An investigation into the proteolytic cleavage of Alzheimer amyloid precursor protein in PC-12 cells.
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Adrenal Gland Neoplasms↗
Biomedical subjects
D M Walsh
Publications and source records attributed to D M Walsh.
Aggregation of Alzheimer's peptides.
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Amino Acid Sequence↗
Effects of low intensity infrared laser irradiation upon conduction in the human median nerve in vivo.
The current investigation, for which ethical permission was obtained, was designed to assess the putative neurophysiological effects of low intensity (9.6 J/cm2) laser (830 nm) irradiation upon conduction latencies in the human median nerve in vivo. Antidromic nerve conduction studies were performed on the non-dominant arms of healthy human volunteers (n = 51), who were each assigned to one of a variety of laser, placebo or control groups under randomized, blinded conditions. Analysis of negative peak latency differences using analysis of variance showed small (approximately 0.4 ms) but significant increases in latencies as a result of direct laser irradiation, and, where two-site recording was used, distal to the site of irradiation. No such differences were seen in the other experimental groups. These results show that laser irradiation applied to intact skin at the parameters used here may produce a direct, localized effect upon conduction in underlying nerves.
Adult↗
Effects of the mutations Glu22 to Gln and Ala21 to Gly on the aggregation of a synthetic fragment of the Alzheimer's amyloid beta/A4 peptide.
We assessed the fibrillogenic properties of synthetic peptides corresponding to residues 13-26 of beta/A4 amyloid, containing either the normal sequence (beta 13 26) or the mutations Glu22 to Gln (beta 13-26Q22) and Ala21 to Gly (beta 13-26G21). The kinetics of aggregation were monitored at 37 degrees C and pH 7.4 by measuring the amount of peptide remaining in solution, using reverse-phase high performance liquid chromatography. Negative stain electron microscopy revealed that all of the peptides formed fibrils. However, beta 13-26Q22 showed greatly accelerated fibril formation compared to the other two. The results suggest that the Q22 mutation confers increased amyloidogenic properties on the beta/A4 peptide, whereas the G21 mutation acts by a different pathogenic mechanism.
Alanine↗
Endopeptidase 3.4.24.11 converts N-1-(R,S)carboxy-3-phenylpropyl-Ala-Ala-Phe-p-carboxyanilide into a potent inhibitor of angiotensin-converting enzyme.
It was reported recently that N-1-(R,S)carboxy-3-phenylpropyl-Ala-Ala-Phe-p-carboxyanilide (CPP-A-A-F-pAB), an inhibitor of endopeptidase 3.4.24.15 (E-24.15), also inhibits angiotensin-converting enzyme (ACE) from rabbit lung. We have found that this compound is without effect on ACE purified from pig kidney, at a concentration some 1000-fold greater than the Ki reported for inhibition of the enzyme from lung. However, preincubation of CPP-A-A-F-pAB with neutral endopeptidase 3.4.24.11 (E-24.11) does result in potent inhibitory effects on ACE. We have shown this to be due to formation of a fragment, CPP-A-A, the structure of which is closely related to ACE inhibitors such as enalaprilat. CPP-A-A was found to be a potent inhibitor of pig ACE. Under the conditions used it had an IC50 value of 1.6 x 10(-8) M, compared with the value obtained for captopril of 7.5 x 10(-10) M. These results have important implications for studies of E-24.15 when using CPP-A-A-F-pAB in vivo or in crude tissue extracts where E-24.11 might also be present.
Amino Acid Sequence↗
A thermospray mass spectrometric assay for Fe-induced 4-hydroxynonenal in tissues.
A method is presented for the determination of 4-hydroxynonenal (HNE) in tissue homogenates following in vitro lipid peroxidation induced by iron (Fe++). HNE is measured as the pentafluorobenzyl oxime derivative using liquid chromatography thermospray mass spectrometry. In vitro metabolism of HNE via the glutathione/glutathione-S-transferase pathway was inhibited using iodoacetic and iodobenzoic acids. The assay has been used as an indicator of the peroxidizability of tissue samples from animals both adequate in and depleted of alpha-tocopherol. The concentrations of HNE produced in tissues taken from animals depleted of alpha-tocopherol were found to be up to 8 times higher than those taken from animals supplemented with alpha-tocopherol.
Aldehydes↗
Antioxidant enzyme activity in the muscles of calves depleted of vitamin E or selenium or both.
