An ELISA for anti-thymocyte autoantibody in NZB mice. Comparison with the cytotoxic assay

An ELISA is described for the detection of anti-thymocyte antibody found in the serum of NZB autoimmune mice. This assay avoids the disadvantages of previous assay techniques which require carefully selected complement sources and/or radioactive labelled target cells. Thymocytes from a variety of strains of mice can be used as the antigenic targets, and the plates stored as long as 1 month. The lymphoma line EL4 can be used as the antigenic target in this assay, but it not as sensitive to most serum pools as thymocytes.     

A short-term-culture ELISA system to detect IgG and autoantibody synthesis by human lymphocytes

A simple combined culture and assay system for small numbers of human lymphocytes is described which permits rapid detection of immunoglobulin adherent to 96-well plates after 18 h culture, by means of an enzyme-linked immunosorbent assay (ELISA). The method is capable of detecting thyroglobulin antibody secreted by cells obtained from fine needle aspiration of the thyroid and therefore allows investigation of B cells activated in vivo from different sites by quantitation of the amount of immunoglobulin or antibody secreted.     

Factors affecting the measurement of bone impedance

Factors which affect the measurement of the electrical properties of bone were examined. Environmental conditions such as the pH of the preserving solution and time of exposure of the sample to air, which controls the moisture content of the specimen, significantly affected the bone impedance. A change in pH of ×2 from the neutral solution (pH=7) caused a change in the resistance R. conductance β and capacitance C values of 70 per cent, 125 per cent and 190 per cent respectively. A 5 min exposure to air increased the resistance by 92 per cent and reduced the capacitance by 35 per cent of their original values. A loss of 8 per cent moisture content by weight resulted in 400 per cent increase in R and 65 per cent decrease in C. Significant errors were introduced in the measurement of bone impedance owing to stray and wiring capacitances; these were avoided by using a differential impedance measurement technique. Further, it is shown that it is essential to measure the phase angle while measuring the bone impedance. Finally, it is illustrated that when normalising for different sized bone specimens, both the resistive component and capacitive component have to be considered while computing the impedance per unit volume.     

Factors affecting the perception of low-level vibration

Summary The level at which vibration becomes a nuisance is low, well below the vibration intensity discussed with regard to the health of industrial workers in the International Standard ISO-2631 draft. The relationships between the various factors and the human response to low-level vibration generated by vehicular traffic, are discussed from the results obtained from questionnaires.A female may respond to a lower level than a male. There is no difference in response to low-level vibration between standing and sitting postures. Accompanying noise distracts the perception of low-level vibration, however at high levels, the effect of distraction is reduced.     

Factors affecting IgA related hyperviscosity

Sera from 14 patients with an IgA M-component, six of whom had myelomatosis and eight with benign monoclonal gammopathy (BMG) were analysed. All six sera from patients with high IgA (greater than 40 g/l) and total protein (greater than 100 g/l) concentrations were hyperviscous (HV). Four of these six patients also had hyperviscosity syndrome (HVS). There was no correlation between the quantity of IgA dimers or polymers and the presentation of HV and HVS. The binding between IgA and albumin and alpha 1-anti-trypsin was not covalent. Differences in the microenvironment of S-S bonds or of aromatic amino acids between isolated monoclonal monomeric and dimeric IgA were demonstrated with circular dichroism. Besides that, differences in hydrophobicity (exposure of aromatic amino acids) between IgA from normal serum and monomeric and dimeric IgA from a myeloma serum were revealed using hydrophobic interaction chromatography. The significance of hydrophobic interactions involving IgA and the influence of such forces on the circulation of the molecules are discussed.     

Factors affecting time to pregnancy

BACKGROUND: Both lifestyle factors and occupational and environmental factors have been suggested to affect the female reproductive system. In the present study, the separate and joint effects of several such factors are investigated. METHODS: Information on time to pregnancy (TTP) was available for 1578 women randomly selected from the general Swedish population. The information was collected retrospectively by using self-administered questionnaires. By means of logistic regression of survival data, fecundability odds ratios were determined for many factors. Multivariate models were used to determine which factors had the most impact on TTP. RESULTS: Several lifestyle factors were found to associate with TTP. However, only use of oral contraceptives prior to attempting to conceive, menstrual cycle length, age at conception and parity remained in the multivariate models. Together, these factors explained 14% of the variance in TTP. Excluding first and second month conceptions, only age at conception and menstrual cycle length remained in the multivariate models, together explaining only 8% of the variance in TTP. CONCLUSIONS: Although information on several factors was available, the multivariate model explained only a small fraction of the variation in the observed time to pregnancies. Furthermore, female biological factors seemed more important predictors of TTP than lifestyle factors.     

