Colony Of Dogs Research Articles

Long-term stability, reproducibility, and statistical sensitivity of a telemetry-instrumented dog model: A 27-month longitudinal assessment

IntroductionICH guidelines, as well as best-practice and ethical considerations, provide strong rationale for use of telemetry-instrumented dog colonies for cardiovascular safety assessment. However, few studies have investigated the long-term stability of cardiovascular function at baseline, reproducibility in response to pharmacologic challenge, and maintenance of statistical sensitivity to define the usable life of the colony. These questions were addressed in 3 identical studies spanning 27months and were performed in the same colony of dogs. MethodsTelemetry-instrumented dogs (n=4) received a single dose of dl-sotalol (10mg/kg, p.o.), a β1 adrenergic and IKr blocker, or vehicle, in 3 separate studies spanning 27months. Systemic hemodynamics, cardiovascular function, and ECG parameters were monitored for 18h post-dose; plasma drug concentrations (Cp) were measured at 1, 3, 5, and 24h post-dose. ResultsBaseline hemodynamic/ECG values were consistent across the 27-month study with the exception of modest age-dependent decreases in heart rate and the corresponding QT-interval. dl-Sotalol elicited highly reproducible effects in each study. Reductions in heart rate after dl-sotalol treatment ranged between −22 and −32 beats/min, and slight differences in magnitude could be ascribed to variability in dl-sotalol Cp (range=3230–5087ng/mL); dl-sotalol also reduced LV-dP/dtmax 13–22%. dl-Sotalol increased the slope of the PR–RR relationship suggesting inhibition of AV-conduction. Increases in the heart-rate corrected QT-interval were not significantly different across the 3 studies and results of a power analysis demonstrated that the detection limit for QTc values was not diminished throughout the 27month period and across a range of power assumptions despite modest, age-dependent changes in heart rate. DiscussionThese results demonstrate the long-term stability of a telemetry dog colony as evidenced by a stability of baseline values, consistently reproducible response to pharmacologic challenge and no diminished statistical sensitivity over time.

Multiple Mechanisms Contribute to Leakiness of a Frameshift Mutation in Canine Cone-Rod Dystrophy

Mutations in RPGRIP1 are associated with early onset retinal degenerations in humans and dogs. Dogs homozygous for a 44 bp insertion including a polyA29 tract potentially leading to premature truncation of the protein, show cone rod degeneration. This is rapid and blinding in a colony of dogs in which the mutation was characterised but in dogs with the same mutation in the pet population there is very variable disease severity and rate of progression.ObjectiveWe hypothesized that this variability must be associated with leakiness of the RPGRIP1 mutation, allowing continued RPGRIP1 production. The study was designed to discover mechanisms that might allow such leakiness.MethodsWe analysed alternate start sites and splicing of RPGRIP1 transcripts; variability of polyAn length in the insertion and slippage at polyAn during transcription/translation.Results and SignificanceWe observed a low rate of use of alternative start codons having potential to allow forms of transcript not including the insertion, with the possibility of encoding truncated functional RPGRIP1 protein isoforms. Complex alternative splicing was observed, but did not increase this potential. Variable polyAn length was confirmed in DNA from different RPGRIP1 −/− dogs, yet polyAn variability did not correspond with the clinical phenotypes and no individual was found that carried a polyAn tract capable of encoding an in-frame variant. Remarkably though, in luciferase reporter gene assays, out-of-frame inserts still allowed downstream reporter gene expression at some 40% of the efficiency of in-frame controls. This indicates a major role of transcriptional or translational frameshifting in RPGRIP1 expression. The known slippage of reverse transcriptases as well as RNA polymerases and thermostable DNA polymerases on oligoA homopolymers meant that we could not distinguish whether the majority of slippage was transcriptional or translational. This leakiness at the mutation site may allow escape from severe effects of the mutation for some dogs.

