Pattern of nipple use by puppies: A comparison of the dingo (Canis dingo) and the domestic dog (Canis familiaris).

Surprisingly little information is available about the behavior of newborn mammals in the functionally vital context of suckling. We have previously reported notable differences in the pattern of nipple use by kittens of the domestic cat and puppies of the domestic dog. Whereas kittens rapidly develop a "teat order," with each individual using principally 1 or 2 particular nipples, puppies show no such pattern. We asked whether the more "chaotic" behavior seen in puppies of the domestic dog (Canis familiaris) could be the result of relaxed selection due to domestication. In a first test of this hypothesis, we studied suckling behavior in 4 litters of wild-type captive dingoes (Canis dingo), a canid species that has inhabited the Australian mainland in substantial numbers for at least 5,000 years with minimal human influence. On all measures of individual puppies' behavior-time spent attached to nipples, lack of individual use of particular nipples and consequent absence of a teat order, lack of synchronized suckling with other littermates, lack of agonistic behavior-we found no differences between the 2 species. In conclusion, we suggest that the difference between the pattern of suckling behavior of kittens of the domestic cat (and other felids) and the domestic dog is not an artifact of domestication, but rather reflects phylogenetic differences between felids and canids as a consequence of their different lifestyles and associated patterns of parental care. These findings emphasize the need for comparative studies to avoid simplistic generalizations from 1 or 2 species across broad taxonomic groups. (PsycINFO Database Record

The role of pelvic and perineal striated muscles in urethral function during micturition in female rabbits.

AIM: To evaluate the role of pelvic and perineal striated muscles on urethral function during micturition. METHODS: Pubococcygeus, or both bulbospongiosus and ischiocavernosus muscles were electrically stimulated during the voiding phase of micturition, and bladder and urethral pressure were simultaneously recorded in urethane anesthetized female rabbits. Bladder and urethral function were assessed measuring urodynamic and urethral pressure variables obtained before and during the stimulation of muscles. Two-tail paired t-tests were carried out in order to determine significant differences (P < 0.05) between groups. RESULTS: Electric stimulation of the pubococcygeus during voiding decreased voiding efficiency and voided volume, whereas residual volume, the duration of voiding, the interval between bladder contraction and urethral resistance increased. Simultaneously, there was an increase in maximum urethral pressure, as well as an increase in the pressure to return to baseline and in the pressure required to close the urethra. Electrical stimulation of bulbospongiosus and ischiocavernosus muscles increased voiding efficiency, voiding duration, and the maximal pressure in bladder. Meanwhile, the maximal urethral pressure, the time related to the rise of urethral pressure, and the urethral pressure required to close the urethra decreased. CONCLUSIONS: The stimulation of pelvic and perineal muscles have opposing roles in urethral function during micturition. Pubococcygeus muscles facilitate urethral closure, while they inhibit bladder contraction. In contrast, bulbospongiosus and ischiocavernosus muscles prevent urethral contraction while they promote bladder contraction.

Olfactory guidance of nipple attachment and suckling in kittens of the domestic cat: Inborn and learned responses.

In 60 kittens (11 litters) from free-ranging domestic cats we investigated the role of chemical cues in facilitating nipple attachment and suckling during the first month of postnatal life when kittens are totally dependent on the mother's milk. Kittens were tested both together and individually on sedated females in different reproductive states. We found (1) that newborn kittens with no suckling experience responded to the ventrum of lactating but not to the ventrum of nonlactating females with search behavior and attached to nipples within minutes; (2) that even in older kittens, nipple attachment depended on females' reproductive state, with virtually no attachments on nonreproducing females, some on pregnant females, the greatest number on early-lactating females, followed by a decline on late-lactating females; and (3) that kittens could locate their particular, most used nipple on their mother but not on a female of similar lactational age, even after eye opening. We suggest that kittens respond from birth with efficient nipple-search behavior to inborn olfactory cues on the mother's ventrum, that emission of these is under hormonal control, but that kittens also quickly learn olfactory cues specific to their own mother and to their own particular nipples.

Scent marking, dominance and serum testosterone levels in male domestic rabbits.

The European rabbit, both in its wild and domesticated forms, has been a pioneer species in the study of mammalian chemical communication, and illustrates well the difficulty of understanding the functional significance of these often complex signals. Here we investigate the performance of one of the rabbit's most conspicuous chemical signaling behaviors, chin marking (chinning), and the hypothesis that this expresses social dominance. In tests of 21 chinchilla-strain sexually mature males we predicted 1) that animals would show marked and stable individual differences in the frequency of chinning, 2) that these differences would correlate with behaviors associated with dominance such as intrasexual mounting, and 3) that individual differences in the frequency of chinning and dominance-related behaviors would correlate with individual differences in a commonly used physiological indicator of dominance, concentration of serum testosterone. Supporting these predictions and consistent with previous reports, animals showed large and stable individual differences in the frequency of chinning which correlated with the behavioral indicators of dominance and less strongly, with serum testosterone. As our animals had been kept in single cages and without direct contact with other males since weaning, these findings raise the question as to how and when during development such differences among individuals arise. We are currently investigating the possible relation between pups' intrauterine position, postnatal competition among littermates for milk and thermally advantageous positions in the litter huddle, and later differences in indicators of dominance such as those reported here.

