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Biomedical subjects

J Landon

Publications and source records attributed to J Landon.

At least 19 recordsLinked to original sources
PubMed1992

Patient delay and receipt of thrombolytic therapy among patients with acute myocardial infarction from a community-wide perspective.

The duration of patient delay from the time of onset of symptoms of acute myocardial infarction (AMI) to hospital presentation, and the relation of delay time and various patient characteristics to receipt of thrombolytic therapy were examined as part of a community-based study of patients hospitalized with AMI in the Worcester, Massachusetts, metropolitan area. In all, 800 patients with validated AMI hospitalized at 16 hospitals in the Worcester metropolitan area in 1986 and 1988 constituted the study sample. Patients delayed on average 4 hours between noting symptoms suggestive of AMI and presenting to area-wide emergency departments with no significant change observed between 1986 and 1988. The shorter the time interval of delay, the greater the likelihood of receiving thrombolytic therapy; patients arriving at the emergency department within 1 hour of the onset of acute symptoms were approximately 2.5 and 6.5 times more likely to receive thrombolytic agents than were those presenting to the hospital between 4 and 6, and greater than 6 hours, respectively, after the onset of symptoms. Results of a multivariate analysis showed increasing length of delay, older age, history of hypertension or AMI and non-Q-wave AMI to be significantly associated with failure to receive thrombolytic therapy.

Adolescent↗
PubMed1992

An affinity purified ovine antivenom for the treatment of Vipera berus envenoming.

A novel antivenom for treating patients with Vipera berus bite has been developed. Sheep are immunised monthly with relatively small amounts of Vipera berus (common adder) venom and the resultant antisera pooled. The immunoglobulin fraction is precipitated with sodium sulphate then cleaved with papain to produce Fab fragments. Finally, those Fab fragments that are directed specifically against components in the venom are purified by affinity chromatography on columns comprising V. berus venom coupled to cyanogen bromide activated Sepharose 4B. The resultant product is some three times more effective than the non-purified Fab in protecting mice against the lethal venom effects.

Animals↗
PubMed1992

Patient characteristics and the effect of three physician-delivered smoking interventions.

BACKGROUND: This paper investigates individual patient characteristics predicting differential response to each of three physician-delivered smoking interventions after 6 months. METHODS: Participants were 1,286 currently smoking patients seen by 196 medical and family practice residents in five primary care clinics affiliated with the University of Massachusetts Medical School. Of the participants, 57% were female, 92% were white, their average age was 35 years, and they smoked an average of 23 cigarettes per day. Physicians were trained to provide the following interventions: advice only (AO), a brief (< 10 min) patient-centered counseling intervention (CI), and counseling plus prescription of the nicotine-containing gum Nicorette (CI+NCG). The CI+NCG condition included NCG only when appropriate and if acceptable to the patient. Patients were randomized to one of these three physician-delivered intervention conditions. RESULTS: Overall, stratified univariate analyses revealed that AO produced consistently lower cessation rates across most subgroups (generally 9-13%) but was somewhat more effective for certain groups of lighter smokers. Relative to AO, CI was somewhat more effective (about 20-24%) for less addicted smokers, for those with more previous quit attempts, and for those with fewer close associates who smoke, but generally failed to produce higher quit rates for harder core smokers or for women. CI+NCG had an overall pattern of greater effectiveness for both more addicted and less addicted smokers, with the highest absolute levels of cessation (about 27-30%) among less dependent smokers. Women in this group had cessation rates (20.6%) comparable to those of men (23.6%). Condition-stratified logistic regression analyses, controlling for a wide range of covariates, revealed associations similar to those observed in the univariate analyses: An overall logistic model in which intervention conditions were fitted as dummy variables produced the following significant main effects: sex, years smoked, contact with other smokers, symptoms, and CI+NCG condition. Significant interactions were observed for both CI and CI+NCG and smoking when feeling too ill to continue normal activities and CI+NCG and amount smoked. CONCLUSIONS: We observed significant main effects on cessation of variables related to addiction, sex, social factors, and physician counseling interventions. Specific interactions were observed between reported smoking when feeling ill and each of the counseling interventions as well as by amount smoked in the CI+NCG condition.

