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Biomedical subjects

C Beckers

Publications and source records attributed to C Beckers.

At least 73 records · Page 4Linked to original sources
PubMed1985

Radionuclide absolute left ventricular volumes during upright exercise: validation in normal subjects by simultaneous hemodynamic measurements.

A nongeometric radionuclide technique for the determination of absolute left ventricular volumes was validated during exercise in nine normal subjects. Simultaneous reference stroke volume and cardiac output measurements were obtained by the Fick method. The reference left ventricular volumes were calculated by combining the Fick stroke volume and the isotopic ejection fraction. Data were collected at rest in the supine and upright positions and during 60 degrees upright exercise, at three levels of increasing severity. At rest, from supine to upright position, the reference end-diastolic volume decreased significantly from 182 +/- 24 ml to 154 +/- 21 ml (mean +/- SD, P less than 0.005); during upright exercise of low intensity, end-diastolic volume increased to 176 +/- 24 ml (P less than 0.05); at maximal exercise, end-diastolic volume was not different from the resting value in upright position. The end-systolic volume gradually decreased at rest from 67 +/- 11 ml in the supine position to 54 +/- 8 ml in the upright position (P less than 0.05). Compared with these reference data, the scintigraphic measurements were significantly lower on average by 23% for stroke volume, 21% for cardiac output, 22% for end-diastolic volume, and 23% for end-systolic volume. The overall changes in stroke volume (P less than 0.05) and end-systolic volume (P less than 0.001) occurring at rest and during exercise were correctly detected by the scintigraphic method but the smaller changes in end-diastolic volume (less than 15%) were not (P less than 0.15) because they were within the range of the precision of the technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Alternative diagnostic strategies for coronary artery disease in women: demonstration of the usefulness and efficiency of probability analysis.

Alternative strategies using conditional probability analysis for the diagnosis of coronary artery disease (CAD) were examined in 93 infarct-free women presenting with chest pain. Another group of 42 consecutive female patients was prospectively analyzed. For this latter group, the physician had access to the pretest and posttest probability of CAD before coronary angiography. These 135 women all underwent stress electrocardiographic, thallium scintigraphic, and coronary angiographic examination. The pretest and posttest probabilities of coronary disease were derived from a computerized Bayesian algorithm. Probability estimates were calculated by the four following hypothetical strategies: SO, in which history, including risk factors, was considered; S1, in which history and stress electrocardiographic results were considered; S2, in which history and stress electrocardiographic and stress thallium scintigraphic results were considered; and S3, in which history and stress electrocardiographic results were used, but in which stress scintigraphic results were considered only if the poststress probability of CAD was between 10% and 90%, i.e., if a sufficient level of diagnostic certainty could not be obtained with the electrocardiographic results alone. The strategies were compared with respect to accuracy with the coronary angiogram as the standard. For both groups of women, S2 and S3 were found to be the most accurate in predicting the presence or absence of coronary disease (p less than .05). However, it was found with use of S3 that more than one-third of the thallium scintigrams could have been avoided without loss of accuracy. It was also found that diagnostic catheterization performed to exclude CAD as a diagnosis could have been avoided in half of the patients without loss of accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Morphological and functional changes during thyroid hyperplasia and involution in C3H mice: effects of iodine and 3,5,3'-triiodothyronine during involution.

Involution of thyroid hyperplasia was induced in mice by discontinuing a goitrogenic treatment (low iodine diet plus 0.25% propylthiouracil for 10 days) and returning either to a moderate iodine diet (MID; 1 microgram I/day) alone or associated with T3 administration (1 microgram/day) or to a high iodine diet (HID; 10 micrograms I/day) alone or associated with T3 treatment. Thyroid involution was studied by morphological, stereological, and biochemical methods after 2, 4, 6, and 8 days of involution. Age-paired, HID-fed animals were used as controls. When the involution was induced by MID, the glands resumed a normal morphological aspect. The synthesis and secretion of T3 were highly stimulated on day 2, but decreased thereafter. Plasma T4 levels reached a plateau at 50% of the control value from days 2-8. The administration of T3 together with MID accelerated the involution of hyperplasia and colloid accumulation in the follicular lumina. The synthesis and secretion of T3 and T4 remained lower than those in controls. When the involution was induced by HID, the thyroid weight remained higher than that in controls or in any involuting groups. The number of follicles and epithelial cells as well as the glandular thyroglobulin content were twice the control values. A Wolff-Chaikoff effect was evident on day 4, and hypothyroidism persisted. When HID was supplemented with T3 treatment, glandular weight and morphology were normal, but the Wolff-Chaikoff effect occurred earlier. In conclusion, the iodine dose given after a goitrogenic treatment must be carefully controlled; a high but physiological dose can have deleterious effects, whereas a small dose is beneficial. T3 prevents the deleterious effects of HID, but the thyroid enters a resting state.

