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Biomedical subjects

T Chard

Publications and source records attributed to T Chard.

At least 379 records · Page 21Linked to original sources
PubMed1976

In vivo activation of synthetic hormonogens of lysine vasopressin: Na-glycyl-glycyl-glycyl-[8-lysine]vassopressin in the cat.

The urine and plasma levels of vasopressin-like immunological activity and of antidiuretic activity were examined following injection of Na-glycyl-glycyl-glycyl-[8-lysine]vasopressin (triglycylvassopressin, TGLVP) in 3 cats. The plasma levels of immunoreactive material were initially high, and fell rapidly. The levels of antidiuretic activity showed considerable variation; the overall pattern was strikingly different from that demonstrated by radioimmunoassay, and all 3 animals showed a rise in plasma antidiuretic activity in the early part of the experiment. Following injection of lysine vasopressin (LVP) the pattern of disappearance of both biological and immunological activity was similar. The total amount of immunoreactive material found in the urine was greater than the amount of antidiuretically active material. These results clearly demonstrate that the antidiuretic activity of TGLVP is mainly due to its conversion to LVP in vivo.

Animals↗
PubMed1976

Comparison of the redox bioassay with other assays for luteinizing hormone.

The cytochemical (redox) bioassay for LH has been compared with established LH assays. Measurements made by redox bioassays were considerably lower than those made by radioimmunoassay in human female plasma samples obtained at mid-cycle. There was no apparent relationship between measurements on incubation media from cultures of sheep pituitary glands made by redox bioassay and the ovarian ascorbic acid depletion (OAAD) assay. After polyacrylamide gel electrophoresis of a crude extract of a human pituitary gland, redox LH measurements were lower than those of the OAAD assay and radioimmunoassay in the cathodal segments of the gel. By contrast, there was reasonable agreement between LH measurements made by radioimmunoassay and redox assay in cathodal fractions from gel electrophroesis of a purified pituitary LH preparation. Follicle-stimulating hormone, and the alpha- and beta-subunits of LH depressed the response of intact LH in the redox assay; this might explain the relatively low levels of LH measured by redox assay in some of the experiments described. Which type of assay best reflects the biological activity of LH in man remains to be determined.

Animals↗
PubMed1975

Levels of alpha-fetoprotein in maternal blood as a screening test for fetal neural-tube defect.

A range has been established for maternal plasma-alpha-fetoprotein (A.F.P.) levels in normal pregnancies (930 women). A.F.P. levels between 10 and 40 weeks gestation were examined in 51 pregnancies associated with fetal neural-tube defect. In 96% of cases (20 anencephalus, 6 spina bifida) examined between 16 and 26 weeks of gestation A.F.P. levels were above the 95th centile of the normal range. It is suggested that measurement of A.F.P. in maternal blood should become a screening test in all pregnancies, and a scheme for the futher investigation of patients with abnormal results is described.

Anencephaly↗
PubMed1975

Serum fibrin(ogen) degradation products in diagnosis of deep-vein thrombosis and pulmonary embolism after hip surgery.

Levels of fibrin(ogen) degradation products (F.D.P.) have been measured by radioimmunoassay for degradation product E (FgE) and by tanned-red-cell haemagglutination-inhibition immunoassay (T.R.C.H.I.I.) in the serum of thirty-three patients undergoing total hip replacement. Levels of F.D.P. did not correlate with thermographic evidence of deep-venous thrombosis. However, in 34 patients with pulmonary embolism, levels of F.D.P. measured by the T.R.C.H.I.I. were transiently raised at the time of embolus, and FgE concentrations were increased for up to 5 days preceding the embolus. Since the measurments of FgE is simple, convenient, and cheap, this estimation might constitute a valuable screening test for major thromboembolic episodes in the postoperative period.

Aged↗
PubMed1975

A comparison between radioimmunoassay and other immunological techniques for the measurement of fibrinogen/fibrin degradation products in serum.

