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At least 19 recordsLinked to original sources
PubMed1979

Ultrastructural and morphometric studies on the rat pituitary thyrotrophs and thyroid follicular cells following administration of thyrotropin releasing hormone.

The pituitary thyrotrophs and thyroid follicular cells of rats were studied by electron microscopy and morphometric analysis at 5, 10, 20, 30 and 60 min after intravenous injection of 200 microgram of thyrotropin releasing hormone (TRH) and at 10 min after injection of 10 microgram TRH. Multiple granule extrusions in a group were often observed around the pituitary thyrotrophs at 5, 10 and 20 min after administration of 200 microgram TRH, as well as at 10 min after injection of 10 microgram TRH. The number of released granules reached its maximum at 10 min after 200 microgram TRH injection, but the total number of secretory granules in the cytoplasm of thyrotrophs did not show any significant variation throughout the experimental period. Percent area of the rough endoplasmic reticulum indicated the maximum value at 20 min and that of the Golgi apparatus at 10 min. These findings suggest that TRH stimulates the thyrotroph and accelerates synchronously the secretion as well as the synthesis of TSH. In the thyroid follicular cells after 200 microgram TRH injection, numerous small vesicles which might be secretory granules were found in the apical cytoplasm at 5 and 10 min. Pseudopod formation on the luminal surface and accumulation of colloid droplets and lysosome-like granules in the apical cytoplasm were most frequently observed at 20 and 30 min. The value of the mean ratio of the diameter of the colloid lumen to the cell height of follicular cells in the thyroid follicles of all experimental animals stimulated with TRH decreased much more than that of the control animals. This value may indicate the increased activity of follicular cells to reabsorb the colloid.

Animals↗
PubMed1975

Paracrystalloids from mitochondria in thyroid follicular cells. Normal occurrence and experimental induction.

The ultrastructure of the follicular cells of the thyroid gland of bats caught in early June, when the euthyroid state is being restored following the phase of great thyroid activity that occurs at arousal, was studied. Several ultrastructural features were found which had not been observed in animals caught at other periods of the annual life cycle. The most striking ultrastructural feature was the presence in many cells of prominent, large membrane-enclosed paracrystalloid bodies. The paracrystalloids exceeded 6.0 mum in length and were approximately 1.0 mum. in width. Examination of transition forms showed that paracrystalloids were derived from mitochondria and were formed by the reorganization of the cristae into parallel closely apposed membranes. The membranes run longitudinally in loops from one end of the mitochondrion to the other. Similar mitochondrial alterations were observed in rats by duplicating the thyroid conditions of the June bat. Rats were given thiouracil for 10 weeks followed by L-triiodothyronine injection. These animals all showed similar mitochondrial-paracrystalline alterations which were not seen in hypophysectomized animals or animals given L-triiodothyronine alone. Mitochondria from thyroids of rats given thiouracil alone showed an increase in size and number and changes in shape and internal structure. The results of the bat and rat studies suggest that rapid shutdown of active follicular cells appears to promote thyroid paracrystalloid formation from mitochondria.

Animals↗
PubMed1979

Mitotic rate of thyroid follicular cells in untreated and goitrogen-treated rats: variation with time of day.

The paper presents the results of investigations into the mitotic rates of thyroid follicular cells of adult male rats maintained under controlled conditions of temperature, photoperiod and handling. The mitotic rate in eight successive 3 hour periods of the day showed a clear mitotic rhythm, with a maximum at 12.00--15.00 hours in untreated rats. The mitotic rate over the 24 hour period was 7.6+/-0.83(S.E.)metaphases/10000 cells/hour. Rats treated with the antithyroid drug, carbimazole, for three weeks were manifestly hypothyroid, as shown by decreases in oxygen consumption and rate of growth. With carbimazole the mitotic rate of the thyroid follicular cells was increased three-fold, and the mitotic rhythm was no longer detectable. In an experiment to test the efficiency of vincristine sulphate, the accumulation of metaphases after 1 mg/kg or 2 mg/kg vincristine was linear for 0.5--8 hours, although, at the higher dose, the number of metaphases was reduced after 8 hours. The mean daily mitotic rate in untreated rats was approximately commensurate with the rate of increase of body weight, which supports the classification of follicular cells as an 'expanding cell population'.

Animals↗
PubMed1976

A cytochemical analysis of the follicular cells and the yolk in the growing oocytes of Octopus vulgaris (Cephalopoda, Mollusca).