Animals↗
PubMed1985

Validation of radionuclide cardiac output measurements during exercise.

A nongeometric radionuclide technique with correction for attenuation was used for the determination of cardiac output and stroke volume during exercise in nine normal subjects and in ten hypertensive patients. Simultaneous reference stroke volume (range 48-159 ml) and cardiac output (range 3.6-23.8 l/min) measurements were obtained by the Fick method. Data were collected at rest and during 60 degrees upright exercise, at two or three levels of increasing severity. Three statistical measurements were used for the comparison of both methods: correlation, precision, and accuracy. Radionuclide and Fick cardiac output measurements (n = 67, rest and exercise data) correlated well (r = 0.90). For stroke volume, the correlation was less (r = 0.64); however, the precision or random variability of both methods was similar for stroke volume (radionuclide: 8 ml or 9%; Fick: 16 ml or 16%). The accuracy or systematic error was defined as the mean difference between radionuclide and Fick measurements. The radionuclide method underestimated the Fick measurements. The systematic error was 18 +/- 18 ml for stroke volume and 2.4 +/- 2.4 l/m for cardiac output. A similar comparison of both methods was made on the absolute changes of stroke volume (r = 0.61; range -19 + 70 ml) and cardiac output (r = 0.82; range +1.6 + 16.4 l/m) between rest and exercise. The precision of the two methods was similar; the systematic error was 1.9 +/- 2.2 l/m for cardiac output and 6 +/- 17 ml for stroke volume. Thus, in these two groups of patients, although radionuclide and Fick cardiac output measurements at rest and during exercise correlated well, the radionuclide values were systematically and significantly lower.

Adult↗
PubMed1984

Familial dysalbuminemic hyperthyroxinemia (FDH): inadequacy of the "analog" methods for assaying free-T4 levels.

Free-T4 levels were determined in familial dysalbuminemic hyperthyroxinemia (FDH) subjects. In agreement with their euthyroid status free-T4 levels were within the normal range when tested by equilibrium dialysis and by the FT4 Immophase method (Corning Medical). However, when using the recently introduced "analog" methods, either Amerlex FT4 or Becton-Dickinson FT4, Free-T4 values were markedly higher than the control values. This discrepancy is probably due to artifactual binding of the labeled analog to the fraction of albumin exhibiting an excessive affinity for T4.

Humans↗
PubMed1984

Serum thyroglobulin levels in preterm neonates.

Serum thyroglobulin (Tg) levels were determined in preterm neonates. Very high values were found at birth. A significant negative correlation was observed between Tg levels and gestational age. A longitudinal study indicates that a very sharp decrease in Tg levels occurred after birth. Three weeks after birth, the values were close to the values of full-term neonates. These high hTg values could result either from an increased turnover of hTg or from a lower clearance rate of this iodoprotein.

Gestational Age↗
PubMed1984

The thyroid-system function in preterm infants of postmenstrual ages of 31 weeks or less: evidence for a "transient lazy thyroid system".

A prospective study was conducted in order to evaluate thyroid function in 20 healthy and 18 sick preterm infants with postmenstrual ages of 31 weeks or less. The clinical condition of both groups was compared using a "Neonatal Special Care Evolution Score". The effect of thyroid hormone treatment, given from D10 on to the sick infants, was also studied. TSH, thyroid hormone levels (TG, T4, T3, rT3, FT4 and FT3) and TBG were measured by radioimmunoassays at D0, D10, D20, D30 and D40. Healthy preterm infants on D0 have a median TSH level of 22 microU/ml and a high TG level of 200 ng/ml; thereafter, median serum levels decrease to 6 microU/ml and 35 ng/ml respectively. During the same period, median serum T4 is maintained at a low level of about 6-8 micrograms/dl, median serum T3 gradually increases from 80 ng/dl on D0 to 150 ng/dl on D40, and median serum rT3 decreases beyond D10 from a plateau of 200 ng/dl to about 100 ng/dl. In the sick preterm infants before treatment, serum TSH is as in the control group but serum T4, T3 and rT3 on D10 are well below the control values (P = 0.005). In all conditions, there is a significant correlation between serum T4 and FT4, and between serum T3 and FT3. Thyroxine, given to the sick preterm infants from D10 on, brings median serum T4 values closely to the ones of the control group whereas serum levels of TSH and TG are unaffected and similar to those of the healthy preterm infants. Furthermore, thyroxine brings serum rT3 within the range of the control group but leaves median serum T3 at a low level of about 50 ng/dl. On T3 treatment, serum T3 normalizes but rT3 and particularly T4 tend to decline further. In the conditions of this study a significant difference in TBG level is not proven. Although an untreated sick group was not enrolled in the study, thyroid hormone treatment brought the "Neonatal Special Care Evolution Score" of the treated sick infants closer to that of the healthy preterm infants. In the sick preterm infant with failure to thrive on D10, there is an impaired thyroid discharge of T4 in spite of serum TSH values not different from those of the control group.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1982

