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Biomedical subjects

M Scott

Publications and source records attributed to M Scott.

At least 109 records · Page 6Linked to original sources
PubMed1999

HIV case loads of Australian GPs. Results of the national survey.

BACKGROUND: This paper presents national survey data concerning the management of HIV positive patients by GPs. OBJECTIVE: To examine the extent and nature of GPs' involvement in the management of patients with HIV/AIDS; to identify their needs for education and support. DISCUSSION: Some GPs have never been consulted by an HIV positive patient, some have no current cases, others have either low or higher case loads. GPs in the first two categories had difficulty maintaining interests and skills in HIV. Those with low case loads recognised limitations in HIV management, relying on the skills of consultants or specialist GPs, and rationalizing CME time according to their current patients. GPs with higher case loads tended to manage full care of their HIV positive patients, to be authorized s100 prescribers, to be members of the Australasian Society for HIV Medicine, to have attended an HIV specific CME course, and to practise in an inner urban area.

Adult↗
PubMed1998

Calcium influx via L-type voltage-gated channels mediates the delayed, elevated increases in steady-state c-fos mRNA levels in cerebellar granule cells exposed to excitotoxic levels of glutamate.

The altered kinetics of steady-state c-fos mRNA production in cultured cerebellar granule cells under excitotoxic conditions was investigated in neurons subjected to depolarising stimuli, namely, high KCl and L-glutamate (Glu), in which Ca2+ influx occurs by differing routes. Increases in intracellular-free calcium levels ([Ca2+]i) stimulated by nontoxic or toxic levels of Glu were blocked by selective N-methyl-D-aspartate (NMDA) receptor antagonism; were blocked only partially by the L-type channel blocker, nifedipine; and were unaffected by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)/kainate receptor antagonists. Glu-induced cell death was prevented only by NMDA receptor blockade. Exposure of cells to nontoxic levels of Glu resulted in a transient increase in c-fos mRNA levels, whereas an excitotoxic dose produced a delay in the appearance of c-fos mRNA but a subsequent, progressive, and sustained (>4 hr) increase. An excitotoxic dose of Glu in combination with either nifedipine or selective NMDA receptor antagonists resulted in the normal, transient increase of c-fos mRNA levels. Chronic exposure to 55 mM KCl caused no cytotoxicity, although it resulted in a delayed, elevated increase in c-fos mRNA levels that was unaffected by NMDA receptor blockade but reverted to the normal, transient profile of c-fos mRNA formation when it was coadministered with nifedipine. The KCl-induced increase in [Ca2+]i levels was inhibited dramatically by nifedipine but was unaffected by any of the ionotropic Glu receptor antagonists. The results support the notion that the appearance of a delayed but elevated increase in steady-state c-fos mRNA levels following exposure to excitotoxic doses of Glu is mediated specifically by calcium influx via L-type voltage-gated channels.

Animals↗
PubMed1998

Crystallization and preliminary X-ray analysis of a member of a new family of pectate lyases, PeIL from Erwinia chrysanthemi.

PeIL, a pectate lyase (E.C. 4.2.2.9) from E. chrysanthemi 3937 that is not homologous to the lyases with known structures, has been purified and crystallized by the hanging-drop method using a variety of organic solvents as precipitant. Elongated lathes grown from poly(ethylene glycol) plus isopropanol belong to the space group P212121 with cell dimensions a = 55.5, b = 58.2, c = 16.4 A with a single molecule in the asymmetric unit. Although complete data sets have been collected to 2.3 A resolution, these crystals diffract to at least 1.9 A resolution and are suitable for structure determination. Chunky plates grown using other organic solvents as the precipitant diffracted to 3 A resolution and were partially characterized as a second orthorhombic crystal form with space group P21212 and cell dimensions a = 119.1, b = 140.5 and c = 105.4 A, suggesting four molecules in the asymmetric unit.

