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      Altered thyrotropic and somatotropic responses to environmental challenges in congenitally athymic mice.

      1 , , ,
      Brain, behavior, and immunity
      Elsevier BV

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          Abstract

          Neonatal thymectomy or congenital absence of the thymus induces morphologic alterations in pituitary somatotrophs as well as in thyroid epithelium. It was therefore of interest to assess somatotropic and thyrotropic cell morphology and the corresponding serum hormone levels in athymic nude mice under basal and stressful conditions, taking as a reference their haired counterparts. Normal (+/+), heterozygous nude (nul+) and homozygous (nu/nu) CD-1 mice were subjected to either 1-h immobilization stress or 2-h cold stress. Serum levels of growth hormone (GH), thyrotropin (TSH), thyroxine (T4), and triiodothyronine (T3) were assessed by RIA at 0, 30, and 60 min poststress. Athymic animals showed lower basal levels of serum TSH, GH, and T3, but not T4, than their heterozygous littermates. Immunohistochemical assessment of somatotropic and thyrotropic cell populations revealed a normal morphology in the athymic animals. Immobilization stress induced a marked reduction in GH and TSH levels in normal mice but had only a weak effect in athymic animals. Two hours of cold exposure caused a comparable increase in serum TSH in normal and athymic animals, whereas the serum T4 and T3 response to cold was greater in the athymic nudes. Cold exposure drastically reduced serum GH levels in normal animals but had only a weak effect in the athymic mice. We conclude that congenital athymia in the mouse is associated with decreased basal levels of serum TSH and GH in the presence of a normal somatotroph and thyrotroph morphology. The anomalous responses of athymic mice to stress do not appear to be due to primary hypopituitarism but rather, to an altered modulation of pituitary hormone secretion.

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          Author and article information

          Journal
          Brain Behav Immun
          Brain, behavior, and immunity
          Elsevier BV
          0889-1591
          0889-1591
          Jun 1995
          : 9
          : 2
          Affiliations
          [1 ] Department of Histology and Embryology, School of Medicine, National University of La Plata, Argentina.
          Article
          S0889-1591(85)71009-4
          10.1006/brbi.1995.1009
          7549038
          df0c3a6d-f9ec-4d4c-8415-225d42ca02f6
          History

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