Breath 14CO2 after intravenous administration of [14C]aminopyrine in liver diseases.

The determination of of 14CO2 in breath after oral administration of [14C]aminopyrine has been proposed as a quantitative liver function test. In order to shorten the procedure and avoid misinterpretations related to variable rates of intestinal absorption, the [14C]aminopyrine breath test (ABT) was performed after intravenous administration of [14C]aminopyrine in 21 controls and 89 patients with biopsy-proven liver disease. The specific activity of the first hour sample corrected for body weight (SA1) was the most discriminant expression of breath data. The SA1 value, expressed as the percentage of the administered dose, was 0.86 +/- 0.1% (mean +/- SD) in controls and significantly less in patients (0.46 +/- 0.31%). Low values were observed in patients with untreated chronic active hepatitis (0.16 +/- 0.13%), alcoholic cirrhosis (0.2 +/ 0.15%0, and untreated postnecrotic cirrhosis (0.47 +/- 0.17%). In contrast, normal values were obtained in chronic persistent hepatitis (0.86 +/- 0.13%) and 58% of noncirrhotic alcoholic liver diseases (0.83 +/- 0.27%). The results of duplicate studies were reproducible and SA1 correlated with other conventional liver function tests, including 45-min BSP retention. Among these, ABT was the most sensitive screening test for the presence of cirrhosis, especially in alcoholic patients, where it allowed a sharp distinction between cirrhotic and noncirrhotic cases. The results obtained in chronic hepatitis suggested that ABT may provide a reliable index of the activity of the disease. In our hands, intravenous ABT, performed over a 1-hr period, was a fast, sensitive, and discriminant liver function test.

Administration, Oral↗
PubMed1982

Assessment of the sites of red cell destruction using quantitative measurements of splenic and hepatic red cell destruction.

Red cell survival, surface counting indices, the splenic and hepatic contribution to red cell destruction and the rate of splenic and hepatic red cell destruction were measured in 29 patients. Splenectomy was performed in 14. No correlation could be found between the splenic excess count index and both the amount and rate of red cell destruction in the spleen, but the rate of splenic and hepatic red cell destruction was related to the rate of disappearance of red cells from the circulation. The mean fractions of red cell destruction in spleen and liver were 46.1% +/- 20.5 (SD) and 11.7% +/- 4.2 (SD) respectively. After splenectomy, the haematocrit returned to normal in all patients despite fractions of red cell destruction in the spleen not exceeding 60%. Although the measurements of the splenic red cell destruction rate and of the fraction of red cell destruction in the spleen provide more precise information on the role of the spleen in red cell destruction, their prognostic value in patients who underwent splenectomy was not obvious.

Adult↗
PubMed1982

Assessment of bone marrow and splenic erythropoiesis in myelofibrosis.

The iron uptake in bone marrow and spleen was measured in 29 patients with myelofibrosis using 52Fe and quantitative scanning. In 10 patients, no iron uptake in the marrow could be observed and active erythropoiesis was extramedullary only. In the bone marrow of patients with myelofibrosis, the iron uptake per nucleated red cell was less than that observed in conditions without myelofibrosis or extramedullary erythropoiesis. Increasing splenic iron uptake was likely to be associated with a decreasing bone marrow iron uptake and was related to the size of the spleen. The data suggest that in myelofibrosis, the spleen dominates iron uptake through intense erythropoiesis and a high splenic blood flow, thus restraining iron supply to the bone marrow.

Adult↗
PubMed1981

The effects of mild iodine deficiency on neonatal thyroid function.

