Development of the independent function of fetal thyroid glands in the dog in connection with iodothyronine concentrations in pregnant bitches, fetal fluids, and fetal serum.

Thyroxine (T4) and triiodothyronine (T3) concentrations in pregnant and nonpregnant bitches were measured. The allantoic and amniotic fluid samples were collected separately in the third week of pregnancy, and fetal blood samples were collected in the fourth week of pregnancy. There was no difference between T4 results in the pregnant and nonpregnant animals, but the measured serum concentrations exceeded the healthy range for normal adults. Serum T4 concentrations were lower in the fetus than those in adults (P < 0.01). Fetal T4 concentrations continuously increased and reached 13.38 ± 6.19 nmol/L before birth. The fetal serum T4 concentrations were lower than the T4 concentrations in allantoic and amniotic fluid until the seventh week, and the fetal serum T3 concentrations were lower than those in fetal fluids throughout the pregnancy (P < 0.01). Maximum T3 concentrations in allantoic and amniotic fluid exceeded the concentrations in the fetal and maternal serum. It is conceivable that the considerable differences between maternal and fetal serum T4 concentrations in healthy animals are explained by the T4 impermeability of the placenta. Extremely high maternal T4 (193.5 nmol/L) in 1 bitch was associated with T4 concentrations under the detection limit in the fetal fluids and serum suggesting an inhibitory effect. The T4 concentrations in all the fetal fluids and serum were under the detectable concentration that can be defined by 3.0 nmol/L in that bitch. We have demonstrated that fetal thyroid glands start functioning independently at the same time as thyroid cell formation in the dog, but the overproduction of maternal T4 may have a suppressive effect on fetal iodothyronine production.

Expression pattern of markers in the canine ovarian cycle.

Although hormonal changes during different phases of the oestrous cycle of bitches are well-described, knowledge about the luteal phase and anoestrus is incomplete. Furthermore, which paracrine and autocrine critical factors that differentiate between follicles destined for atresia and those that continue to develop are unknown. In this study, ovarian tissue was collected from 39 healthy bitches that were subject to ovariectomy or ovariohysterectomy for surgical neutering or medical purposes such as unwanted pregnancy. Bitches were allocated to different groups depending on the stage of the oestrous cycle. Serum progesterone, LH, FSH and 17beta-estradiol (E(2)) -levels were determined and immunhistochemistry was performed for a variety of receptor antigens; Ki-67, vimentin, pan cytokeratin antibody, p53 and oestrogen receptor (ER) alpha antigens. Marked differences were found in progesterone concentration between pregnant and non-pregnant animals. Oestrogen concentration was significantly lower in pro-oestrus and ovulation than during the luteal phase. Although progesterone could be detected in cytoplasm of ovarian cells at each stage, its presence was restricted to follicular cells during anoestrus. A strong presence of AE1/AE3, vimentin and p53 was found in each oestrous stage, in contrast with Ki67. The localization of ERalpha appeared to vary during the oestrous cycle, a phenomenon that suggests a switch between target cells of oestrogen; while as a proliferation marker, the mild reaction of p53 during parturition suggests an apoptotic process at this stage of the cycle.

Progesterone, oestradiol, FSH and LH concentrations in serum of progesterone-treated pregnant bitches with suspected luteal insufficiency.

In the bitch, the corpus luteum is the only source of circulating progesterone throughout pregnancy. Inadequate luteal function may be a cause of abortion or foetal resorption observed after early pregnancy diagnosis. In our study of factors involved in canine luteal inadequacy, 35 pregnant bitches from different breeds were allocated to groups of healthy control (n = 15) vs hypoluteoid (n = 20) pregnant bitches, based on presence or absence of clinical signs of impending abortion and on progesterone concentrations below 10 ng/ml at the 4th-5th week of pregnancy. Hypoluteoid bitches were treated daily with 10-mg natural progesterone in injectable form (Luteosan inj.; Alvetra and Werfft AG, Vienna, Austria) until day 60. Serum progesterone, 17beta-oestradiol, FSH and LH concentrations were measured in samples obtained weekly using ELISA previously validated for dog serum. The exogenous progesterone supplementation was presumed to be sufficient to prevent foetal loss in 15 of the 20 treated bitches. The mean serum progesterone concentration in control pregnant bitches did not decrease below 10 ng/ml until the 8th week of pregnancy. Progesterone concentrations in progesterone-treated hypoluteoid bitches at week 4 were lower than in controls (p < 0.05), but although numerically higher did not differ significantly from those of controls during the period of treatment. Serum 17beta-oestradiol concentrations of healthy bitches were variable, were at most time higher than those of treated animals and slowly decreased until parturition; those of treated bitches remained unchanged during the study. Serum FSH and LH concentrations did not differ between groups. Additional studies involving untreated pregnancies showing equivalent evidence of hypoluteoidism as well as assay of circulating relaxin and prolactin in treated and untreated bitches are needed to better determine the causes and effects of hypoluteoidism in pregnant bitches.

