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Biomedical subjects

A Wells

Publications and source records attributed to A Wells.

At least 37 records · Page 2Linked to original sources
PubMed2001

Effect of elevated concentration of alkaline phosphatase on cardiac troponin I assays.

Troponin I is the regulatory subunit of troponin complex associated with the actin thin filament within muscle cells. Cardiac troponin I (cTnI) is a good marker for diagnosis of myocardial damage. Several immunoassays are available for determination of cTnI in serum. The Stratus cTnI fluorometric enzyme immunoassay (Dade International) uses alkaline phosphatase (ALP) substrate. The microparticle enzyme immunoassay (MEIA) for cTnI (Abbott Laboratories) also uses ALP conjugate. On the other hand, the chemiluminescent assay (CLIA) for cTnI (Bayer Diagnostics) does not use ALP. ALP activity may frequently be elevated in serum of patients being evaluated for suspected myocardial infarction. Therefore, we studied the potential interference of ALP in cTnI assays. Serum pools were prepared from patients, and various concentrations of ALP solution were added to different aliquots. The cTnI concentrations were measured by the Stratus, MEIA, and CLIA assays. We observed no interference of ALP in the MEIA and CLIA assay for cTnI. On the other hand, we observed significant positive interference of ALP when cTnI concentrations were measured using the Stratus.

Alkaline Phosphatase↗
PubMed2001

Negative interference of bilirubin and hemoglobin in the MEIA troponin I assay but not in the MEIA CK-MB assay.

Troponin I is a sensitive and specific marker for the diagnosis of myocardial infarction. Several commercially available immunoassays measure the concentration of troponin I in serum. The microparticle enzyme immunoassay (MEIA) for troponin I (Abbott Laboratories, Abbott Park, IL) is widely used in clinical laboratories, including our hospital laboratory. We studied the effect of bilirubin and hemolysis on the MEIA for troponin I and compared our assay with a newly available chemiluminescent assay (CLIA) for troponin I (Bayer Diagnostics, Tarrytown, NY). We also measured CK-MB concentration using the MEIA CK-MB assay. One serum pool was prepared by combining several specimens of one patient with elevated troponin I and with a diagnosis of myocardial infarction. Other serum pools were prepared by combining sera with similar troponin I values. All serum pools showed normal bilirubin concentrations and had no hemolysis. Then we supplemented aliquots of serum pools with various concentrations of bilirubin (5.0, 10.0, 15.0, and 20.0 mg/dL). After supplementation, troponin I concentrations were measured again using the MEIA and CLIA. We observed a statistically significant decrease in troponin I concentration in the presence of bilirubin with the MEIA. For example, in serum pool 1, the troponin I concentration was 16.3 (bilirubin: 0.8 mg/dL). In the presence of 5.0, 10.0, 15.0 and 20.0 mg/dL of added bilirubin, the cardiac troponin I concentrations were 13.9, 13.4, 13.3 and 13.0 ng/ml respectively. We observed similar negative interference of bilirubin in troponin I measurement by the MEIA in other pools. The troponin I value decreased slightly (not statistically significant) in one pool and did not change in two other pools in the presence of bilirubin when we measured troponin I concentration using the CLIA. Interestingly, bilirubin did not interfere with the MEIA CK-MB assay. Moderate hemolysis did not have any effect on the troponin I assay using either the MEIA or CLIA. However, gross hemolysis (hemoglobin > 40 mg/dL) interfered with both assays for troponin I.

Bilirubin↗
PubMed2001

Tumor invasion as dysregulated cell motility.

Investigations across a range of disciplines over the past decade have brought the study of cell motility and its role in invasion to an exciting threshold. The biophysical forces proximally involved in generating cell locomotion, as well as the underlying signaling and genomic regulatory processes, are gradually becoming elucidated. We now appreciate the intricacies of the many cellular and extracellular events that modulate cell migration. This has enabled the demonstration of a causal role of cell motility in tumor progression, with various points of 'dysregulation' of motility being responsible for promoting invasion. In this paper, we describe key fundamental principles governing cell motility and branch out to describe the essence of the data that describe these principles. It has become evident that many proposed models may indeed be converging into a tightly-woven tapestry of coordinated events which employ various growth factors and their receptors, adhesion receptors (integrins), downstream molecules, cytoskeletal components, and altered genomic regulation to accomplish cell motility. Tumor invasion occurs in response to dysregulation of many of these modulatory points; specific examples include increased signaling from the EGF receptor and through PLC gamma, altered localization and expression of integrins, changes in actin modifying proteins and increased transcription from specific promoter sites. This diversity of alterations all leading to tumor invasion point to the difficulty of correcting causal events leading to tumor invasion and rather suggest that the underlying common processes required for motility be targeted for therapeutic intervention.

