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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 145 records · Page 8Linked to original sources
PubMed2000

Left ventricular filling patterns in patients with systemic hypertension and left ventricular hypertrophy (the LIFE study). Losartan Intervention For Endpoint.

Abnormal left ventricular (LV) filling may exist in early stages of hypertension. Whether this finding is related to LV hypertrophy is currently controversial. This study was undertaken to assess relations between abnormal diastolic LV filling and LV geometry in a large series of hypertensive patients with electrocardiographic LV hypertrophy. M-mode, 2-dimensional, and pulsed Doppler echocardiographic recordings of mitral inflow velocity and isovolumetric relaxation time (IVRT) were obtained in 750 patients with stage I to III hypertension and LV hypertrophy determined by electrocardiography (sex-adjusted Cornell voltage duration criteria or Sokolow-Lyon voltage criteria) after 14 days of placebo treatment. The patients' mean age was 67+/-7 years and 44% were women. One hundred forty patients (19%) had normal LV geometric pattern, 79 (11%) had concentric remodeling, 342 (45%) had eccentric LV hypertrophy, and 189 (25%) had concentric LV hypertrophy. A normal LV filling pattern was found in 116 patients (16%), abnormal relaxation in 519 (69%), "pseudonormal" filling was found in 83 (11%), and a restrictive filling pattern in 32 (4%). Prolonged IVRT was associated with LV hypertrophy (p<0.01) as well as elevated relative wall thickness (p<0.05). A stronger difference (p<0.01) in IVRT was found between groups with and without LV hypertrophy. Multiple regression analysis revealed that increased LV mass correlated with prolonged IVRT, whereas LV mass and geometry were not associated with peak early LV filling velocity (E), peak atrial filling velocity (A) ratio or mitral valve E-peak deceleration time, although IVRT was found to be an independent correlate of E/A ratio and deceleration time. Thus, abnormal IVRT was highly prevalent in all LV geometric subgroups among hypertensive patients with electrocardiographic LV hypertrophy, even in those with normal LV geometry determined by echocardiography. We found that IVRT differed significantly among patient groups with different LV geometric patterns, primarily because of the association of IVRT to LV mass.

Aged↗
PubMed2000

Characterisation of fatty acid multilayers using a TSM biosensor.

Thickness shear mode (TSM) biosensors have many potential applications within the pharmaceutical sciences as a means of measuring mass changes in the nanogram range, film thickness, viscosity and shear moduli. This study addresses the possible use of the TSM sensor as a biosensor for measuring drug partition coefficients. In order to realise this potential, some fundamental understanding is required of the behaviour of lipid films on the sensor. The present study characterises the behaviour of fatty acid multilayers as a suitable model chemical system. Frequency shifts and impedance spectra are presented for multilayers of three fatty acid films coated on to the sensor using a Langmuir-Blodgett trough. The results indicate that the frequency shift is non-linear at lower numbers of fatty acid layers but the response is Sauerbrey-like at higher numbers of layers. Also at high numbers of layers, changes in the impedance spectra indicate viscoelastic behaviour in thicker membranes. An inverse relationship is observed between chain length and frequency shift, which is attributed to variations in the topography of the sensor surface. This work demonstrates the importance of fully characterising the physical behaviour of the lipid multilayers prior to using these systems for the measurement of drug partition coefficients.

Biosensing Techniques↗
PubMed2000

Evidence that serine 304 is not a key ligand-binding residue in the active site of cytochrome P450 2D6.

