Biomedical subjects

D L Price

Publications and source records attributed to D L Price.

At least 109 records · Page 6Linked to original sources

PubMed1995

Effects of extracts of fiberglass insulations on the growth of Aspergillus fumigatus and A. versicolor.

Water extracts of thermal and acoustic fiberglass insulations used in the duct work of heating, ventilation and air conditioning (HVAC) systems supported germination of conidia and growth of Aspergillus versicolor (Vuillemin) Tiraboschi 1908-9 and Aspergillus fumigatus Fresenius 1863. Urea, formaldehyde and unidentified organics were detected in the extracts. Formaldehyde in concentrations similar to those found in the extracts restricted the growth of both species in enriched media. A. versicolor, the more common species associated with fiberglass insulations, was more resistant to formaldehyde than A. fumigatus.

Aspergillus↗

PubMed1995

Fungal colonization of synthetic substrates for use in space craft.

Materials being used or considered for use in space flights were examined for their susceptibility to fungal colonization. The materials included soft goods (clothing) and insulation and fabrication products such as Velcro attachments and elastic cord binders. Materials were exposed for at least 28 days in a high-humidity chamber colonized with over 50 species of fungi, including those species recommended for determining recalcitrance of materials to fungal biodegradation. At least nine of 25 products demonstrated extensive microscopic colonization by fungi, mostly by Acremonium obclavatum. Challenge procedures that rely on observations with the unaided eye, or 40 x magnification of growth by a restricted number of fungal species with a cellulosic substrate as a positive control, are insufficient for determining the resistance of synthetic substrates to fungal colonization.

Construction Materials↗

PubMed1995

The AMPA glutamate receptor GluR3 is enriched in oxytocinergic magnocellular neurons and is localized at synapses.

The cellular localization of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate glutamate receptor, GluR3, was identified using antibodies that recognize the N-terminus of the predicted polypeptide sequence of GluR3. Regional immunoblot analysis of monkey brain homogenates identified a protein of approximately 102,000 mol. wt that was enriched in hypothalamus. Immunocytochemistry demonstrated that GluR3 was enriched within the hypothalamic magnocellular neurosecretory nuclei and axons of the hypothalamo-neurohypophysial tract in rat and monkey. GluR3 immunoreactivity co-localized to oxytocin-containing, but not vasopressin-containing, neurons of the hypothalamic paraventricular nucleus, supraoptic nucleus and accessory magnocellular nuclei. Ultrastructurally, GluR3 immunoreactivity was enriched throughout cytoplasm of the somatodendritic compartment and was associated with postsynaptic and presynaptic structures. GluR3 immunoreactivity was frequently observed to be clustered at the plasma membrane of the somatodendritic compartment, consistent with the predicted localization of a membrane-bound ion channel. Additionally, GluR3-immunoreactive axon terminals in synaptic contact with unlabeled dendrites within the retrochiasmatic area and bed nucleus of the stria terminalis were observed, providing morphological evidence for a presynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor. By immunoblot analysis and immunocytochemistry using antibodies directed against a specific alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor in rat and monkey brain, our findings suggest a highly selective hypothalamic distribution of the GluR3 subunit that may have functional significance in the glutamatergic regulation of oxytocinergic neurons.

Amino Acid Sequence↗

PubMed1995

An adverse property of a familial ALS-linked SOD1 mutation causes motor neuron disease characterized by vacuolar degeneration of mitochondria.

Mutations in Cu/Zn superoxide dismutase (SOD1) cause a subset of cases of familial amyotrophic lateral sclerosis. Four lines of mice accumulating one of these mutant proteins (G37R) develop severe, progressive motor neuron disease. At lower levels of mutant accumulation, pathology is restricted to lower motor neurons, whereas higher levels cause more severe abnormalities and affect a variety of other neuronal populations. The most obvious cellular abnormality is the presence in axons and dendrites of membrane-bounded vacuoles, which appear to be derived from degenerating mitochondria. Since multiple lines of mice expressing wild-type human SOD1 at similar and higher levels do not show disease, the disease in mice expressing the G37R mutant SOD1 must arise from the acquisition of an adverse property by the mutant enzyme, rather than elevation or loss of SOD1 activity.

