Inhibition of the formation of lipid-linked intermediates in normal and transformed cells by a purified tunicamycin homologue

Summary The deffects of a purified homologue of tunicamycin (B₂-tunicamycin) on the biosynthesis of lipid-linked intermediates participating in protein glycosylation in normal embryonic fibroblasts, 3T3 and virally transformed (simian virus 40 and polyoma virus) mouse fibroblasts grown in culture were investigated. Long incubations (20 h) with the antibiotic caused a higher degree of inhibition of sugar incorporation into glycoproteins in transformed cells. However, the formation of lipid-linked intermediates was inhibited to a similar level in both cell types. When time dependent inhibition experiments were carried out using transformed cells, an earlier and stronger inhibition of the formation of lipid-oligosaccharides occurred (70% inhibition at 30 min). In 3T3 cells, prolonged incubation (6–8 h) was necessary in order to reach a similar degree of inhibition. Formation of lipid-sugar was also inhibited to a greater extent by B₂-tunicamycin in transformed cells. This inhibition was not clearly time dependent. Analysis of the newly synthesized glycolipids in 3T3 and in transformed cells after B₂-tunicamycin treatment have shown reduction in dolichyl-P-P-sugars as well as in other glycolipids. Dimethylsulfoxide (10%) and linoleic acid (0.5 mg/ml) markedly increased the level of tunicamycin activity in 3T3 cells while phosphatidylcholine (2 mg/ml) partially reversed it. The stronger and faster inhibition of the formation of lipid intermediates of the dolichyl-phosphate cycle caused by B₂-tunicamycin in transformed cells, described here for the first time, may therefore be due to differences in penetration of the antibiotic into these cells.Abbreviations DMEM Dulbecco's modified Eagle's medium - DMSO dimethylsulfoxide - MF mouse fibroblasts from Balb/c mouse embryos - 3T3 Balb/3T3 mouse fibroblastic line - SV40 Simian virus 40 - PY polyoma virus - TLC thin layer chromatography     

Triadimefon reduces transpiration and increases yield in water stressed plants

The total free amino acid pools in radicles of watermelon seeds, investigated during imbibition of water at 25°C, were higher under the most (darkness) than under the least (continuous broad spectrum far-red light) favourable light regime for germination. When seeds were imbibed in an appropriate osmotic solution of PEG-6000 (fully suppressing germination), in darkness or under continuous red or far-red light, the biochemical analyses of the radicles after 1,2,3 and 4 days from the onset of imbibition show that while the total soluble sugar content remains rather constant in all treatments, significant changes are observed in the total free amino acid pools. After the first day, a considerable increase characterizes the "darkness" pool in contrast to a moderate one under red, while the "far-red" pool remains constant. Ultimately, at 4 days, the three pools are 190,142 and 123% of the 0 day radicle one. The qualitative free amino acid determination of the 4 day darkness and far-red pools shows a considerably increased percentage contribution of glutamic acid, arginine and citrulline in the "darkness" pool. The free amino acid increase in non-illuminated radicles may be correlated to germinability; moreover, it is evidently a phytochrome-mediated, pre-germinatory event, probably due to the hydrolysis of proteins (known to be rich in glutamic acid and arginine), stored in the radicle.     

Emptying rates of single and double meals of different food quality from the stomach of the dab, Limanda limanda (L.)

In previous studies on gastric emptying time in Limanda , data were obtained which predict that food will empty from the stomach according to: after a temperature sensitive delay. This curve gives an excellent prediction of the emptying of both artificial and natural food items given as single meals when stomachs are sampled directly. However, when two meals are given 3 h apart, emptying rate depends on whether the two meals remain separate or are allowed to mix by omitting the binding agent. In the absence of a binder, both meals are slowed so that the overall emptying rate is as predicted by the equation. When binder is present, the first meal is not delayed and the overall gastric emptying rate is increased 35%.     

Growth and mortality of zebra fish, Brachydanio rerio (Hamilton Buchanan), maintained at two temperatures and on two diets

One hundred zebra fish per tank were maintained for 112 days at 24°C or 28°C in glass aquaria and fed a diet of flaked food made without cellulose (13.45 kJ g^?1, metabolizable energy, Type A) or with cellulose (8.71 kJ g^?1, metabolizable energy, Type B). Each experimental condition was repeated in triplicate (12 tanks). The weight of food given daily to the fish was based on daily records of survivors (from which mortality rates were calculated) and wet wt of fish (measured every 14 days) in each tank. All fish were fed with the same weight of food per day and the quantity of energy in the food in excess of standard metabolism (as a proportion of SM) was approximately 0–5 for fish maintained at 28°C and fed food B, 1–0 for fish maintained at 24°C and fed food B, 1–5 for fish maintained at 28°C and fed food A, and 2.2 for fish maintained at 24°C and fed food A. Non-ionized ammonia, nitrite and nitrate nitrogen in the tanks did not reach toxic levels although there was an increase in total ammonium nitrogen in one tank and a subsequent heavy mortality. It was assumed that this was caused by the build up of pathogenic bacteria. Apart from this tank, mortality was highest in tanks at 28°C with fish fed food A and second highest in tanks at 24°C with fish fed on the same diet. Growth was measured in units of length, wet and dry weights, carbon and energy. There was a good correlation (P < 0.001) between carbon (mgC mg^?1) and calorific (J mg^?1) values and a conversion factor of 46.2 J (mgC)^?1 was derived. Fish maintained at 24°C and fed food A had the highest rates of growth both in weight and in energy value per unit weight. Fish fed the same diet but kept at 28°C had the lowest growth rates. Both these groups of fish had the highest coefficients of variation in wet weights which increased during the experiment, indicating an increase in interaction within the tanks. There was agreement between the energy value of fish sampled for growth and a condition factor based on the length-weight relationships of fish remaining in the tanks. A correlation (P < 0.05) was found between instantaneous mortality and growth rates for fish between tanks when those maintained at 28°C and fed on food A were ignored.     

