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  • 1
    Electronic Resource
    Electronic Resource
    Melatonin Inhibits Mitotic Activity of Adrenocortical Cells In Vivo and in Organ Culture (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 7 (1989), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The goal of this study was to examine the effects of melatonin, as well as those of melatonin and corticotropin (1–24 adrenocorticotropic hormone (ACTH); Synac-then Depot) administered together, on the mitotic activity of adrenocortical cells in male and female mice. Melatonin was given subcutaneously once daily, in late-afternoon injections (between 16: 00 and 18: 00) in doses of 1 μg, 10 μg, and 100 μg, and ACTH in a dose of 0. 1 mg (10 U) daily for 10 days. Additionally, the highest dose of melatonin (100 μg daily) was administered together with ACTH. The metaphase-arrest technique using colchicine as a stathmokinetic agent was employed in the study. Melatonin, in all the examined doses, significantly decreased mean mitotic activity rate (MMAR) of the adrenal cortex in both male and female mice. Moreover, in a dose of 100 μg, melatonin suppressed the mitogenic effect of ACTH on the adrenal cortex.Furthermore, the present study investigated the effects of melatonin (5 × 10−7M), N-acetylserotonin (NAC-5HT) (5 × 10−7M), and ACTH (250 mU/ml or 1,000 mU/ml) alone as well as the effect of ACTH (250 mU/ml) applied jointly with melatonin on the mitotic activity of adrenocortical cells in rat adrenal explants incubated in vitro. Both pineal indoleamines (melatonin and NAc-5HT) significantly decreased the MMARs of adrenocortical cells. Corticotropin, as well as ACTH and melatonin applied together, also reduced the MMAR of adrenocortical cells.The present data suggest that melatonin may be directly involved in the inhibitory control of adrenocortical cell proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1989.tb00436.x
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  • 2
    Electronic Resource
    Electronic Resource
    Melatonin Suppression of the Colloid Droplet Formation in the Thyroid Is Not Related to the Alteration of Prostacyclin Synthesis (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 3 (1986), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The goal of the present investigation has been to compare the effect of melatonin on the early secretory event in the thyroid follicular cells (thyroglobulin endocytosis; colloid droplet [CD] formation) and the effect of this pineal indoleamine on the release of a stable prostacyclin (PGI2) metabolite, 6-keto-PGF1α from the thyroid. 6-keto-PGF1α is believed to be a good index of PGI2 synthesis, since PGI2 is not stored within the tissue, but is continuously formed and released. We found that melatonin, administered to rats as daily subcutaneous injections at a dose of 25 μg and/or 250 μg for a total of 3 days, inhibited the CD formation. Moreover, melatonin partially suppressed the stimulatory effect of TSH on the CD formation. In turn, melatonin did not affect 6-keto-PGF1α release in basal conditions, but blocked the stimulatory effect of TSH.It is concluded that melatonin decreases the thyroid secretion acting by a mechanism that is independent of the effect of this hormone on PGI2, synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1986.tb00751.x
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  • 3
    Electronic Resource
    Electronic Resource
    Melatonin Inhibits the Basal and TSH-Stimulated Mitotic Activity of Thyroid Follicular Cells In Vivo and in Organ Culture (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 3 (1986), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The aim of the present study has been to examine the effect of melatonin, administered to mice as daily subcutaneous injections for a total of 10 days, on the mitotic activity of thyroid follicular cells (TFC). The colchicine metaphasearrest technique was employed in the experiment. We found that melatonin (10μg and/or 100μg injection) decreased significantly the mean mitotic activity rate (MMAR) of TFC in both male and female mice. Moreover, melatonin totally suppressed the stimulatory effect of TSH on the MMAR of TFC in both sexes of mice.Furthermore, the effect of melatonin (5 × 10−7 M) on the proliferation of TFC in the organ-cultured rat and mouse thyroid explants was investigated. It was found that melatonin almost totally suppressed the MMAR of TFC in organ culture. Moreover, melatonin blocked the stimulatory effect of TSH on the MMAR of TFC in both rat and mouse thyroid explants. N-acetylserotonin (NAc-5HT, 10−6 M) also decreased the MMAR of cultured thyroid explants, but its effect was less expressed when compared to melatonin inhibition.The present data indicate that melatonin can exert its inhibitory effect on the proliferation of TFC directly at the thyroid level, since this pineal indoleamine has been shown to suppress not only basal but also TSH-stimulated mitotic activity.The results are in agreement with the hypothesis of a pineal-thyroid negative feedback, assuming the direct inhibitory effect of melatonin on the thyroid growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1986.tb00752.x
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  • 4
    Electronic Resource
    Electronic Resource
