Academic literature on the topic 'Grey matter density'

Abstract Objective The development of persistent pain following total knee arthroplasty (TKA) is common, but its underlying mechanisms are unknown. The goal of the study was to assess brain grey matter structure and its correlation with function of the nociceptive system in people with good and poor outcomes following TKA. Subjects Thirty-one people with LOW_PAIN (<3/10 on the numerical ratings scale [NRS]) at six months following TKA and 15 people with HIGH_PAIN (≥3/10 on the NRS) were recruited into the study. Methods Grey matter in key brain areas related to nociception was analyzed using voxel-based morphometry (VBM). Nociceptive facilitatory and inhibitory processes were evaluated using quantitative sensory testing (QST). QST scores and grey matter density in prespecified brain regions were compared between the LOW_PAIN and HIGH_PAIN groups. Regression analyses were used to analyze the associations between the grey matter and QST scores. Results There were no between-group differences in QST measures. In the VBM analysis, the HIGH_PAIN group had a higher grey matter density in the right amygdala, right nucleus accumbens, and in the periaqueductal grey (PAG), but lower grey matter density in the dorsal part of the left caudate nucleus. Grey matter density in the right amygdala and PAG correlated positively with temporal summation of pain. Conclusions Persistent pain at six months after TKA is associated with a higher grey matter density in the regions involved in central sensitization and pain-related fear, which may contribute to the development of persistent pain after surgery.

BackgroundOur previous genome-wide association study (CONVERGE sample) identified significant association between single nucleotide polymorphisms (SNPs) near the SIRT1 gene and major depressive disorder (MDD) in Chinese populations.AimsTo investigate whether SNPs across the SIRT1 gene locus affect regional grey matter density in the Han Chinese population.MethodT1-weighted structural magnetic resonance imaging was conducted on 92 healthy participants from Eastern China. Grey matter was segmented from the image, which consisted of voxel-wise grey matter density. The effect of SIRT1 SNPs on grey matter density was determined by a multiple linear regression framework.ResultsSNP rs4746720 was significantly associated with grey matter density in two brain cortical regions: the orbital part of the right inferior frontal gyrus and the orbital part of the left inferior frontal gyrus (family-wise error-corrected P < 0.05; voxel-wise P < 0.001). Also, rs4746720 exceeded genome-wide significance in association with MDD in our CONVERGE sample (P = 3.32 × 10−08, odds ratio 1.161).ConclusionsOur results provided evidence for a potential role of the SIRT1 gene in the brain, implying a possible pathophysiological mechanism underlying susceptibility to MDD.

BackgroundAlthough a number of functional imaging studies are in agreement in suggesting orbitofrontal and subcortical hyperfunction in the pathophysiology of obsessive–compulsive disorder (OCD), the structural findings have been contradictory.AimsTo investigate grey matter abnormalities in patients with OCD by employing a novel voxel-based analysis of magnetic resonance images.MethodStatistical parametric mapping was utilised to compare segmented grey matter images from 25 patients with OCD with those from 25 matched controls.ResultsIncreased regional grey matter density was found in multiple cortical areas, including the left orbitofrontal cortex, and in subcortical areas, including the thalamus. On the other hand, regions of reduction were confined to posterior parts of the brain, such as the left cuneus and the left cerebellum.ConclusionsIncreased grey matter density of frontal–subcortical circuits, consonant with the hypermetabolic findings from functional imaging studies, seems to exist in patients with OCD, and cerebellar dysfunction may be involved in the pathophysiology of OCD.

Visceral adipose tissue accumulation is an important determinant of metabolic risk and can be estimated by the visceral adiposity index (VAI). Visceral adiposity may impact brain regions involved in eating behavior. We aimed to examine the association between adiposity measurements, binge eating behavior, and grey matter density. In 20 men and 59 women with severe obesity, Grey matter density was measured by voxel-based morphometry for six regions of interest associated with reward, emotion, or self-regulation: insula, orbitofrontal cortex, caudal and rostral anterior cingulate cortex (ACC), ventromedial prefrontal cortex (vmPFC), and dorsolateral prefrontal cortex (DLPFC). Binge eating behavior, depression and impulsivity was assessed by the Binge Eating Scale, Beck Depression Inventory and UPPS Impulsive Behavior Scale, respectively. Men and women were distinctively divided into two subgroups (low-VAI and high-VAI) based on the mean VAI score. Women with high-VAI were characterized by metabolic alterations, higher binge eating score and lower grey matter density in the caudal ACC compared to women with low-VAI. Men with high-VAI were characterized by a higher score for the sensation-seeking subscale of the UPPS–Impulsive Behavior Scale compared to men with low-VAI. Using a moderation–mediation analysis, we found that grey matter density in the caudal ACC mediates the association between VAI and binge eating score. In conclusion, visceral adiposity is associated with higher binge eating severity in women. Decreased grey matter density in the caudal ACC, a region involved in cognition and emotion regulation, may influence this relationship.

