Does adenosine modulate the natriuretic response to ANP in normal dogs?

To determine if the usual natriuretic response to ANP could be altered by raising intrarenal levels of adenosine, ANP was administered to normal anesthetized dogs at 100 ng.kg-1.min-1 i.v. before and after the administration of adenosine (3 micrograms.kg-1.min-1) into the left renal artery (n = 8). For each kidney, the group mean delta UNaV in response to ANP was unchanged by the presence of adenosine. However, following intrarenal infusion of adenosine, this unaltered average response for the infused kidney was achieved by either attenuation or exaggeration of the natriuresis to ANP in half the dogs, respectively. When intrarenal levels of extracellular adenosine were elevated by the i.v. infusion of dipyridamole in seven dogs, there was uniform exaggeration of an ANP-induced natriuresis by an average of 145 mu equiv./min. The provision of theophylline by itself (an adenosine antagonist) had no effect on UNaV but prevented the dipyridamole-induced exaggerated natriuresis to ANP. The infusion of adenosine deaminase into one renal artery reduced the natriuretic response to ANP. We conclude that elevated intrarenal levels of adenosine will exaggerate an ANP-induced natriuresis possibly by altering intracytosolic Ca2+.     

Are dogs able to recognize their handler's voice? A preliminary study

Abstract

A number of studies have dealt with the ability of dogs to rely on olfactory cues to recognize their owner or handler. However, in the absence of these cues (e.g., when working at a distance from their owner) dogs have to use other senses to interact with their owner. Considering the high sensitivity of their auditory system, we can hypothesize that dogs are able to use vocal cues for this purpose. Certainly, it is commonly assumed that dogs can discriminate between people on the basis of their voice, and yet there is a clear lack of empirical data on this subject. The present study assesses the importance of the handler's olfactory and visual cues versus the importance of his/her vocal cues to the working behavior of dogs. I compare the ability of working dogs to obey different vocal commands issued either by their handler (HV) or by a stranger (SV) via loudspeakers in different olfactory contexts: presence of their handler (H) or of a stranger (S). The dogs' performance (percentage of correct responses) decreased when the acoustic cues were modified (H+HV tended to differ from the H+SV—p = 0.09—and differed from the S+SV conditions—p = 0.05) but not when only the olfactory cues were changed (no difference between H+HV and S+HV conditions—p > 0.1). Consequently, we can assume that dogs rely, at least in part, on acoustic parameters of voices to recognize and cooperate with their handler.     

Vaccination of dogs against Echinococcus granulosus: a means to control hydatid disease?

Hydatid disease continues to be a substantial cause of morbidity and mortality worldwide. Elimination is difficult with current control options, but reducing egg production by Echinococcus granulosus (Eg) in canines might help to reduce transmission in areas where the parasite is endemic. Recently obtained data using recombinant protein-based and live attenuated Salmonella vaccines are preliminary but encouraging and auger well for the future development of an effective dog vaccine against Eg, although much additional work is required before this becomes a reality. New approaches to control and for the prevention of hydatidosis have been described recently, and important additional gains should be expected if the efficacy of the dog vaccines is confirmed and leads to their incorporation into future control options.     

How many footsteps do dogs need to determine the direction of an odour trail?

Dogs have the ability to determine the direction of an odour trail left by a human. This study examined how much olfactory information from this trail is required by dogs to determine direction. Six dogs, able to determine direction, were tested on a 21 footstep trail laid on 21 individual carpet squares, one footstep per square, by the same individual wearing the same shoes. Dogs brought in at right-angles to the trail at its centre were able to correctly determine direction better than chance (P < 0.025). Dogs were unable to determine direction when the order of the footsteps was randomized by rearranging the order of the carpet squares. When the individual odour cue was removed, but ground disturbance left, dogs were unable to determine direction, indicating that it was the odour of the individual that was used to determine direction. In the final experiment the number of footsteps made available to the dog was reduced from 21 to 11 and then 9, 7, 5 and finally 3. Dogs were able to determine direction from 5 footsteps but not 3. It was calculated that it takes approximately 1-2 s for the odour information in footsteps to change to provide discernible information that can be used by dogs to determine direction. The process by which dogs may determine direction from odour cues is discussed.     

Frequency of antibodies to Toxoplasma gondii in stray dogs of Oaxaca, México

We studied the frequency of antibodies against Toxoplasma gondii in stray dogs in the city of Oaxaca, Mexico through the evaluation of 154 sera by indirect ELISA. A frequency of 61.7% was found; it was higher in males (45 of 65, 69.2%) than in females (49 of 89, 55.0%), although this difference was not statistically significant. An increase in frequency was observed with age, the lowest being among animals younger than 1 yr (4 of 20, 20.0%) and the highest in dogs older than 7 yr (21 of 25, 84.0%). This is the first study in dogs of this region of Mexico and revealed high T. gondii transmission and evidence of early exposure in animals that are in close contact with contaminated water or raw meat, or both. Further studies are needed in order to understand the role of T. gondii infection in public health.     

