Sequential asymmetric auctions with endogenous participation

In this paper we suggest a model of sequential auctions with endogenous participation where each bidder conjectures about the number of participants at each round. Then, after learning his value, each bidder decides whether or not to participate in the auction. In the calculation of his expected value, each bidder uses his conjectures about the number of participants for each possible subgroup. In equilibrium, the conjectured probability is compatible with the probability of staying in the auction. In our model, players face participation costs, bidders may buy as many objects as they wish and they are allowed to drop out at any round. Bidders can drop out at any time, but they cannot come back to the auction. In particular we can determine the number of participants and expected prices in equilibrium. We show that for any bidding strategy, there exists such a probability of staying in the auction. For the case of stochastically independent objects, we show that in equilibrium every bidder who decides to continue submits a bid that is equal to his value at each round. When objects are stochastically identical, we are able to show that expected prices are decreasing.

Neuropharmacological basis of rTMS-induced analgesia: The role of endogenous opioids

We investigated the role of endogenous opioid systems in the analgesic effects induced by repetitive transcranial magnetic stimulation (rTMS). We compared the analgesic effects of motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC) stimulation before and after naloxone or placebo treatment, in a randomized, double-blind crossover design, in healthy volunteers. Three groups of 12 volunteers were selected at random and given active stimulation (frequency 10 Hz, at 80% motor threshold intensity, 1500 pulses per session) of the right M1, active stimulation of the right DLPFC, or sham stimulation, during two experimental sessions 2 weeks apart. Cold pain thresholds and the intensity of pain induced by a series of fixed-temperature cold stimuli (5, 10, and 15 degrees C) were used to evaluate the analgesic effects of rTMS. Measurements were made at the left thenar eminence, before and 1 hour after the intravenous injection of naloxone (bolus of 0.1 mg/kg followed by a continuous infusion of 0.1 mg/kg/h until the end of rTMS) or placebo (saline). Naloxone injection significantly decreased the analgesic effects of M1 stimulation, but did not change the effects of rTMS of the DLPFC or sham rTMS. This study demonstrates, for the first time, the involvement of endogenous opioid systems in rTMS-induced analgesia. The differential effects of naloxone on M1 and DLPFC stimulation suggest that the analgesic effects induced by the stimulation of these 2 cortical sites are mediated by different mechanisms. (C) 2010 Published by Elsevier B.V. on behalf of International Association for the Study of Pain.

Asymmetric dimethylarginine endogenous inhibition of nitric oxide synthase causes differential vasculature effects

Background: Asymmetric dimethylarginine (ADMA), produced during protein metabolism, is an endogenous inhibitor of nitric oxide synthase, but little is known about its direct vasoactive properties in different arterial beds. Material/Methods: Segments of canine coronary, renal, and femoral arteries were pretreated with increasing concentrations of ADMA, and endothelial function was evaluated in organ chambers. Results: In precontracted canine coronary arteries, the highest concentrations of ADMA inhibited endothelium-dependent relaxation mediated by acetylcholine (n=7), but no concentration of ADMA inhibited receptor-independent relaxation mediated by calcium ionophore (n=7) (P<.001). The effect of ADMA on acetylcholine-mediated relaxation was shown to be competitive inhibition of the nitric oxide synthase pathway, because the addition of L-arginine (10(-3) M), but not D-arginine (101 M), reversed the effect produced by 10(-5) M ADMA. Further, ADMA did not alter endothelium-independent relaxation mediated by sodium nitroprusside (10(-9) to 10(-6) M; n=7). Femoral arteries (n=7) and renal arteries (n=7) were more sensitive to ADMA than were coronary arteries, and they demonstrated significant ADMA inhibition to receptor dependent relaxation induced by acetylcholine (P=.03 and P=.01, respectively) and to receptor-independent relaxation induced by calcium ionophore (P=.02 and P=.01, respectively). Conclusions: Endothelium-dependent relaxation mediated by ADMA is more marked in femoral and renal arteries than in coronary arteries. The response in coronary arteries may be overall protective. Considering these different effects in various artery types, the role of ADMA as a confiable and specific cardiovascular risk factor is questioned.

