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Biomedical subjects

W R Woodward

Publications and source records attributed to W R Woodward.

At least 19 recordsLinked to original sources
PubMed2001

Beta-amyloid plaques induce neuritic dystrophy of nitric oxide-producing neurons in a transgenic mouse model of Alzheimer's disease.

A causative role for nitric oxide has been postulated in a number of neurodegenerative diseases. Using histochemical and immunohistochemical methods, we examined the effect of beta-amyloid plaques on nitric oxide-producing cells in transgenic mice which overexpress a mutant human amyloid precursor protein (APP). In 14-month-old animals, nitric oxide synthase (NOS)-positive dystrophic neurites were observed frequently in the cerebral cortex and hippocampus of all of 16 plaque-bearing transgenic animals and in none of 16 wild-type animals. Double labeling of NOS and beta-amyloid revealed that 90% of beta-amyloid plaques were associated with NOS-containing dystrophic neurites. In 7-month-old animals, beta-amyloid plaques were very rare, but those present were frequently associated with NOS-positive neuritic dystrophy. We conclude that beta-amyloid plaques induce neuritic dystrophy in cortical neurons containing NOS in this model of AD, and hypothesize that this finding may be relevant to the mechanism of beta-amyloid neurotoxicity in human AD.

Alzheimer Disease↗
PubMed1999

Effects of dystrophin isoforms on signal transduction through neural retina: genotype-phenotype analysis of duchenne muscular dystrophy mouse mutants.

Duchenne and Becker muscular dystrophy patients have mutations in the dystrophin gene. Most show reduced b-wave amplitudes in the dark-adapted electroretinogram (ERG). We studied normal C57BL/6J mice and five X-linked muscular dystrophy strains with different dystrophin mutations to determine whether the location of the mutation within the gene affects the mouse ERG and to correlate such effects with dystrophin isoform expression. Amplitudes and implicit times were measured for a-waves, b-waves, and digitally filtered oscillatory potentials. mdx and mdxCv5 mice, with mutations near the amino terminus and lacking expression of Dp427, had ERGs similar to those of C57BL/6J mice. mdxCv2 and mdxCv4 mice, with mutations in the center of dystrophin and who do not express isoforms Dp427, Dp260, or Dp140 (mdxCv4), had increased b-wave and oscillatory potential implicit times. mdxCv3 mice, with a mutation near the carboxy terminus resulting in deficiency of all dystrophin isoforms, had increased b-wave and oscillatory potential implicit times and reduced scotopic b-wave amplitudes. Fitting the a-wave data to a transduction activation phase mathematical model showed normal responses for all phenotypes, suggesting that the b-wave delays are due to defects beyond the rod outer segment, most likely at the rod to on-bipolar cell synapse. The variation in the ERG phenotype with the position of the dystrophin gene mutation suggests that there are different contributions by each isoform to retinal electrophysiology. Although Dp427 and Dp140 isoforms do not appear to be important contributors to the ERG, lack of Dp260 and possibly Dp71 isoforms is associated with an abnormal ERG.

Animals↗
PubMed1997

Short- and long-duration responses to levodopa during the first year of levodopa therapy.

We examined the response to 2-hour levodopa infusions in 18 Parkinson's disease subjects before starting long-term levodopa treatment and after 6 and 12 months of treatment using tapping speed as an index of bradykinesia. The long-duration response (LDR), measured as the increase in baseline (overnight without levodopa) tapping speed, increased by 29 +/- 18 at 6 months and by 35 +/- 24 at 12 months. The magnitude of the short-duration response (SDR) to a 2-hour levodopa infusion after an overnight levodopa withdrawal did not differ at 6 and 12 months (16 +/- 8 and 20 +/- 13 taps/min) from that before long-term levodopa (21 +/- taps/min). However, when levodopa was withheld for 3 days, it was evident that the SDR magnitude was increasing in magnitude (19, 23, and 31 taps/min at 0, 6, and 12 months). Duration of SDR did not change. A diurnal motor pattern with faster tapping speeds in the morning and slower in the evening was apparent on the days no levodopa was administered. These observations indicate (1) the LDR is responsible for much of the sustained response to levodopa during the first year of treatment, (2) the SDR magnitude increases but is obscured by the LDR, and (3) a diurnal pattern of motor function is present that may be partially responsible for the poorer motor function in the afternoons and evenings.

