David A DeWitt Ph.D.

Glial Cell Extracellular Matrix in Alzheimer’s Disease

David A. DeWitt et al. — 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.

Theories of the Origin and Early Evolution of Life

David A. DeWitt — 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.

Impact of a Young-Earth Creationist Apologetics Course on Student Creation Worldview

Tom Henderson et al. — 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.

The Words of the Lord is Flawless

David A. DeWitt — Mon, 15 Jun 2009 06:14:00 PDT

Role of Educational Factors on College Students’ Creation Worldview

David A. Dewitt et al. — 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.

Force-Velocity Curves of Motor Proteins Cooperating In Vivo

David A. Dewitt et al. — 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.

B-Amyloid of Alzheimer's Disease Induces Reactive Gliosis that Inhibits Axonal Outgrowth

David A. Dewitt et al. — 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.

Review: Refuting Compromise

David A. Dewitt — Thu, 28 May 2009 10:58:45 PDT

Chondroitin sulfate proteoglycans are a common component of neuronal inclusions and astrocytic reaction in neurodegenerative diseases

David A. Dewitt et al. — 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.

Chondroitin Sulfate Proteoglycans Are Associated with the Lesions of Alzheimer's Disease

David A. Dewitt et al. — 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.

Peri-nuclear clustering of mitochondria is triggered during aluminum maltolate induced apoptosis

David A. Dewitt et al. — Mon, 25 May 2009 10:11:08 PDT

Synapse loss and neuronal death are key features of Alzheimer’s disease pathology. Disrupted axonal transport of mitochondria is a potential mechanism that could contribute to both. As the major producer of ATP in the cell, transport of mitochondria to the synapse is required for synapse maintenance. However, mitochondria also play an important role in the regulation of apoptosis. Investigation of aluminum (Al) maltolate induced apoptosis in human NT2 cells led us to explore the relationship between apoptosis related changes and the disruption of mitochondrial transport. Similar to that observed with tau over expression, NT2 cells exhibit peri-nuclear clustering of mitochondria following treatment with Al maltolate. Neuritic processes largely lacked mitochondria, except in axonal swellings. Similar, but more rapid results were observed following staurosporine administration, indicating that the clustering effect was not specific to Al maltolate. Organelle clustering and transport disruption preceded apoptosis. Incubation with the caspase inhibitor zVAD-FMK effectively blocked apoptosis, however failed to prevent organelle clustering. Thus, transport disruption is associated with the initiation, but not necessarily the completion of apoptosis. These results, together with observed transport defects and apoptosis related changes in Alzheimer disease brain suggest that mitochondrial transport disruption may play a significant role in synapse loss and thus the pathogenesis or Alzheimer’s disease.

Aluminum Maltolate-Induced Toxicity in NT2 Cells Occurs Through Apoptosis and Includes Cytochrome c Release

David A. Dewitt et al. — Mon, 25 May 2009 10:11:08 PDT

Aluminum (Al) compounds are neurotoxic and have been shown to induce experimental neurodegeneration although the mechanism of this effect is unclear. In order to study this neurotoxic effect of Al, we have developed an in vitro model system using Al maltolate and human NT2 cells. Al maltolate at 500 mM caused significant cell death with a 24-h incubation and this toxicity was even more evident after 48 h. Lower doses of Al maltolate were also effective, but required a longer incubation for cell death. Nuclear fragmentation suggestive of apoptosis was observed as early as three hours and increased substantially through 24 h. Chromatin condensation and nuclear fragmentation were confirmed by electron microscopy. In addition, TUNEL positive nuclei were also observed. The release of cytochrome c was demonstrated with Western blot analysis. This in vitro model using human cells adds to our understanding of Al neurotoxicity and could provide insight into the neurodegenerative processes in human disease.

AB(1-42) and aluminum induce stress in the endoplasmic reticulum in rabbit hippocampus, involving nuclear translocation of gadd 153 and NF-kB

David A. Dewitt — Mon, 25 May 2009 10:11:07 PDT

Apoptosis may represent a prominent form of neuronal death in chronic neurodegenerative disorders, such as Alzheimer’s disease. Although apoptosis under mitochondrial control has received considerable attention, mechanisms used within the endoplasmic reticulum (ER) and nucleus in mediating apoptotic signals are not well understood. A growing body of evidence is emerging from different studies which suggests an active role for the ER in regulating apoptosis. Disturbances of ER function have been shown to trigger two different apoptotic pathways; one involves cross-talk with mitochondria and is regulated by the antiapoptotic Bcl-2, and the second is characterized by the activation of caspase-12. Also, stress in the ER has been suggested to result in the activation of a number of proteins, such as gadd 153 and NF-k, and in the downregulation of the antiapoptotic protein, Bcl-2. In the present study, the intracisternal injection in aged rabbits of either the neurotoxin aluminum maltolate or of Ab(1-42), has been found to induce nuclear translocation of gadd 153 and the inducible transcription factor, NF-kB. Translocation of these two proteins is accompanied by decreased levels of Bcl-2 in both the ER and the nucleus. Aluminum maltolate, but not Ab, induces caspase-12 activation which is a mediator of ER-specific apoptosis; this is the first report of the in vivo activation of caspase-12. These findings indicate that the ER may play a role in regulating apoptosis in vivo, and could be of significance in the pathology of neurodegeneration and related disorders.