Fed State Protein Turnover in Healthy Older Persons under a Usual Protein-Rich Diet

The objective of this study was to verify the protein turnover rates of healthy older persons under a usual protein-rich diet and to compare values to those described in the literature. This cross-sectional study was conducted at Metabolism Unit, Univ. Hospital of the School of Medicine of Ribeirao Preto, Univ. of Sao Paulo, Brazil. In this study, 7 healthy older persons aged 65.4 +/- 2.8 y, with BMI 22.7 +/- 2.4 kg/m(2) and a mean daily protein intake of 1.34 g of protein/kg were studied. A 9-h whole-body (15)N-glycine single-dose study was performed after an overnight fast. During the study, each subject received 6 isoenergetic, isonitrogenous meals at 2-h intervals based on their average intake. Ammonium, urea, and total nitrogen were quantified and analyzed by mass spectrometry, with the determination of total protein turnover rates by the (15)N-glycine method. The results show that total nitrogen output was 3.2 +/- 0.96 g/N and intake 7.7 +/- 1 g/N, (15)N nitrogen flux was 30.6 +/- 6.3 g/9 h. Endogenous nitrogen balance was positive (4.5g +/- g/N in 9 h). In conclusion, the protein turnover of healthy older persons under a usual protein-rich diet is positive during the fed state and has synthesis and degradation rates similar to those previously described in studies involving diet adaptation periods.

Detrimental role of endogenous nitric oxide in host defence against Sporothrix schenckii

We earlier demonstrated that nitric oxide (NO) is a fungicidal molecule against Sporothrix schenckii in vitro. In the present study we used mice deficient in inducible nitric oxide synthase (iNOS(-/-)) and C57BL/6 wild-type (WT) mice treated with N omega-nitro-arginine (Nitro-Arg-treated mice), an NOS inhibitor, both defective in the production of reactive nitrogen intermediates, to investigate the role of endogenous NO during systemic sporotrichosis. When inoculated with yeast cells of S. schenckii, WT mice presented T-cell suppression and high tissue fungal dissemination, succumbing to infection. Furthermore, susceptibility of mice seems to be related to apoptosis and high interleukin-10 and tumour necrosis factor-alpha production by spleen cells. In addition, fungicidal activity and NO production by interferon-gamma (IFN-gamma) and lipopolysaccharide-activated macrophages from WT mice were abolished after fungal infection. Strikingly, iNOS(-/-) and Nitro-Arg-treated mice presented fungal resistance, controlling fungal load in tissues and restoring T-cell activity, as well as producing high amounts of IFN-gamma Interestingly, macrophages from these groups of mice presented fungicidal activity after in vitro stimulation with higher doses of IFN-gamma. Herein, these results suggest that although NO was an essential mediator to the in vitro killing of S. schenckii by macrophages, the activation of NO system in vivo contributes to the immunosuppression and cytokine balance during early phases of infection with S. schenckii.

Is dystonic posturing during temporal lobe epileptic seizures the expression of an endogenous anticonvulsant system?

In temporal lobe epilepsy (TLE) seizures, tonic or clonic motor behaviors (TCB) are commonly associated with automatisms, versions, and vocalizations, and frequently occur during secondary generalization. Dystonias are a common finding and appear to be associated with automatisms and head deviation, but have never been directly linked to generalized tonic or clonic behaviors. The objective of the present study was to assess whether dystonias and TCB are coupled in the same seizure or are associated in an antagonistic and exclusive pattern. Ninety-one seizures in 55 patients with TLE due to mesial temporal sclerosis were analyzed. Only patients with postsurgical seizure outcome of Engel class I or II were included. Presence or absence of dystonia and secondary generalization was recorded. Occurrence of dystonia and occurrence of bilateral tonic or clonic behaviors were negatively correlated. Dystonia and TCB may be implicated in exclusive, non-coincidental, or even antagonistic effects or phenomena in TLE seizures. A neural network related to the expression of one behavioral response (e.g., basal ganglia activation and dystonia) might theoretically ""displace"" brain activation or disrupt the synchronism of another network implicated in pathological circuit reverberation and seizure expression. The involvement of basal ganglia in the blockade of convulsive seizures has long been observed in animal models. The question is: Do dystonia and underlying basal ganglia activation represent an attempt of the brain to block imminent secondary generalization? (C) 2007 Elsevier Inc. All rights reserved.

Short-term urea feeding decreases in vitro hatching of bovine blastocysts

Cows fed high-protein diets may have impaired reproductive performance. Although the pathogenesis has not been completely elucidated, it appears that not only the uterus, but also the follicle and oocyte, are affected by excessive plasma urea nitrogen (PUN) concentrations. Thus, the objective was to determine the effects of short-term urea feeding on the competence of bovine oocytes. Forty crossbred heifers (Bos indicus vs Bos taurus) were allocated to two groups, namely CONTROL (maintenance diet) and UREA (maintenance diet supplemented with 75 g of urea/day), following a cross-over design. Heifers received their respective diets for 6 d (without adaptation). On the sixth day, blood samples were harvested both before and 3 h after feeding, and cumulus oocyte complexes (COCs) were collected by ovum pick-up. Although PUN concentrations were higher in UREA than CONTROL heifers (31.31 mg/dL +/- 1.13 vs 22.12 mg/dL +/- 0.86; mean +/- SEM), neither the number of COCs recovered (8.8 +/- 1.0 vs 9.2 +/- 0.8, UREA vs CONTROL, respectively) nor their quality (based on morphology) differed significantly between groups. Next, oocytes were fertilized and cultured in vitro to assess developmental rates. There was an absence of significant differences between groups for rates of cleavage (Day 3) or blastocyst formation (Days 6, 7 and 9), but the hatched blastocyst rate on Day 11 after fertilization was lower (P < 0.05) in the UREA than the CONTROL groups (64.3 vs 83.5%). Therefore, we inferred that the effects of urea were only manifest later in development. In conclusion, high PUN concentrations decreased oocyte competence in heifers, reinforcing the hypothesis that poor reproductive performance in cows with high PUN was due, at least in part, to a deleterious effect on oocytes. (C) 2011 Elsevier Inc. All rights reserved.