In order to assess neonatal thyroid function in the endemic goitre areas of Greece, T4 and TSH have been measured. Previous studies had shown that in these endemic areas, adults had low T4 but normal TSH values, probably because of an increase in the serum T3 level. In this study, T4 and TSH were measured in dried blood spots from 259 neonates. The fifty-four full-term neonates from the Greek endemic villages had a lower T4 value (8.8 +/- 0.66 micrograms/dl SE) but a higher TSH (15.37 +/- 1.12 mu/l) than the seventy-three full-term neonates from the non-endemic villages (T4:10.0 +/- 0.33 micrograms/dl, TSH:11.93 +/- 0.59 mu/l) or the ninety-eight from Athens (T4:10.0 +/- 0.33 micrograms/dl, TSH:10.96 +/- 0.64 mu/l). Premature neonates, both from Athens and from the endemic areas, have significantly lower T4 and significantly lower TSH values than the full-term ones from the same areas, probably because of the immaturity of the pituitary-thyroidal axis. It is concluded from these observations that (a) Neonates suffer more from the consequences of iodine deficiency than adults. The biochemical hypothyroidism reported here may be relevant to the delayed skeletal maturation previously reported from children of these same areas. This emphasizes the need for correcting even moderate iodine deficiency. (b) The occurrence of non-toxic goitre with normal TSH levels in adults is best explained by assuming that increased TSH stimulation is necessary for goitre formation during neonatal life, but not for goitre maintainance during adulthood. (c) Newborn screening programmes in these areas should take into account the present findings.

Female↗
PubMed1980

Morphological changes in mice thyroid induced by iodine deficiency.

Goitrogenesis induced in mice by iodine deficiency took place in two distinct phases. The first phase lasted four weeks and was characterized histologically by the classic signs of hyperplasia: colloid resorption, increase in the height of the epithelium and enlargment of the capillaries. After the fourth week, the morphological changes in the thyroid were different in males and females. In the male, pluristratified follicles, secondary follicular cavities and papillary projections were observed. In the female, most of the follicles retained their hyperplastic appearance, while papillary projections were observed in very few follicles.

Animals↗
PubMed1980

The uptake and release of ponasterone A by the Kc cell line of Drosophila melanogaster.

The association of ponasterone A (PNA) and 20-hydroxyecdysone with Kc cells is commensurate with their biological activity on this Kc cell line, the physiological activity ratio for PNA, 20-hydroxyecdysone and ecdysone is 1 : 50 : 2000, resp. Both association and release of [3H]-PNA are temperature-dependent, the activation energy was calculated as 16.7 cal (Arrhenius analysis). This association is compatible with unlabelled PNA and various ecdysteroids. The KD for PNA (Scatchard analysis) was estimated as 3.6 x 10(-9) M, giving the number of binding sites as approx. 1800 per cell.

Cell Division↗
PubMed1980

Measurement of erythropoiesis using 52Fe.

A method for determining erythropoiesis quantitatively with 52Fe has been applied to 25 patients with anaemia. The data were derived from quantitative scanning of the erythropoietic areas and the measurement of the plasma iron turnover. We have assessed this 52Fe measurement of erythropoiesis by comparing it with total marrow iron turnover studies. Both methods give similar estimates of erythropoiesis except in patients with severe ineffective erythropoiesis and in a patient with significant peripheral haemolysis, when erythropoiesis as measured with the 52Fe technique gave higher results. In these conditions, the estimate of total erythropoiesis might be more reliable using the 52Fe quantitative scanning technique. However, the measurement of erythropoiesis with 52Fe does not distinguish effective from ineffective erythropoiesis and cannot be applied to patients with extramedullary erythropoiesis.

Bone Marrow↗
PubMed1980

The influence of thyrotropin and growth hormone on the thyroid gland in the hereditary dwarf mouse: a morphometric study.

Snell-type dwarf mice were injected with TSH, GH, or both hormones together for 6 days. GH induced an increase in body weight but not in the weight of the thyroid gland itself; on the contrary, TSH caused an increase in the weight of the thyroid but no increase in body weight. After TSH injection, the relative volume of the thyroid parenchyme was enhanced by 45% compared to that in untreated dwarf mice, and the radius of the follicles and follicular lumina increased by 50% and 48%, respectively. The major effect of TSH was an increase in cellular volume (+93%), and the mean number of cells in the average follicle was doubled, without a reduction in the number of follicles. GH had almost the same effect as TSH on the relative volume of the parenchyme and caused the radius of follicles and of the follicular lumina to increase by 61% and 69%, respectively. However, GH did not influence cellular volume. Its primary effect was to stimulate cellular division (cells were increased about 5 times in the average follicle) and to reduce the number of follicles. The nucleo-cytoplasmic ratio increased with GH but decreased with TSH. T4 serum levels increased to a much lesser extent with GH than with TSH, while normal values were obtained with both hormones together. At a morphological level, the combined administration of TSH and GH produced the same qualitative effects as separate administration, inducing an increase in cell volume and number which was less than the sum of the effects of each hormone administered separately.

Animals↗