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IT WAS SHOWN in a previous report from this laboratory (Meyer, McShan and Erway, 1945) that the ovaries of pregnant and pseudopregnant rats were high in succinic dehydrogenase (SDH-ase) and that this high activity was due to the lutein tissue rather than the other ovarian tissues. However, the determinations during pregnancy were made on days 18 and 20 of gestation, and therefore information is not available as to the way in which this enzyme changes in activity throughout pregnancy and lactation. Thus it was of interest to determine the SDH-ase activity of the corpora lutea and other ovarian tissues at intervals during these two phases of the reproductive cycle. The results obtained are presented in this report. EXPERIMENTAL Sprague-Dawley rats approximately 4 months of age were used in the study. Males were introduced into cages containing females on the day preceding the next estimated estrus and the females were examined on the following morning to determine whether insemination had taken place.

IT IS WELL KNOWN that the adenosine triphosphate system occupies a key position in the energy exchanges of muscle during glycolysis. The presence of ATP and the ATP-splitting enzyme, ATP-ase, in variable quantities in a number of additional tissues has been reported (DuBois and Potter, 1943), and evidence has been presented pointing to the ATP system as a unique mechanism in linking the energy-requiring reactions of tissues with the energy-yielding reactions (Potter, 1945). These reports suggested that the energy changes occurring in tissues other than muscle might be mediated through the ATP system. We became interested, therefore, in determining whether or not the ATP-ase activity of ovarian tissues varied during the different phases of the reproductive cycle, as it is well known that these tissues undergo rapid changes in function and structure at these times. The studies which are reported here were made on the ATP-aee activity of lutein and remaining ovarian tissues during the reproductive cycle. A p...

SINGER (1) AND BARRIE (2) have presented data which indicated that vitamin-Edeficiency has an influence on the histology of the thyroid gland. The former described a hypoplasia of the thyroid of 12 to 18-month E-deficient female rats, and the latter a hypoplasia of the thyroid of both E-low mothers and young born to them. The results of Singer and Barrie have been questioned by Telford, Emerson and Evans (3), who reported that they could find no evidence of hypothyroidism in E-low female rates or in young born to them. We have previously reported (4) that the weight of the thyroids of male rats deficient in vitamin E for 6 months or more was approximately twice that of normal controls, whereas the weight of thyroids from female E-deficient rats was not significantly different from that of normals in any of the age groups studied

IN PREVIOUS quantitative studies from this laboratory it has been shown that the ovarian response of the non-castrated partner of parabiotic rats is a sensitive and reliable indicatorof the quantity of gonadotropic hormone released into the circulation of the rats by the pituitarygland of the castrated partner. It was demonstrated that crystalline estrone (1), estrin from theamniotic fluid of cattle (2) and testosterone, testosterone propionate and dehydroandrosterone (3)were effective in preventing the hypersecretion of gonadotropic hormone that occurs following castration of either male or female rats. When progressively greater quantities of the gonadal hormoneswere injected into the castrated partner the size of the ovaries of the normal partner was progressively decreased. If sufficient hormone was injected the ovaries were no larger than those of non-castrated controls.