Search

The Rhodes Gyre is a cyclonic persistent feature of the general circulation of the Levantine Basin in the eastern Mediterranean Sea. Although it is located in the most oligotrophic basin of the Mediterranean Sea, it is a relatively high primary production area due to strong winter nutrient supply associated with the formation of Levantine Intermediate Water. In this study, a 3D coupled hydrodynamic–biogeochemical model (SYMPHONIE/Eco3M-S) was used to characterize the seasonal and interannual variability of the Rhodes Gyre's ecosystem and to estimate an annual organic carbon budget over the 2013–2020 period. Comparisons of model outputs with satellite data and compiled in situ data from cruises and Biogeochemical-Argo floats revealed the ability of the model to reconstruct the main seasonal and spatial biogeochemical dynamics of the Levantine Basin. The model results indicated that during the winter mixing period, phytoplankton first progressively grow sustained by nutrient supply. Then, short episodes of convection driven by heat loss and wind events, favoring nutrient injections, organic carbon export, and inducing light limitation on primary production, alternate with short episodes of phytoplankton growth. The estimate of the annual organic carbon budget indicated that the Rhodes Gyre is an autotrophic area, with a positive net community production in the upper layer (0–150 m) amounting to 31.2 ± 6.9 gCm-2yr-1. Net community production in the upper layer is almost balanced over the 7-year period by physical transfers, (1) via downward export (16.8 ± 6.2 gCm-2yr-1) and (2) through lateral transport towards the surrounding regions (14.1 ± 2.1 gCm-2yr-1). The intermediate layer (150–400 m) also appears to be a source of organic carbon for the surrounding Levantine Sea (7.5 ± 2.8 gCm-2yr-1) mostly through the subduction of Levantine Intermediate Water following winter mixing. The Rhodes Gyre shows high interannual variability with enhanced primary production, net community production, and exports during years marked by intense heat losses and deep mixed layers. However, annual primary production appears to be only partially driven by winter vertical mixing. Based on our results, we can speculate that future increase of temperature and stratification could strongly impact the carbon fluxes in this region.

Aging is marked by a decline in tissue regeneration, posing significant challenges to an increasingly older population. Here, we investigate age-related impairments in calvarial bone healing and introduce a novel two-part rejuvenation strategy to restore youthful repair. We demonstrate that aging negatively impacts the calvarial bone structure and its osteogenic tissues, diminishing osteoprogenitor number and function and severely impairing bone formation. Notably, increasing osteogenic cell numbers locally fails to rescue repair in aged mice, identifying the presence of intrinsic cellular deficits. Our strategy combines Wnt-mediated osteoprogenitor expansion with intermittent fasting, which leads to a striking restoration of youthful levels of bone healing. We find that intermittent fasting improves osteoprogenitor function, benefits that can be recapitulated by modulating NAD+-dependent pathways or the gut microbiota, underscoring the multifaceted nature of this intervention. Mechanistically, we identify mitochondrial dysfunction as a key component in age-related decline in osteoprogenitor function and show that both cyclical nutrient deprivation and Nicotinamide mononucleotide rejuvenate mitochondrial health, enhancing osteogenesis. These findings offer a promising therapeutic avenue for restoring youthful bone repair in aged individuals, with potential implications for rejuvenating other tissues.

Summary: These protocols investigate the interaction of cytonemes with localized Wnt. Cell-niche signaling between naive or primed mouse embryonic stem cells (ESCs) and either Wnt-secreting trophoblast stem cells (TSCs) or Wnt signals tethered to microbeads can be scrutinized in vitro. This approach analyzes cytoneme reactivity during Wnt-interaction initiation, Ca2+ transients at Wnt-contacting cytonemes, and subsequent pairing between ESCs and Wnt-sources. This pairing interaction is crucial to synthetic embryogenesis; hence this protocol is effective for in vitro studies of developmental biology.For complete details on the use and execution of this protocol, please refer to Junyent et al. (2020, 2021a, 2021b).

Summary: Asymmetric histone inheritance can regulate cell-fate determination in Drosophila male germline stem cells. However, it remains elusive how this mechanism may be used in mammalian system. Recently, we show mouse embryonic stem cells (mESCs) with Wnt3a beads display non-overlapping H3/H4 patterns. Here, we present a detailed protocol for tracking histone inheritance in asymmetrically dividing mESCs at single-cell resolution. This protocol will establish a new system to study histone inheritance in cultured mammalian cells and could be applied to other parallel systems.For complete details on the use and execution of this protocol, please refer to Tran et al. (2012), Habib et al. (2013), Lowndes et al. (2017), and Ma et al. (2020).

A salivary gland anlage tumour (SGAT) is a very rare type of benign tumour that usually presents in early infancy with respiratory distress which is exacerbated upon feeding. We report a full-term male neonate who was referred to the Al Nahdha Hospital, Muscat, Oman, in 2015 with severe neonatal respiratory distress due to a nasopharyngeal obstruction immediately after birth. Computed tomography and magnetic resonance imaging revealed a well-circumscribed mass in the nasopharynx, without intracranial extension. Histopathological analysis of the lesion confirmed a diagnosis of SGAT. Following excision of the tumour, the postoperative period was uneventful. No recurrence was observed over the next two years. This case report highlights the importance of the early recognition of this extremely rare and potentially life-threatening, yet easily curable, condition. Keywords: Nasopharyngeal Neoplasms; Salivary Gland Neoplasms; Neonatal Respiratory Distress Syndrome; Case Report; Oman.

Cell signaling is essential for cell fate determination and tissue patterning. As signaling ligands are presented to the receiving cell, they are recruited and recognized by the cell membrane so as to elicit a biological response and to pattern multicellular tissues. Cells can accumulate and transport these ligands, which results in an emergent organization of the ligands’ spatial distribution. To study this organization, we make use of a simplified experimental setup, in which single mouse embryonic stem cells (mESCs) can interact with immobilized ligands. We introduce a two-species age-dependent correlation function that allows the description and quantification of the spatiotemporal dynamics of single cell-ligand interactions. Through the analysis of mESC data and numerical simulations, we show that cells act as effective force-field generators, perturbing and organizing their environment. This organization, captured in the form of an aging effective potential, is an emergent property of the population of single cells interacting with randomly distributed localized ligands.