Biomedical subjects
Publications and source records attributed to K Thomas.
As important discrepancies in blood concentrations of LH-RH remain, the basic problem of the specificity of the radioimmunoassay was reinvestigated using an antiserum raised against a new conjugate (33). Cross-reactions with related and unrelated peptides were studied in both charcoal-dextran and second antibody methods of separation. The possible relation between the nature of the conjugate and the specificity is discussed.
Comparison of standard curves with different concentrations of human plasma in the medium of incubation is presented. It appears that Bo varies with the dilution although the ratio B/Bo is independent of the dilution. This last observation was used to research 'endogenous' LH-RH in four menstrual cycles, in postmenopausal women and in men. The validity of the dosage is discussed in a more general way in the light of the results published in the literature.
The rate of disappearance of intravenously injected LH-RH was studied in 6 human volunteers. The blood samples were taken every 20 sec from the time of injection to time +5 min and every 30 sec from time +5 min to time +10 min. The half-life of LH-RH was calculated in the interval of 3-10 min, and was found to be 2.4 +/- 0.4 min. The amounts of LH-RH estimated in the vascular compartment were relatively low when compared to the total amount of injected LH-RH. This observation suggests a rapid and important passage towards the extravascular compartment.
Application of a porcine relaxin radioimmunoassay system using Bolton and Hunter reagent was characterized in different biological fluids. In pregnant woman, plasma reveals concentrations from undetectable values to 1,800 pg/ml. Maximal concentrations are found between the 8th and the 13th weeks of pregnancy. These peak values are significantly different from those at other stages of pregnancy. Appreciable relaxin concentrations are detected in gestational corpus luteum extract, and in corpora lutea cyst fluid of pregnant and nonpregnant women. No relaxin was detected in a cyclus corpus luteum extract, in a placental extract, or in an ovarian serous cyst. The presence of immunoreactive relaxin in the nonpregnant woman is reported.
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This work was carried out on 151 estimations of the radioimmune levels of hCG-hCG beta in the first half of normal pregnancy and 390 levels estimated in 10 molar pregnancies, in 4 choriocarcinomata following moles and 1 primary choriocarcinoma of the ovary using homologous hCG beta. In normal pregnancy the level of hCG-hCG beta rises rapidly. The levels are highest between the 8th and 9th weeks of pregnancy, and then gradually decrease. In active molar pregnancies the levels of hCG-hCG beta in the plasma are significantly higher than those found in normal pregnancies of the same gestational age. When the outcome is going to be favourable the levels drop progressively. Complete absence in peripheral blood is usually found about 14 weeks after a mole has been expelled or evacuated. In choriocarcinomata, if the level of hCG-hCG beta rises it is a certain sign of reactivation of the tumour.
Twenty-six patients seeking advice for sterility were given courses of treatment with HMG-HCG. Ovarian maturation was followed by daily evaluation of plasma 17beta-oestradiol concentrations. HCG was administered as soon as 17beta-oestradiol levels reached 250 pg/ml. In a first group of 7 amenorrheic patients with lack of oestrogen activity, a pregnancy rate of 71.4% and an ovulation rate of 91.7% were achieved. In a second group of 5 amenorrheic patients showing evidence of oestrogen activity, a pregnancy rate of 80.0% and an ovulation rate of 100% were obtained. In a third group of 14 oligomenorrheic patients, the pregnancy rate attained 71.4% and the ovulation rate 96.9%. The overall pregnancy rate was 73.0%. With this procedure of monitoring HMG-HCG treatment by means of plasma 17beta-oestradiol levels, the multiple pregnancy rate reached only 11.7% and only one case of mild ovarian hyperstimulation was observed. Pre-ovulatory and pre-conceptional 17beta-oestradiol concentration were identical with those observed in spontaneous ovulatory cycles with or without conception.
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Total RNA was extracted from 24 h old mycelia of Phycomyces blakesleeanus which had been grown in liquid culture. Heavy molecular weight RNA was fractionated on 2.6% polyacrylamide gels. 1. The main cytoplasmic ribosomal RNA fractions had molecular weights of 1.34 and 0.72-16(6). 2. [3H]Uridine pulse labelling of cultures revealed an initial ribosomal RNA precursor of molecular weight 2.5-10(6). 3. An intermediate precursor for the 1.34 - 10(6) dalton peak was found, having a molecular weight of 1.6-10(6). 4. Pulse-chase experiments, using [3H]methionine, showed the flow of synthesis as being (see article). 5. Mature 0.72-10(6) dalton RNA appeared prior to the 1.34-10(6) dalton RNA but no immediate precursor for it was detected.
