Diurnal rhythms of thyroid hormones in rooster chicks (Gallus domesticus). 1. Studies on the colloid epithelium portion, the radioiodine accumulation in the thyroid gland and the plasma radioiodide concentration]

Four and five week old White Leghorn cockerels were investigated concerning diurnal changes of thyroidal activity. They were kept under normal conditions, including the changes in day light (light from 5.00 am to 8.00 pm). In the thyroid maxima of the per cent amount of colloid were found at 3.00 am and at noon. The values differed significantly from the intermediate ones (2P less than 0.001) which reached only 22 per cent of the maxima. The thyroidal uptake of radioiodine had also a maximum at 3.00 am (51 percent and 78 percent resp., 90 min. or 24 hours p.i.). The 24-h uptake at 3.00 am was significant different from the corresponding uptakes between 6.00 am and 6.00 pm (53-61 percent; 2P less than 0.05). The plasma radioiodide increased at afternoon and in the evening. The 9.00 pm concentration differed significantly from the 9.00 am concentration (2P less than 0.001). Since in the afternoon most of the food is ingested the thyroid can take up a greater amount of untracered iodide and therefore the radioiodide concentration of plasma may remain high. The above observations may be explained in the following way: (1) The thyroidal iodine uptake is increased in the afternoon corresponding to the increase in colloid; however these increase is not detectable by measuring the radioiodine uptake because of dilution effects (during the night the increase in colloid coincidences with the increase in iodine uptake); (2) looking at the daily changes of colloid and radioiodine uptake the thyroid may be stimulated in the early morning and in the evening.     

Diurnal rhythms of thyroid hormones in rooster chicks (Gallus domesticus). 3. Studies on the changes in deiodination rate of thyroxine-I-131]

As a measure for the availability and efficiency of the so-called free hormone to repress the thyreotropin-secretion (Mouriz et al., Endocr. 79, 248-260 (1966) we investigated the deiodination of thyroxine-I-131 (T4-I-131). This was done with special regard to a possible cyclic variation. By means of the reutilisation we could measure the removed radio-iodide in the thyroid 1-1/2 hours after T4-I-131 application. Using I-125 as a reference-isotope for the radioiodine uptake we could specify the actual extent of deiodination. The deiodination had a diurnal variation: The minimal values at 9 am and 9 pm ("deiodination" 10 or 9 percent) were significantly different (2 P less than 0.025) from the maximal values at 3.00 am and 3.00 pm ("deiodination-rate" about 17 percent). We propose the following explanation: 1) While the deiodination is decreasing in the morning and evening the pituitary releases more thyreotropin; 2) Thereby the thyroid releases more hormone and so the protein-bound iodine and the so-called free hormone raises. This would be in good agreement with our prior investigations.     

pH effects in the spontaneous reactivation of phosphinylated acetylcholinesterase

Previous studies on the spontaneous reactivation of phosphorylated and phosphonylated cholinesterases report bell-shaped curves with reaction rate maxima between pH values of 7 and 9. By way of contrast, we found reactivation rate minima in the same pH region for a phosphinylated bovine erythrocyte acetylcholinesterase and three phosphinylated eel acetylcholinesterases. To further elucidate these observations, eel acetylcholinesterase was inhibited with racemic 4-nitrophenyl ethyl(phenyl)phosphinate. The spontaneous reactivation of the inhibited enzyme over the pH range 6.00 to 9.00 was monitored following 1. both inhibition and spontaneous reactivation at the same pH, and 2. inhibition at pH 7.60 followed by spontaneous reactivation at the selected pH. The combined plots of both studies gave overlapping pH curves with minima around pH 7.60. The results indicate that the minima in the rates of the spontaneous reactivation of phosphinylated acetylcholinesterases are not the consequence of a pH-controlled change in the relative inhibition rates of the P(+)- and P(-)-enantiomers participating in the inhibition reaction. Our results suggest that the orientation of the phosphinyl group in the active site of phosphinylated acetylcholinesterase is quite different from that of the inhibitor groups in phosphonylated or phosphorylated enzyme.     

Evidence for a secretion of thyroxine by isolated hog thyroid cells.