Given that there are neural markers for the acquisition of a non-verbal skill, we review evidence of neural markers for the acquisition of vocabulary. Acquiring vocabulary is critical to learning one's native language and to learning other languages. Acquisition requires the ability to link an object concept (meaning) to sound. Is there a region sensitive to vocabulary knowledge? For monolingual English speakers, increased vocabulary knowledge correlates with increased grey matter density in a region of the parietal cortex that is well-located to mediate an association between meaning and sound (the posterior supramarginal gyrus). Further this region also shows sensitivity to acquiring a second language. Relative to monolingual English speakers, Italian–English bilinguals show increased grey matter density in the same region. Differences as well as commonalities might exist in the neural markers for vocabulary where lexical distinctions are also signalled by tone. Relative to monolingual English, Chinese multilingual speakers, like European multilinguals, show increased grey matter density in the parietal region observed previously. However, irrespective of ethnicity, Chinese speakers (both Asian and European) also show highly significant increased grey matter density in two right hemisphere regions (the superior temporal gyrus and the inferior frontal gyrus). They also show increased grey matter density in two left hemisphere regions (middle temporal and superior temporal gyrus). Such increases may reflect additional resources required to process tonal distinctions for lexical purposes or to store tonal differences in order to distinguish lexical items. We conclude with a discussion of future lines of enquiry.

BackgroundOur understanding of anatomical differences in people with autistic-spectrum disorder, is based on mixed-gender or male samples.AimsTo study regional grey-matter and white-matter differences in the brains of women with autistic-spectrum disorder.MethodWe compared the brain anatomy of 14 adult women with autistic-spectrum disorder with 19 controls using volumetric magnetic resonance imaging and voxel-based morphometry Results Women with autistic-spectrum disorder had a smaller density bilaterally of grey matter in the frontotemporal cortices and limbic system, and of white matter in the temporal lobes (anterior) and pons. In contrast, they had a larger white-matter density bilaterally in regions of the association and projection fibres of the frontal, parietal, posterior temporal and occipital lobes, in the commissural fibres of the corpus callosum (splenium) and cerebellum (anterior lobe). Further, we found a negative relationship between reduced grey-matter density in right limbic regions and social communication ability.ConclusionsWomen with autistic-spectrum disorder have significant differences in brain anatomy from controls, in brain regions previously reported as abnormal in adult men with the disorder. Some anatomical differences may be related to clinical symptoms.

We used immunochemistry, light microscopy and stereological methods for quantitative description of the microvascular network in 13 tissue samples of the human brain. While the tortuosity of microvessels was comparable in all brain parts under study, the length density of microvessels was higher in subcortical grey matter (652.5±162.0 mm-2) and in the cortex (570.9±71.8 mm-2) than in the white matter (152.7±42.0 mm-2). The numerical density of microvessels was higher in subcortical grey matter (3782.0±1602.0 mm-3) and cerebral cortex (3160.0±638.4 mm-3) than in white matter (627.7±318.5 mm-3). We developed simulation software gensei which generates series of images representing three-dimensional models of microvessels with known length density, volume fraction, and surface density. The simulations are statistically similar to real microvessel networks and can be used for computer modelling of brain perfusion.

Genetic architecture explains about characteristics of different types of genetic variants which affect the traits for heritable variability. The present review is to document the deeper understanding of the genetic architecture of grey matter obtained from reliable sources of information which are associated with grey matter density and volume, cortical thickness, surface area, genetic variants, genetic heritability and genetic effects including Alzheimer disease, Huntington disease and some various diseases. The literature search on genetic architecture was carried out for papers published by google scholar and PubMed with the intention of retrieving all original reports that were relevant to it. The quality assessment of selected studies was conducted for 77 collected articles. This review is an attempt to update recent advances and provide a deeper understanding of the genetic architecture of grey matter which benefits scientists and geneticists.

