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Biomedical subjects

G C Zucchelli

Publications and source records attributed to G C Zucchelli.

At least 55 records · Page 3Linked to original sources
PubMed1982

Serum thyroid hormone concentrations and recovery of TSH secretion after excision of autonomously functioning thyroid nodules.

Serum concentrations of TSH, TT4, TT3 and rT3 were monitored for one month after excision of ten autonomous thyroid adenomas which had suppressed TSH secretion. Basal serum TSH levels start to increase between 30 hr and 20 days after surgery reaching normal and steady levels by the 24 day. Serum TT3 concentrations rapidly decrease in the first 20 hr to values near the lower limit of the normal range. Thereafter TT3 levels change little until pituitary TSH secretion recovers. Serum TT4 levels also fall, but much more slowly than TT3. Rising TSH levels stimulate residual extranodular thyroid tissue secretion of both TT3 and TT4. However, serum TT3 levels rise more rapidly than TT4 levels. Preoperative serum concentrations of both TT4 and TT3 are related directly to the time required until the beginning of the postoperative rise in TSH levels, and inversely with the maximal postoperative serum TSH concentration achieved. Throughout the study period, for all patients, serum TSH concentrations were inversely related to serum TT4 concentrations. These data suggest that, although the time required until the onset of recovery of TSH secretion is directly related to preoperative levels of TT4 and TT3, the regulation of postoperative TSH levels is dependent upon serum TT4 levels. Also, the serum TT3 levels constant at the lower limit of the normal range before recovery of TSH secretion, and the preferential rise in serum TT3 concentrations associated with rising TSH secretion, may prevent or abbreviate temporary postoperative hypothyroidism.

Adenoma↗
PubMed1980

Labeled metabolites appearing in human serum after 125I-triiodothyronine (T3) administration: a quantitative reappraisal.

The appearance in human serum of labeled iodothyronines arising from 3,5,3'-triiodothyronine (T3) catabolism was measured after bolus administration of 125I-T3. The use of column chromatography made it possible to separate in the plasma samples iodoproteins, iodide, T3 and a fourth peak ("pre-T3") eluting just before T3. The radioactivity associated with this pre-T3 peak was found to be 0.5% of T3 activity 30 min after injection, and reached a plateau value of 5.6% +/- 1.2 (mean +/- SD) from the 10th hr onward. From these data, we calculated that a maximal 5% underestimation in T3 metabolic clearance rate is inherent in those analytical methods that do not completely separate pre-T3 from T3 radioactivity. The MCR of 3,3'-diiodothyronine (T2) was also measured from the plasma disappearance curve after single injection of 125I-3,3'-T2. From these data and the mean disappearance curve of T3, the appearance curve of 3,3'-T2 in plasma was reconstructed by convolution under the assumption of a 100% conversion of T3 to 3,3'-T2. A plateau value of 4.6% of T3 activity was computed, very comparable to the experimentally determined 5.6%. This suggest that, if labeled 3,3'-T2 is the main component of the pre-T3 peak, the conversion into 3,3'-T2 represents a major pathway of T3 metabolism in man.

Chromatography, Gel↗
PubMed1979

Radioimmunoassay of lactate dehydrogenase, H forms.

Antisera to H4-lactate dehydrogenase (LDH) were elicited in rabbits, against both human (h) and porcine (p) isoenzymes. 125I-labelled H4-LDH was prepared by electrolytic iodination. A simple and fast procedure (1-h incubation for clinical assays) was set up by using polyethylene glycol for the bound-free separation. The results obtained in the antiserum characterization indicated that the heterologous homotetramer, M4 was completely discriminated in the porcine system, while a weak cross-reaction with human antisera resulted. In both cases, for the hybrid forms, a cross-reactivity level related to the stoichiometric contents of the H-subunit in the tetramers was observed. The H4-LDH from other species was found to be much more effectively disinguished in the porcine than in the human system. The assay for human LDH was further validated in terms of analytical suitability and clinical response. For healthy subjects the mean concentration was 0.46+/-19 micrograms/ml (mean+/-SD). Patients with acute myocardial infarction had levels ranging from 1.2 to 5.9 micrograms/ml.

Humans↗
PubMed1979

Triiodothyronine turnover studies in euthyroid patients with autonomous thyroid nodules.

Triiodothyronine (T3) kinetic studies were carried out using 126I-T3 and the single injection technique in eight clinically euthyroid patients with autonomous thyroid nodules and the metabolic results were compared to those obtained in a group of 12 healthy control subjects. Plasma labeled T3 concentration was measured by a chromatographic method based on the extraction of the hormone on Sephadex G-25 columns, followed by its elution with a specific anti-T3 antiserum. The analysis of the experimental plasma disappearance curves of the labeled hormone was performed using the noncompartmental method. The results obtained showed a significantly increased metabolic clearance rate of T3 in the patients with autonomous thyroid nodules, as compared to the control group. On the average, the T3 production rates were increased more significantly than the corresponding circulating levels of the hormone, therefore, suggesting that the significant TSH inhibition observed in the euthyroid patients with autonomous thyroid nodules could be related with an increased peripheral utilization of triiodothyronine.

