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Biomedical subjects

H Griffiths

Publications and source records attributed to H Griffiths.

At least 91 records · Page 5Linked to original sources
PubMed1992

Measurement of pharyngeal transit time by electrical impedance tomography.

The feasibility of using electrical impedance tomography (EIT) for measuring pharyngeal transit time has been investigated. Imaging sequences were obtained on the neck in a group of eight healthy subjects when swallowing solutions of different electrical conductivities. The solutions used were aqueous Dioralyte (1.5 S m-1) and tap water (0.04 S m-1). The effects of movement upon the images were large compared with the changes due to the solutions, but these were cancelled by a subtraction technique. The mean value of the EIT pharyngeal transit time parameter was 370 +/- 120 ms. EIT has the advantage that repeated measurements could be performed without fear of hazard in contrast to the established technique of video fluoroscopy which involves ionising

Adult↗
PubMed1992

Predictors of infection in chronic lymphocytic leukaemia (CLL).

A group of patients with chronic lymphocytic leukaemia (CLL) were studied to determine whether particular clinical and laboratory parameters might help to identify those patients at risk of recurrent infection who would benefit from immunoglobulin replacement therapy. The case notes of 59 patients were reviewed with regard to stage and duration of disease, chemotherapy and frequency of infection over the preceding 2 years. Serum IgG levels and specific antibodies to tetanus, diphtheria and pneumococcal capsular polysaccharide were measured at the end of the 2-year period. A group of 56 healthy age-matched volunteers were used as controls. Eighteen patients had severe or multiple infections during the study period, 11 patients had recurrent infections and the remaining 30 patients had only minimal infections. Overall, serum IgG levels were low in 32 patients but in none of the control group (P = 8.8 x 10(-11). However, less than half of those patients with hypogammaglobulinaemia suffered from severe or multiple infections. Specific antibodies to pneumococcal capsular polysaccharide were low in 23 patients compared with six of the control group (P = 4.9 x 10(-4)). The majority of patients with severe or multiple infections (13/18) had low levels of both total IgG and specific antibodies to pneumococcal capsular polysaccharide. However, in the groups of patients with less frequent infections, a higher proportion had low serum IgG than low pneumococcal antibody levels. Low levels of pneumococcal antibodies were particularly associated with severe or multiple infections (P = less than 0.00001).

Aged↗
PubMed1992

Comparison of methods for the determination of unbound triiodothyronine in pregnancy.

OBJECTIVE: To study the changes in unbound T3 concentration in the first trimester of pregnancy. DESIGN: We measured serum unbound T3 concentration before and after termination of pregnancy. PATIENTS: Twenty-six clinically euthyroid women. MEASUREMENTS: We used one non-analogue assay (Sclavo) and three analogue assays (Amersham, Becton Dickinson and Diagnostic Products Corporation). RESULTS: Regression analysis did not show any significant agreement between the analogue and non-analogue assays. After termination of pregnancy, unbound T3 concentration as measured by Sclavo and Amersham assays did not change whereas unbound T3 concentration increased and decreased as measured by Becton Dickinson and Diagnostic Products assays respectively. Changes were not directly related to albumin or thyroid binding globulin. CONCLUSION: We believe unbound T3 concentrations as measured by the analogue assays used in this study are due to a balance of errors and cannot be used to determine true physiological changes in pregnancy.

Abortion, Induced↗
PubMed1992

Immunogenicity and safety of PRP-T conjugate vaccine given according to the British accelerated immunisation schedule.

The immunogenicity and safety of a new Haemophilus influenzae type b conjugate vaccine, PRP-T, was studied in 107 infants from the Oxford district. The vaccine was given concurrently with diphtheria, pertussis, tetanus, and polio vaccines at 2, 3, and 4 months of age. Symptoms after immunisation were recorded by a parent. Sera were obtained before the first immunisation and at 5 months of age and the antibodies were measured by both radioimmunoassay and enzyme linked immunosorbent assay (ELISA). No serious adverse reactions were observed and there was no increase in the incidence of expected minor side effects. By radioimmunoassay, the geometric mean titre of serum anticapsular antibody increased from 0.09 micrograms/ml before immunisation to 5.01 micrograms/ml after three immunisations. Ninety eight per cent of children had antibody concentrations consistent with protection (greater than or equal to 0.15 micrograms/ml). IgG antibody concentrations measured by ELISA correlated well with total antibody concentrations measured by radioimmunoassay (r = 0.864). These results provide encouragement that routine immunisation against H influenzae type b at 2, 3, and 4 months of age, could prevent most cases of disease in children in the UK.

