The influence of time-of-day consumption and training status on the ergogenic properties of caffeine

Purpose: The objectives were to determine the effects of time-of-day consumption and training status on the benefits of caffeine supplementation for cycling performance and peak muscle strength. METHODS: Twenty untrained and trained subjects completed four trials consisting of isokinetic peak torque testing and 3-km time trials (TT). Subjects ingested either 6 mg/kg of caffeine or a placebo one hour prior to each trial. Treatments were: morning + placebo, morning + caffeine, evening + placebo, evening + caffeine. Magnitude based inferences were used to evaluate treatment differences. RESULTS: Caffeine (‘very likely’ and ‘likely’) improved 3-km TT performance in the morning and evening. 3-km TT performance was ‘likely’ improved more in the morning than evening for total subject pool and trained subjects. Untrained subjects ‘likely’ benefited more during the 3-km TT from supplementation than trained in both the morning and evening. Caffeine supplementation was ‘likely’ trivial and ‘unclear’ for the majority of peak muscle strength conditions. CONCLUSIONS: Caffeine supplementation improved 3-km TT performance in the morning for trained and untrained, with lesser benefits in the evening, while untrained benefited more than trained. Peak muscle strength was largely unaffected by caffeine supplementation, regardless of time-of-day consumption or training status

Remodelling of human atrial K+ currents but not ion channel expression by chronic β-blockade

Chronic β-adrenoceptor antagonist (β-blocker) treatment in patients is associated with a potentially anti-arrhythmic prolongation of the atrial action potential duration (APD), which may involve remodelling of repolarising K+ currents. The aim of this study was to investigate the effects of chronic β-blockade on transient outward, sustained and inward rectifier K+ currents (ITO, IKSUS and IK1) in human atrial myocytes and on the expression of underlying ion channel subunits. Ion currents were recorded from human right atrial isolated myocytes using the whole-cell-patch clamp technique. Tissue mRNA and protein levels were measured using real time RT-PCR and Western blotting. Chronic β-blockade was associated with a 41% reduction in ITO density: 9.3 ± 0.8 (30 myocytes, 15 patients) vs 15.7 ± 1.1 pA/pF (32, 14), p < 0.05; without affecting its voltage-, time- or rate dependence. IK1 was reduced by 34% at −120 mV (p < 0.05). Neither IKSUS, nor its increase by acute β-stimulation with isoprenaline, was affected by chronic β-blockade. Mathematical modelling suggested that the combination of ITO- and IK1-decrease could result in a 28% increase in APD90. Chronic β-blockade did not alter mRNA or protein expression of the ITO pore-forming subunit, Kv4.3, or mRNA expression of the accessory subunits KChIP2, KChAP, Kvβ1, Kvβ2 or frequenin. There was no reduction in mRNA expression of Kir2.1 or TWIK to account for the reduction in IK1. A reduction in atrial ITO and IK1 associated with chronic β-blocker treatment in patients may contribute to the associated action potential prolongation, and this cannot be explained by a reduction in expression of associated ion channel subunits

A statistical framework to evaluate virtual screening

<p>Abstract</p> <p>Background</p> <p>Receiver operating characteristic (ROC) curve is widely used to evaluate virtual screening (VS) studies. However, the method fails to address the "early recognition" problem specific to VS. Although many other metrics, such as RIE, BEDROC, and pROC that emphasize "early recognition" have been proposed, there are no rigorous statistical guidelines for determining the thresholds and performing significance tests. Also no comparisons have been made between these metrics under a statistical framework to better understand their performances.</p> <p>Results</p> <p>We have proposed a statistical framework to evaluate VS studies by which the threshold to determine whether a ranking method is better than random ranking can be derived by bootstrap simulations and 2 ranking methods can be compared by permutation test. We found that different metrics emphasize "early recognition" differently. BEDROC and RIE are 2 statistically equivalent metrics. Our newly proposed metric SLR is superior to pROC. Through extensive simulations, we observed a "seesaw effect" – overemphasizing early recognition reduces the statistical power of a metric to detect true early recognitions.</p> <p>Conclusion</p> <p>The statistical framework developed and tested by us is applicable to any other metric as well, even if their exact distribution is unknown. Under this framework, a threshold can be easily selected according to a pre-specified type I error rate and statistical comparisons between 2 ranking methods becomes possible. The theoretical null distribution of SLR metric is available so that the threshold of SLR can be exactly determined without resorting to bootstrap simulations, which makes it easy to use in practical virtual screening studies.</p

