The effects of thyroid hormones on the skin of beagle dogs

The effects of hypothyroidism on canine skin were determined by comparing morphologic, morphometric, and hair cycle differences in skin biopsy samples from 3 groups of age- and gender-matched Beagle dogs: (1) euthyroid dogs; (2) dogs made hypothyroid by administration of 131I; and (3) dogs made hypothyroid and maintained in a euthyroid state by treatment with synthetic thyroxine. After 10 months of observation, there was slower regrowth of hair 2 months after clipping in the untreated-hypothyroid dogs. Untreated-hypothyroid dogs had a greater number of follicles in telogen and fewer hair shafts (ie, a greater number of hairless telogen follicles) than did the control group. The control dogs had a greater number of telogen follicles but the same number of hair shafts as the treated-hypothyroid group. Treated-hypothyroid dogs had the greatest number of follicles in the growing stage of the hair cycle (anagen). This study suggests that, at least in Beagles, induced hypothyroidism does not affect the pelage as dramatically as has been described in naturally occurring disease. This is because normal Beagles retain hair shafts in follicles for long periods, and the alopecia of hypothyroidism appears to evolve slowly because of the prolongation of this haired telogen stage. The evaluation of thyroxine-treated hypothyroid dogs demonstrates that thyroid hormone supplementation of Beagle dogs with induced hypothyroidism stimulates hair growth.     

Effects of topical administration of timolol maleate on intraocular pressure and pupil size in dogs

Effects of topical administration of a single dose of timolol maleate on intraocular pressure (IOP) and pupil diameter were evaluated in normotensive eyes of 11 clinically normal dogs over 12 hours (7:00 AM to 7:00 PM). Mean (+/- SEM) normal IOP was 15.5 (+/- 1.1) mm of Hg and diurnal fluctuation was observed, with the highest IOP seen in the morning. Mean normal pupil diameter was 8.5 (+/- 0.3) mm. Topical treatment with 0.5% timolol resulted in reduction of IOP in the treated and nontreated eyes. Mean reduction of IOP in the treated eye was 2.5 mm of Hg, a reduction of 16.1%, with maximal reduction of 3.7 mm of Hg. Mean reduction of IOP in the nontreated eye was 1.4 mm of Hg, a reduction of 9.0%. The treated eye had reduced pupil diameter at 30 minutes after treatment, which persisted throughout the 12 hours of the study. Mean reduction of pupil diameter in the treated eye was 2.9 mm, a reduction of 34.1%. In addition, a contralateral effect on pupil diameter was seen in the nontreated eye, with mean reduction of 1.2 mm, a reduction of 14.1%. Topical administration of timolol maleate resulted in reduction of IOP and pupil diameter in treated and contralateral eyes, thus supporting the use of timolol for treatment of glaucoma in dogs. Miosis indicates possible beta-adrenergic inhibition or alpha-adrenergic activation of the sphincter muscle. beta-Adrenergic blockade would then result in miosis.     

Mammary tumors in a colony of beagle dogs

In a lifetime study, female beagle dogs in a closed colony were administered 226radium and 90strontium. An unirradiated control group was included in the study. A total of 223 of 356 dogs at risk developed 1,112 mammary proliferative growths (hyperplastic nodules and neoplasms). There was no correlation between occurrence and types of lesions in radiation and control groups. The age range for first occurrence of lesions was 10.4 to 13.9 years; hyperplastic nodule and benign mixed tumor occurred 1 to 2 years earlier than other lesions. A multiplicity of growths of similar or different morphological type were common throughout the lifetime of the dog. The female beagles, collectively, developed 244 hyperplastic nodules, 78 adenomas, 694 benign mixed tumors, 78 carcinomas, 14 malignant mixed tumors, and four myoepitheliomas. Proliferations occurred with increasing frequency from the cranial to caudal mammary glands. Metastasis was found in 77% of the dogs with carcinoma. The median time from diagnosis to metastasis was 10 months, but was shorter in dogs with infiltrative carcinoma.     

Thyroid neoplasms in a colony of beagle dogs

The histologic, clinicopathologic, and epidemiologic features of spontaneous thyroid neoplasms were evaluated in a control population of Beagle dogs. The mean age of thyroid tumor-bearing dogs (16.2 years) as significantly higher than non-tumor-bearing dogs (13.6 years). Thirteen benign and 18 malignant tumors were identified, with the incidence of both tumors increasing rapidly near the mean age of 16.2 years for tumor-bearing dogs. The age-specific incidence of tumors was 1.1% per year at 8 to 12 years, increasing to 4.0% per year by 12 to 15 years and 67% over 17 years of age. Numbers of malignant tumors were greater than benign tumors at an earlier age. Approximately 44% of the malignant tumors metastasized but only 22% resulted in death of the dog. There was no difference in tumor incidence when compared according to sex, if total tumor numbers were considered or if tumors were separated into benign and malignant categories. The age at death of tumor-bearing dogs was not increased significantly by the surgical resection of the thyroid tumors. Of dogs with thyroid tumors, 15% had clinical diagnoses of hypothyroidism, and no dogs with thyroid tumors had diagnoses of hyperthyroidism.     

