Alpha-particle emission probabilities in the decay of 240Pu

Sources of enriched ²⁴⁰Pu were prepared by vacuum evaporation on quartz substrates. High-resolution alpha-particle spectrometry of ²⁴⁰Pu was performed with high statistical accuracy using silicon detectors and with low statistical accuracy using a bolometer. The alpha-particle emission probabilities of six transitions were derived from the spectra and compared with literature values. Additionally, some alpha-particle emission probabilities were derived from γ-ray intensity measurements with a high-purity germanium detector. The alpha-particle emission probabilities of the three main transitions at 5168.1, 5123.6 and 5021.2 keV were derived from seven aggregate spectra analysed with five different fit functions and the results were compatible with evaluated data. Two additional weak peaks at 4863.5 and 4492.0 keV were fitted separately, using the exponential of a polynomial function to represent the underlying tailing of the larger peaks. The peak at 4655 keV could not be detected by alpha-particle spectrometry, while γ-ray spectrometry confirms that its intensity is much lower than expected from literature.     

A magnet system for the suppression of conversion electrons in alpha spectrometry

A new magnet system has been designed and constructed to reduce coincidence effects between alpha particles and conversion electrons in high-resolution alpha-particle spectrometry. By means of a magnetic field, the conversion electrons are deflected away from the PIPS^® detector. Compared to existing magnet systems, the new system is not restricted to point sources and can accommodate source diameters up to about 30 mm. Two yokes were built, allowing for configurations with 20 mm or 36 mm distance between the magnets. The effectiveness of both configurations is demonstrated by measuring the conversion electron spectrum of a ²³⁷Np source. The magnet system effectively rejects 93 (7)% of electrons up to 85 keV (36 mm) and 90 (9)% of electrons up to 320 keV (20 mm). It has been successfully applied in the alpha-particle spectrometry of the long-lived nuclides ²³⁶U and ²³⁸U, resulting in significant improvement of the accuracy of alpha emission probabilities.     

A 238Pu irradiator for exposure of cultured cells with alpha-radiation: Construction,calibration and dosimetry

An alpha-particle irradiator that can facilitate investigations of alpha-radiation effects on human cells in radiation protection, carcinogenesis and radioimmunotherapy was constructed. The irradiator was based on a 1.3 GBq ²³⁸Pu source, housed in a stainless steel tube flushed with helium. Radiation provided by ²³⁸Pu consists mainly of alpha-particles with energy of 5.5 MeV. The alpha-particle fluence and energy spectra were measured with a silicon semiconductor detector. Monte Carlo simulations were used to estimate the mean number of alpha-particles and the mean absorbed alpha-particle dose to cells for various irradiation times and distances between cells and source. There was a linear dependence between exposure time and alpha-particle fluence for exposure times above 1 s. The alpha-particle activity concentration varied with a factor 2.7 over the source area, while the variation in energy peak position was <4%. At the cell nucleus position and with a distance of 45 mm between the source and the mylar dish surface, the α-fluence was 4.6×10⁴ counts/(mm² s), the average incident α-particle energy was 2.5 MeV and the average linear energy transfer was 167 keV/μm. The average dose rate to the cells, with 5 μm diameter nucleus, was 1.2 Gy/s. The ²³⁸Pu α-particle irradiator is feasible for irradiation of cells and it can be used for studies of both direct effects and bystander effects of alpha-radiation.     

Multi-layer 235UF4–6LiF–Au targets for high-resolution fission fragment measurements

Multi-layer ²³⁵UF₄–⁶LiF–Au targets have been produced by vacuum deposition on thin polyimide foils with an areal density, measured by spectrophotometry, of about 33 µg cm⁻². The foils were first covered with an Au-layer and then, with a second layer of ⁶LiF, both by vapour deposition. The ²³⁵UF₄ layer was prepared by fluoride sublimation. Each deposited mass was characterized separately by means of differential weighing for the Au and ⁶LiF layers and by low-geometry alpha-particle counting for the ²³⁵UF₄ layer. The atomic abundances of the uranium base material have been measured by thermal ionization mass spectrometry. The targets were prepared for measuring fission-fragment emission yields with high mass-resolution.     