Characterization and influence of cardiac background sodium current in the atrioventricular node

AbstractBackground inward sodium current (IB,Na) that influences cardiac pacemaking has been comparatively under-investigated. The aim of this study was to determine for the first time the properties and role of IB,Na in cells from the heart's secondary pacemaker, the atrioventricular node (AVN). Myocytes were isolated from the AVN of adult male rabbits and mice using mechanical and enzymatic dispersion. Background current was measured using whole-cell patch clamp and monovalent ion substitution with major voltage- and time-dependent conductances inhibited. In the absence of a selective pharmacological inhibitor of IB,Na, computer modelling was used to assess the physiological contribution of IB,Na. Net background current during voltage ramps was linear, reversing close to 0mV. Switching between Tris- and Na+-containing extracellular solution in rabbit and mouse AVN cells revealed an inward IB,Na, with an increase in slope conductance in rabbit cells at −50mV from 0.54±0.03 to 0.91±0.05nS (mean±SEM; n=61 cells). IB,Na magnitude varied in proportion to [Na+]o. Other monovalent cations could substitute for Na+ (Rb+>K+>Cs+>Na+>Li+). The single-channel conductance with Na+ as charge carrier estimated from noise-analysis was 3.2±1.2pS (n=6). Ni2+ (10mM), Gd3+ (100μM), ruthenium red (100μM), or amiloride (1mM) produced modest reductions in IB,Na. Flufenamic acid was without significant effect, whilst La3+ (100μM) or extracellular acidosis (pH6.3) inhibited the current by >60%. Under the conditions of our AVN cell simulations, removal of IB,Na arrested spontaneous activity and, in a simulated 1D-strand, reduced conduction velocity by ~20%. IB,Na is carried by distinct low conductance monovalent non-selective cation channels and can influence AVN spontaneous activity and conduction

Time of Day and Training Status Both Impact the Efficacy of Caffeine for Short Duration Cycling Performance

This project was designed to assess the effects of time of day and training status on the benefits of caffeine supplementation for cycling performance. Twenty male subjects (Age, 25 years; Peak oxygen consumption, 57 mL·kg−1·min−1) were divided into tertiles based on training levels, with top and bottom tertiles designated as ‘trained’ (n = 7) and ‘untrained’ (n = 7). Subjects completed two familiarization trials and four experimental trials consisting of a computer-simulated 3-km cycling time trial (TT). The trials were performed in randomized order for each combination of time of day (morning and evening) and treatment (6mg/kg of caffeine or placebo). Magnitude-based inferences were used to evaluate all treatment effects. For all subjects, caffeine enhanced TT performance in the morning (2.3% ± 1.7%, ‘very likely’) and evening (1.4% ± 1.1%, ‘likely’). Both untrained and trained subjects improved performance with caffeine supplementation in the morning (5.5% ± 4.3%, ‘likely’; 1.0% ± 1.7%, ‘likely’, respectively), but only untrained subjects rode faster in the evening (2.9% ± 2.6%, ‘likely’). Altogether, our observations indicate that trained athletes are more likely to derive ergogenic effects from caffeine in the morning than the evening. Further, untrained individuals appear to receive larger gains from caffeine in the evening than their trained counterparts

A comparative study of the long term psychosocial functioning of childhood acute lymphoblastic leukemia survivors treated by intrathecal methotrexate with or without cranial radiation