Feeding diets depleted of vitamin E and Se to cattle can induce a disease known as nutritional degenerative myopathy. It is believed that an increased peroxidative challenge in muscle is involved in the pathogenesis of this disease. A number of species can up-regulate the activity of some antioxidant enzymes, including glutathione reductase (EC 1.6.4.2), glutathione transferase (EC 2.5.1.18), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), catalase (EC 1.11.1.6), and superoxide dismutase (EC 1.15.1.1), in an attempt to mitigate the effects of a peroxidative challenge. A 2 x 2 factorial study was set up to examine possible changes in the activities of these antioxidant enzymes in muscles of ruminant calves fed on diets low in either vitamin E or Se. Four groups of four calves each were fed on a basal diet of NaOH-treated barley which was supplemented with alpha-tocopherol or Se or both for a total of 50 weeks. Calves fed on diets depleted of vitamin E, but not those fed on diets low in Se, developed subclinical myopathy, as judged by increases in the activity of plasma creatinine kinase (EC 2.7.3.2), and had increased muscle concentrations of two indices of lipid peroxidation, namely thiobarbituric acid-reactive substances, with and without ascorbate activation. Feeding diets depleted of vitamin E and diets low in Se both increased muscle activities of glucose-6-phosphate dehydrogenase in heart, biceps and supraspinatus. This change may have occurred in an attempt to maintain intracellular pools of reduced glutathione. No other changes in antioxidant enzyme activity were observed.
Animals↗
Serum tumor necrosis factor alpha concentrations and clinical abnormalities in colostrum-fed and colostrum-deprived neonatal foals given endotoxin.
We examined the effect of infusion of lipopolysaccharide (LPS) on serum tumor necrosis factor alpha (TNF alpha) concentration and clinical attitude in 2- 3-day-old colostrum-fed (CF) and colostrum-deprived (CD) foals. Eleven CF and 8 CD neonatal foals were given a bolus i.v. infusion of Escherichia coli O55:B5 lipopolysaccharide (0.5 microgram/kg of body weight) in sterile saline (0.9% NaCl) solution. Four CF and 2 CD foals were given saline solution alone. Serum IgG concentration and serum anti-LPS IgG(T) antibody titer were determined for each foal prior to infusion. A depression index was used to score clinical abnormalities. Serum TNF alpha concentration was estimated by use of an in vitro cytotoxicity bioassay that used WEHI 164 clone 13 cells as targets. The cytotoxic serum factor was identified as TNF alpha by immunoprecipitation with caprine antisera raised against the 15 NH2-terminal amino acids of human TNF alpha. Tumor necrosis factor alpha was not detected in any preinfusion serum samples nor in any samples from foals given saline solution alone. Serum TNF alpha concentration increased in all LPS-infused foals and peaked between 60 and 90 minutes after infusion. Serum TNF alpha concentrations, expressed as mean percentage of peak serum TNF alpha concentration, persisted longer in CD foals given LPS than in CF foals given LPS. All LPS-infused foals displayed clinical signs of endotoxemia, but mean depression index scores of the CF and CD foals given LPS were not significantly different at any time. Serum TNF alpha concentrations were correlated with depression index scores in both LPS-infused groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Serum interleukin-6 concentrations in endotoxin-infused neonatal foals.
Serum interleukin-6 (IL-6) concentration was measured in 11 colostrum-fed (CF) and 8 colostrum-deprived (CD) 2- to 3-day-old foals after foals were infused with lipopolysaccharide (LPS; Escherichia coli O55:B5 endotoxin, 0.5 microgram/kg of body weight in sterile saline [0.9% NaCl] solution). Four CF and 2 CD foals were given saline solution alone. Serum IL-6 concentration was estimated by use of an in vitro proliferative bioassay, using the IL-6 dependent B.13.29 clone 9 cells. Interleukin-6 concentration increased in all LPS-infused foals, and geometric mean serum IL-6 concentration was significantly higher in CF than CD foals 30 and 90 minutes after infusion. Both LPS-infused groups had multiple spikes of mean IL-6 concentration that peaked at 120 minutes in CF foals and 150 minutes in CD foals. Results indicated that IL-6 is produced in neonatal foals in response to LPS infusion. Furthermore, colostrum deprivation resulted in longer times to peak mean serum IL-6 concentration and tended to reduce serum IL-6 concentration in neonatal foals.
Animals↗
Vitamin E and selenium deficiencies increase indices of lipid peroxidation in muscle tissue of ruminant calves.
Indices of lipid peroxidation were investigated in muscle tissues of 1) calves depleted of vitamin E and/or Se and 2) calves depleted of vitamin E and Se and fed daily supplements of polyunsaturated fatty acids (PUFA). Calves deficient in both vitamin E and Se or deficient in vitamin E alone showed elevated muscle concentrations of thiobarbituric acid-reactive substances (TBARS), ascorbate-induced TBARS (ATBARS), ascorbate-induced hexanal and iron-induced 4-hydroxynonenal (HNE). Muscle tissue of calves depleted of Se alone showed no increases in these indices of lipid peroxidation. Two further groups of calves were fed diets either sufficient or deficient in both vitamin E and Se. Both of these groups were then fed linseed oil, protected against ruminal hydrogenation, as a source of PUFA. The deficient animals had higher muscle concentrations of all three indices of lipid peroxidation than the supplemented calves. Furthermore, feeding PUFA to vitamin E and Se deficient animals increased muscle concentrations of induced HNE to levels above those in deficient animals not fed PUFA supplements.