Adolescent↗
PubMed1979

Radioimmunoassay of unconjugated and total serum estetrol using a 125I-iodinated tracer.

A radioimmunossay (RIA) for the measurement of both unconjugated and total serum estetrol has been developed, using an antiserum to an E4-3-conjugate and a 125I-radioiodinated E4 tracer. Assay of dried ethyl ether extracts was used for the determination of unconjugated E4, while a direct measurement of unextracted hydrolyzed serum in the presence of 0.3% 8-anilino-1-naphthalene sulphonic acid (ANS) proved adequate for total E4. Assay reliability was evaluated and the procedure standardized through a series of tests aimed at assessing accuracy, sensitivity and precision. No steroidal interference was found to practically affect the assay (0.3% estriol cross-reactivity), nor were solvent and sample blanks observed in the case of unconjugated E4. For total E4 assay, the sample blank effects were acceptably overcome by using hydrolyzed male serum and 0.3% ANS, as a standard diluent. An interassay variability amounting to approximately 10 and 6% resulted for unconjugated E4 and total E4 RIA, respectively. A number of serum samples (285 for unconjugated E4, 147 for total E4) randomly collected throughout normal pregnancy were assayed. The unconjugated E4 levels at 15th week and at term were 62.7 +/- 22.6 and 766.5 +/- 208.2 (SD) pg/ml, respectively. Total E4 was about 6--7 times higher than the levels of free E4 and increased 7 times from the 15th week to term.

Circadian Rhythm↗
PubMed1979

Effect of endogenous thyroid stimulating hormone levels on the secretion of thyroid hormones in man.

The effect of endogenous thyroid stimulating hormone (TSH) on the thyroid secretion of triiodothyronine (T3) and thyroxine (T4) was evaluated by serial determinations of serum T3. T4 and TSH concentrations in the following groups of patients: a) three patients submitted to surgical removal of a solitary, autonomous thyroid nodule which had completely inhibited the extranodular tissue; b) five subjects, with the same disease, in whom functional recovery of the extranodular tissue was induced by increased circulating TSH levels, produced by treatment with methimazole; c) one patient submitted to hemithyroidectomy for multinodular goitre; d) two hyperthyroid patients who had been treated with methimazole. In all these patients serum T3 and T4 levels progressively decreased, with a consequent progressive increase in serum TSH concentrations, leading to stimulation of the thyroid gland. During this TSH-induced stimulation of thyroid tissue, a significant positive correlation was found between the serum TSH concentrations and the corresponding ratio between the serum levels of T3 and T4 (T3/T4), both within each patient group (P less than 0.001) and among all patients (P less than 0.001). The same correlation also governs the relationship between the TSH and the T3/T4 values of 34 euthyroid control subjects and one patient with incipient hypothyroidism. These data strongly suggest that endogenous TSH can induce a preferential secretion of T3 over T4 by the human thyroid.

Goiter↗
PubMed1978

Evaluation of triiodothyronine (T3) kinetics in normal subjects, in hypothyroid, and hyperthyroid patients using specific antiserum for the determination of labeled T3 in plasma.

Triiodothyronine (T3) kinetics was evaluated using [125I]T3 and the single injection technique; 5 hypothyroid, 6 hyperthyroid patients, and 10 euthyroid control subjects were studied. Plasma-labeled T3 concentration was measured by means of a new method based on extraction of the hormone on Sephadex G-25 columns followed by elution with the specific antiserum. This technique allows a far better separation of the hormonal radioactivity from the labeled iodide produced from T3 catabolism in comparison with the TCA-precipitation-butanol extraction method. The analysis of the experimental data has been performed using non-compartmental treatment (integral approach); results of mono-compartmental analysis of the same data are also reported for comparison. Average metabolic clearance was 15.3 +/- 0.6 (mean + SEM) liters/day/m2 body surface in normal subjects; it was significantly decreased in hypothyroid patients (11.4 +/- 1.1) and significantly increased (33.4 +/- 4.0) in hyperthyroidism. The total plasma equivalent distribution volume was found significantly enlarged in hyperthyroid patients (22.6 +/- 0.9 liters/m2) in respect to that measured in the control group (15.6 +/- 0.4), whereas it was not different from normal value in hypothyroid patients (17 +/- 1.7). Using plasma concentration of native T3, absolute turnover rate and extrathyroidal pool were also estimated; their values were 6.5, 23.7, and 131.7 micrograms/day/m2 and 10.1, 24.2, and 90.6 micrograms/m2, respectively, in hypothyroid, normal, and hyperthyroid groups.

Adolescent↗
PubMed1977

Direct radioimmunoassay of estradiol in serum extracts.