    Further evidence of inactivity of hypothalamo-pituitary-thyroid axis in snell dwarf mice (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 210 (1984), S. 617-627 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The effects of hemithyroidectomy (hemiTX) and complete thyroidectomy (TX) on the cellular composition and the mitotic activity of the anterior pituitary gland were examined in genetically thyrotropin (TSH)-deficient female Snell dwarf mice (dw/dw) and in phenotypically normal female mice (?/+) from the same strain. In normal (nondwarf) mice, both hemiTX and TX reduced the percentage of acidophilic (orange G-positive) cells and increased the percentage of thyrotropic (aldehyde fuchsin [AF]-positive) cells, whereas the percentage of gonadotrophs (PAS-positive cells) and chromophobes (unstained cells) was not affected. Both interventions increased the mean mitotic activity rate (MMAR) of the anterior pituitary lobe. This effect was related to the enhancement of the MMAR of acidophilic cells and, particularly, thyrotropic cells. The MMAR of thyrotrophs in thyroidectomized normal mice was significantly higher than that in sham-TX controls or in hemithyroidectomized animals.In Snell dwarf mice, neither hemiTX nor TX affected the percentage of the various cell categories (PAS-positive, unstained, and extremely rare AF-positive cells) in the anterior pituitary lobe. Furthermore, neither hemiTX nor TX substantially influenced the MMAR of the gland. No mitotic figures were found in the AF-positive cells. Since the AF-positive cells in the anterior pituitary of dwarf mice completely failed to respond to hemiTX or TX, we believe they are not true thyrotropic cells.Using electron microscopy, we confirmed a lack of somatotrophs, mammotrophs, and normal thyrotrophs in the anterior pituitary of Snell dwarf mice. The results provide morphological evidence of inactivity of the hypothalamo-pituitary-thyroid axis in Snell dwarf mice.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092100409
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of intraventricular injections of 6-hydroxydopamine on anterior pituitary cell proliferation (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 208 (1984), S. 421-426 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Effects of intraventricular injections of 6-hydroxydopamine (6-OHDA; 200 μg/20 μl vehicle) on anterior pituitary cell proliferation in rats have been investigated by means of the colchicine metaphas-arrest techniques. In those groups of animals receiving 6-OHDA alone or 6-OHDA plus desmethylimipramine (DMI, 25 mg/kg body weight i.p.), where the mean mitotic activity rates (MMARs) were initially low at 48 hours, an increase of MMARs was observed at 96 and 144 hours after the drug injections. At 144 hours after drug administration, the MMARs values in the 6-OHDA-injected group and in the 6-OHDA+DMI-treated group were significantly higher than those in the control groups. This increase of MMARs resulted from the enhancement of acidophilic and chromophobe cell proliferation. The low MMARs at 48 hours after 6-OHDA injection are probably a result of dopamine release from damaged nerve endings; the enhancement of MMARs (particularly evident in the 6-OHDA+DMI-treated group) at 96 and 144 hours after drug adminstriation is presumably related to a deficiency of dopaminergic control of anterior pituitary cell proliferation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092080312
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  • 6
    Electronic Resource
    Electronic Resource
    Stimulus-permeability coupling in rat pulmonary macrophages challenged by Pseudomonas aeruginosa (1985)
    Springer
    Cell & tissue research 240 (1985), S. 461-465 
    Details
    ISSN: 1432-0878
    Keywords: Macrophage activation ; Pseudomonas aeruginosa ; X-ray microanalysis ; Elemental analysis ; Electrolytes ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron probe X-ray microanalysis (XRMA) of freeze-dried ultrathin sections provides the capability of measuring intracellular elemental content. This methodology was used to investigate the stimulus-permeability coupling responses associated with phagocytosis of Pseudomonas aeruginosa by cultured pulmonary alveolar macrophages (PAMs) of rats. PAMs were challenged with P. aeruginosa suspended in Gey's buffer at a bacteria to PAM ratio of 50∶1 for 1 h at 37° C. A 1-mm3 pellet of the unchallenged control PAMs, challenged PAMs and P. aeruginosa alone was quench-frozen in nitrogen-cooled, liquid propane, and 0.1-μm cryosections were cut at -100° C. X-ray spectra were collected for nucleus and cytoplasm of 39 control PAMs, 36 challenged PAMs and 40 P. aeruginosa. Concentrations (mmole/kg dry weight) were obtained for Na, Cl, K, Ca, Mg, P, S for each cell. In the control PAMs, the content was similar to other mammalian cells. Moreover, there were no differences in elemental content between nucleus and cytoplasm. In the challenged PAMs, Na concentration was 4 times that of control PAMs (p〈0.001) whereas Cl was double (p〈0.001), K was 29% lower (p〈0.001), and Ca was 4 times higher (p〈0.05). The elemental concentration profile in the P. aeruginosa was distinctly different from that of the PAMs: higher Na, Ca, Mg, but lower Cl and K values. These results demonstrate elemental content changes in cultured PAMs challenged with P. aeruginosa that indicate a stimulus-permeability response by membranes associated with the phagocytic process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222360
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