Amyotrophic Lateral Sclerosis↗

PubMed1995

NGF-stimulated retrograde transport of trkA in the mammalian nervous system.

The present study was designed to clarify the in vivo function of trkA as an NGF receptor in mammalian neurons. Using the rat sciatic nerve as a model system, we examined whether trkA is retrogradely transported and whether transport is influenced by physiological manipulations. Following nerve ligation, trkA protein accumulates distal to the ligation site as shown by Western blot analysis. The distally accumulating trkA species were tyrosine phosphorylated. The trkA retrograde transport and phosphorylation were enhanced by injecting an excess of NGF in the footpad and were abolished by blocking endogenous NGF with specific antibodies. These results provide evidence that, upon NGF binding, trkA is internalized and retrogradely transported in a phosphorylated state, possibly together with the neurotrophin. Furthermore, our results suggest that trkA is a primary retrograde NGF signal in mammalian neurons in vivo.

Animals↗

PubMed1995

Role of the beta-amyloid protein in Alzheimer's disease.

A major histopathological hallmark of Alzheimer's disease (AD) is the presence of amyloid deposits in the parenchyma of the amygdala, hippocampus, and neocortex. The principal component of amyloid is the beta-amyloid protein (A beta), a 39-43 amino acid peptide composed of a portion of the transmembrane domain and the extracellular domain of the amyloid precursor protein (APP). APP occurs as several A beta-containing isoforms of 695, 751, and 770 amino acids, with the latter two APP containing a domain that shares structural and functional homologies with Kunitz serine protease inhibitors. In cultured cells, APP mature through the constitutive secretory pathway, and some cell surface-bound APP are cleaved by an enzyme, designated as alpha-secretase, within the A beta domain, an event that precludes A beta amyloidogenesis. Several studies have delineated two additional pathways of APP processing: first, an endosomal/lysosomal pathway generates a complex set of APP-related membrane-bound fragments, some of which contain the entire A beta sequence; and, second, by mechanisms which are not fully understood, A beta 1-40 is secreted into the conditioned medium in vitro and is present in cerebrospinal fluid in vivo. The intracellular sites of enzymes responsible for proteolytic cleavage at the NH2 and COOH termini of A beta, termed gamma- and beta-secretase, respectively, have not been identified. Finally, recent molecular genetic investigations have identified a variety of mutations in APP that segregate with early-onset familial AD and with hereditary cerebral hemorrhage with amyloid, Dutch type (HCHWA-D). Several of these mutations appear to influence APP processing and result in the production of higher levels or longer A beta-related peptides that are inherently more fibrillogenic. Although a variety of lines of evidence implicates APP/A beta in AD, the mechanisms by which A beta influences the biology and vulnerability of neural cells are not fully understood but are very active areas of investigation. This review focuses on the present state of our understanding of APP and A beta in the context of AD.

Alzheimer Disease↗

PubMed1995

Amyloid beta amyloidosis in Alzheimer's disease.

The presence of amyloid deposits in the parenchyma of the amygdala, hippocampus, and neocortex is a major histopathological hallmark of Alzheimer's disease. The principal component of amyloid is amyloid beta, a 39-43 amino acid peptide comprised of a portion of the transmembrane domain and the extracellular domain of the amyloid precursor proteins. Amyloid precursor proteins occur as several amyloid beta-containing isoforms of 695, 751, and 770 amino acids. In cultured cells, amyloid precursor proteins mature through the constitutive secretory pathway, and some cell-surface-bound amyloid precursor proteins are cleaved by an enzyme, designated as alpha-secretase, within the amyloid beta domain, an event that precludes amyloid beta amyloidogenesis. Two additional pathways of amyloid precursor protein processing include an endosomal/lysosomal pathway that generates a complex set of amyloid precursor protein-related membrane-bound fragments, some of which contain the entire amyloid beta sequence; and, by mechanisms not fully understood, secretion of amyloid beta 1-40 into the conditioned medium in vitro and its presence in cerebrospinal fluid in vivo. The intracellular sites of enzymes responsible for proteolytic cleavage at the amino- and carboxyl-termini of amyloid beta, termed gamma- and beta-secretase, respectively, have not been identified. Molecular genetic investigations have identified a variety of mutations in the amyloid precursor protein gene that segregate with early-onset familial Alzheimer's disease and with hereditary cerebral hemorrhage with amyloid, Dutch type. Several of these mutations appear to influence amyloid precursor protein processing and result in the production of higher levels or longer amyloid beta-related peptides that are inherently more fibrillogenic.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1995