Cell Adhesion↗
PubMed2001

Brief cognitive therapy for social phobia: a case series.

Social phobia is a common and disabling anxiety disorder. The most effective psychological treatments for social phobia are cognitive therapy and exposure. However, the degree of improvement across these treatments is variable, and their implementation is costly and time-consuming. This study aimed to conduct a preliminary clinical evaluation of the effectiveness of a brief, new form of cognitive therapy based on a recent cognitive model of social phobia. Six consecutively referred patients with social phobia were treated using established single case series methodology. Brief cognitive therapy was effective with all patients demonstrating clinically significant improvements in all measures. Treatment gains were maintained at follow-up. The mean number of treatment sessions delivered was 5.5 and improvements compare favourably with previous treatment studies. Brief cognitive therapy for social phobia appears promising and it is potentially cost-effective. Future randomised and controlled evaluations of this brief treatment are warranted.

Adolescent↗
PubMed2001

Social phobic interoception: effects of bodily information on anxiety, beliefs and self-processing.

It has been suggested that body-state information influences self-perception and negative thinking in social phobia [Clark, D. M., & Wells, A. (1995). A cognitive model of social phobia. In R. G. Heimberg, M. R. Liebowitz, D. A. Hope & F. R. Schneier (Eds.), Social phobia: diagnosis, assessment and treatment (pp. 69-93). New York: Guilford Press.]. This study explored the effects of body-state information on anxiety and cognition in patients with generalised social phobia during a feared social interaction. It was hypothesised that information concerning an increase in pulse rate would lead to increments in anxiety, negative beliefs and self-processing whilst information concerning a decrease in pulse rate would have the opposite effect. The results of this study were generally consistent with the hypotheses. These findings are important as they may help to account for fluctuations in anxiety, negative beliefs and self-processing in social situations that do not present objective social threat. In particular, social anxiety appears to be modulated by body-state information. The implications of the present findings for cognitive therapy of social phobia are briefly discussed.

Adolescent↗
PubMed2001

Digitoxin-like immunoreactivity in sera of mice after feeding with chinese medicine Chan Su: study of protein binding of Chan Su in normal sera, uremic sera and sera from patients with liver disease.

Traditional Chinese medicines are readily available without prescription from herbal drug stores. One such Chinese medicine, Chan Su, which is prepared from the skin gland of toads, has cardiotonic effect due to bufadienolides. Here we report rapid detection of the presence of Chan Su in blood using the fluorescence polarization immunoassay for digitoxin. In our study mice were fed with a dose of 75 mg/kg of Chan Su and blood was drawn before, and 1 and 2 h after feeding. We observed significant digitoxin-like immunoreactivity in the sera. For example in one mouse the digitoxin-like immunoreactivity was undetectable before feeding with Chan Su, but was 19.7 ng/ml 1 h and 8.8 ng/ml 2 h afterwards. The apparent half-life of Chan Su is approximately 1 h in mice. In another experiment, we studied protein binding of Chan Su by measuring total and free Chan Su concentrations (ultrafiltrate prepared by using Centrifree Micropartition Filter, molecular weight cutoff: 30000 Da). Chan Su was strongly bound to serum proteins. We observed higher free fraction in uremic sera and sera from patients with liver disease. We identified albumin as one of the proteins that bind Chan Su in serum.

Animals↗
PubMed2001

Comparison of BD Vacutainer SST Plus Tubes with BD SST II Plus Tubes for common analytes.

Serum separator tubes were introduced 25 years ago and are widely used in the clinical laboratory today for routine collection of blood. These tubes have gained widespread acceptance due to the advantage of the barrier gel that facilitates rapid separation of serum from cellular constituents of blood and thus reduces hemolysis. However, there are some limitations associated with gel tubes (i.e., gel stability and analyte incompatibilities). The serum separator BD SST tubes manufactured by BD are widely used in clinical laboratories. Recently, BD has developed a new barrier gel, which is superior to the existing gel. We studied the stability of common analytes when serum specimens were stored in the new BD SST II tubes by comparing the performance with the existing BD SST tubes. We did not observe any significant reduction in concentrations of 42 commonly ordered analytes using the new BD SST II tubes. Significant differences were noted at low serum volumes for estradiol in both tube types over time. We conclude that the new BD SST II tubes are suitable for collection of blood and storage of serum for commonly ordered laboratory tests.

Equipment and Supplies↗
PubMed2001

Angiotensin and angiotensin receptors in cartilaginous fishes.