Effects of statins on matrix metalloproteinases and their endogenous inhibitors in human endothelial cells

Statins exert anti-inflammatory effects and downregulate matrix metalloproteinases (MMPs) expression, thus contributing to restore cardiovascular homeostasis in cardiovascular diseases. We aimed at comparing the effects of different statins (simvastatin, atorvastatin, and pravastatin) on MMP-2, MMP-9, tissue inhibitors of metalloproteinases (TIMP)-1, TIMP-2, and MMP-9/TIMP-1 and MMP-2/TIMP-2 ratios released by human umbilical vein endothelial cells (HUVEC) stimulated by phorbol myristate acetate (PMA). HUVECs were incubated with statins (0.1-10 mu M) for 12 h before stimulation with PMA 100 nM. Monolayers were used to perform cell viability assays and the supernatants were collected to determine MMPs and TIMPs levels by gelatin zymography and/or enzyme immunoassay. While treatment with PMA increased MMP-9 and TIMP-1 levels (by 556% and 159%, respectively; both P < 0.05), it exerted no effects on MMP-2 and TIMP-2 levels. Simvastatin and atorvastatin, but not pravastatin, attenuated PMA-induced increases in MMP-9 levels (P < 0.05). Only atorvastatin decreased baseline MMP-2 levels significantly (P < 0.05). We found no effects on TIMP-2 levels. Simvastatin and atorvastatin, but not pravastatin, decreased MMP-9/TIMP-1 ratio significantly (both P < 0.05), whereas atorvastatin and pravastatin, but not simvastatin, decreased MMP-2/TIMP-2 ratio significantly (both P < 0.05). Our data support the notion that statins with different physicochemical features exert variable effects on MMP/TIMP ratios (which reflect net MMP activity). Our results suggest that more lipophilic statins (simvastatin and atorvastatin), but not the hydrophilic statin pravastatin, downregulate net MMP-9 activity. However, atorvastatin and pravastatin may downregulate net MMP-2 activity. The clinical implications of the present findings deserve further investigation.

Sodium bicarbonate solution as an anti-erosive agent against simulated endogenous erosion

This study investigated whether sodium bicarbonate solution, applied on enamel previously exposed to a simulated intrinsic acid, can control dental erosion. Volunteers wore palatal devices containing enamel slabs, which were exposed twice daily extra-orally to hydrochloric acid (0.01 M, pH 2) for 2 min. Immediately afterwards, the palatal devices were re-inserted in the mouth and volunteers rinsed their oral cavity with a sodium bicarbonate solution or deionized water for 60 s. After the washout period, the palatal devices were refilled with a new set of specimens and participants were crossed over to receive the alternate rinse solution. The surface loss and surface microhardness (SMH) of specimens were assessed. The surface loss of eroded enamel rinsed with a sodium bicarbonate solution was significantly lower than the surface loss of eroded enamel rinsed with deionized water. There were no differences between treatments with sodium bicarbonate and deionized water for SMH measurements. Regardless of the solution used as an oral rinse, eroded enamel showed lower SMH than uneroded specimens. Rinsing with a sodium bicarbonate solution after simulated endogenous erosive challenge controlled enamel surface loss but did not alter the microhardness.

