Resonant particle production at hadron colliders

We present a method to compute off-shell effects for processes involving resonant particles at hadron colliders with the possibility to include realistic cuts on the decay products. The method is based on an effective theory approach to unstable particle production and, as an example, is applied to t-channel single top production at the LHC.Comment: 6 pages, to appear in the proceedings of the 9th International Symposium on Radiative Corrections (RADCOR 2009), October 25-30 2009, Ascona, Switzerlan

Hormonal adaptation to acute and chronic hypoxia : the role of brain natriuretic peptide and stress hormones in the diagnosis and etiology of altitude illness

PhD ThesisData was collected in two main phases; 1. A field study undertaken in the Cordillera Real Region of Bolivia. 2. Laboratory investigation of terrestrial, hypobaric and normobaric hypoxia. Phase 1 The aim of phase one of the studies was to investigate the endocrine changes (specifically brain natriuretic peptide (BNP), arginine vasopressin (AVP), cortisol, catecholamine and copeptin) with ascent to high altitude. These changes were investigated during a “real world” trekking expedition to Bolivia. Other potential markers for AMS namely high-sensitivity C reactive protein (hs-CRP), high-sensitivity cardiac troponin T (hs-cTnT) and neutrophil gelatinase associated lipocalin (NGAL) were also studied. The overarching hypothesis was that Acute Mountain Sickness (AMS) would be associated with fluid retention and elevated BNP and that changes in other hormones involved in fluid balance such as AVP, copeptin and cortisol may also reflect AMS. The hypotheses investigated included; That BNP would rise with high altitude (HA) illness and be associated with both AMS and a high pulmonary artery systolic pressure (PASP). That copeptin would accurately reflect changes in AVP at altitude and therefore have utility in future field studies as a surrogate for AVP. That AMS would be associated with either elevated copeptin/AVP or with failure to suppress the copeptin/AVP response to exercise. Inflammation and/or rises in PASP occur with the development of high altitude illness and would lead to a detectable rise in hs-cTnT, NGAL or hs-CRP. The dynamic changes in stress hormones associated with exercise are key in the pathogenesis of altitude illness. The physiological stress of HA would lead to a rise in cortisol. This would contribute to fluid retention and be linked to the development of AMS. There would be no difference between total body water (TBW) measured by single or multifrequency bioimpedance analysis. v Methods: This was an observational study with data collection at sea-level and then subsequently over a 10 day ascent from 3800m to 5129m. Daily physiological data was collected with more detailed investigation performed at 3833m, 4450m and 5129m. At these altitudes, data was collected post exercise (after the ascent) and at rest (the following day). Venous blood samples were collected for hormonal assays. BNP and NGAL were analysed in situ using point of care testing technology. Assessment of TBW was performed using bioimpedance devices and pulmonary artery systolic pressure (PASP) was estimated using transthoracic echocardiography. Results and implications: 50 subjects were recruited to the study, 48 of whom were studied at 3833m and 4450m with 47 subjects studied at 5129m. Results presented as mean (range, SD) unless otherwise stated. Significant findings were: Oxygen saturations fell with ascent to altitude to a nadir of 79% (SD 4.4., range 68-88) at 5129m. Fluid balance showed no significant change with altitude or relation to AMS. Plasma osmolality did not change with ascent. AVP and copeptin did not increase until extreme altitude (5129m) and both increased by a greater degree in those recording higher levels of perceived exertion. This was despite no change in osmolality which suggests a non-osmotic stimulus to their secretion. Cortisol secretion increased at 5129m and may support the possibility that the rise in copeptin and AVP was related to physiological stress at extreme altitude. Plasma normetanephrine increased with increasing altitude reaching a maximum of 1423.72 (786.0, 355–4159 pmol/L) at 5129m. Thirst proved difficult to quantify and the visual analogue scale used showed no correlation with total body water, osmolality or AVP. BNP (and NT-proBNP) increased with increasing severity of AMS as assessed by Lake Louise Score (LLS). vi BNP (and NT-proBNP) were higher in those with a high PASP. Hs-cTnT showed an increase with PASP and but no association with AMS. Hs-CRP showed an increase with altitude but no association with AMS. NGAL showed no association with change in altitude. A consistent finding was an evident separation between subjects recording a low Borg score and those recording a Borg rating consistent with “hard work”. Subjects recording a Borg score > 15 (“hard work”) had higher cortisol, AVP, copeptin and an increased LLS. This led to investigation of an additional hypothesis that a higher rating of perceived exertion will lead to an increase in reported AMS symptoms. This was found to be the case with significantly lower SpO2 at rest, higher heart rates and higher LLS in those reporting a Borg RPE > 15.Defence Medical Service