After treatment with papain (6 mg/ml) for 1 h, P815 tumor cells became resistant to complement-mediated lysis by mouse alloantibodies of different specificities. Immunofluorescence and absorption studies indicated that this resistance was associated with removel of the corresponding antigenic determinants from the cell surface. In contrast, papain-treated tumor cells were fully susceptible to lysis by rabbit antiserum against P815 cells, indicating a) no alteration of the membrane sensitivity to complement damage, and b) a dissociation between structure and/or localization of allo- and xenoantigens. Papain-treated cells were also completely resistant to lysis by cytolytic T lymphocytes (CTL) during the first 60 min after completion of the enzyme treatment. Susceptibility to lysis by either CTL or alloantibody and complement reappeared within a few hours after incubation in culture medium and was virtually normal by 6 h. Treatment of P815 cells with trypsin (2 mg/ml) had no effect on either humoral or cellular lytic activities.
Plasma unconjugated estrone (E1), estradiol-17beta (E2) and estriol (E3), and HCS were measured in the same plasma samples collected throughout pregnancy in 19 gestational diabetics (GD) and 21 diabetics (D). When compared to the results obtained in 22 normal subjects, plasma levels of E1 and E2 were significantly elevated in D in the second half of gestation. The results were intermediate although closer to the normals, in GD. E3 values were not different from the normals in both D and GD. HCS values were lower than normal in early pregnancy in both D and GD. In late pregnancy HCS levels were not different from normal in either D or GD, although some individual values were much above the upper limit in some diabetic patients. The hormonal ratios in D and GD parallel those in normals, although E3/E2 and HCS/E2 were lower in D. These results are discussed with respect to the different behaviour of E2 and E3, taking into account the difference in their respective biosynthetic pathways. Besides a possible quantitative modification of the placental function in D, the results could tentatively be explained by a qualitative change in the fetal estrogen precursors to placental aromatization, in favour of the 16 non-hydroxylated compound. However, maternal modifications in precursor production or in estrogen metabolism can be an alternative hypothesis. Finally, the present work does not support the hypothetical estrogen deficiency in diabetic pregnancy. Estrogen treatment appears to have no objective justification.
Sex hormone-binding globulin (SHBG) capacity was measured in a longitudinal study in plasma samples from normal subjects, diabetics, and gestational diabetics and throughout pregnancy, together with unconjugated plasma estradiol. In normal women SHBG capacity (expressed in ng DHT bound per ml of plasma) increased from 23.7 +/- 13.7 (SD) in the 5-8th week period, to 74.5 +/- 20.7 in the 17-20th week period, and to 102 +/- 24 in the 37-40th week period. In diabetics the SHBG capacity for the same periods of time were respectively: 25.3 +/- 17.2, 83.1 +/- 29.1, and 111.6 +/- 22.6. Plasma levels of unconjugated estradiol were 55% higher in the diabetics than in the normal subjects in the second half of gestation, as reported in detail in another publication. From the imbalance between the close to normal SHBG capacity and the higher plasma levels of unconjugated estradiol in the diabetics, it is suggested that the unbound, i.e., metabolically active, fraction of plasma estradiol reaches higher levels in diabetics than in normal subjects in the second half of gestation.
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A study of the fine structure of human thymus, including normal hyperplastic and with thymoma, is reported in this paper. There is increasing experimental evidence that thymic epithelial cells are a source of hormone. It is, therefore, of interest that we found epithelial cells containing intravesicular cytoplasmic material that reacted with silver methenamine as do mucoproteins. Similar material, possibly extracellular, was seen in close contact with lymphocytes and macrophages in the thymus. The results suggest a possible mechanism for epithelial cell/lymphocyte interaction. Some epithelial cells also showed phagocytic features and all appear to play a structural role. The presence of nuclear pockets was noted within lymphocyte nuclei.