Fate of urea nitrogen applied to a banana crop in the wet tropics of Queensland

This paper reports a study in the wet tropics of Queensland on the fate of urea applied to a dry or wet soil surface under banana plants. The transformations of urea were followed in cylindrical microplots (10.3 cm diameter x 23 cm long), a nitrogen (N) balance was conducted in macroplots (3.85 m x 2.0 m) with N-15 labelled urea, and ammonia volatilization was determined with a mass balance micrometeorological method. Most of the urea was hydrolysed within 4 days irrespective of whether the urea was applied onto dry or wet soil. The nitrification rate was slow at the beginning when the soil was dry, but increased greatly after small amounts of rain; in the 9 days after rain 20% of the N applied was converted to nitrate. In the 40 days between urea application and harvesting, the macroplots the banana plants absorbed only 15% of the applied N; at harvest the largest amounts were found in the leaves (3.4%), pseudostem (3.3%) and fruit (2.8%). Only 1% of the applied N was present in the roots. Sixty percent of the applied N was recovered in the soil and 25% was lost from the plant-soil system by either ammonia volatilization, leaching or denitrification. Direct measurements of ammonia volatilization showed that when urea was applied to dry soil, and only small amounts of rain were received, little ammonia was lost (3.2% of applied N). In contrast, when urea was applied onto wet soil, urea hydrolysis occurred immediately, ammonia was volatilized on day zero, and 17.2% of the applied N was lost by the ninth day after that application. In the latter study, although rain fell every day, the extensive canopy of banana plants reduced the rainfall reaching the fertilized area under the bananas to less than half. Thus even though 90 mm of rain fell during the volatilization study, the fertilized area did not receive sufficient water to wash the urea into the soil and prevent ammonia loss. Losses by leaching and denitrification combined amounted to 5% of the applied N.

Significance of gaseous nitrogen loss from a tropical dairy pasture fertilised with urea

This paper reports a study in the wet tropics of Queensland on the fate of urea applied to a dairy pasture in the absence of grazing animals. A nitrogen balance was conducted in cylindrical plots with N-15-labelled urea, and ammonia volatilisation was determined using a mass balance micrometeorological method. The pasture plants took up 42% of the applied nitrogen in the 98 days between fertiliser application and harvest. At harvest 18% of the applied nitrogen was found in the soil, and 40% was lost from the plant-soil system. The micrometeorological study showed that 20% of the unrecovered nitrogen was lost by ammonia volatilisation. As there was no evidence for leaching or runoff losses it was concluded that the remaining 20% of the applied nitrogen was lost by denitrification. It is evident from these results that fertiliser nitrogen is not being used efficiently on dairy pastures, and that practices need to be changed to conserve fertiliser nitrogen and reduce contamination of the environment.

Effect of leucaena supplementation level, and provision of urea, on utilisation by sheep of Rhodes grass hay

Tarramba leucaena (Leucaena leucocephala cv. Tarramba) foliage had per kilogram dry matter, 169 g protein and 29.8 g condensed tannins. Its value as a supplement, given either with or without urea, to sheep given a low-quality Callide Rhodes grass (Chloris gayana cv. Callide) hay was studied. Six rumen fistulated sheep (mean +/- s.d. liveweight, 34 +/- 1.4 kg) were used to compare 6 dietary treatments in an incomplete latin square design. Rhodes grass hay was given ad libitum either alone, or with urea 7 g/day (U), or with leucaena 150 g/day (L150), or leucaena with urea (L150U), or leucaena 300 g/day (L300), or leucaena with urea (L300U). Digestible organic matter intake was increased significantly by leucaena supplementation although digestibility of the whole diet did not alter. Rumen fluid ammonia-N was not altered by leucaena supplementation, but was increased by urea. This suggests that Tarramba foliage protein has some resistance to ruminal degradation. Liquid and solids passage rates were not affected by the treatments. Microbial nitrogen supply to the intestine (g/day), and the efficiency of microbial nitrogen synthesis (g/kg organic matter apparently digested in the rumen), were increased by leucaena supplementation (P

Interferon-gamma enhances cytotoxic T lymphocyte recognition of endogenous peptide in keratinocytes without lowering the requirement for surface peptide

Keratinocytes expressing the human papillomavirus (HPV) type 16 E7 protein, as a transgene driven by the K14 promoter, form a murine model of HPV-mediated epithelial cancers in humans. Our previous studies have shown that K14E7 transgenic skin grafts onto syngeneic mice are not susceptible to immune destruction despite the demonstrated presence of a strong, systemic CTL response directed against the E7 protein. Consistent with this finding, we now show that cultured, E7 transgenic keratinocytes (KC) express comparable endogenous levels of E7 protein to a range of CTL-sensitive E7-expressing cell lines but are not susceptible to CTL-mediated lysis in vitro . E7 transgenic and non-transgenic KC are susceptible to conventional mechanisms of CTL-mediated lysis, including perforin and Fas/FasL interaction when an excess of exogenous peptide is provided. The concentration of exogenous peptide required to render a cell susceptible to lysis was similar between KC and other conventional CTL targets (e.g. EL-4), despite large differences in H-2D(b) expression at the cell surface. Furthermore, exposure of KC to IFN-gamma increased H-2D(b) expression, but did not substantially alter the exogenous peptide concentration required to sensitize cells for half maximal lysis. In contrast, the lytic sensitivity of transgenic KC expressing endogenous E7 is modestly improved by exposure to IFN-gamma. Thus, failure of CTL to eliminate KC expressing endogenous E7, and by inference squamous tumours expressing E7, may reflect the need for a sustained, local inflammatory environment during the immune effector phase.