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Biomedical subjects

A Fletcher

Publications and source records attributed to A Fletcher.

At least 127 records · Page 7Linked to original sources
PubMed1995

Risk factors for ischaemic heart disease and stroke mortality in young and old hypertensive patients.

We investigated the predictors of cardiovascular mortality at different ages in a longitudinal study of 10186 hypertensive patients attending clinics in the UK. There were 7374 patients (51% were men) < 60 years of age and 2799 patients (44% men) were > or = 60 years. For IHD death the age-adjusted relative risks (RRs) and 95% confidence intervals (CI) for a 1 mmol/l increase in cholesterol were RR = 1.17 (1.07, 1.27) (men) and RR = 1.22 (1.12, 1.33) (women). The RRs for stroke were 0.99 (men) and 1.07 (women). In men and younger women, urea and smoking were important predictors of IHD and stroke death. Age differences were present in women for both urea and smoking. For IHD in women, smoking: RR = 2.65 (1.80, 3.89) (< 60 years) and RR = 1.38 (1.01, 1.88) (> or = 60 years). For stroke in women, smoking: RR = 2.03 (1.23, 3.35) (< 60 years) and RR = 1.06 (0.70, 1.61) (> or = 60 years). We conclude that urea and smoking are important risk factors for stroke and IHD death in hypertensive women aged < 60 years, but are less important in those aged over 60 years. Cholesterol predicted IHD death in all men and women, but did not predict stroke death.

Adult↗
PubMed1995

Preservation of normal left ventricular geometry during mitral valve replacement.

The role of the subvalvular apparatus in preserving left ventricular (LV) systolic function, regional LV mechanics and three-dimensional contraction synergy has now been generally accepted. We have developed techniques for maintaining the mitral annulopapillary muscle continuity during mitral valve replacement (MVR) to preserve the normal geometry of the left ventricle. From January 1990 through February 1995, a total of 375 patients underwent MVR. In 183 patients, the entire subvalvular apparatus was retained or the mitral annulo-papillary muscle continuity was reconstructed with Gore-tex sutures. There were 100 males and the average patient age was 64 (24-84) years. One hundred and forty-seven patients had mechanical bileaflet valves implanted and the remaining 36 received bioprostheses. One hundred and nine patients underwent isolated MVR with an operative mortality of three (2.8%), 52 patients had combined MVR and coronary surgery with four deaths (7.7%), 15 patients had multiple valve procedures with one death (6.7%) and seven patients had MVR combined with miscellaneous procedures with no operative deaths. All patients underwent transesophageal echocardiography evaluation intra-operatively. In addition, transthoracic echocardiograms performed during the follow up period (3 mo.-5 yrs.) have demonstrated preservation of global LV function with no evidence of LV outflow tract obstruction. We conclude that preserving the LV geometry by normal anatomical chordal preservation or replacement during MVR is a safe technique resulting in gratifying intermediate term results.

Adult↗
PubMed1994

The influence of 5-hydroxytryptamine re-uptake blockade on CCK receptor antagonist effects in the rat elevated zero-maze.

In this study, the elevated zero-maze model of anxiety was used to investigate CCK receptor antagonist effects on the behaviour of male Lister-hooded rats and to demonstrate, by administering antagonists in the presence or absence of selective 5-hydroxytryptamine (5-HT) re-uptake inhibitors, the involvement of 5-HT in the mediation of these effects. Devazepide, a selective CCKA receptor antagonist, L-365,260 (3R(+)-N-2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepin- 3-yl-N1- (3-methyl-phenyl)urea) or CI-988 (4-([2-[[3-(1H-indol-3-yl)-2-methyl-1- oxo-2-[[(tricyclo[3.3.1.1.(3.7)]-dec-2-yloxy)-carbonyl]-amin o]- propyl]-amino]-1-phenylethyl]-amino)-4-oxo-[R-(R*,R*)]-butanoate- N-methyl-D-glucamine), both selective CCKB receptor antagonists, were administered 30 min prior to testing. Behavioural analysis during testing included measures of risk-assessment behaviours (e.g. stretched-attend posture) in addition to time spent on the open quadrants. Devazepide induced significant anxiolytic effects, whereas CI-988 produced inconsistent results and L-365,260 was ineffective. When administered simultaneously with the 5-HT re-uptake inhibitors zimelidine or Wy 27587 (N-[[[1-[(6- fluoro-2-naphthalenyl)methyl]-4-piperidinyl]amino] carbonyl]-3-pyridine carboxamide methyl sulphonate salt), the significant anxiolytic effect induced by devazepide was dose-dependently and significantly attenuated. Zimelidine and Wy27587 had little effect alone on zero-maze behaviour at the lower of two doses given. These data show that the elevated zero-maze, in conjunction with the analysis of 'risk-assessment' behaviours, is an anxiety model which is sensitive to the anxiolytic effects of CCK receptor antagonism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Evaluation of [O-methyl-3H]WAY-100635 as an in vivo radioligand for 5-HT1A receptors in rat brain.

