BMP antagonists and FGF signaling contribute to different domains of the neural plate in Xenopus

In ectodermal explants from Xenopus embryos, inhibition of BMP signaling is sufficient for neural induction, leading to the idea that neural fate is the default state in the ectoderm. Many of these experiments assayed the action of BMP antagonists on animal caps, which are relatively naïve explants of prospective ectoderm, and different results have led to debate regarding both the mechanism of neural induction and the appropriateness of animal caps as an assay system. Here we address whether BMP antagonists are only able to induce neural fates in pre-patterned explants, and the extent to which neural induction requires FGF signaling. We suggest that some discrepancies in conclusion depend on the interpretations of sox gene expression, which we show not only marks definitive neural tissue, but also tissue that is not yet committed to neural fates. Part of the early sox2 domain requires FGF signaling, but in the absence of organizer signaling, this domain reverts to epidermal fates. We also reinforce the evidence that ectodermal explants are naïve, and that explants that lack any dorsal prepattern are readily neuralized by BMP antagonists, even when FGF signaling is inhibited.     

Hydrogen transfer pathways of the asymmetric reduction of alpha,beta-unsaturated ketone mediated by baker's yeast

The hydrogen transfer mechanism of cofactor reduction and recycling processes in the yeast reduction of alpha,beta-unsaturated ketone was studied by using quantitative isotope tracing close to natural abundance measured by (2)H NMR. In the reaction, the active cofactor is NADPH. The cofactor-transferred hydride attacks the beta sp(2) carbon of the enone carbonyl while water hydrogen is transferred to the alpha position. The reductant involved in the reaction depends on the quantity of yeast. When the amount of yeast is very large, the enzymes use preferentially certain unidentified substance stored in the yeast cells rather than the added glucose as electron donor. In this case, the hydrogen transferred by the cofactor is mainly of water origin. When the yeast amount is low, the added glucose is more efficiently used by the enzymes as electron donor and its hydrogen atoms bound to C-1 and C-3 are delivered to the substrate.     

Effect of solid storage on caprine semen conservation at 5 degrees C

In this work, we investigated the effect of storage in solid-phase extender on buck semen conserved at 5 degrees C. Furthermore, we studied the effect of addition of cysteine to the extender and the washing of seminal plasma on sperm survival. In Experiment 1, milk-based extender (M) was used as a control to study the effect of solid media storage (G) and cysteine supplementation (C), and the combination of both (GC), on in vitro sperm survival of washed and non-washed semen, conserved up to 72 h at 5 degrees C. Motility, acrosome integrity (NAR) and hypo-osmotic swelling tests (HOST) were evaluated to assess in vitro sperm survival. In Experiment 2, an artificial insemination (AI) field trial was performed to compare G versus M. Solid media (G) maintained motility of spermatozoa during storage higher than any other extender (67% G versus 62% GC; 61% M and 59% C; P<0.05), but there was no difference in NAR or HOST between extenders (P>0.05). No improvement in sperm viability was obtained by addition of cysteine to the media. Washing of semen improved motility (65% versus 60%; P<0.05), NAR (70% versus 64%; P<0.05) and HOST (37% versus 28%; P<0.05). No significant differences in fertility were obtained between G and M extenders (47% versus 41%; P>0.05). In conclusion, washing of semen and dilution in gelatin-supplemented milk extender (solid storage) appears to be a successful method for goat semen storage at 5 degrees C.     

The information capacity of hypercycles

Hypercycles are information integration systems which are thought to overcome the information crisis of prebiotic evolution by ensuring the coexistence of several short templates. For imperfect template replication, we derive a simple expression for the maximum number of distinct templates n_m that can coexist in a hypercycle and show that it is a decreasing function of the length L of the templates. In the case of high replication accuracy we find that the product n_mL tends to a constant value, limiting thus the information content of the hypercycle. Template coexistence is achieved either as a stationary equilibrium (stable fixed point) or a stable periodic orbit in which the total concentration of functional templates is nonzero. For the hypercycle system studied here we find numerical evidence that the existence of an unstable fixed point is a necessary condition for the presence of periodic orbits.     

Effects of humic substances derived from organic waste enhancement on the growth and mineral nutrition of maize

A physico-chemical process has been developed to transform and enhance lignocellulosic waste in liquid humic extracts: humic-like substances (HLS). The aim of this study was to determine the effects of HLS on plant physiology in order to consider their agricultural use as organic fertilizers. The effects of HLS were evaluated on maize seed germination, and their impact on growth, development and mineral nutrition was studied on maize plants cultivated under hydroponic conditions. The experimental results showed that HLS do not increase the percentage and rate of germination but enhance the root elongation of seeds thus treated. Positive effects were also observed on the whole plant growth as well as on root, shoot and leaf biomass. These effects can be related to the high water and mineral consumption of plants undergoing this treatment. The high water efficiency indicated that such plants produce more biomass than non-treated plants for the same consumption of the nutrient solution. Furthermore, the use of HLS induced a flowering precocity and modified root development suggesting a possible interaction of HLS with developmental processes. Considering the beneficial effect of HLS on different stages of plant growth, their use may present various scientific and economic advantages. The physico-chemical transformation of sawdust is an interesting way of enhancing organic waste materials.     

