Copyright (c) 2009 All rights reserved. http://works.bepress.com/david_dewitt Recent documents in David A DeWitt Ph.D. en-us Wed, 05 Aug 2009 06:00:21 PDT 3600 http://works.bepress.com/david_dewitt/22 http://works.bepress.com/david_dewitt/22 Tue, 21 Jul 2009 13:42:49 PDT Many studies have yielded conflicting results regarding the toxicity of AB, the peptide which is the principal component of senile plaques in brains of patients with Alzheimer's disease. Using in vitro and in vivo models, we have studied the role of glial cells and extracellular matrix molecules m mediating the effects of AB. Glial cells respond to AB substrate by accumulating and depositing chondroitin sulfate proteoglycans (CSPGs) which are inhibitory to neurite outgrowth. CSPGs are present around the senile plaque core, an area with both dystrophic neurites and a general decrease in normal neurites. We suggest that CSPG may contribute to the pathology by leading to regenerative failure of neurites surrounding senile plaques. David A. DeWitt http://works.bepress.com/david_dewitt/20 http://works.bepress.com/david_dewitt/20 Tue, 21 Jul 2009 13:42:30 PDT After the theory of spontaneous generation was discredited, only religious explanations were offered to explain the origin of life. Alexander Oparin (1894-1980), an atheist, suggested that natural chemical reactions produced biological molecules that came together to form the first living thing. Later, Stanley Miller tested this hypothesis and produced chemical "building blocks" but not life itself. In spite of much progress, there is still no clear consensus on how life originated on Earth. Some scientists are even looking to outer space for the origin of life. David A. DeWitt http://works.bepress.com/david_dewitt/21 http://works.bepress.com/david_dewitt/21 Tue, 21 Jul 2009 13:42:02 PDT Science educators holding an evolutionary worldview are concerned about the teaching of young -Earth creationism (YEC) and generally oppose its presentation in public schools. This paper examines the influence of a YEC apologetics course on Creation and evolution worldview attitudes of Liberty University students. The creation worldview test (CWT) was administered and a total scale score along with three subscales scores in theology, science and age were analyzed. Student pre-test scores indicated some weaknesses, suggesting departure from a solid YEC worldview. Following the course, students shifted significantly toward stronger agreement with the YEC position in total score, science and age. The results demonstrate that when Christian college students are taught from a YEC perspective, they shift toward stronger beliefs in YEC. Tom Henderson http://works.bepress.com/david_dewitt/18 http://works.bepress.com/david_dewitt/18 Mon, 15 Jun 2009 06:14:00 PDT David A. DeWitt http://works.bepress.com/david_dewitt/17 http://works.bepress.com/david_dewitt/17 Mon, 15 Jun 2009 06:13:58 PDT What one believes about origins is a significant component of an overall worldview. An ongoing study at Liberty University is being conducted to define and measure a creationist worldview while determining factors that influence the beliefs and attitudes about origins in a Christian college student population. The Creation Worldview Test (CWT) was administered before and after completion of a required apologetics course. Previous attendance at a creation seminar or course was associated with a stronger initial creation worldview, however prior completion of a college science course appeared to have no impact. Importantly, students who attended a public high school had a significantly weaker initial creation worldview than those who attended Christian high schools or home school. Following the apologetics course which was taught from a young-Earth Creation perspective, a large number of students showed a much stronger creation worldview. In particular, the number of students in the 'conservative Biblical theism' category doubled from 64 to 128 (out of 195 students in the study). These results demonstrate the importance and the clear impact of teaching students from a young-Earth Creation perspective. David A. Dewitt http://works.bepress.com/david_dewitt/19 http://works.bepress.com/david_dewitt/19 Mon, 15 Jun 2009 06:13:23 PDT Motor proteins convert chemical energy into work, thereby generating persistent motion of cellular and subcellular objects. The velocities of motor proteins as a function of opposing loads have been previously determined in vitro for single motors. These single molecule "force-velocity curves" have been useful for elucidating motor kinetics and for estimating motor performance under physiological