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Preimplantation embryo development sets the stage for pluripotency
Regenerative medicine has the potential to revolutionize health care by offering the promise of replacement cells, tissues, and organs to combat injury, disease, and aging. In an ideal setting, stem cell therapies would begin with a pluripotent cell that by definition is able to give rise to any cell formed in the embryo. Additionally this would most likely require that the stem cells could self-renew or were able to divide and give rise to either more pluripotent stem cells or progressively more differentiated cells under the control of extrinsic cues. Stem cells are biological cells found in multicellular organisms, that can mitotically divide and differentiate into specialized cell types and can self-renew to produce more stem cells. There are two broad types of stem cells: embryonic stem cells and adult stem cells. Embryonic stem cells originate from the inner cell mass of the preimplantation embryo and are considered pluripotent whereas in situ adult stem cells are considered multipotent. Embryonic stem cells (ESCs) possess characteristics that make them a potentially outstanding starting material for use in regenerative medicine. They are unique among cultured cells because they have an apparently limitless capacity to self-renew in vitro, as well as being pluripotent. Because of these extraordinary properties, ESCs have been an intense focus of research for more than 30 years.
Most previous attempts to determine the psychological cost of military deployment have been limited by reliance on convenience samples, lack of pre-deployment data or confidentiality and cross-sectional designs.
This study addressed these limitations using a population-based, prospective cohort of US military personnel deployed in support of the operations in Iraq and Afghanistan.
The sample consisted of US military service members in all branches including active duty, reserve and national guard who deployed once (n = 3393) or multiple times (n = 4394). Self-reported symptoms of post-traumatic stress were obtained prior to deployment and at two follow-ups spaced 3 years apart. Data were examined for longitudinal trajectories using latent growth mixture modelling.
Each analysis revealed remarkably similar post-traumatic stress trajectories across time. The most common pattern was low–stable post-traumatic stress or resilience (83.1% single deployers, 84.9% multiple deployers), moderate–improving (8.0%, 8.5%), then worsening–chronic posttraumatic stress (6.7%, 4.5%), high–stable (2.2% single deployers only) and high–improving (2.2% multiple deployers only). Covariates associated with each trajectory were identified.
The final models exhibited similar types of trajectories for single and multiple deployers; most notably, the stable trajectory of low post-traumatic stress pre- to post-deployment, or resilience, was exceptionally high. Several factors predicting trajectories were identified, which we hope will assist in future research aimed at decreasing the risk of post-traumatic stress disorder among deployers.
As archaeologists, we seek to understand variation and change in past human societies. This goal necessitates a comparative approach, and comparisons justify the broad cross-cultural and diachronic scope of our work. Without comparisons we sink into the culture-bound theorizing against which anthropology and archaeology have long sought to broaden social science research. By undertaking comparisons that incorporate long-term social variability, archaeologists not only improve our understanding of the past, but also open the door to meaningful transdisciplinary research. Archaeologists have unique and comprehensive data sets whose analysis can contribute to dialogues surrounding contemporary issues and the myriad challenges of our era.
In the past two decades, the pendulum seems to have swung away from comparative research in archaeology. Many archaeologists focus on detailed contextual descriptions of individual cases, and only a few have dedicated themselves to explicit comparative work. Yet in that same time span, fieldwork has expanded tremendously throughout the world, leading to an explosion of well-documented diachronic data on sites and regions. We now have substantial detail on the variation inherent in phenomena such as cultural assemblages, settlement patterns, and economic activity. New methods, from dating techniques to digital data processing, promote comparative analysis and greatly advance our understanding of human societies and change. The time is ripe for a renewed commitment to comparative research in archaeology.
Gelatin has been widely used to develop tissue engineering scaffolds because it has many attractive properties. Dendrimer provides a versatile, compositionally and structurally controlled architecture to construct nanomedicine. This study was aimed at developing a novel electrospun dendrimer-gelatin nanofiber scaffold to best mimic natural extracellular matrix (ECM) to promote tissue formation and serve as a reservoir for controlled drug delivery. Starburst™ polyamidoamine (PAMAM) dendrimer G3.5 was covalently bonded to the gelatin backbone and electrospun into nanofibers. Doxycycline (DC), which is an effective antibiotic that has the ability to inhibit matrix metalloproteinase, was encapsulated into the nanofiber scaffold. The electrospun DC-gelatin scaffold provides a bacterial free environment for cell growth and tissue regeneration. The resulting dendrimer-gelatin nanofiber scaffold achieved a unique structural configuration where covalently bound three-dimensional dendritic nanospheres were evenly distributed along the elongated dimension of the nanofiber, and both dendrimer and gelatin had numerous functional groups suitable for accommodating multiple functional entities and high payload of drugs. The development of this new scaffold with the capability of delivering multiple functional entities was an important step towards the use of bioactive nanofibers to facilitate tissue regeneration and controlled drug release.