Origin of cholinesterase-containing follicle cells and parafollicular cells of the developing thyroid gland in the rat

Summary The location of cholinesterase-containing cells in the thyroid gland and its precursors (median thyroid primordium and ultimobranchial bodies) has been investigated light-microscopically in rat embryos from the 13 to the 20th day of gestation.From the 13th to the 16th day of gestation the median thyroid primordium and the ultimobranchial bodies are distinct from each other. Cholinesterase-containing cells are found in both. On the 17th–18th day of gestation the reacting ultimobranchial cells spread into the median thyroid primordium where they take up a parafollicular position. At the 19th–20th day of gestation the distribution of cholinesterase-containing cells is as in the adult rat. The results seem to show that cholinesterase-containing follicular cells derive from the median thyroid primordium and cholinesterase-containing parafollicular cells from the ultimobranchial body.     

Proliferating cell nuclear antigen of the rat thyroid gland before and after birth]

We were studied the proliferative activity of the thyroid gland's cells of embryo and adult Wistar rats due to using the antiserum against the cell nuclear antigen (PCNA). The 100% of cells in thyroid's embryo was a positive on the 16th, 17th, 18th stages of the embryonic development (stages by Kornegy). The percent of PCNA-positive cells considerably increased to 67% on the 19th stage. This fact the 20th and 21th stages of prenatal development relatively the previous stage coordinate with starting of the thyroid hormones in fetal thyroid gland and the first follicles formation. The small increasing of number of PCNA-positive cells detected on the 20th and 21th stages of prenatal development relatively the previous stage. Considerable elevation of the proliferating cells to 75% immediately before the birth (22th stage). An infant rats had have the 39% of proliferating cells. The 51% cells divided on the 5th day of postnatal development. Considerable decreased of the cell's division was occurred until the postnatal day 60. Using of the PCNA antiserum allowed to study cell proliferation in thyroid gland during pre- and postnatal rat development.     

The effects of adrenalectomy and hydrocortisone replacement on the thyriod of the adult male rat I. Morphometrical data and histochemistry of some oxidative enzymes.

Morphometrical and histochemical studies were performed to determine the effects of adrenalectomy and hydrocortisone replacement on the rat thyroid. It follows from the performed studies that morphometrical and histochemical changes in the rat thyroid induced by adrenalectomy or hydrocortisone replacement depend upon the duration of the experiment. From the 4th day of the experiment adrenalectomy results in an increase in the volume fraction of the epithelium of the thyroid vesicles with a concomitant decrease of the colloid fraction. As compared to sham operated animals on the 10th day of the experiment the increase in the height of the epithelial cells was seen. Hydrocortisone replacement partially prevents the thyroid changes induced by adrenalectomy, however, this hormone markedly increases the volume fraction of the thyroid stroma and the height of the epithelial cells. On the other hand, histochemical reactions for various oxido-reductases do not provide helpful information for evaluation of the secretory activity of the rat thyroid. It follows from our results that adrenalectomy enhances thyroid stimulation by TSH and enhances the secretory activity of this gland, effects partially prevented by hydrocortisone replacement.     

Morphofunctional characteristics of the recovery processes in the resected thyroid of rats

Histological, electron microscopy and radiometry methods were used to study the time-course of the recovery of the morphological and functional parameters of the rat thyroid after resecting 2/3 of the organ. The signs of thyrocyte regeneration, namely hypertrophy of the cells and ultrastructures, proliferation and formation of new follicles were most pronounced on the 5th day. The increase in the number of C cells, their hypertrophy and proliferation permit attaining the high calcitonin level in the blood serum, reaching a maximum on the 15th experimental day.     