Comparison of new and traditional methods for detection of senile plaques in Alzheimer's disease.

The pathologic diagnosis of Alzheimer's disease (AD) rests upon the identification of senile plaques and neurofibrillary tangles (NFT) in brain tissue. Methods for staining these structures vary in their sensitivity. Six different silver stains and immunocytochemistry for the beta-amyloid (A beta) peptide were compared for sensitivity in staining of plaques and tangles. For staining of plaques, the silver stains fell into two groups: one group stained primarily large, distorted neurites in classic plaques, and the other stained primarily fine, filamentous elements in diffuse plaques and at the periphery of classic plaques. Our recently developed "quick silver" method demonstrated the highest number of plaques. Sensitivity of NFT staining also varied considerably. The quick silver and Yamamoto-Hirano methods were best for staining both plaques and NFT.

Adolescent↗

PubMed1995

Distribution of an APP homolog, APLP2, in the mouse olfactory system: a potential role for APLP2 in axogenesis.

Deposition of beta-amyloid (A beta) in senile plaques is a major pathological characteristic of Alzheimer's disease. A beta is generated by proteolytic processing of amyloid precursor proteins (APP). APP is a member of a family of related polypeptides that includes amyloid precursor-like proteins APLP1 and APLP2. To examine the distribution of APLP2 in the nervous system, we generated antibodies specific for APLP2 and used these reagents in immunocytochemical and biochemical studies of the rodent nervous system. In this report, we document that in cortex and hippocampus, APLP2 is enriched in postsynaptic compartments. In the olfactory system, however, APLP2 is abundant in olfactory sensory axons, and axon terminals in glomeruli. Confocal microscopy revealed that APLP2 is present in both pre- and postsynaptic compartments in the olfactory bulb. Notably, mRNA encoding chondroitin sulfate glycosaminoglycan (CS GAG)-modified forms of APLP2 are enriched in the olfactory epithelium, relative to alternatively-spliced mRNA, encoding CS GAG-free forms of APLP2. In addition, we demonstrate that CS-modified APLP2 forms accumulate in the olfactory bulb. CS proteoglycans are known to play an important role in regulating cell migration and neuronal outgrowth. Since sensory neurons in the olfactory epithelium are in a state of continual turnover, axons of newly generated cells must establish synaptic connections with neurons in the olfactory bulb in adult life. The presence of APLP2 in olfactory sensory axons and glomeruli is consistent with the view that this protein may play an important role in axonal pathfinding and/or synaptogenesis.

Amyloid beta-Protein Precursor↗

PubMed1995

Cellular and molecular biology of Alzheimer's disease and animal models.

Extraordinary progress has been made in understanding the neuronal populations at risk in AD and some of the mechanisms of cytoskeletal pathology; however, most recent research has focused on the mechanisms of amyloidogenesis and the processing of APP and A beta in in vitro and in vivo systems, including aged nonhuman primates and transgenic mice. Over the next several years, we anticipate that transgenic mice recapitulating many of the features of AD will be produced and that these animals will be very useful for defining the etiologies of this disease, for delineating mechanisms of cell dysfunction and death, and for testing novel therapies. Finally, because several other genetic risk factors, including apoE and chromosome 19 and a locus on chromosome 14, have been identified, it is anticipated that future studies will focus on the role of the products of these genes on the cytoskeleton and APP processing, which will represent exciting and challenging new areas of research.