Cardiac conotruncal malformations in a family of beagle dogs

O bjectives : To study forms of congenital heart disease present in a family of beagle dogs with a strong prevalence of ventricular septal defect and to document the pathological findings associated with the ventricular septal defects and investigate the mode of transmission.
M ethods : The animals were investigated by physical examination, radiography, electrocardiography and ultrasonography to diagnose the presence of congenital heart disease. Some animals were diagnosed at post-mortem examination and the dead animals underwent post-mortem examination to verify the presence of ventricular septal defect. An analysis of pedigree was undertaken and two of the affected animals were mated to investigate the mode of transmission.
R esults : Among the 28 dogs evaluated clinically or by post-mortem examination, 14 cases of ventricular septal defect were identified. The post-mortem examination showed some abnormalities of the ventricular outflow region associated with malformation of conotruncal septum development. When two affected dogs were bred, congenital heart disease was present in all of the offspring.
C linical S ignificance : The congenital heart disease identified in this beagle family can be classified as conotruncal malformation, and an autosomal recessive mode of inheritance was suggested by pedigree analysis.     

Neurohormonal and metabolic effects of medetomidine compared with xylazine in beagle dogs

This study was aimed to investigate and compare the effects of medetomidine and xylazine on the blood level of some stress-related neurohormonal and metabolic variables in clinically normal dogs, especially focusing on time and dose relations of the effects. A total of 9 beagle dogs were used for 9 groups, which were treated with physiological saline solution (control), 10, 20, 40, and 80 μg/kg medetomidine, and 1, 2, 4, and 8 mg/kg xylazine, intramuscularly. Blood samples were taken at 10 times during 24 h from a central venous catheter. Plasma norepinephrine, epinephrine, cortisol, glucose, insulin, glucagon, and non-esterified fatty acid concentrations were determined. Both medetomidine and xylazine similarly and dose-dependently inhibited norepinephrine release and lipolysis. Medetomidine suppressed epinephrine release dose-dependently with greater potency than xylazine. Xylazine also tended to decrease epinephrine levels dose-dependently. The cortisol and glucagon levels did not change significantly in any treatment group. Both drugs suppressed insulin secretion with similar potency. Both medetomidine and xylazine increased glucose levels. The hyperglycemic effect of medetomidine, in contrast with xylazine, was not dose-dependent at the tested dosages. The results suggested that the effect of medetomidine on glucose metabolism may not be due only to α₂-adrenoceptor-mediated actions.     

Effects of topical nipradilol and timolol maleate on intraocular pressure, facility of outflow, arterial blood pressure and pulse rate in dogs

Nipradilol is an alpha(1), beta-blocker with milder side effects than other beta-blockers used in humans. In this study the effects of nipradilol were compared with those of timolol maleate in dogs. Twelve clinically normal dogs (nine mongrels, two beagles, and one Akita) were used. We applied 0.25% nipradilol or 0.5% timolol maleate drops for a period of 28 days. Intraocular pressure (IOP) was measured before and after administration on the 2nd, 4th, 7th, 14th, 21st and 28th day. Blood pressure, pulse rate and coefficient of aqueous outflow (C-value) were also measured before and after administration on the 7th, 14th, 21st and 28th day. Both nipradilol and timolol maleate significantly lowered IOP from the 2nd day to the end of the study period. Nipradilol lowered IOP to an equivalent degree to timolol maleate. There was no significant change in blood pressure and pulse rate throughout the study period with administration of nipradilol. C-value showed a significant rise from the 14th day with administration of nipradilol, while it did not show any significant change during the study period with administration of timolol maleate. The reduction of IOP by nipradilol was similar to that by an existing beta-adrenergic antagonist, timolol maleate, but nipradilol was associated with fewer systemic side effects in dogs. Nipradilol appears to be a useful drug for treatment of glaucoma in dogs.     

