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Biomedical subjects

M G Scott

Publications and source records attributed to M G Scott.

At least 37 records · Page 2Linked to original sources
PubMed2000

An IgM lambda antibody to Escherichia coli produces false-positive results in multiple immunometric assays.

BACKGROUND: Interferences in immunometric assays as a result of human anti-immunoglobulin antibodies frequently have been described in the literature. The etiology of these interfering antibodies is usually not known but has been associated with rheumatoid factors in some assays. It is known that microorganisms in experimental settings can induce anti-immunoglobulin antibodies. METHODS: Following Escherichia coli septicemia, a 56-year-old male patient had increased immunoassay results for cardiac troponin I, thyrotropin, human chorionic gonadotropin, alpha-fetoprotein, and CA-125 that were consistent with myocardial infarction, hyperthyroidism, and pregnancy, and suggestive of an occult neoplasm such as hepatic or ovarian cancer. None of these diagnoses were consistent with the rest of his medical exam. In addition, the patient had a restricted IgM lambda paraprotein by immunofixation. Plasma from the patient was incubated with Sepharose-conjugated protein A, irrelevant murine monoclonal antibodies, and formalin-killed E. coli organisms from his infection to determine whether these immunoassay values were falsely increased. RESULTS: Incubation of the patient's plasma with irrelevant murine monoclonal antibodies or the E. coli organism produced normal immunoassay values and removed the IgM lambda paraprotein. CONCLUSIONS: The patient produced a very restricted IgM lambda antibody response to the E. coli infection that had anti-immunoglobulin activity and caused falsely increased values in numerous immunometric assays. Microorganism-induced anti-immunoglobulin antibodies are discussed in the context of this patient.

Animals↗
PubMed2000

Bone lead concentrations assessed by in vivo X-ray fluorescence.

The assessment of past chronic lead exposure is difficult. Chronic lead burden is not always correctly assessed using laboratory-based tests that are useful for acute or recent exposures. We describe a case of suspected chronic lead exposure that illustrated the need for improved and possibly noninvasive methods to determine cumulative lead body burden. X-Ray fluorescence (XRF) is discussed as a method to obtain in vivo bone lead measurements. We discuss the potential of such measurements as accurate biomarkers of cumulative exposure and whether XRF can be used for retroactive exposure assessment or to predict risk of future health problems.

Biomarkers↗
PubMed2000

Cationic antimicrobial peptides and their multifunctional role in the immune system.

Many species of life contain cationic antimicrobial peptides as components of their immune systems. The antimicrobial activity of these peptides has been studied extensively, and many peptides have a broad spectrum of activity not only against gram-negative and gram-positive bacteria but also against antibiotic-resistant bacteria, fungi, viruses, and parasites. Such cationic antimicrobial peptides can also act in synergy with host molecules, such as other cationic peptides and proteins, lysozyme, and also conventional antibiotics, to kill microbes. It has been found that certain peptides are produced in large quantities at sites of infection/inflammation, and their expression can be induced by bacterial products such as endotoxic lipopolysaccharide (LPS) and proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha). These peptides often have a high affinity for bacterial products, such as LPS, allowing them to modulate the host response and reduce the inflammatory response in sepsis. More recently, they have been found to interact directly with host cells to modulate the inflammatory process and innate defenses.

Amino Acid Sequence↗
PubMed1999

Identification of novel polymorphisms within the promoter region of the human beta2 adrenergic receptor gene.

By screening the 1470 bp 5' to the start codon of the human beta2 adrenergic receptor gene, we have identified a total of eight polymorphisms (-20 T-->C, -47 T-->C, -367 T-->C, -468 C-->G, -654 G-->A, -1023 G-->A, -1343 A-->G and -1429 T-->A c.f. beta2 adrenergic receptor start codon). Transient transfection of 5' flanking deletion luciferase reporter constructs demonstrated the majority of activity of the human beta2 adrenergic gene 5' flanking region to be present within a 549 bp fragment immediately upstream from the start codon. Because of linkage disequilibrium, some combinations of polymorphisms were particularly frequent. We transiently transfected COS-7 cells with luciferase constructs under the control of the 549 bp of 5' flanking DNA containing the two most frequent extended haplotypes in this region. Luciferase activity was significantly reduced in cells transfected with the 'mutant' construct (-20C, -47C, -367C, -468G) c.f. the 'wild-type' construct (-20T, -47T, -367T, -468C). These data suggest that polymorphisms have the potential to alter human beta2 adrenergic receptor gene expression.