Aged↗

PubMed1995

Evidence for apoptotic cell death in Huntington disease and excitotoxic animal models.

Huntington disease (HD) is an inherited neurodegenerative disorder characterized by selective death of striatal medium spiny neurons. Intrastriatal injections of glutamate receptor agonists (excitotoxins) recapitulate some neuropathological features of this disorder. Although this model suggests that excitotoxic injury may be involved in HD, the exact mechanisms of cell death in HD and its models are unknown. The present study was designed to test the hypothesis that HD can develop via the activation of an apoptotic mechanism of cell death and to examine whether excitotoxic striatal lesions with quinolinic acid in rats represent accurate models of HD. To characterize cell death, we employed DNA electrophoresis, electron microscopy (EM), and the terminal transferase-mediated (TdT) deoxyuridine triphosphate (d-UTP)-biotin nick end labeling (TUNEL) method for the in situ detection of DNA strand breaks. In the neostriatum of individuals with HD, patterns of distribution of TUNEL-positive neurons and glia were reminiscent of those seen in apoptotic cell death during normal development of the nervous system; in the same areas, nonrandom DNA fragmentation was detected occasionally. Following excitotoxic injury of the rat striatum, internucleosomal DNA fragmentation (evidence of apoptosis) was seen at early time intervals and random DNA fragmentation (evidence of necrosis) at later time points. In addition, EM detected necrotic profiles of medium spiny neurons in the lesioned rats. In concert, these results suggest that apoptosis occurs in both HD and excitotoxic animal models and that apoptotic and necrotic mechanisms of neuronal death may occur simultaneously within individual dying cells in the excitotoxically injured brain. However, the distribution of dying neurons in the neostriatum, the degree of glial degeneration, and the involvement of striatofugal pathways are very different between HD and excitotoxically damaged striatum. The present study suggests that multiple methods should be employed for a proper characterization of neuronal cell death in vivo.

Adult↗

PubMed1995

Localization of superoxide dismutases in Alzheimer's disease and Down's syndrome neocortex and hippocampus.

Abnormalities in the cellular regulation and expression of antioxidant enzymes may have a role in mechanisms of central nervous system aging and neurodegeneration. We therefore examined, using isozyme-specific antibodies and immunohistochemistry, the localization of copper, zinc-superoxide dismutase and manganese-superoxide dismutase in the frontal and temporal neocortices and hippocampi of aged controls and individuals with Alzheimer's disease or Down's syndrome. Two different antibodies to copper, zinc-superoxide dismutase and one antibody to manganese-superoxide dismutase were evaluated by immunoblotting of homogenates of human brain before use in immunohistochemistry. The copper, zinc-superoxide dismutase antibodies recognized a single band of proteins at 16 kd. The manganese-superoxide dismutase antibody detected a single band of proteins at 25 kd. Immunohistochemically, copper, zinc-superoxide dismutase and manganese-superoxide dismutase immunoreactivities were localized predominantly to neocortical and hippocampal pyramidal neurons and scarcely seen in glial cells in controls. In Alzheimer's disease and Down's syndrome, the distributions and intensities of these two forms of superoxide dismutase immunoreactivities were different as compared with controls. Copper, zinc-superoxide dismutase was enriched in pyramidal neurons undergoing degeneration, whereas manganese-superoxide dismutase was more enriched in reactive astrocytes than in neurons. In senile plaques, copper, zinc-superoxide dismutase-positive globular structures were surrounded by astrocytes highly enriched in manganese-superoxide dismutase. By double label immunohistochemistry, some pyramidal neurons coexpressed superoxide dismutases and tau, and a few copper, zinc-superoxide dismutase-positive structures in senile plaques colocalized with tau. Amyloid cores, diffuse plaques, and microglia scarcely showed colocalization with superoxide dismutase-positive structures. The observed changes in the cellular localization of superoxide dismutases in neocortex and hippocampus in cases of Alzheimer's disease and Down's syndrome support a role for oxidative injury in neuronal degeneration and senile plaque formation. The differential localization of copper, zinc-superoxide dismutase and manganese-superoxide dismutase in cerebral sites of degeneration suggests that cellular responses to oxidative stress is antioxidant enzyme specific and cell type specific and that these two forms of superoxide dismutase may have different functions in antioxidant mechanisms.

