A class of recursive optimal stopping problems with applications to stock trading

In this paper we introduce and solve a class of optimal stopping problems of recursive type. In particular, the stopping payoff depends directly on the value function of the problem itself. In a multi-dimensional Markovian setting we show that the problem is well posed, in the sense that the value is indeed the unique solution to a fixed point problem in a suitable space of continuous functions, and an optimal stopping time exists. We then apply our class of problems to a model for stock trading in two different market venues and we determine the optimal stopping rule in that case.Comment: 35 pages, 2 figures. In this version, we provide a general analysis of a class of recursive optimal stopping problems with both finite-time and infinite-time horizon. We also discuss other application

Blood flow measurements in rats using four color microspheres during blockade of different vasopressor systems

The use of colored microspheres to adequately evaluate blood flow chancres under different circumstances in the same rat has been validated with a maximum of three different colors due to methodological limitations. the aim of the present study was to validate the use of four different colors measuring four repeated blood flow. changes in the same rat to assess the role of vasopressor systems in. controlling arterial pressure (AP). Red (150,000), white (200,000)), yellow (150,000), and blue (200,000) colored microspheres were infused into the left ventricle of 6 male Wistar rats 1) at rest and 2) after vasopressin (aAVP, 10 mug/kg, iv), 3) renin-angiotensin (losartan, 10 ms/kg iv), and 4) sympathetic system blockade (hexamethonium., 20 mg/kg, iv) to determine blood flow changes. AP was recorded and processed with a data acquisition system (1-kHz sampling frequency). Blood flow changes were quantified by spectrophotometry absorption peaks for colored microsphere components in the tissues evaluated. Administration of aAVP and losartan slightly reduced the AP (-5.7 +/- 0.5 and -7.8 +/- 1.2 mmHg, respectively), while hexamethonium induced a 52 +/- 3 mmHg fall in AP. the aAVP injection increased blood flow in lungs (78%), liver (117%) and skeletal muscle (>150%), while losartan administration enhanced blood flow in heart (126%), lungs (100%), kidneys (80%), and gastrocnemius (75%) and soleus (94%) muscles. Hexamethonium administration reduced only kidney blood flow (50%). in conclusion, four types of colored microspheres can be used to perform four repeated blood flow measurements in the same rat detecting small alterations such as changes in tissues with low blood flow.Univ São Paulo, Fac Med, Inst Coracao, Unidade Hipertensao, BR-05403000 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Nefrol, São Paulo, BrazilUniv Santo Amaro, UNIPESQ, Santo Amaro, SP, BrazilUniv Sao Judas Tadeu, Lab Movimiento Humano, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Nefrol, São Paulo, BrazilWeb of Scienc

Cardiovascular control in experimental diabetes

Several studies have reported impairment in cardiovascular function and control in diabetes. The studies cited in this review were carried out from a few days up to 3 months after streptozotocin administration and were concerned with the control of the circulation. We observed that early changes (5 days) in blood pressure control by different peripheral receptors were maintained for several months. Moreover, the impairment of reflex responses observed after baroreceptor and chemoreceptor stimulation was probably related to changes in the efferent limb of the reflex arc (sympathetic and parasympathetic), but changes also in the central nervous system could not be excluded. Changes in renal sympathetic nerve activity during volume expansion were blunted in streptozotocin-treated rats, indicating an adaptive natriuretic and diuretic response in the diabetic state. The improvement of diabetic cardiovascular dysfunction induced by exercise training seems to be related to changes in the autonomic nervous system. Complementary studies about the complex interaction between circulation control systems are clearly needed to adequately address the management of pathophysiological changes associated with diabetes.Universidade de Santo Amaro UNIPESQ Laboratório de CardiovascularUniversidade Federal do Rio Grande do Sul Instituto de Ciências Básicas da Saúde Departamento de FisiologiaInstituto de Cardiologia do Rio Grande do Sul Fundação Universitária de CardiologiaUniversidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Departamento de NefrologiaUniversidade de São Paulo Faculdade de Medicina Hospital das ClínicasPontifícia Universidade Católica do Rio Grande do Sul FAENFI Curso de FisioterapiaUNIFESP, EPM, Depto. de NefrologiaSciEL

Efeito de um anticoncepcional hormonal oral de baixa dose na função endotelial venosa em mulheres jovens saudáveis: resultados preliminares