Rapid and highly sensitive analysis of benzodiazepines and tandospirone in human plasma by automated on-line column-switching UFLC-MS/MS

A high-throughput method was developed for the detection of 31 benzodiazepine drugs and tandospirone in human plasma by on-line column-switching ultra-fast liquid chromatography-tandem mass spectrometry. Plasma samples (100 μl) spiked with the 32 drugs and oxazepam-d₅ (internal standard) were diluted with 300 μl of 13.3 mM ammonium acetate/acetonitrile (33:67, v/v). After centrifugation and filtration, the clear supernatant was injected directly onto the extraction column (Oasis HLB cartridge column). The following procedure was fully automated. The analytes retained on the extraction column were eluted by backflushing of the extraction column and introduced into an analytical column (SUMIPAX ODS D-Swifter column, 30 mm × 3.0 mm i.d.; particle size 2 μm) by column switching. Quantification was performed by multiple reaction monitoring with positive-ion electrospray ionization. Distinct peaks appeared for each drug and the internal standard on each channel within 7 min, including the extraction time. All drugs spiked into plasma showed recoveries of 83–95%. The regression equations for the 32 drugs showed excellent linearities in the range of 50–2000 pg/ml of plasma and the limits of detection ranged from 20 to 50 pg/ml. The lower and upper limits of quantitation were 50–100 ng/ml and 2000 pg/ml, respectively. Intra- and interday coefficients of variation for none of the drugs were greater than 13.6%. The accuracies of quantitation were 87–112%. The multiple reaction monitoring information-dependent acquisition of enhanced product ions method enabled the quantification and confirmation of diazepam, triazolam, and lorazepam obtained from actual plasma.     

DNA transfer: The role of temperature and drying time

It has previously been shown, and reconfirmed here, that biological material on a substrate will transfer readily upon contact with another substrate when wet but hardly when dry. There is however a paucity of data regarding the speed at which body fluids dry and how this may affect its transfer upon contact. Here we conduct transfer experiments at 4 °C, 22 °C and 40 °C at multiple time points during the drying process. The speed at which blood dries is dependent on the temperature, with the drying process complete within 15–60 min. The percentage of deposited DNA transferred upon contact follows an exponential pattern of decline from soon after deposition, decreasing until the sample is dry. There are no differences in transfer rates upon contact among the different temperature conditions within the first 5 min or after 60 min since deposit, but significant variation occurs between these time points. When considering the likelihood of a proposed scenario that incorporates one or more contact situations it is important to consider the timing of the potential transfer event(s) relative to when the biological sample in question was initially deposited. The results of this study will assist the interpretation and evaluation of alternative scenarios involving transfer of biological substances.     

Studies on time of death estimation in the early post mortem period – Application of a method based on eyeball temperature measurement to human bodies

This paper presents a verification of the thermodynamic model allowing an estimation of the time of death (TOD) by calculating the post mortem interval (PMI) based on a single eyeball temperature measurement at the death scene. The study was performed on 30 cases with known PMI, ranging from 1 h 35 min to 5 h 15 min, using pin probes connected to a high precision electronic thermometer (Dostmann-electronic). The measured eye temperatures ranged from 20.2 to 33.1 °C. Rectal temperature was measured at the same time and ranged from 32.8 to 37.4 °C. Ambient temperatures which ranged from ?1 to 24 °C, environmental conditions (still air to light wind) and the amount of hair on the head were also recorded every time. PMI was calculated using a formula based on Newton’s law of cooling, previously derived and successfully tested in comprehensive studies on pigs and a few human cases. Thanks to both the significantly faster post mortem decrease of eye temperature and a residual or nonexistent plateau effect in the eye, as well as practically no influence of body mass, TOD in the human death cases could be estimated with good accuracy. The highest TOD estimation error during the post mortem intervals up to around 5 h was 1 h 16 min, 1 h 14 min and 1 h 03 min, respectively in three cases among 30, while for the remaining 27 cases it was not more than 47 min. The mean error for all 30 cases was ±31 min. All that indicates that the proposed method is of quite good precision in the early post mortem period, with an accuracy of ±1 h for a 95% confidence interval. On the basis of the presented method, TOD can be also calculated at the death scene with the use of a proposed portable electronic device (TOD-meter).     