Adult↗

PubMed1994

Superoxide dismutase 1 with mutations linked to familial amyotrophic lateral sclerosis possesses significant activity.

Familial amyotrophic lateral sclerosis (FALS) has been linked to mutations in the homodimeric enzyme Cu/Zn superoxide dismutase 1 (SOD1). Assay by transient expression in primate cells of six FALS mutant enzymes revealed a continuum of enzymatic activity bounded by the enzyme carrying the mutation Gly-85-->Arg, which was inactive, and mutant enzyme G37R carrying the Gly-37-->Arg change, which retained full specific activity but displayed a 2-fold reduction in polypeptide stability. The G37R mutant displayed similar properties in transformed lymphocytes from an individual heterozygous for the G37R and wild-type SOD1 genes; heterodimeric enzymes composed of mutant and wild-type subunits were detected, but there was no measurable diminution in the stability and activity of the wild-type subunits. Thus, for mutants such as G37R, either surprisingly modest losses in activity (involving only the mutant subunit) can yield motor neuron death, or alternatively, mutant SOD1 may acquire properties that injure motor neurons by one or more mechanisms unrelated to the metabolism of oxygen radicals.

Amino Acid Sequence↗

PubMed1994

Motor neurons in Onuf's nucleus and its rat homologues express the p75 nerve growth factor receptor: sexual dimorphism and regulation by axotomy.

The present study establishes that populations of neurons in the lumbosacral cord, which innervate pelvic striated muscles, express p75NGFR throughout their life spans. These neuronal groups comprise the Onuf's nucleus in humans and its principal rat homologues, dorsolateral (DL) and dorsomedial (DM) nuclei, as well as the cremasteric (CRE) nucleus. The p75NGFR in these neurons is localized in the rough endoplasmic reticulum, Golgi complex, and lysosomes. Almost all neurons that project to striated perineal muscles in the male rat express p75NGFR; very low levels of p75NGFR are detected in neurons that innervate perineal sphincters of the female. In the female rat, p75NGFR expression is masculinized with perinatal androgen treatment. In addition, the expression of p75NGFR in DM and DL neurons in the adult is up-regulated by injury (i.e., pudendal axotomy) but is not influenced by gonadectomy. The results of this study establish that neurons of Onuf's nucleus and its rat homologues differ from general somatic motor neurons in that they express p75NGFR from early postnatal life (i.e., when all motor neurons express p75NGFR) into the adult (when the former, but not the latter, express the receptor). In view of growing evidence for the role of neurotrophins in the physiology of motor neurons, the above differentiating feature between general somatic and sexually dimorphic motor neurons suggests that p75NGFR may be involved in motor neuron plasticity and may participate in mechanisms by which neurons can protect themselves from degenerative insults.

Androgens↗

PubMed1994

Rapid anterograde axonal transport of the cellular prion glycoprotein in the peripheral and central nervous systems.

In prion diseases, the cellular prion protein (PrPc), abundant in neurons, is converted posttranslationally into an amyloid-forming scrapie prion protein (PrPSc), which accumulates in white matter tracts and nerve terminals. The trafficking of PrPc in neurons was investigated in vivo by injecting [35S]methionine into the L4 and L5 dorsal root ganglia and the entorhinal cortices of adult rats and by tracing the movement of radiolabeled PrPc. In both paradigms, labeled 33-35-kDa PrPc was transported, within 4 h, to distal axons and nerve terminals cofractionating with proteins in the fast component. Future studies using these methods may allow us to determine whether PrPc is converted into PrpSc during axonal transport and whether PrPSc is transported in animals with prion diseases.

Animals↗

PubMed1994

Highly selective effects of nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 on intact and injured basal forebrain magnocellular neurons.

