Age-related cellular changes in the long-lived bivalve A. islandica

One of the biggest challenges to studying causes and effects of aging is identifying changes in cells that are related to senescence instead of simply the passing of chronological time. We investigated two populations of the longest living non-colonial metazoan, Arctica islandica, with lifespans that differed sixfolds. Of four investigated parameters (nucleic acid oxidation, protein oxidation, lipid oxidation, and protein instability), only nucleic acid oxidation increased with age and correlated with relative lifespan. Nucleic acid oxidation levels increased significantly faster and were significantly higher in the shorter-lived than the longer-lived population. In contrast, neither protein oxidation, lipid oxidation, nor protein stability changed over time. Protein resistance to unfolding stress when treated with urea was significantly lower overall in the shorter-lived population, and lipid peroxidation levels were higher in the longer-lived population. With the exception of nucleic acid oxidation, damage levels of A. islandica do not change with age, indicating excellent cellular maintenance in both populations. Since correlations between nucleic acid oxidation and age have also been shown previously in other organisms, and nucleic acid oxidation accumulation rate correlates with relative age in both investigated populations, nucleic acid oxidation may reflect intrinsic aging mechanisms

Telomere-independent ageing in the longest-lived non-colonial animal, Arctica islandica

The shortening of telomeres as a causative factor in ageing is a widely discussed hypothesis in ageing research. The study of telomere length and its regenerating enzyme telomerase in the longest-lived non-colonial animal on earth, Arctica islandica, should inform whether the maintenance of telomere length plays a role in reaching the extreme maximum lifespan (MLSP) of > 500 years in this species. Since longitudinal measurements on living animals cannot be achieved, a cross-sectional analysis of a short-lived (MLSP 40 years from the Baltic Sea) and a long-lived population (MLSP 226 years Northeast of Iceland) and in different tissues of young and old animals from the Irish Sea was performed. A high heterogeneity of telomere length was observed in investigated A. islandica over a wide age range (10–36 years for the Baltic Sea, 11–194 years for Irish Sea, 6–226 years for Iceland). Constant telomerase activity and telomere lengths were detected at any age and in different tissues; neither correlated with age or population habitat. Stable telomere maintenance might contribute to the long lifespan of A. islandica. Telomere dynamics are no explanation for the distinct MLSPs of the examined populations and thus the cause of it remains to be investigated

Initial Symbiont Contact Orchestrates Host-Organ-wide Transcriptional Changes that Prime Tissue Colonization

SummaryUpon transit to colonization sites, bacteria often experience critical priming that prepares them for subsequent, specific interactions with the host; however, the underlying mechanisms are poorly described. During initiation of the symbiosis between the bacterium Vibrio fischeri and its squid host, which can be observed directly and in real time, approximately five V. fischeri cells aggregate along the mucociliary membranes of a superficial epithelium prior to entering host tissues. Here, we show that these few early host-associated symbionts specifically induce robust changes in host gene expression that are critical to subsequent colonization steps. This exquisitely sensitive response to the host’s specific symbiotic partner includes the upregulation of a host endochitinase, whose activity hydrolyzes polymeric chitin in the mucus into chitobiose, thereby priming the symbiont and also producing a chemoattractant gradient that promotes V. fischeri migration into host tissues. Thus, the host responds transcriptionally upon initial symbiont contact, which facilitates subsequent colonization

Observation of an exotic narrow doubly charmed tetraquark

International audienceConventional, hadronic matter consists of baryons and mesons made of three quarks and a quark–antiquark pair, respectively$^{1,2}$. Here, we report the observation of a hadronic state containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a $\overline{{{{{u}}}}}$ and a $\overline{{{{{d}}}}}$ quark. This exotic state has a mass of approximately 3,875 MeV and manifests as a narrow peak in the mass spectrum of D$^{0}$D$^{0}$π$^{+}$ mesons just below the D$^{*+}$D$^{0}$ mass threshold. The near-threshold mass together with the narrow width reveals the resonance nature of the state

Study of the doubly charmed tetraquark Tcc+T_{cc}^+

An exotic narrow state in the $D^0D^0\pi^+$ mass spectrum just below the $D^{*+}D^0$ mass threshold is studied using a data set corresponding to an integrated luminosity of 9 fb$^{-1}$ acquired with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The state is consistent with the ground isoscalar $T^+_{cc}$ tetraquark with a quark content of $cc\bar{u}\bar{d}$ and spin-parity quantum numbers $\mathrm{J}^{\mathrm{P}}=1^+$. Study of the $DD$ mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell $D^{*+}$ mesons is confirmed by the $D^0\pi^+$ mass distribution. The mass of the resonance and its coupling to the $D^{*}D$ system are analysed. Resonance parameters including the pole position, scattering length, effective range and compositeness are measured to reveal important information about the nature of the $T^+_{cc}$ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed

Observation of Λb0→D+pπ−π−\Lambda_b^0\rightarrow D^+ p \pi^-\pi^- and Λb0→D∗+pπ−π−\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^- decays

International audienceThe multihadron decays ${\Lambda}_b^0$ → D+pπ−π− and ${\Lambda}_b^0$ → D$^{*}$+pπ−π− are observed in data corresponding to an integrated luminosity of 3 fb$^{−1}$, collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector. Using the decay ${\Lambda}_b^0$ → ${\Lambda}_c^{+}$π$^{+}$π$^{−}$π$^{−}$ as a normalisation channel, the ratio of branching fractions is measured to be$\frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}p{\pi}^{-}{\pi}^{-}\right)}{\mathcal{B}\left({\Lambda}_b^0\to {\Lambda}_c^0{\pi}^{+}{\pi}^{-}{\pi}^{-}\right)}\times \frac{\mathcal{B}\left({D}^{+}\to {K}^{-}{\pi}^{+}{\pi}^{+}\right)}{\mathcal{B}\left({\Lambda}_c^0\to {pK}^{-}{\pi}^{-}\right)}=\left(5.35\pm 0.21\pm 0.16\right)\%,$where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for the ${\Lambda}_b^0$ → D$^{*+}$pπ$^{−}$π$^{−}$ and ${\Lambda}_b^0$ → D$^{+}$pπ$^{−}$π$^{−}$ decays is found to be$\frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{\ast +}p{\pi}^{-}{\pi}^{-}\right)}{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}p{\pi}^{-}{\pi}^{-}\right)}\times \left(\mathcal{B}\left({D}^{\ast +}\to {D}^{+}{\pi}^0\right)+\mathcal{B}\left({D}^{\ast +}\to {D}^{+}\gamma \right)\right)=\left(61.3\pm 4.3\pm 4.0\right)\%.$[graphic not available: see fulltext

Study of Bc+ {\mathrm{B}}_{\mathrm{c}}^{+} decays to charmonia and three light hadrons

International audienceUsing proton-proton collision data, corresponding to an integrated luminosity of 9 fb$^{−1}$ collected with the LHCb detector, seven decay modes of the ${\mathrm{B}}_{\mathrm{c}}^{+}$ meson into a J/ψ or ψ(2S) meson and three charged hadrons, kaons or pions, are studied. The decays ${\mathrm{B}}_{\mathrm{c}}^{+}$ → (ψ(2S) → J/ψπ$^{+}$π$^{−}$)π$^{+}$, ${\mathrm{B}}_{\mathrm{c}}^{+}$ → ψ(2S)π$^{+}$π$^{−}$π$^{+}$, ${\mathrm{B}}_{\mathrm{c}}^{+}$ → J/ψK$^{+}$π$^{−}$π$^{+}$ and ${\mathrm{B}}_{\mathrm{c}}^{+}$ → J/ψK$^{+}$K$^{−}$K$^{+}$ are observed for the first time, and evidence for the ${\mathrm{B}}_{\mathrm{c}}^{+}$ → ψ(2S)K$^{+}$K$^{−}$π$^{+}$, decay is found, where J/ψ and ψ(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different ${\mathrm{B}}_{\mathrm{c}}^{+}$ decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.[graphic not available: see fulltext

Observation of the doubly charmed baryon decay Ξcc++→Ξc′+π+ {\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+}

International audienceThe ${\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+}$ decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb−1. The ${\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+}$ decay is reconstructed partially, where the photon from the ${\varXi}_c^{\prime +}\to {\varXi}_c^{+}\gamma$ decay is not reconstructed and the pK$^{−}$π$^{+}$ final state of the ${\varXi}_c^{+}$ baryon is employed. The ${\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+}$branching fraction relative to that of the ${\varXi}_{cc}^{++}\to {\varXi}_c^{+}{\pi}^{+}$ decay is measured to be 1.41 ± 0.17 ± 0.10, where the first uncertainty is statistical and the second systematic.[graphic not available: see fulltext