Baseline corticosterone is associated with parental care in virgin Japanese quail (Coturnix japonica).

Glucocorticoids (GCs) are thought to impact reproductive success, and ultimately fitness. In this study we focus specifically on the relationship between GCs and parental care. Captive bred Japanese quail (Coturnix japonica) do not show spontaneous parental care behavior, however this behavior can be induced through a sensitization procedure. We investigated how the GC status of Japanese quail relates to parental care in animals of both sexes exposed or not to a chick sensitization treatment. To assess GC status, we obtained baseline plasma and feather cort samples, and used the HPA-axis function test to assess stress responsiveness by examining the response to a standardized stressor as well as negative feedback efficacy through dexamethasone injection. Next, birds were either exposed to chicks overnight in a small enclosure (sensitization treatment) or were enclosed but not exposed to chicks (control). The following morning, adult behaviors were filmed in the presence of a fresh set of chicks for 20 min. A final serum GC sample was obtained to assess if exposure to novel chicks was perceived as stressful. In control animals, baseline GCs were associated with increased total parental care duration and decreased latency to first parental care event. Interestingly, the opposite relationship was found in the sensitization group. Finally, exposure to novel chicks was not associated with an increase in corticosterone in either group. Overall it appears that baseline GCs are correlated with parental care in captive bred Japanese quail, and that the relationship changes direction depending on whether or not sensitization has occurred.

Canine hypophysectomy using a ventral paramedian approach.

OBJECTIVE: To evaluate the degree of pituitary exposure, completeness of hypophysectomy, and perioperative morbidity associated with an alternative paramedian surgical approach and excisional technique for the canine pituitary gland. STUDY DESIGN: Experimental imaging, surgical, and endocrinologic study. ANIMAL POPULATION: Nine healthy, purpose-bred Beagle dogs. METHODS: Surgical landmarks for the pituitary were determined by computed tomography (CT), and then using a ventral paramedian approach medial to the rami of the mandible, the pituitary was exposed and removed en bloc by manipulation and ultrasonic aspiration. Efficacy of the procedure was evaluated using endocrinologic and pathologic observation. RESULTS: CT images allowed the precise location of surgical landmarks for hypophysectomy. Statistically significant decreases in secretion of all measured pituitary hormones except adrenocorticotropic hormone (ACTH) occurred after hypophysectomy. Despite the absence of gross evidence of residual pituitary tissue, immunohistochemical staining revealed residual pituitary cells in the sella turcica of most dogs. CONCLUSION: CT imaging and a paramedian approach facilitated surgical access to the pituitary gland by a transoral technique; however, use of an ultrasonic aspirator removed all visible pituitary glands but left cellular remnants capable of ACTH secretion in the sella turcica. CLINICAL RELEVANCE: Although this technique did not result in complete hypophysectomy, clinical use in dogs with pituitary-dependent hyperadrenocorticism is warranted because the goal is not complete hypophysectomy but removal of a pituitary tumor.

Transsphenoidal hypophysectomy for treatment of pituitary-dependent hyperadrenocorticism in 7 cats.