N-(2-(4-(2-Methoxyphenyl)-1-piperazinyl)ethyl)-N-(2- pyridyl)cyclohexanecarboxamide trihydrochloride (WAY-100635) is a new, potent and selective 5-HT1A receptor antagonist. We have evaluated radiolabelled WAY-100635 as a prospective radioligand for positron emission tomography (PET) by studying biodistribution in rat ex vivo. After intravenous injection, [O-methyl-3H]WAY-100635 cleared rapidly from plasma but was retained in brain. Specific binding was quantified from kinetic studies, using a reference-tissue compartment model, fitting for binding potential (k3/k4). The regional variation in binding potential correlated with the known distribution of 5-HT1A receptors. Saturation studies gave Bmax values in vivo that were consistent with those reported in vitro. At 60 min after injection, the ratio of radioactivity in 5-HT1A receptor-rich regions (e.g. septum, entorhinal cortex and hippocampus) to that in cerebellum reached approximately 16. Pre-dosing the rats with WAY-100635 (2 mg/kg) reduced this ratio to one, whereas similar pre-dosing with citalopram (5-HT uptake site inhibitor), prazosin (alpha 1A-adrenoceptor antagonist) or idazoxan (alpha 2-adrenoceptor antagonist) caused little or no reduction. Substantial (77%) blockade of [3H]WAY-100635 binding was achieved with the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), and the partial agonists, ipsapirone and buspirone. Thus, the properties of WAY-100635 are such that, when labelled with carbon-11, it could provide a radioligand suitable for clinical and pharmacological investigations of central 5-HT1A receptors in man using PET.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Molecular basis for Lewis alpha(1,3/1,4)-fucosyltransferase gene deficiency (FUT3) found in Lewis-negative Indonesian pedigrees.

The Le(a) and Le(b) human blood group antigens are synthesized in tissues producing exocrine secretions; they also circulate in plasma, where they are adsorbed by erythrocytes. They are synthesized by two fucosyltransferases, encoded by Lewis (FUT3) and secretor (FUT2) loci. This genetic model has been challenged because some erythrocyte Lewis-negative individuals express Lewis antigens in saliva. To define the molecular basis of this apparent discrepancy, we sequenced FUT3 in Lewis-negative individuals. We identified two single base pair changes. One, termed L1, yields a Leu-20-->Arg substitution in the enzyme's transmembrane domain. When expressed in COS-7 cells, enzyme substrate affinities are essentially identical to those of wild type. However, the mutant enzyme is found at substantially reduced levels in transfected cells. This suggests that the L1 mutation may alter the Golgi membrane anchoring of the enzyme. It was found alone in double dose in 10 of 30 erythrocyte Lewis-negative individuals, nine of whom express Lewis antigens in saliva. Therefore, L1 can account for erythrocyte/saliva-discrepant Lewis typing results. The L2 mutation creates an Ile-356-->Lys change in the enzyme's catalytic domain and inactivates the enzyme. It was found in double dose in 18 of 19 individuals bearing the double erythrocyte and salivary Lewis deficiency and can account for this phenotype.

Alleles↗
PubMed1994

Invasive cancer of the cervix in women with mild dyskaryosis followed up cytologically.

Mildly dyskaryotic smears are common, and women with such results are often followed up with further cervical smear tests. An important consideration in evaluating this practice would be the annual incidence of invasive cervical cancer. A reanalysis of five previous studies of the cytological follow up of women with mildly abnormal smear test results was undertaken to calculate this incidence. The annual incidence of invasive cancer in these women ranged from 0 to 420 per 100,000 women years. The large studies providing the most precise estimates had annual rates of 143 to 420 per 100,000 women years. This is 16 to 47 times greater than in women aged 15-34 years in England and Wales. The average rate was 208 per 100,000 women years. Women with mild dyskaryosis are at high risk of developing invasive cervical cancer despite cytological follow up. A full appraisal of the costs and benefits of colposcopy in this situation is urgently required.