Pharmacokinetics of tildipirosin in beagle dogs

The objective of this study was to investigate the pharmacokinetic profile of tildipirosin (TD) in 24 beagle dogs following intravenous (i.v.) and intramuscular (i.m.) administration, respectively, at 2, 4, and 6 mg/kg. Plasma samples at certain time points (0–14 days) were collected, and the concentrations of drug were quantified by UPLC‐MS/MS. Plasma concentration–time data and relevant parameters were described by noncompartmental through WinNonlin 6.4 software. After single i.m. injection at 2, 4, and 6 mg/kg body weight, mean maximum concentration (C_max) was 412.73 ± 76.01, 1,051 ± 323, and 1,061 ± 352 ng/ml, respectively. Mean time to reach C_max was 0.36 ± 0.2, 0.08 ± 0.00, and 0.13 ± 0.07 hr after i.m. injection at 2, 4, and 6 mg/kg, respectively. The mean value of T_1/2λz for i.m. administration at doses of 2, 4, and 6 mg/kg was 71.39 ± 28.42, 91 .33 ± 50.02, and 96.43 ± 45.02 hr, respectively. The mean residence times were 63.81 ± 10.96, 35.83 ± 15.13, and 38.18 ± 16.77 hr for doses of 2, 4, and 6 mg/kg, respectively. These pharmacokinetic characteristics after i.m. administration indicated that TD could be rapidly distributed into tissues on account of the high lipid solubility and then released into plasma. In addition, the absolute bioavailability of 2 mg/kg after i.m. injection was 112%. No adverse effects were observed after i.v. and i.m. administration.     

Effects of orchidectomy on bone metabolism in beagle dogs

The effects of orchidectomy on bone metabolism in male beagle dogs were examined using twelve 2-year-old dogs that were orchidectomized. The dogs' bilateral iliac bones, double-labeled with tetracycline and calcein for the histomorphometry, were obtained from three dogs prior to orchidectomy and at 3, 6, 9, and 12 months afterwards. The serum biochemical constituents related to bone metabolism were examined before and every month after orchidectomy. Between 1 and 6 months after orchidectomy, the value of serum testosterone decreased (1 month), while the levels of parathyroid hormone, calcitonin, total calcium, osteocalcin, and alkaline phosphatase activity increased significantly, indicating a high bone turnover. The mean trabecular thickness and the fraction of labeled osteoid surface decreased significantly 3 months after orchidectomy, but other histomorphometric parameters were unchanged. In the period 7-12 months after orchidectomy, the parathyroid hormone level increased ever and above that of the first 6-month period, while the levels of calcitonin, osteocalcin, alkaline phosphatase activity, and phosphorus decreased. The bone volume, mean trabecular thickness, and the fraction of labeled trabecular surface decreased significantly compared with the pre-orchidectomy values. These findings indicate an imbalance in bone metabolism (i.e. bone resorption > bone formation). These results indicate that a loss of bone volume accompanied the fall in sex hormone levels following orchidectomy and suggest that the orchidectomized dog is available as an animal model for studying osteoporosis caused by hypogonadism and the decline of sex functions in men.     

Effects of topical administration of timolol maleate on intraocular pressure and pupil size in cats

Effects of topical administration of a single dose of timolol maleate, a nonselective beta-adrenergic blocking agent, on intraocular pressure (IOP) and pupil diameter were evaluated in the normotensive eyes of 10 clinically normal cats over 12 hours. Mean (+/- SEM) normal IOP was 17.1 (+/- 1.1) mm of Hg and diurnal fluctuation was observed, with the highest IOP seen in the evening. Mean (+/- SEM) normal pupil diameter was 10.1 (+/- 0.5) mm. Topical treatment with 0.5% timolol resulted in reduction of IOP in treated and nontreated eyes. This effect was time-dependent and was first observed at 6 hours after treatment. Mean reduction of IOP was 22.3% in the treated eye and 16.3% in the nontreated eye. The treated eye had reduced pupil diameter at 30 minutes after treatment, and miosis persisted throughout the 12 hours of the study. Mean reduction of pupil diameter was 38.7%. A contralateral effect on pupil diameter was not seen in the nontreated eye. Topical administration of timolol maleate results in a reduction of IOP in treated and contralateral eyes, which supports the use of timolol for treatment of glaucoma in cats. In addition, the treated eye becomes miotic. This effect may indicate beta-adrenergic inhibition or alpha-adrenergic activation of the iris sphincter muscle. beta-Adrenergic blockade would then result in miosis.     

