Algal Remodeling in a Ubiquitous Planktonic Photosymbiosis

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The NAD-Booster Nicotinamide Riboside Potently Stimulates Hematopoiesis through Increased Mitochondrial Clearance

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Characterization and expression of a maternal axolotl cyclin B1 during oogenesis and early development

The M phase promoting factor (MPF) is a dimer composed of a catalytic Cdk1 subunit and a Cyclin B regulatory subunit. We have characterized a cDNA containing the entire coding sequence of an axolotl Cyclin B1 protein that is able to promote MPF activity when added to a fraction from prophase I oocytes that contains monomeric Cdk1. The axolotl cyclin B1 gene is expressed as a maternal mRNA in oocytes and early embryos. Its poly(A) tail length increases in metaphase II oocytes and then decreases regularly during the first embryonic cell cycles. Endogenous Cyclin B1 protein is first expressed during oocyte meiotic maturation. Its level oscillates after fertilization and is coordinated to the phosphorylation level of tyrosine 15 residue of Cdk1 (pTyr15), with both maxima preceding each cell division. As expected, when translated into microinjected oocytes, axolotl Cyclin B1 induces the resumption of meiosis. In electrically activated unfertilized eggs (UFE), Cyclin B1 and pTyr15 cyclic accumulations are observed with kinetics different from those of the early embryonic cycles. The axolotl embryo and UFE provide interesting in vivo comparative models for studying events controlling Cyclin B1 regulation during development.     

Delayed inflammation decrease is associated with mortality in Tocilizumab-treated critically ill SARS-CoV-2 patients: A retrospective matched-cohort analysis

Little is known about the immuno-inflammatory response to Tocilizumab and its association with outcome in critically-ill SARS-CoV2 pneumonia. In this multicenter retrospective cohort of SARS-CoV-2 patients admitted to three intensive care units between March and April 2020, we matched on gender and SAPS II 21 Tocilizumab-treated patients to 42 non-treated patients. Need for mechanical ventilation was 76% versus 79%. IL-6, C-reactive protein, and fibrinogen had been collected within the first days of admission (T1), 3 d (T2) and 7 d (T3) later. Tocilizumab-treated patients had persistently higher IL-6 plasma levels and persistently lower C-Reactive protein and fibrinogen levels. Among Tocilizumab-treated patients, baseline levels of inflammatory biomarkers were not different according to outcome. Conversely, C-reactive protein and fibrinogen decrease was delayed in non-survivors. C-Reactive protein decreased at T1 in survivors (45 [30–98] vs 170 [69–204] mg/l, P < 0.001) but only at T2 in non-survivors (37 [13–74] vs 277 [235–288], P = 0.03). Fibrinogen decreased at T2 in survivors (4.11 [3.58–4.69] vs 614 [5.61–7.85] g/l, P = 0.005) but not in non-survivors (4.79 [4.12–7.58] vs 7.24 [6.22–9.24] g/l, P = 0.125). Tocilizumab treatment was thus associated with a persistent both increase in plasma IL-6, and decrease in C-reactive protein and fibrinogen. Among Tocilizumab-treated patients, the decrease in inflammatory biomarkers was delayed in non-survivors.     

Role of threonines in the Arabidopsis thaliana somatic embryogenesis receptor kinase 1 activation loop in phosphorylation

The Arabidopsis thaliana somatic embryogenesis receptor kinase 1 (AtSERK1) gene encodes a receptor-like protein kinase that is transiently expressed during embryogenesis. To determine the intrinsic biochemical properties of the AtSERK1 protein, we have expressed the intracellular catalytic domain as a glutathione S-transferase fusion protein in Escherichia coli. The AtSERK1-glutathione S-transferase fusion protein mainly autophosphorylates on threonine residues (K(m) for ATP, 4 x 10(-6) m), and the reaction is Mg(2+) dependent and inhibited by Mn(2+). A K330E substitution in the kinase domain of AtSERK1 abolishes all kinase activity. The active AtSERK1(kin) can phosphorylate inactive AtSERK1(K330E) protein, suggesting an intermolecular mechanism of autophosphorylation. The AtSERK1 kinase protein was modeled using the insulin receptor kinase as a template. On the basis of this model, threonine residues in the AtSERK1 activation loop of catalytic subdomain VIII are potential targets for phosphorylation. AtSERK1 phosphorylation on myelin basic protein and casein showed tyrosine, serine, and threonine as targets, demonstrating that AtSERK1 is a dual specificity kinase. Replacing Thr-468 with either alanine or glutamic acid not only obliterated the ability of the AtSERK1 protein to be phosphorylated but also inhibited phosphorylation on myelin basic protein and casein, suggesting that Thr-468 is essential for AtSERK-mediated signaling.     