Dissertação de mestrado em Psicologia Aplicada
Creativity is a complex construct since there isn´t a consensual definition among the authors in the field. Numerous instruments have been used to evaluate this construct, one of them was used for Portuguese population properly validated, to study creative personality, that is, the Creative Personality Scale (CPS). Numerous studies have tried to understand neural correlates of creative personality. This specific study intends to explore the association between creative personality scale score and gray matter (GM) density using Voxel-Based Morphometry (VBM), through volumetrical alterations of gray matter (GM). In order to achieve this, the Creative Personality Scale was administered in adolescents and young adults and GM densities were measured through VBM, analyzing the volumetrical alterations of GMV. The results observed confirmed that there is a negative association between GM densities and scores of CPS. This means that a decreased on the GM was found in Superior Frontal Gyrus (SFG), Middle Frontal Gyrus (MFG), Inferior Frontal Gyrus (IFG) and Left Caudate(LC) which was related to an increase of creative personality. We concluded that the smaller the density of GM, the greater were the scores of creative personalities.
A criatividade é um constructo complexo visto que, não existe uma definição consensual entre os autores deste campo. Inúmeros instrumentos têm vindo a avaliar este constructo, sendo que, um deles foi usado na população portuguesa, devidamente validado para estudar a personalidade criativa, a Escala da Personalidade Criativa. Vários estudos têm tentado perceber os correlatos neurais da personalidade criativa. Este estudo em específico visa explorar a associação entre a personalidade criativa e a densidade da substância cinzenta avaliada através da Voxel-Based Morphometry (VBM), analisando as alterações volumétricas na substância cinzenta. Assim, foi administrada a Escala de Personalidade Criativa a adolescentes e jovens adultos e recolhidas imagens de ressonância magnética estrutural para estudar a possível associação entre os scores da personalidade criativa e as alterações volumétricas da substância cinzenta. Os resultados observados confirmam que existe uma associação negativa entre o volume de substância cinzenta e os scores da escala da personalidade criativa, o que significa que foi encontrado um decréscimo de substância cinzenta no Giro Frontal Superior, Giro Frontal Médio, Giro Frontal Inferior e Caudado Esquerdo, associada a um aumento da personalidade criativa. Concluímos que quanto menor o volume de substância cinzenta maiores os scores de personalidade criativa.
Apoio disponibilizado através do financiamento prestado oriundo do anterior projeto com a referência POCI-01-0145-FEDER-028228

The doctoral dissertation: Searching for pathomechanisms of late-life minor depression – a combined MRI, biomarker and meta-analytic study was one of the first studies investigating the underlying pathophysiology of minor depression. The dissertation comprises a systematic review of the prevalence rates of minor depression, two meta-analyses of peripheral BDNF changes in major depressive disorder, as well as two original studies investigating serum BDNF, S100B and NSE levels and gray matter changes in minor depression. The limitations of studies and proposed improvements to the study design are discussed extensively.:1. INTRODUCTION 1.1 Motivation 1.1.1 Minor depression in the spectrum of psychiatric disorders 1.1.2 Minor depression is prevalent but unrecognized. 1.2 Theoretical background 1.2.1 Overview of depression hypotheses 1.2.2 Neurotrophic hypothesis of depressive disorders 1.2.3 Glial hypothesis of depressive disorders 1.2.4 Structural neuroimaging changes in major depression 1.3. Rationale and hypotheses of the empirical studies 1.3.1 Research questions 1.3.2 Research hypotheses 2. EMPIRICAL STUDIES 2.1 The prevalence of minor depression in the late life 2.2 The meta-analysis of BDNF changes in mood disorders 2.3 The meta-analysis of BDNF changes following ECT in depression 2.4 Serum biomarkers in minor depression 2.5 Structural brain imaging in minor depression 3. GENERAL DISCUSSION 3.1 Summary of results 3.2 Implications for research 3.3 Implications for clinical studies SUMMARY REFERENCES APPENDIX A: DECLARATION OF CONTRIBUTION APPENDIX B: STATEMENT OF AUTHORSHIP APPENDIX C: CURRICULUM VITAEAPPENDIX D: ACADEMIC CONTRIBUTIONS APPENDIX E: ACKNOWLEDGMENT

