Kinetics of cerebral blood flow in the moderate and heavy exercise intensity domains estimated using the transcranial Doppler method

Purpose: The purpose of this study was to investigate the kinetics of cerebral blood flow (CBF) in conjunction with cardiopulmonary response during constant-work rate cycling exercise of moderate and heavy intensities. Methods: Seven subjects (6 males and 1 female; age, 25.4 ± 7.7 yr; height, 171.9 ± 4.3 cm; body mass, 67.7 ± 11.4 kg) participated in the present study. The subjects completed incremental cycle ergometer test to assess VO2peak, the gas exchange threshold (GET), and the respiratory compensation threshold (RCT). Secondary, the subjects performed two sets of constant workload of exercise bouts (10 min) by cycle ergometer corresponding to the level of 10% below GET (moderate intensity) and RCT (heavy intensity). Respiratory gas analysis and the middle cerebral blood flow mean velocity (MCA Vmean) were measured simultaneously using the transcranial Doppler (TCD) method. PaCO2 was estimated (ePaCO2) using PETCO2 and VT. We assumed that MCA Vmean could be used as an index of the global CBF. Results: VO2 and ePaCO2 remained stable after the onset at moderate intensity whereas VO2 increased throughout the trail and ePaCO2 decreased after the onset at heavy intensity. The percentage change from baseline for MCA Vmean (ΔMCA Vmean) increased within 2 min to a peak value within 2 min by 32.8 ± 9.1% and 31.8 ± 11.8% at moderate and heavy intensity, respectively. In the heavy-intensity exercise ΔMCA Vmean decreased further below the response to moderate exercise as time progressed prior to the recovery phase (trials × time: F = 3.84, P < 0.05). Conclusion: The different kinetics of MCA Vmean between moderate and heavy-intensity exercise was identified during a constant work rate cycling exercise. We found that in heavy-intensity trials, the relationship between ePaCO2 and MCA Vmean was different to that at moderate intensity during the recovery phase

Cerebrovascular response to CO2 during moderate-intensity exercise measured by performing transcranial Doppler Ultrasonography

Previous studies demonstrated that cerebral blood flow (CBF) changes during dynamic exercise and a physiological basis for this observation may be explained by the tight control of CBF by arterial carbon dioxide tension (PaCO?). This study examined whether the steady state of the middle cerebral artery blood flow velocity (MCAVmean) and PaCO?could be observed during constant work rate cycling exercise and to investigate the cerebrovascular reactivity (CVR) to CO?. Seven young volunteers performed a 10-min exercise session with constant workload using a cycle ergometer, with intensities corresponding to the level below the lactate threshold. Respiratory gas analysis and MCAVmean were measured simultaneously using the transcranial Doppler (TCD) method. PaCO?was estimated (ePaCO?) using the end-tidal pressure of CO?(PETCO?) and the tidal volume (VT). On-transient phase II of VO?and the corresponding responses of MCAVmean and ePaCO? were investigated simultaneously with the monoexponential model. Since the responses in ΔMCAVmean or ePaCO?had the overshoot phase within 3min in some cases, analysis for the fitted curves of the monoexponential model was performed during the first 5 min as well as during the total 10 min. CVR to CO?during the dynamic cyclic exercise was 5.33 % mmHg-1 and 4.78 % mmHg?1 in the 5-min and the 10-min analysis, respectively. In the 5-min and the 10-min analysis, CVR to CO?significantly correlated with the exercise intensity during the 10-min bout (r2 = 0.89 and 0.75, respectively). During the on-transient phase of dynamic exercise, CBF would be influenced by PaCO?and other factors such as the neuronal activation and cardiac output would also be involved in changing CBF

Optimization of surface-mount-device light-emitting diode packaging : investigation of effects of component optical properties on light extraction efficiency

An investigation of the effects of the optical properties of surface-mount-device (SMD) light-emitting diode (LED) (side-view and top-view LEDs) packaging (PKG) components on the light extraction efficiency ηPKG using ray-tracing simulations is presented. In particular, it is found that the optical properties of the PKG resin and the lead-frame (L/F) silver-plating significantly affect ηPKG. Thus, the effects of the surface reflection methods of these components are investigated in order to optimize the optical design of the LED PKG. It is shown that there exists peak extraction efficiency for each PKG, and the cavity angle formed by the cavity wall is important to the optical design. In addition, the effect of phosphor present in the mold resin is examined using a Mie scattering simulation. Finally, an SMD LED PKG optical design method is proposed on the basis of the simulation results