Differential substrate behaviour of phenol and aniline derivatives during conversion by horseradish peroxidase

For the first time saturating overall k(cat) values for horseradish peroxidase (HRP) catalysed conversion of phenols and anilines are described. These k(cat) values correlate quantitatively with calculated ionisation potentials of the substrates. The correlations for the phenols are shifted to higher k(cat) values at similar ionisation potentials as compared to those for anilines. (1)H-NMR T(1) relaxation studies, using 3-methylphenol and 3-methylaniline as the model substrates, revealed smaller average distances of the phenol than of the aniline protons to the paramagnetic Fe(3+) centre in HRP. This observation, together with a possibly higher extent of deprotonation of the phenols than of the anilines upon binding to the active site of HRP, may contribute to the relatively higher HRP catalysed conversion rates of phenols than of anilines.     

TEAC antioxidant activity of 4-hydroxybenzoates

The influence of pH, intrinsic electron donating capacity, and intrinsic hydrogen atom donating capacity on the antioxidant potential of series of hydroxy and fluorine substituted 4-hydroxybenzoates was investigated experimentally and also on the basis of computer calculations. The pH-dependent behavior of the compounds in the TEAC assay revealed different antioxidant behavior of the nondissociated monoanionic form and the deprotonated dianionic form of the 4-hydroxybenzoates. Upon deprotonation the radical scavenging ability of the 4-hydroxybenzoates increases significantly. For mechanistic comparison a series of fluorobenzoates was synthesized and included in the studies. The fluorine substituents were shown to affect the proton and electron donating abilities of 4-hydroxybenzoate in the same way as hydroxyl substituents. In contrast, the fluorine substituents influenced the TEAC value and the hydrogen atom donating capacity of 4-hydroxybenzoate in a way different from the hydroxyl moieties. Comparison of these experimental data to computer-calculated characteristics indicates that the antioxidant behavior of the monoanionic forms of the 4-hydroxybenzoates is not determined by the tendency of the molecule to donate an electron, but by its ability to donate a hydrogen atom. Altogether, the results explain qualitatively and quantitatively how the number and position of OH moieties affect the antioxidant behavior of 4-hydroxybenzoates.     

IL-6, RANKL, TNF-alpha/IL-1: interrelations in bone resorption pathophysiology

All osteogenic cells (osteoclasts, osteoblasts) contribute individually to bone remodeling. Their cellular interactions control their cellular activities and the bone remodeling intensity. These interactions can be established either through a cell-cell contact, involving molecules of the integrin family, or by the release of many polypeptidic factors and/or their soluble receptor chains. These factors can act directly on osteogenic cells and their precursors to control differentiation, formation and functions (matrix formation, mineralization, resorption...). Here, we present the involvement of three groups of cytokines which seem to be of particular importance in bone physiology: interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) (TNF-alpha)/IL-1, and the more recently known triad osteoprotegerin (OPG)/receptor activator of NF-kappaB (RANK)/RANK ligand (RANKL). The interactions between these three groups are presented within the framework of bone resorption pathophysiology such as tumor associated osteolysis. The central role of the OPG/RANK/RANKL triad is pointed out.     

Nifedipine protects against overproduction of superoxide anion by monocytes from patients with systemic sclerosis

We have reported previously that dihydropyridine-type calcium-channel antagonists (DTCCA) such as nifedipine decrease plasma markers of oxidative stress damage in systemic sclerosis (SSc). To clarify the cellular basis of these beneficial effects, we investigated the effects in vivo and in vitro of nifedipine on superoxide anion (O₂ ^•-) production by peripheral blood monocytes. We compared 10 healthy controls with 12 patients with SSc, first after interruption of treatment with DTCCA and second after 2 weeks of treatment with nifedipine (60 mg/day). O₂ ^•- production by monocytes stimulated with phorbol myristate acetate (PMA) was quantified by the cytochrome c reduction method. We also investigated the effects in vitro of DTCCA on O₂ ^•- production and protein phosphorylation in healthy monocytes and on protein kinase C (PKC) activity using recombinant PKC. After DTCCA had been washed out, monocytes from patients with SSc produced more O₂ ^•- than those from controls. Nifedipine treatment considerably decreased O₂ ^•- production by PMA-stimulated monocytes. Treatment of healthy monocytes with nifedipine in vitro inhibited PMA-induced O₂ ^•- production and protein phosphorylation in a dose-dependent manner. Finally, nifedipine strongly inhibited the activity of recombinant PKC in vitro. Thus, the oxidative stress damage observed in SSc is consistent with O₂ ^•- overproduction by primed monocytes. This was decreased by nifedipine treatment both in vivo and in vitro. This beneficial property of nifedipine seems to be mediated by its cellular action and by the inhibition of PKC activity. This supports the hypothesis that this drug could be useful for the treatment of diseases associated with oxidative stress.