Nocturnal peaks in core body temperature of rats during the estrous cycle were highest during the night of ovulation (2300-0200 h, proestrus-estrus) and lowest during the night before (diestrus 2-proestrus). Less dramatic diurnal secondary peaks, absent only during estrus, occurred 3-4 h after the onset of daylight. After induction of pseudopregnancy, mean temperature declined, but both daily peaks persisted until the first postluteal estrus, when the secondary peak was again absent transiently. Ovariectomy reduced mean core temperature and abolished all secondary peaks. In contrast, castration during pseudopregnancy did not abolish the secondary peaks. When cyclic rats were gonadectomized (abolishing the secondary rhythm) it was possible to re-establish this rhythm by stimulating the uterine cervix (as if to induce pseudopregnancy). However, in animals exposed to darkness (which also abolishes the secondary rhythm) reinduction by cervical stimulation was ineffective. These results indicated that the integrity of the secondary peak, though dependent on photoperiod, nevertheless was influenced by a neuroendocrine reflex arc.

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Particulate fractions isolated from the growing region of the epicotyl of Pisum sativum L. var Alaska are capable of transferring glucose from uridine or guanosine diphosphate glucose-14C to buffer-insoluble products which are partly alkali-soluble and partly alkali-insoluble. Cellobiose activates the reaction; carboxymethylcellulose and cellodextrins act as competitive acceptor molecules.When the epicotyl is decapitated, glucan synthetase activity disappears from particulate fractions of the growing region within 3 days unless the hormone indoleacetic acid (IAA) is added to the tissue, in which event activity is retained. Other growth regulators (gibberellic acid, benzyladenine) have no such effect. Loss of activity is not due to a change in solubility of enzyme or product or to the absence of substrate, activator, or acceptor molecules, nor is it accompanied by comparable losses in total protein or cellulase activity from the particulate fraction. It is concluded that IAA is needed for the formation and/or protection of an essential part of the insoluble synthetase complex.

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