Isolated thyroid cells prepared from hog thyroid glands by tryptic dispersion were incubated with 131I- for 1--6 h. Free [131I]thyroxine was identified in the incubation medium by three chromatographic methods. Neither [131I]iodotyrosines nor [131I]triiodothyronine were detected. The [131I]thyroxine released in the medium by 100 mul of cells (packed cell volume) after a 6-h incubation period amounted to 1.16% (S.E. = +/- 0.39) of the total radioactivity. The medium [131I]thyroxine represented 15--25% of the total [131I]thyroxine synthesized during the 6 h of incubation. Thyrotropin, 1--60 munits/ml, increased the medium [131I]thyroxine content 2-4 fold. Dibutyryl cyclic AMP mimicked the effect of thyrotropin. The amount of medium [131]thyroxine was strictly related to the amount of incubated cells but was independent of the volume of the incubation medium. When prelabeled cells were incubated in the presence of methimazole the increase in medium [131I]thyroxine was quantitatively related to a decrease in the intracellular [131I]thyroxine. Addition of dinitrotyrosine, an inhibitor of the deiodinase activity, induced the release of iodotyrosines in the incubation medium. That the incubation supernatant of isolated thyroid cells did contain free thyroxine but not iodotyrosines suggests that the normal mechanisms of proteolysis of thyroglobulin and deiodination of iodotyrosines inside the cells are preserved. From these data, it was concluded that the thyroxine release by isolated cells represents a real secretion.     

Extensive scleral perforation with complete recovery

Sixty patients with abnormally high I(131) uptake were treated with liothyronine (L-triiodothyronine) for seven or eight days and then tested again. Fifty-five patients showed a suppression of iodine uptake sufficient to eliminate the possibility of hyperthyroidism. Also the therapeutic trial of liothyronine indicated whether they were euthyroid, or hypothyroid with iodine deficiency. Six of the patients showed insignificant change in the I(131) uptake after treatment with thyroid hormone-that is, the change from the original uptake was less than 30 per cent. These six patients were later confirmed to be hyperthyroid. In four patients the uptake at the second test was less by between 35 and 52 per cent than at the first. These four patients, like the remainder with even greater suppression in thyroid uptake, remained clinically euthyroid.The repeat I(131) uptake test was thus seen to be considerably more accurate than the single test and well worth the time required to perform it.     

Secretion of Radioiodine in Milk Following a Single Oral Administration in the Cow

The secretion of radioiodine in the milk following the administration of a single oral dose was studied using I131. All of the values are corrected for the physical decay of the isotope. I131 began to appear in the milk 30 minutes after administration with a maximal concentration of, on the average, 1.7 per cent of the given dose per 1 of milk at about six hours following administration. The subsequent reduction in the concentration showed a two exponential course with biological half-lives of 0.6 days and 10 days, respectively. The total secretion in the milk was between 10 and 27 per cent of the given dose of I131 in six days. The total secretion of radioiodine in the milk was seen to be dependent upon the cow’s milk production.     

The Purity of Radioiodide-I131 Assessed by in Vivo and in Vitro Methods

Between 41 and 94% of the radioactivity of 24 preparations of I¹³¹ supplied without cysteine preservative was non-iodide on chromatographic analysis. Extraneous radio-activity was essentially absent from I¹³¹ supplied with cysteine. It was converted to iodide-I¹³¹ by 10^-3 M cysteine or iodide but not by incubation at pH 2. The average thyroid uptake of I¹³¹ containing extraneous radioactivity was significantly lower than the uptake of I¹³¹ free from non-iodide impurity in 16 human subjects measured under controlled conditions and in a random group of 669 patients. Incubation of samples of I¹³¹ containing non-iodide radioactivity with tyrosine and cupric chloride resulted in the non-enzymatic formation of monoiodotyrosine-I¹³¹ either in the presence or absence of thyroid homogenate. Enzymatic formation of monoiodotyrosine-I¹³¹ by thyroid homogenates could be demonstrated only when I¹³¹ free from extraneous activity was used.     