Senile Plaques and Neurofibrillary Tangles: The Concurrent Lesions of Alzheimer’s Disease

David A. Dewitt et al. — Mon, 25 May 2009 10:11:07 PDT

Immunocytochemical Evidence that the B-Protein Precursor is an Integral Component of Neurofibrillary Tangles of Alzheimer's Disease

David A. Dewitt — Mon, 25 May 2009 10:11:07 PDT

Amyloid B (AB) immunoreactivity has been demonstrated in all extracellular neurofibrillary tangles (E-NFT) and most intraneuronal neurofibrillary tangles (I-NF. We undertook this immunocytochemical study to understand the relationship between AB immunoreactivity localized in NFT and B-protein precursor (BPP). We found epitopes of amino-, mid-, and carboxyl-terminal domains of BPP in I-NFT and the majority of ENFT. NFT retained (BPP after ionic detergent extraction, demonstrating that BPP is an integral component of NFT. Finding BPP in regions of AB immunoreactivity raises the possibility that BPP or its fragments associate with amyloid, and that the stability of AB is responsible for its dominance in amyloid deposits.

Effects of a History of Life Course on Student Views of Science

Steve W. Deckard et al. — Mon, 25 May 2009 10:11:06 PDT

Regenerative Failure: A Potential Mechanism for Neuritic Dystrophy in Alzheimer’s Disease

David A. Dewitt et al. — Mon, 25 May 2009 10:11:06 PDT

Although neuronal pathology and synaptic loss are salient features of Alzheimer’s disease (AD), the underlying mechanisms involved are unknown. Using double-immunolabeled preparations, we found that both the density and the total lengths of axons are decreased within the AB-containing area of senile plaques (SP) in comparison with the adjacent neuropil. These observations suggest that axotomy is occurring in the vicinity of the SP which could account for the synaptic loss. Since AB in solution has been shown to be neurotoxic in vitro, we tested whether intact SP cores isolated from AD brain were equally detrimental when presented to retinal ganglion neurons. Surprisingly, SPs did not appear to be toxic or even repulsive to neurons since they adhered well and elaborated axons which wrapped tightly around the SP core. In the presence of cortical astrocytes, however, neurons appeared to avoid SP cores. We found that astrocytes accumulate and deposit chondroitin sulfate proteoglycans (CSPGs) around SP cores in vitro in a pattern similar to that observed around SPs in Alzheimer’s disease brain. Neuronal avoidance of astrocyte-conditioned SP cores could be due to the axon outgrowth inhibitory nature of CSPGs. These results suggest that astrocytic reaction to SPs, including increased CSPGs, may facilitate the decreased axon density and synaptic loss in AD brain. Moreover, the similarities between swollen axon endings following axotomy in trauma and the dystrophic neurites of the SP suggest that dystrophic neurites in AD may be exhibiting regenerative failure rather than aberrant sprouting.

Direct Comparison of Worldview Learning Outcomes in Resident versus DLP Creation Studies Course

David A. DeWitt Ph.D. — Mon, 25 May 2009 10:11:05 PDT

Are there differences in worldview learning outcomes between students in a residential vs. a DLP format course? We have conducted pre and post test assessment of student beliefs about creation before and after completing the CRST 290 History of Life course. Come and see the surprising results!

Astrocytes Regulate Microglial Phagocytosis of Senile Plaque Cores of Alzheimer’s Disease

David A. Dewitt et al. — Mon, 25 May 2009 10:11:05 PDT

We have developed an in vitro model in which isolated senile plaque (SP) cores are presented to rat microglial cells in culture. Microglia rapidly phagocytosed, broke apart, and cleared SP cores. However, when cocultured with astrocytes, microglial phagocytosis was markedly suppressed, allowing the SPs to persist. Suppression of phagocytosis by astrocytes appears to be a general phenomena since microglia in the presence of astrocytes showed reduced capacity to phagocytose latex beads as well. The astrocyte effect on microglia is related in part to a diffusible factor(s) since astrocyte- but not fibroblast-conditioned media also reduced phagocytosis. These results suggest that while microglia have the capacity to phagocytose and remove SPs, astrocytes which lie in close association to microglia may help prevent the efficient clearance of SP material allowing them to persist in Alzheimer’s disease.

Involvement of complex carbohydrate chemistry in Alzheimer’s disease

David A. Dewitt et al. — Mon, 25 May 2009 10:11:04 PDT

The cardinal feature of Alzheimer disease is the extracellular deposition of proteinaceous amyloid-β fibrils as senile plaques. Amyloid-β plays an essential role in disease diagnosis and is also thought by many to be a key mediator of disease pathogenesis. As such, there are tremendous efforts underway to understand mechanisms of amyloid deposition. In this context, it is notable that the actual term amyloid, represents a historical misnomer (being derived from amylose, i.e., starch) and since this realization, the contribution of carbohydrates in disease pathogenesis has largely been ignored. However, recently, two emerging lines of evidence indicate not only that the interaction of carbohydrates with amyloid is a key event in disease pathogenesis but also that therapeutic efforts targeted towards such pathways may prove therapeutically efficacious. First, just over a decade ago, we and others discovered that oxidative glycation, similar if not identical to that found in diabetes, was an early and chronic contributor to the disease. Second, we very recently found evidence for the presence of chitin-like polysaccharides in association with amyloid deposits in the diseased brain. Both carbohydrate-associated changes likely contribute to the physiochemical properties of amyloid (and other disease-related proteins such as tau) and, as such, to the insolubility and protease-resistance of amyloid. In fact, taken together, the findings indicate an emerging and important role for carbohydrates in the pathogenesis of Alzheimer disease.