甜菊不同叶龄细胞结构及其甜菊糖甙含量分布的研究

本文报道甜菊(Stevia rebaudiana Bertoni)不同叶龄细胞结构与甜菊糖苷含量分布。应用电镜技术观察表明,现蕾期成叶细胞内具有内含物丰富的巨大液泡,这些内含物呈大小不一的颗粒或小泡。应用差速离心法,对甜菊成叶的叶肉细胞进行亚细胞分离,并对各部分进行甜菊糖苷的提取与微量测定。结果表明,甜菊糖苷主要存在于12000g的上清液(这部分主要包括液泡内含物和可溶性细胞质)。结合细胞结构和细胞化学研究结果,表明细胞质是合成UDPG的主要场所,在甜菊糖苷合成中具有重要作用。对不同叶龄叶片甜菊糖苷测定表明,现蕾期成叶的甜菊糖苷含量最高。从甜菊不同叶龄细胞结构和甜菊糖苷含量测定结果,现蕾期是甜菊叶片收割的最适时期。     

Clinical and Serological Response after Experimental Inoculation with Babesia Divergens of Newborn Calves with and without Maternal Antibodies

The influence of maternal antibodies on clinical and serological response after experimental inoculation with Babesia divergens of newborn calves was studied. Five calves, born to dams seropositive for B.divergens, (Group 1) had specific maternal antibodies when tested 12 h after their first feeding of colostrum. At that point they were inoculated i.v. with B.divergens infected erythrocytes. Five other calves, born to dams seronegative for B.divergens, (Group 2) had no Babesia specific maternal antibodies when inoculated at the same age. Babesia divergens organisms were demonstrated in blood smears from calves in both groups at some point 5 to 10 days p.i. All calves in both groups had B.divergens specific IgM antibodies at 7 to 17 days p.i. as shown by a modified IF-test. Specific IgG antibodies, transferred by colostrum, were found in all calves of Group 1 before inoculation of B.divergens. The IgG titre of these animals increased by a doubling dilution step at 11–25 days p.i. Among calves of Group 2 specific IgG antibodies were found at first between day 9 and 15 p.i. Both IgM and IgG antibody titres had to be investigated since demonstrated IgG antibodies can originate both from maternally transferred antibodies and from actively produced antibodies after an infection. There was no difference in clinical parameters; parasitaemia, PCV, Hb, and rectal temperature between the groups. This experiment gives evidence that there can be a resistance to bovine babesiosis in newborn calves independent of maternal antibodies.     

Effect of rhodium (III) complex on experimental carcinogenesis in the livers of rats treated with thioacetamide

Enzyme activities and protein content were determined in the cytosolic and mitochondrial fractions of liver homogenates obtained from Rh(III) complex-, thioacetamide- and thioacetamide + Rh(III) complex-treated rats. The Rh(III) complex administered to nonthioacetamide-treated rats produced no significant changes either in the enzymatic activities assayed or in the protein concentration. The Rh(III) complex administered to thioacetamide-treated rats produced significant restoration of the following altered values: cytosolic and mitochondrial aspartate aminotransferase, glutamate dehydrogenase, NADP-isocitrate dehydrogenase, and protein concentration. However, a further increase was produced in the activities of glucose-6-phosphate dehydrogenase and malic enzyme. These increases can be interpreted in terms of an enhancement of the NADPH-dependent detoxifying processes and of nucleic acid synthesis and repair.     

The in vitro synthesis and characteristics of ribosomal RNA in imaginal discs of Drosophila melanogaster

Summary Late third instar imaginal discs of Drosophila melanogaster cultured in vitro in Robb's tissue culture medium synthesize 38S, 28S and 18S ribosomal RNAs which are qualitatively indistinguishable from their in vivo synthesized counterparts (Fig. 1). As found in other insect systems, the 38S molecule appears to be the precursor for both the 28S and 18S rRNAs (Figs. 2, 3 and 4). The 28S rRNA and a portion of the 38S pre-rRNA shift in sedimentation value upon exposure to heat or dimethylsulfoxide (Figs. 5 and 8). Studies of the thermal denaturations of these molecules (Figs. 6, 7 and 9) indicate the existence of a single class of 28S rRNA, but three classes of 38S pre-rRNAs. The addition of -ecdysone to the in vitro culture medium stimulates the net amount of rRNA synthesized, increases the rate of processing of the 38S precursor and increases the relative amount of 18S material produced (Figs. 10 and 12).This work was supported in part by grants from the National Science Foundation (GB-8176) and from the Atomic Energy Commission (AT-04-3-34).Predoctoral Trainees, PHS Training Grant No. 2-Tl-GM367 from Research Training Grants Branch, National Institute of General Medical Sciences.1 For purposes of simplification we shall refer to the rRNA molecules of D. melanogaster as being 38S, 30S, 28S and 18S; however, it should be noted that these values are approximate (see Hastings and Kirby, 1966; Greenberg, 1969; Tartof and Perry, 1970).