Homology models of cytochrome P450 2D6 (CYP2D6) have identified serine 304 as an active-site residue and implicated a putative role for this residue in substrate enantioselectivity and the differential inhibition of enzyme activity by the diastereoisomers quinine and quinidine. The role of serine 304 in selectivity is thought to be achieved through a preferential hydrogen-bond interaction between the hydroxyl group of the residue and one of the stereoisomers of each ligand. We have tested this hypothesis by substituting serine 304 with alanine, a non-hydrogen-bonding residue, and compared the properties of the wild-type and mutant enzymes in microsomes prepared from yeast cells expressing the appropriate cDNA-derived enzyme. The Ser(304)Ala substitution did not alter the enantioselective oxidation of metoprolol; the O-demethylation reaction remained R-(+)-enantioselective (wild-type, R/S, 1.7; mutant, R/S, 1.6), whereas alpha-hydroxylation remained S-(-)-enantioselective (wild-type and mutant, R/S, 0.7). Similarly, the selective oxidation of the R-(+) and S-(-) enantiomers of propranolol to the major 4-hydroxy metabolite was identical with both wild-type and mutant forms of the enzyme (R/S 0.9), although the formation of minor metabolites (5-hydroxy and deisopropylpropranolol) did show some slight alteration in enantioselectivity. The differential inhibition of enzyme activity by quinine and quinidine was also identical with both forms of CYP2D6, the IC(50) values for each enzyme being approx. 10 microM and 0.1 microM for quinine and quinidine, respectively. The kinetics of formation of alpha-hydroxymetoprolol and 4-hydroxydebrisoquine by wild-type and the Ser(304)Ala mutant was also very similar. However, modest changes in the regioselective oxidation of metoprolol and debrisoquine were observed with the Ser(304)Ala mutant. The regio- and enantioselective oxidation of an analogue of metoprolol, in which the hydroxyl group attached to the chiral carbon was replaced by a methyl moiety, was again identical with both wild-type and Ser(304)Ala mutant. However, the observed selectivity was the reverse of that observed with metoprolol. Collectively, these data indicate that Ser(304) is unlikely to be a key ligand-binding residue, although the residue may indeed be located in the active-site cavity. The reversal of selectivity with the methyl analogue of metoprolol indicates that the hydroxyl group attached to the chiral centre of ligands, such as metoprolol, is important in defining the enzyme's selective properties, and that a hydrogen-bonding residue, other than Ser(304), may be involved in this interaction. Current homology models of the active site of CYP2D6 that predict a hydrogen-bond interaction between Ser(304) and specific ligands will need to be re-evaluated, and other candidate residues capable of such an interaction nominated and tested by site-directed mutagenesis studies.

Alanine↗
PubMed2000

Lack of association of the alpha2-macroglobulin locus on chromosome 12 in AD.

OBJECTIVE: Analysis of AD has revealed that the apolipoprotein E locus (APOE) cannot account for all of the genetic risk associated with AD. Whole genome scanning in AD families suggests that a chromosome 12 locus may contribute significantly to disease development. The alpha2-macroglobulin gene (A2M) has been suggested as a candidate locus for AD based on analysis of familial AD. METHOD: We determined, in 195 neuropathologically verified AD cases and 107 age-matched control subjects, the association of two common polymorphisms in A2M (a pentanucleotide deletion 5' to the bait domain exon, and a valine-1000-isoleucine polymorphism in the thiolester site of the protein). RESULTS: Evidence was observed for linkage disequilibrium between the deletion and Ile1000 polymorphisms. No evidence was observed for an association between the thiolester polymorphism and AD alone or when accounting for the APOE-epsilon4 allele. No alteration in the frequency of the bait domain deletion was observed, although a small excess (4%) of deletion homozygotes was found in the AD group, which were absent in the control population. CONCLUSIONS: The A2M deletion polymorphism at most accounts for a small fraction of the genetic contribution toward AD, and this is small compared with APOE. Furthermore, reverse transcriptase PCR of A2M RNA from the brains of patients homozygous for the deletion polymorphism showed that the bait domain exon still is present in the RNA. This suggests that the A2M deletion polymorphism may be nonfunctional and that the chromosome 12 AD locus is situated elsewhere.

Aged↗
PubMed2000

Antagonistic effects of [Nphe1]nociceptin(1-13)NH2 on nociceptin receptor mediated inhibition of cAMP formation in Chinese hamster ovary cells stably expressing the recombinant human nociceptin receptor.

Nociceptin/orphanin FQ (NC) is the endogenous ligand for the nociceptin receptor (NCR) which is negatively coupled to adenylyl cyclase to inhibit the formation of cAMP. In this study we describe the inhibitory action of the novel NC analogue, [Nphe1]nociceptin(1-13)NH2 on cAMP formation in Chinese hamster ovary cells expressing the human NCR. NC, NC(1-13)NH2, the pseudopeptides [Phe1psi(CH2-NH)Gly2]NC(1-17)NH2 and [Phe1psi(CH2-NH)Gly2]NC(1-13)NH2, the hexapeptide, acetyl-Arg-Tyr-Tyr-Arg-Trp-Lys-NH2 and buprenorphine all produced a concentration dependent inhibition of forskolin stimulated cAMP formation. This inhibition was competitively reversed by [Nphe1]NC(1-13)NH2 with essentially identical pA2 values (6.12-6.48). [Nphe1]NC(1-13)NH2 showed per se a negligible residual agonist activity (alpha < 0.15).

Animals↗
PubMed2000

Consumers' experiences of mental health policymaking.

Consumers' roles are changing from passive recipients of mental health services to active participants. The Oregon Health Plan provided an opportunity to hasten this development, which required learning by all.

