A soluble chloroplast protein catalyzes ribulosebisphosphate carboxylase/oxygenase activation in vivo

Ribulosebisphosphate carboxylase/oxygenase (EC 4.1.1.39) (rubisco) must be fully activated in order to catalyze the maximum rates of photosynthesis observed in plants. Activation of the isolated enzyme occurs spontaneously, but conditions required to observe full activation are inconsistent with those known to occur in illuminated chloroplasts. Genetic studies with a nutant of Arabidopsis thaliana incapable of activating rubisco linked two chloroplast polypeptides to the activation process in vivo. Using a reconstituted light activation system, it was possible to demonstrate the participation of a chloroplast protein in rubisco activation. These results indicate that a specific chloroplast enzyme, rubisco activase, catalyzes the activation of rubisco in vivo.     

Potentiation of the antagonistic effect of ACTH11-24 on steroidogenesis by synthesis of covalent dimeric conjugates

Covalent dimerization of the adrenocorticotropin fragment ACTH11-24 increases its antagonistic potency on the ACTH-induced steroidogenesis in isolated bovine fasciculata/reticularis cells by 3 orders of magnitude when the C-termini are linked via a 10 A long spacer. This strong potentiation, probably mediated by cross-linking of the receptors, was shown to be dependent on the point of attachment of the monomeric fragment to the spacer, thus providing information about the position of the binding site in the hormonal segment and about the distance of the receptors on the cell surface.     

T wave changes in humans and dogs during experimental dives.

Electrocardiogram (ECG) analysis was performed in three human divers studied at 21 and 23.5 ATA while they breathed various gas mixtures containing H2 and/or He (COMEX HYDRA IX experiment) and in five dogs exposed to 91 ATA of He-O2 or He-N2-O2. In all cases, the O2 partial pressure was slightly higher than its physiological value. These human and animal studies reveal that elevated pressure of different inert gases did not change the resting heart rate or its respiratory fluctuation. However, the T wave amplitude increased in proportion to the gas density in the three divers; this was also found in four of the five dogs studied. Changes in peak T wave configurations were also observed in the dog experiments. Positional changes in QRS or T vectors cannot explain these T wave changes.     

Oral behaviour following forebrain ablations in Gallus Domesticus

The oral behaviour of adult Brown Leghorn hens was recorded in response to oral stimulation with water, 2 M sodium chloride, 2 M acetic acid and 0.1 M quinine hydrochloride before and after surgical ablation of either the anterior telencephalon or the entire telencephalon and/or the diencephalon. It was found that beak wiping behaviour could be abolished by the removal of the anterior telencephalon. Head shaking behaviour was abolished only by the complete removal of the forebrain (telencephalon and diencephalon) whereas beak and tongue movements persisted after forebrain removal. Although these three behaviour patterns occur together in response to the stimulus, they appear to be controlled in different areas of the brain. The results are discussed in relation to the current work on the control of oral behaviour in mammals.