Maximum metabolic rate estimation

Figure 2.5. Metabolic scope for activity (defined as the difference between maximum metabolic rate and the SMR) and the metabolic scope for survival (defined as the difference between the SMR and maximally suppressed metabolic rates). Hummingbird estimates shown for normothermic conditions and for torpor metabolic rates (the latter gives the full biological scope for activity). Suppressed metabolic rates for the aquatic organisms assume temperatures of about 20°C (except for the pumpkinseed, where suppressed metabolism occurs during overwintering hibernation at about 4°C). (Modified from Hochachka (1990.)...

Small amounts of phenytoin are excreted unchanged in the urine (2-4%) and feces (5%). Most is eliminated renally as inactive conjugated metabolites. The elimination half-life at linear doses averages 20-30 h (12-20 h in children) but may be as long as 60 h, and as high as 200 h after overdose, due to saturation of hydroxylation pathways. The maximum rate of metabolism is estimated at 6mgkg day. ... 

Direct evaluation of the convective heat transfer coefficient (h ) of subjects clothed in undergarments and socks (normal ventilated environment) was achieved by observing the sublimation rate of naphthalene balls uniformly positioned three centimeters from the body surface. Equations were developed for prediction of h as a function of metabolic activity and posture, calculation o average skin temperature, and estimation of maximum evaporative heat losses from the body (U2 ). In another approach, the coefficients of dry heat transfer at varying wind speeds for nude and clothed sectional mannequins were determined (U3). At air flow rates above 2 m/sec, percentage contributions of individual body sections to total heat transfer remain constant for the nude and clothed mannequin, yet increased for normally uncovered units such as the face and hands. Generally, the ratio of total heat flow for the nude to clothed mannequin increased with air flow. 

As far as the rate component of bioavailability is concerned, it is estimated by two parameters, Cmax and tmax. The maximum plasma concentration (Cmax) is related to (a) total plasma clearance (b) the fraction of dose that reaches the general circulation without being metabolized (c) the rate of absorption and (d) the rates of distribution and elimination. The time to reach Cmax (tmax) depends on (a) the rate of absorption and (b) the rates of distribution and elimination. 

Metabolites of tea catechins are excreted in bile or urine. In general, small conjugates, such as monosulfates, tend to be excreted in urine, and extensively conjugated metabolites are more likely to be excreted in bile. The total amount of metabolites excreted in urine correlated roughly with maximum plasma concentrations. " The exact half-lives of tea catechins in plasma were calculated to be in the order of 2-3 h, except for EGCG, which is eliminated more slowly. " Relative urinary excretion data were used to estimate the minimal absorption rate and were consistent with the plasma kinetic data for most catechins, but for EGCG that mostly excreted in bile, the urinary excretion rate was very small (0-0.1%), and its absorption was underestimated. The urinary excretion rates of EC and EGC were 18.5 and 11.1%, respectively. The low cumulative excretion of tea catechins in human urine, which was 0-9.8%, suggested that they were extensively metabolized in the human body. 

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