The activation process of Arabidopsis thaliana A1 gene encoding the translation elongation factor EF-1α is conserved among angiosperms

In Arabidopsis thaliana, the activation process of the A1 EF-1 gene depends on several elements. Using the GUS reporter gene, transient expression experiments have shown that mutations of upstream cis-acting elements of the A1 promoter, or the deletion of an intron located within the 5 non-coding region, similarly affect expression in dicot or monocot protoplasts. The results reported here strongly suggest that this 5 intron is properly spliced in Zea mays. We show that two trans-acting factors, specifically interacting with an upstream activating sequence (the TEF 1 box), are present in nuclear extracts prepared from A. thaliana, Brassica rapa, Nicotiana tabacum and Z. mays. In addition, a DNA sequence homologous to the TEF 1 box, found at approximately the same location within a Lycopersicon esculentum EF-1 promoter, interacts with the same trans-acting factors. Homologies found between the A. thaliana and L. esculentum TEF 1 box sequences have allowed us to define mutations of this upstream element which affect the interaction with the corresponding trans-acting factors. These results support the notion that the activation processes of A. thaliana EF-1 genes have been conserved among angiosperms and provide interesting data on the functional structure of the TEF 1 box.     

Effect of imazaquin on absorption,translocation, and pattern of distribution of chlormequat chloride in winter wheat

The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL^* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)¹⁴C-chlormequat chloride, (2) CYCOCEL^* CL containing¹⁴C-chlormequat chloride, and (3) CYCOCEL^* CL containing¹⁴C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the¹⁴C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant.     

Reverse-phase high-pressure liquid chromatography of uridine diphosphate N-acetylmuramyl peptide precursors of bacterial cell wall peptidoglycan

A series of seven different UDP-N-acetylmuramyl peptide precursors of bacterial cell wall peptidoglycan was examined by reverse-phase high-pressure liquid chromatography. Mixtures of these compounds were successfully and rapidly analyzed by using a Waters μBondapak C₁₈ column as a stationary phase and isocratic elutions with 0.05 m ammonium phosphate or formate buffers of appopriate pH. Furthermore, their accurate quantitation could also be readily achieved by reverse-phase high-pressure liquid chromatography. All these techniques should be extremely useful for the purification of these compounds and for a wide range of biochemical studies concerning the cytoplasmic steps of the biosynthesis of peptidoglycan.     

Ans fluorescence and electrokinetic potential of activated lymphocytes by con A or LPS in vivo

The $\text{in vivo}$ effect of Concanavalin A (Con A), or bacterial lipopolysaccharide (LPS) on mouse spleen cell populations was investigated. The membrane fluorescence changes of activated splenic lymphocytes were studied during two weeks after the injection of polyclonal immunogens. Experiments were performed with the hydrophobic fluorescent probe: 1-anilino-8-naphthalene sulphonate (ANS). The kinetic studies further indicated that the course of fluorescence changes may considerably vary depending on both immunogens. These fluorescence intensity changes would be in direct relation to the electrokinetic surface potential changes of activated lymphocytes, as assessed by the electrophoretic mobility analysis. By comparison with the inverse relationship observed in our previous study, it would be concluded that the relation (direct or inverse) between ANS fluorescence and electrokinetic potential depends on the net electrical charge of the antigens used.     

Genetic Diversity and Temporal Variation in the E. COLI Population of a Human Host

