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Biomedical subjects

B N Premachandra

Publications and source records attributed to B N Premachandra.

At least 55 records · Page 3Linked to original sources
PubMed1979

Association of prealbumin deficiency with alpha-1-antitrypsin deficiency.

Prealbumin (PA) measurements were made by electrophoretic and radial immunodiffusion techniques in three alpha-1-antitrypsin deficient Pi-D) serum samples. The deficiency was characterized as phenotype ZZ (homozygous). In two out of three serums PA was undetectable, as revealed by the absence of radiothyroxine distribution in the PA area, whereas quantitative estimates of PA by radial immunodiffusion showed very low levels (2--7 mg/100 ml) thus corroborating electrophoretic observations; low PA binding of T4 tracer was noted in another Pi-D serum. The total protein and laboratory thyroid function (thyroxine, triiodothyronine, and free thyroxine index concentration) measurements were normal, and the decrease in PA could not be explained on the basis of surgery, protein malnutrition, or cirrhosis. These and other observations described in this preliminary communication have served to raise the possibility of severe prealbumin deficiency being associated with alpha-1-antitrypsin deficiency, while the presence of low-but-not-absent PA in another Pi-D case might also suggest subgroup classification of the phenotype ZZ based on degrees of PA deficiency.

Adult↗
PubMed1979

Thyroid hormone levels during glucose tolerance test in euthyroid subjects.

Twelve normal, healthy, clinically and biochemically proven euthyroid volunteer subjects (age 19-35) were administered a standard glucose tolerance test (100 g glucose orally) and thyroxine (T4), triiodothyronine (T3) and reverse triiodothyronine (rT3) levels were determined by specific radioimmunoassays to determine the acute effect of glucose and insulin on peripheral monodeiodination of thyroxine. The fasting levels of T4, T3, rT3 and free thyroxine were 82.4 nmol/l, 1.7 nmol/l, 0.52 nmol/l, and 0.22 nmol/l, respectively, and these levels were unchanged during the 3 hours post-glucose load. The rise and fall of glucose and insulin levels were typical of the standard responses normally observed in the glucose tolerance test. The variations in insulin and glucose levels were not correlated with thyroid hormone concentrations at any interval during the test. It is therefore concluded that dietary glucose does not acutely cause shifts in peripheral monodeiodination of thyroxine in healthy euthyroid subjects.

Adult↗
PubMed1978

Radioimmunoassay of reverse triiodothyronine.

rT3 RIA standard curves were generated using rT3 standards from various sources. The rT3 antiserum and the method of free and bound hormone separation used were the same in all assays. The slopes of rT3 RIA curves differed considerably; standard curves generated with Henning (Berlin) rT3 standard had the steepest slope. Because of the differences in slopes of standard curves, bound to free estimates, when extrapolated from standard curves generated with various rT3 standards, resulted in 2- to 3-fold differences in rT3 assay values in the same sera. Circulating rT3 concentration in human sera was 20 ng/100 ml when Henning rT3 standard was used in the assay, whereas with Jorgensen's rT3 standard, a value of 42 ng/100 ml was noted. As the rT3 antiserum and assay conditions used were identical in all comparisons (except rT3 standards), the 2- to 3-fold differences in rT3 values noted in the same sera suggested variability in potency of rT3 standards. The differences in rT3 values in the same sera (resulting from extrapolation from standard curves using different rT3 standards) were of the same magnitude as that noted in normal human sera in various studies, suggesting that the reported rT3 variations in sera of euthyroid individuals may also be due to differences in rT3 standards employed in the assay.

Antibody Specificity↗
PubMed1976

A simple and rapid thyroxine radioimmunoassy (T4-RIA) in unextracted human serum; a comparison of T4-RIA and T4 displacement assay, T4(D), in normal and pathologic sera.

A simple, rapid and accurate thyroxine radioimmunoassay (T4-RIA) in unextracted serum or plasma has been described, and for comparison T4 determinations have also been made by a T4(D) procedure using Abbott Tetrasorb kits. T4-RIA procedure basically involved denaturation of serum to dissociate T4-protein bond, and T4 released was allowed to react with [125I]T4-labeled T4 antiserum elicited by immunizing rabbits against bovine thyroglobulin. The displaced unbound [125I]T4 was rapidly taken up by an anionic resin sponge within 15 min and this sponge [125I]T4 uptake was linearly related to T4 present in standards or serum. The denaturation of serum effected by trichloroacetic acid-sodium hydroxide permitted virtually 100% T4 extraction recovery in normal, pregnancy, hypo- and hyperthyroid sera whereas 72.9-87.6% T4 recovery from normal serum (and with large individual differences) was noted with lower alcohols in T4(D) procedure. Cumbersome and/or tedious steps such as pre-extraction, centrifugation, time consuming bound and unbound hormone separation procedures, etc. are obviated in T4-RIA and the entire assay can be completed in the same tube in approximately an hour. These attributes along with increased sensitivity and specificity and the need for only microamounts of test sera (25-50 mul) in T4-RIA offer distinct advantages over T4(D) procedures, and in simplicity excel even other T4-RIAs. T4-RIA values in physiological and pathological states were highly correlated (r = 0.97) with T4(D) measurements and no differences between these two techniques were found. The reported discrepancies between T4-RIA and T4(D) measurements in human sera and some of the reasons for attributing these inconsistencies to probable methodological errors and variations are discussed.

