Androgen on the estrogen receptor. I - Binding and in vivo nuclear translocation

In the immature rat uterus, high concentrations of androgens competed specifically with estradiol on the estrogen receptor (RE). This competition was stereospecific for C19 steroids bearing a 17beta and/or 3 hydroxyl group. Very low affinity ligands, such as testosterone, could not compete with estradiol at equilibrium but decreased the association rate of estradiol on its receptor. High doses (greater than 0.4mg) of 5dihydrotestosterone provoked in vivo as in vitro the nuclear translocation of RE. The nuclear receptor thus formed displayed the same 5.2 S sedimentation constant as that induced by estradiol. We conclude that the weak affinity binding of androgens to the estrogen receptor is sufficient to induce its nuclear translocation in vivo provided androgen concentration is high enough in uterus to occupy the estradiol binding site. Conversely, progesterone which does not bind RE could not provoke its nuclear translocation.

Identification of tachistoscopically exposed symmetrical and asymmetrical letter arrays

Six-letter arrays containing symmetrical, e.g., H, M, T, or asymmetrical letters, e.g., J, K, R, were tachistoscopically exposed bilaterally for 100 msec. to 100 college students. Significantly more asymmetrical than symmetrical letters were identified, and significantly more Ss identified more asymmetrical than symmetrical items. This experiment, which incorporated methodological considerations suggested by Harcum (1964) and Bryden (1968), corroborates their findings. Their ideas and other findings were used to account for the data. Asymmetrical letters have more intrinsic left-to-right directionality than symmetrical elements. The rapidly fading after-stimulation of tachistoscopically presented alphabetical material is usually scanned from left to right. Individual array letters might also be scanned in the same direction. Confluence of directionality of letter and scan, which obtains only with asymmetrical letters, might have typically allowed asymmetrical targets to be scanned more rapidly and, consequently, more efficiently than symmetrical displays.

Antagonism between penicillin and chloramphenicol in experimental pneumococcal meningitis

Trimethoprim and sulfamethoxazole were tested alone and in combination against 227 recently isolated Shigella strains. Variations in medium constituents and inoculum size were used to determine the optimal testing conditions. The plate dilution method with addition of 5% lysed horse blood to the susceptibility test medium and an inoculum size of 10² organisms was found to provide satisfactory results. All 227 strains were inhibited by low concentrations of trimethoprim, and all were susceptible to the combination of 0.06 μg of trimethoprim per ml and 1.25 μg of sulfamethoxazole per ml. Sixteen percent of these strains were resistant to ampicillin, 33% to tetracycline, 15% to chloramphenicol, and 27% to cephalothin. Based on these in vitro observations, trimethoprim and sulfamethoxazole appear worth evaluating for treatment of shigellosis due to multiply antibiotic-resistant strains.

Blockade of the antiadrenergic action of Bretylium by an aqueous extract of the leaves of Rhoeo spathacea

In isolated rabbit ileum, bretylium-induced blockade of the inhibitory response to stimulation of the adrenergic nerve supply is prevented by an aqueous extract of the leaves of Rhoeo spathacea, apparently as a result of its dopamine content.

An eserine-like action of chloroquine

High concentrations of chloroquine antagonize the hydrolysis of acetylcholine by acetylcholinesterase as well as by the pseudocholinesterase found in dog serum.