Crystallization↗
PubMed1998

Crystallization and preliminary X-ray diffraction studies of a family 26 endo-beta-1,4 mannanase (ManA) from Pseudomonas fluorescens subspecies cellulosa.

Crystals of an endo-beta-1,4-mannanase (1,4-beta-D-mannohydrolase, E. C. 3.2.1.78) from Pseudomonas fluorescens sub species cellulosa have been grown by the hanging-drop technique at 291 K over a period of one to two weeks to maximal dimensions of 0.17 x 0.17 x 0.25 mm. These crystals belong to the space group R32 (or R3) with cell dimensions of a = b = 155.4 and c = 250.8 A (hexagonal setting) and contain three (six) molecules in the asymmetric unit. The crystals diffract to at least 3.2 A using a laboratory source and are suitable for structure determination.

Crystallization↗
PubMed1998

Are genetic factors important in the aetiology of leukoaraiosis? Results from a memory clinic population.

OBJECTIVE: To discover whether polymorphism in either the apolipoprotein E (ApoE) or angiotensin-converting enzyme (ACE) genes is associated with leukoaraiosis, white matter lesions visible on neuroimaging of the brain, which is commonly seen in dementia as well as some normal elderly subjects. DESIGN: Prospective study of consecutive patients attending our memory disorders clinic, to examine the relationship between leukoaraiosis and polymorphism of the ApoE and ACE genes. SETTING: Memory disorders clinic in Bristol, UK. PATIENTS: 182 patients attending the memory disorders clinic for investigation of possible dementia of whom 75% were suffering from dementia, 20% from memory impairment but no dementia and in 5% of whom a dementing illness was thought to be unlikely; 38% of all patients had visible white matter lesions and 16% had cerebral infarcts. MEASURES: Patients and/or carers who agreed to participate in the study had their ACE and ApoE genotype determined and their brain CT/MRI scans were assessed by a neuroradiologist, blind to the result of the genotyping, for the presence or absence of white matter low attenuation. RESULTS: There was a significant association between white matter lesions and the DD genotype (p < 0.05), but not the ApoE genotype. However, this relationship with the DD genotype was only significant for patients with a previous infarct. CONCLUSION: Homozygosity of ACE gene deletion polymorphism is a risk factor for white matter lesions when it is associated with cerebral infarction. This suggests that it may be possible to identify subjects who are at greater risk of developing white matter lesions and are at risk of cognitive impairment and possibly dementia.

Aged↗
PubMed1998

Effect of gender and apolipoprotein E genotype on response to anticholinesterase therapy in Alzheimer's disease.

BACKGROUND: Anticholinesterase therapies offer modest benefit to subgroups of AD sufferers. However, there has previously been no way of predicting which patients will respond to any of the drugs. OBJECTIVE: To discover if gender and/or apolipoprotein E genotype can be used as predictors of response in the clinical setting. DESIGN: 107 patients from the Bristol Memory Disorders Clinic took part in a double-blinded or open label trial of tacrine therapy for between 3 and 12 months or an open label trial of galanthamine therapy for 3 months. RESULTS: After 3 months of therapy, gender was found to be the only significant influence on the number of responders to anticholinesterase therapy. Men had a 73% greater chance of responding than women (p = 0.012). While ApoE genotype did not modify response to therapy in the short term, there are indications that it may affect response over the longer term (up to 12 months), and also that the initial advantage of male gender may not be maintained after 3 months. CONCLUSION: Gender is likely to be a more powerful determinant of outcome of anticholinesterase treatment than apolipoprotein E status in the short term.

Alzheimer Disease↗
PubMed1998

Alterations in the growth factor signal transduction pathways and modulators of the cell cycle in endocervical cells from macaques exposed to TCDD.