Influence of carbohydrate supplementation on skill performance during a soccer match simulation

ObjectivesThis study investigated the influence of carbohydrate supplementation on skill performance throughout exercise that replicates soccer match-play.DesignExperimentation was conducted in a randomised, double-blind and cross-over study design.MethodsAfter familiarization, 15 professional academy soccer players completed a soccer match simulation incorporating passing, dribbling and shooting on two separate occasions. Participants received a 6% carbohydrate–electrolyte solution (CHO) or electrolyte solution (PL). Precision, success rate, ball speed and an overall index (speed-precision-success; SPS) were determined for all skills. Blood samples were taken at rest, immediately before exercise, every 15 min during exercise (first half: 15, 30 and 45 min; second half: 60, 75 and 90 min), and 10 min into the half time (half-time).ResultsCarbohydrate supplementation influenced shooting (time × treatment interaction: p < 0.05), where CHO attenuated the decline in shot speed and SPS index. Supplementation did not affect passing or dribbling. Blood glucose responses to exercise were influenced by supplementation (time × treatment interaction: p < 0.05), where concentrations were higher at 45 min and during half-time in CHO compared with PL. Blood glucose concentrations reduced by 30 ± 1% between half-time and 60 min in CHO.ConclusionsCarbohydrate supplementation attenuated decrements in shooting performance during simulated soccer match-play; however, further research is warranted to optimise carbohydrate supplementation regimes for high-intensity intermittent sports.     

Comparison of Actical and activPAL measures of sedentary behaviour in preschool children

ObjectivesThe purpose of this study was to examine the convergent validity of the Actical and activPAL to measure sedentary behaviour (SB) and non-SB in preschoolers in a free-living environment.DesignA convenience sample of 49 preschoolers (22 boys; 4.0 ± 0.5 years) from six early childhood centres in Auckland, New Zealand were included in data analysis.MethodsParticipants wore a hip-mounted Actical and a thigh-mounted activPAL accelerometer simultaneously during centre attendance for one day and data were collected in 15 s epochs. Bland–Altman tests were used to assess differences in group mean minutes and percentage of time in (non-)SB between both monitors. Agreement between binary coded (SB vs. non-SB) 15 s-by-15 s Actical and activPAL data was evaluated by calculating percentage agreement and κ statistic.ResultsThe monitors were worn on average for 294.8 ± 46.3 min resulting in a total of 57,780 15 s epochs. Bland–Altman tests suggested a small group mean difference in (non-)SB (1.3 min; 0.1%) and a wide prediction interval (121.3 min; 39.2%). No obvious systematic bias was observed in the Bland–Altman plot. Percentage agreement between the 15 s-by-15 s Actical and activPAL data of all participants was 73.0% (inter-child range: 36.8–93.8%). The κ statistic showed moderate agreement with a value of 0.46 (95% CI: 0.45–0.47).ConclusionsAlthough the group mean estimate of (non-)SB was similar between the Actical and activPAL, the output of both monitors cannot be considered convergent as meaningful random disagreement was found between both monitors.     

Targetry of SrCO3 on a copper substrate by sedimentation method for the cyclotron production no-carrier-added 86Y

Strontium carbonate deposition on copper substrate was carried out by the sedimentation method in order to produce yttrium-86. Natural strontium carbonate thick layer was prepared with 480 mg SrCO₃, 220 mg ethyl cellulose, and 7.5 mL acetone. This optimum condition is a result of several repeated experiments with different amount of ethyl cellulose and acetone. Target quality control was done by SEM photomicrograph and thermal shock test. The deposited target was irradiated at 30 μA current and 15 MeV proton beam for 12 min.     