Evidence for endogenous urotensin-II as an inhibitor of insulin secretion. Study in the perfused rat pancreas

In the perfused rat pancreas, infusion of urotensin-II (UII), a somatostatin-like peptide, inhibits glucose-induced insulin secretion. We have resorted to specific antagonists of the UII receptor (UT), palosuran and urantide, to investigate whether endogenous UII also behaves as an inhibitor of beta-cell secretion. The insulinostatic effect of UII was counteracted by palosuran and by urantide but not by a somatostatin-receptor antagonist (cyclo-somatostatin). Furthermore, the insulinostatic effect of somatostatin was not reversed by palosuran. These results suggest that UII and somatostatin blocked beta-cell secretion via distinct receptors. Finally, in the absence of exogenous UII, both palosuran and urantide potentiated glucose-induced insulin release, thus supporting the concept that endogenous UII is an insulinostatic peptide. By virtue of their insulinotropic effect, UT antagonists may be considered potential drugs for treating the impaired insulin secretion characteristic of type 2 diabetic patients.     

Somatostatin, insulin and glucagon secretion by the perfused pancreas from the cysteamine-treated rat

In rats, administration of a single dose of cysteamine (300 mg/kg, intragastrically) induces a depletion of pancreatic somatostatin content (approximately 60%) without modifying pancreatic insulin or glucagon content. In perfused pancreases from cysteamine-treated rats, there was a lack of somatostatin response to glucose, arginine or tolbutamide. In the absence of stimulated somatostatin release, the secretory responses of insulin and glucagon to glucose, to arginine, and to tolbutamide were not significantly different from those observed in pancreases from control rats. Our data do not support the concept that pancreatic somatostatin plays a major role in the control of insulin and glucagon release.     

Thyroid Hormone and Estrogen Regulate Exercise-Induced Growth Hormone Release

Growth hormone (GH) regulates whole body metabolism, and physical exercise is the most potent stimulus to induce its secretion in humans. The mechanisms underlying GH secretion after exercise remain to be defined. The aim of this study was to elucidate the role of estrogen and pituitary type 1 deiodinase (D1) activation on exercise-induced GH secretion. Ten days after bilateral ovariectomy, animals were submitted to 20 min of treadmill exercise at 75% of maximum aerobic capacity and tissues were harvested immediately or 30 min after exercise. Non-exercised animals were used as controls. A significant increase in D1 activity occurred immediately after exercise (~60%) in sham-operated animals and GH was higher (~6-fold) 30 min after exercise. Estrogen deficient rats exhibited basal levels of GH and D1 activity comparable to those found in control rats. However, after exercise both D1 activity and serum GH levels were blunted compared to sedentary rats. To understand the potential cause-effect of D1 activation in exercise-induced GH release, we pharmacologically blocked D1 activity by propylthiouracil (PTU) injection into intact rats and submitted them to the acute exercise session. D1 inhibition blocked exercise-induced GH secretion, although basal levels were unaltered. In conclusion, estrogen deficiency impairs the induction of thyroid hormone activating enzyme D1 in the pituitary, and GH release by acute exercise. Also, acute D1 activation is essential for exercise-induced GH response.     

Development of a Fluorescent Based Immunosensor for the Serodiagnosis of Canine Leishmaniasis Combining Immunomagnetic Separation and Flow Cytometry

Background

An accurate diagnosis is essential for the control of infectious diseases. In the search for effective and efficient tests, biosensors have increasingly been exploited for the development of new and highly sensitive diagnostic methods. Here, we describe a new fluorescent based immunosensor comprising magnetic polymer microspheres coated with recombinant antigens to improve the detection of specific antibodies generated during an infectious disease. As a challenging model, we used canine leishmaniasis due to the unsatisfactory sensitivity associated with the detection of infection in asymptomatic animals where the levels of pathogen-specific antibodies are scarce.

Methodology

Ni-NTA magnetic microspheres with 1,7 µm and 8,07 µm were coated with the Leishmania recombinant proteins LicTXNPx and rK39, respectively. A mixture of equal proportions of both recombinant protein-coated microspheres was used to recognize and specifically bind anti-rK39 and anti-LicTNXPx antibodies present in serum samples of infected dogs. The microspheres were recovered by magnetic separation and the percentage of fluorescent positive microspheres was quantified by flow cytometry.

Principal Findings

A clinical evaluation carried out with 129 dog serum samples using the antigen combination demonstrated a sensitivity of 98,8% with a specificity of 94,4%. rK39 antigen alone demonstrated a higher sensitivity for symptomatic dogs (96,9%), while LicTXNPx antigen showed a higher sensitivity for asymptomatic (94,4%).

Conclusions

Overall, our results demonstrated the potential of a magnetic microsphere associated flow cytometry methodology as a viable tool for highly sensitive laboratorial serodiagnosis of both clinical and subclinical forms of canine leishmaniasis.