Community Participation↗
PubMed2000

Purification and characterization of human alpha-galactosidase A expressed in insect cells using a baculovirus vector.

Fabry disease is an X-linked inborn error of glycolipid metabolism caused by deficiency of the lysosomal enzyme alpha-galactosidase A. The enzyme is responsible for the hydrolysis of terminal alpha-galactoside linkages in various glycolipids. To perform more extensive biochemical characterization and to develop new approaches for enzyme therapy, a method of producing and purifying recombinant alpha-galactosidase A suitable for scale-up manufacture for use in humans is needed. Previously, a catalytically active recombinant human alpha-galactosidase A was expressed using a baculovirus vector and purified using conventional chromatography. However, the level of expression was too low to permit economical production and the chromatographic techniques used for enzyme purification were not suitable for enzyme to be used in humans. Therefore, the cDNA of the enzyme was cloned to an improved baculovirus vector and the enzyme was expressed in a 15-liter bioreactor using optimized growth conditions. Infection of insect cells by the baculovirus resulted in a significant fivefold increase in the level of secreted recombinant alpha-galactosidase A activity that is compatible with economic manufacturing. The recombinant alpha-galactosidase A was purified to homogeneity using ion exchange (Poros 20-CM, Poros 20-HQ) and hydrophobic chromatography (Toso-ether, Toso-butyl) using the BioCAD HPLC workstation. These chromatographic steps are readily scalable to larger volumes and are appropriate for the purification of the recombinant human alpha-galactosidase A to be used in clinical trials of enzyme replacement therapy for Fabry disease patients.

Amino Acid Sequence↗
PubMed2000

Evaluation of biologically based dose-response modeling for developmental toxicity: a workshop report.

Biologically based dose-response (BBDR) modeling represents a novel approach for quantitative assessment of health risk by incorporating pharmacokinetic and pharmacodynamic characteristics of a chemical and by relating the immediate cellular responses to a cascade of aberrant biological actions that leads to detectable adverse outcomes. The quantitative relationship of each of the intervening events can be described in mathematical forms that are amenable for adjustment and extrapolation over a range of doses and across species. A team of investigators at the Reproductive Toxicology Division of the U.S. Environmental Protection Agency has explored the feasibility of BBDR modeling by examining the developmental toxicity of a known teratogen, 5-fluorouracil. A panel of researchers from academic and industrial laboratories, biomathematical modelers, and risk assessment scientists was convened in a workshop to evaluate the approaches undertaken by the EPA team and to discuss the future prospects of BBDR modeling. This report summarizes the lessons learned from one approach to BBDR modeling and comments from the panelists: while it is possible to incorporate mechanistic information into quantitative dose-response models for the assessment of health risks, the process is enormously data-intensive and costly; in addition, the confidence of the model is directly proportional to our current understanding of basic biology and can be enhanced only through the ongoing novel discoveries. More importantly, the extent of "uncertainty" (inherent with the default assumptions associated with the NOAEL or benchmark approach) reducible by BBDR modeling requires further scrutiny and comparison.

Abnormalities, Drug-Induced↗
PubMed2000

Approaches to sampling and case selection in qualitative research: examples in the geography of health.

This paper focuses on the question of sampling (or selection of cases) in qualitative research. Although the literature includes some very useful discussions of qualitative sampling strategies, the question of sampling often seems to receive less attention in methodological discussion than questions of how data is collected or is analysed. Decisions about sampling are likely to be important in many qualitative studies (although it may not be an issue in some research). There are varying accounts of the principles applicable to sampling or case selection. Those who espouse 'theoretical sampling', based on a 'grounded theory' approach, are in some ways opposed to those who promote forms of 'purposive sampling' suitable for research informed by an existing body of social theory. Diversity also results from the many different methods for drawing purposive samples which are applicable to qualitative research. We explore the value of a framework suggested by Miles and Huberman [Miles, M., Huberman,, A., 1994. Qualitative Data Analysis, Sage, London.], to evaluate the sampling strategies employed in three examples of research by the authors. Our examples comprise three studies which respectively involve selection of: 'healing places'; rural places which incorporated national anti-malarial policies; young male interviewees, identified as either chronically ill or disabled. The examples are used to show how in these three studies the (sometimes conflicting) requirements of the different criteria were resolved, as well as the potential and constraints placed on the research by the selection decisions which were made. We also consider how far the criteria Miles and Huberman suggest seem helpful for planning 'sample' selection in qualitative research.

Chronic Disease↗
PubMed2000

Feasibility and safety of early exercise testing using the Bruce protocol after acute myocardial infarction.

