Development of the neonatal rat as a model for Sudden Infant Death Syndrome: cardiorespiratory effects of ethanol

The current pathogenesis of Sudden Infant Death Syndrome (SIDS) is unknown. Elevated endogenous ethanol production by gastrointestinal yeast has been proposed as a possible mechanism for SIDS. To investigate the role of ethanol in SIDS, three studies were undertaken. In the first study, transcutaneous blood gas technology was evaluated for repeated monitoring of arterial blood gases. The second study identified the cardiorespiratory responses to inhaled CO2 challenge in juvenile rats, to determine the age corresponding to the age range of peak incidence of SIDS in human infants. Finally, utilizing the optimized juvenile rat model, the cardiorespiratory responses to ethanol and CO2 challenge were examined. The following observations were made: 1) A transcutaneous probe temperature of 44.5¡ãC provided the best correlation with arterial blood gas levels, though extended skin contact caused thermal burns. 2) The transcutaneous probe could be maintained in place for 3 hours utilizing probe temperatures of 44¡ãC (adults) and 42¡ãC (juveniles) without producing thermal burns, while providing modest correlation between arterial and transcutaneous CO2. 3) On post embryonic (PE) days 30 & 31, pups exhibited higher heart rates and responded more slowly to and recovered slower from CO2 challenge versus older ages tested. 4) On PE days 30 and 31, pup respiratory rate was unchanged in response to 10 % inhaled CO2 challenge, whereas older animals decreased respiratory rate approximately 38 %. 5) Simultaneous challenge with ethanol and CO2 inconsistently elevated transcutaneous CO2 to levels over those observed for CO2 challenge alone. 6) Respiratory responses to modest levels of CO2 and ethanol were ineffective in lowering transcutaneous CO2 levels. 7) Ethanol alone elevated transcutaneous CO2 levels without a concurrent depression of respiration. In summary, transcutaneous blood gas methodology provides an effective means of serially monitoring changes in arterial CO2 concentrations in small rodents. Juvenile rats of PE age 29 - 31 days (¡Öpost natal days 8- 10) provide a useful rodent model for future investigations into the pathogenesis of SIDS. Finally, low blood ethanol concentrations may exacerbate the effects of inhaled CO2 and should be further investigated as a mechanism for the pathogenesis of SIDS

Prevalence and Infection Load Dynamics of Rickettsia felis in Actively Feeding Cat Fleas

Background: Rickettsia felis is a flea-associated rickettsial pathogen recurrently identified in both colonized and wild-caught cat fleas, Ctenocephalides felis. We hypothesized that within colonized fleas, the intimate relationship between R. felis and C. felis allows for the coordination of rickettsial replication and metabolically active periods during flea bloodmeal acquisition and oogenesis. Methodology/Principal Findings: A quantitative real-time PCR assay was developed to quantify R. felis in actively feeding R. felis-infected fleas. In three separate trials, fleas were allowed to feed on cats, and a mean of 3.9610 6 R. felis 17-kDa gene copies was detected for each flea. A distinct R. felis infection pattern was not observed in fleas during nine consecutive days of bloodfeeding. However, an inverse correlation between the prevalence of R. felis-infection, which ranged from 96 % in Trial 1 to 35 % in Trial 3, and the R. felis-infection load in individual fleas was identified. Expression of R. felis-infection load as a ratio of R. felis/C. felis genes confirmed that fleas in Trial 3 had significantly greater rickettsial loads than those in Trial 1. Conclusion/Significance: Examining rickettsial infection dynamics in the flea vector will further elucidate the intimate relationship between R. felis and C. felis, and facilitate a more accurate understanding of the ecology and epidemiology of R. felis transmission in nature

Effects of fenbendazole on fecal microbiome in BPH/5 mice, a model of hypertension and obesity, a brief report.

Fenbendazole (FBZ) is a common antiparasitic treatment used in research rodent colonies for biosecurity purposes. The effect of this compound has been studied in C57 mice, but never before in a strain of mice that has co-morbidities, such as the blood pressure high (BPH)/5. The BPH/5 mouse is an inbred genetic model of hypertension. While both male and female BPH/5 have high blood pressure, there is a metabolic sexual dimorphism with females displaying key features of obesity. The obese gut microbiome has been linked to hypertension. Therefore, we hypothesized that fenbendazole treatment will alter the gut microbiome in hypertensive mice in a sex dependent manner. To test the influence of FBZ on the BPH/5 gut microbiota, fecal samples were collected pre- and post-treatment from adult BPH/5 mice (males and non-pregnant females). The mice were treated with fenbendazole impregnated feed for five weeks. Post-treatment feces were collected at the end of the treatment period and DNA was extracted, and the V4 region of 16S rRNA was amplified and sequenced using the Illumina MiSeq system. The purpose was to analyze the fecal microbiome before and after FBZ treatment, the results demonstrate changes with treatment in a sex dependent manner. More specifically, differences in community composition were detected in BPH/5 non-pregnant female and males using Bray-Curtis dissimilarity as a measure of beta-diversity (treatment p = 0.002). The ratio of Firmicutes to Bacteroidetes, which has been identified in cases of obesity, was not altered. Yet, Verrucomicrobia was increased in BPH/5 males and females post-treatment and was significantly different by sex (treatment p = 5.85e-05, sex p = 0.0151, and interaction p = 0.045), while Actinobacteria was decreased in the post-treatment mice (treatment p = 0.00017, sex p = 0.5, interaction p = 0.2). These results are indicative of gut dysbiosis compared to pre-treatment controls. Lactobacillus was decreased with FBZ treatment in BPH/5 females only. In conclusion, fenbendazole does alter the gut microbial communities, most notable in the male rather than female BPH/5 mouse. This provides evidence that caution should be taken when providing any gut altering treatments before or during mouse experiments