Evidence for a secretion of thyroxine by isolated hog thyroid cells

Isolated thyroid cells prepared from hog thyroid glands by tryptic dispersion were incubated with ¹³¹I⁻ for 1–6 h. Free [¹³¹I]thyroxine was identified in the incubation medium by three chromatographic methods. Neither [¹³¹I]iodotyurosines nor [¹³¹I]triiodothyronine were detected. The [¹³¹I]thyroxine released in the medium by 100 μl of cells (packed cell volume) after a 6-h incubation period amounted to 1.16% (S.E. = ± 0.39) of the total radioactivity. The medium [¹³¹I]thyroxine represented 15–25% of the total [¹³¹I]thyroxine synthesized during the 6 h of incubation. Thyrotropin, 1–60 munits/ml, increased the medium [¹³¹I]thyroxine content 2–4 fold. Dibutyryl cyclic AMP mimicked the effect of thyrotropin. The amount of medium [¹³¹I]thyroxine was strictly related to the amount of incubated cells but was independent of the volume of the incubation medium. When prelabeled cells were incubated in the presence of methimazole the increase in medium [¹³¹I]thyroxine was quantitatively related to a decrease in the intracellular [¹³¹I]thyroxine. Addition of dinitrotyrosine, an inhibitor of the deiodinase activity, induced the release of iodotyrosines in the incubation medium. That the incubation supernatant of isolated thyroid cells did contain free thyroxine but no iodotyrosines suggests that the normal mechanisms of proteolysis of thyroglobulin and deiodination of iodotyrosines inside the cells are preserved. From these data, it was concluded that the thyroxine release by isolated cells represents a real secretion.     

Goitres in rats fed polychlorinated biphenyls.

Rats fed a polychlorinated biphenyl (PCB) mixture in a high- or low-iodine diet (HID or LID respectively) for 15 days had thyroid enlargement, low serum thyroxine (T4), and high serum thyrotropin concentrations. Although binding of thyroid hormones to serum proteins was reduced in PCB-fed animals, the free T4 index (reflecting free T4 in serum) was less in these rats. Both serum triiodothyronine (T3) and the free T3 index were elevated in rats fed PCB in HID. LID-maintained rats elevated serum T3 concentrations but the free T3 index was similar to that in HID-fed rats, owing to enhanced binding of thyroid hormone to serum proteins. Addition of PCB to LID reduced serum T3 levels but did not alter the free T3 index because binding was less. In rats fed HID containing PCB, thyroid 131I uptake was increased.     

Severe euthyroid cardiac disease; technique for treatment with radioiodine

It is possible to safely lower the basal metabolism of patients suffering from severe cardiac disease by administering multiple small doses of radioiodine in order to achieve symptomatic relief. From the present study, multiple small doses of I(131) appeared to be as effective as single or multiple large doses of this material and complications such as thyroiditis, temporary thyrotoxicosis and bone marrow depression were almost always avoided. No damage to the parathyroid glands or the recurrent laryngeal nerve was observed. No radiation sickness developed after therapy.A scintigram of the thyroid gland was useful in determining the size, shape and function of the thyroid gland before and during radioiodine treatment and helped to determine the need for additional treatment. In order to prevent the distressing symptoms of the myxedema state, desiccated thyroid was administered when necessary. In the series of 278 euthyroid patients with severe cardiac disease who were treated with radioactive iodine, results were excellent in 35 per cent of cases and good in 44 per cent. In 21 per cent there was no improvement.     

Regulation of RNA synthesis in the rat heart in L-thyroxine toxicosis and hypothyroidism; the role of RNA-polymerases and the template activity of chromatin

It is shown that L-thyroxin applied to rats has induced in them development of pronounced cardiac hypertrophy accompanied by an increase in the total amount of nucleic acids in the myocardium (per organ) and enhancement of the RNA synthesis rate. It is confirmed by a considerable rise of the intensity of the labelled uridine incorporation into RNA without alteration of the specific radioactivity in a pool of free nucleotides and by the growth of the RNA-polymerase I activity. When L-thyroxin toxicosis lasts for four weeks and heart weight has not already increased the content of nucleic acids remains high, the rate of the label incorporation into RNA lowering down to the normal level. The activity of RNA-polymerase I is almost twice as low as that under thyrotoxicosis lasting for a week. In this case the matrix activity of chromatin tested by exogenous RNA-polymerase III of the rat gets lower. Under mercasolyl-induced hypothyrosis the heart weight decreases as well as the amount of nucleic acids, RNA synthesis intensity (by 40%) and RNA-polymerase I activity in it. The data obtained testify to the versatile effect of the thyroid hormones on RNA biosynthesis in the cardiac muscle and on the activity of both the RNA-polymerases and chromatin matrix.     

