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  • Key words Aging  (1)
  • Thyroid ultrastructure  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Age delays thyroglobulin progression towards dense lysosomes in the cream hamster thyroid (1998)
    Springer
    Cell & tissue research 294 (1998), S. 125-135 
    Details
    ISSN: 1432-0878
    Keywords: Key words Aging ; Thyroid hormones ; Lysosomes ; Amyloidosis ; Sexual dimorphism ; Cream hamster (LHC/LAK)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  We have shown that large lysosomes appear in thyroids of aging male cream hamsters. To investigate the role of this lysosomal change in the age-dependent reduction in hormone secretion, thyroids of young (〈4 months of age) and old (〉22 months of age) male and female hamsters were labeled with 125I at near isotopic equilibrium. Changes in thyroid morphology were analyzed by light- and electron-microscopic morphometry. Changes in thyroglobulin processing were analyzed by subcellular fractionation and identification of 125I-compounds by sucrose gradients and reverse-phase high-pressure liquid chromatography (HPLC). Sexual dimorphism present in thyroids of young animals became more marked upon aging. The parallel increase in thyroid weight and thyroglobulin content was more conspicuous in old females than in old males. Two morphological observations were specific to old females: (1) large follicles with flat epithelium and evenly labeled colloid and (2) deposits of amyloid material (possibly immunoglobulin light chain-related) between follicles. Although lysosomes were enlarged in female and male aged thyroids, they did not accumulate iodine. However, after isopycnic centrifugation of crude lysosomal fractions in Percoll gradients, 125I in old thyroids was not distributed mainly in the dense fraction L1 (lysosomes) as in young thyroids, but partly in particles of lower density (light L2 and buoyant fractions). 125I in the lighter particles was mostly found in intact thyroglobulin and in large iodopeptides. This 125I shift towards less dense particles was more marked in females than in males. These results indicate that age delays thyroglobulin progression towards dense lysosomes and suggest that the slower traffic of thyroglobulin in the endocytic pathway contributes to the reduction in thyroid hormone secretion in the aged cream hamster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051162
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of aging on the morphology and function of the thyroid gland of the cream hamster (1981)
    Springer
    Cell & tissue research 220 (1981), S. 499-509 
    Details
    ISSN: 1432-0878
    Keywords: Aging ; Thyroid secretion ; Thyroid ultrastructure ; TSH stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of aging on the morphology and function of the thyroid gland of the cream hamster was studied by light and electron microscopy coupled with autoradiography or histochemistry. Morphologically, aging induces an accumulation of lysosomal dense bodies and a loss of the phagocytosis of colloid droplets after stimulation with TSH. Iodine uptake and organification occur normally and thyroglobulin synthesis, estimated by autoradiography with 3H-leucine, is not different from that observed in young animals. The basal T4 and T3 plasma levels are lower in the old animals. A low iodine diet administered for several months prevents the age related accumulation of lysosomal dense bodies. Hormone secretion seems to proceed by two different mechanisms; phagocytosis of colloid droplets, the classical mechanism that decreases with age, and an additional mechanism, probably micropinocytosis, that is maintained during the whole lifespan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216753
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    Paper (German National Licenses)
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