Do more sociable dogs gaze longer to the human face than less sociable ones?

Domestic dogs (Canis familiaris) are especially skillful in communicating with humans, and they rely on special abilities to do that. One of these skills involves gazing at human faces in cases of uncertainty or when seeking for something out of reach. In this study, we evaluated the relationship between dogs' sociability level and the ability to learn to gaze in a situation with food in sight but out of their reach. Thirty-nine adult dogs were tested in two procedures: (1) a sociability test that involved interacting with an unknown person, and (2) a learning task that consisted of training trials in which gazing at the experimenter's face was food reinforced, followed by extinction trials in which gazing was not followed by food. A significant positive correlation was found between the duration of physical contact with the unknown person in the sociability test and gaze duration during extinction. Moreover, high sociability dogs gazed significantly longer at humans during extinction trials. We discuss the possibility that, more sociable animals, such as those who pay more attention to the person in our sociability test, may be more persistent in their communicative attempts because the presence of the human is intrinsically reinforcing to them. Finally, we comment on the importance of these findings for training purposes.     

Do large dogs die young?

In most animal taxa, longevity increases with body size across species, as predicted by the oxidative stress theory of aging. In contrast, in within-species comparisons of mammals and especially domestic dogs (e.g. Patronek et al., '97; Michell, '99; Egenvall et al., 2000; Speakman et al., 2003), longevity decreases with body size.We explore two datasets for dogs and find support for a negative relationship between size and longevity if we consider variation across breeds. Within breeds, however, the relationship is not negative and is slightly, but significantly, positive in the larger of the two datasets. The negative across-breed relationship is probably the consequence of short life spans in large breeds. Artificial selection for extremely high growth rates in large breeds appears to have led to developmental diseases that seriously diminish longevity.     

What happens to shelter dogs? An analysis of data for 1 year from three Australian shelters

Annually, welfare shelters admit many dogs, including those whose caregivers surrender them or dogs who are strays. This article analyzes admission data from 3 metropolitan Australian shelters. The study collected data for a 1-year period and analyzed them to identify the characteristics of the typical shelter dog; patterns of relinquishment, sales, reclamation and euthanasia; and duration of stay and reasons underlying euthanasia, relinquishment, and postadoptive return. The study tracked more than 20,000 admissions during this period. To facilitate reclamation, the local Code of Practice requires a mandatory holding period for stray dogs; assessment for suitability for rehoming then occurs. Dogs failing the assessment are euthanized. Surrendered dogs can be assessed immediately. The Code of Practice also recommends that unsold dogs be euthanized 28 days postassessment. Typically, shelter dogs in Melbourne are strays, sexually entire, adult, small, and-usually-male. The majority of admissions are reclaimed or sold. Most reclamations occur within 4 days, and postadoptive return rates are low. That current desexing messages do not appear to have reached the owners of stray dogs to the same extent as they have other dog owners is a major finding, suggesting that a targeted education campaign may be required.     

What happens to shelter dogs? Part 2. Comparing three melbourne welfare shelters for nonhuman animals

Although the characteristics of dogs admitted to animal welfare shelters have been described previously, few studies have compared the statistics of different welfare shelters. The existing studies compare shelters that differ operationally and philosophically on factors such as whether they perform euthanasia or whether the shelter receives both impounded and relinquished animals. This study aims to determine whether differences in admission and outcome data exist between shelters when these issues are constant. The study sampled 3 metropolitan Australian shelters over a 12-month period. All shelters sampled serve both as municipal pounds and welfare shelters, perform euthanasia as required, and operate within the relatively small, culturally homogeneous environment of Melbourne. The study observed significant differences between shelters regarding the admission characteristics of the dogs, length of stay, and outcomes. The identification of these differences may enable us to establish “best-practice ”procedures capable of implementation elsewhere. The differences identified in the reasons given for relinquishment between locations also may have policy and educational implications for animal control agencies.     