Does a Ketogenic Diet Have a Place Within Diabetes Clinical Practice? Review of Current Evidence and Controversies

Carbohydrate restriction has gained increasing popularity as an adjunctive nutritional therapy for diabetes management. However, controversy remains regarding the long-term suitability, safety, efficacy and potential superiority of a very low carbohydrate, ketogenic diet compared to current recommended nutritional approaches for diabetes management. Recommendations with respect to a ketogenic diet in clinical practice are often hindered by the lack of established definition, which prevents its capacity to be most appropriately prescribed as a therapeutic option for diabetes. Furthermore, with conflicted evidence, this has led to uncertainty amongst clinicians on how best to support and advise their patients. This review will explore whether a ketogenic diet has a place within clinical practice by reviewing current evidence and controversies

Does a Ketogenic Diet Have a Place Within Diabetes Clinical Practice? Review of Current Evidence and Controversies

Carbohydrate restriction has gained increasing popularity as an adjunctive nutritional therapy for diabetes management. However, controversy remains regarding the long-term suitability, safety, efficacy and potential superiority of a very low carbohydrate, ketogenic diet compared to current recommended nutritional approaches for diabetes management. Recommendations with respect to a ketogenic diet in clinical practice are often hindered by the lack of established definition, which prevents its capacity to be most appropriately prescribed as a therapeutic option for diabetes. Furthermore, with conflicted evidence, this has led to uncertainty amongst clinicians on how best to support and advise their patients. This review will explore whether a ketogenic diet has a place within clinical practice by reviewing current evidence and controversies

CHANGES IN BALANCE AND JOINT POSITION SENSE DURING A 12-DAY HIGH ALTITUDE TREK

The purpose of this study was to investigate changes in postural control and knee joint position sense (KJPS) during a trek to high altitude. Postural control during standing balance and KJPS were measured in 12 participants at sea-level, 3619m, 4600m and 5140m. Total (p = 0.003, d=1.9) and anterior-posterior sway velocity (p= 0.001, d=1.9) during standing balance with eyes open velocity was significantly greater at altitudes of 3619m and 5140m when compared with sea level. Despite a gradual ascent profile, exposure to 3619 m was associated with impairments in postural control. Importantly, these impairments did not worsen at higher altitudes. The present findings should be considered during future trekking expeditions when considering specific strategies to manage impairments in postural control that occur with increasing altitude

Activation of Muscarinic M1 Acetylcholine Receptors Induces Long-Term Potentiation in the Hippocampus

Muscarinic M1 acetylcholine receptors (M1Rs) are highly expressed in the hippocampus, and their inhibition or ablation disrupts the encoding of spatial memory. It has been hypothesized that the principal mechanism by which M1Rs influence spatial memory is by the regulation of hippocampal synaptic plasticity. Here, we use a combination of recently developed, well characterized, selective M1R agonists and M1R knock-out mice to define the roles of M1Rs in the regulation of hippocampal neuronal and synaptic function. We confirm that M1R activation increases input resistance and depolarizes hippocampal CA1 pyramidal neurons and show that this profoundly increases excitatory postsynaptic potential-spike coupling. Consistent with a critical role for M1Rs in synaptic plasticity, we now show that M1R activation produces a robust potentiation of glutamatergic synaptic transmission onto CA1 pyramidal neurons that has all the hallmarks of long-term potentiation (LTP): The potentiation requires NMDA receptor activity and bi-directionally occludes with synaptically induced LTP. Thus, we describe synergistic mechanisms by which acetylcholine acting through M1Rs excites CA1 pyramidal neurons and induces LTP, to profoundly increase activation of CA1 pyramidal neurons. These features are predicted to make a major contribution to the pro-cognitive effects of cholinergic transmission in rodents and humans

