Mitochondrial alterations and apoptosis in smooth muscle from aged rats

We studied changes in mitochondrial morphology and function in the smooth muscle of rat colon. Under confocal microscopy, tissues loaded with potentiometric dye displayed rapid and spontaneous depolarization. Cyclosporin A (CsA), inhibitor of the permeability transition pore (PTP), caused an increase in mitochondrial membrane potential (ΔΨ_m) in tissues from adult young animals. In aged rats these changes were not observed. This suggests that physiological activation of PTP in aged rats is reduced. Electron microscopy showed alterations of the mitochondrial ultrastructure in tissues from aged rats involving a decreased definition of the cristae and fragmentation of the mitochondrial membranes. We also detected an increase in apoptotic cells in the smooth muscle from aged animals. Our results show that the aging process changes PTP activity, the ability to maintain ΔΨ_m and mitochondrial morphology. It is suggested that these can be associated with mitochondrial damage and cell death.     

Expérience de biologie délocalisée,télémaintenance et CQ interlaboratoire...

Dans le cadre de la gestion des analyses urgentes de biologie, le site d’Argenteuil a mis en place une organisation originale (Filière “urgence” mise en place depuis avril 1998) assurant en particulier rapidité et sécurité dans la production des résultats. Nous avons recueilli le témoignage des acteurs principaux à l’origine de cette mise en place.     

Purification of a cysteine proteinase from Carica candamarcensis L. and cloning of a genomic putative fragment coding for this enzyme.

We describe the purification of a cysteine proteinase from latex of Carica candamarcensis, hereby designated CC23. The enzyme has been purified by ion-exchange chromatography and behaves electrophoretically as a monomer of M(r) 23,000 and optimal pH of 8.0. It displays a basic isoelectric point, has one cysteine residue in the active site by titration with E-64, confirmed by DNA sequencing, and responds to proteinase inhibitors as a classic cysteine proteinase. The K(m) and k(cat)/K(m) for CC23 using BAPNA were respectively 14.7 +/- 1.8 x 10(-4) M and 1.3 x 10(3) M(-1) s(-1). Therefore, the catalytic efficiency of CC23 is sixfold higher than that of CC-I, another proteinase from the same plant. DNA primers were designed to amplify by PCR a genomic sequence related to this enzyme. An 895-bp DNA fragment was cloned and sequenced. It shows strong homology with chymopapain isoform IV from C. papaya. The translated sequence is similar to that of chymopapain isoform II (73%) and CC-III (77%) from C. candamarcensis.     

Mutations in the essential spindle checkpoint gene bub1 cause chromosome missegregation and fail to block apoptosis in Drosophila.

We have characterized the Drosophila mitotic checkpoint control protein Bub1 and obtained mutations in the bub1 gene. Drosophila Bub1 localizes strongly to the centromere/kinetochore of mitotic and meiotic chromosomes that have not yet reached the metaphase plate. Animals homozygous for P-element-induced, near-null mutations of bub1 die during late larval/pupal stages due to severe mitotic abnormalities indicative of a bypass of checkpoint function. These abnormalities include accelerated exit from metaphase and chromosome missegregation and fragmentation. Chromosome fragmentation possibly leads to the significantly elevated levels of apoptosis seen in mutants.We have also investigated the relationship between Bub1 and other kinetochore components. We show that Bub1 kinase activity is not required for phosphorylation of 3F3/2 epitopes at prophase/prometaphase, but is needed for 3F3/2 dephosphorylation at metaphase. Neither 3F3/2 dephosphorylation nor loss of Bub1 from the kinetochore is a prerequisite for anaphase entry. Bub1's localization to the kinetochore does not depend on the products of the genes zw10, rod, polo, or fizzy, indicating that the kinetochore is constructed from several independent subassemblies.     

