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Biomedical subjects

A Fisher

Publications and source records attributed to A Fisher.

At least 19 recordsLinked to original sources
PubMed1999

Effect on cell kill of addition of multidrug resistance modifiers cyclosporin A and PSC 833 to cytotoxic agents in chronic lymphocytic leukaemia.

Expression of P-glycoprotein (Pgp), the drug efflux pump which mediates multidrug resistance (MDR), has been widely reported in chronic lymphocytic leukaemia (CLL) and improved accumulation of daunorubicin has been reported using the MDR reversing agent cyclosporin A (CSA). We have investigated the effects on cell kill of the addition of CSA and its analogue PSC 833 to daunorubicin, doxorubicin, idarubicin, mitozantrone and fludarabine in samples from 51 patients with CLL using an MTT [3(4,5-dimethylthaizol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Pgp expression was assessed by immunocytochemistry using the JSB-1 monoclonal antibody. Of the 51 samples, 10 (20%) were Pgp positive and all of these samples were from treated patients. With the exception of mitozantrone, the addition of CSA and PSC 833 to cytotoxic agents failed to significantly improve cytotoxicity, even in the Pgp positive group. With mitozantrone significant responses were seen in both Pgp positive and negative groups suggesting that the responses were due to direct cytotoxicity of the cytotoxic-modifier combination rather than reversal of MDR. Both CSA and PSC 833 showed significant direct cytotoxicity (P = 0.004 and 0.04 for PSC 833 at 1000 ng/ml and 500 ng/ml respectively; P < 0.001 for both concentrations of CSA). The responses were disappointing compared to the highly significant improvements in cytotoxicity seen using cells from the Pgp positive CEM VLB 100 acute myeloid leukaemia cell line, and it was not possible to demonstrate the superiority of PSC 833 over CSA which is also seen in cell lines. Our data do not support a role for Pgp modifiers in CLL. Further studies using larger numbers of Pgp positive CLL cells and higher doses of PSC 833 would be useful.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Site-specific dephosphorylation of tau of apolipoprotein E-deficient and control mice by M1 muscarinic agonist treatment.

Apolipoprotein E (apoE)-deficient mice have memory deficits that are associated with synaptic loss of basal forebrain cholinergic projections and with hyperphosphorylation of distinct epitopes of the microtubule-associated protein tau. Furthermore, treatment of apoE-deficient mice with the M1 selective agonist 1-methylpiperidine-4-spiro-(2'-methylthiazoline) [AF150(S)] abolishes their memory deficits and results in recovery of their brain cholinergic markers. In the present study, we used a panel of anti-tau monoclonal antibodies to further map the tau epitopes that are hyperphosphorylated in apoE-deficient mice and examined the effects of prolonged treatment with AF150(S). This revealed that tau of apoE-deficient mice contains a distinct, hyperphosphorylated "hot spot" domain which is localized N-terminally to the microtubule binding domain of tau, and that AF150(S) has an epitope-specific tau dephosphorylating effect whose magnitude is affected by apoE deficiency. Accordingly, epitopes which reside in the hyperphosphorylated "hot spot" are dephosphorylated by AF150(S) in apoE-deficient mice but are almost unaffected in the controls, whereas epitopes which flank this tau domain are dephosphorylated by AF150(S) in both mice groups. In contrast, epitopes located at the N and C terminals of tau are unaffected by AF150(S) in both groups of mice. These findings suggest that apoE deficiency results in hyperphosphorylation of a distinct tau domain whose excess phosphorylation can be reduced by muscarinic treatment.

Animals↗
PubMed1999

Reduction of motoric agitation and restlessness by AF102B and tacrine in the macaque.

The cholinesterase inhibitor tacrine (THA) and the M1 muscarinic agonist AF102B (cevimeline), both reported to enhance cognition in animals and humans, were tested in 5 macaques for reduction of spontaneous, random movements. Monkeys were videotaped 1 hour after administration of normal saline vehicle, after low- and high-dose intramuscular AF102B, and after low- and high-dose oral THA. Two independent blind judges counted numbers of spontaneous movements made by each monkey over 12 consecutive 15-second segments for each drug condition. Both THA and AF102B reduced movement significantly at high doses without overt side effects, warranting further research on the agitation-reducing potential of cognition-enhancing cholinomimetic drugs.