Fed and fasted gastric pH and gastric residence time in conscious beagle dogs

The gastric pH values are controversial in the literature. Some suggest the dog gastric pH is higher than human and dog gastric pH after fed with particular diet is uncertain. Gastric pH in 16 male beagle dogs was measured using Bravo pH telemetry system. For the fed study, the dogs received 10 or 200 g of dog dry food (5L18) 15 min before dosing the Bravo pH capsule, followed by a 50 mL of water to aid in swallowing. It was surprising to find a small, but statistically significantly lower pH in the fed compared to the fasted stomach. The average gastric pH in fasted dogs was 2.05 and 1.08 and 1.26 for 10 and 200 g fed dogs. The average gastric emptying time of the capsule was 1.4, 9.4 and 20 h for fasted, 10 g fed and 200 g fed dogs, respectively. The inter-individual variability was higher in fasted dogs than in fed dogs. The results showed the gastric pH in each colony of dogs can be different from reported values in the literature. It emphasizes that the importance of measuring the pH in each colony when dogs are used to evaluate pharmacokinetics of pH sensitive drugs or formulations.

A package for VWD endothelial cells

Comment on De Meyer et al, page [4728][1] In this issue of Blood , De Meyer and colleagues not only report the procurement of endothelial progenitor cells from dogs, but they also procure endothelial cells from a colony of dogs with severe von Willebrand disease that have the added potential to

FIRST BREEDING RECORD OF A MOUNTAIN PLOVER IN NUEVO LEON, MEXICO

Abstract We document the first breeding record of Mountain Plovers (Charadrius montanus) in the state of Nuevo Leon, Mexico. On 9 July 2004, we located a nest with two eggs and one chick in a colony of Mexican prairie dogs (Cynomys mexicanus). Mean height of vegetation near the nest was 7.1 cm, and bare ground cover was 41.2% (30 m2 sampled). Although this record represents the second nesting for this species in Mexico, it is the first to document successful breeding.

Effect of Diet and Tylosin on Chronic Diarrhea in Beagles

Seven beagles in a colony of dogs had chronic diarrhea for at least 30 days. The dogs were subsequently treated with tylosin 20 mg/kg BW q24h PO for 10 days. During the treatment period, the feces became firmer but remained loose. When the treatment was discontinued, the diarrhea reappeared in 3 weeks. The feces remained abnormally loose in all dogs treated with metronidazole, trimethoprim-sulfadiazine, or doxycycline and prednisone. The diet was then changed for 10 days from a highly digestible moist pet food to a dry food developed for normal adult dogs. The feces again became firmer, although still loose in some dogs. The period was then extended to 3 month, but the fecal consistency continued to fluctuate from ideal to diarrhea. The dogs were treated a 2nd time with tylosin 20 mg/kg BW q24h PO for 10 days. The feces then became significantly firmer and remained so throughout a 3-month follow-up. We conclude that the combination of diet and tylosin was more effective than either agent alone in control of chronic diarrhea.

Effect of Diet and Tylosin on Chronic Diarrhea in Beagles

Seven beagles in a colony of dogs had chronic diarrhea for at least 30 days. The dogs were subsequently treated with tylosin 20 mg/kg BW q24h PO for 10 days. During the treatment period, the feces became firmer but remained loose. When the treatment was discontinued, the diarrhea reappeared in 3 weeks. The feces remained abnormally loose in all dogs treated with metronidazole, trimethoprim-sulfadiazine, or doxycycline and prednisone. The diet was then changed for 10 days from a highly digestible moist pet food to a dry food developed for normal adult dogs. The feces again became firmer, although still loose in some dogs. The period was then extended to 3 month, but the fecal consistency continued to fluctuate from ideal to diarrhea. The dogs were treated a 2nd time with tylosin 20 mg/kg BW q24h PO for 10 days. The feces then became significantly firmer and remained so throughout a 3-month follow-up. We conclude that the combination of diet and tylosin was more effective than either agent alone in control of chronic diarrhea.