Assessing the suitability of miRNA-142-5p and miRNA-541 for bloodstain deposition timing

A recent proof-of-concept pilot study proposed using microRNA (miRNA) markers for time of death determination. The markers – miRNA-142-5p and miRNA-541, were reported to show considerable expression differences in vitreous humor between individuals who died during the day or night. Here, we investigated whether these miRNA markers show the same diurnal expression pattern in blood, which would make them useful for estimating bloodstain deposition time to allow molecular alibi testing for forensic casework. We analyzed venous blood samples collected from 12 healthy individuals every 4 h during the 24 h day/night period under controlled sleep-laboratory conditions. MiRNA-142-5p normalized against miRNA-222 showed no statistically significant expression differences between blood samples collected during daytime and nighttime (one-way ANOVA p = 0.81), and also no statistically significant rhythmicity during the 24 h day/night period (cosine fit for all individuals p > 0.05, averaged data p = 0.932). MicroRNA-541 amplification in blood was above the 34-cycle threshold applied in the study, indicating too low quantities for obtaining reliable data. Overall, we conclude that the two miRNA markers previously suggested for time of death determination in vitreous humor are not suitable for estimating the deposition time of forensic bloodstains. Future studies may find out if miRNA markers with significant diurnal expression patterns can be identified and how useful they would be for forensic trace deposition timing.     

Effect of stage duration on maximal heart rate and post-exercise blood lactate concentration during incremental treadmill tests

ObjectivesThis study compared the responses during maximal incremental treadmill tests of 1-min, 2-min, and 3-min stage durations mainly in terms of maximal heart rate (HR_max) and peak blood lactate concentration (LA_peak).DesignRepeated-measures.MethodsThirty-four male, recreational, endurance-trained runners (40 ± 13 years) performed three tests on a motorized treadmill. The tests started at 8 km h^?1 with increments of 1 km h^?1 every 1 min for the short-stage protocol, every 2 min for the intermediate-stage protocol, and every 3 min for the long-stage protocol. LA_peak was defined for each subject as the highest value among the lactate concentrations determined at the end of each test and at the third, fifth and seventh minutes after test, during passive recovery.ResultsAnalysis of variance revealed a significant effect of the stage duration on the HR_max (p = 0.003) and LA_peak (p = 0.001). The HR_max was higher in the intermediate-stage compared to the short-stage protocol (184.8 ± 12.7 vs. 181.8 ± 12.1 beats min^?1, p < 0.001), but no significant differences were found between the long-stage (183.1 ± 12.1 beats min^?1) and the intermediate-stage or short-stage protocols (p > 0.05). The LA_peak was lower in the long-stage compared to the short-stage and intermediate-stage protocols (7.9 ± 2.2 vs. 9.4 ± 2.2 and 9.2 ± 1.9 mmol L^?1, respectively, p < 0.05). Further, blood lactate reached peak concentration at the fifth minute after test for all the protocols.ConclusionsThus, HR_max and LA_peak depend on the stage duration of the incremental test, but the moment at which blood lactate reaches peak concentration is independent of the duration. Further, we suggest 2-min stage duration protocols to determine HR_max.     

Influence of post-warm-up recovery time on swim performance in international swimmers

