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Analysis of the volumetric relationship among human ocular, orbital and fronto-occipital cortical morphology. - Journal of anatomy
Recent research on the visual system has focused on investigating the relationship among eye (ocular), orbital, and visual cortical anatomy in humans. This issue is relevant in evolutionary and medical fields. In terms of evolution, only in modern humans and Neandertals are the orbits positioned beneath the frontal lobes, with consequent structural constraints. In terms of medicine, such constraints can be associated with minor deformation of the eye, vision defects, and patterns of integration among these features, and in association with the frontal lobes, are important to consider in reconstructive surgery. Further study is therefore necessary to establish how these variables are related, and to what extent ocular size is associated with orbital and cerebral cortical volumes. Relationships among these anatomical components were investigated using magnetic resonance images from a large sample of 83 individuals, which also included each subject's body height, age, sex, and uncorrected visual acuity score. Occipital and frontal gyri volumes were calculated using two different cortical parcellation tools in order to provide a better understanding of how the eye and orbit vary in relation to visual cortical gyri, and frontal cortical gyri which are not directly related to visual processing. Results indicated that ocular and orbital volumes were weakly correlated, and that eye volume explains only a small proportion of the variance in orbital volume. Ocular and orbital volumes were also found to be equally and, in most cases, more highly correlated with five frontal lobe gyri than with occipital lobe gyri associated with V1, V2, and V3 of the visual cortex. Additionally, after accounting for age and sex variation, the relationship between ocular and total visual cortical volume was no longer statistically significant, but remained significantly related to total frontal lobe volume. The relationship between orbital and visual cortical volumes remained significant for a number of occipital lobe gyri even after accounting for these cofactors, but was again found to be more highly correlated with the frontal cortex than with the occipital cortex. These results indicate that eye volume explains only a small amount of variation in orbital and visual cortical volume, and that the eye and orbit are generally more structurally associated with the frontal lobes than they are functionally associated with the visual cortex of the occipital lobes. Results also demonstrate that these components of the visual system are highly complex and influenced by a multitude of factors in humans.Â© 2015 Anatomical Society.
Functional craniology and brain evolution: from paleontology to biomedicine. - Frontiers in neuroanatomy
Anatomical systems are organized through a network of structural and functional relationships among their elements. This network of relationships is the result of evolution, it represents the actual target of selection, and it generates the set of rules orienting and constraining the morphogenetic processes. Understanding the relationship among cranial and cerebral components is necessary to investigate the factors that have influenced and characterized our neuroanatomy, and possible drawbacks associated with the evolution of large brains. The study of the spatial relationships between skull and brain in the human genus has direct relevance in cranial surgery. Geometrical modeling can provide functional perspectives in evolution and brain physiology, like in simulations to investigate metabolic heat production and dissipation in the endocranial form. Analysis of the evolutionary constraints between facial and neural blocks can provide new information on visual impairment. The study of brain form variation in fossil humans can supply a different perspective for interpreting the processes behind neurodegeneration and Alzheimer's disease. Following these examples, it is apparent that paleontology and biomedicine can exchange relevant information and contribute at the same time to the development of robust evolutionary hypotheses on brain evolution, while offering more comprehensive biological perspectives with regard to the interpretation of pathological processes.
