a microfluidic chip for sample control and an interdigitated microelectrode for impedance measurement. In this study polyclonal antibody against N1 subtype was immobilized on the surface of the microelectrode to specifically bind AIV H5N1 to generate more specific impedance signal and chicken red blood cells (RBC) were used as biolabels to attach to AIV H5N1 captured on the microelectrode to amplify impedance signal. RBC amplification was shown to increase the impedance signal change by more than 100% compared to the protocol without RBC biolabels, and was necessary for forming a linear calibration curve for the biosensor. The use of a second antibody against N1 offered much greater specificity and reliability than the previous biosensor protocol. The biosensor was able to detect AIV H5N1 at concentrations down to 10(3) EID(50)ml(-1) in less than 2h.     

Sternal osteomyelitis and scrofuloderma due to BCG vaccination

BCG vaccine has been used for nearly 100 years in the prevention of tuberculosis. The case of a 13 month-old girl vaccinated as a newborn with BCG is described as presenting a sternal mass with associated periostic erosion. The mass was resected, and histopathological examination revealed a chronic inflammatory reaction with caseous granulomas, and extension to bone and skin. PCR amplifications using specific primers for Mycobacterium tuberculosis on paraffin-embedded tissue were negative. BCG vaccination at birth, the histological appearance and the absence of M. tuberculosis DNA in the resected tissue indicated that osteomyelitis and scrofuloderma were a consequence of BCG. Osteomyelitis is a rarely occurring adverse effect of BCG vaccination, more commonly seen in immunosuppressed patients. In the patient described above, no symptoms of immunodeficiency were seen, however.     

Diatom Communities and Water Quality Assessment in Mountain Rivers of the Upper Segre Basin (La Cerdanya,Oriental Pyrenees)

Epilithic diatoms of mountain rivers from the upper Segre catchment (Oriental Pyrenees) were studied in 1998, during three different seasons: March, July and September. Four rivers, the river Segre and its three most important tributaries, Duran, Molina and Querol, were sampled in upstream and downstream stretches. The diatom communities were comparable in all upstream stretches of these mountain rivers draining siliceous substrates. Dominant taxa were Achnanthidium subatomus, Diatoma mesodon, Encyonema cf. minutum, E. silesiacum, Fragilaria arcus, F. capucina, Gomphonema calcifugum, G. pumilum, Meridion circulare and Nitzschia pura. Changes in water quality in the downstream stretches lead to the appearance of pollution tolerant taxa, such as Eolimna minima, Gomphoneis minuta, Navicula gregaria, and Nitzschia inconspicua. As a result, the values obtained with the diatom water quality indices (IPS Specific Polluosensitivity Index, CEE and IBD Biological Diatom Index) decreased. The diatom community composition and the derived water quality values did not change in the upstream stretches over the year. In contrast, significant changes were observed in the downstream stretches with best water␣quality in July, during high flows due to melting snow, and worst values in September, during low␣discharge. The diatom indices, especially the IPS, showed a good performance in these mountain rivers.