131I对男性甲状腺功能亢进症血清性激素及甲状腺球蛋白水平影响研究

目的:探讨~(131)I对男性甲状腺功能亢进症患者血清性激素及甲状腺球蛋白水平的影响。方法:收集我院收治的男性甲状腺功能亢进症患者74例,随机分为对照组和实验组,每组各37例,对照组患者给予他巴唑口服,20-30 mg/次,每日口服1次。实验组患者在对照组基础上给予~(131)I治疗。治疗结束后,检测并比较两组患者血清游离三碘甲状腺素(FT3)、游离甲状腺素(FT4)、促甲状腺激素(TSH)、睾酮(T)、雌二醇(E2)、甲状腺球蛋白(TG)水平的变化以及临床疗效。结果:与治疗前相比,两组患者血清FT3、FT4、T、E2、TG水平均显著下降,TSH水平明显升高(P0.05);与对照组相比,实验组患者血清FT3、FT4、T、E2、TG水平较低,TSH水平以及临床治疗有效率较高(P0.05)。结论:~(131)I能够显著降低男性甲状腺功能亢进症血清FT3、FT4、T、E2、TG水平,升高TSH水平,临床效果较好。     

Iodinated phospholipids and the iodination of proteins of dog thyroid gland in vitro

Slices of dog thyroid gland were incubated with liposomes consisting of (125)I-labelled phosphatidylcholine (the iodine was covalently linked to unsaturated fatty acyl chains). The (125)I label of (125)I-labelled liposomes was incorporated into thyroid protein and/or thyroglobulin at a higher rate than was the (131)I label of either Na(131)I or (131)I(2). The iodine was shown to be protein-bound by the co-migration of the labelled iodine with protein under conditions where free iodine, iodide and lipid-bound iodine were removed from protein. The uptake of iodine from the iodinated phospholipid was probably due to phospholipid exchange between the iodinated liposomes and the thyroid cell membrane, since (a) (14)C-labelled phospholipid was metabolized to (14)CO(2) and (b) many lipids in the tissue slice became (14)C-labelled. A very strong inhibition of iodide ;uptake' from Na(131)I, caused by thiosulphate, produced only a minor inhibition of the incorporation of (125)I from (125)I-labelled liposomes into thyroid protein and/or thyroglobulin. This implies that free iodide may not necessarily be formed from the iodinated phospholipids before their entrance or utilization in the cell. Synthetic polytyrosine polypeptide suspensions showed some iodination by (131)I-labelled liposomes. In tissues with low tyrosine contents, such as liver and kidney, only a trace uptake was observed. Salivary gland showed some uptake. Endoplasmic reticulum of thyroid gland showed a higher iodine uptake than that of the corresponding plasma membranes. These experiments, together with the demonstration of the diet-dependent presence of iodinated phospholipids in dog thyroid, leads us to suggest that iodination of the membrane phospholipids of thyroid cells may be directly or indirectly involved at some stage in the synthesis of thyroglobulin, or exists as a scavenger mechanism, to re-utilize and/or recover released iodine from unstable compounds inside the thyroid cell.     

Intrathyroidal iodine metabolism in the rat. The influence of diet and the administration of thyroid-stimulating hormone

1. Ratios of mono[¹³¹I]iodotyrosine and di[¹³¹I]iodotyrosine (R values) and the incorporation of ¹³¹I into iodothyronines have been estimated in rat thyroid glands from 30min. to 38hr. after the administration of [¹³¹I]iodide. 2. In rats receiving a powdered low-iodine diet the R values were close to unity and did not change with time after the administration of [¹³¹I]iodide. In rats receiving a commercial pellet diet the R values fell from a mean of 0·8 at 30min. after [¹³¹I]iodide administration to 0·49 at 38hr. 3. Administration of 0·5–2·0i.u. of thyroid-stimulating hormone before giving the injection of [¹³¹I]iodide caused a small diminution in the R value when the time between injecting [¹³¹I]iodide and killing the animal was 16hr. or more. 4. Iodothyronines represented a greater percentage of the total thyroid-gland radioactivity in the iodine-deficient animals than in animals fed on the pellet diet. Thyroid-stimulating hormone had little effect, if any, on the iodothyronine contents.     