Schizophrenia is a brain disease with unknown etiology; a variety of neurodevelopmental mechanisms contribute to its pathogenesis. In this chapter, we review some of the most salient neurobiological findings that seem to be linked with the pathophysiology of psychosis generally and schizophrenia specifically. Several important findings have been made from neuroimaging and neuropathology, including reduced whole-brain volume, enlarged ventricles, and decreased cortical gray matter. Abnormalities in the prefrontal cortex, such as decreased dendritic spine density, are particularly important for cognitive and negative symptoms in schizophrenia. Functional imaging suggests that patterns of activation may be closely linked to symptom clusters. We will review neurotransmitter abnormalities, especially dopamine but also glutamate and GABA, and relevant circuitry and connectivity problems related to pathology. Finally, we will discuss genetics and heritability, and the challenges of identifying relevant loci in such a complex disorder.

Bones are multifunctional passive organs of movement that supports soft tissue and directly attached muscles. They also protect internal organs and are a reserve of calcium, phosphorus and magnesium. Each bone is covered with periosteum, and the adjacent bone surfaces are covered by articular cartilage. Histologically, the bone is an organ composed of many different tissues. The main component is bone tissue (cortical and spongy) composed of a set of bone cells and intercellular substance (mineral and organic), it also contains fat, hematopoietic (bone marrow) and cartilaginous tissue. Bones are a tissue that even in adult life retains the ability to change shape and structure depending on changes in their mechanical and hormonal environment, as well as self-renewal and repair capabilities. This process is called bone turnover. The basic processes of bone turnover are: • bone modeling (incessantly changes in bone shape during individual growth) following resorption and tissue formation at various locations (e.g. bone marrow formation) to increase mass and skeletal morphology. This process occurs in the bones of growing individuals and stops after reaching puberty • bone remodeling (processes involve in maintaining bone tissue by resorbing and replacing old bone tissue with new tissue in the same place, e.g. repairing micro fractures). It is a process involving the removal and internal remodeling of existing bone and is responsible for maintaining tissue mass and architecture of mature bones. Bone turnover is regulated by two types of transformation: • osteoclastogenesis, i.e. formation of cells responsible for bone resorption • osteoblastogenesis, i.e. formation of cells responsible for bone formation (bone matrix synthesis and mineralization) Bone maturity can be defined as the completion of basic structural development and mineralization leading to maximum mass and optimal mechanical strength. The highest rate of increase in pig bone mass is observed in the first twelve weeks after birth. This period of growth is considered crucial for optimizing the growth of the skeleton of pigs, because the degree of bone mineralization in later life stages (adulthood) depends largely on the amount of bone minerals accumulated in the early stages of their growth. The development of the technique allows to determine the condition of the skeletal system (or individual bones) in living animals by methods used in human medicine, or after their slaughter. For in vivo determination of bone properties, Abstract 10 double energy X-ray absorptiometry or computed tomography scanning techniques are used. Both methods allow the quantification of mineral content and bone mineral density. The most important property from a practical point of view is the bone’s bending strength, which is directly determined by the maximum bending force. The most important factors affecting bone strength are: • age (growth period), • gender and the associated hormonal balance, • genotype and modification of genes responsible for bone growth • chemical composition of the body (protein and fat content, and the proportion between these components), • physical activity and related bone load, • nutritional factors: – protein intake influencing synthesis of organic matrix of bone, – content of minerals in the feed (CA, P, Zn, Ca/P, Mg, Mn, Na, Cl, K, Cu ratio) influencing synthesis of the inorganic matrix of bone, – mineral/protein ratio in the diet (Ca/protein, P/protein, Zn/protein) – feed energy concentration, – energy source (content of saturated fatty