Adult↗
PubMed1992

Urinary cotinine fluoroimmunoassay for smoking status screening adapted to an automated analyser.

A polarization fluoroimmunoassay for cotinine, a major metabolite of nicotine, has been adapted for fully automated screening of urine samples on the Abbott TDx analyser. The method has sensitivity and specificity suitable for the discrimination of active smokers from non-smokers (including passive smokers) by application of a cut-off at 0.5 mg l-1 of total urinary cotinine. Most active smokers' urine gave results over 1 mg l-1, whereas apparent levels in non-smokers were 0.08 mg l-1 or lower. A result for one sample can be obtained in about 5 min and a throughput of 80 samples h-1 can be maintained for large-scale screening applications.

Adult↗
PubMed1992

Production of polyclonal antibodies in ascitic fluid of mice: time and dose relationships.

Further studies of the humoral immune response have been undertaken using ovine immunoglobulin G as the immunogen and BALB/C mice as the recipients. Mice immunized by the intraperitoneal route weekly for five weeks with an emulsion of the immunogen in Freund's complete adjuvant and given an intraperitoneal injection of pristane on day 14 produce relatively large volumes of ascitic fluid. A simple fluoroimmunoassay is used to determine specific antibody titres. The mice do not lose condition, remain active and eat normally throughout, although all show extensive granuloma formation within the peritoneal cavity. Tapping is performed before ascitic fluid production is excessive and each study is complete within 49 days, with a maximum of 5 taps. Only a single immunization site is required, since no higher antibody titres are obtained using combined intraperitoneal plus intramuscular plus subcutaneous immunization routes. A dose response study has shown that relatively large amounts (100 micrograms) of ovine immunoglobulin G must be injected to evoke a maximum response. Studies are in progress of various adjuvants and potential modulators of the immune response and of ways in which the immunogenicity of macromolecules can be changed. This approach can also be used to obtain antibodies for diagnostic purposes more rapidly than in rabbits and sheep.

Animals↗
PubMed1991

The effect of fluorescein labels on the affinity of antisera to small haptens.

Small haptens such as methylamphetamine (MW 149) cannot, on their own, induce an immune response. It is also unlikely that they fill the binding site of any antibody that recognises them. Under such circumstances any attached label might be expected to enter the area of the binding site and exert an influence on overall binding. To investigate the possible influence of the label on binding, a range of fluorescein-labelled derivatives, differing in bridge length, were prepared. Antiserum binding of these labelled derivatives was then compared to that of the unlabelled drug. Evidence is presented which suggests that, with small haptens, the closeness of the fluorescein molecule can markedly influence antibody binding. Significant differences were found in titre, sensitivity, and assay kinetics. These overall effects appear to be brought about by the change in affinity of the antibody for the labelled hapten.

Amphetamines↗
PubMed1991

An indirect haemolytic assay for assessing antivenoms.

Dilutions of antivenom, venom, human erythrocytes and a phosphatidylcholine suspension, were incubated for 30 min at 37 degrees C. After centrifugation, the liberated haemoglobin was measured spectrophotometrically. The assay was used to assess an ovine antivenom against the venom from the South American rattlesnake, Crotalus durissus terrificus, and an equine Wyeth antivenin (Crotalidae, polyvalent). The ovine antivenom was more than five times as effective as the equine product. It also neutralized venoms from the Western diamondback rattlesnake, Crotalus atrox, and the fer-de-lance, Bothrops atrox. However, antivenoms raised against venoms from other Crotalus and Bothrops species provided little protection against the haemolytic activity of C. d. terrificus venom.

Antivenins↗
PubMed1991

Development and validation of a fluoroimmunoassay for urinary normetanephrine.

The development of a separation fluoroimmunoassay for urinary normetanephrine is described. Antiserum specific to normetanephrine was coupled, using cyanogen bromide, to magnetizable cellulose; and fluorescein labelled normetanephrine was synthesized from fluoresceinthiocarbamylethylene diamine and a previously described normetanephrine derivative. Using these reagents it was possible to construct a reproducible standard curve, covering a wide range of concentrations, and to accurately measure the concentration of this metabolite in acid-hydrolysed urine samples. Cross-reactivities of structurally similar compounds were low and the fluoroimmunoassay showed good correlation with an established gas-chromatographic assay. The procedure is rapid; it is possible to accurately determine the normetanephrine concentration of urine samples approximately 2 h after hydrolysis, resulting in an overall assay time of approximately 4 h. This is the first report of a non-isotopic immunoassay for normetanephrine.