From an examination of the structural and cytochemical data obtained on the follicular epithelium and on the growing oocytes of Octopus vulgaris it has been possible to establish that, during the evitellogenetic period, the follicular cells penetrate into the oocyte cytoplasm and assume the form of cords. The yolk, which meanwhile has been constituted also through the probable contribution of material metiated by the follicular cells, is seen to be rich in neutral glycoproteins, proteins with sulphydrilic and thiolic radicals and proteins tyrosine and tryptophan containing, but is lacking in glycogen and in acid mucopolysaccharides.

Animals↗
PubMed1979

Testosterone synthesis by chicken follicular cells.

The roles of theca and of granulosa cells in the synthesis of testosterone (T) in ovarian follicle of hens have been studied. Theca cells alone synthesized no progesterone (P), and no or only negligible amounts of T. Granulosa cells, in contrast, without stimulation produced large amounts of P and small amounts of T. When incubated with ovine gonadotrophins, theca cells showed greater response than granulosa cells in synthesizing more T (2- to 2.5-fold increase). Combination of the two follicular cell types decreased synthesis of P, but increased that of T (9- to 17-fold). When 0.1 microgram of ovine luteinizing hormone (oLH) was added to the combined cells, T concentrations increased most dramatically, a 83-fold increase was seen after 12 h of incubation. Theca cells incubated with exogenous P also produced large amounts of T. These results indicated that in hens, theca cells may be the major site of follicular T synthesis, however, theca cells alone cannot synthesize T unless granulosa cells or P were added. It is suggested that granulosa cells may use P as a precursor, and that P is converted to T in the theca cells.

Animals↗
PubMed1978

Effect of gonadectomy on the follicular cell and inclusions in mitochondria of rabbit thyroid gland.

Thyroid glands of male rabbits were studied 2, 4, and 6 weeks after gonadectomy. In the gonadectomized group of animals, at the end of 2 weeks the follicular cell did not present any significant change except for the reduction of the supranuclear portion of the cell. By the end of 4 weeks there was a marked decrease in the microvilli of the apical border, dense granules, colloid droplets, ribosomes, and ergastoplasmic sacs. The lateral and basal cell margins were less convoluted. These changes reached a peak by the end of 6 weeks. The mitochondria with the inclusions also showed an apparent decrease in incidence at the end of 4 weeks and were rarely encountered by the end of 6 weeks. The thyroid gland morphologially resembled a hypothroid state, indicating that gonadectomy depresses the function and, therefore, may affect the metabolic process controlled by the gland.

Animals↗
PubMed1979

Fibronectin mediates cytokinesis and growth of rat follicular cells in serum-free medium.

In this study, the growth of rat follicular (RF-1) cells was severely depressed when the cells were subcultured by trypsinization directly into serum-free medium supplemented with insulin, transferrin and hydrocortisone, which are required for growth of these cells in vitro. Within 24 hr after plating, 50-65% of the cells became binucleated, indicating lack of cytokinesis. However, the addition of human plasma fibronectin (8 microgram/ml) to the serum-free medium eliminated cell binucleation and enhanced cell growth considerably. Fibronectin had the same effect when RF-1 cells were plated into tissue culture dishes on which fibronectin had been absorbed, and cells were inoculated into fibronectin-free medium. Cell binucleation and poor growth in serum-free medium occurred when the cells were subcultured by trypsinization, EGTA treatment or detachment of mitotic cells. Under some conditions, cells could be "rescued" if fibronectin was added soon after inoculation, indicating that fibronectin was needed mainly during a limited time when the subcultured cells were attaching to the tissue culture substratum. Our findings describe an adhesive activity for fibronectin which circumvents the serum preincubation usually needed after RF-1 cells are subcultured for growth in serum-free medium. They also indicate the importance of fibronectin-mediated adhesion for cytokinesis processes of these cells.

Animals↗
PubMed1978

Secretory kinetics in the follicular cells of silkmoths during eggshell formation.