ObjectivesSwimmers must enter a marshalling call-room 20 min prior to racing, which results in some swimmers completing their warm-up 45 min pre-race. Since a recovery period longer than 15–20 min may prove problematic, this study examined 200 m freestyle performance after a 20 and 45 min post-warm-up recovery period.DesignEight international swimmers completed this randomised and counter-balanced study.MethodsAfter a standardised warm-up, swimmers rested for either 20 (20 min) or 45 min (45 min) prior to completing a 200 m freestyle time-trial (TT). Core temperature (T_core), blood lactate (BL), heart rate and rate of perceived exertion (RPE) were recorded at baseline, post-warm-up, pre-TT, immediately post-TT and at 3 min post-TT.ResultsT_core was similar after the warm-up under both conditions, however, at pre-TT T_core was greater under 20 min (mean ± SD; 20 min 37.8 ± 0.2 vs. 45 min 37.5 ± 0.2 °C; P = 0.002). BL was similar between conditions at all-time points before the TT (P > 0.05). Swimmers demonstrated a 1.5 ± 1.1% improvement in performance under 20 min (20 min 125.74 ± 3.64 vs. 45 min 127.60 ± 3.55 s; P = 0.01). T_core was similar between conditions at immediately post-TT and 3 min post-TT (P > 0.05), however, BL was higher at these time points under 20 min (P < 0.05). Heart rate and RPE were similar between conditions at all-time points (P > 0.05).Conclusions200 m freestyle performance is faster 20 min post-warm-up when compared to 45 min probably due to better T_core maintenance. This has implications for swim race preparation as warm-up procedures should be completed close to entering the pre-race call room, in order to maintain elevated core temperature.     

Experimental drowning lung images on postmortem CT – Difference between sea water and fresh water

PurposeExperimental drowning models were prepared to investigate the time-related course of lung changes using postmortem CT. This study was approved by our institutional animal ethics committee.Materials and methodsFifteen NZW rabbits (female fifteen, 2.6–4.3 (mean 3.3) kg) were divided into 3 groups: fresh water drowning (FRESH), sea water drowning (SEA), and sea water drowning with anterior chest compression (ACC). All individuals were examined by CT (Aquilion CX, Toshiba, Japan) on postmortem time course. The rabbit’s head was submerged in a water bath for a total of 10 min. In ACC, cardiopulmonary resuscitation was performed for 2 min, additionally. The percentage of aerated lung volumes (%ALV = 100 (aerated lung volume/total lung volume)) were statistically evaluated and the lung CT image patterns and pleural fluid appearance time were investigated.ResultsAll lungs had decreased their %ALV within 24 h, and there were no statistical differences in and among the 3 groups. After 36 h, %ALV tended to increase in all groups, and only ACC presented a statistical difference between 1 h and 36 h (p < 0.005).On postmortem lung CT, all lungs presented ground-glass opacity with interstitial thickening spread pattern (100%) and no pattern change during the follow-up period. After presenting pleural space fluid collection, the %ALV tended to increase.ConclusionThere were no differences among FRESH, SEA, and ACC in %ALV within 24 h. Only ground-glass opacity could be detected on postmortem lung CT, experimentally.     

Ultra low-dose of gadobenate dimeglumine for late gadolinium enhancement (LGE) imaging in acute myocardial infarction: A feasibility study

