Activation of mammalian Chk1 during DNA replication arrest: a role for Chk1 in the intra-S phase checkpoint monitoring replication origin firing

Checkpoints maintain order and fidelity in the cell cycle by blocking late-occurring events when earlier events are improperly executed. Here we describe evidence for the participation of Chk1 in an intra-S phase checkpoint in mammalian cells. We show that both Chk1 and Chk2 are phosphorylated and activated in a caffeine-sensitive signaling pathway during S phase, but only in response to replication blocks, not during normal S phase progression. Replication block–induced activation of Chk1 and Chk2 occurs normally in ataxia telangiectasia (AT) cells, which are deficient in the S phase response to ionizing radiation (IR). Resumption of synthesis after removal of replication blocks correlates with the inactivation of Chk1 but not Chk2. Using a selective small molecule inhibitor, cells lacking Chk1 function show a progressive change in the global pattern of replication origin firing in the absence of any DNA replication. Thus, Chk1 is apparently necessary for an intra-S phase checkpoint, ensuring that activation of late replication origins is blocked and arrested replication fork integrity is maintained when DNA synthesis is inhibited

Lowest-lying 12−{\frac{1}{2}}^- and 32−{\frac{3}{2}}^- ΛQ\Lambda_{Q} resonances: from the strange to the bottom sectors

We present a detailed study of the lowest-lying ${\frac{1}{2}}^-$ and ${\frac{3}{2}}^-$ $\Lambda_{Q}$ resonances both in the heavy quark (bottom and charm) and the strange sectors. We have paid special attention to the interplay between the constituent quark-model and chiral baryon-meson degrees of freedom, which are coupled using a unitarized scheme consistent with leading-order heavy quark symmetries. We show that the $\Lambda_b(5912)$ [$J^P=1/2^-$], $\Lambda_b(5920)$ [$J^P=3/2^-$] and the $\Lambda_c(2625)$ [$J^P=3/2^-$], and the $\Lambda(1520)$ [$J^P=3/2^-$] admitting larger breaking corrections, are heavy-quark spin-flavor siblings. They can be seen as dressed quark-model states with $\Sigma_{Q}^{(*)}\pi$ molecular components of the order of 30\%. The ${J^P=\frac{1}{2}}^-$ $\Lambda_c(2595)$ has, however, a higher molecular probability of at least $50$\%, and even values greater than 70\% can be easily accommodated. This is because it is located almost on top of the threshold of the $\Sigma_c\pi$ pair, which largely influences its properties. Although the light degrees of freedom in this resonance would be coupled to spin-parity $1^-$ as in the $\Lambda_b(5912)$, $\Lambda_b(5920)$ and $\Lambda_c(2625)$, the $\Lambda_c(2595)$ should not be considered as a heavy-quark spin-flavor partner of the former ones. We also show that the $\Lambda(1405)$ chiral two-pole pattern does not have analogs in the $\frac{1}{2}^-$ charmed and bottomed sectors, because the $ND^{(*)}$ and $N\overline{B}{}^{(*)}$ channels do not play for heavy quarks the decisive role that the $N \overline{K}$ does in the strange sector, and the notable influence of the bare quark-model states for the charm and bottom resonances. Finally, we predict the existence of two $\Lambda_b(6070)$ and two $\Lambda_c(2765)$ heavy-quark spin and flavor sibling odd parity states.Comment: 41 pages, 13 figures, and 7 table

Genotoxicity analysis of different magnetite-based nanoparticles applied in chemical catalysis processes

info:eu-repo/semantics/publishedVersio

Single Miller Class III recession treatment in the anterior maxilla

Introduction: Miller’s Class III gingival recession represents a challenging condition with a low predictability in order to obtain successful outcomes. The purpose of this case report is to document the management of an isolated Class III gingival recession (Rec) with Coronally Advanced Flap in combination with Subepithelial Connective Tissue Graft. Presentation of the case: A 45 years-old female with a 2 mm Rec associated with interproximal attachment loss at the upper left canine requested a dental cosmetic treatment for this area. A bilaminar technique was performed in order to solve the aesthetic impairment. Results at short (1 year) and long term (10 years) are reported. Discussion: At 1-year follow up a complete root coverage with no interproximal attachment loss was observed, with an increased amount of keratinized tissue width and thickness. Optimal aesthetic outcome was accomplished with complete patient satisfaction. However, at 10-year follow-up 1mm Rec on mesio-buccal and buccal sites associated to a non-carious cervical lesion (NCCL) were noticed, associated with a bruxism pattern in combination with a relapse of traumatic brushing technique and vigorous use of interdental brushes. At this time, reinstruction to the appropriate domiciliary oral hygiene procedures and a composite restoration were performed in order to solve the clinical condition. Conclusion: At 1-year follow-up Rec associated to attachment loss and NCCL can be successfully managed by means of bilaminar technique and conservative restorations. However, a careful assessment of prognostic factors must be considered in order to achieve successful treatment outcomes in the long-term

Correlation function for the TbbT_{bb} state: Determination of the binding, scattering lengths, effective ranges and molecular probabilities

We perform a study of the $B^{*+}B^0,B^{*0}B^+$ correlation functions using an extension of the local hidden gauge approach which provides the interaction from the exchange of light vector mesons and gives rise to a bound state of these components in $I=0$ with a binding energy of about $21$~MeV. After that, we face the inverse problem of determining the low energy observables, scattering length and effective range for each channel, the possible existence of a bound state, and, if found, the couplings of such a state to each $B^{*+}B^0,B^{*0}B^+$ component as well as the molecular probabilities of each of the channels. We use the bootstrap method to determine these magnitudes and find that, with errors in the correlation function typical of present experiments, we can determine all these magnitudes with acceptable precision. In addition, the size of the source function of the experiment from where the correlation functions are measured can be also determined with a high precision.Comment: 7 pages, 3 figure