Reduced nitrogen losses after conversion of row crop agriculture to perennial biofuel crops. - Journal of environmental quality
Current biofuel feedstock crops such as corn lead to large environmental losses of N through nitrate leaching and NO emissions; second-generation cellulosic crops have the potential to reduce these N losses. We measured N losses and cycling in establishing miscanthus (), switchgrass ( L. fertilized with 56 kg N ha yr), and mixed prairie, along with a corn ( L.)-corn-soybean [ (L.) Merr.] rotation (corn fertilized at 168-202 kg N ha). Nitrous oxide emissions, soil N mineralization, mid-profile nitrate leaching, and tile flow and nitrate concentrations were measured. Perennial crops quickly reduced nitrate leaching at a 50-cm soil depth as well as concentrations and loads from the tile systems (year 1 tile nitrate concentrations of 10-15 mg N L declined significantly by year 4 in all perennial crops to <0.6 mg N L, with losses of <0.8 kg N ha yr). Nitrous oxide emissions were 2.2 to 7.7 kg N ha yr in the corn-corn-soybean rotation but were <1.0 kg N ha yr by year 4 in the perennial crops. Overall N balances (atmospheric deposition + fertilization + soybean N fixation - harvest, leaching losses, and NO emissions) were positive for corn and soybean (22 kg N ha yr) as well as switchgrass (9.7 kg N ha yr) but were -18 and -29 kg N ha yr for prairie and miscanthus, respectively. Our results demonstrate rapid tightening of the N cycle as perennial biofuel crops established on a rich Mollisol soil.Copyright Â© by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
Relative size of the eye and orbit: an evolutionary and craniofacial constraint model for examining the etiology and disparate incidence of juvenile-onset myopia in humans. - Medical hypotheses
The principal aim of this research is to provide a new model for investigating myopia in humans, and contribute to an understanding of the degree to which modern variation and evolutionary change in orbital and overall craniofacial morphology may help explain the common eye form association with this condition. Recent research into long and short-term evolution of the human orbit reveals a number of changes in this feature, and particularly since the Upper Paleolithic. These include a reduction in orbital depth, a decrease in anterior projection of the upper and lower orbital margins, and most notably, a reduction in orbital volume since the Holocene in East Asia. Reduced orbital volume in this geographic region could exacerbate an existing trend in recent hominin evolution toward larger eyes in smaller orbits, and may help explain the unusually high frequency of myopia in East Asian populations. The objective of the current study is to test a null hypothesis of no relationship between a ratio of orbit to eye volume and spherical equivalent refractive error (SER) in a sample of Chinese adults, and examine how relative size of the eye within the orbit relates to SER between the sexes and across the sample population. Analysis of the orbit, eye, and SER reveals a strong relationship between relative size of the eye within the orbit and the severity of myopic refractive error. An orbit/eye ratio of 3 for females and 3.5 for males (or an eye that occupies approximately 34% and 29% of the orbit, respectively), designates a clear threshold at which myopia develops, and becomes progressively worse as the eye continues to occupy a greater proportion of the orbital cavity. These results indicate that relative size of the eye within the orbit is an important factor in the development of myopia, and suggests that individuals with large eyes in small orbits lack space for adequate development of ocular tissues, leading to compression and distortion of the lithesome globe within the confines of the orbital walls. The results of this study indicate that future research examining the etiology of juvenile-onset myopia, and particularly its correlation with ancestry, sex, age, and intelligence, should consider how the eye interacts with the matrix of structural and functional components of the skull during both ontogenetic and evolutionary morphogenesis.Copyright Â© 2012 Elsevier Ltd. All rights reserved.
The influence of drought and heat stress on long term carbon fluxes of bioenergy crops grown in the Midwestern US. - Plant, cell & environment
Perennial grasses are promising feedstocks for bioenergy production in the Midwestern US. Few experiments have addressed how drought influences their carbon fluxes and storage. This study provides a direct comparison of ecosystem-scale measurements of carbon fluxes associated with miscanthus (Miscanthusâ€‰Ã—â€‰giganteus), switchgrass (Panicum virgatum), restored native prairie and maize (Zea mays) / soybean (Glycine max) ecosystems. The main objective of this study was to assess the influence of a naturally occurring drought during 2012 on key components of the carbon cycle and plant development relative to non-extreme years. The perennials reached full maturity 3-5 years after establishment. Miscanthus had the highest GPP and lowest NEE in 2012 followed by similar values for switchgrass and prairie, and the row crops had the lowest GPP and highest NEE. A post-drought effect was observed for miscanthus. Over the duration of the experiment, perennial ecosystems were carbon sinks, as indicated by negative NECB, while maize/soybean was a net carbon source. Our observations suggest that perennial ecosystems, and in particular miscanthus, can provide high yield and large potential for CO2 fixation even during drought, although drought may negatively influence carbon uptake in the following year, questioning the long-term consequence of its maintained productivity.This article is protected by copyright. All rights reserved.
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