Influence of imperfections on dynamic properties of oscillating rod

© 2020 Institute of Physics Publishing. All rights reserved. The paper deals with the analysis of the influence of boundary conditions on the dynamic properties of a mechanical system. The steel bar is fixed in one place so that it is inserted under the hydraulic press. The pressure force in the press changes and models the imperfect fixation of the bar. The effect of bond imperfection is evaluated based on rod vibration analysis. This problem is solved computationally, by FEM and the results are compared with experimental measurement

A novel strigolactone-miR156 module controls stomatal behaviour during drought recovery

miR156 is a conserved microRNA whose role and induction mechanisms under stress are poorly known. Strigolactones are phytohormones needed in shoots for drought acclimation. They promote stomatal closure ABA-dependently and independently; however, downstream effectors for the former have not been identified. Linkage between miR156 and strigolactones under stress has not been reported. We compared ABA accumulation and sensitivity as well as performances of wt and miR156-overexpressing (miR156-oe) tomato plants during drought. We also quantified miR156 levels in wt, strigolactone-depleted and strigolactone-treated plants, exposed to drought stress. Under irrigated conditions, miR156 overexpression and strigolactone treatment led to lower stomatal conductance and higher ABA sensitivity. Exogenous strigolactones were sufficient for miR156 accumulation in leaves, while endogenous strigolactones were required for miR156 induction by drought. The “after-effect” of drought, by which stomata do not completely re-open after rewatering, was enhanced by both strigolactones and miR156. The transcript profiles of several miR156 targets were altered in strigolactone-depleted plants. Our results show that strigolactones act as a molecular link between drought and miR156 in tomato, and identify miR156 as a mediator of ABA-dependent effect of strigolactones on the after effect of drought on stomata. Thus, we provide insights into both strigolactone and miR156 action on stomata

Temperature and Water Availability During Maturation Affect the Cytokinins and Auxins Profile of Radiata Pine Somatic Embryos

Somatic embryogenesis (SE) provides us a potent biotechnological tool to manipulate the physical and chemical conditions (water availability) along the process and to study their effect in the final success in terms of quantity of somatic embryos produced. In the last years, our research team has been focused on the study of different aspects of the SE in Pinus spp. One of the main aspects affecting SE is the composition of culture media; in this sense, phytohormones play one of the most crucial roles in this propagation system. Many studies in conifers have shown that different stages of SE and somatic embryo development are correlated with distinct endogenous phytohormone profiles under the stress conditions needed for the process (i.e., cytokinins play a regulatory role in stress signaling, which it is essential for radiata pine SE). Based on this knowledge, the aim of this study was to test the effect of different temperatures (18, 23, and 28°C) and gelling agent concentrations (8, 9, and 10 gL-1) during the maturation stage of Pinus radiata SE in maturation and germination rates. Parallel, phytohormone profile of somatic embryos developed was evaluated. In this sense, the highest gellan gum concentration led to significantly lower water availability. At this gellan gum concentration and 23°C a significantly higher number of somatic embryos was obtained and the overall success of the process increased with respect to other treatments assayed. The somatic embryos produced in these conditions showed the highest concentration of iP-type cytokinins and total ribosides. Although, the different conditions applied during maturation of somatic embryos led to different hormonal profiles, they did not affect the ex vitro survival of the resulting somatic plants, where no significant differences were observed

Vliv probiotik ve výživě telat na hmotnostní přírůstky živé hmotnosti a zdravotní stav

This paper aims to monitor the impact of Lactobacillus sporogenes (LS), Saccharomyces cerevisiae (SC), the combination thereof Lactobacillus sporogenes and Saccharomyces cerevisiae (CLS) on the health status and the live weight gain in calves compared to a control group (C). The experiment took place in the period from March 2022 to March 2023. 100 Holstein heifers in the age from 1 to 56 days were included in the experiment. The differences in live weight gain were significant when the live weight gains were compared in the first 14 days after birth between the CLS vs C group (63,36.72 ± 4.81 vs 59.55 ± 4.55, P 0.05. The impact on decrease and duration of diarrhea was not proved statistically P = 0.0634. However, a tendency to decrease the occurrence and duration thereof was proved. The impact of feed additives on the transmission of passive immunity in calves in their first week of life was not proved as statistically significant.Cílem této studie bylo sledovat vliv Lactobacillus sporogenes (LS), Saccharomyces cerevisiae (SC) a jejich kombinaci Lactobacillus sporogenes and Saccharomyces cerevisiae (CLS) na zdravotní stav a přírůstek živé hmotnosti telat oproti skupině kontrolní (C). Pokus se uskutečnil v období březen 2022 až březen 2023. Do pokusu bylo zařazeno celkem 100 holštýnských jaloviček ve stáří 1 až 56 dní. Rozdíly v přírůstku živé hmotnosti byly významné, pokud byly porovnány hmotnostní přírůstky ve 14. dech po narození mezi skupinou CLS vs C (63,36.72 ± 4.81 vs 59.55 ± 4.55, P < 0.05) a v 56 dnech po narození mezi skupinu CLS vs C, LS vs C a SC vs C (87.34 ± 4.95 kg vs 83.15 ± 5.32 kg, P < 0.01; 86.41 ± 5.34 kg vs 83.15 ± 5.32 kg, P < 0.05 a 85.92 ± 5.86 kg vs 83.15 ± 5.32 kg, P < 0.05). Rozdíly v přírůstku živé hmotnosti mezi pokusnými skupinami nebyly statisticky prokázány P > 0.05. Vliv na snížení výskytu a trvání průjmových onemocnění nebyl statisticky prokázán P = 0.0634, ovšem byla zde prokázána tendence ke snížení jejich výskytů a době trvání. Statisticky významný nebyl prokázán vliv krmných aditiv na přenos pasivní imunity u telat v prvním týdnu života