After more than a year had elapsed since a single oral exposure to 2 and 4 microgram 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)/kg, there was an apparent dose-related increased incidence of significant endocervical squamous metaplasia in a group of cynomolgus macaques (Scott et al., 1998). In the present experiments we investigated the mechanisms by which chemicals like TCDD could induce epithelial cell transdifferentiation in the primate endocervix. One focus of investigation was epidermal growth factor receptor (EGFR) and the key cytosolic signaling kinases, c-Src and protein tyrosine kinase (PTK), whose responses to TCDD are well characterized. A second focus was the distal kinase Erk2 that transduces the cytosolic signal into a nuclear signal, and which in combination with nuclear casein kinase II (CKII), can lead to activation of p53. Finally, we studied three key target proteins of activated p53 (wafl/p21, Cdc2 p34, and Cdk4), whose modulation could produce cell cycle effects. The studies were carried out using primary cell cultures prepared from endocervical epithelium recovered at necropsy from TCDD-treated (2 and 4 microgram TCDD/kg) and untreated macaques. There was a significant decrease in EGFR binding activity in cells from TCDD-treated animals as compared to controls. A marked increase in the protein amount of H-Ras and a significant increase in the activity of c-Src kinase, PTK, and Erk2 were found in cells from TCDD-treated animals. A significant decrease in the activity of CKII and in the protein amount of p53, wafl/p21, and Cdc2 p34 was found. On the other hand, a substantial increase in the protein amount of Cdk4 and DNA binding activity of AP-1 was found in cells from TCDD-treated animals. In vitro experiments using primary cultures of endocervical cells from untreated macaques revealed that these cells have AhR, and that c-Src protein is functionally attached to the AhR and is specifically activated upon ligand binding as judged by the following criteria. (1) A structure-activity relationship study with TCDD and three dioxin congeners revealed a rank order for their potency in activation of AhR-associated c-Src kinase from cervical cells which was identical to that of previously determined toxicity indices. (2) TCDD-induced, AhR-associated c-Src kinase activity was abolished when an AhR immunoprecipitate from cervical cells was preincubated with alpha-naphthoflavone (AhR blocker) or geldanamycin (Src kinase inhibitor) prior to the addition of TCDD. (3) The analysis of the AhR complex showed three proteins of molecular weights of 100 (AhR), 90, and 60 kDa. (4) The same protein with molecular weight 60 kDa was found when the immunoprecipitate with anti AhR-antibody was analyzed by SDS-PAGE, then transferred into nitrocellulose membrane followed by immunobloting the membrane with anti c-Src-antibody. Our data suggest that TCDD induced pathology in endocervical cells through changes in growth factor receptor signaling, other cytosolic signaling proteins, tumor suppressor proteins, and cell cycle proteins.

Animals↗
PubMed1998

Assessment of glutaraldehyde crosslinking efficiency with an amine-specific fluorescent probe.

BACKGROUND: Crosslinking of heart valves with glutaraldehyde involves the binding of amine groups. We have developed a technique that provides an inverse measure of the degree of tissue fixation by quantifying the amount of unbound amines. METHODS: Whole aortic valves were exposed to 0.5% glutaraldehyde solution for 0, 1, 15, and 60 minutes, 6 hours, and 1 and 7 days. Frozen sections were exposed to carboxyfluorescein succinimidyl ester, a fluorescent amine-reactive probe. Images were acquired from each section and processed to separate pixels representing tissue from those representing background. An average fluorescent intensity for each image was calculated and related to the number of unbound amines by comparing with standards. RESULTS: The amount of uncrosslinked amines was observed to decrease exponentially with fixation time and achieved a plateau at 1 day of fixation. A significant difference in the amount of unbound amines also exists between valve leaflets fixed while connected to the root and those excised from the root before fixation. CONCLUSIONS: This amine measurement technique, being sensitive to spatially varying differences in chemical fixation, should be useful in evaluating the efficacy of new fixation protocols.

Amines↗
PubMed1998

A comparison of methods used in species identification of coagulase-negative staphylococci isolated from the milk of sheep.