Follicular development and plasma concentrations of LH and prolactin in anestrous female dogs treated with the dopamine agonist cabergoline.

The effect of a daily administration of a dopamine agonist (cabergoline, 5 microg/kg) for 4 weeks, starting about 95 days after the end of estrus on follicular development and its relationship with LH and prolactin secretion has been investigated in two groups of anestrous bitches (Beagles and Greyhounds). Pro-estrus was detected in 80% (8/10) of beagles and 50% (3/6) of treated greyhounds. The mean inter-estrus interval of treated animals was 132+/-5.0 and 169+/-7.0 days for beagles and greyhounds, respectively, and in both this differed significantly from the cycle preceding treatment (192+/-9.0 and 198+/-12.0 days) and from that in untreated bitches (194+/-11.0 and 196+/-11.0 days for beagles and greyhounds, respectively (all comparisons at P<0.001). The interval from the beginning of treatment to pro-estrus in responding animals was 13.3+/-1.90 days in beagles and 20.3+/-1.70 days in greyhounds. Cabergoline increased (P<0.001) the length of pro-estrus (10.6+/-0.50 and 11.7+/-0.50 days) in the treated estrus cycle compared to the previous estrus cycle (8.4+/-0.30 and 8.8+/-0.40 days for in beagles and greyhound, respectively). Ovarian enlargement and follicle development was detected by ultrasound in 90% of treated beagles and in 83% of greyhound between the second and third weeks of treatment, but only 80% of beagles and 66% of treated greyhound displayed pro-estrus and estrus. In the treated bitches, mean plasma LH increased (P<0.001) before pro-estrus. There was high variability in mean plasma prolactin levels between animals. These data indicate that the administration of the dopamine agonist cabergoline to anestrous bitches increases mean LH plasma levels and induces follicular development shortly before pro-estrus but this activity is not always followed by pro-estrus and estrus. Finally, prolactin per se does not have a prominent role in the control of folliculogenesis in the bitch.

Immunohistochemical detection of progesterone and cellular proliferation in canine mammary tumours.

Immunohistochemical expression of progesterone and the cellular proliferation marker Ki-67 was assessed in formalin-fixed, paraffin wax-embedded samples from 43 canine mammary tumours. Benign tumours showed high surface membrane progesterone expression (mean 196.42+/-25.91 positively labelled cells per 500 tumour cells) and low cellular proliferation (52.14+/-16.73 positively labelled cells per 500 tumour cells), whilst malignant tumours had low progesterone expression (68.19+/-17.53 positively labelled cells per 500 tumour cells) and higher cellular proliferation (141.72+/-23.65 positively labelled cells per 500 tumour cells), the difference being statistically significant (P<0.005) in both cases. These findings suggest that the majority of progesterone receptors in canine mammary tumour tissue are not associated with bound progesterone. The progression towards malignancy in spontaneously arising canine mammary tumours therefore appears to be associated with a decrease in steroid hormone dependency. Progesterone expression was also noted in the cytoplasm of tumour cells where it may be associated with a cellular repair mechanism. This hypothesis is supported by the finding of significantly higher progesterone content in the cytoplasm of benign tumour cells.

Effect of anticoagulants and sampling time on results of progesterone determination in canine blood samples.

The concentration of plasma progesterone was measured by ELISA, in serum and samples prepared with three different anticoagulant agents - namely ethylenediaminetetraacetic acid (EDTA), heparine and sodium fluoride oxalate potassium(NaFK). Forty clinically healthy bitches were selected based on the signs of pro-oestrus or oestrus. Values of progesterone concentration were significantly higher in serum than in EDTA-plasma (p < 0.0005); heparin-plasma (p < 0.05) and NaFK-plasma (p < 0.005). During pro-oestrus and oestrus until the time of ovulation, progesterone exhibited a conspicuous and statistically verified diurnal pattern (p < 0.05), its serum concentration being higher during 6.00-7.00 p.m. than 8.00-9.00 a.m. By the time of ovulation tendency of higher p.m. progesterone level reverses and from this point on the a.m. progesterone concentration is higher. The results of these experiments indicate that the concentration of canine progesterone assayed with ELISA may be affected by the time of collection and the method of preservation used.

Oncological scintigraphy in dogs with 99mTechnetium MIBI and DMSA(V)--two case reports.

Oncological scintigraphy is described in two dogs with malignant lymphoma and malignant schwannoma, respectively. The distribution of the radiopharmaceuticals could be visualized for the purpose of detection of neoplasia and eventual metastases, and to evaluate the effectivity of therapy. It is concluded that 99mTechnetium MIBI and 99mTc DMSA (V) scintigraphy is useful for the detection of soft tissue malignancy in dogs.