Adult↗
PubMed1997

Motor fluctuations during continuous levodopa infusions in patients with Parkinson's disease.

The cause of motor fluctuations occurring during constant-rate levodopa infusions is unknown. We examined whether known pharmacokinetic factors could explain the fluctuations and looked for clues to pharmacodynamic causes. Eleven subjects with stage III-V Parkinson's disease (PD) and a fluctuating response to levodopa underwent constant-rate infusions for 36-110 h. Levodopa, 3-O-methyldopa (3-OMD), and plasma large neutral amino acids (LNAAs) were measured at 2- to 6-h intervals and PD was monitored hourly from 07:00 to 22:00 h with tapping speed. Ten subjects had motor fluctuations during the infusions. Zero to 68% of the variability of tapping speed could be explained by variation in plasma LNAA concentrations in individual subjects. Fluctuations occurred more commonly later in the day, which may be related to the tendency for LNAAs to increase during the day. Motor fluctuations were not associated with minor variations in levodopa or 3-OMD concentrations. Fluctuations during constant infusions were more marked in patients using larger daily doses of oral levodopa; severity of PD did not predict fluctuations during the infusions. There was no trend for fluctuations or dyskinesia to decrease or increase during several days of constant-rate levodopa infusion. A portion of motor fluctuations occurring during constant levodopa infusions can be explained by peripheral pharmacokinetic mechanisms. Fluctuations are more prominent in subjects who have taken larger daily doses of levodopa, implicating pharmacodynamic factors as well.

Adult↗
PubMed1996

Characterization and distribution of basic fibroblast growth factor-containing cells in the rat hippocampus.

Basic fibroblast growth factor (bFGF), a member of the heparin-binding growth factor family, is present in relatively high levels in the brain where it may play an important role in the maintenance, repair, and reorganization of the tissue. Although bFGF is associated mainly with astrocytes throughout most of the central nervous system (CNS), a narrow but prominent band of pyramidal neurons, which coincides with the CA2 subregion of Ammon's horn in the hippocampus, stains intensely for bFGF. In order to gain an understanding of which cells express bFGF and whether or not BFGF is a good marker for CA2 neurons, we have used a mouse monoclonal antibody directed against recombinant human bFGF to characterize the distribution and localization of bFGF expression in the hippocampus. We find that about one-quarter of the neurons in CA2 are bFGF positive, and they appear smaller and have more irregular-shaped nuclei than their unstained counterparts. In addition, all glial fibrilary acidic protein (GFAP)-positive astrocytes in the hippocampus stain for bFGF, and the distribution of these astrocytes is heterogeneous in the hippocampus. Finally, in both astrocytes and CA2 pyramidal neurons, bFGF immunoreactivity is localized primarily in the nucleus and to a lesser extent in the cytoplasm and processes of stained cells.

Animals↗
PubMed1996

Apomorphine tolerance in Parkinson's disease: lack of a dose effect.

The development of tolerance to dopaminergic drugs may be important in the long-term therapy of Parkinson's disease. In this study, we sought to determine whether tolerance developed during infusions of apomorphine and if there was evidence of any dose dependency. Eight patients with Parkinson's disease received 4- to 6-h infusions of apomorphine at low, medium, and high rates on consecutive days. Before and after each infusion, test boluses of apomorphine were administered to measure sensitivity to the drug. The duration of motor effects after the postinfusion boluses were reduced in comparison to those of the preinfusion boluses, indicating that tolerance developed during the infusions. The infusion rate did not affect the responses to the postinfusion test boluses. Our observations indicate that tolerance develops to the antiparkinsonian effect of apomorphine after several hours of its constant infusion, but is not influenced by the dose of drug administered.