The clinical and immunological reaction to a flavoured monthly oral heartworm prophylatic in 12 dogs with spontaneous food allergy

There is debate among practicing veterinary dermatologists as to whether flavoured prophylactics should be avoided in the food‐allergic dog. At North Carolina State University we have a colony of dogs with spontaneous food allergy. They are maintained on a hypoallergenic diet (Prescription diet d/d Duck and Rice, Hills Pet Nutrition, Topeka, KS). A flavoured chewable tablet containing pork liver, soy and 2.3 mg of milbemycin (Interceptor Flavor Tabs, Novartis Animal Health, Greensboro, NC) was administered under controlled conditions to 12 dogs. Previous exposure to this medication was documented. A physical examination was performed prior to, and on four occasions after, tablet administration. A clinical score (CS) was assigned to determine the severity of skin and otic disease. Serum was collected at 3‐ to 5‐day intervals. Allergen‐specific IgE (soy, pork and corn) was measured by ELISA. Statistical analysis was performed using SAS software (Cary, NC, USA) and a longitudinal mixed model was employed for the evaluation of the clinical response. An increased CS was observed in 10 dogs post‐challenge; peak values were measured on day 2 (five dogs) and day 5 (five dogs). When compared with pre‐treatment CS this increase was statistically significant (P < 0.05). Significant peaks in serum allergen‐specific IgE were measured on days 5 and 20 to soy, pork and corn. The authors conclude that these dogs have a rapid adverse clinical response to this flavoured medication which is accompanied by a significant increase in serum allergen‐specific IgE, although this does not necessarily correlate with the orally administered allergen.

Epidemiology of Toxascaris leonina infection post-weaning within a colony of dogs.

This communication reports incidental observations on Toxascaris leonina infections in a beagle breeding colony. Regular faecal monitoring demonstrated that T. leonina was endemic in the adult dam population within this colony. Small numbers of T. leonina eggs were also detected in the faeces of weaned pups from eight weeks of age possibly produced by a patent infection. This would mean a pre-patent period for T. leonina of 56 days or less. Worm counts on 10 pups showed that 60% of pups had acquired a T. leonina infection by 12 weeks of age. Since prenatal and lactogenic transmission do not occur and as the pups were kept in an environment which reduced chances of infection with T. leonina and there was no apparent source of paratenic hosts, the source of infection must have been embryonated T. leonina eggs from the whelping environment. These observations on T. leonina demonstrate that, if pups are exposed to an infected environment, patent infections may be seen in a younger age group than is normally associated with T. leonina infections.

Noncirrhotic portal hypertension and nodular regenerative hyperplasia of the liver in dogs with mucopolysaccharidosis type I.

Nodular regenerative hyperplasia (NRH) is an uncommon hepatic lesion often associated with noncirrhotic portal hypertension (PHT). We have noted that NRH and PHT are frequent occurrences in a colony of dogs with the genetic storage disease, mucopolysaccharidosis I (MPS-I). This observation provides the opportunity to study the histology and pathogenesis of NRH and noncirrhotic PHT in a new animal model. Thirteen of 32 dogs (41%) with MPS-I developed multiple portocaval shunts between 4 and 48 months of age that were grossly visible at necropsy. Seven of the 13 developed marked ascites, whereas all those without shunts and littermates (n = 24) heterozygous for the mutated alpha-L-iduronidase allele (carriers unaffected by the storage disease) did not. The large and medium-sized portal veins were widely patent without thrombosis or vascular malformations. Hepatic parenchymal fibrosis was absent or mild and did not correlate with shunt formation. All 32 livers had varying degrees of diffuse periportal hepatocellular hyperplasia with multifocal atrophy and compression of centrolobular cords (NRH) most prominent in dogs with shunts. Many small portal veins were reduced in diameter or absent, especially in animals with shunts. Noncirrhotic PHT and NRH appear to be related to the obliteration of small portal veins in these dogs, but the pathogenesis of this vascular change remains unknown.

X-linked ectodermal dysplasia in the dog.

A male German shepherd pup had symmetrical areas of hairlessness as well as missing and misshapen teeth. There was no family history of a similar phenotype. In biopsies of the hairless skin and foot pads there were no hair follicles, adnexal structures, or eccrine glands. These findings resemble those in ectodermal dysplasia in the Tabby mouse and anhidrotic/hypohidrotic ectodermal dysplasia (HED) in man, which are both X-linked recessive disorders and thought to be homologous gene defects. While similar cases of ectodermal dysplasia have been reported in the dog and some genetic studies carried out, definitive confirmation of X-linked inheritance of canine ectodermal dysplasia is lacking. Family studies and experimental matings using the propositus gave results that confirm X-linked recessive inheritance. On statistical grounds, it is concluded that ED in the propositus is due to a new mutation. A colony of dogs with this mutation is maintained for further study.

