The Role of Ethylene in the Inhibition of Rooting under Low Oxygen Tensions

A 60-fold increase in ethylene content was observed in stem cuttings of chrysanthemum (Chrysanthemum × morifolium Ramat.) held in aero-hydroponics under anoxic conditions during the 8 to 12 days necessary for adventitious root formation. Ethylene, 1-aminocyclopropane-1-carboxylic acid, and 10-(malonylamino) cyclopropane-1-carboxylic acid contents were highest in the immersed portion of the cuttings, but there was substantial ethylene produced by the anoxic, misted portions of the cutting above the liquid. Application of ethylene (10 microliters per liter) to chrysanthemum cuttings stimulated root development in cuttings held in high dissolved oxygen concentrations (8.0 milligrams per liter). Since the application of ethylene did not inhibit rooting in cuttings held at low dissolved oxygen concentrations (2.0 milligrams per liter), the inhibition of rooting under low oxygen concentrations is not mediated by the observed increase in endogenous ethylene content.     

Macroaggregated calcifications in cancer of the breast

Breast cancer is characterized by the presence of multiple aggregated microcalcinates. However, the authors managed to detect 6 cases of breast cancer with macroaggregate calcifications, of which 3 were not adequately imaged on mammograms. Morphological investigations in all cases have shown that macroaggregate calcifications that are typical of benign lesions, are also detectable in breast cancer. The absence of an image of calcification on mammograms is probably accountable for by its various density.     

Interrelationships among various measures of upper body strength assessed by different contraction modes Evidence for a general strength component

Two studies were conducted in 83 college men to determine the degree of generality of individual differences in upper body muscular strength assessed by different testing modes. In study 1 (N = 43), correlations were computed between four measures of upper body strength using the bench press movement, maximal isokinetic (0.09 rad.s-1), maximal fast (0.126 m.s-1) and slow (0.037 m.s-1) hydraulic, and one repetition maximum (1-RM) free weight bench press (BP). Compared to free weight BP, maximal strength during isokinetic and slow hydraulic BP was approximately 29% and approximately 8% larger, and fast hydraulic BP strength was approximately 63% lower (p less than 0.05). Simple linear regression of isokinetic BP on 1-RM BP yielded r = 0.79, error of prediction (SE) = 12%, and generality = 81%. The corresponding averaged values for the regression of slow and fast hydraulic BP on free weight 1-RM BP were r = 0.77, SE = 13.5%, and generality = 84%. In Study 2 (N = 40), testing included maximal isokinetic concentric and eccentric arm flexion and extension at 0.524, 1.570, and 2.094 rad.s-1. The ratio of concentric to eccentric torque at the 3 speeds averaged 0.68 (flexion) and 0.70 (extension), and eccentric torques were 32% and 30% greater than concentric torques (p less than 0.05). The linear regression between concentric vs. eccentric flexion and extension torques at the three velocities yielded an average r = 0.80, SE = 13.7%, and generality = 73%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation and characterization of cDNA clones encoding the 17.9 and 8.1 kDa subunits of Photosystem I from Chlamydomonas reinhardtii

cDNA clones encoding two Photosystem I subunits of Chlamydomonas reinhardtii with apparent molecular masses of 18 and 11 kDa (thylakoid polypeptides 21 and 30; P21 and P30 respectively) were isolated using oligonucleotides, the sequences of which were deduced from the N-terminal amino acid sequences of the proteins. The cDNAs were sequenced and used to probe Southern and Northern blots. The Southern blot analysis indicates that both proteins are encoded by single-copy genes. The mRNA sizes of the two components are 1400 and 740 nucleotides, respectively. Comparison between the open reading frames of the cDNAs and the N-terminal amino acid sequences of the proteins indicates that the molecular masses of the mature proteins are 17.9 (P21) and 8.1 kDa (P30). Analysis of the deduced protein sequences predicts that both subunits are extrinsic membrane proteins with net positive charges. The amino acid sequences of the transit peptides suggest that P21 and P30 are routed towards the lumenal and stromal sides of the thylakoid membranes, respectively.Abbreviations OEE1, 2 and 3 oxygen evolution enhancer proteins 1, 2 and 3 - Rubisco ribulose bisphosphate carboxylase/oxygenase - PS photosystem - P21 and P30 C. reinhardtii thylakoid polypeptides 21 and 30     