Thirty reference strains of staphylococci, 76 strains isolated from confirmed cases of subclinical mastitis and 10 strains from the teat tip skin and the mouth of sucking lambs were assigned to species using four biochemical methods. These were the commercially available micromethods API Staph and Staph-Zym; the specialized laboratory method Rosco Set and Reactions in Standard Laboratory Culture Media (SLCM). The Rosco Set assigned species to all the strains, the SLCM to 96.5%, the Staph-zym to 86.1% and the API Staph to 81.4%. API Staph and the SLCM favoured the 'aureus' group with the 'epidermidis' second, while the reverse was true for the other two methods. All the identification methods assigned the same species to only 29% of the tested isolates, causing considerable variation in the number of species identified within each group. This variation indicates that reported species prevalence from cases of ovine mastitis should be viewed with caution.

Animals↗
PubMed1998

Effect of montelukast on single-dose theophylline pharmacokinetics.

The effect of montelukast (MK-0476), a cysteinyl leukotriene receptor antagonist in development for treatment of asthma, on single-dose theophylline plasma concentrations was studied in three separate clinical trials. Montelukast was evaluated at 10 mg once daily (the clinical dosage), 200 mg once daily, and 600 mg (200 mg three times daily). At the clinical dosage, montelukast did not change single-dose theophylline plasma concentration in a clinically important manner. The geometric mean ratios for theophylline area under the plasma concentration versus time curve (AUC0-->infinity ) (0.92) and maximal plasma concentration (Cmax ) (1.04) were well within the predefined and generally accepted bioequivalence range of 0.80 and 1.25. Montelukast decreased theophylline Cmax by 12% and 10%, AUC0-->infinity by 43% and 44%, and elimination half-time by 44% and 39% at 200 mg/d (oral and intravenous, respectively), and at 600 mg/d, montelukast decreased theophylline Cmax by 25%, AUC0-->infinity by 66%, and elimination half-time by 63%. These results show that montelukast at the clinical dosage did not change theophylline pharmacokinetics in a clinically important manner, but at 20- to 60-fold higher dosages, montelukast significantly reduced the theophylline pharmacokinetics parameters; an apparent dosage dependence is suggested.

Acetates↗
PubMed1998

Moyamoya syndrome associated with congenital heart disease.

OBJECTIVE: To describe the association between moyamoya syndrome and congenital heart disease and to discuss its clinical implications. Study Design. Retrospective analysis of a case series from two institutions. RESULTS: Five patients with moyamoya syndrome and structural congenital heart disease were identified. Coarctation of the aorta was present in 3 patients, in association with a ventricular septal defect (1 patient), aortic and mitral valve stenoses (1 patient), and tetralogy of Fallot (1 patient). Tetralogy of Fallot and a large paramembranous ventricular septal defect were found in the other 2 patients. Four patients underwent surgical repair of their congenital heart disease during the first year of life and 1 patient had balloon dilation of aortic coarctation at 5 years of age. In all patients, moyamoya syndrome was diagnosed after surgical intervention for congenital heart disease-at 6 months of age in 1 patient, at 2 years of age in 3 patients, and at 6 years in 1 patient. Strokes were the most common presenting sign (3 patients) followed by seizures (2 patients). By the age of 33 months, 4 of 5 patients had undergone cerebral revascularization surgery to halt the clinical progression of moyamoya syndrome. CONCLUSIONS: Moyamoya syndrome should be considered in the differential diagnosis of seizures and stroke in patients with structural congenital heart disease. Prompt diagnosis and surgical management of the occlusive cerebral angiopathy should lead to improved neurological outcome in these patients.

Diagnosis, Differential↗
PubMed1998

[Evaluation of fragmented potentials in right bundle branch block without structural myocardium abnormalities. Study made by signal-averaged electrocardiogram on time and frequency domain].