P53, erbB-2 and K-ras Gene Alterations Are Rare in Spontaneous and Plutonium-239-Induced Canine Lung Neoplasia

Inhalation of high-linear energy transfer radiation in the form of radon progeny is a suspected cause of human lung cancer. To gain insight into the types of genetic derangement(s) caused by this type of radiation, lung tumors from beagle dogs exposed to 239PuO2 and those arising in animals with no known carcinogen exposure were examined for evidence of aberrations in genes known to be altered in lung tumors. Altered expression of the p53 tumor suppressor gene and proto-oncogene erbB-2 proteins (p185erbB2) was evaluated by immunohistochemical analysis of 117 tumors representing different histological types in exposed (n = 80) and unexposed (n = 37) animals. Twenty-eight tumors were analyzed for K-ras proto-oncogene mutations by polymerase chain reaction amplification and direct sequencing. Fourteen percent (16/116) of all lung neoplasms showed elevated nuclear accumulation of p53 protein. Regardless of exposure history, adenosquamous and squamous cell cancers comprised 94% of all tumors with p53 abnormalities. Eighteen percent (21/117) of all tumors had evidence in codons 12, 13 or 61 tumors from unexposed (n = 9) or plutonium-exposed dogs (n = 19). These data indicate that p53 and K-ras gene abnormalities as a result of missense mutation are infrequent events in spontaneous and 239PuO2-induced lung neoplasia in this colony of beagle dogs. Alternative mechanisms of gene alteration may be involved in canine pulmonary carcinogenesis.

901-64 Heterogeneous Sympathetic Innervation in German Shepherd Dogs with Inherited Ventricular Arrhythmia and Sudden Death

An inbred colony of German Shepherd dogs with spontaneous ventricular arrhythmias and sudden death has recently been identified. The median age of onset of the arrhythmia (4.5 months), the tendency for sudden death to occur during REM sleep, during/following exercise, and the absence of structural heart disease suggest a developmental abnormality of the autonomic innervation to the heart. To further evaluate this possibility, we studied 7 dogs from this colony, mean age 5.2 months. Three of seven were severely affected (frequent VT on holter). two were mildly affected, and two had no arrhythmias by holter analysis. We imaged the distribution of functional myocardial sympathetic innervation and perfusion using I-123 metaiodobenzylguanidine (MIBG) and thallium-201 respectively. Sympathetic nerve distribution was evaluated morphologically by immunocytochemical localization of tyrosine hydroxylase. Six mCi of I-123 MIBG was injected IV followed three hours later by 2 mCi of thallium-201. The hearts were excised, sliced transversely, and imaged directly for MIBG and thallium. Color functional maps were derived to display the distribution of innervation (MIBG) and perfusion (thallium-2011 simultaneously. Following imaging, the slices were fixed in formaldehyde then stored at 4°C in 30% sucrose/phosphate buffer until processing for immunohistochemistry. All of the hearts showed homogeneous thallium perfusion, however there was evidence of a regional decrease in MIBG uptake ranging from 10% to 45% of the left ventricle, consistent with regional denervation. The defects were generally localized to the anterior and septal territories. Immunocytochemial studies on sections from regions with decreased MIBG uptake showed a striking paucity of nerves compared to regions with normal MIBG uptake, confirming denelVation. While all of the hearts showed denelVation, 2/3 with severe arrhythmia showed either extensive denervation or a steep gradient in MIBG uptake, while 1/4 of the mildly affected or dogs without arrhythmias showed extensive denervation. We conclude that there is abnormal heterogeneous sympathetic innervation in this population of dogs with spontaneous naturally occurring ventricular arrhythmias and increased incidence of sudden cardiac death. This heterogeneity of innervation may playa role in the etiology of ventricular arrhythmia, particularly during states of increased sympathetic tone.