Lactobacilli and enterococci — Potential probiotics for dogs

Forty strains of enterococci and forty strains of lactobacilli isolated from feces of 10 healthy dogs were tested for the antimicrobial activity, tolerance to bile and adhesion activity. The total count of fecal enterococci reached 5.5 log CFU/g and of lactobacilli 7.6 log CFU/g. Screening for production of bacteriocin-like substances showed an to partly inhibit the growth of Enterobacter sp. (hazy zones of inhibition). Ten strains of Enterococcus sp. and nine strains of Lactobacillus sp. were found without any inhibitory activity against all indicators used. Seven enterococcal strains and six lactobacilli with the broadest antimicrobial spectrum were selected for further probiotic assays. In the presence of 1% bile, the survival rate of selected enterococci (71.7-97.5%) was higher than that of lactobacilli (66.7-75.4%). The adhesion of strains to human intestinal mucus (5.1-8.2% by enterococci, 2.7-8.3% by lactobacilli) was found to be similar as adhesion to canine intestinal mucus (3.7-10.6% by enterococci, 2.1-6.0% by lactobacilli). Strain AD1, one lactobacillus isolate, reduced the higher level of serum cholesterol and alanine aminotransferase after oral administration to dogs suffering from diseases of the gastrointestinal tract.     

Müllerian inhibiting substance in sex-reversed dogs

In normal males, Müllerian Inhibiting Substance (MIS), produced by testes during an embryonic critical period, is thought to induce regression of the Müllerian duct system, including the oviducts and uterus. In XX sex-reversed dogs, an apparent contradiction has been reported: The uterus persists in the presence of testes or ovotestes. The objective of this study is to determine whether testes of XX male and ovotestes of true hermaphrodite dogs produce MIS, and to examine the anatomy of Müllerian duct derivatives of affected dogs for evidence of regression. Gonadal samples were tested for MIS activity in a bioassay. The mean MIS activity score of XX males was similar to that of normal XY males and significantly greater than that of normal XX females. The mean MIS activity score of XX true hermaphrodites was intermediate between normal XX females and XY males. Within the true hermaphrodite group, ovotestes in which the proportion of testicular tissue was greater than or equal to 1/2 had higher MIS scores than those in which the proportion of testicular tissue was less than 1/2. XX males had a well-developed epididymis adjacent to each testis, but no oviducts. In true hermaphrodites, the oviduct regressed and an epididymis was present when greater than or equal to 1/2 of the adjacent ovotestis was testicular, and MIS activity in that gonad was high. A few ovotestes with intermediate levels of MIS activity had both an oviduct and an epididymis. Regression of the oviductal portion of the Müllerian duct system was positively correlated to the amount of testicular tissue and the MIS activity of the gonad, as would be predicted by Jost's original hypothesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Seasonal variations in lectin‐induced lymphocyte transformation in beagle dogs

Abstract

The lymphocyte stimulation test (LST) is an in vitro corollary of in vivo cell‐mediated immunity. We have analyzed LST results from 32 dogs covering a 16‐month time span. Two mitogens (plant lectins) were used in the LST, phytohemagglutinin (PHA) and concanavalin A (Con A) with comparable results. All dogs exhibited a seasonal variation in LST results using both mitogens. The dogs were either controls or were in one of five groups that received whole‐body gamma ray irradiation from a ⁶⁰CO source. There was little effect of irradiation except on the mean levels of oscillation. Few differences were noted among groups. The estimated mean times of peak activity in the LST ranged from July 19‐August 2 for PHA and from July 18‐August 15 for Con A. The times of peak of individual dogs for both mitogens were predominantly in the calendar quarter June 21 ‐September 20, and were, therefore, not randomly distributed throughout the year. The implications of these findings are discussed.     

Hormonal changes in spontaneous and aglépristone-induced parturition in dogs

To increase our understanding of the endocrine changes associated with parturition in dogs, plasma concentrations of progesterone (P4), 15-ketodihydroprostaglandin F(2alpha) (PGFM), estradiol-17-beta (E2beta), cortisol, ACTH, prolactin (PRL), LH, and FSH were measured in six spontaneously whelping bitches and in six bitches in which parturition was induced with the progesterone-receptor blocker aglépristone on day 58 of pregnancy. Expulsion of pups in the induced group took place in the presence of P4 concentrations that were still elevated. PGFM concentrations increased before parturition in both groups, but levels were lower in the induced bitches. PGFM levels reached a maximum in both groups during parturition and quickly decreased in the spontaneously whelping group after parturition, but remained elevated in the induced group. In both groups, cortisol concentrations reached similar maximum levels during the last 30 h before the onset of expulsion. During the 3 days postpartum, cortisol concentrations were higher in the induced group. The highly variable ACTH concentrations did not differ significantly throughout the study within or between groups. In both groups, E2beta concentrations decreased and PRL concentrations increased between the late gestational period and the 30-h period before parturition. Concentrations of both LH (spontaneously whelping group) and FSH (both groups) decreased between late gestation and the postpartum period. The results of this study illustrate the hormonal changes around parturition in the bitch, and reveal that aglépristone-induced parturition is associated with still incomplete luteolysis, an altered PGFM profile, and elevated postpartum cortisol concentrations as compared with spontaneously whelping dogs.