Procedures for quantitative autoradiography were used for studying the process of secretion of eggshell (chorion) proteins in the follicular epithelium of silkmoths. The method was based on photometric measurements of the reflectance of vertically illuminated autoradiographic silver grains. Results were analyzed and plotted by computer. Secretory kinetics were also determined by analysis of labeled proteins in physically separated epithelium and chorion. Rapid accumulation of radioactivity into "clumps" visualized by light microscope autoradiography and evidence from preliminary electron microscope autoradiography indicate that, within 2 min from the time of synthesis, labeled chorion proteins move to Golgi regions scattered throughout the cytoplasm. The proteins begin to accumulate in the apical area 10-20 min later and to be discharged from the cell. The time for half-secretion is 20-25 min, and discharge is essentially complete 30-50 min after labeling. At the developmental stages examined, the kinetics of secretion appear to be similar for all proteins. Within the chorion the proteins rapidly assume a characteristic distribution, which varies for different developmental stages. Two relatively slow steps have been identified in secretion, associated with residence in Golgi regions and in the cell apex, respectively. By contrast, translocation of proteins across the cell and deposition of discharged proteins in the chorion are rapid steps.

Animals↗
PubMed1975

[Meiogenic function of follicular fluid. Gonadotropins and labeling with Na2 35SO4 in follicular cells and ovocytes in immature mice].

The injection in immature mouse of pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (HCG) with Na2 35SO4 in a strict equilibrium allowed us to show the concentration of 35S in the follicular fluid (meiogenic function) and around maturating oocytes (meiosis). This result allow new cytological progress in the field of vertebrates oogenesis.

Animals↗
PubMed2026

Ovarian expression and function of neuropeptide systems in teleosts and anurans.

The hypothalamic-pituitary-gonadal axis regulates reproduction, sexual maturation, and spawning behaviours. Its evolutionary origins trace back to primitive jawless fish and has been well characterized in teleosts. Recent advances in multi-species genome sequencing, annotation, and experimental approaches for identifying and characterizing key regulators have advanced understanding of neuroendocrine regulation in teleost reproduction, reshaping existing models. Early studies in amphibians established that steroids are critical regulators of final oocyte maturation. Subsequent work in anurans revealed complex interactions among theca cells, follicular cells, and oocytes, supporting a three-cell model in which oocytes contribute to their own steroidogenic environment, challenging the traditional two-cell view of ovarian steroidogenesis. In teleosts, however, direct evidence that oocytes support steroid precursor delivery to theca and follicular cells is limited, and whether a comparable three-cell model applies remains an open hypothesis. Across both taxa, the roles of locally produced neuropeptides in coordinating interactions among theca cells, follicular cells, and oocytes remain largely uncharacterized. Here, we provide a short review of the localization and potential autocrine/paracrine functions of neuropeptides in teleost and amphibian ovaries and discuss existing knowledge gaps. We identify opportunities to leverage detailed localization studies that map neuropeptides to specific ovarian cell types and developmental stages, and discuss how integrating traditional and emerging experimental approaches can advance comparative studies in ovarian endocrinology. This work will improve our understanding of reproductive regulation in fishes and frogs, with applications in captive breeding, aquaculture, and endocrine disruption research.

Autocrine↗
PubMed1975

[Critical study of extra-lysosomal acid phosphatase localizations in thyroid follicular cells by the Gomori reaction (author's transl)].

With the Gömöri technique, lead precipitates have been found in thyroid follicle cells in unusual localizations such as apical hyaloplasm and microvilli; it has been established that they were actually significant for acid phosphatase activity: constant results in spite of repeated controls and several variations from the original cytochemical technique, allow to think that lead precipitates were not merely artefactual, but actually significant of enzymatic activity. However it is pointed to the fact that the origin of the enzyme has to be questioned; it is assumed that most likely acid phosphatase has diffused from its original lysosomal site. Such diffusion implies variations of the selective permeability of lysosomal membranes; inappropriate relation between the quantity of enzyme present in these organelles and the quantity of substrate used might also be considered, though changes in the amount (resp. concentration) of substrate remained ineffective and induced no modification in the localization of observed enzymatic activity. In addition, one point of interest is an obvious relation between the observed enzyme diffusion and the state of activity resp. rest of the cell; in the present state of investigations, this remains unexplained and likely related to factors escaping control during processing; moreover, no explanation can be provided for the fact that it revealed impossible to avoid such diffusion even by means of variations of the numerous parameters involved in the Gömöri technique. So that it finally appears necessary to remain on a critical position regarding the results at the ultrastructural level of this standardized technique, and there is no doubt it would reveal useful that several assumptions in the literature about extra lysosomal acid phosphatase activity should be reinvestigated with a similar critical purpose.

Acid Phosphatase↗