Animals↗
PubMed1990

Development of a radioimmunoassay for idazoxan hydrochloride.

To facilitate the measurement of idazoxan in clinical trials an immunoassay capable of detecting low ng ml-1 concentrations was required. A stable derivative was prepared which, after linking to keyhole limpet hemocyanin (KLH), was subsequently immunized into sheep. Early assay development was carried out with both fluorescent (1-FITC) and iodinated (I-125) labels. The assay methodology was the same in both cases, using magnetizable solid-phase particles to which the antibody was linked. The sensitivity of the assay was such that a large sample volume was required, which in turn, led to problems of increased protein interference. The use of pepsin to digest the protein was used effectively after several blocking agents were unsuccessfully used. The limit of detection was in the region of 3 ng ml-1. Cross-reactivity studies showed that the antibody was specific for idazoxan. Intra- and inter-assay precision was 7 and 12%, respectively. Correlation with the analytical GC-MSD method was in the order of 0.90.

Antibody Specificity↗
PubMed1990

Circulating levels of GH-releasing hormone and GH during human pregnancy.

To study the potential role of GH-releasing hormone (GHRH) in maintaining circulating levels of GH during pregnancy, 302 maternal plasma samples were collected from non-fasted subjects at various stages of pregnancy and assayed for GHRH using a 'two-site' immunoradiometric assay. The GH and placental lactogen levels were also determined. In addition, maternal plasma samples taken during labour, amniotic fluid and cord blood were also assayed for these hormones. Maternal plasma GHRH levels were similar to non-pregnant levels throughout gestation despite fluctuations in GH values which were always higher than non-pregnant levels. There was no significant difference between GHRH levels in maternal plasma and cord blood although high GH levels were observed in the latter. These findings suggest that peripheral GHRH levels do not play an important role in maintaining circulating GH levels during pregnancy.

Amniotic Fluid↗
PubMed1989

Production and characterisation of antibodies to vanillylmandelic acid.

Antibodies were raised to the catecholamine metabolite vanillylmandelic acid (VMA). The side chain was protected and, after derivatisation through the 4-phenolic hydroxyl group, the hapten was coupled to KLH and the resultant conjugate deprotected. Sheep immunised with this immunogen responded with specific, high titre antibodies to VMA as assessed using a fluorescent label. Cross-reaction of the antiserum from one of the sheep was minimal, being under 1% with all naturally occurring related compounds tested. This report is the first to describe an effective antiserum for VMA which will permit measurement over the normal range in urine.

Animals↗
PubMed1989

Development of a magnetisable solid-phase fluoroimmunoassay for primaquine and carboxyprimaquine.

Primaquine coupled to keyhole limpet hemocyanin was used as an immunogen to produce antiprimaquine antibodies in three sheep. The antisera obtained were characterised by the increase in fluorescence polarisation found upon binding to fluorescein-labelled primaquine prepared via same route. All sheep showed a good antibody response and one antiserum was coupled to magnetisable solid-phase particles to facilitate the separation of the antibody bound from free labelled antigen and the removal of interfering components which may be present in the sample. The fluoroimmunoassay requires addition of 100 microliters of standard or sample (urine or serum) to 100 microliters tracer (150 nmol/l) followed by 100 microliters of magnetisable solid-phase particles (12.5 g/l). After one hour incubation followed by the usual washing and eluting procedures, using a magnetic rack, the fluorescence of the supernatant was measured directly in a fluorimeter. Sodium salicylate was incorporated in the tracer solution to block the non-specific binding of tracer to the protein in serum samples. Cross-reactivity studies showed that the antibodies have high specificity for the 8-aminoquinoline nucleus but not to the 8-N-aminobutyl side chain. Thus carboxyprimaquine cross-reacted equally with primaquine and the assay can be used to measure their combined level. After extraction of primaquine from a basified sample with methylene chloride, the assay may be applied for the quantitation of either primaquine (in the organic phase) or its acidic metabolites including carboxyprimaquine (in the aqueous phase) separately. This approach was applied for the determination of total primaquine (primaquine and its metabolites) and extracted primaquine in urine samples following a single oral dose of 45 mg primaquine.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1989

An improved label for amphetamine fluoroimmunoassay.