APPEARANCE AND FUNCTION OF ENDOGENOUS PEROXIDASE IN FETAL RAT THYROID

Iodination within the thyroid follicle is intimately associated with a thyroid peroxidase. In order to locate the in vivo site of iodination, the initial cytochemical appearance of this enzyme has been determined in fetal rat thyroid and its presence correlated with the onset of iodinated thyroglobulin synthesis. Peroxidase first appears in follicular cells during the 18th day of gestation. It is seen first in the perinuclear cisternae, the cisternae of the endoplasmic reticulum, and within the inner few Golgi lamellae. These organelles presumably represent sites of peroxidase synthesis. During the 19th and 20th days of gestation, there is a tremendous increase in peroxidase activity. In addition to the stained sites described, there are now many peroxidase-positive apical vesicles in the follicular cells. Newly forming follicles stain most conspicuously for peroxidase, the reaction product being heavily concentrated at the external surfaces of apical microvilli and in the adjacent colloid. Iodinated thyroglobulin becomes biochemically detectable in thyroids during the 19th day of gestation and increases greatly during the 20th day. The parallel rise in peroxidase staining that just precedes, and overlaps, the rise in iodinated thyroglobulin, suggests that apical vesicles and the apical cell membrane are the major sites of iodination within the thyroid follicle.     

Chronic effect of TSH on human thyroid tissue in organ culture

The chronic effect of TSH on thyroidal cAMP concentrations and release of thyroid hormones was investigated using human thyroid tissue in organ culture. Normal human thyroid slices were placed in HAM's F-10 synthetic culture medium in Falcon organ tissue culture dishes, and incubated at 37 degrees in a humidified atmosphere of 5% CO2 in air. Medium was changed everyday and daily T3 or T4 release was determined using concentration of T3 or T4 in the medium. After incubation, slices were transferred to the medium containing 10 mM theophylline and incubated without TSH for an additional 30 min to determine thyroidal cAMP concentrations. Thyroidal cAMP concentrations in slices incubated with 10 mU/ml of TSH increased significantly at 2, 6, and 24 hr and even on the 6th day of incubation. Daily T3 release was significantly increased above control from the 3rd day and daily T4 release from the 4th day to the 11th day of incubation with 10 mU/ml of TSH. Histologically, almost all follicles were structurally maintained even on the 11th day of incubation. These results suggest that both thyroidal cAMP concentrations and release of thyroid hormones are stimulated chronically by TSH. This organ culture system is useful for investigating chronic effects of various materials on human thyroid tissue.     

Thiocyanate effects on thyroid function of weaned mice

The aim of this study was to determine the effects of thiocyanate on thyroid function in weaned mice. At this developmental period, induction and reversibility of thiocyanate effects have not yet been studied. In the present work, adult female mice were given thiocyanate [SCN(-) (1 g L(-1))] in their drinking water from the 15(th) day of pregnancy until either the 25(th) (group B) or the 15(th) day (group C) after parturition. During five days after weaning, water and food consumptions of treated mice (group B) were 42.2+/-1.2% and 56.4+/-0.9%, respectively, less than those of the controls (group A). On the sacrifice day (the 25(th) day after birth), body weight, thyroid iodine content and thyroid hormone levels (FT(4) and FT(3)) decreased by 10.4+/-3.0%, 40.6+/-2.3%; 18.7+/-2.3% and 18.1+/-1.3%, respectively. Plasma TSH increased by 30.6+/-1.7% along with the hypertrophy of thyroid glands (52.6+/-3.1%). We have observed a hypertrophy of follicle cells and a decrease in colloid volume within histological slides. After SCN(-) withdrawal (group C), partial or total recovery were noted in all parameters studied. We concluded that hypothyroidism effects added to the weaning event affected greatly thyroid function and behaviour of mice; these would be largely reversed by withdrawing thiocyanate treatment for a period of ten days.     

Morphofunctional features of the development of the thyroid gland of Dicrostonyx torquatus during the drop in population stage

By means of the histostereometrical method, peculiarities of the thyroid gland formation have been studied in the lemming (Dicrostonyx torquatus) fetuses and newborns at the stage of the population quantity drop, as well specificity of the organ's morphofunctional state during the postnatal period. On the 14th prenatal day the thyroid gland already has the follicular structure. Up to the 19th day progressive follicular growth, accumulation of colloid and increase of its density occur. On the 19th-20th days, as well as in newborn animals, there are certain signs, demonstrating as essential activation of the thyroid gland function. In the newborn animals cavities of the completely formed follicles are devastated. During the postnatal period again growth of follicles, accumulation of colloid are observed, signs of hypersecretion of the hypophysis appear.     