Animals↗
PubMed1999

Effects of a range of beta2 adrenoceptor agonists on changes in intracellular cyclic AMP and on cyclic AMP driven gene expression in cultured human airway smooth muscle cells.

1. The effects of the selective beta2 adrenoceptor agonists salbutamol, terbutaline and salmeterol and the non-selective beta adrenoceptor agonist isoprenaline on [3H]-cyclic AMP formation and cyclic AMP response element (CRE) driven luciferase expression, assessed using the construct p6CRE/luc, were studied in primary cultures of human airway smooth muscle (HASM) cells. 2. Optimal transfection conditions for transient expression of pGL3 Control were 4 microg DNA/well71 in a 6 well plate and 1.8 microl Transfectam/microg DNA. Expression was maximal at 48 - 72 h. 3. Salbutamol (maximum response 19%, EC50 0.6 microM), terbutaline (maximum response 38%, EC50 2.3 microM) and salmeterol (maximum response 18%, EC50 0.0012 microM) were all partial agonists for cyclic AMP formation compared with isoprenaline (EC50 0.08 microM). However, all of the beta2 adrenoceptor agonists produced increases in CRE-driven luciferase activity, in cultured HASM transfected with the vector p6CRE/luc, which were equivalent or greater (salmeterol) than those seen with isoprenaline. 4. Both salbutamol and salmeterol were more potent at increasing luciferase expression than in elevating cyclic AMP levels in these cells. The potency ratios (EC50 (cyclic AMP)/EC50 (LUC)) for the agents studied were isoprenaline: 0. 2 fold, terbutaline: 3 fold, salbutamol: 24 fold, salmeterol: 38 fold. 5. These data suggest that important quantitative differences exist in the ability of beta2 adrenoceptor agonists to increase whole cell cyclic AMP levels in airway smooth muscle and to drive gene expression via a CRE-driven mechanism.

Adrenergic beta-2 Receptor Agonists↗
PubMed1999

Sequential antimicrobial therapy: treatment of severe lower respiratory tract infections in children.

Although there have been a number of studies in adults, to date there has been little research into sequential antimicrobial therapy (SAT) in paediatric populations. The present study evaluates the impact of a SAT protocol for the treatment of severe lower respiratory tract infection in paediatric patients. The study involved 89 paediatric patients (44 control and 45 SAT). The SAT patients had a shorter length of hospital stay (4.0 versus 8.3 days), shorter duration of inpatient antimicrobial therapy (4.0 versus 7.9 days) with the period of iv therapy being reduced from a mean of 5.6 to 1.7 days. The total healthcare costs were reduced by 52%. The resolution of severe lower respiratory tract infection with a short course of iv antimicrobials, followed by conversion to oral therapy yielded clinical outcomes comparable to those achieved using longer term iv therapy. SAT proved to be an important cost-minimizing tool for realizing substantial healthcare costs savings.

Administration, Oral↗
PubMed1999

Salt-resistant alpha-helical cationic antimicrobial peptides.

Analogues based on the insect cecropin-bee melittin hybrid peptide (CEME) were studied and analyzed for activity and salt resistance. The new variants were designed to have an increase in amphipathic alpha-helical content (CP29 and CP26) and in overall positive charge (CP26). The alpha-helicity of these peptides was demonstrated by circular dichroism spectroscopy in the presence of liposomes. CP29 was shown to have activity against gram-negative bacteria that was similar to or better than those of the parent peptides, and CP26 had similar activity. CP29 had cytoplasmic membrane permeabilization activity, as assessed by the unmasking of cytoplasmic beta-galactosidase, similar to that of CEME and its more positively charged derivative named CEMA, whereas CP26 was substantially less effective. The activity of the peptides was not greatly attenuated by an uncoupler of membrane potential, carbonyl cyanide-m-chlorophenylhydrazone. The tryptophan residue in position 2 was shown to be necessary for interaction with cell membranes, as demonstrated by a complete lack of activity in the peptide CP208. Peptides CP29, CEME, and CEMA were resistant to antagonism by 0.1 to 0.3 M NaCl; however, CP26 was resistant to antagonism only by up to 160 mM NaCl. The peptides were generally more antagonized by 3 and 5 mM Mg2+ and by the polyanion alginate. It appeared that the positively charged C terminus in CP26 altered its ability to permeabilize the cytoplasmic membrane of Escherichia coli, although CP26 maintained its ability to kill gram-negative bacteria. These peptides are potential candidates for future therapeutic drugs.

