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Biomedical subjects

D Smith

Publications and source records attributed to D Smith.

At least 271 records · Page 15Linked to original sources
PubMed2000

Evaluation of novel assays in clinical chemistry: quantification of plasma total homocysteine.

BACKGROUND: There is a need for systematic evaluation of methods before their release to the market. We addressed this problem in novel homocysteine assays as part of an European Demonstration Project involving six centers in four countries. METHODS: Two immunological methods for measurement of plasma total homocysteine (P-tHcy), the fluorescence polarization immunoassay (FPIA) and the enzyme immunoassay (EIA), were compared with two comparison methods, HPLC and gas chromatography-mass spectrometry (GC-MS). All laboratories performed the following procedures: (a) familiarization; (b) determination of linearity and precision by analyzing five plasma samples with interrelated concentrations for 20 days; (c) correlation using patients' samples; and (d) assessment of long-term performance. RESULTS: Both immunological methods were linear for P-tHcy between 5 and 45 micromol/L. The intralaboratory imprecision (CV) was <5% for FPIA and <9% for EIA used with a sample processor. The bias was -2% to 3% for FPIA and 2-4% for EIA used with a sample processor. CONCLUSIONS: The immunological methods provide results with little bias compared with HPLC and GC-MS. The imprecision of the assays must be considered in the context of their intended use(s).

Fluorescence Polarization Immunoassay↗
PubMed2000

Lymphadenopathy in children and adolescents: role of fine-needle aspiration in management.

This study was undertaken to assess the role of fine-needle aspiration biopsy in the evaluation of palpable peripheral lymphadenopathy in pediatric and adolescent patients. A 15-year experience in aspiration of patients younger than age 21 was reviewed. These cases were taken from four large university hospitals and clinics. Data included clinical information, anatomic site, cytologic diagnosis, and any follow-up surgical excision at these institutions. From a total of 1,302 lymph node fine-needle aspirates, a subset of 106 aspirates from patients 21 years or younger was selected. This group formed the basis for this study, and these aspirates were obtained from 103 patients. Most of these aspirates (88.7%) were from the head and neck; 11 were from sites other than head and neck; and the site was not stated in one case. One hundred and one of the aspirates produced adequate samples, and only five (4.72%) were unsatisfactory. Of the 106 fine-needle aspirates, 88 (83.0%) were diagnosed as negative for malignancy, five (4.7%) were inconclusive, and three (2.8%) were interpreted as suspicious but not diagnostic of malignancy. Five cases (4.7%) were diagnosed as positive for malignancy, including two cases of metastatic papillary carcinoma of the thyroid, two cases of Hodgkin's disease, and a single case of high-grade non-Hodgkin's lymphoma. No false-positive or false-negative diagnoses occurred, excluding the aspirates classified as inconclusive or suspicious but not diagnostic of malignancy (six cases). Results of aspirates from near adolescent and adolescent patients (ages 11-21 years) were compared with those of younger pediatric patients (age < 10 years). Eighty-one (76%) of the 106 aspirates were obtained from the older group. The percentage of unsatisfactory specimens was smaller and the percentage of inconclusive or suspicious or malignant diagnoses was greater in the older group. Fine-needle aspiration biopsy is reliable in the evaluation of palpable peripheral lymphadenopathy. As most fine-needle aspirates in children and adolescents proved to indicate benign reactive conditions that failed to respond to antibiotics rather than proving to be malignant tumors, we advocate a larger role for the fine-needle aspiration biopsy technique in the evaluation of peripheral lymphadenopathy in this age group. Its early use can direct further testing, saving time, expense, and morbidity for the patient and reducing anxiety for the parents.

Adolescent↗
PubMed2000

Web reports.

Explore the source record for details and available documents.

Critical Care↗
PubMed2000

Utilisation of computerised clinical guidance in general practice consultations.

This paper reports on the results of a series of focus groups held during the Phase 1 pilot intervention period of a NHS decision-support system (Prodigy), which aims to offer contextual clinical guidance in general practice consultations. The aim of the focus groups was to collect qualitative data about users' interaction with the pilot system as part of a wider evaluation.

