Continuous light increases N-acetyltransferase activity in the optic lobe of the giant freshwater prawn Macrobrachium rosenbergii de Man (Crustacea: Decapoda).

Giant freshwater prawns, Macrobrachium rosenbergii de Man, were reared under three different lighting conditions: continuous darkness (DD), 12 hr of light and 12 hr of darkness (LD 12:12) and continuous light (LL). After one month, the prawns were sacrificed and optic lobes isolated from the eyestalks were determined for N-acetyltransferase (NAT) activities and melatonin concentrations. Gonads were weighed and examined under light microscopy.

Stereological changes in rat ventral prostate induced by melatonin.

Effects of melatonin on the ventral prostate of castrated rats supplemented with testosterone were studied using light microscopy. Stereological measurements were made of volume fractions of acini and stroma and surface fractions of glandular epithelium. From these figures and the weights of the glands, the volumes and surface areas were calculated, as well as the mean epithelial heights, mean acinar diameters, and mean distances between glandular acini.

Dynamic uptake of radioactive substance in rat salivary gland following 3H-melatonin administration.

Dynamics of radioactive accumulation in rat greater salivary gland following systemic administration of 3H-melatonin was studied to determine a possible action of the hormone in the gland. Progressive decline of 3H-melatonin concentrations was found in the serum, lung, skeletal muscle, liver, kidney, and salivary gland during 60 min following the administration. On the contrary, there was a progressive accumulation of radioactive substance other than 3H-melatonin in the salivary gland but not in other tissues mentioned.

Retention of radioactive substances in the hypothalamus, anterior pituitary, and reproductive organs of male rats after 3H-melatonin administration.

Radioactive concentrations were determined in serum, lung, hypothalamus, anterior pituitary, testis, and accessory sex organs of adult male rats at 2, 20, 30 and 60 min after intravenous 3H-melatonin administrations. The retention patterns of 3H-melatonin and other radioactive substance (3H-non-melatonin) in these tissues were compared. The anterior pituitary demonstrated best tissue retention with highest concentration of 3H-melatonin.