Thyroid volumetric measurement and quantitative thyroid scintigraphy in dogs.

Thyroid volumetric measurement combined with quantitative 99mTc-per-technetate thyroid scintigraphy was performed in 62 clinical canine patients having suspected thyroid abnormalities. Euthyroid dogs (n = 22) had a total thyroid size of 3.60 +/- 1.36 cm3, the thyroid/salivary gland region of interest (ROI) ratio was 2.01 +/- 0.55, the thyroid/background ROI ratio was 3.86 +/- 0.90, and 20-min thyroid radioactivity uptake was 1.17 +/- 0.71% of the injected dose (I. D.). By Student's unpaired test, thyroid size of the hypothyroid group (n = 36) was not statistically different from that of the euthyroid dogs, but all other quantitative data (e.g., thyroid/salivary gland ROI ratio = 1.08 +/- 0.56, thyroid/background ROI ratio = 2.32 +/- 0.70, and 20-min thyroid radioactivity uptake = 0.34 +/- 0.22% of the I. D.) were significantly (p < 0.001) lower in hypothyroid than in euthyroid dogs. Evaluating the above-listed quantitative data of separated thyroid lobes by Student's paired test, there was no significant difference between the left and the right lobe either in the euthyroid or in the hypothyroid group.

Diagnosis of hyperadrenocorticism in dogs as compared to human diagnostic methods: a review.

Spontaneous hyperadrenocorticism is a common and well-recognised endocrine disorder occurring in dogs. The biochemical diagnosis of hyperadrenocorticism rests on the documentation of excessive glucocorticoid levels or metabolites in urine or blood. The diagnosis of canine hyperadrenocorticism is historically developed from human methods and based on non-dynamic and dynamic tests and visualisation. In some cases the different ranges of endocrine parameters or metabolites necessitate the modification of human protocols. Elevation of the activity of alkaline phosphatase (AP) and its heat-resistant isoenzyme (SIAP) induced by endogenous or exogenous glucocorticoid excess raise the suspicion of hyperadrenocorticism. Cortisol values in morning urine are related to creatinine concentrations to correct for differences in urine concentration. Theoretically, the administration of dexamethasone (DX) at a relatively low dose (0.01 mg/kg of body weight) can inhibit the pituitary secretion of ACTH and, in turn, decrease endogenous cortisol secretion for as long as 24 to 48 h. Therefore, DX administration to dogs with a functioning adrenocortical tumour would not affect the plasma cortisol concentration at any time following its administration. The high-dose dexamethasone suppression test (HDDS) is based on the observation that the function of adrenocortical tumours is independent of pituitary ACTH and they completely suppress ACTH secretion; therefore, regardless of its dose, dexamethasone is never able to suppress cortisol secretion. HDDS can be combined with the measurement of urinary cortisol/creatinine (c/c) ratio from morning urine samples on three consecutive days. In case of non-suppressible urinary c/c ratio one has to speculate on differentiating adrenal tumour (AT) from non-suppressible pituitary-dependent hyperadrenocorticism (PDH) due to a pituitary tumour arising from the intermediate lobe. Radiocholesterol scintigraphy is a less frequently used technique in the diagnosis of canine Cushing's syndrome (CCS); however, it has the same advantages in the localisation and characterisation of adrenocortical diseases as in humans.

Multiple endocrine neoplasias in a dog: corticotrophic tumour, bilateral adrenocortical tumours, and pheochromocytoma.

In a 10-year-old ovariohysterectomized standard Schnauzer, the finding of dexamethasone-resistant hypersecretion of cortisol, the results of computed tomography, and elevated plasma concentrations of ACTH suggested the presence of both adrenocortical tumour and pituitary-dependent hyperadrenocorticism. The dog made an uneventful recovery after bilateral adrenalectomy and remained in good health for 31/2 years with substitution for the induced hypoadrenocorticism. Then the enlarged pituitary caused neurological signs and eventually euthanasia was performed. The surgically excised right adrenal contained a well-circumscribed tumour of differentiated adrenocortical tissue and in the left adrenal there were two adrenocortical tumours and a pheochromocytoma. The unaffected parts of the adrenal cortices were well developed and without regressive transformation. At necropsy there were no metastatic lesions. The cells of the pituitary tumour were immunopositive for ACTH and had characteristics of malignancy. The present combination of corticotrophic tumour, adrenocortical tumours, and pheochromocytoma may be called 'multiple endocrine neoplasia' (MEN), but does not correspond to the inherited combinations of diseases known in humans as the MEN-1 and the MEN-2 syndromes. It is suggested that the co-existence of hyperadrenocorticism and pheochromocytoma may be related to the vascular supply of the adrenals. Some chromaffin cells of the adrenal medulla are directly exposed to cortical venous blood, and intra-adrenal cortisol is known to stimulate catecholamine synthesis and may promote adrenal medullary hyperplasia or neoplasia.