acids - SFA, content of polyun saturated fatty acids - PUFA, in particular ALA, EPA, DPA, DHA), – feed additives, in particular: enzymes (e.g. phytase releasing of minerals bounded in phytin complexes), probiotics and prebiotics (e.g. inulin improving the function of the digestive tract by increasing absorption of nutrients), – vitamin content that regulate metabolism and biochemical changes occurring in bone tissue (e.g. vitamin D3, B6, C and K). This study was based on the results of research experiments from available literature, and studies on growing pigs carried out at the Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences. The tests were performed in total on 300 pigs of Duroc, Pietrain, Puławska breeds, line 990 and hybrids (Great White × Duroc, Great White × Landrace), PIC pigs, slaughtered at different body weight during the growth period from 15 to 130 kg. Bones for biomechanical tests were collected after slaughter from each pig. Their length, mass and volume were determined. Based on these measurements, the specific weight (density, g/cm3) was calculated. Then each bone was cut in the middle of the shaft and the outer and inner diameters were measured both horizontally and vertically. Based on these measurements, the following indicators were calculated: • cortical thickness, • cortical surface, • cortical index. Abstract 11 Bone strength was tested by a three-point bending test. The obtained data enabled the determination of: • bending force (the magnitude of the maximum force at which disintegration and disruption of bone structure occurs), • strength (the amount of maximum force needed to break/crack of bone), • stiffness (quotient of the force acting on the bone and the amount of displacement occurring under the influence of this force). Investigation of changes in physical and biomechanical features of bones during growth was performed on pigs of the synthetic 990 line growing from 15 to 130 kg body weight. The animals were slaughtered successively at a body weight of 15, 30, 40, 50, 70, 90, 110 and 130 kg. After slaughter, the following bones were separated from the right half-carcass: humerus, 3rd and 4th metatarsal bone, femur, tibia and fibula as well as 3rd and 4th metatarsal bone. The features of bones were determined using methods described in the methodology. Describing bone growth with the Gompertz equation, it was found that the earliest slowdown of bone growth curve was observed for metacarpal and metatarsal bones. This means that these bones matured the most quickly. The established data also indicate that the rib is the slowest maturing bone. The femur, humerus, tibia and fibula were between the values of these features for the metatarsal, metacarpal and rib bones. The rate of increase in bone mass and length differed significantly between the examined bones, but in all cases it was lower (coefficient b <1) than the growth rate of the whole body of the animal. The fastest growth rate was estimated for the rib mass (coefficient b = 0.93). Among the long bones, the humerus (coefficient b = 0.81) was characterized by the fastest rate of weight gain, however femur the smallest (coefficient b = 0.71). The lowest rate of bone mass increase was observed in the foot bones, with the metacarpal bones having a slightly higher value of coefficient b than the metatarsal bones (0.67 vs 0.62). The third bone had a lower growth rate than the fourth bone, regardless of whether they were metatarsal or metacarpal. The value of the bending force increased as the animals grew. Regardless of the growth point tested, the highest values were observed for the humerus, tibia and femur, smaller for the metatarsal and metacarpal bone, and the lowest for the fibula and rib. The rate of change in the value of this indicator increased at a similar rate as the body weight changes of the animals in the case of the fibula and the fourth metacarpal bone (b value = 0.98), and more slowly in the case of the metatarsal bone, the third metacarpal bone, and the tibia bone (values of the b ratio 0.81–0.85), and the slowest femur, humerus and rib (value of b = 0.60–0.66). Bone stiffness increased as animals grew. Regardless of the growth point tested, the highest values were observed for the humerus, tibia and femur, smaller for the metatarsal and metacarpal bone, and the lowest for the fibula and rib. Abstract 12 The rate of change in the value of this indicator changed at a faster rate than the increase in weight of pigs in the case of metacarpal and metatarsal bones (coefficient b = 1.01–1.22), slightly slower in the case of