OBJECTIVE: Evaluation of microsurgical transsphenoidal hypophysectomy for the treatment of pituitary-dependent hyperadrenocorticism (PDH) in cats. STUDY DESIGN: Prospective clinical study. ANIMALS OR SAMPLE POPULATION: Seven cats with PDH. METHODS: Urinary cortisol/creatinine ratios, pituitary-adrenocortical function tests, and computed tomography (CT) were performed on 7 cats that presented with a provisional diagnosis of hyperadrenocorticism. All cats underwent microsurgical transsphenoidal hypophysectomy with histologic examination of the excised specimen. Follow-up consisted of clinical evaluation, repeat adrenocortical function testing, and CT. RESULTS: Four cats had concurrent diabetes mellitus. In all cats, the urinary cortisol/creatinine (C/C) ratios were elevated. The dexamethasone screening test showed that 2 cats did not meet the criterion for hyperadrenocorticism. The response of the cats' plasma concentrations of cortisol and adrenocorticotrophic hormone to a high dose of dexamethasone varied from very sensitive to completely dexamethasone resistant. Basal plasma alpha-melanocyte-stimulating hormone concentrations were elevated in 2 cats with a pars intermedia adenoma and in 3 cats with an adenoma that originated from the anterior lobe. Preoperative CT enabled accurate assessment of pituitary size (5 nonenlarged pituitaries with a height <4 mm and 2 enlarged pituitaries with a height >5 mm) and localization relative to intraoperative anatomic landmarks. Two cats died within 4 weeks after surgery of a nonrelated disease. In the remaining 5 cats, the hyperadrenocorticism went into both clinical and biochemical remission. Hyperadrenocorticism recurred in 1 cat after 19 months, but no other therapy was given and the cat died at home 28 months after surgery. CT evaluation of this cat had identified pituitary remnants 6 weeks after surgery. The main postoperative complications were oronasal fistula (1 cat), complete dehiscence of the soft palate (1 cat), and transient reduction of tear production (1 cat). One cat died at 6 months (undefined anemia), and another cat at 8 months (recurrent nose and middle ear infection secondary to soft palate dehiscence) after surgery. In the surviving 2 cats, the remission periods at the time of writing were 46 and 15 months. In the 2 cats with sufficient follow-up time, the concurrent diabetes mellitus disappeared, ie, insulin treatment could be discontinued at 4 weeks and 5 months after hypophysectomy. In all 7 cats, the histologic diagnosis was pituitary adenoma. CONCLUSIONS: Microsurgical transsphenoidal hypophysectomy is an effective method of treatment for feline PDH in specialized veterinary institutions having access to advanced pituitary imaging techniques. Concurrent diabetes mellitus is usually reversible after hypophysectomy. Thorough presurgical screening for coexisting diseases is imperative. CLINICAL RELEVANCE: PDH in cats can be effectively treated by hypophysectomy. The neurosurgeon performing hypophysectomy must master a learning curve and must be familiar with the most frequent complications of the operation to treat them immediately and effectively. Urinary C/C ratios are sensitive indicators for the assessment of remission and recurrence of hyperadrenocorticism.

Combined pituitary hormone deficiency in german shepherd dogs with dwarfism.

In German shepherd dogs pituitary dwarfism is known as an autosomal recessive inherited abnormality. To investigate whether the function of cells other than the somatotropes may also be impaired in this disease, the secretory capacity of the pituitary anterior lobe (AL) cells was studied by a combined pituitary AL stimulation test with four releasing hormones (4RH test) in four male and four female German shepherd dwarfs. In addition, the morphology of the pituitary was investigated by computed tomography. The physical features of the eight German shepherd dwarfs were primarily characterized by growth retardation and stagnant development of the hair coat. The results of the 4RH test confirmed the presence of hyposomatotropism. The basal plasma TSH and prolactin concentrations were also low and did not change upon stimulation. Basal plasma concentrations of LH were relatively low and responded only slightly to suprapituitary stimulation. With respect to the plasma FSH levels there was a clear gender difference. In the males plasma FSH concentrations remained below the detection limit throughout the 4RH test, whereas in the females the basal plasma FSH levels were slightly lower and there was only a small increase following suprapituitary stimulation, compared with the values in age-matched controls. In contrast, basal and stimulated plasma ACTH concentrations did not differ between the dwarfs and the controls. Computed tomography of the pituitary fossa revealed a normal sized pituitary with cysts in five dogs, an enlarged pituitary with cysts in two dogs, and a small pituitary gland without cysts in the remaining dog. The results of this study demonstrate that German shepherd dwarfs have a combined deficiency of GH, TSH, and prolactin together with impaired release of gonadotropins, whereas ACTH secretion is preserved. The combined pituitary hormone deficiency is associated with cyst formation and pituitary hypoplasia.

Transsphenoidal hypophysectomy in beagle dogs: evaluation of a microsurgical technique.