Electrophoretic techniques were employed to study variation in chromosomal genes encoding enzymes and in the distribution of cryptic plasmids in the E. coli population of a human host over an 11-month period. Thirteen of the 15 enzymes studied were polymorphic, and mean genetic diversity per locus was 0.39. Among 550 clones isolated from fecal samples, protein electrophoresis revealed 53 distinct electrophoretic types (ETs). Most ETs appeared on only one or a few days and were considered transients, but two (ET-12 and ET-13) were observed many times over extended periods and represented residents. Complete turnover in the transient ETs in the population occurred in periods of from two weeks to a month. ETs appearing in one month showed no particular genetic similarity to those of the previous month. — All but 4 of the 53 ETs carried one or more "cryptic" plasmids with molecular weights ranging from 1 to 80 megadaltons. With few exceptions, the plasmid composition of each ET was unique. In the course of the 11-month sampling period, there were changes in the plasmid profiles of the resident strains ET-12 and ET-13, and also in the profile of a recurrent strain, ET-2, which was isolated on four days. Modification of the plasmid profile of ET-12 involved the sequential addition of relatively high molecular weight bands. For ET-2 and ET-13, the changes in the plasmid profiles were radical, suggesting invasions of new cell types rather than merely the addition and deletion of plasmids. — The results of this study provide three lines of evidence that recombination plays a minor role in the generation of genetic diversity in the E. coli population of a single host. (1) Several pairs of loci were in strong linkage disequilibrium; compared to a randomly generated array of genotypes, the sample of ETs contained an excess of pairs differing at one or two loci and too many pairs with highly distinctive combinations of electromorphs. (2) In most cases where pairs of ETs differed at a single locus and, therefore, could reasonably have been generated by phage- or plasmid-mobilized gene transfer, the plasmid profiles of the pair members were radically different and/or the potentially transmitted alleles were not present in other ETs in the population. (3) Although ET-12 was abundant, being represented by 252 of the 550 clones sampled, the electrophoretic type most similar to ET-12 different from it at six loci, and ET-12 carried two unique alleles. We conclude that most of the genetic diversity observed in this human host is a consequence of successive invasions of E. coli genotypes.     

Patterns of chromosome segregation in chinese hamster × mouse cell hybrids between permanent cell lines and thymus cells

Hybrids between a tumorigenic Chinese hamster cell line (DC3F-aza) and normal mouse thymus cells very rapidly lost most of their mouse chromosomes, whereas hybrids between tumorigenic mouse cell lines (either Cl.1D of L cell line origin, or PCC4-aza1 teratocarcinoma cells) and normal Chinese hamster thymus cells lost most of their hamster chromosomes. From three such fusion experiments, 20 cell lines were developed which all followed the same evolution, namely, the elimination of the majority of the chromosomes contributed by the normal thymus cell. In some hybrids, the elimination process resulted in the total absence of intact chromosomes contributed by the thymus cell parent. Such hybrids were distinguished from revertant parental cells growing in the selective hybrids were distinguished from revertant parental cells growing in the selective medium by the presence of at least one enzyme in their cell extracts which displayed the electrophoretic mobility of the enzyme of the thymus cell parent. These observations, together with data from other reports, suggest that, as a rule, interspecific cell hybrids which develop upon fusion between normal diploid cells and tumorigenic cell lines maintain the chromosomes of the latter and eliminate preferentially many or most of the chromosomes contributed by the normal cell parents, independent of the respective species of the parental cells.     

Secondary response of in vitro-primed human lymphocytes to allogeneic cells

In vitro-primed human lymphocytes proliferate in a secondary mixed lymphocyte reaction (MLR) under the control of MLR-S specificities. HL-A antigens are unable to induce a secondary Proliferation. In familial haploidentical combinations, the secondary proliferation is specific for the priming MLR-S specificity, i.e., as early as 24 to 48 hours after the re-stimulation, a clearcut response is observed toward the sensitizing MLR-S specificity. The secondary response is reflected in acceleration of the reaction rather than in the peak of (³H) TdR uptake. However, when either haploidentical familial primed responding cells or unrelated cells primed toward MLR-S homozygous cells were used, no early typing response was observed against unrelated cells. The level of (³H) TdR incorporation toward cells which possessed and those which did not possess the priming specificity was identical until day 3–4. Noneless, the peak response toward cells possessing the priming MLR-S specificity occurs regularly 24 to 48 hours prior to the peak response toward the cells negative for the priming specificity (day 3–4 as opposed to day 5). Technical improvements are therefore needed before such a technique will provide a clearcut MLR-S typing methodology.