Age Factors↗
PubMed1992

Human chorionic gonadotropin may not be responsible for thyroid-stimulating activity in normal pregnancy serum.

Although hCG can activate thyroid cells in culture there is considerable doubt as to whether it is responsible for the changes in thyroid function which occur during normal pregnancy. Thyroid-stimulating activity (TSA), measured using iodide uptake into FRTL-5 cells, was demonstrated in 32/51 (63%) first and 15/29 (52%) third trimester sera. Free T3 was increased (P less than 0.001) and TSH decreased (P less than 0.01) in first trimester. In the early pregnancy group there was a positive correlation between hCG and TSA (r = 0.594, P less than 0.001) and a negative correlation between hCG and TSH (r = -0.329, P less than 0.02). In third trimester hCG concentration was often below that required to produce TSA in vitro and TSA could not be neutralized by antibodies to hCG. There was no correlation between hCG and TSH or thyroid hormones in the third trimester. In 26 women TSA decreased in parallel with serum hCG concentration after termination of pregnancy (P less than 0.001). Free T3 also decreased (P less than 0.01) and TSH increased (P less than 0.05) after termination. TSA persisted in many patients even after hCG was either very low or undetectable. Purified hCG stimulated iodide uptake in a concentration-dependent manner. Stimulation of iodide uptake by TSH was inhibited by the simultaneous presence of low concentrations of hCG while activity was restored with high concentrations. hCG may contribute to the thyroid changes in early pregnancy. However the poor correlation between TSA and thyroid tests suggests that other factors may be involved. The partial agonist activity of hCG may account for some of the inconsistencies observed but TSA in serum from late pregnancy or after termination of pregnancy is almost certainly due to another hormone or growth factor.

Adult↗
PubMed1991

Hypogammaglobulinaemia in low grade B cell tumours; significance and therapy.

Bacterial infection is an important cause of morbidity and mortality in patients with B-cell tumors; this is related to their secondary hypogammaglobulinaemia. Two studies of intravenous replacement therapy [IVIg] have been performed in such patients: a crossover study over two years and a randomised, multicentre study over one year. Both involved infusions of IVIg [400 mg/Kg] or an equivalent volume of saline every three weeks for one year. In both studies, serious bacterial infections were considerably reduced by IVIg. Viral and fungal infections were uncommon. In the crossover study bacterial infections were more frequent in periods in which patients serum IgG levels were below the normal range [less than 6.4 g/l]. The sites of bacterial infection were similar in these studies to those in previously published reports, namely respiratory tract, skin, urinary tract and blood. There were a few mild adverse reactions which were related to the rate of infusion, but no serious toxic effects. Haematological parameters were not significantly changed by IVIg at this dose and disease progression did not appear to be changed.

Agammaglobulinemia↗
PubMed1990

Reactive oxygen species modify human DNA, eliciting a more discriminating antigen for the diagnosis of systemic lupus erythematosus.

During the development of an ELISA to measure anti-DNA antibodies in systemic lupus erythematosus (SLE) sera, native dsDNA was found not to be the most appropriate antigen to use in ELISA assays for differentiating between SLE patients and those with rheumatoid arthritis (RA), a disease also associated with circulating serum anti-DNA antibodies. By modifying the ELISA technique to incorporate human DNA, denatured by reactive oxygen species, to detect anti-DNA antibodies in SLE sera, results consistently showed an increase in antibody binding when compared with the native antigen; no such trend was observed in the comparable group of RA patients. Using this assay serum anti-dsDNA antibody levels were measured in a group of 20 controls, 20 RA patients (10 seropositive and 10 seronegative) and 30 SLE patients (15 with clinically active disease, 15 with inactive disease). A comparison with the standard radioimmunoassay used to measure anti-DNA antibodies for the diagnosis of SLE showed that the ELISA assay using modified DNA performed better than the standard radioimmunoassay offering an improvement in both clinical specificity and sensitivity. The improved method particularly reduced the problem of false-negative results for SLE patients shown clinically to be either mildly active or inactive.