Somatic embryogenesis and plant regeneration in myrtle (Myrtaceae)

Somatic embryos of myrtle (Myrtus communis L.) were induced from mature zygotic embryos cultured in MS medium supplemented with several concentrations of 2,4-D (2.26 μM – 18.98 μM) or Picloram (2.07 μM – 16.5 μM) combined with 0.087 M or 0.23 M sucrose. For all the concentrations of 2,4-D or Picloram tested, 0.087 M sucrose proved to be more effective than 0.23 M. The best frequencies of induction were obtained in a medium containing 2.26 μM 2,4-D in which 97.3% of the explants produced somatic embryos. Although most embryos were produced from the adaxial side of the cotyledons, some of them differentiated from the hypocotyl. Secondary somatic embryos were often seen arising from the periphery of the former somatic embryos. Somatic embryo development was not synchronous but practically all the embryos germinated well after being transferred to media containing GA₃ (0.29, 0.58 and 1.44 μM) alone. When benzyladenine was combined with gibberellic acid, germinating somatic embryos produced adventitious shoot buds which contributed to an increase in plantlet regeneration. Histological observations suggested that somatic embryos arise from the upper surface of the cotyledons probably from peripheral cells. Polyphenol-rich cells were usually seen in association with meristematic-like cells from which somatic embryos originate or with earlier steps of somatic embryo differentiation. Regenerated plants were phenotypically normal, showing a diploid (2n = 22) set of chromosomes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Assessing the best time interval between doses in a two-dose vaccination regimen to reduce the number of deaths in an ongoing epidemic of SARS-CoV-2

The SARS-CoV-2 pandemic is a major concern all over the world and, as vaccines became available at the end of 2020, optimal vaccination strategies were subjected to intense investigation. Considering their critical role in reducing disease burden, the increasing demand outpacing production, and that most currently approved vaccines follow a two-dose regimen, the cost-effectiveness of delaying the second dose to increment the coverage of the population receiving the first dose is often debated. Finding the best solution is complex due to the trade-off between vaccinating more people with lower level of protection and guaranteeing higher protection to a fewer number of individuals. Here we present a novel extended age-structured SEIR mathematical model that includes a two-dose vaccination schedule with a between-doses delay modelled through delay differential equations and linear optimization of vaccination rates. By maintaining the minimum stock of vaccines under a given production rate, we evaluate the dose interval that minimizes the number of deaths. We found that the best strategy depends on an interplay between the vaccine production rate and the relative efficacy of the first dose. In the scenario of low first-dose efficacy, it is always better to vaccinate the second dose as soon as possible, while for high first-dose efficacy, the best strategy of time window depends on the production rate and also on second-dose efficacy provided by each type of vaccine. We also found that the rate of spread of the infection does not affect significantly the thresholds of the best window, but is an important factor in the absolute number of total deaths. These conclusions point to the need to carefully take into account both vaccine characteristics and roll-out speed to optimize the outcome of vaccination strategies.     

Trust your guts? The effect of gut section on diet composition and impact of Mus musculus on islands using metabarcoding

1. DNA metabarcoding is widely used to characterize the diet of species, and it becomes very relevant for biodiversity conservation, allowing the understanding of trophic chains and the impact of invasive species. The need for cost‐effective biodiversity monitoring methods fostered advances in this technique. One question that arises is which sample type provides a better diet representation.
2. Therefore, with this study, we intended to evaluate if there were differences in diet estimates according to the section of the gastrointestinal tract analysed and which section(s) provided the best diet representation. Additionally, we intended to infer the ecological/economic impacts of an invader as a model of the potential effects in an originally mammal‐free ecosystem.
3. We examined the gut contents of the house mouse Mus musculus introduced to Cabo Verde, considering three sections: stomach, small intestine, and large intestine. We applied a DNA‐metabarcoding approach using two genetic markers, one specific for plants and another for invertebrates.
4. We showed that this invader consumed 131 taxa (73 plants and 58 invertebrates). We obtained significant differences in the composition of two of the three sections, with a higher incidence of invertebrates in the stomach and plants in the intestines. This may be due to stomach inhibitors acting on plants and/or to faster absorption of soft‐body invertebrates compared to the plant fibers in the intestines. We verified that the impact of this invader in the ecosystem is predominantly negative, as at least 50% of the ingested items were native, endemic, or economically important taxa, and only 19% of the diet items were exotics.
5. Overall, results showed the need to analyse only two gastrointestinal tract sections to obtain robust diet data, increasing the cost‐effectiveness of the method. Furthermore, by uncovering the native taxa most frequently preyed on by mice, this DNA‐metabarcoding approach allowed us to evaluate efficiently which are at the highest risk.