Reactions of oxytocin- and vasopressinergic cells of the hypothalamic supraoptic and paraventricular nuclei in the rat to repeated administrations of thyroliberin

Male Wistar rats were injected with 1 microgram thyroliberin twice a day for 8 days. Vasopressinergic (VE) and oxytocinergic (OE) cells of the supraoptic (SON) and paraventricular nuclei (PVN) were detected immunohistochemically, their changes were estimated morphometrically. The blood level of the thyrostimulating hormone determined by radioimmunoassay was 220% of the control on the 6th day but declined by the 9th day. The thyroid hormone concentration was also diminished. The nucleoli of the VE and OE cells of the SON were reduced by the 9th day (by 74 and 82%, respectively; P less than 0.01). The nucleoli of the OE cells of the PVN were enlarged to 120% (P less than 0.01), hence production of the neurohormone by these cells was intensified. The VE cells of the PVN remained essentially unchanged. The data obtained suggest that disagreement between the PVN and SON cell reactions is caused by various reactions of the nerve centers conveying toward the PVN and SON. Moreover, the OE and VE cells of the PVN apparently differ in their input. The importance of the OE cells of the PVN for the thyrostimulating hormone level normalization is suggested.     

Features of the development of the pituitary-thyroid system of the Wrangel Island hoofed lemming Dicrostonyx torquatus at stages of growth and peak population

By means of morphometric techniques, peculiarities in formation of the hypophyseal-thyroid system during prenatal and early postnatal periods have been studied in lemmings (Dicrostonyx torquatus) from the Wrangel island at growth stages and at the peak of the population quantity. Folliculoformation rate, time when the organ reaches the definitive structure, periods for establishing connection with the regulating center--the anterior hypophyseal lobe, correlation of differentiation rates of histo- and ultrastructures of the organ distinctly react to changes in the density population of the animals. Periods of initiation of folliculoformation are early and comparable at both stages of the population cycles. However, further at the peak of the population quantity, an essential retardation in the development of both histo- and ultrastructures of the thyroid cells is observed; formation of the histostructure significantly overtakes differentiation of the ultrastructures composing its cellular elements. The follicular structure begins to form only in newborn animals, the folliculogenesis completes on the 1st-6th days of the postnatal period. At the stage of growth of the population quantity, the folliculogenesis lasts 2 days (the 15th-17th days of the prenatal development), the organ's structure becomes definitive on the 17th day, at the same period connections are established with the anterior hypophyseal lobe. The role of the thyroid hormones in formation of reprodactive and adaptive potencies of the organism at various stages of the population cycle is discussed.     

Involution of hyperplastic goitre in the adult male rat. Tissue compartment process with early iodide effect: a stereological and biochemical study

The morphological and functional changes during involution of hyperplastic goitre have been investigated in the adult male rat. Male wistar rats received an iodine-deficient diet for 6 months and during the last 2 months received propylthiouracil (PTU, 0.15%). By the end of this treatment (day 0), a hyperplastic goitre was obtained. A normal iodine supply was then given and PTU withdrawn. During the first 8 days of iodine refeeding, the plasma thyrotropin (TSH) remained at a high level (ten times the control value), whereas the thyroid iodide content was low on day 0, markedly increased on day 1 and decreased on day 4. Plasma T3 and T4 levels remained unchanged for 4 days and only increased on day 8. The total thyroid protein concentration was low on day 0 and then increased rapidly on day 8 (by 34%). The volume density of colloid remained low and unchanged until day 8, when it started to increase. However, the thyroid epithelial cell volume and the volume density of capillaries were raised on day 0, decreased rapidly in the next 8 days and more slowly later on. The total number of thyroid epithelial cells was considerably raised in the hyperplastic gland. It did not vary until day 16, when it decreased slowly, reaching a plateau on day 45 above the control value. The present data show that involution of hyperplastic goitre in the rat is due essentially to a decrease in thyroid epithelial cell volume and to a reduction of the increased number of capillary blood vessels present. The decrease in the number of epithelial cells is only 16.5%, suggesting that the death of thyroid epithelial cells contributes little. Half the process of involution, which occurs from days 0 to 8, is controlled by the thyroid iodide concentration rather than TSH, indicating the involvement of a thyroid autoregulatory mechanism. It must be emphasized, however, that the discontinuous pattern of epithelial cell number during involution may indicate that some cells with larger nuclei and more rapid turnover disappear more quickly after iodine refeeding.     