Ocular effects of topical 0.03% bimatoprost solution in normotensive feline eyes

OBJECTIVE: The current study was undertaken to evaluate the effects of topically applied bimatoprost, an ocular hypotensive lipid, on intraocular pressure (IOP) and pupil size (PS) in healthy cats. ANIMAL STUDIED: Nine European Shorthair cats free from clinically relevant ocular abnormalities were used in the study. PROCEDURES: Pretreatment baseline measurements of IOP and PS were obtained bilaterally at 8 am, 2 pm, and 8 pm for five consecutive days (days 1 to 5). Then the cats received one drop twice daily (10 am and 6 pm) of bimatoprost ophthalmic solution 0.03% (Lumigantrade mark, Allergan Inc., Irvine, CA USA), in one randomly selected eye and one drop of artificial tears in the fellow eye (control eye) for 5 days (days 6 to 10). Values for IOP and PS were obtained under the same conditions as in the pretreatment phase. The potential for ocular irritation following bimatoprost application was also evaluated. RESULTS: During the pretreatment period, the mean IOP and mean PS were not significantly different between the eyes subsequently treated with bimatoprost and those subsequently determined as controls. During the treatment period, the mean IOP in bimatoprost-treated eyes was not significantly lower than in control eyes (14.2+/-2.3 vs. 14.5+/-2.8 mmHg). Mean IOP in control eyes was not significantly changed at any time during the study period. A marked reduction of PS was seen in all bimatoprost-treated eyes, but no other clinically relevant side effects were observed. CONCLUSION: Twice daily topical applications of bimatoprost produced miosis but had no significant effect on IOP in healthy cats.     

Sedative and analgesic effects of medetomidine in beagle dogs infected and uninfected with heartworm

The sedative and analgesic effects of medetomidine were evaluated in heartworm-infected (HW+) and uninfected (HW–) beagle dogs by intravenous (IV) and intramuscular (IM) administration of 30 µg/kg and 40 µg/kg doses, respectively. Posture, response to noise and the pedal reflex were monitored. A procedure for mock radiographic positioning was performed to evaluate its overall clinical use. Observation times were 0, 15, 30, 60, 90, 120 and 180 min. In addition, the times from injection until the dog could not stand on its feet (down time), from lateral to sternal recumbency (sternal recumbency time), and from sternal recumbency to rising again (rising time) were also noted.Medetomidine produced rapid sedation and analgesia by both routes. Down times for the IM and IV routes were similar, which verified the manufacturer's recommended doses. The HW+ dogs had shorter down times, probably owing to increased blood flow to the brain caused by adrenergic alpha-2 activity. Sternal recumbency and rising times did not differ between the groups, suggesting a similar metabolism. Sedation and analgesia were adequate for performing the procedure in all dogs. HW– dogs showed less resistance to handling during the procedure than HW+ dogs. Overall, medetomidine seems to be a suitable agent for short-term chemical restraint in dogs, even with subclinical heartworm infestation.     

Effectiveness of a dental gel to reduce plaque in beagle dogs

Tooth brushing is considered a superior technique for reducing plaque accumulation. Chemical agents may be used to reduce plaque accumulation on tooth surfaces since many owners may not be willing or able to brush their dog's teeth. Following a professional teeth cleaning procedure, a dental gel containing chlorhexidine was applied in 11 dogs BID for 7-days, while 11 other dogs received a control dental gel applied in the same manner. Dogs in the treatment group had significantly less plaque accumulation during the trial period compared with dogs in the control group. The dental gel applied in the study reported here decreases plaque accumulation in the short-term and may be beneficial in reducing the severity of gingivitis and associated periodontal disease if provided on a long-term basis.     

Influence of age on bronchoscopic findings in healthy beagle dogs

The aims of this study were to evaluate the effect of age on bronchoscopic features and bronchoalveolar lavage fluid (BALF) cellularity in dogs. Thirty healthy beagle dogs from three age groups were included: young dogs (10 months to 4.5 years of age; n = 8), middle-aged dogs (5–8 years old; n = 13) and older dogs (>8 years; n = 9). Haematology, thoracic radiography, bronchoscopy and bronchoalveolar lavage were performed; bronchoscopic findings were scored and BALF total and differential cell counts were determined. The total bronchoscopic score was higher in older dogs; these dogs had more irregular bronchial mucosa, more prominent mucosal vessels and bronchiectasis. Younger dogs had a higher percentage of neutrophils in BALF compared with middle-aged and old dogs and a higher percentage of lymphocytes in BALF compared with middle-aged dogs. The results show that age has an effect on bronchoscopic features of airways and the composition of BALF in the dog.     

Mineralisation in kidney and stomach of beagle dogs

Histological examination of 753 Beagle dogs showed renal foci of calcification in 27.9% of males and 21.5% of females. In contrast, stomach calcification was observed in 6.2% of males and 5.2% of females examined. It is suggested that the focal calcification seen in both organs was possibly of dietary origin and may have been related to the phosphate content.