Water Relations of Agropyron smithii and Bouteloua gracilis and Community Evapotranspiration Following Long-term Grazing by Prairie Dogs

-The influence of intensive grazing on canopy microclimate, grass leaf water relations and community evapotranspiration was investigated by comparing a grassland heavily grazed by a colony of black-tailed prairie dogs (Cynomys ludovicianus) with an adjacent lightly-grazed, uncolonized area in a northern-mixed prairie in South Dakota. Total aboveground plant biomass was lower on the colony through the growing season. Daytime leaf and air temperatures were higher on the colony. Although daytime air vapor pressure in the canopy was higher on the colony, higher leaf temperatures resulted in higher leaf-to-air vapor-pressure differences on the colony. Along with higher vapor-pressure differences, higher wind speeds within the canopy probably also contributed to higher evaporative demand. In spite of this, the dominant grasses, Agropyron smithii and Bouteloua gracilis, had consistently higher leaf conductances to water vapor and water potentials (4) on the colony, especially later in the day and growing season. Predawn leaf 'p were higher on the colony in July and August, suggesting available soil moisture in the rooting zone was higher there. At the community level, afternoon evapotranspiration rates were lower on the colony in June, but higher on the colony in July and August as soil water became more limiting. While intensive grazing by prairie dogs lead to a warmer canopy microclimate with higher evaporative demand, any detrimental effects on plant water status were apparently offset by greater available soil moisture, especially later in the day and season. Greater soil water availability on the colony was probably the result of smaller transpiring leaf mass (and area), although soil factors such as improved infiltration due to prairie dog burrows can not be ruled out as causative factors.

Immunosuppression of canine renal allograft recipients by CD4 and CD8 monoclonal antibodies.

A state of tolerance to MHC mismatched allografts can be generated in rodents by treatment with CD4 and CD8 monoclonal antibodies (mAb). In order to transpose this type of therapy to large animals and ultimately to the clinic, a suitable model is required. To this end we have generated a series of mAb to the canine CD4, CD8, and Thy-1 antigens and have tested their ability to prevent rejection of renal allografts. Donor-recipient pairs were selected from a colony of mongrel dogs in which untreated rejection of two haplotype-mismatched kidneys occurred by day 7 (defined as a serum creatinine > 300 mumol/l). Therapy with either the CD4 or the CD8 mAb, using no other immunosuppression, did not prolong graft survival. Depletion of T cells by a Thy-1 mAb prior to surgery only extended graft survival to day 9. However, treating with combinations of mAb up to day 10 (CD4 plus Thy-1; CD4 plus CD8; or CD4 plus CD8 plus Thy-1) prolonged renal allograft function up to 25 days. Combination of the triple mAb therapy with a sub-therapeutic immunosuppressive drug regimen (cyclosporin A plus azathioprine that alone gave a median survival of 15 days) favored survival to a median of 38 days. This protocol also inhibited the antiglobulin response that had curtailed the effects of mAb treatment, opening the way to more extended, and potentially tolerizing, mAb plus drug regimens.

Platelet aggregation and dense granule secretion in a colony of dogs with spontaneous hypertension.

Since canine hereditary essential hypertension has been previously reported in a colony of Siberian husky dogs, we tested the suitability of this model for use in studies on the platelet defect identified in humans with essential hypertension. Platelet aggregation and dense granule ATP secretion were measured in dogs with essential hypertension and normotensive control dogs. The platelets from the hypertensive group showed significantly increased aggregation and secretion in response to stimulation with ADP. There was no significant increase in aggregation or secretion when platelets from hypertensive dogs were stimulated by platelet-activating factor, thrombin, calcium ionophore A23187 or phorbol myristate acetate. The increased aggregation and secretion responses in platelets from the hypertensive dogs suggest that a defect similar to that reported in humans with essential hypertension exists and that further investigation is warranted.

Spontaneous familial systemic lupus erythematosus in a canine breeding colony

A colony of German shepherd dogs was studied in which a high proportion of antinuclear antibody (ANAb) carriers and dogs with systemic lupus erythematosus (SLE)-like signs were found. The titre of serum thymulin and the percentage of circulating T lymphocytes were both low. The incidence of disease decreased down the generations through the introduction of outside sires, thus suggesting a genetic origin for the disease.

Primary hypertension in a colony of dogs.