Cytodifferentiation of the adenohypophysis of the domestic fowl

Summary In the chick embryo the first membrane-bound secretory granules occur in the cytoplasm of occasional cells in the cephalic lobe of pars distalis at the 7th day of incubation. On the 8th day most of the cells in both the cephalic and caudal lobes contain secretory granules that are variable in size, form and density.On the 9th day at least two types of glandular cells are distinguishable in the cephalic and in the caudal lobes; however, these cells are not comparable with those of the adult gland. Differentiation of acidophils and basophils occurs, apparently simultaneously, in 11-day embryos.The cells of the cephalic and caudal lobes are morphologically distinct from their first appearance. Thus it is concluded that these two lobes develop independently and differently from an early stage of ontogenesis.The secretory granules are formed in the Golgi area of the hypophysial cells after the 8th day of incubation. However, secretory material may be synthesized also by a process not involving the Golgi apparatus.Nerve fibers containing granules first appear in the superficial layer of the median eminence on the 8th embryonic day and by the 12th day three types of granules and two types of clear vesicles are identifiable.The investigation reported herein was supported by grant from Japan-U.S. Cooperative Science Program of Japan Association for Science Promotion to Professor Mikami and by U.S.-Japan Cooperative Science Program Grant No. GF-33334 to Professor Farner.     

Transfer of iodine through the milk in protein-restricted lactating rats

Iodine supply is important to avoid neonatal hypothyroidism. This study evaluated whether protein restriction during lactation affects iodine transfer to the pups through the milk. We studied lactating rats fed an 8% protein-restricted diet (PR), a control 23% protein diet (C), and an energy-restricted diet group (ER). On days 4, 12 and 21, mothers were separated from their pups for 4 h, injected with (131)I IP, and put together with their pups. The animals were killed 2 h later. PR pups had a significant decrease in iodine uptake in the gastric content and duodenal mucosa on the 4th day. On the contrary, at 12 and 21 days radioiodine was increased in the gastric content and in the duodenal mucosa. ER pups had an increase in iodine uptake in the gastric content and in the duodenal mucosa only at the end of lactation. The thyroid iodine uptake in PR pups was significantly decreased on the 4th day and significantly increased on the 21st day compared to control. When injected IP with an equivalent amount of (131)I, the PR pups had a decrease in thyroid iodine uptake on the 4th and 12th day, while ER pups had no significant changes. So, these data suggest that protein restriction during lactation was associated with lower iodine secretion into the milk in the beginning of lactation. However, at the end of lactation, an adaptation process seems to occur leading to a higher transfer of iodine through the milk that compensates the impairment of thyroid iodine uptake in these pups.     

Effect of thyroxine administration to the mother on postnatal radioiodine uptake by the thyroid of partially thyroidectomized rats.