Alginates↗
PubMed1999

Interaction of cationic peptides with lipoteichoic acid and gram-positive bacteria.

Compounds with antiendotoxin properties have been extensively studied for their potential as therapeutic agents for sepsis attributable to gram-negative bacteria. However, with the increasing incidence of gram-positive sepsis, there is interest in identifying compounds with a broad spectrum of action against both gram-positive and gram-negative bacteria. A series of synthetic alpha-helical cationic peptides related to bee melittin and silk moth cecropin have previously been shown to bind lipopolysaccharide (LPS) with high affinity, inhibit LPS-induced tumor necrosis factor alpha (TNF-alpha) production in vitro and in vivo, and kill gram-negative bacteria. In this study, we analyzed whether these peptides were active against gram-positive bacteria; whether they could bind to lipoteichoic acid (LTA), the major proinflammatory structure on gram-positive bacteria; and whether they could block the ability of LTA to promote the release of cytokines by the RAW 264.7 murine macrophage cell line. We found that the cationic peptides demonstrated moderate growth-inhibitory activity toward gram-positive bacteria. In addition, the peptides bound LTA with high affinity. This correlated with the ability of the peptides to block LTA-induced production of TNF and interleukin-6 by RAW 264.7 cells but did not correlate with their ability to kill the bacteria. The peptides also effectively inhibited LTA-induced TNF production in a whole human blood assay. The peptides were also able to partly block the ability of heat-killed Staphylococcus aureus, as well as soluble products of live S. aureus, to stimulate cytokine production by macrophages. Our results indicate that these cationic peptides may be useful to prevent sepsis and inflammation caused by both gram-negative and gram-positive bacteria.

Anti-Bacterial Agents↗
PubMed1999

Biological properties of structurally related alpha-helical cationic antimicrobial peptides.

A series of alpha-helical cationic antimicrobial peptide variants with small amino acid changes was designed. Alterations in the charge, hydrophobicity, or length of the variant peptides did not improve the antimicrobial activity, and there was no statistically significant correlation between any of these factors and the MIC for Pseudomonas aeruginosa, Escherichia coli, or Salmonella typhimurium. Individual peptides demonstrated synergy with conventional antibiotics against antibiotic-resistant strains of P. aeruginosa. The peptides varied considerably in the ability to bind E. coli O111:B4 lipopolysaccharide (LPS), and this correlated significantly with their antimicrobial activity and ability to block LPS-stimulated tumor necrosis factor and interleukin-6 production. In general, the peptides studied here demonstrated a broad range of activities, including antimicrobial, antiendotoxin, and enhancer activities.

Amino Acid Sequence↗
PubMed1999

Modulation of human airway smooth muscle proliferation by type 3 phosphodiesterase inhibition.

Elevation in cell cAMP content can inhibit mitogenic signaling in cultured human airway smooth muscle (HASM) cells. We studied the effects of the type 3-selective phosphodiesterase inhibitor siguazodan, the type 4-selective phosphodiesterase inhibitor rolipram, and the nonselective inhibitor 3-isobutyl-1-methylxanthine (IBMX) on proliferation of cultured HASM cells. At concentrations selective for the type 3 phosphodiesterase isoform, siguazodan inhibited both [3H]thymidine incorporation (IC50 2 microM) and the increase in cell number (10 microM; 64% reduction) induced by platelet-derived growth factor-BB (20 ng/ml). These effects were mimicked by IBMX. At concentrations selective for type 4 phosphodiesterase inhibition, rolipram was without effect. A 20-min exposure to siguazodan and rolipram did not increase whole cell cAMP levels. However, in HASM cells transfected with a cAMP-responsive luciferase reporter (p6CRE/Luc), increases in cAMP-driven luciferase expression were seen with siguazodan (3.9-fold) and IBMX (16.5-fold). These data suggest that inhibition of the type 3 phosphodiesterase isoform present in airway smooth muscle results in inhibition of mitogenic signaling, possibly through an increase in cAMP-driven gene expression.