Adolescent↗
PubMed1994

Molecular basis for plasma alpha(1,3)-fucosyltransferase gene deficiency (FUT6).

While most humans express an alpha(1,3)-fucosyltransferase in plasma, 9% of individuals on the isle of Java (Indonesia) do not express this enzyme. Ninety-five percent of these plasma alpha(1,3)-fucosyltransferase-deficient individuals have Lewis negative phenotype on red cells, suggesting strong linkage disequilibrium between these two traits. To define the molecular basis for this plasma deficiency and to determine which of two candidate human alpha(1,3)-fucosyltransferase genes encode this enzyme (FUT5 and FUT6), we cloned and analyzed alleles at these two loci from an Indonesian individual deficient in plasma alpha(1,3)-fucosyltransferase activity. Single base pair changes were identified in the coding region of each gene, relative to previously published wild type alleles. These changes in turn yield three codon changes in FUT5 and three in FUT6. The codon changes in the FUT5 gene do not yield detectable diminutions in alpha(1,3)-fucosyltransferase activity when tested by expression in transfected COS-1 cells, and none of the FUT5 alleles co-segregate with plasma alpha(1,3)-fucosyltransferase deficiency in Indonesian pedigrees. By contrast, two of the codon changes in the FUT6 alleles inactivate this gene when tested by expression in transfected COS-1 cells. One of these inactivating changes is a missense mutation (Glu-247-->Lys) within the enzyme's catalytic domain. The other inactivating mutation represents a nonsense mutation (Tyr-315-->stop) that truncates the COOH terminus of the enzyme by 45 amino acids. The Glu-247-->Lys missense mutation is present in double dose in the nine plasma alpha(1,3)-fucosyltransferase-deficient individuals tested, whereas the nonsense mutation at tyrosine 315 is present in double dose in just one of these persons. These results demonstrate that the alpha(1,3)-fucosyltransferase activity in human plasma is encoded by the FUT6 gene and that the missense mutation within codon 247 of this gene is responsible for deficiency of this activity in these Indonesian families.

Alleles↗
PubMed1994

A second generation of non-peptide cholecystokinin receptor antagonists and their possible therapeutic potential.

The profile of an acidic series of benzodiazepine CCK-B receptor antagonists is described. The tetrazolyl urea derivative L-368,935 had high affinity (CCK-B IC50 0.1 nM) and was one of the most selective (CCK-B/CCK-A 10,000) CCK-B antagonists known. L-368,935 was a CCK-B antagonist with high affinity on the rat ventromedial hypothalamic slice preparation (Kb 0.6 nM) and also blocked pentagastrin-induced calcium mobilization in GH3 cells. L-368,935 had potent in vivo activity and antagonized pentagastrin-induced gastric acid secretion in the anesthetized rat and CCK-8S-induced aspartate release using microdialysis in the striatum of conscious rats. Activity within the central nervous system was confirmed by a mouse ex vivo binding assay and by direct measurement of the compound within the central nervous system using an HPLC assay. A second generation of CCK-B receptor antagonists such as L-368,935 will be important in determining the therapeutic potential of this class of compound in man.

Animals↗
PubMed1994

The effects of WAY-100135 and 8-hydroxy-2-(di-n-propylamino)tetralin on feeding in the rat.

We have examined the effects of the selective 5-HT1A receptor antagonist, WAY-100135, on feeding and on 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)-induced hyperphagia in rats. Given alone, WAY-100135 (1-10 mg/kg s.c.) did not affect the food intake of fasted or satiated rats; however, in free feeding rats, WAY-100135 (3 mg/kg s.c.) significantly attenuated 8-OH-DPAT-induced hyperphagia (0.1 mg/kg s.c.). Using a satiety sequence analysis of feeding behaviour, WAY-100135 (1 mg/kg s.c.) did not affect behaviour per se, but significantly antagonised the increased incidence of feeding, but not the decrease in observations of grooming following 8-OH-DPAT (0.1 mg/kg s.c.). These data provide the first demonstration of the antagonism, by a selective 5-HT1A receptor antagonist, of 8-OH-DPAT-induced feeding; an effect mediated via the somatodendritic 5-HT1A autoreceptor. These results also suggest that 5-HT1A receptor antagonists may have no intrinsic effect on food intake or feeding behaviour.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Assessment of epidermal dendritic cell markers and T-lymphocytes in psoriasis.