Transformation of Claviceps purpurea using a bleomycin resistance gene

Summary To develop a DNA-mediated transformation system for Claviceps purpurea a vector was constructed using a bleomycin-resistance gene (bleo ^R) fused in frame to the Aspergillus nidulans trp C promoter as a dominant selection marker. The construct was shown to be functional in Aspergillus nidulans and Aspergillus niger and used to transform a wild strain of Claviceps purpurea. Transformats were obtained at low frequencies; they were shown to contain transforming DNA integrated into the chromosomal DNA, probably in multimeric copies and at multiple sites. Combined Southern, Northern and resistance level analysis indicate that the A. nidulans promoter is functional in C. purpurea.Dedicated to Professor Dr. Dr. h. c. K. Esser on the occasion of his 65^th birthday     

Mitogen-responsive S6 kinase

Many cell lines respond to mitogenic stimuli (serum, growth factors) with rapid phosphorylation of the ribosomal protein S6 at several serine sites. We have tried to identify the protein kinase(s) mediating this effect of growth stimuli. Examining post-DEAE chromatography fractions of S49 kin- cell extracts, we could detect a highly active effector-independent S6 kinase with specificity for serine residues. The study was extended to the presumably homologous human enzyme, using HeLa S3 cells as model system. Activity yields increased up to sevenfold when exhausted HeLa cells were supplied with fresh medium plus serum. The enzyme uses ATP, not GTP, as cosubstrate, 40-S or 80-S (reassociated from subunits) ribosomal particles being substrate. The optimal K+ concentration, measured at 3 mM Mg2+, is 35 mM. Under optimized assay conditions S6 phosphorylation proceeded faster in vitro than it appeared to do in vivo. The apparent Mr of the enzyme, as estimated by gel filtration on Sephadex G-100, is 56,000 (determination in the presence of 200 mM KCl in 25 mM phosphate buffer). Tighter binding to DEAE-Sephacel and higher specificity for S6 distinguishes this enzyme from the following S6-phosphorylating protein kinases: protein kinase C, protease-activated kinase II, histone-4 phosphotransferase and an enzyme with the properties of casein kinase I. In published summaries of observations shown here and in a follow-up study with chick embryo fibroblasts, the enzyme(s) has been referred to as mitogen-responsive S6 kinase(s) [Martini, O. H. W. and Lawen, A. (1985) in Hormones and cell regulation (Dumont, J. E., Hamprecht, B. and Nunez, J., eds) vol. 9, pp. 411-412, Elsevier Company, North-Holland, Amsterdam; Lawen, A. and Martini, O. H. W. (1985) FEBS Lett. 185, 272-276].     

Insulin-induced S6 kinase activation in HeLa cells and its reversal by hyperthermic stress

Insulin treatment of HeLa S3 cells activates an S6-phosphorylating protein kinase. Although this enzyme has chromatographic properties resembling those of described proteolytic fragments of other protein kinases, namely protein kinase C, protease-activated kinase II and histone-4 protein kinase, and although insulin has been proposed by others to cause S6 phosphorylation via proteolytic protein kinase activation, the insulin-induced increase in S6-kinase activity described here is probably not due to proteolysis. Rather, the activity indicates the existence, in HeLa cells, of an interconvertible S6 kinase, since the insulin-induced activity increase was rapidly reversed under hyperthermic stress, and since this effect of hyperthermia was itself reversible. The S6-kinase activities from serum- and from insulin-stimulated HeLa cells resemble each other closely and are likely to represent the same enzyme. The enzyme may therefore mediate both signals delivered by mitogens and the insulin signal. Analysed at an in vitro transfer of 1 mol phosphate/mol S6, this S6 kinase activity does not phosphorylate the (principal) S6 site recognized by the cAMP-dependent protein kinase.     

Linkage and the Maintenance of Heritable Variation by Mutation-Selection Balance

The role of linkage in influencing heritable variation maintained through a balance between mutation and stabilizing selection is investigated for two different models. In both cases one trait is considered and the interactions within and between loci are assumed to be additive. Contrary to most earlier investigations of this problem no a priori assumptions on the distribution of genotypic values are imposed. For a deterministic two-locus two-allele model with recombination and mutation, related to the symmetric viability model, a complete nonlinear analysis is performed. It is shown that, depending on the recombination rate, multiple stable equilibria may coexist. The equilibrium genetic and genic variances are calculated. For a polygenic trait in a finite population with a possible continuum of allelic effects a simulation study is performed. In both models the equilibrium genetic and genic variances are roughly equal to the house-of-cards prediction or its finite population counterpart as long as the recombination rate is not extremely low. However, negative linkage disequilibrium builds up. If the loci are very closely linked the equilibrium additive genetic variance is slightly lower than the house-of-cards prediction, but the genic variance is much higher. Depending on whether the parameters are in favor of the house-of-cards or the Gaussian approximation, different behavior of the genetic system occurs with respect to linkage.