Aldehydes↗
Dopamine D1 and D2 receptor interactions in the MPTP-treated marmoset.
In a modified MPTP model of Parkinson's disease in the marmoset, both L-DOPA and the dopamine D2 agonist quinpirole were found to exhibit anti-bradykinetic activity. Both the dopamine D1 agonist SKF38393 and the D1 antagonist SCH23390 reduced the anti-bradykinetic action of L-DOPA and quinpirole. These results are discussed with respect to partial agonist activity of SKF38393 and the possibility that other dopamine receptors may be required for anti-Parkinsonian drug activity.
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
Role of NK-2 receptors in the antidipsogenic activity of neurokinins in the mouse.
1. The receptors involved in the anti-dipsogenic activity of neurokinin (NK) agonists were investigated in water-deprived mice. 2. Intracerebral administration of agonists selective at all three NK receptors (NK-1, NK-2, NK-3) caused inhibition of drinking in this model. However, only the NK-2 receptor agonist, GR64349, inhibited drinking without producing other behavioural effects. Both NK-1 (GR73632) and NK-3 (senktide) agonists induced a variety of behavioural effects which appeared to compete with the drinking response. 3. The inhibitory effect on drinking observed after central injection of the NK-2 agonist, GR64349, was attenuated by co-administration of the NK-2 antagonist, L-659,877, but not by the NK-1 antagonist, GR82334. 4. These results illustrate that the antidipsogenic activity of the NKs, in mice, is mediated via NK-2 receptors.
Animals↗
Evaluation of a single injection of 99mTc-labeled diethylenetriaminepentaacetic acid for measuring glomerular filtration rate in horses.
Glomerular filtration rate (GFR) was measured in 12 clinically normal horses, using the standard inulin clearance method, and values were compared with values for 2 methods, using a single rapid IV injection of 99mTc-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). The first 99mTc-DTPA method used a 2-compartment model to calculate GFR blood clearance of the tracer. The second method used sequential digital gamma camera images of the kidneys to determine fractional accumulation of the total dose of the tracer in the kidneys (percentage of injected dose, gamma camera) from 0 to 10 minutes after radionuclide administration. Linear correlation among the 3 methods was determined. Mean (+/- SD) GFR, using the inulin clearance method, was 154.67 +/- 42.28 ml/min/100 kg of body weight. Mean GFR, using the 2-compartment blood clearance curve, was 146.92 +/- 27.49 ml/min/100 kg. Mean GFR, using percentage of injected dose (gamma camera method) was 154.7 +/- 22.00 ml/min/100 kg. The percentage of injected dose (gamma camera method) did not correlate significantly to the inulin clearance results. However, a significant (r = 0.666, P less than 0.018) correlation was observed between the inulin method and the 99mTc-DTPA blood clearance method. Significant (P less than 0.0001) difference also was observed in the split function of the equine kidneys, with GFR of the right kidney contributing 60.1 +/- 9.12% of the total function, as determined by 99mTc-DTPA gamma camera imaging. Because the 99mTc-DTPA blood clearance method does not require urine collection, it may be a more practical procedure to measure GFR in the horse.
Animals↗
The effect of vitamin E and/or selenium depletion on tissue peroxidation and peroxidisability in ruminant cattle.
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Animals↗
The pharmacology of fluparoxan: a selective alpha 2-adrenoceptor antagonist.
