Rhythmic cyclic AMP changes in Chlamydomonas cells synchronized by temperature and light cycles in chemostat culture

Division in chemostat cultures of Chlamydomonas reinhardi was synchronized by daily cycles of both temperature and light. In response to 8 h cool (20 degrees C) - dim light/16 h warm (28 degrees C) - bright light cycles and continuous dilution that removed half the cells daily, the cells replicated nuclear DNA late in the warm-bright phase; released an average of two daughter zoospores early in the warm-bright phase of the next cycle. In these synchronized green algal cultures all ATP and most cAMP were intracellular; most cGMP (approximately 91%) was extracellular. Early in the warm-bright phase ATP doubled after which cAMP level fell 25%. During DNA replication cAMP level doubled, rising to a modest peak reached as replication ended.     

The influence of postnatal nutritional deprivation on the phospholipid content of developing rat lung.

It has been previously reported that fasting may result in decreased lung surfactant production. In order to investigate this relationship and the role of nutrition in lung phospholipid synthesis, 21-day-old rats were exposed for 60 h to one of five dietary regimens: standard rat chow (controls), fasting, pure glucose, pure fat, or pure protein. After the period of fasting there was a 33% decrease in lung protein content, but there was no change in DNA content. Exposure to any of the experimental diets resulted in a decrease in tissue total phospholipid and phosphatidylcholine content per lung, but not per unit lung protein. Similarly lung lavage phospholipid and phosphatidylcholine content was decreased by 25% after fasting when expressed per lung or per unit DNA, but not per unit protein. Pulmonary cholinephosphotransferase (EC 2.7.8.2) activity was decreased in the fasted animals and those fed the protein diet, but not in the glucose or fat-fed animals. The activities of acetyl-CoA carboxylase (EC 6.4.1.2) and microsomal fatty acid elongation were decreased in all the experimental groups except for the glucose-fed group. It is concluded that fasting results in a decrease in lung cell size but not in lung cell number. Total phospholipid and phosphatidylcholine content in lung tissue and lung lavage is decreased per cell but not per unit cell mass.