OBJECTIVE: Assessment of a microsurgical technique for transsphenoidal hypophysectomy in dogs. STUDY DESIGN: Prospective study using physical examination, pituitary function testing, computed tomography (CT), and histological examination at autopsy. ANIMALS OR SAMPLE POPULATION: Eight laboratory beagle dogs. METHODS: Pituitary function was assessed before and at 10 weeks after hypophysectomy by combined administration of four releasing hormones (anterior pituitary), administration of haloperidol (pars intermedia), and infusion of hypertonic saline (posterior pituitary). RESULTS: CT imaging enabled accurate preoperative localization of the pituitary. Appropriate positioning and surgical technique facilitated exposure of the pituitary and its extraction without hemorrhage. Postoperative recovery was generally uncomplicated. None of the eight dogs had somatotropic, gonadotropic, lactotropic, melanotropic, or posterior pituitary responses to stimulation at 10 weeks after hypophysectomy. Four dogs (ACTH nonresponders) also had no corticotropic response and four (ACTH responders) had small but significant responses in the combined anterior pituitary function test. Adrenocortical atrophy was more pronounced in the ACTH nonresponders than in the responders. No residual pituitary tissue was found along the ventral hypothalamic diencephalon but nests of pituitary cells were found embedded in fibrous tissue in the sella turcica. CONCLUSIONS: The surgical technique proved to be safe and effective. Microscopic nests of pituitary cells in the sella turcica may be responsible for residual corticotropic response to hypophysiotropic stimulation after hypophysectomy. CLINICAL RELEVANCE: The surgical technique may be used in the treatment of dogs with pituitary-dependent hyperadrenocorticism. The corticotropic response is the most sensitive criterion in assessing completeness of hypophysectomy in dogs.

Diagnostic testing for pituitary pars intermedia dysfunction in horses.

Pituitary pars intermedia dysfunction is a slowly progressive disorder that afflicts most breeds of horses. Because it shares features with human Cushing disease, it has been referred to as equine Cushing disease. A variety of tests of pituitary-adrenocortical function were performed on horses with evidence of pituitary pars intermediate dysfunction, and results were compared with those in healthy control horses. Diurnal variations in plasma cortisol concentration were not statistically different between control horses and those with pituitary pars intermedia dysfunction. An ACTH stimulation (1 U of natural ACTH gel/kg of body weight, IM) test or a combined dexamethasone suppression test (10 mg, IM) and ACTH stimulation (100 mg of synthetic ACTH, IV) test also failed to distinguish horses with pituitary pars intermedia dysfunction from control horses. A significant (P < 0.001) dose-related suppression of cortisol concentration in response to increasing doses (5, 10, 20, and 40 micrograms/kg) of dexamethasone was observed in control horses but not in those with pituitary pars intermedia dysfunction. On the basis of plasma cortisol concentration, the dexamethasone suppression test, using 40 micrograms/kg, whether initiated at 5 PM with sample collection at 15 (8 AM) and 19 (12 PM) hours after dexamethasone administration, or initiated at 12 AM with sample collection at 8 (8 AM), 12 (12 PM), 16 (4 PM), 20 (8 PM), and 24 (12 AM) hours after dexamethasone administration, reliably distinguished between control horses and those with pituitary pars intermedia dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Metyrapone and adrenal response in stressed calves.

The effects on some hematochemical stress indices of previously administered metyrapone (750 mg given orally six times every 4 hours) were evaluated in calves submitted to simulated transport for 30 min. The plasma cortisol increases were significantly lower than those observed in untreated calves of the same age, sex and breed. Plasma adrenaline and NEFA increased similarly in both groups of calves during simulated transport and were unaffected by metyrapone administration. The results indicate that in cattle, as in other animals, metyrapone inhibits cortisol biosynthesis. Under our experimental conditions, the rise of NEFA, a well known stress index, seems mainly to be related to adrenaline release.

Canine pituitary-testicular function in relation to toxicity testing.

The physiological onset and establishment of adult pituitary-testicular function has been characterised for Beagle dogs. Testicular measurements, circulating prolactin, luteinising hormone and testosterone concentrations, semen analyses and the histological appearance of testicular biopsies, suggest that male Beagles attain sexual maturity between 35 and 41 weeks of age. The assessment of testicular toxicity is discussed and attention drawn to possible approaches for investigating primary mechanisms of toxic action on the canine testis. Expected values for testicular size, hormone levels and semen characteristics are reported.