Brassinosteroid coordinates cell layer interactions in plants via cell wall and tissue mechanics

Growth coordination between cell layers is essential for development of most multicellular organisms. Coordination may be mediated by molecular signaling and/or mechanical connectivity between cells, but how genes modify mechanical interactions between layers is unknown. Here we show that genes driving brassinosteroid synthesis promote growth of internal tissue, at least in part, by reducing mechanical epidermal constraint. We identified a brassinosteroid-deficient dwarf mutant in the aquatic plant Utricularia gibba with twisted internal tissue, likely caused by mechanical constraint from a slow-growing epidermis. We tested this hypothesis by showing that a brassinosteroid mutant in Arabidopsis enhances epidermal crack formation, indicative of increased tissue stress. We propose that by remodeling cell walls, brassinosteroids reduce epidermal constraint, showing how genes can control growth coordination between layers by means of mechanics.

Localization of stomatal lineage proteins reveals contrasting planar polarity patterns in Arabidopsis cotyledons

Many plant cells exhibit polarity, revealed by asymmetric localization of specific proteins within each cell.^1,2,3,4,5,6 Polarity is typically coordinated between cells across a tissue, raising the question of how coordination is achieved. One hypothesis is that mechanical stresses provide cues.⁷ This idea gains support from experiments in which cotyledons were mechanically stretched transversely to their midline.⁸ These previously published results showed that without applied tension, the stomatal lineage cell polarity marker, BREVIS RADIX-LIKE 2 (BRXL2), exhibited no significant excess in the transverse orientation. By contrast, 7 h after stretching, BRXL2 polarity distribution exhibited transverse excess, aligned with the stretch direction. These stretching experiments involved statistical comparisons between snapshots of stretched and unstretched cotyledons, with different specimens being imaged in each case.⁸ Here, we image the same cotyledon before and after stretching and find no evidence for reorientation of polarity. Instead, statistical analysis shows that cotyledons contain a pre-existing transverse excess in BRXL2 polarity orientation that is not significantly modified by applied tension. The transverse excess reflects BRLX2 being preferentially localized toward the medial side of the cell, nearer to the cotyledon midline, creating a weak medial bias. A second polarity marker, BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL), also exhibits weak medial bias in stomatal lineages, whereas ectopic expression of BASL in non-stomatal cells exhibits strong proximal bias, as previously observed in rosette leaves. This proximal bias is also unperturbed by applied tension. Our findings therefore show that cotyledons contain two near-orthogonal coordinated biases in planar polarity: mediolateral and proximodistal.

Structural Characterisation Reveals Mechanism of IL-13-Neutralising Monoclonal Antibody Tralokinumab as Inhibition of Binding to IL-13Rα1 and IL-13Rα2

Interleukin (IL)-13 is a pleiotropic T helper type 2 cytokine frequently associated with asthma and atopic dermatitis. IL-13-mediated signalling is initiated by binding to IL-13Rα1, which then recruits IL-4Rα to form a heterodimeric receptor complex. IL-13 also binds to IL-13Rα2, considered as either a decoy or a key mediator of fibrosis. IL-13-neutralising antibodies act by preventing IL-13 binding to IL-13Rα1, IL-4Rα and/or IL-13Rα2. Tralokinumab (CAT-354) is an IL-13-neutralising human IgG4 monoclonal antibody that has shown clinical benefit in patients with asthma. To decipher how tralokinumab inhibits the effects of IL-13, we determined the structure of tralokinumab Fab in complex with human IL-13 to 2 Å resolution. The structure analysis reveals that tralokinumab prevents IL-13 from binding to both IL-13Rα1 and IL-13Rα2. This is supported by biochemical ligand-receptor interaction assay data. The tralokinumab epitope is mainly composed of residues in helices D and A of IL-13. It is mostly light chain complementarity-determining regions that are driving paratope interactions; the variable light complementarity-determining region 2 plays a key role by providing residue contacts for a network of hydrogen bonds and a salt bridge in the core of binding. The key residues within the paratope contributing to binding were identified as Asp50, Asp51, Ser30 and Lys31. This study demonstrates that tralokinumab prevents the IL-13 pharmacodynamic effect by binding to IL-13 helices A and D, thus preventing IL-13 from interacting with IL-13Rα1 and IL-13Rα2.

Suicide and self-poisoning in three countries--a study from Ireland, England and Wales, and Denmark

Because it has been suggested that both the frequency of deliberate self-poisoning and the characteristics of those who self-poison differ between Ireland, and England and Wales on the one hand and Denmark on the other we have examined self-poisoning rates and suicide rates in these three countries. Higher self-poisoning rates were found for England and Wales than for the other two countries below age 35. After this age self-poisoning rates decline in both England and Ireland but female rates continue to rise in Denmark up to age 45. Danish suicide rates are conspicuously higher than those of both England and Wales, and Ireland. Because combined death rates for suicide, undetermined and accidental deaths diminish but do not remove the differences between countries it is suggested that the Danish suicide death rate reflects a genuinely higher rate of suicide in that country.

Cross allergenicity between penicillins and cephalosporins

Twenty patients excluded from pre-marketing trials of cephalosporin antibiotics as chemoprophylaxis for open heart surgery were enrolled in an evaluation of skin-test reactivity. All gave a history of type I hypersensitivity to penicillins. None knew of adverse reactions to cephalosporins. Eighteen were negative to testing with saline, cefazolin, ceftriaxone, penicillin G and benzyl-penicilloyl. Two patients with positive skin tests safely received vancomycin chemoprophylaxis. We conclude that most patients who give a positive allergic history but have negative skin tests can safely receive cephalosporin chemoprophylaxis.

Single-dose antimicrobial prophylaxis in open heart surgery

A single one-gram pre-operative dose of ceftriaxone was compared with seven one-gram doses of cefazolin administered peri-operatively with the aim of preventing infections associated with coronary artery bypass graft surgery. Ninety-four evaluable cases were analyzed; 49 patients received ceftriaxone and 45 received cefazolin. There was no significant difference in the number of infectious complications between the two groups. Ceftriaxone had a terminal half-life of approximately 15.7 hours. There was no toxicity associated with either antibiotic. Because of the reduced number of doses, single-dose prophylaxis may result in considerable savings. Single-dose prophylaxis with ceftriaxone was found to be an effective modality for prevention of infection in open heart surgery.

Suicide and self-poisoning in Great Britain and Ireland

Reported national rates of suicide remain fairly stable from year to year and considerable differences persist between countries. Reported rates of suicide also differ from actual rates according to the social influences and the legal procedure both in attributing suicide and also in how the death is recorded and coded. This paper compares the rates of suicide and non-fatal self-poisoning in Scotland, England and Wales, and Ireland, and also examines suicide rates in people born in Ireland but now resident in England and Wales. The rise in overdose admissions to hospital which is continuing in relative degrees in all communities of Great Britain and Ireland, except Northern Ireland, does not seem to be correlated with trends in fatal suicide behaviour. Further studies on all aspects of the subject are needed to clarify the social determinants involved and to identify ways in which further increases can be contained.

Why do people use paracetamol for suicide?

A questionnaire to assess motives for choosing paracetamol as a suicidal agent was completed by 107 patients admitted after an overdose of the drug. None of the 48 patients interviewed would have chosen paracetamol had they known that there would be an interval of two to three days before the onset of serious symptoms. Only five of the patients had obtained the drug on prescription, but the remainder had obtained it easily from a retail pharmacy. There was no apparent reason for the preference for paracetamol. It would be difficult to restrict the availability of paracetamol, and educating the public about the effects of an overdose would be more appropriate.