fibula (coefficient b = 0.92), definitely slower in the case of the tibia (b = 0.73), ribs (b = 0.66), femur (b = 0.59) and humerus (b = 0.50). Bone strength increased as animals grew. Regardless of the growth point tested, bone strength was as follows femur > tibia > humerus > 4 metacarpal> 3 metacarpal> 3 metatarsal > 4 metatarsal > rib> fibula. The rate of increase in strength of all examined bones was greater than the rate of weight gain of pigs (value of the coefficient b = 2.04–3.26). As the animals grew, the bone density increased. However, the growth rate of this indicator for the majority of bones was slower than the rate of weight gain (the value of the coefficient b ranged from 0.37 – humerus to 0.84 – fibula). The exception was the rib, whose density increased at a similar pace increasing the body weight of animals (value of the coefficient b = 0.97). The study on the influence of the breed and the feeding intensity on bone characteristics (physical and biomechanical) was performed on pigs of the breeds Duroc, Pietrain, and synthetic 990 during a growth period of 15 to 70 kg body weight. Animals were fed ad libitum or dosed system. After slaughter at a body weight of 70 kg, three bones were taken from the right half-carcass: femur, three metatarsal, and three metacarpal and subjected to the determinations described in the methodology. The weight of bones of animals fed aa libitum was significantly lower than in pigs fed restrictively All bones of Duroc breed were significantly heavier and longer than Pietrain and 990 pig bones. The average values of bending force for the examined bones took the following order: III metatarsal bone (63.5 kg) <III metacarpal bone (77.9 kg) <femur (271.5 kg). The feeding system and breed of pigs had no significant effect on the value of this indicator. The average values of the bones strength took the following order: III metatarsal bone (92.6 kg) <III metacarpal (107.2 kg) <femur (353.1 kg). Feeding intensity and breed of animals had no significant effect on the value of this feature of the bones tested. The average bone density took the following order: femur (1.23 g/cm3) <III metatarsal bone (1.26 g/cm3) <III metacarpal bone (1.34 g / cm3). The density of bones of animals fed aa libitum was higher (P<0.01) than in animals fed with a dosing system. The density of examined bones within the breeds took the following order: Pietrain race> line 990> Duroc race. The differences between the “extreme” breeds were: 7.2% (III metatarsal bone), 8.3% (III metacarpal bone), 8.4% (femur). Abstract 13 The average bone stiffness took the following order: III metatarsal bone (35.1 kg/mm) <III metacarpus (41.5 kg/mm) <femur (60.5 kg/mm). This indicator did not differ between the groups of pigs fed at different intensity, except for the metacarpal bone, which was more stiffer in pigs fed aa libitum (P<0.05). The femur of animals fed ad libitum showed a tendency (P<0.09) to be more stiffer and a force of 4.5 kg required for its displacement by 1 mm. Breed differences in stiffness were found for the femur (P <0.05) and III metacarpal bone (P <0.05). For femur, the highest value of this indicator was found in Pietrain pigs (64.5 kg/mm), lower in pigs of 990 line (61.6 kg/mm) and the lowest in Duroc pigs (55.3 kg/mm). In turn, the 3rd metacarpal bone of Duroc and Pietrain pigs had similar stiffness (39.0 and 40.0 kg/mm respectively) and was smaller than that of line 990 pigs (45.4 kg/mm). The thickness of the cortical bone layer took the following order: III metatarsal bone (2.25 mm) <III metacarpal bone (2.41 mm) <femur (5.12 mm). The feeding system did not affect this indicator. Breed differences (P <0.05) for this trait were found only for the femur bone: Duroc (5.42 mm)> line 990 (5.13 mm)> Pietrain (4.81 mm). The cross sectional area of the examined bones was arranged in the following order: III metatarsal bone (84 mm2) <III metacarpal bone (90 mm2) <femur (286 mm2). The feeding system had no effect on the value of this bone trait, with the exception of the femur, which in animals fed the dosing system was 4.7% higher (P<0.05) than in pigs fed ad libitum. Breed differences (P<0.01) in the coross sectional area were found only in femur and III metatarsal bone. The value of this indicator was the highest in Duroc pigs, lower in 990 animals and the lowest in Pietrain pigs. The cortical index of individual bones was in the following order: III metatarsal bone (31.86) <III metacarpal bone (33.86) <femur (44.75). However, its value did not significantly depend on the intensity of feeding or the breed of pigs.