A 5-year-old female Siberian husky that was diagnosed as an essential hypertensive was bred several times over a 5-year period, producing a colony of 39 offspring. Thirty of the 39 animals were subjected to biweekly systemic arterial blood pressure determinations with femoral arterial puncture and were placed into two hypertensive and two normotensive groups based on mean blood pressure: Group 1 (mean blood pressure, 128 +/- 12 mm Hg), Group 2 (mean blood pressure, 121 +/- 3 mm Hg), Group 3 (mean blood pressure, 114 +/- 8 mm Hg), and Group 4 (mean blood pressure, 101 +/- 9 mm Hg). Groups 1, 2, and 3 had mean blood pressures significantly higher than that of Group 4 (p less than 0.05). Ten dogs (representatives from Groups 1, 2, and 3) were subjected to more detailed clinical testing including angiography, echocardiography, ophthalmic examination, plasma catecholamine and renin activity measurements, plasma lead and cadmium determinations, cerebrospinal fluid examination, renal profile, and serum chemistry and hematological analysis. Five unrelated normotensive Siberian huskies were compared with colony dogs by using echocardiography. Groups 1 and 2 showed a clear but statistically insignificant upward trend in left ventricular wall thickness indexed against body weights when compared with that in Group 3 and in the unrelated five normal Siberian dogs. Thus, the only specific difference from group to group in the colony at the termination of this study was the difference in mean blood pressure. Based on these data, it is possible and likely that aging will reveal changes secondary to chronic primary hypertension. The pathogenesis of this hereditary disorder remains unknown.

Airway responsiveness to inhaled antigen, histamine, and methacholine in inbred, ragweed-sensitized dogs.

We studied the responses to antigen in animals selected from a colony of inbred dogs sensitized to specific allergens to determine if they had characteristics similar to those of human asthmatics. They were immunized with ragweed and grass pollen extracts (10 micrograms in alum) immediately after routine vaccination with attenuated live virus (distemper and hepatitis) and killed bacteria (Leptospira) at 4, 8, and 12 wk of age. Subsequently, ragweed and grass injections were repeated every 2 months. Immunized dogs made specific IgE-antibodies in serum averaging 3 to 4 times that of control animals (no immunization with pollen or vaccine). They showed positive skin responses to the injection of ragweed pollen extract, whereas control dogs did not respond to ragweed pollen by quantitative skin test or inhalation challenge. In immunized dogs under barbiturate anesthesia, air-flow resistance of the total respiratory system increased from 0.60 +/- 0.07 (mean +/- SEM) before to 12.6 +/- 3.4 cm H2O/lps 5 min after the start of antigen aerosol; respiratory resistance remained increased for 20 min and was associated with 0 hypoxemia and increased arterial plasma histamine. In addition, airway responsiveness to both inhaled histamine and methacholine was greater in immunized dogs than in nonimmunized dogs of comparable age. Airway responses to each agonist were highly reproducible on repeated testing. These results indicate that physiologic responses to antigen by inbred, ragweed-sensitized dogs resemble human asthma closely and that these dogs appear suitable for a variety of experimental studies of asthma with respect to pathogenesis, diagnosis, prevention, and treatment.

The atopic dog model: report of an attempt to establish a colony.

In an attempt to establish a colony of atopic dogs as a research resource, dogs with seasonal dermatitis - a reported manifestation of naturally occurring allergy in that species - were identified, acquired, and inbred. Progeny were studied during their first 2 years of life to determine if the trait could be genetically transmitted and to investigate the hypothesis that this spontaneously occurring dermatitis correlates with positive laboratory measurements for specific IgE to airborne allergens. (Serial immunoglobulin levels, including total IgE, end-point titration of histamine, and results of fecal examinations for identification of parasites were also investigated and are to be the subject of a separate publication.) Only a weak correlation between positive direct skin test results and the appearance of seasonal dermatitis was found in initial studies. Neither the results of testing by passive cutaneous anaphylaxis nor radioallergosorbent procedures correlated with positive clinical findings. Independently conducted clinical examinations and direct skin testing using selected antigens, as well as additional bronchial challenges of representative animals from the colony, also failed to furnish evidence of atopy in the dogs. Therefore, the goal of establishing an inbred line of atopic animals was not accomplished within the allotted 2-year period. Also, the data did not show a positive correlation between the seasonal dermatitis and measurements for specific IgE to airborne allergens.