Unique sequence, ski, in Sloan-Kettering avian retroviruses with properties of a new cell-derived oncogene.

The Sloan-Kettering viruses (SKVs) are a group of transforming retroviruses that were isolated from chicken embryo cells which had been infected with the avian leukosis virus transformation-defective Bratislava 77 (tdB77). Each of the SKV isolates was shown to contain multiple genomes of different sizes indicating the presence of several viruses in addition to tdB77. To identify and characterize the putative transforming gene(s) of the SKVs, we used hybridization selection to isolate the fraction of a representative cDNA which was SKV specific. Both solution and blot hybridization studies with viral RNAs showed that the specific probe contained a sequence, ski, that was at least partially held in common by the multiple SKV genomes. This conclusion was confirmed by the observation that a molecularly cloned ski probe also hybridized to each of the multiple SKV genomes. Southern blots of chicken DNA revealed homologs of ski (c-ski) which were not associated with endogenous viral loci. Results showing that c-ski was expressed in polyadenylated cytoplasmic RNA of uninfected chicken cells indicated that it is a functional gene. Other data showed that c-ski was conserved in avian and mammalian evolution, suggesting a functional role for the gene in species other than chickens. Using ski cDNA in solution hybridizations with viral RNAs and in Southern blot hybridization with cloned retroviral oncogenes, we did not detect any relationship between ski and any of 15 previously identified oncogenes.     

A tetrapeptide isolated from hamster embryo with central opiate properties on gastrointestinal motility but not on pain perception

The effects of centrally administered kentsin (H-Thr-Pro-Arg-Lys-OH) on intestinal motility and on pain perception were investigated in rats chronically equipped with lateral ventricle catheters. Intestinal motility was recorded electromyographically from electrodes placed on the duodeno-jejunum; analgesia was evaluated by the hot-plate and tail-flick tests. Kentsin (4.0 ug/kg), injected intracerebroventricularly (ICV) 2 hours after the beginning of a meal, restores the "fasted" i.e. the migrating myoelectric complex of intestinal motility, while a 5 times higher dose administered subcutaneously was inactive. The ICV effect of kentsin was blocked by previous ICV administration of naloxone (400 ug/kg). In contrast, kentsin administered ICV (40 ug/kg) or SC (200 ug/kg) did not affect significantly (P greater than 0.05) the time latency in the two analgesic tests during 90 minutes after its administration and did not significantly modify the analgesic effects of (D5-Ala2, Met5) enkephalinamide. We conclude that kentsin when centrally administered acts on opiate receptors to alter gastrointestinal motility but without effects on pain perception.     

Structure-activity relationships of nitro and methyl-nitro derivatives of indoline, indole, indazole and benzimidazole in Salmonella typhimurium

The mutagenic activities of eleven nitro derivatives and eleven N-methyl-nitro derivatives of indoline, indole, indazole and benzimidazole were investigated in Salmonella TA98 and TA100. The presence of a nitro group at C4 or C7 resulted in only weakly or nonmutagenic compounds, while a nitro group at C2, C5 or C6 usually resulted in measurable mutagenic activity in the non-N-methylated compounds. Methylation of a ring nitrogen usually reduced the mutagenic activity of these nitroheterocyclics except 2-nitro-benzimidazole, which resulted in a better than 300-fold increase in mutagenic activity. A proposed mechanism for the increased mutagenic activity obtained by methylation of imidazole nitrogens may provide insights into the reasons for the potent mutagenicities observed for several similarly methylated cooked-food mutagens.     

Reward partitioning in Capparis spp. along ecological gradient

Summary The genus Capparis is represented in Israel by three taxons of the section spinosa. The pollinators of the three taxa are hawkmoths, crepuscular bees of the genus Proxylocopa and various daily bees. However, the efficiency of the different pollinators is very varied with respect to the individual taxons. Hawkmoths were frequently observed as pollinators of C. spinosa var. aravensis and C. ovata, but rarely on C. spinosa var. aegyptia. All the other bees, on the other hand, were found abundantly on all three taxons, all over the country. The three taxa all provide different rewards for their particular pollinators. Bees visiting C. spinosa var. aegyptia are provided with a lot of pollen but a relatively small amount of nectar, with a low sugar content. C. spinosa var. aravensis and C. ovata (the flowers visited more by hawkmoths), have less pollen but a higher amount of nectar which has a higher concentration of sugar. In drier habitats the emphasis of the reward provided by the flowers is nectar, whilst in the Mediterranean habitats it is the pollen which is the reward, without any connection to the systematic origin of the plant.     

