Adenyl cyclase activity in rat pineal gland: effects of chronic denervation and norepinephrine

Adenyl cyclase activity in the pineal gland of rats was determined by measuring the rate of formation of radioactive cyclic 3',5'-adenosine monophosphate from (14)C-labeled adenosine triphosphate. Norepinephrine added in vitro to pineal homogenates enhanced this activity, while denervation of the pineal gland by superior cervical ganglionectomy did not significantly reduce it. The enzyme in these denervated glands was more responsive to the stimulatory effects of norepinephrine.

A computer analysis of serial interactions in spaced responding

Serial dependencies in interresponse times were studied by means of a digital computer. In monkeys exposed to a DRL 20-sec schedule of reinforcement, serial interactions appeared at all stages of training. Early in training the serial effects consisted of trains of relatively long interresponse times interspersed among trains of relatively short ones. Later on, the serial effects appeared to be characterized by a tendency to drift up and down in long wavelength periods around the minimum interval required for reinforcement. After training to a point at which most interresponse times produced reinforcement, serial effects of a still more subtle nature appeared. These effects were made apparent by autocorrelation and power spectrum methods and consisted of both long-term and extremely short-term fluctuations in interresponse times.

The enzymatic phosphorylation of nucleic acids and its application to end-group analysis

Polynucleotide kinase catalyzes the transfer of a phosphate group from ATP to the 5'-hydroxyl termini of polynucleotides. Selective labeling of the 5'-hydroxyl termini of DNA with polynucleotide kinase has been used to study the number and the identity of the 5'-terminal residues of bacteriophage DNA's, and to examine the nature of the phosphodiester bond cleavages produced by endonucleases and by sonic irradiation. The intact strands of T7 DNA bear 5'-phosphoryl end-groups; only deoxyadenylate and deoxythymidylate are present as 5'-terminal residues. The intact strands of native lambda-DNA bear 5'-hydroxyl end-groups. M13 DNA, a circular molecule, cannot be phosphorylated. End-group labeling of DNA provides a method for determination of molecular weight; calibration against other DNA preparations is not required. The molecular weight of a single strand of T7 DNA, determined by end-group labeling, is 13.1 x 10(6); the molecular weight of a single strand of lambda-DNA is 16.0 x 10(6). These values are in agreement with molecular weight estimates by sedimentation analysis and electron microscopy. Sonic irradiation of DNA has been shown to favor the production of polynucleotides terminated by 5'-phosphomonoester groups. All four deoxyribonucleotides are present as 5'-terminal residues of sonicated DNA.

Behavioral thermoregulation during vitamin B6 deficiency

Thermoregulatory behavior was studied in vitamin B6-deficient and control rats exposed to a temperature of 2–3 C. The animals were kept in an experimental chamber provided with a lever which, when pressed, turned on a heat lamp placed above the chamber. The B6-deficient rats turned on the heat lamp more frequently than did the controls. This difference was observed with both ad libitum and paired feeding. Furthermore, administration of vitamin B6 to the deficient rats and deoxypyridoxine, a B6 antagonist, to the controls brought about reversals in the relative frequency of heat reinforcements which were accompanied by changes in biochemical indices of vitamin B6 deficiency, i.e., increased xanthurenic acid excretion and decreased plasma glutamic-oxalacetic transaminase levels. Measurements of skin and rectal temperatures in the cold indicate that the body temperature of B6-deficient rats falls more rapidly than that of controls, a fact which would account for the difference in thermoregulatory behavior. Attempts to search for evidence of thyroid dysfunction in B6-deficient rats as the possible cause of such behavioral differences were unrevealing. These experiments indicate that behavioral studies are useful in assessing nutritional deficiency.