An Haemophilus influenzae mutant which inhibits the growth of HP1c1 phage

Summary A strain of Haemophilus influenzae, called hpm ^- inhibits the growth of phage HP1c1 but not S2. This inhibition is overcome by HP1c1ph mutants. Phage HP1c1 adsorbs normally to hpm ^- cells but only a small fraction of infected cells produce phage with a normal burst size or become lysogenic. When hpm ^- strains lysogenic for HP1c1 are induced, 100% of the cells yield phage. There is no degradation of phage DNA after infection of hpm ^- cells and HP1c1 can normally grow when its DNA is introduced into hpm ^- by transfection. The most probable explanation is that in hpm ^- cells the penetration of phage DNA is blocked. The hpm ^- property behaves as as unstable mutation.     

New Chimeric Analogues of Galanin: Synthesis and Effects on the Glucose-Induced Insulin Secretion

The solid-phase synthesis and in vitro assays on the glucose-induced insulin secretion from rat pancreatic islets of Langerhans with six new chimeric peptides were performed. All the peptides were built up of the N-terminal galanin (GAL) fragment or its analogues, linked to the C-terminal portion of substance P (SP) analogues or scyliorhinin I (SCY-I) analogues. Two strong antagonists of the inhibitory effect of galanin on the glucose-induced insulin release were found: [cycloleucine⁴]GAL(1-13)-SP(5-11)-amide and GAL(1-13)-[L-norleucine¹⁰]SCY-I(3-10)-amide.     

Biosynthesis of oleanolic acid glycosides in protoplasts isolated from Calendula officinalis L. roots

Many medicinal plants contain oleanane saponins in roots, however, only scarce data on their biosynthesis in this organ are available so far, including our previous results concerning Calendula officinalis plant. Thus, the purpose of the present work was to confirm the presumable biosynthetic pathway of oleanolic acid glycosides in roots of young C. officinalis plants. First of all, the effective method of isolation of protoplasts from C. officinalis roots was established. Then, isolated root protoplasts were supplied with radioactive precursors, [2-¹⁴C] mevalonate (MVA) and [3-³H] oleanolic acid (OL) and their transformations were studied with comparison to results obtained with excised roots. The penetration of both precursors into protoplasts was more rapid and effective than in the case of excised roots. The labeling of sterols and OL during the incubation with MVA showed that the isoprenoid pathway leading to triterpenoids was operative in excised roots as well as isolated root protoplasts. Moreover, the transformations of OL into two series of its glycosides, i.e. glucosides and glucuronides were investigated. It has been shown that both series of OL glycosides are synthesized in isolated root protoplasts in the same way as in excised roots of young marigold plants.     

Angiotensins II and IV stimulate the activity of tyrosine kinases in estrogen-induced rat pituitary tumors

The effects of angiotensin II (AngII) and its fragment 3-8 (angiotensin IV, AngIV) on tyrosine kinase (TK) activity in estrogen-induced rat pituitary tumor homogenates were studied. It was found that both angiotensin peptides increase the TK activity. AngIV was effective in a lower concentration and its maximal effect was greater as compared to that of AngII. Moreover, the specific inhibitors of aminopeptidase A (EC33) and of aminopeptidase N (PC18) significantly attenuated the stimulatory effect of AngII. Because the action of both aminopeptidases is necessary to convert AngII into AngIV, this finding suggested that the effect of AngII on TK activity is (at least in part) exerted via AngIV.     

The effects of oligomycin on content of adenylates in mesophyll protoplasts,chloroplasts and mitochondria from Pb<Superscript>2+</Superscript> treated pea and barley leaves

The effects of oligomycin on photosynthesis and respiration in relation to ATP production in chloroplasts and mitochondria were investigated in protoplasts isolated from the detached pea (Pisum sativum L cv. Iłowiecki.) and barley (Hordeum vulgare L. cv. Gunilla) leaves treated 5 mM Pb(NO₃)₂. The oligomycin (OM), an inhibitor of oxidative phosphorylation at 0.1 μM concentration caused the inhibition of photosynthesis rate in the protoplasts from both the control and the Pb-treated pea leaves. The respiration rate and ATP/ADP ratio in the protoplasts and the activity of ATPase in mitochondria, were also diminished in the control protoplasts. These effects were not observed in the protoplasts and mitochondria isolated from the Pb-treated leaves. Oligomycin, an inhibitor of photophosphorylation at 10 μM concentration decreased ATPase activity in chloroplasts from both the control and the Pb- treated leaves. Using the method of rapid fractionation of barley protoplasts it was shown that the ATP/ADP ratio in the mitochondria from Pb-treated leaves was largely suppressed (from 1.8 to 0.4) by OM under nonphotorespiratory conditions (high CO₂), whereas under photorespiratory conditions (low CO₂) this ratio was high (5.3) and under OM decreased less (to 3.1). Our results indicate that oligomycin, in organelle isolated from Pb-treated leaves, had no inhibitory effect on the mitochondrial ATPase, whereas it inhibited chloroplasts ATPase. We suggest that Pb ions affected the catalytic cycle and/or conformational changes of ATPase in pea chloroplasts differently than in mitochondria. The differences in Pb responses may reflect fine mechanisms for the regulation of ATP production in the plant cells under stress conditions.