PURPOSE: To evaluate if the presence of right bundle branch block (RBBB), without structural myocardial abnormalities (SMA) can generate fragmented potentials (FP) and spectral turbulence on signal-averaged electrocardiogram (SAECG). METHODS: Twelve children with atrial septal defect (ASD) and incomplete right bundle branch block (IRBBB without SMA (group I) were compared to 17 children with post-operative tetralogy of Fallot (TF) with CRBBB, all with SMA, 5 with ventricular premature beats and 2 with sustained ventricular tachycardia (group II). All had SAECG on time (TD) and frequency domain (FD) with 5 variables analysed. RESULTS: All patients of group I had normal variables, in contrast with group II which presented abnormal variables suggesting FP and ST. CONCLUSION: In ASD without SMA, the isolated IRBBB did not generate FP and ST.

Bundle-Branch Block↗
PubMed1998

Quality of life during acute and intermittent treatment of gastro-oesophageal reflux disease with omeprazole compared with ranitidine. Results from a multicentre clinical trial. The European Study Group.

AIMS: To investigate quality of life in patients with gastro-oesophageal reflux disease. PATIENTS: A series of 704 patients were randomised to treatment with ranitidine 150 mg bd, omeprazole 10 mg om or omeprazole 20 mg om for 2 weeks. Asymptomatic/mildly symptomatic patients were followed for 12 months. METHODS: The Psychological General Well-Being index and the Gastrointestinal Symptom Rating Scale were completed before and during short-term and intermittent treatment. RESULTS: The quality of life response rate was > 80%. The majority of the patients receiving omeprazole 20 mg om (55%) had symptom relief after 2 weeks despite the fact that more patients on ranitidine required 4 weeks' treatment and an increased dose. There was no difference in the reflux dimension of Gastrointestinal Symptom Rating Scale between treatments in the initial treatment phase, but the total Gastrointestinal Symptom Rating Scale score improved significantly more on omeprazole 10 mg om than on ranitidine 150 mg bd (p = 0.006). Both doses of omeprazole improved the total Psychological General Well-Being score more than ranitidine (omeprazole 10 mg om versus ranitidine 150 mg bd, p = 0.005, omeprazole 20 mg om versus ranitidine 150 mg bd, p = 0.031). During follow-up, relapsing patients returned to pre-treatment symptom and well-being scores, but these dimensions were restored after treatment. CONCLUSION: The quality of life is impaired in patients presenting with reflux symptoms. Irrespective of whether the patients presented with endoscopy positive or endoscopy negative reflux disease, treatment on demand improved the quality of life.

Adolescent↗
PubMed1997

Evidence for protein X binding to a discontinuous epitope on the cellular prion protein during scrapie prion propagation.

Studies on the transmission of human (Hu) prions to transgenic (Tg) mice suggested that another molecule provisionally designated protein X participates in the formation of nascent scrapie isoform of prion protein (PrPSc). We report the identification of the site at which protein X binds to the cellular isoform of PrP (PrPC) using scrapie-infected mouse (Mo) neuroblastoma cells transfected with chimeric Hu/MoPrP genes even though protein X has not yet been isolated. Substitution of a Hu residue at position 214 or 218 prevented PrPSc formation. The side chains of these residues protrude from the same surface of the C-terminal alpha-helix and form a discontinuous epitope with residues 167 and 171 in an adjacent loop. Substitution of a basic residue at positions 167, 171, or 218 also prevented PrPSc formation: at a mechanistic level, these mutant PrPs appear to act as "dominant negatives" by binding protein X and rendering it unavailable for prion propagation. Our findings seem to explain the protective effects of basic polymorphic residues in PrP of humans and sheep and suggest therapeutic and prophylactic approaches to prion diseases.

Animals↗
PubMed1997

Cloning, in vitro expression, and functional characterization of a novel human CC chemokine of the monocyte chemotactic protein (MCP) family (MCP-4) that binds and signals through the CC chemokine receptor 2B.