The feasibility of direct radioimmunoassay of unconjugated estradiol in dried serum extracts in the assessment of ovarian function in the regulation of the menstrual cycle has been investigated. Using an antiserum to an estradiol-6-conjugate, assay reliability was evaluated and the procedure standardized through a series of tests aimed at assessing accuracy, sensitivity, and precision. These included multiple titration with competing steroids, the definition of blank effects from solvent and sample, the assay both of samples to which known amounts of estradiol had been added and of serially diluted samples, and clinical validation using as a reference samples related to well-defined physiological situations. The variability of replicate estimates and the repeatability of the calibration curve were evaluated to obtain information on assay precision and sensitivity. The analytical performances proved to be perfectly adequate for the clinical purposes for which the assay was intended, in terms both of reliability of results and of methodologic practicability.

Animals↗
PubMed1975

Measurement by radioimmunoassay of unconjugated estriol in pregnancy serum.

Antisera to estriol 6--onjugates were tested for suitability in the direct radioimmunoassay of unconjugated estriol in extracts of pregnancy serum. Assessment of specificity through titration with competing steroids allowed a selection to be made within the group of antisera. The measurement was then standardized by checking the absence of analytical blank (solvent and sample blank) and the extent of binding variability associated with the use of charcoal-dextran as a separating agent. Validation was made by means of the usual recovery and dilution tests, and by a cross-comparison of analytical data obtained with different antisera; reproducibility of calibration curve and within-and between-assay variability was evaluated under routine conditions. The validity of the clinical information was assessed by assaying 202 samples randomly collected throughout normal pregnancy from the 16th week to term: both trend and levels of unconjugated estriol concentration were found to be in good agreement with the literature data.

Animals↗
PubMed1975

Automatic treatment of radioimmunoassay data: an experimental validation of the results.

A computational method for the automatic treatment of radioimmunoassay data has been developed and a computer program has been written in accordance. The main features of the approach used are the following: (a) a constant ratio between the bound fraction and its variance is assumed and estimated in each assay; (b) the points of the dose-response curve are fitted using the three-parameter function y' equals b1/(1 plus b2x(-b)3) where y' equals bound - nonspecific counts and x is the amount of hormone; the fitting is performed using the nonlinear, least-squares technique; (c) the values of the unknown samples are evaluated from the fitted standard curve; their confidence limits are computed taking into account both the variance of the bound replicates and the variance of the parameters of the dose-response curve. Experimental data that support the validity of the assumption on the variance of bound measurement and the suitability of the chosen function to fit the points of the standard curve are presented. A comparison between the confidence limits of the unknowns experimentally obtained and those computed by the program is reported and discussed.

Analysis of Variance↗
PubMed1975

Results of a comparative study on insulin radioimmunoassay in 36 Italian laboratories.

An interlaboratory study in which the insulin contents of five plasma samples were estimated in 36 italian laboratories was coordinated by the Istituto Superiore di Sanità (National Institute of Health) and the Consiglio Nazionale delle Ricerche (National Research Council). A rather large between-laboratory variability resulted, though the ranking of samples according to their insulin concentrations was practically the same. A significant dependence of estimates on the method used was established. The analysis of data, aimed at defining the possible reasons of the assay variability, is reported and discussed.

Insulin↗
PubMedDate not supplied

Comparison of immunoassays for tumor markers CA 19-9, CA 15-3 and CA 125: data from an international quality assessment scheme.

Data collected in the 1993 and 1994 cycles of an international external quality assessment (EQA) program and in a national multicenter collaborative study were cumulatively analyzed to evaluate the standardization of the methods currently in use for the assay of mucinous tumor markers CA 19-9, CA 15-3 and CA 125. On average the between-laboratory variability was 15.2 and 16.0 CV% for CA 15-3 and CA 125 respectively; the between-laboratory variability found for CA 19-9 was markedly worse (mean 28.3 CV%). The variability component attributable to systematic differences between different methods/kits was relatively small for CA 15-3 and CA 125 (18% and 24% of the total variability) but markedly larger for CA 19-9 (48% of the total variability). The agreement of CA 19-9 results worsened in the last few years when new nonisotopic techniques became available. The precision of the methods/kits most used in the survey ranged from 9.9 to 13.3 CV% for CA 125 and from 11.6 to 13.9 CV% for CA 15-3. For these two tumor markers the precision of the traditional IRMAs does not appear different from that of the new fully automated nonisotopic techniques. The precision of CA 19-9 methods was on average worse (from 11.7 to 19.6 CV%) although two automated systems exhibited a precision better than that of IRMAs. In conclusion, the results of this study indicate that CA 15-3 and CA 125 are satisfactorily assayed whereas CA 19-9 assay appears affected by larger differences between methods and by poorer precision of laboratories and kits.

Antigens, Tumor-Associated, Carbohydrate↗