Antiparkinson Agents↗
PubMed1995

Developmental time course of acidic and basic fibroblast growth factors' expression in distinct cellular populations of the rat central nervous system.

Acidic and basic fibroblast growth factors (aFGF and bFGF, respectively) are expressed in high levels in adult central nervous system (CNS). We report the time course of developmental appearance and distribution of these factors and of two FGF receptors, FGFR-1 and FGFR-2, in the CNS of rats ranging in age from embryonic day 16 to adult. Immunohistochemical analysis showed that sensory neurons in the midbrain were the first cells to contain detectable aFGF immunoreactivity at embryonic day 18. The next cell group to contain aFGF were motor neurons, which were found to be aFGF-positive at the day of birth. A number of other subcortical neuronal populations were observed to contain aFGF immunoreactivity after postnatal day 7. Adult levels and distribution patterns of aFGF were reached in all CNS areas by postnatal day 28. Basic FGF immunoreactivity was observed at postnatal day 0 in neurons in the CA2 subfield of hippocampus. Astrocytes contained detectable bFGF immunoreactivity, starting at postnatal day 7. Adult levels and patterns of distribution of bFGF were reached in all CNS areas by postnatal day 28. These immunohistochemical observations were confirmed by using bioassay and Western blot techniques. FGFR-1 and FGFR-2 mRNA were expressed in significant levels in all CNS areas at all time points analyzed. The observation that aFGF and bFGF appear in specific and distinct cellular populations at relatively late developmental times suggests that these FGFs may be involved in specific mechanisms of CNS maturation, maintenance, and repair.

Animals↗
PubMed1995

Progressive hippocampal loss of immunoreactive GLUT3, the neuron-specific glucose transporter, after global forebrain ischemia in the rat.

Brain damage after global forebrain ischemia is worsened by prior hyperglycemia and ameliorated by antecedent hypoglycemia. To assess whether GLUT3, the neuron specific glucose transporter and its mRNA, are affected by cerebral ischemia, we investigated the hippocampal pattern of GLUT3 immunoreactivity and GLUT3 gene expression 1, 4 and 7 days after global forebrain ischemia in a rat 2-vessel occlusion model. We used a newly generated, specific, C-terminally directed polyclonal antiserum against GLUT3 to stain coronal frozen sections. Thionin staining and the microglial marker, OX42, indicated the extent of ischemic damage in hippocampus and correlated with GLUT3 loss. One day after ischemia, no significant change in hippocampal GLUT3 immunoreactivity was observed; by 4 days however, there was consistent and pronounced loss; and at 7 days the loss of GLUT3 staining was maximal. The greatest loss of GLUT3 staining was in the CA1 region, especially the strata oriens and radiatum of Ammon's horn. By contrast, GLUT3 staining was undiminished in the stratum lacunosum moleculare, in the mossy fibers of the lateral aspect of CA3 and in all but the inner-most portion of the molecular layer of the dentate gyrus, immediately adjacent to the granule cells. GLUT3 mRNA levels were not significantly altered at 24 hours and significantly declined at 4 and 7 days after ischemia in the CA1 pyramidal layer. These data are consistent with the pattern of neuronal loss and microglial activation in hippocampus. Loss of GLUT3 may affect the availability of glucose, and possibly the viability of ischemically damaged neurons.

Animals↗
PubMed1995

Apomorphine infusional therapy in Parkinson's disease: clinical utility and lack of tolerance.