loads due to, for example, the cytoplasmic drag force on transported organelles. Here we report forcevelocity curves for single and multiple motors measured in vivo. Using motion enhanced differential interference contrast (MEDIC) movies of living NT2 (neuron-committed teratocarcinoma) cells at 37°C, three parameters were measured-velocity (v), radius (a), and effective cytoplasmic viscosity (n1)-as they applied to moving vesicles. These parameters were combined in Stokes' equation, F= 6panv1, to determine the force, F, required to transport a single intracellular particle at velocity, v. In addition, the number of active motors was inferred from the multimodal pattern seen in a normalized velocity histogram. Using this inference, the resulting in vivo force-velocity curve for a single motor agrees with previously reported in vitro single motor force-velocity curves. Interestingly, however, the curves for two and three motors lie significantly higher in both measured velocity and computed force, which suggests that motors can work cooperatively to attain higher transport forces and velocities. David A. Dewitt http://works.bepress.com/david_dewitt/16 http://works.bepress.com/david_dewitt/16 Thu, 28 May 2009 10:58:46 PDT Pathological lesions in the brains of patients with Alzheimer's disease (AD) are characterized by dense deposits of the protein ,B-amyloid. The link between the deposition of B-amyloid in senile plaques and AD-associated pathology is, at present, controversial since there have been conflicting reports on whether the 39- 43 amino acid B-amyloid sequence is toxic or trophic to neurons. In this report, we show that B-amyloid peptide when presented as an insoluble substrate which mimics its conformation in vivo can induce cortical glial cells in vitro and in vivo to locally deposit chondroitin sulfate containingproteoglycan. In vitro the proteoglycan-containing matrix deposited by glia on B-amyloid blocks the usual ability of the peptide to allow cortical neurons to adhere and grow. Chondroitin sulfate-containing proteoglycan was also found in senile plaques of human AD tissue. We suggest that an additional effect of B-amyloid in the brain, which compounds the direct effects of ,8- amyloid on neurons, is mediated by the stimulation of astroglia to become reactive. Once in the reactive state, glial cells deposit large amounts of growth-inhibitory molecules within the neuropil which could impair neuronal process survival and regeneration leading to neurite retraction and/or dystrophy around senile plaques in AD. David A. Dewitt http://works.bepress.com/david_dewitt/14 http://works.bepress.com/david_dewitt/14 Thu, 28 May 2009 10:58:45 PDT David A. Dewitt http://works.bepress.com/david_dewitt/15 http://works.bepress.com/david_dewitt/15 Thu, 28 May 2009 10:58:45 PDT Previously, we showed three differentially sulfated forms of chondroitin sulfate proteoglycans (CSPG) associated with senile plaques, astrocytes and neurofibrillary tangles in Alzheimer's disease. Here, monoclonal antibodies were used to demonstrate CSPGs in other neurodegenerative diseases. CSPGs were found associated with inclusions of Parkinson's, diffuse Lewy body, Pick's diseases, and progressive supranuclear palsy. Reacting astrocytes in each of these neurodegenrative diseases and Huntington's disease showed immunoreactivity for CSPG. CSPG distribution in a variety of neurodegenerative diseases suggests that similar mechanisms may be involved in the accumulation of proteoglycans in a number of filamentous inclusions. David A. Dewitt http://works.bepress.com/david_dewitt/13 http://works.bepress.com/david_dewitt/13 Thu, 28 May 2009 10:58:44 PDT Chondroitin sulfate proteoglycans (CSPG) are extracellular matrix proteins inhibitory to neurite outgrowth in vitro and correlated with decreased neurite outgrowth after CNS injury. Previously, heparan sulfate proteoglycan and dermatan sulfate proteoglycan have been shown to be associated with senile plaques (SPs) and neurofibrillary tangles (NFTs) but CSPG was not. In an immunocytochemical study, three monoclonal antibodies to different sulfation states of the chondroitin glycosaminoglycan were used to localize CSPG in cases of Alzheimer's disease. Chondroitin 4-sulfate was found in both SPs and NFTs. An antibody to unsulfated chondroitin strongly immunostained intracellular NFTs and the dystrophic neurites of SPs. Chondroitin 6-sulfate was found in NFTs and the area around SPs. These results suggest that CSPG, in addition or as an alternative to B-amyloid protein, could be responsible for the regression of neurites around senile plaques in Alzheimer's disease. David A. Dewitt