P. P. Krupp

Brain TRH, monoamines, tyrosine hydroxylase, and tryptophan hydroxylase in the woodchuck, Marmota monax, during the hibernation season

Abstract 1. Thyrotropin-releasing hormone (TRH), norepinephrine (NE), epinephrine (E), dopamine (DA), serotonin (5-HT), tyrosine hydrxylase (TH), and tryptophan hydrosylase (TpOH) were measured in several areas of the brains of woodchucks studied prior to, during, and immediately after hibernation. 2. TRH was highest in the hypothalamus. TRH increased markedly in the hypothalamus, septum, and striatum during hibernation, but remained unchanged in the other areas. 3. Hypothalamic NE and E were significantly decreased during hibernation, and DA and NE in the spring. No changes in 5-HT were detected. 4. During hibernation midbrain TH activity decreased, while TpOH increased in striatum and brainstem. 5. These results suggest that TRH and the neurotransmitters may play a role in the mechanism of hibernation.

The effects of dietary iodine on thyroid ultrastructure

This is a morphological study of changes in thyroid cells following iodine deficiency and iodine excess. Fifteen young male Sprague-Dawley rats were divided into three groups and fed one of the following diets for 6 weeks: low iodine (LID), normal iodine (NID) and high iodine (HID). Then the thyroid glands were removed and processed for light and electron microscopy. Thyroid tissue from the NID group was normal in appearance. The most outstanding feature of HID thyroids was the presence of numerous cells which contained irregularly shaped and stained lysosomes. These displaced other cell organelles and caused the apical cell surfaces to project into the follicle lumen. Thyroids from the LID group were three times heavier than the other two groups. Their follicles were very small, contained very little colloid. They were surrounded by dilated capillaries. Mitoses were frequent. Cells were columnar and contained abundant dilated endoplasmic reticulum, numerous apical vesicles, long microvilli and many mitochondria. Mitochondria were especially abundant in greatly infolded lateral and basal cell membranes. These findings show that there is a redistribution of organelles in thyroid cells in response to iodine deficiency and iodine excess which can be related to alterations in intracellular iodine metabolism.

Intranuclear rodlets in woodchuck thyroid follicular cells

SummaryIntranuclear rodlets are seen in thyroid follicular cells of woodchucks fixed during summer and fall. They are not observed in winter and spring animals. A functional significance of these structures is suggested.

The parathyroid gland of the woodchuck (Marmota monax): A study of seasonal variations in the chief cells

The ultrastructure of the parathyroid chief cell in the woodchuck, Marmota monax, was studied during the four seasons of the year. Spring chief cells have stacks of granular endoplasmic reticulum, prominent multiple Golgi zones and many clumped mitochondria. Summer cells resemble those seen in the spring but the mitochondria are associated with stacks of granular endoplasmic reticulum. Multiple areas of stacked granular endoplasmic reticulum characterize the fall chief cells. Their Golgi zones are large and are associated with many dense core secretory granules. Lipoid vacuoles are frequently noted. Winter chief cells have secretory granules and phagolysosomes (dense bodies). Some of these cells contain stacked arrays of granular endoplasmic reticulum associated with mitochondria, others have only short segments. The above morphological findings are discussed in relation to those in other hibernators, the parafollicular (C) cell, and to the cyclic seasonal activities of the woodchuck.

Effects of vitamin a deficiency on ultimobranchial cysts in the thyroid gland

SummaryUltimobranchial cysts in the thyroid glands of rats receiving a diet adequate in vitamin A are lined with stratified squamous epithelium and contain non-keratinized cellular debris. The epithelium of these cysts in vitamin A deficient animals is keratinized, and their lumina contain keratinized cellular strands surrounding a core of cellular debris. Upon return to a diet adequate in vitamin A the epithelium returns to a non-keratinized state, and the lumina contain keratinized strands surrounded by cell fragments and desquamated whole cells. Occasionally these cysts have an epithelium that is highly irregular in appearance. The relationship of alterations in this tisssue to possible subsequent development of neoplasias is discussed.