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"Perez, S"
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Rapid radiation of humans in South America after the last glacial maximum: A radiocarbon-based study
The early peopling of the Americas has been one of the most hotly contested topics in American anthropology and a research issue that draws archaeologists into a multidisciplinary debate. In South America, although the background data on this issue has increased exponentially in recent decades, the core questions related to the temporal and spatial patterns of the colonization process remain open. In this paper we tackle these questions in the light of the quantitative analysis of a screened radiocarbon database of more than 1600 early dates. We explore the frequency of radiocarbon dates as proxies for assessing population growth; and define a reliable and statistically well supported lower chronological bound (not to the exact date) for the earliest human arrival. Our results suggest that the earliest chronological threshold for the peopling of South America should be between 16,600 and 15,100, with a mean estimated date ~ 15,500 cal BP (post Last Glacial Maximum). Population would have grown until the end of Antarctic Cold Reversal stadial ~12,500 cal BP at the time of the main extinctions of megafauna-, when the increase rate slows, probably as a result of the changes that occurred in the trophic niche of humans.
Journal Article
Late Pleistocene South American megafaunal extinctions associated with rise of Fishtail points and human population
In the 1970s, Paul Martin proposed that big game hunters armed with fluted projectile points colonized the Americas and drove the extinction of megafauna. Around fifty years later, the central role of humans in the extinctions is still strongly debated in North American archaeology, but little considered in South America. Here we analyze the temporal dynamic and spatial distribution of South American megafauna and fluted (Fishtail) projectile points to evaluate the role of humans in Pleistocene extinctions. We observe a strong relationship between the temporal density and spatial distribution of megafaunal species stratigraphically associated with humans and Fishtail projectile points, as well as with the fluctuations in human demography. On this basis we propose that the direct effect of human predation was the main factor driving the megafaunal decline, with other secondary, but necessary, co-occurring factors for the collapse of the megafaunal community.
Human arrival in South America predated the extinction of regional megafauna by a substantial margin, which has suggested a different cause for the extinctions. However, here, the authors show that megafaunal extinctions do correspond to the spread of hunting tools and human population shifts.
Journal Article
Complex regional pain syndrome -- phenotypic characteristics and potential biomarkers
Complex regional pain syndrome (CRPS) is a pain condition that usually affects a single limb, often following an injury. The underlying pathophysiology seems to be complex and probably varies between patients. Clinical diagnosis is based on internationally agreed-upon criteria, which consider the reported symptoms, presence of signs and exclusion of alternative causes. Research into CRPS biomarkers to support patient stratification and improve diagnostic certainty is an important scientific focus, and recent progress in this area provides an opportunity for an up-to-date topical review of measurable disease-predictive, diagnostic and prognostic parameters. Clinical and biochemical attributes of CRPS that may aid diagnosis and determination of appropriate treatment are delineated. Findings that predict the development of CRPS and support the diagnosis include trauma-related factors, neurocognitive peculiarities, psychological markers, and local and systemic changes that indicate activation of the immune system. Analysis of signatures of non-coding microRNAs that could predict the treatment response represents a new line of research. Results from the past 5 years of CRPS research indicate that a single marker for CRPS will probably never be found; however, a range of biomarkers might assist in clinical diagnosis and guide prognosis and treatment.
Journal Article
Fame
Passions will be tested and young hearts will be broken. Ultimately, talent, dedication and hard work will triumph. Centers around a group of dancers, singers, musicians and actors at the New York City High School of Performing Arts, and their spirited drive to live out their dreams of stardom. In an incredibly competitive atmosphere, each student must shine amidst the tumult of school work, deep friendships, budding romance and self-discovery.
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Changes in projectile design and size of prey reveal the central role of Fishtail points in megafauna hunting in South America
Fishtail projectile points are the earliest widespread projectile type in South America, and share chronology and techno-morphology with Clovis, the oldest North American projectile type. Both were temporally associated with late Pleistocene megafaunal extinctions. Although the elusive direct evidence of human exploitation of megafauna in South America had kept Fishtails out of the extinction debate, a recent paper showed a strong relationship between the temporal density and spatial distribution of megafauna and Fishtail projectile points, and proposed that this weapon was designed and used for megafauna hunting, contributing to their extinction. If so, this technology must be distinctly different from post-FPP technologies (i.e., early Holocene projectile points), used for hunting smaller prey, in terms of distribution and functional properties. In this paper, we explore the changes in projectile point technology, as well as the body mass of potential megafaunal prey, and show that Fishtails were strongly related to the largest extinct megafaunal species.
Journal Article
Hippocampal interneuron transplants reverse aberrant dopamine system function and behavior in a rodent model of schizophrenia
Schizophrenia patients exhibit increased hippocampal activity that is correlated with positive symptoms. Although the cause of this hippocampal hyperactivity has not been demonstrated, it likely involves a decrease in GABAergic signaling. Thus, we posit that restoring GABAergic function may provide a novel therapeutic approach for the treatment of schizophrenia. It has been demonstrated that transplanted GABAergic precursor cells from the medial ganglionic eminence (MGE) can migrate and differentiate into mature interneurons. Here, we demonstrate that ventral hippocampal MGE transplants can restore hippocampal function and normalize downstream dopamine neuron activity in a rodent model of schizophrenia. Furthermore, MGE transplants also reverse the hyper-responsive locomotor response to amphetamine. Taken together, these data demonstrate that restoring interneuron function reverses neurophysiological and behavioral deficits in a rodent model of schizophrenia and moreover, demonstrate the feasibility of a neuronal transplant procedure as a potential novel therapeutic approach for the treatment of schizophrenia.
Journal Article
Perspectives on skeletal muscle stem cells
Skeletal muscle has remarkable regeneration capabilities, mainly due to its resident muscle stem cells (MuSCs). In this review, we introduce recently developed technologies and the mechanistic insights they provide to the understanding of MuSC biology, including the re-definition of quiescence and G
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states. Additionally, we present recent studies that link MuSC function with cellular heterogeneity, highlighting the complex regulation of self-renewal in regeneration, muscle disorders and aging. Finally, we discuss MuSC metabolism and its role, as well as the multifaceted regulation of MuSCs by their niche. The presented conceptual advances in the MuSC field impact on our general understanding of stem cells and their therapeutic use in regenerative medicine.
Skeletal muscle has a remarkable regenerative capacity, which can largely be attributed to resident muscle stem cells (MuSCs). Here, the authors review the molecular mechanisms regulating MuSC quiescence, activation and proliferation, how these processes are regulated by the stem cell niche, and the role of MuSCs in neuromuscular diseases.
Journal Article