Attitude to Computers↗
PubMed2000

Cardiovascular disease: a historic perspective.

Cardiovascular disease (CVD) is the leading cause of death and disability in the United States and in most industrialized nations. Major breakthroughs to modern day cardiovascular/lipid research have been attributed to the findings of the Framingham Heart Study and Gofman and colleagues who made associations between lipoprotein levels (LDL, VLDL and HDL) and CVD. Unfortunately, half of all CVD patients have none of the established coronary risk factors (hypertension, hypercholesterolemia, cigarette smoking, diabetes mellitus, obesity) and new strategies for identifying patients need be considered. Although there remains little disagreement regarding the necessity to lower elevated plasma cholesterol levels, there remains much controversy regarding appropriate dietary means of accomplish this goal. The National Cholesterol Education Program (1993) proposed a dietary reduction (Step I and Step II diets) to the percent saturated fat and cholesterol consumed by at-risk patients. Many currently question about the effectiveness of these diets and an alternative diet, replacing saturated fats by monounsaturated fats (olive oil), has attracted recent attention. While diet modification is considered the foundation of primary treatment, other interventions are frequently required. Although early drug trials demonstrated that agents such as nicotinic acid, clofibrate, gemfibrozil, bile acid-binding resins generally slowed progression of atherosclerotic lesions, lowered plasma cholesterol levels and decreased mortality from CVD, the greatest advance to current drug therapy involved the discovery of the "statins" (HMG-CoA reductase inhibitors). In the current work, mechanisms for vascular dysfunction resulting in myocardial ischemia were explored and potential nutritional (dietary) and pharmacologic interventions were reviewed.

Arteriosclerosis↗
PubMed1999

Severe adverse life events and depressive symptoms among women with, or at risk for, HIV infection in four cities in the United States of America.

OBJECTIVE: To examine frequency and predictors of severe adverse life events and depressive symptoms among HIV-infected women and a comparison group of uninfected women. DESIGN: Analysis of baseline data collected from HIV-infected and uninfected women in a prospective cohort study of HIV infection and women, the HIV Epidemiologic Research Study. METHOD: The sample of 871 HIV-infected and 439 demographically and behaviorally similar uninfected women were recruited from four metropolitan areas in the USA. Women provided interview information that included sociodemographic characteristics, sexual and drug-using behaviors, and social and psychological functioning. The outcome measures were number of severe adverse life events (e.g., insufficient money for necessities, physical attack or rape, death of a person close to them) and levels of depressive symptoms. RESULTS: HIV-infected and uninfected women reported numerous adverse life events and high levels of depressive symptoms. The two groups, however, did not differ on either outcome measure. Low socio-economic status, injecting drug and crack cocaine use, and high risk sexual activity were related to reports of more adverse events and depressive symptoms for both groups. CONCLUSIONS: HIV-infected and uninfected women in socially and economically disadvantaged environments experience many adverse events and high levels of depressive symptoms. HIV infection, at least during the early phase, may be less important than socio-environmental factors in predicting negative psychosocial outcomes for women.

Adolescent↗
PubMed1999

Differential activity of soluble versus cellular Fas ligand: regulation by an accessory molecule.

Fas ligand induces apoptosis by binding to its receptor Fas. This process has been shown to be important for activation-induced cell death of T lymphocytes, homeostasis of T cell numbers, cytotoxicity, and the maintenance of immunological privilege. Fas ligand is a type II membrane protein that is cleaved by a metalloproteinase to produce an active, soluble molecule. It has been found that a variety of target cells are differentially sensitive to soluble and membrane-associated forms of Fas ligand. However, the explanation for this differential activity has not been determined. One proposed explanation for this differential activity is that membrane-associated Fas ligand is more efficiently aggregated than soluble Fas ligand. Another possibility that we have investigated is that accessory molecules may act to enhance the activity of cellular Fas ligand. We have transfected cells to express membrane-associated Fas ligand and have characterized clones of these transfected cells in terms of Fas ligand and ICAM-1 surface expression. Enhanced activity was associated with enhanced levels of both Fas ligand and ICAM-1. Moreover, inhibition of ICAM-1 modulated the activity of membrane-associated Fas ligand so that its cellular specificity was similar to that of soluble Fas ligand. Thus, ICAM-1 plays a significant role in regulating Fas ligand activity, and this role explains, at least in part, the different functional attributes of the soluble versus the cell-associated molecule.

