No abstract

SUMMARY. An ulcerated lesion resembling a tumour in the lesser curvature of the stomach of a 3-year-old male Dobermann pinscher was found to be caused by Cryptococcus neoformans. The dog had been vomiting for two months and had slight leucocytosis and anaemia. Biopsies of the ulcerated lesion revealed granulomatous inflammation and many cryptococci, which were particularly prominent in PAS and mucicarmine stained sections. No other lesions were found at necropsy.

Various aspects of iodine metabolism were studied in adult beagles maintained at iodine intake levels ranging from 480 to 20 mug/day. On the basis of changes in radioiodine metabolism, the minimum daily iodine requirement of the adult beagle was found to be 140 mug. Although striking changes were observed in radioiodine metabolism when iodine intake was reduced to 90mug/day, serum T4 and T3 levels were unaffected. Marked reductions in serum T4 occurred in dogs restricted to an iodine intake of 50 or 20 mug/day, but even at these low levels of iodine intake there were only slight reductions in serum T3 concentration and a eumetabolic state was maintained. Prolonged iodine deficiency (8-12 months) resulted in variable patterns of thyroid histology, which were related to differences in thyroidal 127I content and in the rate of release of radioiodine from the thyroid. The heterogeneity in thyroid morphology and iodine kinetics did not, however, have a significant effect on serum T4 and T3 levels.

A study was made of the concentration and cellular localization of serotonin in the thyroid gland of the dog. This species is characterized by a low level of serotonin in the adult thyroid gland. Endogenous serotonin consequently cannot be demonstrated by fluorescence microscopy following treatment of frozen‐dried adult thyroid tissue with formaldehyde vapor. In contrast, the thyroid concentration of serotonin was found to be high, in both beagle and basenji (purebred dogs of European or African origin respectively), around the time of birth. The serotonin concentration then fell rapidly as development of the animals proceeded. This pattern also seemed true of the rabbit. When the concentration of serotonin was high, just prior to birth, a yellow fluorophore, probably the condensation product formed between serotonin and formaldehyde could, as in other species, be demonstrated in parafollicular cells after exposure of tissue to formaldehyde gas. Thyroid follicular cells never showed serotonin but instead, a striking accumulation of autofluorescent apical dense bodies (0.3–1.0 μ in diameter), probably lysosomes, occurred during the first year of life.