The experiment was carried out on 35 litters of infant rats aged 4-17 days. The animals in each litter were always divided into two groups: control (sham operation) and experimental (hemithyroidectomy). Starting with the day on which the young were operated on, the mothers received daily subcutaneous injections of either saline or of thyroxine in doses of 50, 100 or 200 mug. At the end of the experiment, the young were injected intraperitoneally with 1 muCi 131I. One hour later they were decapitated and the radioactivity in their thyroid was expressed as the percentage of the administered dose per mg thyroid. The following age groups were used, according to the interval between thyroidectomy and decapitation: 4 to 8, 9 to 13, 13 to 15 and 15 to 17 days. 131I uptake by the residue of the thyroid in partially thyroidectomized animals was always compared with the values in the animals from the same litter subjected to sham operation. The results showed that partial thyroidectomy significantly stimulated 131I uptake in all age groups in which the mother was only given saline. In the 4- to 8-day-old group, the administration of 50 or 100 mug thyroxine to the mother inhibited this compensatory increase. In the 9- to 13-day-old group, inhibition occurred only after a dose of 100 mug thyroxine. In animals with an interval from the 13th to the 15th days old the dose of thyroxine administered to the mother had to be raised to 200 mug/day to achieve an inhibitory effect. In the last group (interval 15th to 17th day), not even administration of the maximum thyroxine dose to the mother from the 13th postnatal day succeeded in inhibiting the significant increase in 131I uptake. These results show that thyroxine administered to lactating female rats can be transmitted via the milk to the organism of the young in amounts which can be demonstrated in a physiological tests.     

Action of acetazolamide on the chick embryo during late development.

Acetazolamide was injected into chick embryos on the 14th or 15th day of incubation. Doses ranging between 5 and 10 mg per egg produced a retardation in the growth of long bones. The affected bones contained a normal proportion of mineral as determined by ashing and presented a normal histological picture. On the basis of these findings, it is suggested that the alterations were not due to a specific direct effect of the drug on bones. The incorporation of 131-I by the thyroid glands of acetazolamide-injected embryos was analyzed radioautographically and quantitated on the same 6 mu-paraffin sections, with a thin window Geiger counter. The incorporation appeared notably reduced 3 h after the injection of acetazolamide and the reduction persisted for a least 24 h.the electron microscopical observation of thyroid follicular cells from similarly treated embryos showed that the cytological characteristics indicating an active protein synthesis were unmodified with respect to those found in control embryos. These results may indicate that acetazolamide inhibits the iodination of the throid hormone without interfering with the synthesis of the globulin. It is suggested that the growth retardation observed in the embryos treated with acetazolamide may be secondary to the action of the drug on the thyroid gland, although this action appears to be a transitory one.     

The action of the cells of hemopoietic organs in chick embryos on mouse CFUdc and CLFUdc]

The humoral influence of cells of hemopoietic organs of chicken embryos of different terms on the development of the colony and cluster formation of mononuclears of the bone marrow of mice was studied in joint cultivation in two-compartment cylindrical diffuse microchambers. The process of formation of colonies and clusters is inhibited by cells of the yolk sac on the 2nd-4th day of the development, by cells of the liver on the 8th-12th day, of the spleen on the 13th-18th day and of the bone marrow--on the 15th day. The yolk sac cells were found to have most considerable inhibiting influence on proliferation and differentiation of cells on the 2nd day of the development of chicken embryo. The yolk sac cells on the 6th day stimulate the formation of colonies and clusters. The yolk sac, beginning from the 4th day of the development, and the liver release humoral factors promoting the formation of erythroid colonies. The erythroid colonies are formed but when cultivated on the vascular membrane of the chicken embryo; the erythroid colonies are not formed when cultivated in the abdominal cavity of mice. Local erythropoietinoid factors are not synthetized by the spleen and bone marrow cells. A supposition is put forward that a combination of the local inhibiting and erythropoietic effects promotes the erythroid differentiation of cells.     

Light and electron microscopic studies on the development of the spiral prominence of the cochlear duct of the fetal guinea pig

The anlage of the spiral prominence can be seen on the 37th day of development as a small protrusion of the epithelium towards the lumen of the cochlear duct. During the further progress, the spiral prominence more distinctly protrudes by augmentation of the vascularized connective tissue. In the epithelial cells pinocytotic vesicles near the plasmalemma are seen earliest lateral and basal on the 37th day, apical on the 39th day. The epithelial cells send basal cytoplasmic extensions towards the connective tissue. Starting on the 44th day, small invaginations of connective tissue extend into the epithelium, remaining separated from the epithelial cells by the basal lamina. Until the 48th day, the monostratified epithelium remains columnar, thereafter it changes to cuboidal or flat. Towards the end of the development, the invaginations of the connective tissue nearly reach the surface of the epithelium, being separated from the endolymph by a small epithelial area.     