Absorption of Foliar-Applied 32P by Successive Leaves, and Distribution Patterns in Relation to Early Fruiting and Abscission in the Cowpea (Vigna unguiculata L.)

In controlled environment experiments, the uptake and distributionpatterns of ³²P were studied in relation to flowering and fruitingin the cowpea. Absorption by the plant, retention by the fedleaf, and translocation to various plant parts depended on theposition and age of the fed leaf. At the 4-leaf stage, whenthe terminal leaflet of the first trifoliate (oldest) was fed³²P, the plant absorbed 43 per cent of total radioactivity suppliedin 24 h. The percentages resulting from the feeding of trifoliates2, 3, and 4 (youngest) were 58, 71, and 73 respectively. Trifoliate1 retained 34 per cent of the total radioactivity, while trifoliate4 retained 68 per cent. Of the plant tissues, the root accumulatedthe greatest amounts of the P exported by the fed leaflet, withthe feeding of trifoliates 1, 2, or 3. With the feeding of trifoliate4, however, the root imported only 0.2 per cent of total radioactivity. When the plants had one set of flowers fully open at raceme1, the flowers imported 0.19 per cent of total radioactivityin the cultivar Adzuki, and 0.36 per cent in the cultivar EarlyRamshorn. When the raceme 1 flowers developed into fruits whilethe raceme 2 flowers were fully open, the raceme 1 fruit importof radioactivity was 2.61 per cent in Adzuki and 14.21 per centin Early Ramshorn. Raceme 1 fruits of Early Ramshorn thus accumulatedfive times as much P radioactivity as those of Adzuki. Whenracemes 1 and 2 both bore fruits, removal of the raceme 1 fruitsjust prior to ³²P feeding, led to the import by the raceme 2fruits of 0.25 per cent in Adzuki and 0.09 per cent in EarlyRamshorn. The raceme 1 fruits constituted a more potent sinkfor ³²P in Early Ramshorn than in Adzuki. The results are discussedin relation to the known patterns of premature abscission offlowers and young fruits in the two cultivars.     

HYPERTHYROIDISM—Diagnosis by Failure of Triiodothyronine to Suppress Uptake of Iodine131

Sixty patients with abnormally high I¹³¹ uptake were treated with liothyronine (L-triiodothyronine) for seven or eight days and then tested again. Fifty-five patients showed a suppression of iodine uptake sufficient to eliminate the possibility of hyperthyroidism. Also the therapeutic trial of liothyronine indicated whether they were euthyroid, or hypothyroid with iodine deficiency. Six of the patients showed insignificant change in the I¹³¹ uptake after treatment with thyroid hormone—that is, the change from the original uptake was less than 30 per cent. These six patients were later confirmed to be hyperthyroid. In four patients the uptake at the second test was less by between 35 and 52 per cent than at the first. These four patients, like the remainder with even greater suppression in thyroid uptake, remained clinically euthyroid.The repeat I¹³¹ uptake test was thus seen to be considerably more accurate than the single test and well worth the time required to perform it.     