This chapter shows that, after cosmological recombination, the Universe had entered the “dark ages,” during which the relic cosmic microwave background (CMB) light from the Big Bang gradually faded away. During this “pregnancy” period (which lasted hundreds of millions of years), the seeds of small density fluctuations planted by inflation in the matter distribution grew until they eventually collapsed to make the first galaxies. In addition to the density evolution, the second key “initial condition” for galaxy formation is the temperature of the hydrogen and helium gas that had likewise collapsed into the first galaxies. Here, the chapter describes the first stages of these processes and introduces the methods conventionally used to describe the fluctuations. It follows the evolution of structure in the linear regime, when the perturbations are small.

Natural resource scientists, concerned citizens, and government officials are interested in reconstructing disturbed environments for reforestation and agricultural productivity. We examined Clearfield County in Pennsylvania, USA, to develop a predictive model to reconstruct the landscape for seven agronomic crops (corn, corn silage, oats, alfalfa hay, red clover, bluegrass, and soybeans) and thirteen woody plants (white cedar, lilac, highbush cranberry, Amur maple, gray dogwood, peashrub, white spruce, white pine, red maple, red pine, jack pine, nannyberry, and white ash). A significant predictive model (p ≤ 0.001) was generated explaining 96.94% of the variance, with percent clay, bulk density, hydraulic conductivity, available water capacity, pH, percent organic matter, percent rock fragments, slope, topographic position, and electrical conductivity explored as main effect terms, plus squared terms, and first order interaction terms. The model is not over-specified and each predictor is significant (p ≤ 0.05). The modeling effort suggests that there are at least several clusters of vegetation preference dimensions based upon the terrain of the landscape. The model provides insight into how to reconstruct the disturbed environment for vegetation in the study area.

One of the obstacles of culturing functioning vital tissues in vitro is to obtain a substantial biomass at a physiological cell density (&gt;108cells/cm3). At this high density, the diffusion length of metabolites is limited to ~100um. As a matter of fact, in real tissue, almost all the cells are located within 100um distance from the capillaries [1]. Studies [2, 3] also confirmed that the cells in the artificial tissue cannot be properly cultured when they are further than 400um from the external nutrient source. Therefore, to culture three dimensional artificial tissue with substantial biomass, vascularization is necessary to enhance the metabolites transport. The short diffusion length of the metabolites requires high capillary density (&gt;100/mm2) in vascularization. To meet this need, we have developed a novel high resolution and high speed 3D microfabrication technique, the projection microstereolithography[4] to explore microcirculatory networks with high density (&gt;150/mm2). Using this technology we designed and fabricated the microreactors as shown in Figure 1. In our samples, 800um PEG microcapillaries with 20um inner radius and 40um outer radius with pitch of 96um are fabricated. Two rings as inlet and outlet are connected to external supply of culture medium. We designed the parameters of the vascularized microbioreactor based on the simulations of oxygen and carbon dioxide transport and metabolism in hepatocytes. As shown in Figure 2, the capillaries are arranged in a hexagonal way. According to the geometric symmetry, the final simulation domain is divided into 2 regions, the polymer capillary wall and the tissue. We assumed that a culture media with dissolved oxygen is pumped through the capillaries at 1.5mm/s rate and diffuses through the capillary wall, into the hepatocytes. The consumption of oxygen follows Michaelis-Menten kinetics [5, 6] and the metabolic rate of carbon dioxide is assumed to be proportional to that of oxygen by a fixed quotient (-0.81) which is addressed and studied by other groups [7]. The carbon dioxide diffuses into the capillaries and can be carried away through the flow of the culture medium. Our simulation indicates that the bottleneck of effective oxygen transport is the permeability of the polymer materials. The oxygen concentration drops off about 90% after diffusing through the capillary wall. It is predicted that the diffusion length at the inlet is 74um and 48um at the outlet; the rapid drop of carbon dioxide concentration also happens across the capillary wall. The predicted carbon dioxide concentration in the tissue is ~80nmol/cm3; this value is much smaller than the toxic value (100mmHg or 3umol/cm3) reported by David Gray and coworkers [8]. In Figure 2, we present the effect of the permeability of the capillary polymer materials on the diffusion length of oxygen and the concentration of carbon dioxide in the tissue. Our study indicates the existence of an optimal permeability for the capillary network, at which the overall diffusion length of oxygen is maximized. Interestingly, we also found a maximum concentration of carbon dioxide in the cultured tissue as the permeability of the polymer material changes. We attribute it to the competition between the tissue thickness and the permeability. Higher permeability increases the cultured tissue thickness, and also increases the ability of capillary to empty carbon dioxide. Not only is this model applicable for oxygen and carbon dioxide, but also for the transport of other metabolites. As an ongoing experimental effort, our fluorescent microscopy measurement validated the diffusion transport of fluorescent species from the capillary (Figure 3). Experiments are also in progress on the oxygen diffusion from the capillaries will cell cultures of high density on the PEG scaffold by introducing proper indicators. In summary, we have established a method to design and manufacture vascularized microcirculatory network to enhance the mass transport during the tissue culture. To ensure the effective nutrient delivery and wastes removal, our numerical simulation also confirms that it is essential to embed high density microcapillaries with optimal permeability.