Time and sequence of the replacement of the deciduous by the permanent dentition in dogs and its applicability for age estimation.

This study investigated the influence of several covariates on the time and sequence of permanent dentition emergence following exfoliation of the deciduous teeth in puppies. The aim was to determine whether the emergence of permanent dentition can be used to assess whether a puppy that is traded across borders in the EU has reached the legally required minimum age of 15 weeks. The events were evaluated in a longitudinal study, with some cross-sectional observations, of 440 puppies belonging to 82 breeds. No significant differences were found between the left and right sides of a puppy's dentition nor between male and female puppies. Breed size and skull type had a significant impact: both the appearance and the completion of tooth eruption occurred considerably later in small or toy breeds and brachycephalic skull type breeds. The sequence of emergence differed little between maxillary or mandibular quadrants or between breeds. The first emerging elements were the maxillary first premolars or first incisors or the mandibular first incisors. The emergence of a permanent tooth usually occurred within 3 days before or after exfoliation of its precursor, except for the canines, which demonstrated a wider tooth replacement interval. This study presents standards for age assessment based on the emergence of permanent dentition for breeds of different sizes, using median ages or cumulative emergence percentages. However, the legal age determination of puppies with an assumed age of 15 weeks cannot be performed based on permanent dentition emergence, as this occurred at a later age in a large proportion of dogs (at least 95%) in our studied population. The probability of being at least 15 weeks old when at least one maxillary tooth has emerged was at least 72.25%, depending on breed size.

Dynamic Immune Response to Vibriosis in Pacific Oyster Crassostrea gigas Larvae during the Infection Process as Supported by Accurate Positioning of GFP-Tagged Vibrio Strains.

As the immune system is not fully developed during the larval stage, hatchery culture of bivalve larvae is characterized by frequent mass mortality caused by bacterial pathogens, especially Vibrio spp. However, the knowledge is limited to the pathogenesis of vibriosis in oyster larvae, while the immune response to pathogenic microorganisms in this early life stage is still far from being fully elucidated. In this study, we combined green fluorescent protein (GFP)-tagging, histological and transcriptomic analyses to clarify the pathogenesis of experimental vibriosis and the mechanisms used by the host Pacific oyster Crassostrea gigas larvae to resist infection. The Vibrio strains first colonized the digestive system and rapidly proliferated, while only the transcription level of IκB kinase (IKK) and nuclear factor κB (NF-κB) associated with signaling transduction were up-regulated in oyster at 18 h post challenge (hpc). The mRNA levels for integrin ß-1, peroxinectin, and heat shock protein 70 (HSP70), which are associated with phagocytosis, cell adhesion, and cytoprotection, were not upregulated until 30 hpc when the necrosis already happened in the larval digestive system. This suggested that the immunity in the early stages of C. gigas is not strong enough to prevent vibriosis and future research may focus on the strengthening of the gastrointestinal immune ability to defend vibriosis in bivalve larvae.