Evaluation Studies as Topic↗
PubMed1976

Studies on obesity. III. effect of triiodothyronine (T3) on thyroglobulin autoantibodies in euthyroid obese subjects.

Effect of T3 therapy on tanned red cell agglutinating thyroglobulin (TRC-TG) antibodies in 10 obese subjects without apparent thyroid disease was investigated. Six other obese subjects without thyroid dysfunction and of approximately the same mean age who also had circulating TRC-TG antibodies served as control subjects and were untreated. In vitro thyroid tests (TSH, total and free T4) performed before T3 therapy, as well as clinical examination, showed thyroid function to be normal in all subjects, and there was no evidence of thyroiditis. TRC-TG antibodies were present in low to moderate titers of 40-1280 in control subjects as well as in subjects selected for T3 treatment. Therapy with T3 was started at 50 mug/day and gradually increased to a maximum of 250 mug/day, depending on clinical needs. T3-treated as well as untreated obese control subjects were all maintained on a high protein, low fat, low carbohydrate diet. Duration of T3 therapy varied from 2-8 mo, and in all but one T3-treated subject, TRC-TG antibodies completely disappeared. In the one exceptional case, TRC-TG antibody titer decreased from 1280 to 80 after 7 mo of therapy. In non-T3-treated obese control subjects, antibody titers remained at the same levels throughout the observation period, thereby indicating a lack of spontaneous regression of circulating immune response. Therapy with T3, by inhibiting TSH, may have caused regression of inapparent immunologic thyroid lesion, thus leading to the disappearance of circulating TRC antibodies; alternatively, T3 specifically may have accelerated catabolism of thyroid antibodies. The latter possibility is favored in the absence of clinical and laboratory evidence of thyroiditis in T3-treated subjects.

Adult↗
PubMed1976

Increased free thyroxine in a euthyroid patient with thyroxine-binding globulin deficiency.

An unusual finding of elevated free thyroxine (FT4) concentration coexistent with familial low thyroxine-binding globulin (TBG) is described in a euthyroid patient. Clinical and other laboratory tests were normal and consistent with a clinical diagnosis of euthyroidism. Low TBG (TBG capacity 3-10 mug/100 ml) was confirmed by various electrophoretic procedures and by TBG immunoassay (0.9 mg/100 ml). Serum T4 concentration was low (2.0-5.5 mug/100 ml). Triiodothyronine (T3) resin uptake was increased (88-93%) and the free thyroxine index was normal. Twenty-four-hour thyroidal 131I uptake was normal and varied between 13-20%. Serum thyroid-stimulating hormone (less than 2 muunits) and T3 concentration (80 ng/100 ml) were also normal. Long-acting thyroid stimulator (LATS) was not present. Free T4 concentration measured by dialysis procedure was markedly elevated (9.2-12.1 ng/100 ml). Pulse T3 and T4 tracer kinetic studies by the single compartmental method revealed accelerated blood disappearance of T4 (t 1/2 = 3.7 days) but normal disappearance of T3 (t 1/2 = 2.1 days). Extrathyroidal hormonal iodine pool (569 mug) was in the range of normals. T4 degradation rate (144 mug/70 kg/day) was moderately elevated over the euthyroid mean values, but was still close to or within the upper normal range. T3 degradation was normal (34 mug/day). Failure to develop hyperthyroidism in the presence of elevated free T4 levels, but with normal T3 concentration and dynamics, may suggest that T3, not T4, plays a major role in regulating metabolic activity; alternatively, euthyroidism in this low-TBG patient despite elevated free T4 concentration may simply be explained on the basis of a daily T4 disposal rate which was not clearly abnormal.

Humans↗
PubMed1976

A simple and rapid radioimmunoassay of triiodothyronine in unextracted serum.

A simple, accurate, and rapid procedure for radioimmunoassay (RIA) of triiodothyronine (T3) is described. Serum is denatured by sodium trichloroacetate and the T3 released is allowed to react with 125I-T3-labeled T3 anti-serum. The displaced 125I-T3 is rapidly taken up by an anionic-resin sponge, and this uptake is linearly related to serum T3 concentration. The entire assay procedure was completed in the same tube in about 1 hr. The T3 antibody was specific, and T4-to-T3 conversion in the assay did not occur. Recovery of exogenously added T3 was virtually complete. The mean T3 concentration in 92 euthyroid subjects (142 ng/100 ml) is comparable to the values described in a number of radioimmunoassays for T3.

Female↗