Alzheimer Disease↗
PubMed1998

Detection of HIV-1 nucleic acid and HIV-1 antibodies in needles and syringes used for non-intravenous injection.

BACKGROUND: HIV antibodies and HIV DNA have been detected in needles and syringes that have been used for intravenous injections in HIV-infected persons. During intravenous injection, blood is typically aspirated into the lumen of the syringe. During intramuscular or subcutaneous injection, however, blood is not usually introduced into the syringe. OBJECTIVES: To investigate the presence of HIV antibodies, HIV proviral DNA, HIV RNA, and human DNA in needles and syringes that had been used for intramuscular or subcutaneous injection in persons known to have HIV infection. METHODS: Discarded disposable needles and syringes used by health-care personnel for medically indicated intramuscular or subcutaneous injections of HIV-infected patients were collected. Residual material was extracted from the syringes. The extracts were analyzed by enzyme immunoassay for the presence of HIV antibodies. PCR was conducted to detect HIV and human DNA, as well as HIV RNA. RESULTS: HIV antibodies were detected in 16 (6.2%) out of 260 syringes. Human DNA or HIV-specific DNA were not detected. A second set of 80 syringes was collected to examine the presence of HIV RNA. HIV RNA was detected in three (3.8%) out of 80 syringes. CONCLUSION: This analysis demonstrates that the risk of transmitting HIV from syringes that have been used for intramuscular or subcutaneous injection may be low, but is not zero.

DNA, Viral↗
PubMed1998

Differential effects of NMDA and non-NMDA antagonists on the activity of aromatic L-amino acid decarboxylase activity in the nigrostriatal dopamine pathway of the rat.

This study examined the acute effects of a variety of NMDA and non-NMDA antagonists on the activity of aromatic l-amino acid decarboxylase (AADC) in the corpus striatum (CS) and substantia nigra (SN) of the rat. Sixty min pretreatment with the high affinity NMDA receptor-channel blockers MK 801 (0.01, 0.1 and 1 mg/kg) and phencyclidine (4 mg/kg) elevated AADC activity in both the CS and SN (2- to 3-fold). Even more striking increases in AADC were noted with 40 mg/kg amantadine (3.8-fold for CS, 9.0-fold for SN), 40 mg/kg memantine (3.4-fold for CS, 3.1-fold for SN; 20 mg/kg no effect) and 40 mg/kg dextromethorphan (3.4-fold for CS, 6.2-fold for SN, in 6/10 'responders'). Similarly pronounced increases in AADC activity in CS (1.9-fold) and SN (2.8-fold) were detected after administering clonidine (2 mg/kg). R-HA 966 (5 mg/kg, not 1 mg/kg) modestly raised AADC activity in CS (0.45-fold) and not SN. Other drugs had no effect on the activity of the decarboxylase enzyme, including CGP 40116 (1 and 5 mg/g), eliprodil (10 mg/kg), NBQX (10 mg/kg, 30 min pretreatment) and atropine (1 mg/kg). These experiments indicate that blocking the NMDA receptor-channel (and to a lesser extent the glycine site) or stimulating alpha2-adrenoceptors, profoundly increases AADC activity, more especially in the SN than CS. By contrast, inhibiting the NMDA glutamate recognition or polyamine sites, AMPA or muscarinic receptors is without effect on AADC in either brain region. The ability of amantadine and memantine to potentiate the antiparkinsonian actions of l-DOPA in the clinic, may be due to facilitated decarboxylation of l-DOPA by the brain.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1998

The antiparkinsonian drug budipine stimulates the activity of aromatic L-amino acid decarboxylase and enhances L-DOPA-induced dopamine release in rat substantia nigra.

