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Linear Measures (linear + measure)
Selected AbstractsMagnetic Resonance Microscopy Defines Ethanol-Induced Brain Abnormalities in Prenatal Mice: Effects of Acute Insult on Gestational Day 8ALCOHOLISM, Issue 6 2009Scott E. Parnell Background:, Magnetic resonance microscopy (MRM), magnetic resonance imaging (MRI) at microscopic levels, provides unprecedented opportunities to aid in defining the full spectrum of ethanol's insult to the developing brain. This is the first in a series of reports that, collectively, will provide an MRM-based atlas of developmental stage-dependent structural brain abnormalities in a Fetal Alcohol Spectrum Disorders (FASD) mouse model. The ethanol exposure time and developmental stage examined for this report is gestational day (GD) 8 in mice, when the embryos are at early neurulation stages; stages present in humans early in the fourth week postfertilization. Methods:, For this study, pregnant C57Bl/6J mice were administered an ethanol dosage of 2.8 g/kg intraperitoneally at 8 days, 0 hour and again at 8 days, 4 hours postfertilization. On GD 17, fetuses that were selected for MRM analyses were immersion fixed in a Bouin's/Prohance® solution. Control fetuses from vehicle-treated dams were stage-matched to those that were ethanol-exposed. The fetal mice were scanned ex vivo at 7.0 T and 512 × 512 × 1024 image arrays were acquired using 3-D spin warp encoding. The resulting 29 ,m (isotropic) resolution images were processed using ITK-SNAP, a 3-D segmentation/visualization tool. Linear and volume measurements were determined for selected brain, head, and body regions of each specimen. Comparisons were made between control and treated fetuses, with an emphasis on determining (dis)proportionate changes in specific brain regions. Results:, As compared with controls, the crown-rump lengths of stage-matched ethanol-exposed GD 17 fetuses were significantly reduced, as were brain and whole body volumes. Volume reductions were notable in every brain region examined, with the exception of the pituitary and septal region, and were accompanied by increased ventricular volumes. Disproportionate regional brain volume reductions were most marked on the right side and were significant for the olfactory bulb, hippocampus, and cerebellum; the latter being the most severely affected. Additionally, the septal region and the pituitary were disproportionately large. Linear measures were consistent with those of volume. Other dysmorphologic features noted in the MR scans were choanal stenosis and optic nerve coloboma. Conclusions:, This study demonstrates that exposure to ethanol occurring in mice at stages corresponding to the human fourth week postfertilization results in structural brain abnormalities that are readily identifiable at fetal stages of development. In addition to illustrating the utility of MR microscopy for analysis of an FASD mouse model, this work provides new information that confirms and extends human clinical observations. It also provides a framework for comparison of structural brain abnormalities resulting from ethanol exposure at other developmental stages and dosages. [source] Comparison of neuronal and hemodynamic measures of the brain response to visual stimulation: An optical imaging studyHUMAN BRAIN MAPPING, Issue 1 2001Gabriele Gratton Abstract The noninvasive mapping of hemodynamic brain activity has led to significant advances in neuroimaging. This approach is based in part on the assumption that hemodynamic changes are proportional to (and therefore constitute a linear measure of) neuronal activity. We report a study investigating the quantitative relationship between neuronal and hemodynamic measures. This study exploited the fact that optical imaging methods can simultaneously provide noninvasive measures of neuronal and hemodynamic activity from the same region of the brain. We manipulated visual stimulation frequency and measured responses from the medial occipital area of 8 young adults. The results were consistent with a model postulating a linear relationship between the neuronal activity integrated over time and the amplitude of the hemodynamic response. The hemodynamic response colocalized with the neuronal response. These data support the use of quantitative neuroimaging methods to infer the intensity and localization of neuronal activity in occipital areas. Hum. Brain Mapping 13:13,25, 2001. © 2001 Wiley-Liss, Inc. [source] Morphological variability in the Cuatro Cienegas cichlid, Cichlasoma minckleyiJOURNAL OF FISH BIOLOGY, Issue 2 2003J. Trapani The endemic cichlids of the Cuatro Cienegas Basin, Coahuila, Mexico are currently grouped in a single polymorphic species, Cichlasoma minckleyi. Two morphs of C. minckleyi were distinguished largely by features of the trophic apparatus, especially the pharyngeal dentition. Variation in body shape, based upon analysis of a set of linear measures, was continuous and did not allow recognition of discrete morphs. Individuals raised in the laboratory on several different diets indicated that trophic morphology had an important genetic component. Individuals raised in the laboratory, however, did not differentiate to the degree seen in comparably sized individuals collected at Cuatro Cienegas. This may be because snails used as food in the experiments were not as hard as endemic snails and indicated that some aspects of trophic morphology were also dependent upon environmental cues. [source] Exploring alternative conceptions from Newtonian dynamics and simple DC circuits: Links between item difficulty and item confidenceJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 2 2006Maja Planinic Croatian 1st-year and 3rd-year high-school students (N,=,170) completed a conceptual physics test. Students were evaluated with regard to two physics topics: Newtonian dynamics and simple DC circuits. Students answered test items and also indicated their confidence in each answer. Rasch analysis facilitated the calculation of three linear measures: (a) an item-difficulty measure based upon all responses, (b) an item-confidence measure based upon correct student answers, and (c) an item-confidence measure based upon incorrect student answers. Comparisons were made with regard to item difficulty and item confidence. The results suggest that Newtonian dynamics is a topic with stronger students' alternative conceptions than the topic of DC circuits, which is characterized by much lower students' confidence on both correct and incorrect answers. A systematic and significant difference between mean student confidence on Newtonian dynamics and DC circuits items was found in both student groups. Findings suggest some steps for physics instruction in Croatia as well as areas of further research for those in science education interested in additional techniques of exploring alternative conceptions. © 2005 Wiley Periodicals, Inc. J Res Sci Teach 43: 150,171, 2006 [source] Body size estimation of small-bodied humans: Applicability of current methodsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010H.K. Kurki Abstract Body size (stature and mass) estimates are integral to understanding the lifeways of past populations.Body size estimation of an archaeological skeletal sample can be problematic when the body size or proportions of the population are distinctive. One such population is that of the Holocene Later Stone Age (LSA) of southern Africa, in which small stature (mean femoral length = 407 mm, n = 52) and narrow pelves (mean bi-iliac breadth = 210 mm, n = 50) produce a distinctive adult body size/shape, making it difficult to identify appropriate body size estimation methods. Material culture, morphology, and culture history link the Later Stone Age people with the descendant population collectively known as the Khoe-San. Stature estimates based on skeletal "anatomical" linear measures (the Fully method) and on long bone length are compared, along with body mass estimates derived from "morphometric" (bi-iliac breath/stature) and "biomechanical" (femoral head diameter) methods, in a LSA adult skeletal sample (n = 52) from the from coastal and near-coastal regions of South Africa. Indices of sexual dimorphism (ISD) for each method are compared with data from living populations. Fully anatomical stature is most congruent with Olivier's femur + tibia method, although both produce low ISD. McHenry's femoral head body mass formula produces estimates most consistent with the bi-iliac breadth/staturemethod for the females, although the males display higher degrees of disagreement among methods. These results highlight the need for formulae derived from reference samples from a wider range of body sizes to improve the reliability of existing methods. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. 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