In mammals, a principal bioactive component of the renin-angiotensin system (RAS), angiotensin II (ANG II), is known to be vasopressor, dipsogenic, a stimulant of adrenocortical secretion and to control glomerular and renal tubular function. Historically, a RAS analogous to that found in mammals was thought to have first evolved in the bony fishes. Recent research has identified the unusually structured elasmobranch [Asp(1)-Pro(3)-Ile(5)] ANG II. Physiological studies have demonstrated that ANG II in elasmobranchs is vasopressor, and stimulates interrenal gland production of the elasmobranch corticosteroid 1alpha-hydroxycorticosterone. The specific binding of ANG II in elasmobranchs has been reported in gills, heart, interrenal gland, gut and rectal gland. The precise osmoregulatory role ANG II plays in cartilaginous fishes is not yet known; however, putative evidence is emerging for a role in the control of drinking rate, rectal gland secretion, and kidney function.

Adrenal Cortex↗
PubMed2001

Uremic sera contain inhibitors that block digitoxin-valproic acid interaction.

BACKGROUND: Digitoxin and valproic acid show strong binding to serum albumin. Thus, when present simultaneously in serum, digitoxin and valproic acid compete for binding sites. We studied digitoxin-valproic acid interaction in normal and uremic sera. METHODS: Fluorescence polarization immunoassays were used for measuring total digitoxin and total valproic acid concentrations. We used a modified protocol of improved sensitivity to measure free digitoxin concentrations. We supplemented 2 normal and 2 uremic pools with digitoxin and then aliquots of these pools were further supplemented with various concentrations of valproic acid. After incubation at 37 degrees C for 2 hours in a water bath, specimens were allowed to re-equilibrate at room temperature for 20 minutes. Free digitoxin concentrations were measured. We also investigated digoxin-valproic acid interaction using 1 normal and 1 uremic serum pool. RESULTS: We observed significant increases in free digitoxin concentrations in normal sera in the presence of valproic acid. In contrast, we observed a slight decline in free digitoxin concentration in the presence of valproic acid in uremic sera. We speculated that uremic sera contained inhibitors that block digitoxin-valproic acid interaction and identified indoxyl sulfate as an inhibitor. However, another uremic compound, hippuric acid showed no inhibitory effect. Interestingly, we observed no significant interaction between digoxin and valproic acid in either normal or uremic serum pool. This is probably because of poor protein binding of digoxin. CONCLUSION: We conclude that valproic acid significantly displaces digitoxin from protein binding sites in normal serum. However, uremic sera contain inhibitors that block digitoxin-valproic acid interaction.

Anticonvulsants↗
PubMed2001

Stability of therapeutic drugs in serum collected in vacutainer serum separator tubes containing a new gel (SST II).

The stability of therapeutic drugs in sera collected in Becton-Dickinson Vacutainer serum separator SST tubes has been well studied. Although most therapeutic drugs are stable, certain drugs such as phenytoin, carbamazepine, and phenobarbital decrease in concentrations over a long storage time. To circumvent this problem, Becton-Dickinson devised a new gel formulation. The authors studied the stability of 14 commonly monitored drugs in sera when stored on the new gel of the SST II tubes and compared the concentrations of drugs in sera stored in plain tubes (no gel), those stored in the old SST tubes, and those stored in the SST II tubes containing a new serum separator gel. The concentrations of most drugs studied did not decline even after 24 hours of storage in SST II tubes. After storage for 7 days in SST II tubes, the concentration of carbamazepine declined by 10% and that of phenytoin decreased by 4%. This is a significant improvement over the existing tube, where concentrations of several drugs declined with prolonged storage. The authors conclude that new SST II tubes are effective in collecting blood for therapeutic drug monitoring.

Blood Specimen Collection↗
PubMed2001

Digoxin-like and digitoxin-like immunoreactive substances in elderly people. Impact on therapeutic drug monitoring of digoxin and digitoxin concentrations.

We compared digoxin-like (DLIS) and digitoxin-like (DTLIS) immunoreactive substance concentrations for 30 people older than 65 years with those for 25 people younger than 50. None received digoxin or had liver disease, uremia, or volume expansion. We found no DTLIS in any specimen, and only 1 specimen from an elderly person demonstrated a low DLIS concentration. In addition, for 22 non-volume expanded patients (8 younger than 50 years and 14 older than 65) receiving digoxin, the fluorescence polarization (FPIA) and the microparticle enzyme (MEIA) immunoassays revealed comparable serum digoxin concentrations, indicating an insufficient DLIS concentration to interfere with digoxin immunoassay results. Therefore, elderly people who are not volume expanded do not have elevated DLIS or DTLIS concentrations. Furthermore, for patients with liver disease or uremia (18 older than 65 years and 20 younger than 50), the DLIS and DTLIS concentrations were elevated. Finally, for 5 patients with liver disease who received digoxin, serum digoxin concentrations were lower by MEIA and higher by FPIA, indicating the patients had elevated DLIS levels that interfered with the assays. Elevated DLIS and DTLIS concentrations are associated with volume expansion and not age.