The present study examined the effects of the antiparkinsonian drug budipine on dopamine synthesis and release from L-DOPA in the substantia nigra of reserpine-treated rats. Budipine (at 100 microM, but not 10 microM) applied by reverse dialysis to the nigra caused a small and significant rise in dopamine recovery in normal rats, but not in rats pretreated with reserpine (4 mg/kg i.p. for 18 hours) and alpha-methyl-p-tyrosine (alpha-MPT; 200 mg/kg i.p. for 1 hour to limit dopamine synthesis to L-DOPA). L-DOPA applied to the nigra by reverse dialysis in reserpine + alpha-MPT-treated rats, increased the recovery of dopamine when applied at 5 or 10 microM, but not at 2 microM. Coadministration of budipine (10 microM) significantly enhanced L-DOPA-induced dopamine (and DOPAC) release with 5 microM L-DOPA, but not with 2 or 10 microM L-DOPA. This potentiation was even more pronounced when the budipine concentration was raised to 100 microM (equivalent to approximately 10 microM extracellularly). Pretreating rats with budipine (5, 12.5, or 20 mg/kg i.p.) for 1 hour significantly raised the activity of the enzyme L-aromatic amino acid decarboxylase in the striata and nigras of intact rats, as well as in rats pretreated with reserpine alone (5 mg/kg i.p.), without altering tissue levels of dopamine or its metabolites. It is suggested that the beneficial effects of budipine, when used as an adjunct to L-DOPA therapy of Parkinson's disease, may be due to an increase in the bioconversion of L-DOPA with a consequent rise in synaptic dopamine. These actions of budipine may be related to its weak NMDA receptor antagonist property.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

The function of hairy-related bHLH repressor proteins in cell fate decisions.

Hairy-related proteins are a distinct subfamily of basic helix-loop-helix (bHLH) proteins that generally function as DNA-binding transcriptional repressors. These proteins act in opposition to bHLH transcriptional activator proteins such as the proneural and myogenic proteins; together, the activator and repressor genes that encode these proteins have co-evolved as a regulatory gene "cassette" or "module" for controlling cell fate decisions. In the development of the Drosophila peripheral nervous system, Hairy-related genes function at multiple steps during neurogenesis, for example, as positional information genes that establish the "prepattern" that controls where "proneural cluster" equivalence groups will form, and later as nuclear effectors of the Notch signaling pathway to "single out" individual precursor cells within the equivalence group. Hairy-related genes also function in the establishment and restriction of other types of equivalence groups, such as those for muscle and Malphigian tubule precursors. This general function in cell fate specification has been conserved from Drosophila to vertebrates and has implications for human disease pathogenesis.

Animals↗
PubMed1998

Effects of glutamate antagonists on the activity of aromatic L-amino acid decarboxylase.

This study examines the hypothesis that glutamate tonically suppresses the activity of the enzyme aromatic L-amino acid decarboxylase (AADC), and hence the biosynthesis of dopamine, to explain how antagonists of glutamate receptors might potentiale the motor actions of L-DOPA in animal models of Parkinson's disease. A variety of glutamate antagonists were therefore administered acutely to normal rats, which were sacrificed 30-60 min later and AADC activity assayed in the substantia nigra pars reticulata (SNr) and corpus striatum (CS). The NMDA receptor-ion channel antagonists MK 801, budipine, amantadine, memantine and dextromethorphan all caused a pronounced in creased in AADC activity, more especially in the SNr than CS. The NMDA glycine site antagonist (R)-HA 966 produced a modest increase in AADC activity in the CS but not SNr, whilst the NMDA polyamine site antagonist eliprodil, the NMDA competitive antagonist CGP 40116 and the AMPA antagonist NBQX were without effect. The results suggest that an increase in dopamine synthesis might contribute to the L-DOPA-facilitating actions of some glutamate antagonists.

Animals↗
PubMed1998

Quantitative heel ultrasound in 3180 women between 45 and 75 years of age: compliance, normal ranges and relationship to fracture history.