Post-Chernobyl thyroid cancers in Ukraine. Report 2: risk analysis

On April 26, 1986, the worst nuclear reactor accident to date occurred at the Chornobyl (Chernobyl) power plant in Ukraine. Millions of people in Ukraine, Belarus and Russia were exposed to radioactive nuclides, especially (131)I. Since then, research has been conducted on various subgroups of the exposed population, and it has been demonstrated that the large increase in thyroid cancer is related to the (131)I exposure. However, because of study limitations, quantified risk estimates are limited, and there remains a need for additional information. We conducted an ecological study to investigate the relationship between (131)I thyroid dose and the diagnosis of thyroid cancer in three highly contaminated oblasts in Northern Ukraine. The study population is comprised of 301,907 persons who were between the ages of 1 and 18 at the time of the Chornobyl accident and were living in 1,293 rural settlements in the three study oblasts. Twenty-four percent of the study population had individual thyroid dose estimates and the other 76% had "individualized" estimates of thyroid dose based on direct thyroid measurements taken from a person of the same age and gender living in the same or nearby settlement. Cases include 232 thyroid cancers diagnosed from January 1990 through December 2001, and all were confirmed histologically. Dose-response analyses took into account differences in the rate of ultrasound examinations conducted in the three study oblasts. The estimated excess relative risk per gray was 8.0 (95% CI = 4.6-15) and the excess absolute risk per 10,000 person-year gray was estimated to be 1.5 (95% CI = 1.2-1.9). In broad terms, these estimates are compatible with results of other studies from the contaminated areas, as well as studies of external radiation exposure.     

Early ultrastructural injuries in the thyroid of the normal rat radioinduced by diagnostic and/or therapeutic amounts of iodine-131.

After irradiation, two principal mechanisms of cytolytic cell death can be involved: apoptosis and necrosis. By using morphological criteria, cells undergoing apoptosis can be distinguished from cells dying by necrosis. In nuclear medicine 131I is used to ablate thyroid remnants or to treat well differentiated thyroid carcinoma. The aim of study was to describe the progressive morphological thyroid changes induced by a diagnostic and/or therapeutic amounts of 131I in the rat using electron microscopy, in an attempt to determine which is the cell death pathway and to analyse "stunned" thyroid tissue to elucidate this effect. Tissular and ultrastructural examinations show that damages induced by 131I irradiation of the normal thyroid gland are heterogeneous. Thyroid cells die by necrosis after this metabolic irradiation, and no signs of apoptosis were observed by electron microscopy. In the other hand, stunning effect did not seem to impair the effectiveness of 131I treatment.     

The value of plasma TSH estimation and TRH stimulation test in the course of treatment of differentiated thyroid cancers.

Plasma TSH levels were measured on 114 occasions in 96 patients treated for differentiated thyroid cancer. Prior to thyroid surgery, plasma TSH levels were within the range of normal. Plasma TSH levels increased slightly following partial thyroid resection and definitely after total thyroid ablation. In patients where the removal of normal thyroid induced hormonogenesis in thyroid tumours, plasma TSH levels were dependent on the hormonal secretion of the tumour as shown by inverse relationship between TSH and both PBI and 131I uptake. The increase of radioiodide uptake following stimulation by exogenous bovine TSH was inversely related to the plasma thyrotropin levels. The suppressibility of enhanced thyrotropin levels was complete with individually adjusted doses of synthetic thyroid hormones. With the exception of patients on suppressive treatment, TRH administration induced increase in plasma TSH levels. The findings are discussed with regard to the role played by TSH in the induction of hormonogenesis in thyroid tumours. The practical values of TSH estimation and TRH stimulation seem to be low; the measurements of thyrotropin levels may be important for the estimation of the suppressive effect in the course of and following withdrawal of treatment with thyroid hormones.     

Chronopharmacological study of furosemide; (VIII) influence of feeding restriction

We have previously reported that a time-dependent variation is observed in the diuretic effect of furosemide and the light-dark cycle is a potent zeitgeber for this chronopharmacological phenomenon of the agent in rats. The present study was undertaken to examine whether a time of food intake is another zeitgeber for this event. In study I, rats were maintained with free access to food for 3 weeks. Furosemide (30 mg/kg) was given orally at 12 am or 12 pm. Urine was collected for 8 hours after the agent and urinary excretion of sodium and furosemide were determined. Thereafter, these rats were maintained under a daytime-restricted feeding schedule (9 am-11 am) for 3 weeks (study II) and a night-time-restricted feeding schedule (9 pm-11 pm) for 3 weeks (study III). The identical protocol of study I was repeated at the end of study II and III. Diuretic effect of furosemide and its urinary excretion were significantly greater at 12 am than at 12 pm in study I and III. However such an administration time-dependent change in the effect of furosemide and its urinary amount disappeared in study II. These data indicate that a time of food intake is another potent zeitgeber for the time-dependent variation in the diuretic effect of furosemide.