BACKGROUND: A possible increase in the incidence of venous thromboembolic events has been reported among users of third generation oral contraceptives. The objective of this study was to evaluate the effect of a low dose oral contraceptive (15 µg ethinyl estradiol/60 µg gestodene) on the venous endothelial function of healthy young women. METHODS: Prospective case control study using the dorsal hand vein technique. Venous endothelial function was evaluated at baseline and after 4 months in the oral contraceptive users group (11 women) and in a control group (9 women). After preconstriction of the vein with phenylephrine, dose-response curves for acetylcholine and sodium nitroprusside were constructed. RESULTS: In the contraceptive users group, a reduction occurred in the maximum venodilation response to acetylcholine and sodium nitroprusside after 4 months of oral contraceptive use, but this difference was not statistically significant (P >; 0.05). No significant changes were detected in maximum venodilation responses to acetylcholine and sodium nitroprusside at the 4-month time point in the control group. CONCLUSION: This study found no significant impairment of endothelium-dependent or independent venodilation in healthy young women following oral contraceptive use. Further studies are necessary using the same methodology in a larger sample over a longer follow-up period.Um aumento no risco de tromboembolismo venoso têm sido descrito em usuárias de anticoncepcionais hormonais oral de terceira geração. OBJETIVO: Avaliar o efeito de um anticoncepcional combinado hormonal oral de baixa dose (15 µg etinil estradiol/60 µg gestodeno) na função endotelial venosa de mulheres jovens saudáveis. MÉTODOS: Realizou-se um estudo caso-controle prospectivo em vinte mulheres jovens saudáveis que foram avaliadas pela técnica da complascência venosa. A função endotelial venosa foi avaliada em um momento basal e após 4 meses no grupo das usuárias de anticoncepcional oral (11 mulheres) e em um grupo controle (9 mulheres). Foram construídas curvas dose resposta para acetilcolina e nitroprussiato de sódio após a pré-constrição da veia com fenilefrina. RESULTADOS: No grupo de usuárias de anticoncepcional combinado hormonal oral houve diminuição da venodilatação máxima em resposta a acetilcolina e nitroprussiato de sódio, porém esta mudança não foi estatisticamente significante (p>; 0,05). No grupo controle não foram detectadas mudanças significantes na venodilatação máxima, em resposta a acetilcolina e nitroprussiato de sódio no intervalo de 4 meses. CONCLUSÃO: Este estudo não observou redução significante da venodilatação endotélio dependente e independente após os uso de anticoncepcional combinado hormonal oral. Mais estudos são necessários utilizando a mesma metodologia em uma amostra maior e com maior tempo de seguimento

Preventive role of exercise training in autonomic, hemodynamic, and metabolic parameters in rats under high risk of metabolic syndrome development

Preventive role of exercise training in autonomic, hemodynamic, and metabolic parameters in rats under high risk of metabolic syndrome development. J Appl Physiol 114: 786-791, 2013. First published January 17, 2013; doi:10.1152/japplphysiol.00586.2012.-High fructose consumption contributes to metabolic syndrome incidence, whereas exercise training promotes several beneficial adaptations. in this study, we demonstrated the preventive role of exercise training in the metabolic syndrome derangements in a rat model. Wistar rats receiving fructose overload in drinking water (100 g/l) were concomitantly trained on a treadmill (FT) or kept sedentary (F) for 10 wk. Control rats treated with normal water were also submitted to exercise training (CT) or sedentarism (C). Metabolic evaluations consisted of the Lee index and glycemia and insulin tolerance test (kITT). Blood pressure (BP) was directly measured, whereas heart rate (HR) and BP variabilities were evaluated in time and frequency domains. Renal sympathetic nerve activity was also recorded. F rats presented significant alterations compared with all the other groups in insulin resistance (in mg.dl(-1).min(-1): F: 3.4 +/- 0.2; C: 4.7 +/- 0.2; CT: 5.0 +/- 0.5 FT: 4.6 +/- 0.4), mean BP (in mmHG: F: 117 +/- 2; C: 100 +/- 2; CT: 98 +/- 2; FT: 105 +/- 2), and Lee index (in g/mm: F = 0.31 +/- 0.001; C = 0.29 +/- 0.001; CT = 0.27 +/- 0.002; FT = 0.28 +/- 0.002), confirming the metabolic syndrome diagnosis. Exercise training blunted all these derangements. Additionally, FS group presented autonomic dysfunction in relation to the others, as seen by an similar to 50% decrease in baroreflex sensitivity and 24% in HR variability, and increases in sympathovagal balance (140%) and in renal sympathetic nerve activity (45%). These impairments were not observed in FT group, as well as in C and CT. Correlation analysis showed that both Lee index and kITT were associated with vagal impairment caused by fructose. Therefore, exercise training plays a preventive role in both autonomic and hemodynamic alterations related to the excessive fructose consumption.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Univ São Paulo, Sch Med, Heart Inst InCor, Hypertens Unit, BR-05403900 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Nephrol, São Paulo, BrazilNove Julho Univ, São Paulo, BrazilUniv Prebiteriana Mackenzie, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Nephrol, São Paulo, BrazilWeb of Scienc

Moderate exercise training promotes adaptations in coronary blood flow and adenosine production in normotensive rats