Optimization of surface-mount-device light-emitting diode packaging: investigation of effects of component optical properties on light extraction efficiency

An investigation of the effects of the optical properties of surface-mount-device (SMD) light-emitting diode (LED) (side-view and top-view LEDs) packaging (PKG) components on the light extraction efficiency η PKG using ray-tracing simulations is presented. In particular, it is found that the optical properties of the PKG resin and the lead-frame (L/F) silver-plating significantly affect η PKG . Thus, the effects of the surface reflection methods of these components are investigated in order to optimize the optical design of the LED PKG. It is shown that there exists peak extraction efficiency for each PKG, and the cavity angle formed by the cavity wall is important to the optical design. In addition, the effect of phosphor present in the mold resin is examined using a Mie scattering simulation. Finally, an SMD LED PKG optical design method is proposed on the basis of the simulation results

lnitial Human PET Studies of Metabotropic Glutamate Receptor Type 1 Ligand 11C-lTMM

N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-4-11C-methoxy-N-methylbenzamide (11C-ITMM) is a potential radioligand for mapping metabotropic glutamate receptor type 1 (mGluR1) in the brain by PET. The present study was performed to determine the safety, distribution, radiation dosimetry, and initial brain imaging of 11C-ITMM in healthy human subjects. Methods: The multiorgan biodistribution and radiation dosimetry of 11C-ITMM were assessed in 3 healthy human subjects, who underwent 2-h whole-body PET scans. Radiation dosimetry was estimated from the normalized number of disintegrations of source organs using the OLINDA/EXM program. Five healthy human subjects underwent 90-min dynamic 11C-ITMM scans of brain regions with arterial blood sampling. For anatomic coregistration, T1-weighted MR imaging was performed. Metabolites in plasma and urine samples were analyzed by high-performance liquid chromatography. 11C-ITMM uptake was assessed quantitatively using a 2-tissue-compartment model. Results: There were no serious adverse events in any of the subjects throughout the study period. 11C-ITMM PET demonstrated high uptake in the urinary bladder and gallbladder, indicating both urinary and fecal excretion of radioactivity. The absorbed dose (muGy/MBq) was highest in the urinary bladder wall (13.2+/-3.5), small intestine (9.8+/-1.7), and liver (9.1+/-2.0). The estimated effective dose for 11C-ITMM was 4.6+/-0.3muSv/MBq. 11C-ITMM showed a gradual increase of radioactivity in the cerebellar cortex. The total distribution volume in the brain regions ranged from 2.61+/-0.30 (cerebellar cortex) to 0.52+/-0.17 (pons), and the rank order of the corresponding total distribution volume of 11C-ITMM was cerebellar cortex > thalamus > frontal cortex > striatum &#8776; pons, which was consistent with the known distribution of mGluR1 in the primate brain. The rate of 11C-ITMM metabolism in plasma was moderate: at 60 min after injection, 62.2%+/-8.2% of the radioactivity in plasma was intact parent compound. Conclusion: The initial findings of the present study indicated that 11C-ITMM PET is feasible for imaging of mGluR1 in the brain. The low effective dose will permit serial examinations in the same subjects

Global Alliance for the Promotion of Physical Activity: the Hamburg Declaration

Non-communicable diseases (NCDs), including coronary heart disease, stroke, hypertension, type 2 diabetes, dementia, depression and cancers, are on the rise worldwide and are often associated with a lack of physical activity (PA). Globally, the levels of PA among individuals are below WHO recommendations. A lack of PA can increase morbidity and mortality, worsen the quality of life and increase the economic burden on individuals and society. In response to this trend, numerous organisations came together under one umbrella in Hamburg, Germany, in April 2021 and signed the ‘Hamburg Declaration’. This represented an international commitment to take all necessary actions to increase PA and improve the health of individuals to entire communities. Individuals and organisations are working together as the ‘Global Alliance for the Promotion of Physical Activity’ to drive long-term individual and population-wide behaviour change by collaborating with all stakeholders in the community: active hospitals, physical activity specialists, community services and healthcare providers, all achieving sustainable health goals for their patients/clients. The ‘Hamburg Declaration’ calls on national and international policymakers to take concrete action to promote daily PA and exercise at a population level and in healthcare settings