Thyrotrophin receptors in normal and neoplastic (primary and metastatic) canine thyroid tissue.

Thyrotrophin (TSH) is the conditional growth factor of thyroid epithelial cells. Abnormalities in TSH-receptor binding such as a low receptor number or low binding affinity may be a marker of thyroid carcinoma or metastases, or may exhibit a relationship with the functional variability of such tissues. The dog was used as a model to characterize TSH-receptor binding in normal thyroid tissues, naturally occurring thyroid neoplasms and distant metastases. In normal dog thyroid tissues, specific 125I-labelled TSH binding ranged from 2.7 to 15.5%, and low cross-reactivity with bovine LH (0.023%) was observed. One class of TSH-binding sites was found in eight normal thyroid tissues and 22 thyroid carcinomas; two normal thyroid tissues and one tumour exhibited two classes of binding sites. The concentration of binding sites was lower in the five carcinomas with reduced pertechnetate uptake (0.09 pmol/mg protein) than in the five thyroid neoplasms with increased uptake (0.19 pmol/mg) (P = 0.055). Compared with the original carcinoma tissues, TSH binding revealed a reduced binding affinity in eight out of eleven metastases. Two metastases showed a complete absence of TSH binding, suggesting that they were not dependent on TSH for growth. We conclude that one class of TSH-binding site is predominant in normal dog thyroid tissues and dog thyroid carcinomas. TSH could therefore contribute, at least in theory, to further growth of primary dog thyroid carcinomas. Secondly, assays measuring TSH binding may not be able to discriminate between malignant and benign dog thyroid tumours. TSH receptor number or affinity may be related to the functional variability of thyroid neoplasms.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of and radioimmunoassay for canine thyroglobulin.

Canine thyroglobulin (cTg) has been isolated and purified. It has similar electrophoretic patterns as Tg from other mammalian species. The main fraction had a MW of 660,000, whereas also fractions of a MW of approximately 1,300,000 (dimer) and 330,000 (subunit) were present. The iodine content was 0.8 to 1.0% (w/w). cTg did not cross-react with antibodies against human Tg to a degree that would allow the use of a radioimmunoassay for human Tg for the determination of cTg in serum or plasma. Therefore a polyclonal antiserum was raised against cTg and a homologous radioimmunoassay was developed, which was sensitive (0.4 micrograms/l) and specific (cross-reactivity in cTg assay of human Tg, goat Tg, T4, T3, and DIT less than 0.01%). Plasma Tg levels in normal dogs of both sexes and aged 3-15 years amounted to 192 +/- 73 micrograms/l (mean +/- SD, n = 30). There was no relation between plasma Tg and T4 levels.

Circulating thyroglobulin measurements by homologous radioimmunoassay in dogs with thyroid carcinoma.

Circulating thyroglobulin was measured in 20 dogs with thyroid cancer, using a homologous polyclonal radioimmunoassay. Plasma Tg levels exceeded the normal range in 14 (70%) dogs, and ranged from 6 to 2902 micrograms/l (median 608). Plasma Tg levels tended to decrease from follicular carcinomas to solid-follicular carcinomas, to solid carcinomas (p less than 0.05). Plasma Tg levels were also higher in scintigraphically hot tumours than in cold ones. Other relationships between circulating Tg and clinical, pathological, and functional parameters were not found, except a poor (R = 0.49) but significant (p = 0.04) correlation between Tg and T4 levels. Plasma Tg was measured before surgery and at least once during follow-up, in 9 dogs. After hemithyroidectomy, a decrease was observed in 8 dogs. In 7 of these 8 dogs, plasma Tg levels declined within the reference range at the first postoperative sample. In the ninth dog, where metastases were detected 14 months after surgical treatment, plasma Tg slightly increased, yet within normal range. It is concluded that measurement of plasma Tg levels might be useful for monitoring the postoperative course of the disease in individual dogs with thyroid cancer.

Flow-cytometric DNA ploidy analysis in primary and metastatic canine thyroid carcinomas.

DNA ploidy was measured by flow cytometry in 36 primary malignant thyroid neoplasms (including 6 bilateral tumours which were considered as separate neoplasms) from 30 dogs. In addition, DNA ploidy was determined in local recurrences in 3 dogs, and in 18 metastatic sites from 14 dogs. Aneuploidy was found in 21 of 36 (58%) primary sites. Eighteen of the 21 (86%) aneuploid tumours contained hypodiploid cell populations, with 12 having single hypodiploid peaks, and 6 being multiploid. Three other tumours had single aneuploid peaks with a DNA index (DI) greater than 1.0. The DIs in local recurrences were identical to those in the original neoplasms. Ploidy status (diploid vs. aneuploid) was identical in primary and metastatic sites in 10 out of the 14 dogs. Aneuploidy was more frequent in carcinomas from dogs with distant metastases (78%) than from dogs with less advanced stages of disease (53%), although this difference was not significant. There was no significant correlation between DNA ploidy and histopathological variables. From the strikingly high frequency of hypodiploidy in canine tumours, it is concluded that ploidy evolution in canine neoplasms may differ from that in human tumours.

[Evaluation of blood chemistry using 'dry chemistry' in small animal practice]. / Evaluatie van bloedonderzoek met behulp van 'droge chemie' in de kleine huisdierenpraktijk.

In this paper three different systems for clinical chemistry determinations by the general practitioner are evaluated. The systems, Seralyzer, Kodak Ektachem DT 60 and Reflotron, are based on the use of dry reagent strips in combination with a reflectometer. The principle of reflectometry is discussed briefly. These systems enable the practitioner to carry out the majority of the common chemical laboratory blood tests quickly and with an acceptable degree of confidence. The present possibilities are given for each system, including the costs of instruments and tests in the Netherlands. The results of some common tests in small animal medicine have been compared with standard methods in our own laboratory. Since in a few tests species dependent differences were found, it is recommended that each dry chemistry test should be carefully evaluated for each animal species.