Fluctuations du taux d'AMP cyclique et des activites adenylate cyclase et AMP cyclique-phosphodiesterase dans les cultures synchrones d'un procaryote, Nocardia restricta

Cultures of Nocardia restricta, a prokaryote from the group of Actinomycetes, can be synchronised by diluting, in a fresh growth medium, cells already in stationary phase. The synchronisation of the cultures is monitored by examining the synchrony of DNA replication.In these synchronised cultures, the intracellular cyclic AMP level exhibits rythmic oscillations with a period equal to the generation time of the culture. There is only one peak per generation. The average ratio of maximum to minimum concentrations is at least 3.Cyclic AMP accumulates also in the medium with a step pattern. It appears in the medium during maximum production of cyclic AMP in the cell.The specific activity of adenylate cyclase (EC 4.6.1.1) measured in the 30 000 × g pellet of cell-free extracts also oscillates and correlates well with fluctuations in the cyclic AMP level. At the end of exponential growth, cyclic-AMP phosphodiesterase (EC 3.1.4.17) is detectable in the cells. The specific activity of this enzyme measured in the 30 000 × g supernatant of cell-free extracts shows also an oscillating pattern.To our knowledge it is the first time that such oscillations in the metabolism of cyclic AMP are described among prokaryotes. It is now possible to look at a link between this phenomenon and the cell cycle of the organism.     

Variations in mitochondrial monoamine oxidase during progressive starvation in the brain of developing rats

Effects of progressive starvation of 12, 24, 48 and 60 h upon brain mitochondrial monoamine oxidase activity were studied. The enzyme activity was determined by three different substrates: ¹⁴C-labeled tryptamine, dopamine and kynuramine. With dopamin as substrate, the enzyme activity showed decline during 24 and 48 h starvation. Monoamine oxidase when determined by tryptamine as the substrate, showed a decreased after 60 h of starvation. The use of kynuramine as substrate also produced a decrease in enzyme activity after 48 and 60 h of starvation. Refeeding the 60-h-starved rats for the following 24 h resulted in further decrease of monoamine oxidase activity of brain mitochondria from the 60 h starved values. The results suggest that oxidative deamination of biogenic amines is greatly inhibited during progressive starvation and remains low even after feeding the 60 h starved rats for 24 h.     

Stimulation of dieldrin elimination by a thiouracil derivative and DDT in the rat: Enhancement of dieldrin oxidative metabolism?

Oral treatment of rats with either DDT or 1-benzyl-2-thio-5,6-dihydrouracil (BTDU) enhanced the elimination of intraperitoneally administered [¹⁴C]dieldrin. Both DDT and BTDU caused a severalfold increase in the urinary elimination of [¹⁴C]dieldrin. The increase in [¹⁴C]dieldrin elimination in the feces was less pronounced.     

Structure of sterically hindered aryl derivatives of five-membered nitrogen containing heterocyclicortho-analogs of POPOP

The molecular conformation of three newly synthesized, sterically hindered aryl derivatives of five-membered nitrogen-containing heterocyclicortho-analogs of POPOP were studied by X-ray analysis and vibrational spectroscopy. It was shown that molecules of the compounds in the crystalline state and in solution are non-planar and asymmetric.     

Acid phospholipase A1 and A2 in the cells, and subcellular redistribution of their activities in the cells infected with measles virus

Presence of soluble acid phospholipase A₁ and A₂ was confirmed in the (lysosomes + mitochondria) fraction of cultured human amnion cell line, FL cells. Activity of these enzymes and acid phosphatase was detected in the cytosol fraction of FL cells harvested at 59 hr after infection with measles virus, indicating that these enzymes in the (lysosomes + mitochondria) fraction were released to the cytosol fraction during the maturation of measles virus in the cells. Further, it was confirmed that the release of acid phospholipase A₁ and A₂ almost paralleled the development of cytopathic effect.