Electron microscope study of antigen constituents of the phage DDVI and its h-mutant]

A comparative study of the fine antigen structure of phage DDVI and its h mutant using neutralization reaction and the electron microscopy of the phage-antibody complex has shown that the head and the tail of these phages have common protein constituents. The bulk of the antigens located in tail's fibers and in a base plates is also identical. However, the application of the cross-adsorbed sera has shown that the phage DDVI and the h mutant differ by only one specific antigen located in the distal part of tail's fibers.     

Trigger properties of gonadotropic hormones and oocyte factors in connection with the germinal epithelium of the rat testis]

In order to reveal possible stimulation of growth of the germinal epithelium of the rat's injured testicle the animals were injected follicle-stimulating and luteinizing hormones and their mixture as well as homogenate of fertilized egg-cells during two weeks. Changes of neurosecretion in large-cell nuclei of the anterior hypothalamus, cellular set in the adenohypophysis and the condition of the germinal epithelium in the gonad under study were investigated. Identical phenomena of reduction (having quantitative distinctions) took place due to effects of exogeneous honadotropins in neurosecretory nuclei and the adenohypophysis. In testicular tubules there occurred pronounced proliferation of the germinal epithelium, but spermatogenesis was absent. Egg-cell homogenate failed to cause changes in neurosecretion and adenohypophysis but resulted in completing the developmental cycle of the germinal epithelium with mature spermatozoa. The effect of gonadotropins upon the system hypothalamus-hypophysis is explained by feed-back mechanism, and the absence of spermatogenesis--by the lack of androgens. The rsults of egg-cell homogenate effects should be associated with local stimulating effects of DNA of the dividing egg-cell.     

De novo phosphatidylcholine synthesis is required for autophagosome membrane formation and maintenance during autophagy

ABSTRACT

Macroautophagy/autophagy can enable cancer cells to withstand cellular stress and maintain bioenergetic homeostasis by sequestering cellular components into newly formed double-membrane vesicles destined for lysosomal degradation, potentially affecting the efficacy of anti-cancer treatments. Using ¹³C-labeled choline and ¹³C-magnetic resonance spectroscopy and western blotting, we show increased de novo choline phospholipid (ChoPL) production and activation of PCYT1A (phosphate cytidylyltransferase 1, choline, alpha), the rate-limiting enzyme of phosphatidylcholine (PtdCho) synthesis, during autophagy. We also discovered that the loss of PCYT1A activity results in compromised autophagosome formation and maintenance in autophagic cells. Direct tracing of ChoPLs with fluorescence and immunogold labeling imaging revealed the incorporation of newly synthesized ChoPLs into autophagosomal membranes, endoplasmic reticulum (ER) and mitochondria during anticancer drug-induced autophagy. Significant increase in the colocalization of fluorescence signals from the newly synthesized ChoPLs and mCherry-MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) was also found on autophagosomes accumulating in cells treated with autophagy-modulating compounds. Interestingly, cells undergoing active autophagy had an altered ChoPL profile, with longer and more unsaturated fatty acid/alcohol chains detected. Our data suggest that de novo synthesis may be required to increase autophagosomal ChoPL content and alter its composition, together with replacing phospholipids consumed from other organelles during autophagosome formation and turnover. This addiction to de novo ChoPL synthesis and the critical role of PCYT1A may lead to development of agents targeting autophagy-induced drug resistance. In addition, fluorescence imaging of choline phospholipids could provide a useful way to visualize autophagosomes in cells and tissues.