Regulation of the mitochondrial anabolism at low concentrations of thyroid hormones and by some of their structural analogues.

The Authors demonstrate that the in vitro stimulation of mitochondrial RNA synthesis produced by thyroid hormones takes place also at physiological levels, equal to those held in the liver cells of experimental animals. Two groups of male rats have been used: normal control animals (N) and animals surgically thyroidectomized on the 25th day of life (T). The animals were fed and kept in standard conditions and killed on the 85th day of life. The purification of mitochondrial samples and the determination of the mitochondrial RNA synthesis were carried out as previously described. The results suggest that the in vitro stimulation of mitocondrial RNA synthesis is already significant at the concentration of lnM. The trends are qualitatively comparable for either N or T animals. The structural analogues TRIAC (3,5,3'-triiodothyroacetic acid) and TRIPROP (3,5,3'-triiodothyropropionica acid) exhibit a clearly stimulatory effect on samples of N animals, while on samples of T animals is significant only for the first analogue. Similar trends are also observed on ADP/O ratio.     

Development of substance P and neurokinin A immunoreactivity in ganglia supplying nerves to the submandibular glands of the rat

Developing submandibular, trigeminal and superior cervical ganglia, which provide innervation to the submandibular glands, were studied for substance P (SP)-and neurokinin A (NKA)-immunoreactive (IR) ganglion cells and nerve fibres in rat. These ganglia were examined by using an indirect immunofluorescence technique at daily intervals from the 16th day in utero (i.u.) until birth, and subsequently on the 2nd, 5th, 7th, 12th, 16th, 30th, 42nd postnatal day and in the adult (3 months). In the submandibular ganglion SP- and NKA-IR cells and fibres first appeared in considerable numbers on the 19th day i.u. (in one sample out of five on the 18th day i.u.), when more than 90% of the ganglion cells were immunoreactive to SP and NKA. The number stayed at more than 90% to the 7th postnatal day and then slowly decreased to the levels of adult animals (18% SP, 17% NKA). The first SP- and NKA-IR ganglion cells and fibres appeared in the trigeminal ganglion on the 18th day i.u. when they represented 7% (SP) and 4% (NKA) of the ganglion cells. The number of SP- and NKA-IR cells increased steadily, reaching a maximum at the time of birth when 68% (SP) and 74% (NKA) of the ganglion cells were immunoreactive. Thereafter they began to decrease toward the level of an adult rat (10% SP, 11% NKA). In the superior cervical ganglion only a few SP-and NKA-IR ganglion cells were detected from the 19th day i.u. to the fifth postnatal day. Positive ganglion cells were also occasionally found in the nerve trunks outside the superior cervical ganglion. From the seventh day onwards no SP- or NKA-IR ganglion cells were found. SP-and NKA-IR SIF (small intensively fluorescent) cells were detected from the 16th postnatal day onwards.     

Cyclic AMP as the second hormonal messenger in the in vitro folliculogenesis of the foetal thyroid gland of the rat

Thyroid-stimulating hormone, the catecholamine isoproterenol, and prostaglandins E1 and E2, all substances known to increase cAMP concentration in thyroid tissue, accelerate the formation of follicular cavities in explanted thyroid of 15-day-old rat foetuses. Dibutyryl-cAMP added to the medium, but not sodium fluoride, also stimulates the folliculogenesis. Since fluoride stimulates membrane adenylate cyclase but does not increase the intracellular cAMP level, these results show that cAMP is involved as a second messenger in the activation of foetal thyroid morphogenesis induced by hormones. They indicate also that the thyroid gland of the foetal rat is capable of responding to hormonal stimulation as early as the 15th day of pregnancy; this implies that on day 15, the foetal thyroid possesses receptors not only for the thyroid-stimulating hormone, but also for catecholamines and prostaglandins.