We assessed the clinical utility of apomorphine infusional therapy in patients with parkinsonism and motor fluctuations and sought evidence for alterations in drug response resulting from chronic treatment. Six patients with Parkinson's disease were treated for 3 months with s.c. infusions of apomorphine administered during waking hours. At the beginning and the end of the study, test doses of apomorphine (12.5-100 micrograms/kg) were administered to establish a dose-response curve. Over the study, the patients reported a significant improvement in the number of "on" hours experienced per day and substantially reduced the dose and frequency of levodopa and other antiparkinsonian medications. No average change in apomorphine dose-response relationships or pharmacokinetics was observed during the study. However, two patients lowered the infusion rate during the 3-month observation and exhibited higher drug levels and longer responses following test doses of apomorphine given at the end of the study. Although pragmatic concerns with the use of infusion pumps solutions and adverse effects limited the overall benefit afforded by the treatment, this kind of drug treatment may be useful in selected patients with severe parkinsonism and fluctuations.

Administration, Cutaneous↗
PubMed1995

Long-duration response to levodopa.

We measured the long-duration response to levodopa by changes in tapping rate in 16 patients with Parkinson's disease undergoing 3 to 5 days of levodopa withdrawal. "Off" tapping rates deteriorated 22% over the course of this holiday, the decline beginning 24 hours after levodopa withdrawal. Deterioration was more pronounced in the more affected hand in asymmetrically affected patients. A 2-hour infusion of levodopa after the levodopa holiday did not restore the long-duration response, although it produced a greater short-duration response than before the holiday. These observations indicate that the long-duration response is an important component of the therapeutic benefit of levodopa and is separable from the short-duration response.

Female↗
PubMed1995

mdxCv3 mouse is a model for electroretinography of Duchenne/Becker muscular dystrophy.

PURPOSE: To identify an animal model for the abnormal scotopic electroretinogram found in a majority of Duchenne and Becker muscular dystrophy patients. METHODS: Ganzfeld electroretinograms were recorded in dark-adapted normal C57BL/6 mice, and two strains of mice with different X-linked muscular dystrophy mutations (mdx and mdxCv3). Responses for the right eye were averaged and the amplitudes and implicit times of the a-wave and b-wave were measured. The electroretinogram was digitally filtered to extract the oscillatory potentials. Statistical analyses included one-way analysis of variance and the Scheffé S test. RESULTS: While the electroretinogram in mdx was normal, in mdxCv3 the scotopic b-wave was markedly reduced and the oscillatory potentials were delayed, similar to changes observed in Duchenne and Becker muscular dystrophy patients. Some of the mdxCv3 animals demonstrated negative configuration electroretinograms, with the b-wave amplitude reduced compared to that of the a-wave. CONCLUSIONS: Abnormalities found in the electroretinograms of Duchenne and Becker muscular dystrophy patients led to the identification of dystrophin in human retina and the discovery that dystrophin is required for normal retinal electrophysiology. These results indicate that mdxCv3 is a model for elucidating the role of dystrophin in retina and suggest that dystrophin isoforms, consisting of only the C-terminal domains of the full-length protein, may be important to the development of normal retinal electrical potentials.

Animals↗
PubMed1994

Immunohistochemical localization of the neuron-specific glucose transporter (GLUT3) to neuropil in adult rat brain.

The precise histologic localization of GLUT3, a glucose transporter thought to be restricted to neurons, is unknown. Using a high-affinity, specific antiserum against rodent GLUT3 for immunocytochemistry, light microscopic staining concentrates heterogeneously in the neuropil in a region- and lamina-specific manner; intense staining characterizes areas with high rates of glucose utilization such as inferior colliculus and pyriform cortex. Neuropil localization with little perikaryal staining suggests that GLUT3 may provide the energy needed locally for synaptic transmission.

Animals↗
PubMed1994

Cellular distribution, subcellular localization and possible functions of basic and acidic fibroblast growth factors.

The distribution in the rat nervous system of acidic and basic fibroblast growth factors (FGFs) was analysed by a combination of biochemical and anatomical methods. Acidic FGF (aFGF) was found to be present exclusively in specific neuronal populations, such as motor neurons and basal forebrain cholinergic neurons. Basic FGF (bFGF) was found in astrocytes and in neurons in hippocampal area CA2. Within labelled astrocytes and CA2-neurons, bFGF was detected in both the cytoplasm and the nucleus. The levels of intracellular bFGF were manipulated by antisense oligonucleotide treatment of cultures of developing neural crest cells. Results indicated that the amount of melanogenesis in the cultures is likely to be regulated by intracellular, possibly nuclear bFGF.

