Biosynthesis of adrenocortical steroids by monotremes: echidna (Tachyglossus aculeatus) and platypus (Ornithorhynchus anatinus)

The formation of corticosteroids from [14C]pregnenolone or [14C]progesterone by platypus and echidna adrenal homogenates was studied. Corticosteroids were assayed in the peripheral blood plasma of the platypus. In the platypus nine labelled conversion products were identified. The combined yields of cortisol and cortisone averaged 70% and the combined yields of corticosterone and 11-dehydrocorticosterone averaged 14%. Aldosterone was identified in each experiment in yields below 0·1%. In the echidna ten labelled conversion products were identified. Those in highest yield were 11-deoxycorticosterone and 11-deoxycortisol which contained, respectively, an average of 35 and 11% of the added substrate. The yield of corticosterone was always less than 1% and that of cortisol was consistently lower. Aldosterone was identified in all cases in yields below 0·05%.

The yields of total 11β-hydroxylated conversion products from platypus adrenal exceeded 80%, whereas they were below 1% from glands of male echidnas and 7% from female echidna.

The yield—time curves for labelled conversion products from [14C]-pregnenolone indicated that the biosynthetic pathways of corticosteroid production by the monotreme adrenal are similar to those in eutherian mammals.

From stored endogenous precursors of a platypus adrenal incubated for 30 min, corticosteroids were formed in the following amounts (per 100 mg adrenal): cortisone, 5·1 μg; cortisol, 1·3 μg; 11-dehydrocorticosterone, 1·5 μg. In the peripheral plasma of platypus the concentration of combined cortisol and cortisone was 14 μg/100ml and the combined corticosterone and 11-dehydrocorticosterone was 1·8 μg. The mean ratio of adrenal weight (mg) to body weight (kg) was 39·5 in the echidna and 257 in the platypus. The marked contrast in adrenocortical biosynthetic capacity of the two monotremes is discussed and a comparison of the results is made in relation to higher mammals.

Airborne Measurements of Earth Surface Temperature (Ocean and Land) in the 10-12-micro and 8-14-micro Regions

Field experience using infrared radiometers for making airborne measurements of land and ocean surface temperature show that an atmospheric induced error and a surface reflectivity error are present when the 8-14-micro atmospheric window is used. It is generally accepted that the error can be minimized by working in a narrow region of the atmospheric window centered about 10.5 micro. In order to evaluate the improvement in performance using the narrow band filter region, simultaneous airborne measurements were made with two Barnes model PRT-5 infrared radiometers flown side by side over land and water areas for a range of altitudes up to 8000 ft (2440 m). One radiometer contained an 8-14-micro (standard) filter, and the second contained a 10-12-micro filter. Comparison of the data shows the narrow band filter to reduce the measured error 1.5-2.0 times compared with the wide band filter. The data also show that the error increases approximately linearly with altitude, and therefore by taking measurement at two altitudes and linearly extrapolating to ground level, an accuracy of measurement of a few tenths of a degree Celsius is possible.