PurposeTo assess the feasibility of using an ultra-low dose (0.05 mmol/kg of body weight [BW]) of high relaxivity contrast agent for late gadolinium enhancement (LGE) imaging in patients with acute myocardial infarction (AMI).Materials and methods17 consecutive patients (mean age, 60.1 ± 10.3 years) with ST-segment elevation AMI underwent two randomized cardiac magnetic resonance studies (exam intervals between 24 and 48 h) on a 1.5 T unit during the first week after the event using gadobenate dimeglumine (Gd-BOPTA) at the dose of 0.1 mmol/kg BW (standard dose or SD group) and 0.05 mmol/kg BW (half dose or HD group). Image quality was qualitatively assessed. Quantitative analysis of LGE were performed by measuring signal intensity (SI), signal-to-noise ratio (SNR) in the infarcted myocardium (IM), non-infarcted myocardium (N-IM) and left ventricular cavity (LVC) in images acquired at 1, 3, 5, 10, 15 and 20 min after administration of Gd-BOPTA using both contrast media protocol. Contrast-to-noise ratio (CNR) between IM and N-IM (CNR IM/N-IM) and between IM and LVC (CNR IM/LVC) were also quantified for each time point. Moreover the extent of infarcted myocardium was measured.Results102 LGE images were evaluated for each dose group. Quality score was significantly higher for SD at 1, 15 and 20 min (0.002 < p < 0.046) and for HD at 5 min (p = 0.013). SNR has been higher in the SD group compared to the HD group even though not statistically significant at any time-point for both IM (SD vs. HD: 87.7 ± 73 vs. 65 ± 66; 0.15 < p < 0.38) and N-IM (SD vs. HD: 22 ± 61 vs. 9.9 ± 6.5; 0.09 < p < 0.43). LVC SNR was significantly higher with SD at 10 min (p = 0.03), 15 min (p = 0.001) and 20 min (p = 0.004). CNR between the IM and N-IM was significantly higher using SD compared to HD (1382.24 ± 1049 vs. 695.4 ± 500; 0.000 < p < 0.028) at 10, 15 and 20 min. No significant differences in CNR IM/LVC were noted for HD acquired 5 min after CM administration compared to SD acquired at 10 (p = 0.34), 15 (p = 0.96) and 20 (p = 0.41) min, and between HD at 10 min compared to SD acquired at 15 min (p = 0.78) and 20 min (p = 0.32). Good correlation between SD and HD (0.56 < r² < 0.85, p < 0.024) was found at all time-points in the measuring of IA.ConclusionThe use of a 0.05 mmol/kg dose of gadobenate dimeglumine is feasible for LGE imaging of acute MI and the best image quality is obtained at 5 min after contrast administration. It could be beneficial in patient with renal failure and a solution to improve the identification of subendocardial infarction reducing examination time, costs and total gadolinium load. However, the standard dose of 0.1 mmol/kg provides overall better image quality, with the best performance obtained at the delay of 10 min or more after Gd-BOPTA administration, and it should be routinely preferred.     

Dose-response between frequency of breaks in sedentary time and glucose control in type 2 diabetes: A proof of concept study

ObjectivesThis study aimed to investigate dose-response between frequency of breaks in sedentary time and glucose control.DesignRandomised three-treatment, two-period balanced incomplete block trial.MethodsTwelve adults with type 2 diabetes (age, 60 ± 11 years; body mass index, 30.2 ± 4.7 kg/m²) participated in two of the following treatment conditions: sitting for 7 h interrupted by 3 min light-intensity walking breaks every (1) 60 min (Condition 1), (2) 30 min (Condition 2), and (3) 15 min (Condition 3). Postprandial glucose incremental area under the curves (iAUCs) and 21-h glucose total area under the curve (AUC) were measured using continuous glucose monitoring. Standardised meals were provided.ResultsCompared with Condition 1 (6.7 ± 0.8 mmol L⁻¹ × 3.5 h⁻¹), post-breakfast glucose iAUC was reduced for Condition 3 (3.5 ± 0.9 mmol L⁻¹ × 3.5 h⁻¹, p ˂ 0.04). Post-lunch glucose iAUC was lower in Condition 3 (1.3 ± 0.9 mmol L⁻¹ × 3.5 h⁻¹, p ˂ 0.03) and Condition 2 (2.1 ± 0.7 mmol L⁻¹ × 3.5 h⁻¹, p ˂ 0.05) relative to Condition 1 (4.6 ± 0.8 mmol L⁻¹ × 3.5 h⁻¹). Condition 3 (1.0 ± 0.7 mmol L⁻¹ × 3.5 h⁻¹, p = 0.02) and Condition 2 (1.6 ± 0.6 mmol L⁻¹ × 3.5 h⁻¹, p ˂ 0.04) attenuated post-dinner glucose iAUC compared with Condition 1 (4.0 ± 0.7 mmol L⁻¹ × 3.5 h⁻¹). Cumulative 10.5-h postprandial glucose iAUC was lower in Condition 3 than Condition 1 (p = 0.02). Condition 3 reduced 21-h glucose AUC compared with Condition 1 (p < 0.001) and Condition 2 (p = 0.002). However, post-breakfast glucose iAUC, cumulative 10.5-h postprandial glucose iAUC and 21-h glucose AUC were not different between Condition 2 and Condition 1 (p ˃ 0.05).ConclusionsThere could be dose-response between frequency of breaks in sedentary time and glucose. Interrupting sedentary time every 15 min could produce better glucose control.     

