Studies on the synthesis of CDP-diacylglycerol: Stimulation by GTP and inhibition by ATP and fluoride

The rat liver microsomal enzyme CTP: phosphatidate cytidylyltransferase (EC 2.7.7.41) which catalyzes the formation of CDP-diacylglycerol has been found to be markedly stimulated by GTP. The requirement for GTP is absolute, the novel GTP analogues such as guanosine 5′-[β,γ-methylene]-triphosphate, guanosine 5′-[α,β-methylene]-triphosphate, guanosine 5′-[β,γ-imido]-triphosphate and guanosine 3′-diphosphate 5′-diphosphate are without significant effect. Maximal stimulation occurs at 1 mM GTP. ATP at a concentration of 5 mM totally inhibits the formation of CDP-diacylglycerol even in the presence of optimal GTP concentration. Analogues of ATP such as adenosine 5′-[α,β-methylene]-triphosphate, adenosine 5′-[β,γ-methylene]-triphosphate and adenosine 5′-[β,γ-imido]-triphosphate are without effect on the reaction. The addition of fluoride (8 mM) likewise abolishes the stimulatory effect of GTP.     

The role of retinol in the initiation of sporangiophores of Phycomyces blakesleeanus

The initiation of sporangiophores of Phycomyces was analyzed under oxygen-limiting conditions. Mutants lacking -carotene have a higher oxygen threshold than the wild type depending on the residual amount of -carotene. The supersensitivity to low oxygen tension is specific for sporangiophore initiation and can be suppressed by addition of either retinal, retinol or retinol acetate to the medium. It is suggested that retinol is a natural regulator of differentiation in Phycomyces.     

Effects of pyrrol-carboxylic acid derivatives on the growth of coliphages.

Effects of 14 pyrrol-carboxylic acid derivatives and analogues (PY-compounds) on the growth of coliphage MS2 using E. coli E102 (Hfr) as the host were measured by the agar double-layer method. Enlargements of plaque size were observed with 7 PY-compounds but increase in plaque numbers was not induced. These enlargements of plaque size were specific to RNA coliphages MS2, GA and qbeta and not found with DNA coliphages delta AC and T4. Furthermore, the interaction between PY-compound PY-10 and the coliphage MS2 was dependent on the host bacterium (indicator strain). When E102 (Hfr) was used, the enlargement was marked, in the case of substrain W1895 (Hfr) it was less, while in the case of substrain W6 (F+) it was undetectable. The one-step growth of the phage MS2 and the production of intracellular phage MS2 were little affected by the PY-compound PY-10. However, the rate of one-step growth was increased in the early stage after infection. Accordingly, the enlargements of plaque size by the PY-compounds might be correlated with an increase in rate of release of phage particles.     

Immunochemical analysis of the carbohydrate moiety of yeast killer toxin K28

Killer toxin K₂₈, a 16 kd protein secreted by the wine yeast Saccharomyces cerevisiae strain 28, was reversibly bound by a column of Concanavalin A-Sepharose, confirming its glycoprotein nature. HPLC analysis of acid hydrolyzates of K₂₈ toxin as well as Western-blots of -eliminated and/or endo H-treated killer toxin preparations probed with polyclonal -toxin antibodies revealed that the carbohydrate moiety of K₂₈ consists of D-mannose only, which is O-glycosidically linked via Ser/Thr residues to the protein part. The change in gel mobility of K₂₈ after -elimination was caused by a decrease in molecular mass of about 1,800, corresponding to a carbohydrate moiety of 10 mannose residues per killer toxin molecule.     

Decidual cell reaction induced by prostaglandin F2α in the mature oöphorectomized rat

Summary Sprague-Dawley rats were oöphorectomized and after a 2–3 week recovery period were given daily injections of progesterone (2.0 mg/0.1 ml) for six consecutive days. On the fourth day of progesterone treatment 0.2 mg of estradiol 17 was given in addition and the right uterine cornua were subjected to one of five experimental maneuvers. On the sixth day of progesterone treatment the uterine cornua were weighed and processed for light and electron microscopy. The weights of all left cornua (84.6 +- 3.7 mg) and the right cornua of PBS-injected (93.3 +- 11.5 mg) and sham operated uteri (83.6 +- 19.8 mg) were comparable. A significant increase (p<0.001) in weight was found in cornua that received PGF₂ (144 +- 6.7 mg), PGF₂ with mild local trauma (scratch) (146 +- 28.0 mg), and scratch alone (162 +- 12.7 mg). The majority of cornua treated by scratch alone, or by PGF₂ with or without scratch, showed a decidual cell reaction by light microscopy and had a significantly higher mitotic index than those treated with saline, or by sham operation. When specimens were evaluated for the presence of the OCR, the highest rank was found in tissues treated by scratch alone or by PGF₂ with or without scratch. Morphometric evaluation by light microscopy indicated that the extent of decidualization in PGF₂-treated tissue was comparable to that of scratchtreated tissue. Ultrastructural observation of PGF₂-treated tissue revealed that decidual cells closely resembled those treated with scratch. However, electron microscopic morphometry revealed that cells that responded to PGF₂ had higher volume and surface densities of organelles associated with metabolic activity than did cells responding to scratch alone. These results demonstrate that locally administered PGF₂ can initiate, in the hormonally prepared mature oöphorectomized rat, a DCR comparable to that induced by local trauma.     

Stimulation of the anaerobic growth ofSalmonella typhimurium by reduction ofl-carnitine,carnitine derivatives and structure-related trimethylammonium compounds

In view of the development of al-carnitine deficiency, the metabolism ofl-carnitine and structure-related trimethylammonium compounds was studied inSalmonella typhimurium LT₂ by means of thin-layer chromatography (TLC).l-Carnitine, crotonobetaine and acetyl-l-carnitine stimulated the anaerobic growth in a complex medium significantly. The stimulation depended on the formation of -butyrobetaine. The reduction ofl-carnitine proceeded in two steps: (1) Dehydration of thel-carnitine to crotonobetaine, (2) hydrogenation of crotonobetaine to -butyrobetaine. The reduction of crotonobetaine was responsible for the growth stimulation. Terminal electron acceptors of the anaerobic respiration such as nitrate and trimethylamine N-oxide, but not fumarate, suppressed the catabolism ofl-carnitine completely. Glucose fermentation, too, inhibited the reduction ofl-carnitine but optimal growth with a high carnitine catabolism was achieved byd-ribose. The esters of carnitine with medium- and long-chain fatty acids inhibited the growth considerably because of their detergent properties.Abbreviations TLC thin-layer chromatography