BACKGROUND: Although previous research has delineated medical, cognitive, and neuropsychologic late effects of central nervous system (CNS) prophylaxis for childhood acute lymphoblastic leukemia (ALL), it has been difficult to draw conclusions about the long term psychosocial sequelae of these treatments due to methodologic problems that led to inconclusive results in past studies. In the current study, the authors examined the long term psychosocial functioning of childhood ALL survivors who had been treated on a Phase III clinical protocol (Cancer and Leukemia Group B [CALGB] 7611) between 1976 and 1979, in which they were randomized to receive either 2400 centigray of cranial radiation (CRT) with intrathecal methotrexate (IT-MTX) or intermediate dose systemic methotrexate (IV-MTX) with IT-MTX. METHODS: One hundred ten survivors of childhood ALL (mean age, 20.8 years) treated on CALGB 7611 who were age 14 years or older and disease free for at least 1 year were studied a mean of 14.7 years after their entry on CALGB 7611. In a telephone interview, a psychosocial assessment battery was administered to the patients, consisting of measures that assessed psychologic, sexual, social, and vocational functioning as well as any delayed physical effects. RESULTS: Survivors who had received CRT + IT-MTX had significantly poorer academic achievement (P = 0.0001), poorer self-images with regard to their bodies (P = 0.001), and greater psychologic distress (P = 0.005). CONCLUSIONS: Cranial radiation used to treat children with ALL has significant long term sequelae in terms of poorer academic achievement and psychosocial functioning. These data add weight to the conclusion that CRT prophylaxis should only be used to treat children who are at high risk of CNS relapse

Trial design: The St. Jude Children's Research Hospital Cancer Survivors Tobacco Quit Line study

Nearly, one-fifth of childhood cancer survivors (CCSs) smoke cigarettes. Because CCSs are already at greater medical smoking-related risks, targeting them for smoking cessation efforts is a high priority. One of the major challenges with smoking cessation in CCSs is how to reach such a geographically dispersed population. This study aims to demonstrate that these challenges can be overcome through the use of telephone-based tobacco quit lines (QLs). This report describes the design of the St. Jude Cancer Survivor Tobacco QL study, which is a randomized controlled clinical trial that will examine the long-term (1-year) efficacy of a counselor initiated vs. participant initiated tobacco QL with adjunctive nicotine replacement therapy (NRT) in both groups. Participants ( N = 950) will be recruited nationally and randomly assigned to one of the two interventions. The counselor initiated intervention includes six scheduled telephone sessions of a behavioral intervention and provision of 8 weeks of NRT. The participant initiated intervention allows the participant to call the QL at their convenience, but includes the same six telephone sessions and provision of 2 weeks of NRT. Both groups will receive two follow-up phone calls at 8 weeks and 1 year after enrollment to assess their smoking status. The primary outcome measure is cotinine-validated self-reported smoking abstinence at 1-year follow-up. Results from this study will provide the first evidence about the efficacy of intensive QL cessation intervention in this high-risk population. Such evidence can lead as well to the dissemination of this intervention to other medically compromised populations

Outcome and prognostic factors for children with supratentorial primitive neuroectodermal tumors treated with carboplatin during radiotherapy: A report from the Children\u27s Oncology Group.

BACKGROUND: Supratentorial PNETs (sPNET) are uncommon embryonal malignancies of the central nervous system whose prognosis has historically been poor. We evaluated the outcome and prognostic factors of children with sPNET treated prospectively on a Children’s Oncology Group trial. PROCEDURE: Following surgery, patients received craniospinal radiotherapy with concurrent carboplatin followed by six months of maintenance chemotherapy with cyclophosphamide and vincristine. RESULTS: Five-year overall survival (OS) and progression-free survival (PFS) for all patients was 58 ±7% and 48 ±7%. For patients with pineoblastoma (n=23), five-year OS and PFS was 81 ± 9% and 62 ± 11%. Extent of resection but not M-stage was prognostic. Five-year OS and PFS for 37 patients with non-pineal tumors (NPsPNET) was 44 ± 8% and 39 ± 8%, significantly worse than for PB (p=0.055 and 0.009 respectively). Extent of resection and major radiotherapy deviations were prognostic. Five year OS was 59 +/− 11.4% for those undergoing complete resection versus 10.4 +/− 7% for those who did not (p=0.017). Central pathologic review called 14 (38%) “classic” sPNET, 8 (22%) "undifferentiated” and 13 (35%) “malignant gliomas”. There was no significant difference between the subgroups, although survival distributions approached significance when the combined “classic” and “undifferentiated” group was compared to the “malignant gliomas”. CONCLUSIONS: Carboplatin during RT followed by 6 months of non-intensive chemotherapy is a feasible treatment strategy for patients with sPNET. Aggressive surgical resection should be attempted if feasible. The classification of supratentorial small cell malignancies can be difficult