Effect ofAzospirillum inoculation on nitrogen fixation and growth of several winter legumes

Summary Inoculation of naturally nodulatedPisum sativum L. (garden pea) withAzospirillum in the greenhouse caused a significant increase in nodule numbers above controls. Field inoculation of garden peas in the winter 1981–1982 andCicer arietinum L. (chick pea), in winter 1982–1983, withAzospirillum one week after plant emergence, produced a significant increase in seed yield, but did not affect plant dry matter yield. ForVicia sativa L. (vetch) grown in soil in the greenhouse and in the field for forage, winter 1980–1981, inoculation significantly increased dry matter yield, %N, N-content, and acetylene reduction (nitrogen fixation) activity. InHedysarum coronarium L. (sulla clover), winter 1981–1982, inoculated with both its specificRhizobium (by the slurry method) andAzospirillum, 7 days after emergence, there was an increase in acetylene reduction above controls inoculated withRhizobium alone. These results suggest that it is possible, under conditions tested in this work, to increase nodulation, nitrogen fixation, and crop yields of winter legumes by inoculation withAzospirillum.     

Estimation of symbiotically fixed nitrogen in field grown soybeans: An application of natural15N/14N abundance and a low level15N-tracer technique

Summary Plants from agricultural and natural upland ecosystem were investigated for¹⁵N content to evaluate the role of symbiotic N₂-fixation in the nitrogen nutrition of soybean. Increased yields and lower δ¹⁵N values of nodulating soybeansvs, non-nodulating isolines gave semi-quantitative estimates of N₂ fixation. A fairly large discrepancy was found between estimations by δ¹⁵N and by N yield at 0 kg N/ha of fertilizer. More precise estimates were made by following changes in plant δ¹⁵N when fertilizer δ¹⁵N was varied near¹⁵N natural abundance level. Clearcut linear relationships between δ¹⁵N values of whole plants and of fertilizer were obtained at 30 kg N/ha of fertilizer for three kinds of soils. In experimental field plots, nodulating soybeans obtained 13±1% of their nitrogen from fertilizer, 66±8% from N₂ fixation and 21±10% from soil nitrogen in Andosol brown soil; 30%, 16% and 54% in Andosol black soil; 7%, 77% and 16% in Alluvial soil, respectively. These values for N₂ fixation coincided with each corresponding estimation by N yield method. Other results include: 1)¹⁵N content in upland soils and plants was variable, and may reflect differences in the mode of mineralization of soil organics, and 2) nitrogen isotopic discrimination during fertilizer uptake (δ¹⁵N of plant minus fertilizer) ranged from −2.2 to +4.9‰ at 0–30 kg N/ha of fertilizer, depending on soil type and plant species. The proposed method can accurately and relatively simply establish the importance of symbiotic nitrogen fixation for soybeans growing in agricultural settings.     

Identification with Monoclonal Antibodies of a Second Antigenic Domain on Avena Phytochrome that Changes upon Its Photoconversion

An enzyme-linked immunosorbent assay that revealed an antigenic difference between the red-absorbing and far-red-absorbing forms of phytochrome (Pr and Pfr, respectively) near its amino terminus (Cordonnier M-M, H Greppin, LH Pratt 1985 Biochemistry 24: 3246-3253) was used to screen eight additional monoclonal antibodies directed to phytochrome from etiolated oats. While six of these antibodies detected Pr and Pfr with equal affinity, two of them, designated Oat-9 and Oat-16, bound to Pfr 1.6 to 2.3 times better than to Pr. Competitive enzyme-linked immunosorbent assays indicate (a) that Oat-9 and Oat-16 probably bind to the same domain on phytochrome and (b) that this domain is at least 3.5 nanometers away from the epitope near its amino terminus that was shown earlier to change upon phototransformation. Neither the absorbance spectra of Pr and Pfr, nor the rate of dark reversion of Pfr to Pr, was influenced by the presence of Oat-9. Immunoblotting of sodium dodecyl sulfate polyacrylamide gels after electrophoretic separation of phytochrome fragments obtained by endogenous proteolytic digestion indicates that Oat-16 binds to an epitope located on the chromophore half of this chromoprotein. The observation that the epitope recognized by Oat-9 and Oat-16 is also present on at least some of the immunochemically distinct phytochrome that is obtained from green oat shoots (Shimazaki Y, LH Pratt 1985 Planta 164: 333-344), together with the evidence that this epitope undergoes a change upon photoransformation, indicates that it may play an important role in phytochrome function.