Adult↗
PubMed1990

Thyroid function in choriocarcinoma: demonstration of a thyroid stimulating activity in serum using FRTL-5 and human thyroid cells.

Hyperthyroidism is a well recognized complication of gestational trophoblastic tumours (GTT) and may be due to high circulating concentrations of human chorionic gonadotrophin (hCG) or its variants. We have studied 24 clinically euthyroid women with GTT. Eight were biochemically hyperthyroid with low or undetectable serum thyrotrophin (TSH) and had a mean serum hCG of 361.2 x 10(3) IU/l compared to 76.2 x 10(3) IU/l in the other patients (P less than 0.01). Purified hCG stimulated iodide uptake into FRTL-5 cells with 25 x 10(3) IU/l being equivalent in potency to 1 mU/l of thyrotrophin (TSH). Sixteen out of the 24 sera (67%) stimulated iodide uptake when applied to the cells at a 1:10 dilution. Sera from all eight hyperthyroid patients contained thyroid stimulating activity. The mean hCG concentration in the 16 stimulatory sera was 238.2 x 10(3) IU/l compared to 37.1 x 10(3) IU/l in the other eight sera (P less than 0.01). Six men with hCG-secreting testicular tumours were biochemically euthyroid although three of their sera stimulated iodide uptake into FRTL-5 cells. In human thyroid cells the mean cAMP production over 4 h with sera from five healthy controls was 54.2 +/- 1.81 pmol/mg cell protein compared to 67.0 +/- 3.8 pmol/mg protein with sera from five choriocarcinoma patients (P less than 0.02). Serum from patients with gestational trophoblastic tumours contains a thyroid stimulating activity which may be hCG and whose presence correlates with hyperthyroidism.

Adolescent↗
PubMed1990

Thyroid-stimulatory effects of human chorionic gonadotrophin in early pregnancy. In vivo and in vitro studies.

Human chorionic gonadotrophin (hCG) shares structural similarity with pituitary thyrotrophin (TSH) and may act as a thyroid stimulator. We have studied serum hCG levels, thyroid function tests and the ability of serum to stimulate cultured thyroid cells in 40 subjects between 6 and 12 weeks of pregnancy. Serum free tri-iodothyronine was increased and serum TSH reduced in pregnancy samples (both p less than 0.05). hCG was detectable in all pregnancy sera with a mean level of 105.6 X 10(3) U/l. Serum from 24 of the 40 (60%) patients stimulated iodide uptake into cultured FRTL-5 thyroid cells. The potency of sera in stimulating cells correlated with the hCG level (r = 0.710, p less than 0.01). The stimulatory activity in some, but not all, sera could be specifically neutralized with antiserum to hCG. Partially purified hCG stimulated iodide uptake and growth of thyroid cells at concentrations of 50 X 10(3) U/l and above. In these experiments, 25 X 10(3) U/l of hCG produced equivalent stimulation to 1 mU/l of TSH. In 8 patients tested before and after termination of pregnancy, the thyroid-cell-stimulatory activity of serum declined rapidly in parallel with serum hCG. hCG may stimulate the thyroid gland at concentrations which prevail in normal pregnancy. Its potential as a physiological regulator of the thyroid gland is not widely appreciated and requires further study.

Adolescent↗
PubMed1990

A general surgeon in Vietnam: lessons learned the hard way.

As a general surgeon in Vietnam, I learned about readiness, preparation, survival, and support the hard way. Tri-Service cooperation training, logistics, personnel utilization, and evacuation will help to provide the best possible care to our troops.

General Surgery↗
PubMed1989

A dual-frequency electrical impedance tomography system.

An electrical impedance tomography (EIT) system has been constructed, operating at two frequencies, 40.96 and 81.92 kHz, for investigating the practicability of the dual-frequency imaging method discussed theoretically in a previous paper. For testing the system, a phantom with a frequency-dependent electrical conductivity was designed. The properties of the phantom can be adjusted to match the frequency dependence observed in a given type of tissue. Dual-frequency images were obtained from a phantom simulating liver and also from 200 g of porcine liver in a saline tank. Prior to image reconstruction, it was necessary to apply a correction to the data to cancel the effects of stray capacitance within the electronics.

Animals↗