Antigens, CD↗
PubMed1999

Competitive, reversible inhibition of cytosolic phospholipase A2 at the lipid-water interface by choline derivatives that partially partition into the phospholipid bilayer.

Cytosolic phospholipase A2 (cPLA2) catalyzes the selective release of arachidonic acid from the sn-2 position of phospholipids and is believed to play a key cellular role in the generation of arachidonic acid. When assaying the human recombinant cPLA2 using membranes isolated from [3H]arachidonate-labeled U937 cells as substrate, 2-(2'-benzyl-4-chlorophenoxy)ethyl-dimethyl-n-octadecyl-ammonium chloride (compound 1) was found to inhibit the enzyme in a dose-dependent manner (IC50 = 5 microM). It was over 70 times more selective for the cPLA2 as compared with the human nonpancreatic secreted phospholipase A2, and it did not inhibit other phospholipases. Additionally, it inhibited arachidonate production in N-formyl-methionyl-leucyl-phenylalanine-stimulated U937 cells. To further characterize the mechanism of inhibition, an assay in which the enzyme is bound to vesicles of 1,2-dimyristoyl-sn -glycero-3-phosphomethanol containing 6-10 mol % of 1-palmitoyl-2-[1-14C]arachidonoyl-sn-glycero-3-phosphocholine was employed. With this substrate system, the dose-dependent inhibition could be defined by kinetic equations describing competitive inhibition at the lipid-water interface. The apparent equilibrium dissociation constant for the inhibitor bound to the enzyme at the interface (KI*app) was determined to be 0.097 +/- 0.032 mol % versus an apparent dissociation constant for the arachidonate-containing phospholipid of 0.3 +/- 0.1 mol %. Thus, compound 1 represents a novel structural class of inhibitor of cPLA2 that partitions into the phospholipid bilayer and competes with the phospholipid substrate for the active site. Shorter n-alkyl-chained (C-4, C-6, C-8) derivatives of compound 1 were shown to have even smaller KI*app values. However, these short-chained analogs were less potent in terms of bulk inhibitor concentration needed for inhibition when using the [3H]arachidonate-labeled U937 membranes as substrate. This discrepancy was reconciled by showing that these shorter-chained analogs did not partition into the [3H]arachidonate-labeled U937 membranes as effectively as compound 1. The implications for in vivo efficacy that result from these findings are discussed.

Arachidonic Acid↗
PubMed1999

Circadian regulation of cAMP response element-mediated gene expression in the suprachiasmatic nuclei.

A program of stringently-regulated gene expression is thought to be a fundamental component of the circadian clock. Although recent work has implicated a role for E-box-dependent transcription in circadian rhythmicity, the contribution of other enhancer elements has yet to be assessed. Here, we report that cells of the suprachiasmatic nuclei (SCN) exhibit a prominent circadian oscillation in cAMP response element (CRE)-mediated gene expression. Maximal reporter gene expression occurred from late-subjective night to mid-subjective day. Cycling of CRE-dependent transcription was not observed in other brain regions, including the supraoptic nucleus and piriform cortex. Levels of the phospho-active form of the transcription factor CREB (P-CREB) varied as a function of circadian time. Peak P-CREB levels occurred during the mid- to late-subjective night. Furthermore, photic stimulation during the subjective night, but not during the subjective day, triggered a marked increase in CRE-mediated gene expression in the SCN. Reporter gene experiments showed that activation of the p44/42 mitogen-activated protein kinase signaling cascade is required for Ca2+-dependent stimulation of CRE-mediated transcription in the SCN. These findings reveal the CREB/CRE transcriptional pathway to be circadian-regulated within the SCN, and raise the possibility that this pathway provides signaling information essential for normal clock function.

Animals↗