Metabolic changes in the rat anterior pituitary and prolactin production following estradiol treatment

The effects of estradiol treatment on the synthesis and release of prolactin and GH in castrated male rats were studied in connection with the anterior pituitary enzymes that represent the hexosemonophosphate shunt, glycolytic, oxidative, and lysosomal activity. LDH and G6P-DH activities increased by 15%–30% at 12 hr and by 70% at 72 hr after estrogen administration. PK activity showed a statistically significant elevation of 20%–40% only after 48–72 hr. ICDH, MDH, acid phosphatase activities, and water-soluble protein concentrations were unchanged. Serum prolactin concentration increased about 400% 24 hr after estradiol injection, and the pituitary synthesized 1000%–1500% more radioactive prolactin in vitro than did control glands. However, no significant increase in prolactin synthesis was observed 12 hr after estradiol treatment.It is suggested that the primary effect of estradiol is on the synthesis of prolactin and that the increased rate of secretion is secondary. Radioimmunoassayable prolactin in the incubated gland tissue and its medium was greatly increased after estradiol treatment. A slight but statistically significant accumulation and decreased release of radioactive GH were also observed. The results suggest a correlation of pituitary prolactin production with the tissue's metabolic activity.     

The Shrinking Landscape of Pediatric Surgery: Is Less More?

The Fred MacLeod Lecture was given at the 49th Annual Canadian Association of Pediatric Surgeons meeting held October 5-7th, 2017, in Banff, Alberta, Canada.     

Chromaticity co‐ordinates of Ishihara plates reveal that hidden digit plates can be read by S‐cones

Background: The Ishihara pseudoisochromatic plates constitute one of the most commonly used screening tools for red‐green colour vision deficiencies. Even though hidden digit plates are supposed to be read only by those who are colour vision defective, studies report that some normal trichromats can indeed read these plates. By measuring the chromaticity co‐ordinates of the dots used in Ishihara plates, the purpose of this study was to clarify the mechanism that enables normal trichromats and colour vision defectives to read the plates, particularly hidden digit plates. Methods: Spectrophotometric measurements were made for a 24‐plate version of the Ishihara pseudoisochromatic plates and chromaticity co‐ordinates of the dots were expressed in the MacLeod‐Boynton diagram. Results: As theoretically expected, reading of Ishihara plates by normal trichromats was mediated by the dot chromaticity differences along the L/(L + M) axis. On the other hand, reading by colour vision defective observers was made possible mainly by the dot chromaticity differences along the S/(L + M) axis. This would also explain why some normal trichromats can read hidden digit plates, the plates that are supposed to be read only by colour vision defective observers. Conclusion: Normal trichromats read Ishihara plates using their chromatic discrimination ability along the L/(L + M) axis. Red‐green colour vision defective observers rely on S‐cones in reading the plates. Some normal trichromats can read the hidden digit plates because they can extract S‐cone differences efficiently despite the distraction from the L/(L + M) axis.