Fibrinogen/fibrin degradation products (FDP) have been measured in serum by radioimmunoassay for fragment E (FgE), one of the terminal fragments in plasmic digestion of fibrinogen, and the results compared with those determined by both a tanned red cell haemagglutination inhibiton immunoassay (TRCHII) and a latex particle agglutination inhibition immunoassay. The detection limit of the FgE assay was 0.8 ng/ml, that of TRCHII was 625 ng/ml and the latex particle agglunitaion inhibition immunoassay was 10 mug/ml. All the samples measured had detectable levels of FDP with the FgE assay, whereas only 88% were measurable with the TRCHII and 2% by the latex particle agglutination inhibition immunoassay. A comparison of those samples giving a positive result with both the TRCHII and FgE assay showed overall agreement between the results of the two types of assay, but there was considerable scatter of FgE levels at each point of the TRCHII. The major advantages of the radioimmunoassay system are greater sensitivity, specificity and reproducibility.

Anemia, Sickle Cell↗
PubMed1975

The development of radioimmunoassays for fibrinogen degradation products: fragments D and E.

Fibrinogen degradation products, fragment D (FgD) and fragment E (FgE) have been measured in human serum by specific radioimmunoassays. In addition, the appearance of a neoantigenic determinant on FgD, revealed when fibrinogen is degraded by plasmin has been utilized to develop a specific radioimmunoassay for FgD in plasma (FgDneo). The reagents and conditions used in each assay are described in detail. The mean specific activity was 144 muCi/mug for 125I-labelled FgE and 82 muCi/mug for 125I-labelled FgD. Separation of antibody bound and free antigen was achieved using second antibody. The detection limits of the FgE, FgD and FgDneo assays were 0.8, 1.0 and 6.2 ng/ml respectively. The specificity of each assay with respect to fibrinogen and its degradation fragments has been assessed. Fibrinogen and fragment X cross-reacted markedly in both the FgE and FgD assays, whereas the cross-reaction of fibrinogen was abolished in the FgDneo assay, while the cross-reaction of fragment X was 10%, indicating gradual emergence of the neoantigenic site during digestion of fibriogen. The sensitivity, precision, and specificity of the radioimmunoassay systems described have major advantages over the existing procedures for the measurement of fibrinogen degradation products.

Antibody Specificity↗
PubMed1975

The distribution of placental lactogen in the human term placenta.

Serial frozen sections of human term placentae were examined by quantitative morphology and, after extraction, by a radioimmunoassay for human placental lactogen (HPL). The total quantity of HPL in the placenta was estimated as 720 mg. The amount of HPL was related to the amount of trophoblast in any area, but otherwise did not vary in different parts of the placenta. A semi-logarithmic relationship was observed between the amount of HPL and the percentage trophoblast in a section. It is suggested that the amount of HPL in a given area of the placenta is related to the blood-flow in that area.

Cell Count↗
PubMed1975

Circulating levels of fibrin/fibrinogen degradation fragment E in normal pregnancy, and in association with intrauterine growth retardation and perinatal asphyxia.

Levels of fibrin/fibrinogen degradation products have been measured by aspecific and sensitive radioimmunoassay for degradation fragment E (FgE) in pregnant patients. Maternal FgE levels rose from the 16th week reaching a plateau at the 36th week in normal pregnancy. There was no correlation between maternal FgE levels and maternal age, parity or the occurrence of perinatal asphyxia. A minority of patients (5 per cent) with evidence of intrauterine growth retardation showed prolonged elevation of FgE levels.

Asphyxia Neonatorum↗
PubMed1975

Maternal plasma alphafetoprotein levels in the second half of normal pregnancy: relationship to fetal weight, and maternal age and parity.

A semi-automated radioimmunoassay for plasma alphafetoprotein has been developed, suitable for routine clinical use. Several hundred samples can be assayed in a working week, with results available within 24 hours. The use of extensive quality controls ensures that good precision is maintained both within and between assays. The range of plasma concentrations of alphafetoprotein in the second half of pregnancy has been established in 100 normal subjects. The levels rise progressively to reach a peak at 32 weeks, and thereafter fall until term. No relationship between circulating alphafetoprotein levels and birth weight was observed.

Adult↗