There is growing evidence to support the use of quantitative ultrasound (QUS) to identify fracture risk in late postmenopausal women but few data are available in younger women. In order to address this issue all women between 45 and 75 years of age registered in two general practices in Bournemouth, Dorset, UK were invited to attend for heel QUS. Measurements were made in 79% of the 4018 women identified. The mean QUS results for 5-year age groups were very similar to those from reported reference ranges from North America and the north of England. The odds ratios (95% confidence limits) for self-reported fractures after 45 years per standard deviation of age-adjusted QUS parameters were: broadband ultrasound attenuation (BUA) = 1.40 (1.26-1.56), speed of sound (SOS) = 1.56 (1.41-1.74) and Stiffness = 1.52 (1.37-1.68). The results suggest that QUS is associated with fracture history in early postmenopausal women.

Aged↗
PubMed1998

Effects of AF102B and tacrine on delayed match-to-sample in monkeys.

1. Object working memory, a function which declines in aging and dementia, was tested in young and aged pretrained monkeys using a delayed match-to-sample task. 2. During drug treatment, monkeys were given the m 1 muscarinic agonist AF102B (0.1-2.1 mg/kg i.m.), the cholinesterase inhibitor tacrine (0.5-2.0 mg/kg p.o.), or vehicle controls in a repeated measures design to assess putative cognitive enhancement. 3. Both agents improved task performance in both young and aged monkeys, AF102B yielding equivalent or greater, and less variable, improvement than tacrine. 4. AF102B may represent a low-toxicity alternative to tacrine for the treatment of age-related memory disorders.

Age Factors↗
PubMed1998

Rating threat mitigators: faith in experts, governments, and individuals themselves to create a safer world.

This research explores public judgments about the threat-reducing potential of experts, individual behavior, and government spending. The data are responses of a national sample of 1225 to mail surveys that include measures of several dimensions of public judgments about violent crime, automobile accidents, hazardous chemical waste, air pollution, water pollution, global warming, AIDS, heart disease, and cancer. Beliefs about who can best mitigate threats are specific to classes of threats. In general, there is little faith that experts can do much about violent crime and automobile accidents, moderate faith in their ability to address problems of global warming, and greater expectations for expert solutions to the remaining threats. People judge individual behavior as effective in reducing the threats of violent crime, AIDS, heart disease, and automobile accidents but less so for the remaining threats. Faith in more government spending is highest for AIDS and the other two health items, lowest for the trio of violent crime, automobile accidents, and global warming, and moderate for the remaining threats. For most threats, people are not distributed at the extremes in judging mitigators. Strong attitudinal and demographic cleavages are also lacking, although some interesting relationships occur. This relative lack of sharp cleavages and the generally moderate opinion indicate ample opportunity for public education and risk communication.

Adult↗
PubMed1998

Non-invasive measurement of colonic blood flow distribution using laser Doppler imaging.

BACKGROUND: This study tested a prototype laser Doppler scanner for the measurement of human colonic blood flow. METHODS: Blood flow distribution was assessed in human colon during operation in six controls and in six patients with inflammatory bowel disease undergoing colectomy. Image processing software analysed several hundred reading points, expressing average flow in perfusion units. RESULTS: Blood flow in the colon was not significantly lower in the control group than in patients with inflammatory bowel disease (mean(s.e.m.) 297.8(24.5) versus 347.2(59.0) perfusion units, P = 0.12). Intestinal colonic mural blood supply was demonstrated up to a distance of 6 cm and ischaemia demarcation lines were identified before the onset of visible changes. CONCLUSIONS: This prototype laser Doppler flowscanner overcomes the previous limitations of laser Doppler flowmeters and may have many clinical and research applications.

Adult↗
PubMed1998

M1 muscarinic agonist treatment reverses cognitive and cholinergic impairments of apolipoprotein E-deficient mice.

