Loren D. Carlson

A HUMAN CALORIMETER.

Human calorimeter studies have been made in the past under static environmental conditions since stabilization time or heat content of thermal barrier materials limit measurement when the environment is changed. Direct calorimetry combined with indirect calorimetry offers the marked advantages of measuring the change in heat content of the body during transient states. Thus the most significant value of direct calorimetry is in dynamic caloric studies where transient energy exchange is measured. The thermal gradient calorimeter as devised by Day and Hardy(l) and Benzinger and Kitzinger(2) permits these studies when the unsteady state is produced by conditioning of the subject at different temperatures prior to insertion into the calorimeter or by increasing heat production by exercise. The human calorimeter described is designed to indicate variations in body heat exchange and to allow change and stabilization of environment within a few minutes. It is similar in concept to the calorimeter described by Visser and Hodgson(3). Overall design and performance specifications.† The interior floor space is .91 meter by .76 meter and the height is 1.83 meters allowing the subject to sit or stand in the calorimeter. Inlet temperature can be regulated at temperatures between 5°C and 50°C. Humidity may be reduced from ambient conditions by a precool coil. The temperature can be changed at a maximum rate of 2.5°C per minute.

ENZYMES IN ONTOGENESIS (ORTHOPTERA): XVIII. ESTERASES IN THE GRASSHOPPER EGG

1. Proteins, when added to activators (sodium oleate. Aerosol) of protyrosinase, greatly decrease the degree of activation. 2. Certain proteins adsorbed on activator micelles are markedly affected by temperature and are rendered more sensitive by ultraviolet light. 3. Ideas are expressed as to the possible nature of activating and inhibiting phenomena especially as they relate to the enzyme tyrosinase.

Ultraviolet Absorption Spectrum of Protyrosinase and Tyrosinase.

Summary We have purified to come extent the pronezyme (protytosinase) without activating it. There is a charge in the absorption spectrum in the ultraviolet accompanying the activation of the protyrosinase molecule to the active tyrosinase from.

ENZYMES IN ONTOGENESIS (ORTHOPTERA): XII. SOME PHYSIOLOGICAL CHANGES IN EGGS THE EMBRYOS OF WHICH HAVE BEEN DESTROYED BY X-IRRADIATION

Investigations have been conducted on the effect of x-irradiation on the morphology, respiration and enzyme (protyrosinase) formation in the egg of the grasshopper, Melanoplus differentialis (Evans, 1934; 1935; 1936; 1937; Boell, Ray and Bodine, 1937; Ray, 1938). By the fifth day of development at 25? C. differentiation has progressed to such a degree that the embryo may be dissected from the egg (Slifer and King, 1934). An x-irradiation of 1000 r given the egg on the sixth day after laying will cause the destruction of the embryo proper leaving the yolk and serosa cells intact (Evans, 1936; Ray, 1938). This permits a study to be made on some of the physiological activities of these eggs from which the embryo has been thus removed. The following three criteria of physiological activity in these eggs were used: (1) Respiration: The respiration of the whole egg as well as of the contained embryo has been reported (Bodine and Boell, 1936). For the first 15 to 20 days after laying, the rate of 02 uptake increases; then it declines to a minimum by the twentieth to twenty-fifth day and remains constant during the blocked or diapause state. This period of inactivity (diapause) may be terminated by exposure to 5? C. and when the eggs are again placed at 25? C. there is a rapid increase in the rate of respiration until the grasshopper hatches on the eighteenth to twentieth day. The respiration of the embryo is, at first, lower than that of the intact egg, but later it accounts for a considerable part of late prediapause and postdiapause respiration (Bodine and Boell, 1936). (2) Formation of the enzyme protyrosinase: This enzyme in the normal egg begins to form on the tenth day and by the twentieth day has reached a maximum which is maintained during further development (Bodine, Allen and Boell, 1937). The remarkable resistance of this enzyme to x-irradiation during its formation has been reported (Ray,

Reactive Sulfhydryl and Disulfide Groups of Protyrosinase and Tyrosinase.

Summary and Conclusions It seems evident that no change in sulfhydryl nor disulfide groups occurs upon activation of protyrosinase and further that the sulfhydryl and disulfide groups do not seems essential for enzyme activity. Any apparent inhibition caused by oxidation of the sulfhydryl groups or the reduction of the disulfide groups is due to a reaction of the oxidant or reductant with the intermediary products of the oxidation of tyramine-HCL. If the production of tyrosinase is occasioned by the denaturation of an inhibitor, an increase in-SH groups seems probable; this, however, is not the case.