Epidermal dendritic and T-cell counts have been performed in lesional and non-lesional skin from 35 psoriatic patients. The aims were to investigate absolute changes and interrelationships between these cellular elements in psoriasis and to explain apparent discrepancies between these results and reports in the literature. In non-lesional skin, the most frequently expressed dendritic cell marker was CD1a. HLA-DR+ and alpha-mannosidase+ dendritic cells were approximately 50 per cent and S100+ cells were 25 per cent as frequent. T-lymphocytes were rare, CD4+ cells predominating. In lesional psoriatic epidermis, there was a definite increase (approximately two-fold) in the absolute number of CD1a+ dendritic cells. This differs from the conclusions from the majority of previous studies. However, when cell counts were expressed per unit area of vertical section, there was a decrease in CD1a+ cells in lesional skin, which is an explanation for this discrepancy. There was a greater increase in absolute HLA-DR+ cell counts, so that the numbers of cells expressing CD1a and HLA-DR were similar in lesional skin. S100 expression increased proportionately with CD1a+, but there was no absolute increase in alpha-mannosidase+ cells, which might represent a separate sub-population of dendritic cells. The greatest cellular increase was in T-lymphocytes, particularly CD8+. In lesional skin, direct correlations have been demonstrated between epidermal thickness, HLA-DR+ dendritic cells and T-lymphocytes, particularly CD8+ cells. We would suggest that the present method of quantification is of value for the analysis of absolute changes in epidermal infiltrates, particularly psoriasis, and could be applied to other epidermal pathologies.

Adult↗
PubMed1994

Glycosylation and functional activity of anti-D secreted by two human lymphoblastoid cell lines.

Cell lines BTSN4 and BTSN5 were produced by the Epstein-Barr Virus (EBV) transformation of B-lymphocytes from the same human donor. Both secrete an anti-D monoclonal of the IgG1 subclass but these antibodies display vastly different effector activities. Specifically, anti-D from BTSN4 has a far greater activity in both monocyte- and lymphocyte-mediated ADCC reactions and causes a higher percentage of rosettes to be formed with monocyte-like U937 cells. This variation in functional activity is shown to coincide with changes in the structure of the sugar chains attached to the asparagine-297 site on the immunoglobulin heavy chain.

Antibodies, Monoclonal↗
PubMed1994

Behavioural and pharmacological characterisation of the elevated "zero-maze" as an animal model of anxiety.

The elevated "zero-maze" is a modification of the elevated plus-maze model of anxiety in rats which incorporates both traditional and novel ethological measures in the analysis of drug effects. The novel design comprises an elevated annular platform with two opposite enclosed quadrants and two open, removing any ambiguity in interpretation of time spent on the central square of the traditional design and allowing uninterrupted exploration. Using this model, the reference benzodiazepine anxiolytics, diazepam (0.125-0.5 mg/kg) and chlordiazepoxide (0.5-2.0 mg/kg) significantly increased the percentage of time spent in the open quadrants (% TO) and the frequency of head dips over the edge of the platform (HDIPS), and reduced the frequency of stretched attend postures (SAP) from the closed to open quadrants. In contrast, the anxiogenic drug m-chlorophenyl-piperazine (mCPP; 0.25-1.0 mg/kg) induced the opposite effects, decreasing %TO and HDIPS, and increasing SAP. The 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.001-0.1 mg/kg) had no effects on either %TO or HDIPS, but did decrease SAP at 0.01 mg/kg although not at higher or lower doses. Similarly, the 5-HT3 receptor antagonist, ondansetron (0.0001-1.0 mg/kg) decreased SAP and increased %TO at 0.01 mg/kg, but not at other doses. The present data suggest that a combination of the novel "zero-maze" design and a detailed ethological analysis provides a sensitive model for the detection of anxiolytic/anxiogenic drug action.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Effect of the putative 5-HT1A antagonists WAY100135 and SDZ 216-525 on 5-HT neuronal firing in the guinea-pig dorsal raphe nucleus.