1-Methyl-3-isobutylxanthine↗
PubMed1998

Comparison between the CEDIA and EMIT II immunoassays for the determination of benzodiazepines.

We evaluated a new, qualitative immunoassay for benzodiazepines in urine using CEDIA technology on the Hitachi 747 and compared its performance to an immunoassay using EMIT II methodology on the same instrument. A total of 500 urine samples received for routine drug screen analysis were prospectively examined for benzodiazepines by both methods. Samples producing positive results by either immunoassay method were analyzed by gas chromatography-mass spectrometry (GC-MS). Available medical records were reviewed for patients whose samples produced discrepant immunoassay results or that were positive in both immunoassays but negative by GC-MS. Samples that produced negative results in both immunoassays were not subjected to GC-MS analysis. Therefore, identification of an immunoassay result as a false negative only occurred when the sample produced a positive value in only one of the two immunoassays and was confirmed as positive by either GC-MS or medical record review. Following initial immunoassay screening and confirmation by GC-MS, a medical record review and reanalysis of GC-MS data was performed. After this in-depth analysis of the data, the CEDIA method produced 60 true-positives, 7 false positives and no false negatives. The EMIT II method produced 47 true positives, 1 fase positive and 13 false negatives. These differences appear to be due to the CEDIA assay being more sensitive for detection of lorazepam.

Benzodiazepines↗
PubMed1998

Buccal absorption of enalapril and lisinopril.

OBJECTIVE: The buccal absorption of captopril does not exhibit the classical pH/partition hypothesis, suggesting that mechanisms other than passive diffusion are involved in its absorption; animal studies have suggested that a peptide carrier-mediated transport system may be responsible for its absorption. The present study evaluated the effects of pH on octanol partitioning, and on the buccal absorption of enalapril and lisinopril, using in vitro techniques and buccal partitioning in human volunteer subjects. METHODS: The partitioning of enalapril and lisinopril into n-octanol was examined over the pH range of 3 9 at room temperature. RESULTS: Enalapril exhibited maximal partitioning into the organic phase at pH 4 5; minimal partitioning was recorded at pH values 8 and 9. The partitioning of lisinopril into n-octanol was found to be maximal at pH 9 and minimal at pH 3. Using the buccal absorption technique, the partitioning of enalapril and lisinopril (0.5 mg), was examined in six healthy male volunteers from buffered solutions (pH 3, 4, 5, 6, 7, 8 and 9). In the case of enalapril, lowest buccal partitioning occurred at pH 3, 8 and 9, while maximal partitioning occurred at pH 5; absorption of lisinopril was not extensive at any pH, but was greatest at pH 6. These results, in addition to the n-octanol partition coefficients, indicated that enalapril obeyed the normal lipid partition hypothesis with respect to buccal absorption. The buccal absorption of lisinopril also obeyed the lipid partition hypothesis over the pH range 3-7. These findings are in direct contrast to those for captopril. The buccal partitioning experiments were repeated at the maximal pH for absorption for each angiotensin converting enzyme (ACE) inhibitor, but with the addition of cephradine (0.05 mmol x l(-1)). CONCLUSION: The data indicated that the presence of this peptide transport inhibitor had no effect on the buccal absorption of enalapril (0.06 mmol x l(-1)) and lisinopril (0.057 mmol x l(-1)), which suggests that both drugs do not share a common buccal absorption pathway with cephradine.

Administration, Buccal↗
PubMed1998

Oxygen carriers as blood substitutes. Past, present, and future.

Prospects for safe and effective blood substitutes are promising, based on clinical trial results of soluble hemoglobin solutions and emulsion of perfluorocarbins. Advantages of blood substitutes include sterilization of viral and bacterial contaminants, room temperature storage, a long shelf life, and absence of ABO and other red cell antigens. Projected arenas for their use include not only military applications but also trauma medicine and elective surgical settings, coupled with acute normovolemic hemodilution. Applications of perfluorocarbons are limited by the need for 100% FIO2. A significant challenge facing development of hemoglobin solutions is their effect on vascular tone through smooth muscle constriction. Development of second or third generation hemoglobin solutions may be necessary so that hemoglobin solutions more closely mimic cellular hemoglobin's nitric oxide binding properties. Optimizing O2 delivery to ischemic tissues and organs may lead to regulatory approval of these agents in this setting before their approval as blood substitutes.