Aged↗
PubMed2001

An experimental investigation of thought suppression and anxiety in children.

OBJECTIVES: This study aimed to explore the effects of thought suppression in children--in particular, whether trying to suppress a thought leads to an immediate and/or delayed increase in its occurrence. The influence of anxiety on children's performance in the experimental paradigm was also examined. DESIGN: Participants were allocated to conditions in a between-groups experimental design devised on the basis of thought suppression methodologies reported in the adult literature. METHODS: One-hundred and twelve participants were recruited from local primary schools and randomly allocated to four experimental conditions. Children in all conditions monitored the occurrence of a target thought (either neutral or anxiety-provoking) by tapping their hand on a table each time the thought came to mind during two consecutive experimental periods. During the first period, half the children were asked not to think about the target thought, while the remaining half were asked to think about anything. During the second period, all children were instructed to think about anything. RESULTS: No evidence was found for either an immediate or a delayed increase in frequency of target thoughts as a consequence of suppression attempts. State and trait anxiety were, however, found to influence children's performance during these experimental tasks and were associated with increased intrusions under certain conditions. CONCLUSIONS: The results of this study suggest that the experimental thought suppression paradigm is workable with 7-11-year-old children. The methodological, theoretical and clinical implications of these findings are discussed.

Adolescent↗
PubMed2000

Localized biphasic changes in phosphatidylinositol-4,5-bisphosphate at sites of phagocytosis.

Phagocytosis requires localized and transient remodeling of actin filaments. Phosphoinositide signaling is believed to play an important role in cytoskeletal organization, but it is unclear whether lipids, which can diffuse along the membrane, can mediate the focal actin assembly required for phagocytosis. We used imaging of fluorescent chimeras of pleckstrin homology and C1 domains in live macrophages to monitor the distribution of phosphatidylinositol-4,5-bisphosphate (4,5-PIP(2)) and diacylglycerol, respectively, during phagocytosis. Our results reveal a sequence of exquisitely localized, coordinated steps in phospholipid metabolism: a focal, rapid accumulation of 4,5-PIP(2) accompanied by recruitment of type Ialpha phosphatidylinositol phosphate kinase to the phagosomal cup, followed by disappearance of the phosphoinositide as the phagosome seals. Loss of 4,5-PIP(2) correlated with mobilization of phospholipase Cgamma (PLCgamma) and with the localized formation of diacylglycerol. The presence of 4, 5-PIP(2) and active PLCgamma at the phagosome was shown to be essential for effective particle ingestion. The temporal sequence of phosphoinositide metabolism suggests that accumulation of 4,5-PIP(2) is involved in the initial recruitment of actin to the phagocytic cup, while its degradation contributes to the subsequent cytoskeletal remodeling.

Actins↗
PubMed2000

Epidermal growth factor and membrane trafficking. EGF receptor activation of endocytosis requires Rab5a.

Activated epidermal growth factor receptors recruit various intracellular proteins leading to signal generation and endocytic trafficking. Although activated receptors are rapidly internalized into the endocytic compartment and subsequently degraded in lysosomes, the linkage between signaling and endocytosis is not well understood. Here we show that EGF stimulation of NR6 cells induces a specific, rapid and transient activation of Rab5a. EGF also enhanced translocation of the Rab5 effector, early endosomal autoantigen 1 (EEA1), from cytosol to membrane. The activation of endocytosis, fluid phase and receptor mediated, by EGF was enhanced by Rab5a expression, but not by Rab5b, Rab5c, or Rab5a truncated at the NH(2) and/or COOH terminus. Dominant negative Rab5a (Rab5:N34) blocked EGF-stimulated receptor-mediated and fluid-phase endocytosis. EGF activation of Rab5a function was dependent on tyrosine residues in the COOH-terminal domain of the EGF receptor (EGFR). Removal of the entire COOH terminus by truncation (c'973 and c'991) abrogated ligand-induced Rab5a activation of endocytosis. A "kinase-dead" EGFR failed to stimulate Rab5a function. However, another EGF receptor mutant (c'1000), with the kinase domain intact and a single autophosphorylation site effectively signaled Rab5 activation. These results indicate that EGFR and Rab5a are linked via a cascade that results in the activation of Rab5a and that appears essential for internalization. The results point to an interdependent relationship between receptor activation, signal generation and endocytosis.