The selective 5-hydroxytryptamine1A (5-HT1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OHDPAT, 0.5-35 micrograms kg-1 i.v.) produces a dose related reversible inhibition (ED50 = 6.5 micrograms kg-1 i.v.) of the firing of serotonergic neurones in the dorsal raphe nucleus of the guinea-pig. Administration of N-tert-butyl-3- (4-(2-methoxyphenyl)piperazine-1-yl)-2phenylpropanamide dihydrochloride (WAY100135, 0.5 mg kg-1 i.v.), a specific 5-HT1A antagonist, antagonized the 8-OHDPAT induced inhibition of neuronal firing whilst methyl 4-(4-[4-(1,1,3-trioxo-2H-1,2-benzoisothiazol-2-yl)butyl]-1- piperazinyl) 1 H-indole-2-carboxylate (SDZ 216-525, 0.1-0.5 mg kg-1 i.v.) (also a putative 5-HT1A antagonist) reduced the basal firing of 5-HT neurones and furthermore failed to antagonize the inhibition produced by 8-OHDPAT. These results indicate that WAY 100135 is a silent and selective 5-HT1A antagonist whereas SDZ 216-525 demonstrates a partial agonist activity at the somatodendritic 5-HT1A autoreceptor in the guinea-pig DRN.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Molecular genetics of alpha-L-fucosyltransferase genes (H, Se, Le, FUT4, FUT5 and FUT6).

Six human alpha-L-fucosyltransferase genes have been registered in the GDB as FUT1 to FUT6 according to the chronology of their description. FUT1 and FUT2 encode the alpha(1,2)fucosyltransferases H and Se respectively. The FUT2 gene has not been cloned, but it is expected to be closely linked to FUT1 on the long arm of chromosome 19. FUT3, FUT4, FUT5 and FUT6 encode different alpha(1,3)fucosyltransferases which share between 60 and 90% homology with each other, but none with FUT1. Missense and nonsense point mutations have been found to inactivate the cognate enzymes of FUT1, FUT3 and FUT6. FUT3 and FUT6 are closely linked on the short arm of chromosome 19 and encode the Lewis and plasma enzymes respectively. The FUT5 gene has been cloned and sequenced, but its tissue expression has not been defined as yet. FUT4 has been mapped to 11q21 and encodes a monomorphic myeloid enzyme. All but FUT4 are genetically polymorphic. The deficient alleles of FUT1 and FUT6 have a very low incidence and they have been found mainly around the Indian Ocean. A myeloid enzyme is present in 5 to 10 week old human embryos and is later progressively replaced by different patterns of adult fucosyltransferase enzymes in all tissues, except in leukocytes and brain which continue to express a FUT4 like enzyme in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Fucosyltransferases↗
PubMed1994

Absence of Coxsackie viruses in idiopathic inflammatory muscle disease by in situ hybridization.

The role of coxsackie virus infection in the pathogenesis of idiopathic inflammatory muscle disease (IIMD) has been investigated by many workers with conflicting results. This study uses in situ hybridization, with digoxigenin-labelled oligonucleotide probes complementary to the coxsackie B virus genome, to investigate the presence of virus RNA in muscle biopsies from 26 patients with IIMD. In the five cases of inclusion body myositis studied, there was focal probe-binding to nuclei and cytoplasm, and in nine cases probe-binding to mast cells was seen. In both of these instances probe-binding was non-specific and not due to hybridization. None of the cases showed the presence of coxsackie virus RNA within muscle and it is concluded that lytic infection of myocytes by coxsackie virus does not occur in IIMD.

Adolescent↗
PubMed1994

Absence of Epstein-Barr virus RNA in multiple sclerosis as assessed by in situ hybridisation.

Epidemiological and serological evidence has suggested a role for Epstein-Barr virus infection in the aetiology of multiple sclerosis. Epstein-Barr virus-specific RNA was looked for in the brains of 10 patients with multiple sclerosis by in situ hybridisation. A total of 21 plaques was examined. In all of these preservation of RNA was shown by hybridisation of control probes to mitochondrial rRNA but no signal was detected with the Epstein-Barr virus probes. It is unlikely that persistent or latent Epstein-Barr virus infection of the CNS occurs in multiple sclerosis, although present findings do not exclude a role for Epstein-Barr virus in the initiation of this disorder.

Aged↗