Here we describe the characterization of a novel human CC chemokine, tentatively named monocyte chemotactic protein (MCP-4). This chemokine was detected by random sequencing of expressed sequence tags in cDNA libraries. The full-length cDNA revealed an open reading frame for a 98-amino acid residue protein, and a sequence alignment with known CC chemokines showed high levels of similarity (59-62%) with MCP-1, MCP-3, and eotaxin. MCP-4 cDNA was cloned into Drosophila S2 cells, and the mature protein (residues 24-98) was purified from the conditioned medium. Recombinant MCP-4 induced a potent chemotactic response (EC50 = 2.88 +/- 0.15 nM) and a transient rise in cytosolic calcium concentration in fresh human peripheral blood monocytes but not in neutrophils. Binding studies in monocytes showed that MCP-4 and MCP-3 were very potent in displacing high affinity binding of 125I-MCP-1 (IC50 for MCP-4, MCP-3, and unlabeled MCP-1 of 2.1 +/- 1.4, 0.85-1.6, and 0.7 +/- 0.2 nM respectively), suggesting that all three chemokines interact with the CC chemokine receptor-2 (MCP-1 receptor). This was confirmed in binding studies with Chinese hamster ovary cells, stably transfected with the CC chemokine 2B receptor. Northern blot analysis in extracts of normal human tissues showed expression of mRNA for MCP-4 in small intestine, thymus, and colon, but the level of protein expression was too low to be detected in Western blot analysis. However, expression of MCP-4 protein was demonstrated by immunohistochemistry in human atherosclerotic lesion and found to be associated with endothelial cells and macrophages.

Amino Acid Sequence↗
PubMed1997

Association of c-fos mRNA expression and excitotoxicity in primary cultures of mouse neocortical and cerebellar neurons.

The effect of excitatory amino acids (EAAs) on c-fos mRNA expression was studied in primary cultures of mouse cerebellar granule cells and in neocortical neurons after 2 and 7 days in vitro (div). In cultured granule cells at 2 and 7 div, and in cortical neurons at 2 div, exposure to low levels (< or = 10 microM) of a variety of EAAs (viz. glutamate [Glu], S-sulpho-L-cysteine [SC], N-methyl-D-aspartate [NMDA], alpha-amino-3-hydroxy-5-methyl-4-isoxazole [AMPA], and kainate [KA]) resulted in a transient increase in the level of c-fos mRNA which peaked at 30 min but returned to a basal level by 120 min. However, exposure of granule cells (7 div) to high levels (250 microM) of Glu, NMDA, KA, SC and of cortical neurons (7 div) to high levels (250 microM) of Glu, NMDA, KA, SC, or AMPA and to low levels (< or = 10 microM) of Glu and AMPA resulted in a delay in c-fos mRNA induction but a subsequent, progressive increase that was sustained for at least 240 min. Furthermore, this effect was accompanied by a dose-related increase in the release of the cytosolic enzyme, lactate dehydrogenase, used as an indicator of excitotoxicity. A ratio (Q240/30) for the steady-state levels of c-fos mRNA after 30 min and 240 min of exposure to EAAs was determined which showed that Q240/30 >2 correlated reproducibly with excitotoxic cell death, whereas a ratio of < or = 1 correlated with a nonexcitotoxic event. In both cell types at 7 div, coadministration of the selective NMDA receptor antagonist, DL(+/-)-2-amino-5-phosphonopentanoic acid (APV) with cytotoxic levels of Glu 1) protected against EAA-induced neurotoxicity and 2) exhibited a transient c-fos mRNA expression (Q240/30 values approximately 1). In contrast, the AMPA/KA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), provided no protection against excitotoxicity and had no significant effect on the Glu-induced delay in c-fos mRNA expression. These results suggest that the Q240/30 c-fos mRNA ratio may 1) be used as a predictive index for excitotoxic neuronal death, 2) provide information on the identity of the receptor subtype mediating excitotoxicity in different brain cell types, and 3) aid in establishing the role of excitotoxicity during the development of neurons in vitro.

6-Cyano-7-nitroquinoxaline-2,3-dione↗