Blood Substitutes↗
PubMed1998

Coexpression of parathyroid hormone-related protein and its receptor in breast carcinoma: a potential autocrine effector system.

Parathyroid hormone-related protein (PTHrP), the pathogenic factor in most cases of humoral hypercalcemia of malignancy, is also expressed by many normal tissues. Its diverse biologic activities in these tissues are mediated by the PTH/PTHrP receptor through autocrine and paracrine mechanisms. Recent data suggest that PTHrP and its receptor might also influence the growth and metastatic spread of some cancers through similar local actions. Accordingly, immunohistochemical studies using murine monoclonal antibodies to detect coexpression of PTHrP and the PTH/PTHrP receptor were performed on 52 invasive breast carcinomas to assess the existence of this potential autocrine effector system. All of the 52 invasive breast carcinomas expressed reactivity for PTHrP, and 50 (96%) of these tumors also expressed reactivity for the receptor. Although additional investigations are necessary for evaluation of the role of PTHrP and PTH/PTHrP receptor in tumor pathogenesis, our current study demonstrates the presence of this potential autocrine effector system in the great majority of invasive breast carcinomas.

Adult↗
PubMed1998

Clinical utility of the soluble transferrin receptor and comparison with serum ferritin in several populations.

Soluble transferrin receptor (sTfR) and ferritin concentrations were measured in a variety of clinical settings to compare the ability of these two tests to identify iron deficiency. Among 62 anemic patients who either had a bone marrow aspirate performed or had a documented response to iron therapy, the diagnostic sensitivity and specificity of sTfR (at a diagnostic cutoff of > 2.8 mg/L) were 92% and 84%, respectively, with a positive predictive value of 42% in this population. Ferritin (< or = 12 microg/L) had a sensitivity of 25% and a specificity of 98%. However, the sensitivity and specificity of ferritin could be improved to 92% and 98%, respectively, by using a diagnostic cutoff value of < or = 30 microg/L, resulting in a positive predictive value of 92%. Ferritin and sTfR were also measured in 267 outpatient samples and 112 medical students. In the outpatient group, the two tests agreed in 73% of the samples; however, 25% of the samples had ferritin values > 12 microg/L and increased sTfR. Among the medical students, there was 91% agreement between the two tests, but 7% of the samples had ferritin < or = 12 microg/L and normal sTfR. Together, these data suggest that measurement of sTfR does not provide sufficient additional information to ferritin to warrant routine use. However, sTfR may be useful as an adjunct in the evaluation of anemic patients, whose ferritin values may be increased as the result of an acute-phase reaction.

Acute-Phase Reaction↗
PubMed1998

Mechanisms of dopamine and dobutamine interference in biochemical tests that use peroxide and peroxidase to generate chromophore.

Dopamine and dobutamine have recently been shown to produce a negative interference in several biochemical tests that use peroxide and peroxidase to generate a chromophore. To define the chemical mechanism of this interference, we examined the effects of dopamine and dobutamine in various peroxidase-based biochemical tests. Dopamine interfered stoichiometrically with peroxidase-based tests that use 4-aminophenazone to form chromophore but interfered little in those that use other compounds to generate chromophore. Dopamine reacts with 4-aminophenazone in the presence of peroxide and peroxidase to form a novel quinone-imine dye, with a smaller absorptivity than the chromophore formed in the absence of dopamine. The smaller absorptivity of this novel chromophore results in negative interference by reducing the total absorbance at the wavelength used to measure analyte. In contrast, dobutamine interfered stoichiometrically with all peroxidase-based tests studied, regardless of whether 4-aminophenazone was used to form the chromophore. Dobutamine was rapidly oxidized by peroxide in the presence of peroxidase, thus depleting the peroxide necessary to generate chromophore. Dopamine and dobutamine demonstrate two distinct general mechanisms of interference in peroxidase-based biochemical tests.

Ampyrone↗