Cholinergic neurons of the basal nucleus complex (BNC) respond to nerve growth factor (NGF), the first member of a polypeptide gene family that also includes brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5). NGF, BDNF, and NT-3 are enriched in hippocampus. In addition, NGF and, more recently, BDNF have been shown to stimulate the cholinergic differentiation and enhance the survival of BNC cells in vitro. The present investigation was designed to test, in a comparative fashion, the in vivo effects of human recombinant NGF, BDNF, and NT-3 with confirmed activities in vitro on cholinergic and gamma-aminobutyric acid (GABA)-ergic BNC neurons. The specific questions asked were whether and, to what extent, biologically active recombinant neurotrophins stimulate the transmitter phenotypes of intact cholinergic and GABAergic neurons of the BNC, and whether, and to what extent, recombinant neurotrophins protect the transmitter phenotypes of axotomized cholinergic and GABAergic neurons of the BNC following complete transections of the fimbria-fornix (measured by ChAT enzyme activity and ChAT immunoreactivity and ChAT, p75NGFR, and GAD mRNA hybridization). Our results confirm the profound stimulatory and protective effects of recombinant NGF on the transmitter phenotype of cholinergic BNC neurons at the mRNA and protein levels. The effect of NGF on injured cholinergic neurons of the BNC is very specific and saturated at a dose of 20 micrograms/2 weeks. BDNF appeared to increase moderately p75NGFR expression in both intact and axotomized cholinergic neurons and to exert minor effects on some cholinergic markers (e.g., ChAT immunoreactivity). NT-3 had no effects on cholinergic neurons or the BNC. Moreover, NGF, BDNF, and NT-3 had no influence on GABAergic BNC neurons. Taken together, these results indicate that, despite their significant sequence homologies and their shared abundance in target fields of BNC neurons, NGF, BDNF, and NT-3 show striking differences in their efficacies as cholinergic trophic factors. GABAergic neurons of the BNC are resistant to neurotrophins. The results of the present investigation establish that NGF excels among neurotrophins as a trophic factor for intact and injured basal forebrain cholinergic neurons.

Animals↗

PubMed1994

Neurotrophin 4/5 is a trophic factor for mammalian facial motor neurons.

The survival of developing motor neurons depends on factors secreted from skeletal muscles and from cells within the central nervous system. Although several members of the nerve growth factor protein family [neurotrophins (NTs)] are able to maintain developing rat motor neurons in vitro, only the brain-derived neurotrophic factor has been shown to have significant effects on the survival of motor neurons in vivo. In the present study, we demonstrate that NT-4/5 also prevents injury-induced death of facial motor neurons in neonatal rats. Furthermore, facial motor neurons express a functional receptor for NT-4/5, whereas mRNA-encoding NT-4/5 can be detected in their environment throughout embryonic and postnatal life. Thus, both NT-4/5 and brain-derived neurotrophic factor may be physiological survival factors for facial motor neurons and may serve as therapeutic agents for motor neuron disease.

Animals↗

PubMed1994

Ventral root avulsion: an experimental model of death of adult motor neurons.

The present study proposes a reproducible model of experimental degeneration of adult motor neurons in the rat. Avulsion of ventral roots in the adult lumbar cord transects motor axons at the root exit and leads to retrograde cell death of 80% of motor neurons 2 weeks later; this result follows a series of retrograde changes, including chromatolysis, loss of transmitter phenotype, and accumulation of phosphorylated neurofilaments in perikarya. Glial cells recruited at the site of retrograde injury express both microglia-specific epitopes (as exemplified by OX-42 immunoreactivity) and macrophage-specific markers (e.g., ED-1 immunoreactivity). Macrophage-specific markers become particularly intense 7 days postaxotomy and provide additional evidence of active phagocytosis of injured neurons. Ventral root avulsion is a very useful model for assessing mechanisms of motor neuron death and testing the ability of trophic factors and other agents to preserve the phenotype and promote the survival of adult motor neurons in vivo.

Animals↗