New Urea Derivatives Are Effective Anti-senescence Compounds Acting Most Likely via a Cytokinin-Independent Mechanism

Stress-induced senescence is a global agro-economic problem. Cytokinins are considered to be key plant anti-senescence hormones, but despite this practical function their use in agriculture is limited because cytokinins also inhibit root growth and development. We explored new cytokinin analogs by synthesizing a series of 1,2,3-thiadiazol-5-yl urea derivatives. The most potent compound, 1-(2-methoxy-ethyl)-3-1,2,3-thiadiazol-5-yl urea (ASES - Anti-Senescence Substance), strongly inhibited dark-induced senescence in leaves of wheat (Triticum aestivum L.) and Arabidopsis thaliana. The inhibitory effect of ASES on wheat leaf senescence was, to the best of our knowledge, the strongest of any known natural or synthetic compound. In vivo, ASES also improved the salt tolerance of young wheat plants. Interestingly, ASES did not affect root development of wheat and Arabidopsis, and molecular and classical cytokinin bioassays demonstrated that ASES exhibits very low cytokinin activity. A proteomic analysis of the ASES-treated leaves further revealed that the senescence-induced degradation of photosystem II had been very effectively blocked. Taken together, our results including data from cytokinin content analysis demonstrate that ASES delays leaf senescence by mechanism(s) different from those of cytokinins and, more effectively. No such substance has yet been described in the literature, which makes ASES an interesting tool for research of photosynthesis regulation. Its simple synthesis and high efficiency predetermine ASES to become also a potent plant stress protectant in biotechnology and agricultural industries

The Cytokinin Complex Associated With Rhodococcus fascians: Which Compounds Are Critical for Virulence?

Virulent strains of Rhodococcus fascians cause a range of disease symptoms, many of which can be mimicked by application of cytokinin. Both virulent and avirulent strains produce a complex of cytokinins, most of which can be derived from tRNA degradation. To test the three current hypotheses regarding the involvement of cytokinins as virulence determinants, we used PCR to detect specific genes, previously associated with a linear virulence plasmid, including two methyl transferase genes (mt1 and mt2) and fas4 (dimethyl transferase), of multiple strains of R. fascians. We inoculated Pisum sativum (pea) seeds with virulent and avirulent strains of R. fascians, monitored the plants over time and compared these to mock-inoculated controls. We used RT-qPCR to monitor the expression of mt1, mt2, and fas4 in inoculated tissues and LC-MS/MS to obtain a comprehensive picture of the cytokinin complement of inoculated cotyledons, roots and shoots over time. The presence and expression of mt1 and mt2 was associated with those strains of R. fascians classed as virulent, and not those classed as avirulent. Expression of mt1, mt2, and fas4 peaked at 9 days post-inoculation (dpi) in cotyledons and at 15 dpi in shoots and roots developed from seeds inoculated with virulent strain 602. Pea plants inoculated with virulent and avirulent strains of R. fascians both contained cytokinins likely to have been derived from tRNA turnover including the 2-methylthio cytokinins and cis-zeatin-derivatives. Along with the isopentenyladenine-type cytokinins, the levels of these compounds did not correlate with virulence. Only the novel 1- and 2-methylated isopentenyladenine cytokinins were uniquely associated with infection by the virulent strains and are, therefore, the likely causative factors of the disease symptoms

Non–T Cell Activation Linker (NTAL): A Transmembrane Adaptor Protein Involved in Immunoreceptor Signaling

A key molecule necessary for activation of T lymphocytes through their antigen-specific T cell receptor (TCR) is the transmembrane adaptor protein LAT (linker for activation of T cells). Upon TCR engagement, LAT becomes rapidly tyrosine phosphorylated and then serves as a scaffold organizing a multicomponent complex that is indispensable for induction of further downstream steps of the signaling cascade. Here we describe the identification and preliminary characterization of a novel transmembrane adaptor protein that is structurally and evolutionarily related to LAT and is expressed in B lymphocytes, natural killer (NK) cells, monocytes, and mast cells but not in resting T lymphocytes. This novel transmembrane adaptor protein, termed NTAL (non–T cell activation linker) is the product of a previously identified WBSCR5 gene of so far unknown function. NTAL becomes rapidly tyrosine-phosphorylated upon cross-linking of the B cell receptor (BCR) or of high-affinity Fcγ- and Fcɛ-receptors of myeloid cells and then associates with the cytoplasmic signaling molecules Grb2, Sos1, Gab1, and c-Cbl. NTAL expressed in the LAT-deficient T cell line J.CaM2.5 becomes tyrosine phosphorylated and rescues activation of Erk1/2 and minimal transient elevation of cytoplasmic calcium level upon TCR/CD3 cross-linking. Thus, NTAL appears to be a structural and possibly also functional homologue of LAT in non–T cells