Factors affecting respiratory system stability

Periodic breathing (recurrent central apneas) occurs frequently during sleep. Periodic breathing can arise as a result of unstable behavior of the respiratory control system. A mathematical model of the respiratory control system was used to investigate, systematically, the effect of severity of disturbances to respiration and certain system parameters on periodic breathing occurring during sleep. The model consisted of multi-compartment representation of O₂ and CO₂ stores, a peripheral controller sensitive to O₂ and CO₂, and a central controller sensitive to CO₂. The effects of hypoxia and hypercapnia on the upper airway muscles were not considered in the model. Episodes of hyperventilation or asphyxia were used to disturb the control system and explore the boundaries of stable breathing. Circulation time and metabolic rate were also varied. Simulations with the model produced the following findings: The number of central apneas associated with periodic breathing were greater as circulation time increased; controller gain increases also made the number of apneas greater, although periodic breathing occurs with lower controller gains as circulation time increases. At each level of circulation time there was a range of controller gain changes which caused little change in the number of apneas. There were more apneas with hypoxia; also the number of apneas increased with sleep-associated reductions in metabolic rate. The more rapidly resting PCO₂ rose at sleep onset, the greater the likelihood of recurrent apneas. Finally, the more intense the disturbance, the more apneas there were.     

A sensitive radioimmunoassay of insulin autoantibody: reduction of non-specific binding of [125I]insulin

There has been a lack of consensus among results of assays for insulin autoantibody (IAA) carried out by different laboratories, despite a reduction in the non-specific effect using a cold insulin competitor in radioimmunoassays (RIAs) for IAA in type I diabetes. We speculated that the discrepancies are partly a result of the non-specific binding (NSB) of [125I]insulin to unidentified molecules in serum on polyethylene glycol separation, and tried to improve IAA RIAs. The molecular weight of a candidate for the factor causing NSB was estimated to be about 700 kDa by gel filtration analysis, resembling that of alpha 2-macroglobulin (a2M). Further, the addition of purified a2M to the assay resulted in an increase in NSB. Screening revealed that heterocyclic compounds, such as isothiazolinone derivatives (ProClin300), were greatly effective at reducing NSB in control subjects from 2.904+/-0.909% to 1.347+/-0.254% (n=283, mean+/-SD, p<0.0001). Using our newly developed IAA RIA with ProClin300, the sensitivity for newly diagnosed type I diabetes patients (n=55) was 32.7% and 30.9% with or without insulin competition, respectively, whereas that of the former assay without ProClin300 was only 20.0%.     

Factors affecting the maintenance dose of warfarin.

AIM: To identify the possible factors determining the dose of warfarin prescribed in patients receiving anticoagulant treatment. METHODS: The computerised records of 2305 patients maintained on the drug in seven hospitals were amalgamated and classified into one of seven diagnostic groups. The associations with the dose of warfarin prescribed were investigated by univariate and multiple regression analysis. Differences between hospitals were studied with regard to the coagulometric method and the thromboplastin preparation used. RESULTS: The geometric mean dose of warfarin was 4.57 mg and 5% of patients were prescribed 10 mg or greater. There was a noticeable decrease in dose with increasing age, which averaged about 6 mg for patients aged 30 but 3.5 mg for those aged 80. Men required slightly more warfarin than women. Patients with heart disease or atrial fibrillation required lower doses of warfarin, while higher doses were required by patients with deep vein thrombosis. Significant differences in mean warfarin dose among the seven hospitals were evident. These differences could not be explained entirely by the use of different coagulometric methods or thromboplastins. CONCLUSIONS: Clinicians should be aware that older patients need reduced doses of warfarin. The considerable differences in doses of warfarin among hospitals indicates that further efforts to improve uniformity are required.