A simple and efficient method of nickel electrodeposition for the cyclotron production of 64Cu

Nickel targets for the cyclotron production of ⁶⁴Cu were prepared by electrodeposition on a gold backing from nickel chloride solutions using boric acid as buffer. Parameters studied were nickel chloride and boric acid concentration, temperature and current density. All plating conditions studied were successful obtaining efficiencies of approximately 90% in 2–3 h, reaching almost quantitative plating (>97%) in 10–20 h depending on the current density. All plated targets withstood proton irradiations up to 40 µA for 2 h. Recovered nickel was successfully recycled and reused with an overall efficiency >95%.     

Simultaneous quantification of batrachotoxin and epibatidine in plasma by ultra-performance liquid chromatography/tandem mass spectrometry

An ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous quantification of batrachotoxin and epibatidine in plasma. Plasma samples were pretreated by liquid-liquid extraction with acetonitrile and methanol. The toxins were separated on a reversed phase C18-column (2.1 mm × 50 mm, 1.7 μm) using a formic acid/acetonitrile gradient elution. Quantification was carried out by mass chromatography with each product ion referenced against midazolam-d₄ as an internal standard (IS). The two toxins and the IS were separated within 2 min. The calibration curves for the two toxins spiked into human plasma showed good linearities in the range from 2.5 to 250 ng/mL. The detection limits were estimated to be 0.5 ng/mL for batrachotoxin and 1 ng/mL for epibatidine with a signal-to-noise ratio of 3:1. Overall recoveries ranged from 69.6% to 98.2%, and no significant matrix effects were observed. The intra- and interday accuracies were 94.7–102.3%, and the precisions were 1.0–10.3%. This method was successfully applied for the quantification of batrachotoxin and epibatidine in rat plasma samples taken after intraperitoneal administration of the toxins. This is the first report to use UPLC-MS/MS to simultaneously quantify batrachotoxin and epibatidine in plasma samples.     

Coinciding exercise with peak serum caffeine does not improve cycling performance

ObjectivesTo investigate whether coinciding peak serum caffeine concentration with the onset of exercise enhances subsequent endurance performance.DesignRandomised, double-blind, crossover.MethodsIn this randomised, placebo-controlled, double-blind crossover study, 14 male trained cyclists and triathletes (age 31 ± 5 year, body mass 75.4 ± 5.7 kg, VO₂max 69.5 ± 6.1 mL kg^?1 min^?1 and peak power output 417 ± 35 W, mean ± SD) consumed 6 mg kg^?1 caffeine or a placebo either 1 h (C_1 h) prior to completing a 40 km time trial or when the start of exercise coincided with individual peak serum caffeine concentrations (C_peak). C_peak was determined from a separate ‘caffeine profiling’ session that involved monitoring caffeine concentrations in the blood every 30 min over a 4 h period.ResultsFollowing caffeine ingestion, peak serum caffeine occurred 120 min in 12 participants and 150 min in 2 participants. Time to complete the 40 km time trial was significantly faster (2.0%; p = 0.002) in C_1 h compared to placebo. No statistically significant improvement in performance was noted in the C_peak trial versus placebo (1.1%; p = 0.240). Whilst no differences in metabolic markers were found between C_peak and placebo conditions, plasma concentrations of glucose (p = 0.005), norepinephrine and epinephrine (p ≤ 0.002) were higher in the C_1 h trial 6 min post-exercise versus placebo.ConclusionsIn contrast to coinciding peak serum caffeine concentration with exercise onset, caffeine consumed 60 min prior to exercise resulted in significant improvements in 40 km time trial performance. The ergogenic effect of caffeine was not found to be related to peak caffeine concentration in the blood at the onset of endurance exercise.