Fuel Use during Exercise at Altitude in Women with Glucose–Fructose Ingestion

Purpose: This study compared the co-ingestion of glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at terrestrial high altitude (HA) versus sea level, in women. Method: Five women completed two bouts of cycling at the same relative workload (55% Wmax) for 120 minutes on acute exposure to HA (3375m) and at sea level (~113m). In each trial, participants ingested 1.2 g.min-1 of glucose (enriched with 13C glucose) and 0.6 g.min-1 of fructose (enriched with 13C fructose) before and every 15 minutes during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation and endogenous glucose oxidation derived from liver and muscle glycogen. Results: The rates and absolute contribution of exogenous carbohydrate oxidation was significantly lower at HA compared with sea level (ES>0.99, P<0.024), with the relative exogenous carbohydrate contribution approaching significance (32.6±6.1 vs. 36.0±6.1%, ES=0.56, P=0.059) during the second hour of exercise. In comparison, no significant differences were observed between HA and sea level for the relative and absolute contributions of liver glucose (3.2±1.2 vs. 3.1±0.8%, ES=0.09, P=0.635 and 5.1±1.8 vs. 5.4±1.7 grams, ES=0.19, P=0.217), and muscle glycogen (14.4±12.2% vs. 15.8±9.3%, ES=0.11, P=0.934 and 23.1±19.0 vs. 28.7±17.8 grams, ES=0.30, P=0.367). Furthermore, there was no significant difference in total fat oxidation between HA and sea level (66.3±21.4 vs. 59.6±7.7 grams, ES=0.32, P=0.557). Conclusion: In women, acute exposure to HA reduces the reliance on exogenous carbohydrate oxidation during cycling at the same relative exercise intensity

The Effects of Sex on Cardiopulmonary Responses to Acute Normobaric Hypoxia

Background: Acute hypoxia leads to a number of recognized changes in cardiopulmonary function, including acute increase in pulmonary artery systolic pressure. However, the comparative responses between men and women have been barely explored.Fourteen young healthy adult Caucasian subjects were studied at sea-level rest and then after >150-minute exposure to acute normobaric hypoxia (NH) equivalent to 4800 m and again at sea-level rest at 2 hours post-NH exposure. Cardiac function, using transthoracic echocardiography, physiological variables, and Lake Louise Scores for acute mountain sickness (AMS) were collected.All subjects completed the study, and there was an equal balance of men (n = 7) and women (n = 7) who were well matched for age (25.9 ± 3.2 vs. 27.3 ± 4.4; p = 0.51). NH exposure led to a significant increase in AMS scores and heart rate, as well as a fall in oxygen saturation, systolic blood pressure, and stroke volume. Stroke volumes and cardiac output were overall significantly higher in men than in women, and acute NH heart rate was higher in women (80.3 ± 10.2 vs. 69.7 ± 10.7/min; p < 0.05). NH led to a significant fall in the estimated left ventricular filling pressure (E/E'), an increase in the septal A' and S' and septal and lateral isovolumic contractile velocities (ICVs), and a fall in the E'A'S' ratio. The mitral E, lateral ICV, and E' velocities were all higher in men. Acute NH led to a significant increase in right ventricular systolic pressure and pulmonary vascular resistance. There was no interaction between NH exposure and sex for any parameters measured.Despite several baseline differences between men and women, the cardiopulmonary effects of acute NH are consistent between men and women