Recent studies suggest that apolipoprotein E (apoE) plays a specific role in brain cholinergic function and that the E4 allele of apoE (apoE4), a major risk factor for Alzheimer's disease (AD), may predict the extent of cholinergic dysfunction and the efficacy of cholinergic therapy in this disease. Animal model studies relevant to this hypothesis revealed that apoE-deficient (knockout) mice have working memory impairments that are associated with distinct dysfunction of basal forebrain cholinergic neurons. Cholinergic replacement therapy utilizing M1-selective muscarinic agonists has been proposed as effective treatment for AD patients. In the present study, we examined whether the memory deficits and brain cholinergic deficiency of apoE-deficient mice can be ameliorated by the M1-selective agonist 1-methylpiperidine-4-spiro-(2'-methylthiazoline), [AF150(S)]. Treatment of apoE-deficient mice with AF150(S) for 3 weeks completely abolished their working memory impairments. Furthermore, this reversal of cognitive deficit was associated with a parallel increase of histochemically determined brain choline acetyltransferase and acetylcholinesterase levels and with the recovery of these cholinergic markers back to control levels. These findings show that apoE deficiency-related cognitive and cholinergic deficits can be ameliorated by M1-selective muscarinic treatment. They also provide a novel model system for development and evaluation of therapeutic strategies directed specifically at the AD patients whose condition is attributed to the apoE genotype.

Acetylcholinesterase↗
PubMed1998

Mitogen-activated protein kinase-dependent and protein kinase C-dependent pathways link the m1 muscarinic receptor to beta-amyloid precursor protein secretion.

Full and functionally selective M1 muscarinic agonists (carbachol and AF102B, respectively) activate secretion of the soluble form of amyloid precursor protein (APPs) in PC12 cells expressing the m1 muscarinic receptor (PC12M1 cells). This activation is further augmented by neurotrophins such as nerve growth factor and basic fibroblast growth factor. Muscarinic stimulation activates two transduction pathways that lead to APPs secretion: protein kinase C (PKC)-dependent and mitogen-activated protein kinase (MAPK)-dependent pathways. These pathways operate in parallel and converge with transduction pathways of neurotrophins, resulting in enhancement of APPs secretion when both muscarinic agonist and neurotrophins stimulate PC12M1 cells. These conclusions are supported by the following findings: (a) Only partial blockade of APPs secretion is observed when PKC, p21ras, or MAPK is fully inhibited by their respective specific inhibitors, GF109203X, S-trans, trans-farnesylthiosalicylic acid, and PD98059. (b) K252a, which blocks PKC and phorbol 12-myristate 13-acetate-induced APPs secretion, enhances both muscarinic-stimulated MAPK activation and APPs secretion. (c) Activation of MAPK in PC12M1 cells by muscarinic agonists is Ras-dependent but PKC-independent and is enhanced synergistically by neurotrophins. These results suggest that muscarinic stimulation of APPs secretion is mediated by at least two independent pathways that converge and enhance the signal for APPs secretion at the convergence point.

Amyloid beta-Protein Precursor↗
PubMed1998

Structure-function relationships of aldosterone synthase and 11 beta-hydroxylase enzymes: implications for human hypertension.