Reduced nitric oxide synthase 2 (NOS2) promoter activity in the Syrian hamster renders the animal functionally deficient in NOS2 activity and unable to control an intracellular pathogen.

Progressive disease in the hamster model of visceral leishmaniasis, caused by Leishmania donovani, in contrast to infection in mice, mimics the progressive disease observed in untreated humans. During progressive infection in hamsters, there was a vigorous type 1 cellular immune response, which is typically associated with control of infection, suggesting that there was ineffective IFN-gamma-mediated macrophage activation. Indeed, at the site of infection, hamsters did not express NO synthase 2 (NOS2), which is the primary mechanism for control of infection in mice. Furthermore, in striking contrast to mouse macrophages, IFN-gamma-activated hamster macrophages did not did not express NOS2 nor generate NO, and were unable to restrict the replication of intracellular L. donovani. The absent hamster NOS2 expression was not the result of NOS2 gene deletion and the NOS2 cDNA had an intact open reading frame. Furthermore, the impaired transcription of NOS2 mRNA was selective and not due to global impairment of IFN-gamma signaling (members of the IFN-gamma-signaling pathway were expressed and functional and IFN-gamma up-regulated several primary and secondary response genes). Strikingly, the proximal hamster NOS2 promoter, like the human ortholog, had >20-fold less basal and IFN-gamma/LPS-inducible activity than the corresponding mouse promoter. Thus, reduced basal and IFN-gamma-induced activity of the hamster NOS2 transcriptional unit, which is unique to this small animal and similar to the human counterpart, accompanies the inability of the animal to control an intracellular pathogen.

Pathogenicity and protective immunogenicity of cysteine proteinase-deficient mutants of Leishmania mexicana in non-murine models.

This study demonstrates that deletion of cysteine proteinase (CP) genes diminishes pathogenicity of Leishmania mexicana in non-murine experimental host models while preserving immunogenicity. Both cpb and cpa/cpb-deficient lines induced delayed disease onset, smaller lesions and lower parasite burden in hamsters. cpa/cpb-deficient L. mexicana grew more slowly as promastigotes and presented lower infectivity and growth in human mononuclear phagocytic host cells. Protection against homologous challenge comparable to that induced by infection with the virulent wild-type (WT) L. mexicana strain was achieved in the highly susceptible hamster model by immunization with 1000 cpb-deficient promastigotes. CP-deficient L. mexicana elicited significantly lower levels of Th2-associated cytokines IL-10 and TGF-beta than the WT in the primary lesion of hamsters. These findings support the feasibility of using genetically attenuated live Leishmania to achieve protective immunity.

Gender is a major determinant of the clinical evolution and immune response in hamsters infected with Leishmania spp.

In regions where leishmaniasis is endemic, clinical disease is usually reported more frequently among males than females. This difference could be due to disparate risks of exposure of males and females, but gender-related differences in the host response to infection may also play a role. Experimental studies of the influence of gender on Leishmania infection have not included parasites of the subgenus Viannia, which is the most common cause of cutaneous leishmaniasis in the Americas. Mice are not readily susceptible to infection by Leishmania (Viannia) spp., but cutaneous infection of hamsters with L. (V.) panamensis or L. (V.) guyanensis resulted in chronic lesions typical of the human disease caused by these parasites. Strikingly, infection of male hamsters resulted in significantly greater lesion size and severity, an increased rate of dissemination to distant cutaneous sites, and a greater parasite burden in the draining lymph node than infection in female animals. Two lines of evidence indicated this gender-related difference in disease evolution was determined at least in part by the sex hormone status of the animal. First, prepubertal male animals had smaller and/or less severe cutaneous lesions than adult male animals. Second, infection of testosterone-treated female animals resulted in significantly larger lesions than in untreated female animals. The increased severity of disease in male compared to female animals was associated with significantly greater intralesional expression of interleukin-4 (IL-4) (P = 0.04), IL-10 (P = 0.04), and transforming growth factor beta (TGF-beta) (P < 0.001), cytokines known to promote disease in experimental leishmaniasis. There was a direct correlation between the expression of TGF-beta mRNA and lesion size (Spearman's correlation coefficient = 0.873; P < 0.001). These findings demonstrate an inherent risk of increased disease severity in male animals, which is associated with a more permissive immune response.