• A V Kurpad

      Articles written in Journal of Biosciences

    • Characteristics of norepinephrine stimulated thermogenesis in undernourished subjects

      A V Kurpad R N Kulkarni D Rodriguez P S Shetty

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      Thermoregulatory thermogenesis was evaluated in chronically undernourished subjects as well as normally nourished controls by 60 min infusions of norepinephrine at a calculated dose of 0.15 μg/kg fat free mass/min. There was a significant (P< 0.05) reduction in the thermogenic response to norepinephrine in the undernourished labourers. When the characteristics of response were evaluated, the baseline and peak responses were comparable in both groups. However, the steepness of the response was greater (P< 0.05) in the undernourished subjects. The time to register a threshold response of 5 ml per min increase in oxygen consumption over the baseline after the start of infusion was longer in undernourished (about 20 min) as compared to the controls (about 10 min). It appears that, while the undernourished subjects have a reduced thermogenic component in their energy output, their peak capacity or potential for regulatory thermogenesis is the same as that in control subjects, since their thermogenic response has a greater slope. It is possible that chronically undernourished subjects may have a suppressed response over shorter periods of stimulation (less than 20 min), that is, before steady state thermogenic responses are achieved.

    • Bicarbonate kinetics in Indian males

      T Raj R Kuriyan A V Kurpad

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      Measurement of rates ofin vivo substrate oxidation such as that of glucose, fatty acids and amino acids, are based on tracer (14C or13C) data, and often depend on the isotopic content of expired CO2. The recovery of tracer-labelled CO2 generated from the oxidation of13C labelled substrates may not be 100% over short term. This can lead to underestimation of oxidation rate of substrates, and consequently a correction for the incomplete recovery of tracer has to be applied by the determination of the recovery of13CO2 in the breath during tracer bicarbonate infusions. We have studied the recovery of tracer-labelled bicarbonate using a bolus administration model, and further characterized kinetics of bicarbonate using a three-compartment model, to assess which compartmental fluxes changed during the change from a fasted state to fed state. Recovery of bicarbonate was lower at 69% and 67% (fasted and fed state) than the value of 71% and 74% found during earlier longer term of continuous infusions. During feeding, there was a 20-fold increase in the flux of bicarbonate between the central compartment and the compartment that was equivalent to the viscera. This study shows that the difference between the fasted and fed state recovery of tracer bicarbonate similar to that obtained with continuous infusions, and that bicarbonate fluxes show large changes between different compartments in the body depending on metabolic state.

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