1. The genes encoding aldosterone synthase (CYP11B2) and 11 beta-hydroxylase (CYP11B1) are very similar at the nucleotide level (> 95% homology). Despite this and the corresponding similarity of amino acid sequence, there are considerable differences in functional and substrate specificity of the two enzymes. In the present study we have examined the role of two amino acids that differ between the two enzymes (147 and 248) to determine the difference between aldosterone synthase and 11 beta-hydroxylase capacity to 11-hydroxylate 11-deoxycorticosterone (DOC). 2. Plasmids containing cDNA encoding wild-type aldosterone synthase, wild-type 11 beta-hydroxylase and mutated forms of aldosterone synthase (D147E and I248T), in which the codons for residues 147 (aspartate exon 3) or 248 (isoleucine exon 4) had been altered to encode the corresponding amino acids (glutamate and threonine respectively) from 11 beta-hydroxylase were transiently expressed in non-steroidogenic COS-7 cells. All transfections were cotransfected with bovine adrenodoxin. Cells were then incubated with [3H]-DOC for 48 h and the production of corticosterone (B), 18-hydroxycorticosterone (18-OHB) and aldosterone measured by measuring tritriated products using thin layer chromatography. 3. Compared with wild-type aldosterone synthase, the mutated form (D147E) encoding amino acid 147 from 11 beta-hydroxylase was more efficient in 11 beta-hydroxylation of deoxycorticosterone (B:DOC ratio 0.53 +/- 0.05 (wild type) to 3.05 +/- 0.37 (mutant); P < 0.001). However, 18-hydroxylation of B and conversion of this steroid into aldosterone were unaffected. There was a 20% increase in the production of aldosterone from DOC (P < 0.05). However, in comparison with wild-type 11 beta-hydroxylase, the mutated aldosterone synthase (D147E) was still less efficient (B:DOC ratio 6.2 +/- 0.41). The mutated aldosterone synthase (I248T) encoding amino acid 248 from 11 beta-hydroxylase showed no changes in conversion of DOC to B or in the production of aldosterone. 4. These data demonstrate that position 147 has an important effect on the efficiency of 11 beta-hydroxylation of DOC and indicate that this is a key difference between the two enzymes in determining functional specificity. However, other residues must also contribute to efficiency of 11-hydroxylation of 11 beta-hydroxylase. In contrast, amino acid 248, which is one of the few differences between the two enzymes in exon 4, does not affect enzyme efficiency. As altered activity of aldosterone synthase and 11 beta-hydroxylase has been proposed as an important intermediate phenotype in essential hypertension, such studies will help our understanding of the structure-function relationships that will be necessary in order to understand how genetic changes may contribute to observed differences in phenotype.

18-Hydroxycorticosterone↗
PubMed1998

Expression and mapping of protein phosphatase 2A alpha in the developing rat heart.

Protein phosphatase 2A (PP2A) is a second messenger involved in cell cycle regulation, cell transformation, and cell fate determination. We previously identified a gene encoding the alpha catalytic subunit of PP2A in the embryonic rat heart, but its role in cardiac morphogenesis was unknown. In this study, we examined the developmental expression of PP2A alpha mRNA and protein in the heart using Northern and Western analysis, in situ hybridization, and immumohistochemical staining. We found two major PP2A alpha transcripts in the rat heart (1.8 and 2.4 kb), at all stages examined. By Western blotting, PP2A alpha protein levels were twice as high in the embryonic rat heart compared with the adult. In situ hybridization on embryonic d 12 showed that PP2A alpha mRNA was expressed in the heart, brain, tail, and limb buds. Cardiac PP2A alpha expression was regionally restricted to the atrium, ventricle, and truncus arteriosus. PP2A alpha expression did not extend into the more distal aortic sac or aortic arches. Cross-sectional hybridization revealed PP2A alpha mRNA in the epicardium, pericardium, and endothelium. Later in development, mRNA expression was also detected at high levels in mesenchymal cells populating the endocardial cushions and in myocardium. At term, PP2A alpha was highly expressed in endothelial cells, but not in the underlying myocardium. PP2A alpha protein had a similar distribution at all embryonic stages examined. These results show that there is transcriptional, translational, and cell-specific regulation of PP2A alpha during heart development. We speculate on the role of PP2A alpha-mediated dephosphorylation in cardiac morphogenesis and suggest a number of possible molecular targets.

Animals↗
PubMed1998

Portable satellite telemedicine in practice.

The US army's first portable telemedicine unit was built in 1993 and comprised a 'ruggedized' videoconferencing unit. The unit was initially used in the United Nations' operations in Macedonia in February 1994 and subsequently in support of the Mobile Army Surgical Hospitals in Haiti, but its dimensions made it suitable only for locations where a move at short notice was unlikely. The second portable telemedicine unit comprised a PC linked to an Inmarsat B earth station through a modern. The unit allowed videoconferencing at 64 kbit/s. Three and a half years of clinical experience with both units has shown this to be quite adequate for the majority of clinical telemedicine. Portable telemedicine units have been a major benefit to medical commanders in the field.

Bosnia and Herzegovina↗