OBJECTIVE: To assess the feasibility and safety of exercise testing (ET) using a Bruce protocol (BPR) within three days of an acute myocardial infarction (AMI) with the data obtained from a prospectively managed database. BACKGROUND: Exercise testing after AMI is usually done between days 4 and 6 and often using a "low-level" protocol. Earlier testing with BPR may allow for efficient triage. METHODS: Patients were considered for early ET when off intravenous nitroglycerine with no rest angina, uncontrolled cardiac failure or arrhythmias. RESULTS: Of 300 consecutive AMI patients who underwent an ET, 216 (72.0%; M = 163, F = 53; age mean 59 +/- 0.8 SEM, range 34 to 83 years) had ET within three days of admission. There were 124 (57%) negative, 56 (26%) positive and 36 (17%) indeterminate tests. The maximum heart rate achieved was 116 +/- 1 beats/min (range 64 to 163), which was 72.2 +/- 0.8% of predicted maximum (86.6% on beta-adrenergic blocking agents at ET; exercise duration = 6.7 +/- 0.2 min). Reasons for termination: maximum effort-89 (41%); low-level test target (stage III/IV of BPR)-63 (29%); positive ST segment change-19 (9%); severe chest pain-12 (5.5%); reaching 90% predicted maximum heart rate-6 (3%); nonsustained ventricular tachycardia-1 (0.5%); other-26 (12%). Fourteen (6.5%) patients had minor complications (i.e., drop in systolic pressure, chest pain >5 min) with no cardiac arrests, AMIs or deaths. After the ET, 87 (40%) patients were discharged the same day, 73 (34%) the next day. CONCLUSIONS: The majority of ETs after an AMI can be done using the Bruce protocol within three days of admission with a very low incidence of complications. This can lead to early triage and potential cost savings.

Adult↗
PubMed2000

Upper airway reflex sensitivity following general anaesthesia for day-case surgery.

We have studied changes in upper airway reflex sensitivity following general anaesthesia using dilute ammonia vapour as a chemical stimulant in 16 patients undergoing elective laparoscopic gynaecological surgery. We measured the threshold concentration of ammonia vapour required to elicit a transient reduction of inspiratory flow caused by glottic closure, defined as a glottic stop. Measurements of upper airway reflex sensitivity and auditory reaction time were obtained before surgery, and at 60 and 120 min after recovery. Auditory reaction time was depressed significantly at 60 min but was similar to baseline values 120 min after recovery. Upper airway reflex sensitivity remained significantly reduced at 60 and 120 min despite the return of auditory reaction time to normal. The lack of correlation between upper airway reflex sensitivity and auditory reaction time suggests that central nervous system depression alone does not explain the delayed recovery in airway reactivity.

Acoustic Stimulation↗
PubMed2000

Development and characterization of expressed sequence tags for the turkey (Meleagris gallopavo) genome and comparative sequence analysis with other birds.

Twenty-one randomly selected clones from a turkey (Meleagris gallopavo) pituitary complementary DNA (cDNA) library were sequenced to develop expressed sequence tags (ESTs) for this economically important avian species whose genome is among the least understood. Primers specific for the ESTs were used to produce amplicons from the genomic DNA of turkey, chicken (Gallus gallus), guinea fowl (Numidia meleagris), pigeon (Columba domestica), and quail (Corturnix japonica). The amplicons were sequenced and analyzed for sequence variation within- and similarity among-species and with GenBank database sequences. The proportion of shared bases between the turkey sequence and the consensus sequence from each of the other species ranged from 72% to 93% between turkey and pigeon and quail and between turkey and chicken, respectively. The total number of single nucleotide polymorphisms (SNPs) observed ranged from 3 in quail to 18 in chicken out of 4898 and 5265 bases analyzed, respectively. The most frequent nucleotide variation observed was a C-->T transition. Linkage analysis of one such SNP in the backcross progeny of the East Lansing reference DNA panel, localized TUS0005, the chicken sequence derived from primers specific for turkey TUT2E EST, to chromosome 4. The ESTs reported, as well as the SNPs may provide a useful resource for ongoing efforts to develop high utility genome maps for the turkey and chicken. The primers described can also be used as a tool in future investigations directed at further understanding the biology of the guinea fowl, pigeon and quail and their relatedness to the turkey.

Animals↗
PubMed2000

A rapid one-stage whole-blood HPA-1a phenotyping assay using a recombinant monoclonal IgG1 anti-HPA-1a.