This paper describes the synthesis of amphetamine derivatives, functionalized at the para-position of the phenyl ring of the drug. These derivatives were used to prepare fluorescein-labelled amphetamine to replace the label in a previously described polarisation fluoroimmunoassay that is highly specific for amphetamine. The original label was obtained using material donated by industrial sources and therefore not generally available. When the new label was used in the immunoassay, specificity was similar but the sensitivity was improved by a factor of four. This increase in sensitivity is explained by elimination of bridge-binding effects.

Amphetamines↗
PubMed1988

Development of a simple, fluoroimmunoassay for paraquat.

High affinity populations of antibodies to paraquat were produced in high concentrations in the sera of immunised sheep. A simple fluoroimmunoassay was developed for rapid measurement of plasma paraquat. Fluorescein-labelled paraquat was added to sample or standard (20 microliter) followed by premixed first and second antisera. Equilibrium was reached within 2 min and results were available within 20 min. Correlation with weighed-in paraquat gave a regression line (r) of 0.997. All reagents proved stable and are suitable for general distribution.

Animals↗
PubMed1988

Comparison of separation techniques in radioimmunoassays for 17-hydroxyprogesterone.

Separation techniques have been studied in the development of a direct radioimmunoassay to determine levels of 17-hydroxyprogesterone in serum. The same highly specific sheep antiserum was used throughout, together with the same amount of 125I-labelled 17-hydroxyprogesterone to which was added sodium salicylate to eliminate interference by endogenous binding proteins in serum samples. In one approach, dextran-coated charcoal was employed to adsorb the free fraction and, in another, the antibodies were covalently coupled to magnetisable particles. The antiserum was also adsorbed to assay tubes either directly or indirectly through second (double) antibodies. Analytical recovery and specificity were similar irrespective of the separation technique as was the correlation with results obtained by a reference assay. Levels of 17-hydroxyprogesterone in sera from normal adults and from treated and untreated patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency were also similar. However, the assay employing dextran-coated charcoal for separation showed the best precision and resulted in the greatest sensitivity, while the use of antibodies adsorbed indirectly to assay tubes was superior in terms of practicability.

17-alpha-Hydroxyprogesterone↗
PubMed1988

Production of polyclonal antibodies in ascitic fluid of mice: technique and applications.

Balb/c mice immunised intraperitoneally with insulin developed significantly higher antibody concentrations in their serum than mice immunised subcutaneously. The antibody response was dose related, 50 ug amounts being more effective than either 20 ug or 5 ug amounts. In contrast, the antibody titres in the ascitic fluid of mice immunised with growth hormone were significantly higher after 5 ug when compared to 25 and 100 ug amounts. Repeated intraperitoneal injections of an emulsion of sheep IgG or human growth hormone in complete Freund's adjuvant, together with a single intraperitoneal injection of Pristane, induced ascites formation in most mice within 5 weeks. Up to 90 mL could be obtained from a single mouse by abdominal tapping, and the antibodies derived from the ascitic fluid proved suitable for application in a radioimmunoassay.

Animals↗
PubMed1988

Development of separation fluoroimmunoassays for bendazac and 5-hydroxy bendazac.

Two distinct separation fluoroimmunoassays were developed to determine serum levels of bendazac and its main metabolite 5-hydroxy bendazac for use in early pharmacokinetic studies and for long-term therapeutic drug monitoring should this prove necessary. In both assays fluorescein-labeled analyte was used as tracer and the antibodies were coupled to magnetizable particles. The use of a magnetizable solid phase enabled a simple and rapid separation step and thus a high sample throughput. There was no crossreactivity between the drug and its metabolite in either assay, indicating that highly specific antibodies had been produced. The results from both assays correlated well with serum levels determined by a high performance liquid chromatography method.

Anti-Inflammatory Agents, Non-Steroidal↗