Nash Fick | University of LIberal Arts Bangladesh (original) (raw)
Address: Dhaka, Bangladesh
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Transepidermal water loss (TEWL) through the ventral skin of the hamster ear was determined using... more Transepidermal water loss (TEWL) through the ventral skin of the hamster ear was determined using a modified flow-through diffusion apparatus. Tritium-labeled water was allowed to permeate through the dermal/epidermal layers. Water vapor was collected in a closed system by adsorption onto solid anhydrous calcium chloride in a separately attached receiver. The desiccant was removed, dissolved in water, and the radioactivity determined by liquid scintillation counting. The rate of TEWL was determined for various durations of exposure to the desiccated environment, in the temperature range between 5 and 40øC. TEWL rate reached a maximum one hour after exposure, and then decreased to a steady state with time. TEWL increased exponentially with increasing temperature in accordance with the Arrhenius relationship. An activation energy value of 13 Kcal/mole was obtained. At incubator temperature of 22øC, the rate of TEWL was found to be 152 _+ 14 p,g/cm2/hr, which agrees with previously reported values obtained by in vivo methods of testing. The present technique is proposed as a rapid in vitro method for measuring TEWL and as a possible pretest for assessing efficacy of potential skin-moisturizing agents. Four agents were studied for their effect on water permeability. The agents tested were mineral oil, castor oil, sesame oil, and 25% glycerin in water. Skin membranes treated with occlusive agents such as mineral oil, castor oil, and sesame oil showed a marked decrease in the TEWL rate, while those membranes treated with the humectant, 25% glycerin in water, showed a marked increase in the TEWL rate. Similar results using these same agents have been reported previously.
European Journal of Applied Physiology, 2010
This study investigated cycling performance and oxygen uptake \(( \dot{V}{\text{O}}_{ 2} )\) kine... more This study investigated cycling performance and oxygen uptake \(( \dot{V}{\text{O}}_{ 2} )\) kinetics between upright and two commonly used recumbent (R) postures, 65°R and 30°R. On three occasions, ten young active males performed three bouts of high-intensity constant-load (85% peak-workload achieved during a graded test) cycling in one of the three randomly assigned postures (upright, 65°R or 30°R). The first bout was performed to fatigue and second and third bouts were limited to 7 min. A subset of seven subjects performed a final constant-load test to failure in the supine posture. Exercise time to failure was not altered when the body inclination was lowered from the upright (13.1 ± 4.5 min) to 65°R (10.5 ± 2.7 min) and 30°R (11.5 ± 4.6 min) postures; but it was significantly shorter in the supine posture (5.8 ± 2.1 min) when compared with the three inclined postures. Resulting kinetic parameters from a tri-exponential analysis of breath-by-breath \( \dot{V}{\text{O}}_{ 2} \) data during the first 7 min of exercise were also not different between the three inclined postures. However, inert gas rebreathing analysis of cardiac output revealed a greater cardiac output and stroke volume in both recumbent postures compared with the upright posture at 30 s into the exercise. These data suggest that increased cardiac function may counteract the reduction of hydrostatic pressure from upright ~25 mmHg; to 65°R ~22 mmHg; and 30°R ~18 mmHg such that perfusion of active muscle presumably remains largely unchanged, and also therefore, \( \dot{V}{\text{O}}_{ 2} \) kinetics and performance during high-intensity cycling.
Transepidermal water loss (TEWL) through the ventral skin of the hamster ear was determined using... more Transepidermal water loss (TEWL) through the ventral skin of the hamster ear was determined using a modified flow-through diffusion apparatus. Tritium-labeled water was allowed to permeate through the dermal/epidermal layers. Water vapor was collected in a closed system by adsorption onto solid anhydrous calcium chloride in a separately attached receiver. The desiccant was removed, dissolved in water, and the radioactivity determined by liquid scintillation counting. The rate of TEWL was determined for various durations of exposure to the desiccated environment, in the temperature range between 5 and 40øC. TEWL rate reached a maximum one hour after exposure, and then decreased to a steady state with time. TEWL increased exponentially with increasing temperature in accordance with the Arrhenius relationship. An activation energy value of 13 Kcal/mole was obtained. At incubator temperature of 22øC, the rate of TEWL was found to be 152 _+ 14 p,g/cm2/hr, which agrees with previously reported values obtained by in vivo methods of testing. The present technique is proposed as a rapid in vitro method for measuring TEWL and as a possible pretest for assessing efficacy of potential skin-moisturizing agents. Four agents were studied for their effect on water permeability. The agents tested were mineral oil, castor oil, sesame oil, and 25% glycerin in water. Skin membranes treated with occlusive agents such as mineral oil, castor oil, and sesame oil showed a marked decrease in the TEWL rate, while those membranes treated with the humectant, 25% glycerin in water, showed a marked increase in the TEWL rate. Similar results using these same agents have been reported previously.
European Journal of Applied Physiology, 2010
This study investigated cycling performance and oxygen uptake \(( \dot{V}{\text{O}}_{ 2} )\) kine... more This study investigated cycling performance and oxygen uptake \(( \dot{V}{\text{O}}_{ 2} )\) kinetics between upright and two commonly used recumbent (R) postures, 65°R and 30°R. On three occasions, ten young active males performed three bouts of high-intensity constant-load (85% peak-workload achieved during a graded test) cycling in one of the three randomly assigned postures (upright, 65°R or 30°R). The first bout was performed to fatigue and second and third bouts were limited to 7 min. A subset of seven subjects performed a final constant-load test to failure in the supine posture. Exercise time to failure was not altered when the body inclination was lowered from the upright (13.1 ± 4.5 min) to 65°R (10.5 ± 2.7 min) and 30°R (11.5 ± 4.6 min) postures; but it was significantly shorter in the supine posture (5.8 ± 2.1 min) when compared with the three inclined postures. Resulting kinetic parameters from a tri-exponential analysis of breath-by-breath \( \dot{V}{\text{O}}_{ 2} \) data during the first 7 min of exercise were also not different between the three inclined postures. However, inert gas rebreathing analysis of cardiac output revealed a greater cardiac output and stroke volume in both recumbent postures compared with the upright posture at 30 s into the exercise. These data suggest that increased cardiac function may counteract the reduction of hydrostatic pressure from upright ~25 mmHg; to 65°R ~22 mmHg; and 30°R ~18 mmHg such that perfusion of active muscle presumably remains largely unchanged, and also therefore, \( \dot{V}{\text{O}}_{ 2} \) kinetics and performance during high-intensity cycling.