1. This paper describes the pharmacology of the novel alpha 2-adrenoceptor antagonist fluparoxan (GR 50360) which is currently being studied clinically as a potential anti-depressant. Idazoxan and yohimbine were included in many studies for comparison. 2. In the rat isolated, field-stimulated vas deferens and the guinea-pig isolated, field-stimulated ileum preparations, fluparoxan was a reversible competitive antagonist of the inhibitory responses to the alpha 2-adrenoceptor agonist UK-14304 with pKB values of 7.87 and 7.89 respectively. In the rat isolated anococcygeus muscle, fluparoxan was a much weaker competitive antagonist of the contractile response to the alpha 1-adrenoceptor agonist phenylephrine with a pKB of 4.45 giving an alpha 2: alpha 1-adrenoceptor selectivity ratio of greater than 2500. 3. In the conscious mouse, fluparoxan (0.2-3.0 mg kg-1) was effective by the oral route and of similar potency to idazoxan in preventing clonidine-induced hypothermia and antinociception. In the rat, UK-14304-induced hypothermia (ED50 = 1.4 mg kg-1, p.o. or 0.5 mg kg-1, i.v.) and rotarod impairment (ED50 = 1.1 mg kg-1 p.o. or 1.3 mg kg-1, i.v.) were antagonized by fluparoxan. Fluparoxan, 0.67-6 mg kg-1, p.o., also prevented UK-14304-induced sedation and bradycardia in the dog. 4. In specificity studies fluparoxan had low or no affinity for a wide range of neurotransmitter receptor sites at concentrations up to at least 1 x 10(-5) M. It displayed weak affinity for 5-HT1A (pIC50 = 5.9) and 5-HT1B (pKi = 5.5) binding sites in rat brain. 5. We conclude that fluparoxan is a highly selective and potent alpha 2-adrenoceptor antagonist. The density of rat brain [3H]-dihydroalprenolol binding sites was reduced by 26% when fluparoxan was administered chronically for 6 days at a dose of 12 mg kg- 1 orally twice daily. The down-regulation of beta-adrenoceptors by fluparoxan is consistent with its antidepressant potential.
Adrenergic alpha-Agonists↗
Neuroleptic-induced catalepsy as a model of Parkinson's disease. I. Effect of dopaminergic agents.
Catalepsy was observed in the rat following intrastriatal injections of the dopamine antagonists sulpiride or fluphenazine and after subcutaneous administration of fluphenazine. The neuroleptic-induced catalepsy was reversed by the classical anti-parkinsonian agent L-DOPA and by agents that function through dopamine systems such as d- and methamphetamine and the direct D2 receptor agonist quinpirole. The D1 agonist SKF 38393, and the D1/D2 agonist apomorphine, were ineffective in this model. These results support limited use of the rat catalepsy model for the screening of potential anti-parkinsonian compounds and indicate that this procedure can provide valuable information concerning striatal dopamine function.
Animals↗
Neuroleptic-induced catalepsy as a model of Parkinson's disease. II. Effect of glutamate antagonists.
Subcutaneous administration of fluphenazine elicits catelepsy that can be attenuated by the glutamate antagonists MK801 and phencyclidine (PCP). 3-[-(+)-2-carboxy piperazine-4-yl]-propyl-1-phosphanate (CPP) was found to be ineffective in this model. Intrastriatal injections of sulpiride or fluphenazine were also found to induce catalepsy which could be attenuated by MK801 and PCP. These results illustrate that nondopaminergic compounds might possibly be of value in the treatment of Parkinson's disease. Furthermore it was demonstrated that this paradigm can be utilized to investigate neurotransmitter interactions within the striatum. This was clearly emphasized by the observation that bilateral administration of MK801 into the striatum increased basal locomotor activity.
Animals↗
Behavioural effects of serotonin agonists and antagonists in the rat and marmoset.
The present study was conducted to investigate the effects of various 5-hydroxytryptamine (5-HT) agonists and antagonists on motor behaviour in rats and marmosets. Various motor-based responses were assessed after central or peripheral administration of 5-HT agents to rats and marmosets. Drugs acting as agonists at the 5-HT1A receptor (8-OHDPAT, gepirone, BMY-7378, NAN-190, PAPP (LY165163) and flesinoxan) and 5-HT2/1C receptors (DOI) were found to reverse neuroleptic-induced catalepsy in the rat whereas 5-HT2/1C antagonists (mianserin, ritanserin and ICI-170,809) and the 5-HT1 antagonist ((+/-)pindolol) increased catalepsy. Agonists acting at 5-HT3 receptors (phenylbiguanide and 2-methyl-5-HT) had no effect on catalepsy. The putative 5-HT1A antagonist, (+/-) pindolol, attenuated the reversal of catalepsy by 8-OHDPAT. Although both 8-OHDPAT and BMY-7378 were tested, only the latter was found to reduce apomorphine-induced stereotypy. Bilateral or unilateral infusions of 8-OHDPAT, BMY-7378 or pindolol into the substantia nigra of non-lesioned rats had no effect on spontaneous locomotor or rotational activity, respectively. However, 8-OHDPAT and BMY-7378 were found to increase or decrease motor activity, after injection into the median or dorsal raphe nuclei, respectively. Finally, 8-OHDPAT and BMY-7378 were found to be inactive against MPTP-induced bradykinesia in the marmoset. It is concluded that both 5-HT1A and 5-HT2/1C receptors are involved in the anti-cataleptic effects of 5-HT agents. The 5-HT1A receptors are probably situated within the raphe, whereas the location of the 5-HT2/1C receptors remains undetermined.
Animals↗