Animals↗
PubMed2000

Mathematical modeling of epidermal growth factor receptor signaling through the phospholipase C pathway: mechanistic insights and predictions for molecular interventions.

Combining engineering analyses and mathematical modeling with intervention and detection methodologies at the molecular level will allow manipulation of intracellular signal transduction pathways, and therefore rational control of functional processes central to medicine and biotechnology. We have formulated a simple mathematical model of a key signaling pathway required for regulated migration of fibroblasts and other cell types: activation of the intracellular enzyme phospholipase C (PLC) mediated by epidermal growth factor receptor (EGFR) and a multitude of other transmembrane receptors. One of the interesting features of this pathway is that the substrate of PLC, the lipid phosphatidylinositol (4,5)-bisphosphate (PIP(2)), is turned over quite rapidly and must be constantly resupplied to the plasma membrane by a known transfer mechanism. The model, which accounts for regulation of PIP(2) concentration, is sufficiently detailed to explain unique quantitative features of recent experimental data. We find that competitive pathways that deplete PIP(2) from the membrane, as well as receptor-mediated enhancement of PIP(2) supply, must be significant for agreement between model and experiment. Importantly, the mechanistic nature of the model also allowed us to predict the efficacy of various molecular intervention strategies, including overexpression of wild-type and variant proteins in the pathway as well as treatment with specific drug inhibitors. For many parameter conditions the intuitive strategy of targeting the enzyme itself is actually predicted to be relatively inefficient, with a novel and potentially useful alternative being disruption of the reactant supply mechanism.

ErbB Receptors↗
PubMed2000

Kinetic and spectroscopic evidence for three actomyosin:ADP states in smooth muscle.

Smooth muscle myosin II undergoes an additional movement of the regulatory domain with ADP release that is not seen with fast skeletal muscle myosin II. In this study, we have examined the interactions of smooth muscle myosin subfragment 1 with ADP to see if this additional movement corresponds to an identifiable state change. These studies indicate that for this myosin:ADP, both the catalytic site and the actin-binding site can each assume one of two conformations. Relatively loose coupling between these two binding sites leads to three discrete actin-associated ADP states. Following an initial, weakly bound state, binding of myosin:ADP to actin shifts the equilibrium toward a mixture of two states that each bind actin strongly but differ in the conformation of their catalytic sites. By contrast, fast myosins, including Dictyostelium myosin II, have reciprocal coupling between the actin- and ADP-binding sites, so that either actin or nucleotide, but not both, can be tightly bound. This uncoupling, which generates a second strongly bound actomyosin ADP state in smooth muscle, would prolong the fraction of the ATPase cycle time that this actomyosin spends in a force-generating conformation and may be central to explaining the physiologic differences between this and other myosins.

Actins↗
PubMed2000

Aging fibroblasts present reduced epidermal growth factor (EGF) responsiveness due to preferential loss of EGF receptors.

Wound healing is compromised in aging adults in part due to decreased responsiveness of fibroblasts to extracellular signals. However, the cellular mechanisms underlying this phenomenon are not known. Aged dermal fibroblasts with reduced remaining replicative capacities demonstrated decreased epidermal growth factor (EGF)-induced cell migrative and cell proliferative capacities, as reported previously. Thus, as cells approach senescence, programmed in vivo or in vitro, EGF responsiveness is preferentially lost. To define the rate-limiting signaling event, we found that the activity of two different EGF receptor (EGFR)-signaling pathways to cell migration (phospholipase-C gamma) and/or mitogenesis (extracellular signal/regulated-mitogen-activated kinases) were decreased in near senescent cells despite unchanged levels of effector molecules. Aged cells presented decreased levels of EGFR, although insulin receptor and transferrin receptor levels were relatively unchanged. EGFR mRNA levels and production of new transcripts decreased during aging, suggesting that this preferential loss of EGFR was due to diminished production, which more than counteracts the reduced ligand-induced receptor loss. Since these data suggested that the decrement in EGF was rate-limiting, higher levels of EGFR were established in near senescent cells by electroporation of EGFR cDNA. These cells presented higher levels of EGFR and recovered their EGF-induced migration and proliferation responsiveness. Thus, the defect in EGF responsiveness of aged dermal fibroblasts is secondary to reduced EGFR message transcription. Our experimental model suggests that EGFR gene delivery might be an effective future therapy for compromised wound healing.

Cell Division↗