OBJECTIVES: Aerobic exercise training prevents cardiovascular risks. Regular exercise promotes functional and structural adaptations that are associated with several cardiovascular benefits. The aim of this study is to investigate the effects of swimming training on coronary blood flow, adenosine production and cardiac capillaries in normotensive rats. METHODS: Wistar rats were randomly divided into two groups: control (C) and trained (T). An exercise protocol was performed for 10 weeks and 60 min/day with a tail overload of 5% bodyweight. Coronary blood flow was quantified with a color microsphere technique, and cardiac capillaries were quantified using light microscopy. Adenine nucleotide hydrolysis was evaluated by enzymatic activity, and protein expression was evaluated by western blot. The results are presented as the means ± SEMs (p<0.05). RESULTS: Exercise training increased the coronary blood flow and the myocardial capillary-to-fiber ratio. Moreover, the circulating and cardiac extracellular adenine nucleotide hydrolysis was higher in the trained rats than in the sedentary rats due to the increased activity and protein expression of enzymes, such as E-NTPDase and 59- nucleotidase. CONCLUSIONS: Swimming training increases coronary blood flow, number of cardiac capillaries, and adenine nucleotide hydrolysis. Increased adenosine production may be an important contributor to the enhanced coronary blood flow and angiogenesis that were observed in the exercise-trained rats; collectively, these results suggest improved myocardial perfusion

Aerobic training is better than resistance training on cardiac function and autonomic modulation in female ob/ob mice

This study evaluated the effects of aerobic, resistance, and combined exercise training on cardiac function and autonomic modulation in female ob/ob mice. Methods: Four-week-old female wild type and obese (ob/ob) mice were divided into five groups (n = 8): control (WT), obese (OB) obese + aerobic training (OBA), obese + resistance training (OBR), and obese + combined training (OBC). The exercise training was performed on treadmill and/or ladder at 40-60% maximum test during 8 weeks. Cardiac function was measured using echo machine. Heart rate variability (HRV) was evaluated in the time and frequency domain. Results: OB group presented higher body weight gain (similar to 600%), glycemia (similar to 44%) and glucose intolerance (similar to 150%), reduction of cardiac vagal modulation, evidenced by a lower RMMSD (similar to 56%), total power and high frequency band, and a higher isovolumic relaxation time (IVRT) (similar to 24%) in relation to the WT group. Aerobic and combined training led to a lower IVRT (OBA: similar to 14%; OBC: similar to 14%) and myocardial global index (OBA: similar to 37%; OBC: similar to 44%). The OBA group presented an increased in vagal indexes of HRV than the other ob/ob groups. A negative correlation was observed between the delta of aerobic exercise capacity and MPI (r = 0.45; p = 0.002) and exercise capacity and body weight gain (r = 0.39; p = 0.002). Conclusion: Only the obese females underwent to aerobic exercise training showed improvement in cardiac function and HRV. Moreover, the aerobic exercise capacity as well as a greater responsivity to aerobic exercise training is intimately associated with these improvements, reinforcing the importance of aerobic exercise training to this population10CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP427892/2018-0; 457200/2014-6; 401781/2012-7; 479076/2012-0; 563961/2010-4; 307138/2015-1; 307833/2017-8; 309684/2016-199999.008874/20142018/19006-2; 2018/17183-4; 2015/11223-6; 2011/15828-9; 2010/17188-

Dynamic resistance training improves cardiac autonomic modulation and oxidative stress parameters in chronic stroke survivors : a randomized controlled trial

Stroke survivors are at substantial risk of recurrent cerebrovascular event or cardiovascular disease. Exercise training offers nonpharmacological treatment for these subjects; however, the execution of the traditional exercise protocols and adherence is constantly pointed out as obstacles. Based on these premises, the present study investigated the impact of an 8-week dynamic resistance training protocol with elastic bands on functional, hemodynamic, and cardiac autonomic modulation, oxidative stress markers, and plasma nitrite concentration in stroke survivors. Twenty-two patients with stroke were randomized into control group (CG, n=11) or training group (TG, n=11). Cardiac autonomic modulation, oxidative stress markers, plasma nitrite concentration, physical function and hemodynamic parameters were evaluated before and after 8 weeks. Results indicated that functional parameters (standing up from the sitting position (P=0.011) and timed up and go (P=0.042)) were significantly improved in TG. Although not statistically different, both systolic blood pressure (Delta=-10.41 mmHg) and diastolic blood pressure (Delta=-8.16 mmHg) were reduced in TG when compared to CG. Additionally, cardiac autonomic modulation (sympathovagal balance-LF/HF ratio) and superoxide dismutase were improved, while thiobarbituric acid reactive substances and carbonyl levels were reduced in TG when compared to the CG subjects. In conclusion, our findings support the hypothesis that dynamic resistance training with elastic bands may improve physical function, hemodynamic parameters, autonomic modulation, and oxidative stress markers in stroke survivors. These positive changes would be associated with a reduced risk of a recurrent stroke or cardiac event in these subjects2019CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão temnão tem2017/21320-