Animals↗
PubMed1994

Controlled release levodopa/carbidopa 25/100 (Sinemet CR 25/100): pharmacokinetics and clinical efficacy in untreated parkinsonian patients.

The pharmacokinetics of the clinically determined optimal dose of controlled release levodopa/carbidopa 25/100 (Sinemet CR 25/100) after 12 weeks of therapy was studied in nine parkinsonian patients without prior exposure to levodopa. The pharmacokinetics of single oral doses of controlled release levodopa/carbidopa 25/100 and 50/200 were also compared. As predicted from the plasma half-life (1.7 +/- 0.3 h) and confirmed by morning trough levels, levodopa did not accumulate when controlled released levodopa/carbidopa 25/100 was administered twice daily. The absorption and bioavailability of CR 25/100 are minimally greater than CR 50/200. Controlled released levodopa/carbidopa 25/100 levodopa plasma levels peak slightly faster than controlled release levodopa/carbidopa 50/200.

Absorption↗
PubMed1994

Effect of peripheral catechol-O-methyltransferase inhibition on the pharmacokinetics and pharmacodynamics of levodopa in parkinsonian patients.

Catechol-O-methyltransferase (COMT) metabolizes a portion of administered levodopa and thus makes it unavailable for conversion to dopamine in the brain. In an open-label trail, we examined the effects of entacapone, a peripheral inhibitor of COMT, administered acutely or for 8 weeks, on the pharmacokinetics and pharmacodynamics of levodopa in 15 parkinsonian subjects with a fluctuating response to levodopa. Acutely and chronically administered entacapone similarly decreased the plasma elimination of orally and intravenously administered levodopa. Absorption of levodopa was minimally affected. During chronic entacapone treatment, daily levodopa dosages were reduced by 27% yet mean plasma levodopa concentrations were increased by 23%. Plasma 3-O-methyldopa concentrations were decreased by 60%. Entacapone increased the duration of action of single doses of levodopa by a mean of 56%. The percent of the day "on" after 8 weeks of entacapone treatment was 77%; it dropped to 44% upon withdrawal of entacapone. We conclude that inhibition of COMT by entacapone increases the plasma half-life of levodopa and augments the antiparkinsonian effects of single and repeated doses of levodopa.

Aged↗
PubMed1994

Effect of brief levodopa holidays on the short-duration response to levodopa: evidence for tolerance to the antiparkinsonian effects.

To determine whether tolerance to the antiparkinsonian actions of levodopa develops during longterm levodopa therapy, we compared the response to 2-hour levodopa infusions before and after 2- to 4-day levodopa holidays using tapping and walking speeds and tremor/dyskinesia scores as measures of response in 17 parkinsonian patients with a fluctuating response to levodopa. As expected, motor function deteriorated during the levodopa holiday, but the maximum motor tapping and walking speeds and dyskinesia scores produced by the levodopa infusion before the holiday were the same as those produced by the infusion after the holiday. Because the baseline motor function was lower after the holiday, the increment in tapping and walking speeds (ie, the difference between the baseline and the maximum response) was larger with the postholiday infusion (p < 0.01). The postholiday infusion produced a longer response than did the preholiday infusion as measured by tapping score (p = 0.047), walking speed (p = 0.02), and tremor or dyskinesia scores (p = 0.02). The prolongation of the response was greater in patients receiving larger daily doses of levodopa (r = 0.55; p = 0.03). These changes in the duration of response suggest that progressive shortening of the response to levodopa during long-term therapy is partially caused by development of tolerance to levodopa and not just by loss of dopamine storage sites. Tolerance to levodopa should be considered in establishing oral dosing regimens and in developing new strategies for drug delivery.

Adult↗