Severe neonatal alloimmune thrombocytopenia and patients with HPA-1a-specific antibodies require transfusion of HPA-1a-negative platelets. Identifying HPA-1a-negative donors requires simple and reliable typing methods. Most existing techniques use polyclonal antibodies, are time consuming and involve platelet isolation. We have used a horseradish peroxidase (HRP)-conjugated recombinant IgG1 anti-HPA-1a (CAMTRAN007) to develop a rapid and reliable enzyme-linked immunosorbent assay (ELISA), which eliminates sample preparation and reduces the incubation and wash steps associated with traditional sandwich ELISAs. The assay uses simultaneous incubation of the monoclonal antibody RFGP56 to capture GPIIbIIIa from whole blood and the recombinant IgG1 antibody to detect captured HPA-1a antigen. It allows 96 samples to be typed in less than 1 h and can be used on stored samples. Initial testing of 85 samples of known HPA-1a genotype demonstrated that HPA-1a-negative samples had OD values of < 0.266, whereas HPA-1a-positive samples had OD values of > 0.6. Testing of 1862 random donor samples in two blood centres confirmed these OD cut-off values and identified 45 HPA-1a-negative samples (2.4%), all except one giving OD values of < 0.2. The remaining HPA-1a-negative sample had an OD value of 0.303. The HPA-1a status on all the negative samples and an equivalent number of randomly selected positive samples was confirmed by flow cytometry and polymerase chain reaction with sequence-specific primers (PCR- SSP).

Antigens, Human Platelet↗
PubMed2000

Early effects of a new problem-based clinically oriented curriculum on students' perceptions of teaching.

OBJECTIVES: To compare the course experiences of medical students in a new problem-based (PBL) undergraduate medical course with those of their peers in a conventional curriculum. DESIGN: Whole class questionnaire survey using a pre-validated research instrument. SETTING: University of Liverpool, UK. SUBJECTS: First and second year medical students RESULTS: New curriculum students were more satisfied with their course when compared to their conventional course peers. Problem solving, team working and motivation scores were significantly higher amongst new course (PBL) students. New course students were more anxious about clarity of objectives and standard of work required. CONCLUSIONS: Early evidence suggests that curriculum reform from conventional teaching to a small group problem analysis programme results in improvement in student satisfaction with teaching and the development of appropriate learning skills.

Curriculum↗
PubMed2000

Prospective and retrospective memory in normal ageing and dementia: a questionnaire study.

Frequency of prospective memory and retrospective memory failures was rated on a 16-item questionnaire by 862 volunteers, from five groups: patients with Alzheimer Disease (rated by carers), carers of Alzheimer Disease patients, elderly, young, and a group of married couples. Reported memory failures were highest for Alzheimer Disease patients, and lowest for carers, with elderly and young controls in between. More prospective memory than retrospective memory failures were reported in all groups, although the difference was small for Alzheimer Disease patients who were rated near ceiling for both. Prospective memory failures of Alzheimer Disease patients were reported as more frustrating for carers than retrospective memory failures; prospective memory and retrospective memory failures frustrated Alzheimer Disease patients equally. Data from the couples indicated that there were no biases resulting from rating on behalf of someone else. These results suggest that: (1) normal ageing has no greater effect on self-reported retrospective memory than prospective memory failures, (2) the relatively small number of memory failures reported by carers may result from comparing themselves with the Alzheimer Disease patients in their care, and (3) prospective memory failures have a greater impact on the lives of the carers and are therefore more likely to be reported as early indicants of the disease.

Adolescent↗
PubMed2000

Efficacy testing of recombinant human immunodeficiency virus (HIV) gp160 as a therapeutic vaccine in early-stage HIV-1-infected volunteers. rgp160 Phase II Vaccine Investigators.

A phase II efficacy trial was conducted with recombinant human immunodeficiency virus (HIV) type 1 envelope glycoprotein gp160 (rgp160) in 608 HIV-infected, asymptomatic volunteers with CD4+ cell counts >400 cells/mm3. During a 5-year study, volunteers received a 6-shot primary series of immunizations with either rgp160 or placebo over 6 months, followed by booster immunizations every 2 months. Repeated vaccination with rgp160 was safe and persistently immunogenic. Adequate follow-up and acquisition of endpoints allowed for definitive interpretation of the trial results. There was no evidence that rgp160 has efficacy as a therapeutic vaccine in early-stage HIV infection, as measured at primary endpoints (50% decline in CD4+ cell count or disease progression to Walter Reed stage 4, 5, or 6) or secondary endpoints. A transient improvement was seen in the secondary CD4 endpoint for the vaccination compared with the placebo arm, but this did not translate into improved clinical outcome.

AIDS Vaccines↗