The basis of the paradoxical reversal of temperature perception commonly described in ciguatera poisoning has never been defined. The sensations experienced are described as tingling, burning, "dry ice-like", smarting, and "electric". Studies have demonstrated that these types of sensations are generated in C-polymodal nociceptor fibers in skin and deep structures and the intensity of these sensations depends on the intensity of discharge in these fibers. Ciguatoxin causes persistent sodium channel opening in nerve membrane resulting in oscillations in membrane potentials and runs of spontaneous discharges. Studies on ciguatera victims in which their hands were immersed in water baths ranging from 0 degree C to 50 degrees C, suggest the paradoxical sensory discomfort experienced is, most likely, a result of an exaggerated and intense nerve depolarization occurring in peripheral small A-delta myelinated and in particular, C-polymodal nociceptor fibers. Gross temperature perception was found to be intact in ciguatera poisoning and reversal of temperature does not occur.
The impact of dietary composition and prebiotics, in promoting the growth of beneficial groups of gut bacteria, is increasingly apparent. Using Illumina MiSeq sequencing of bacterial 16S rRNA genes, this study has aimed to characterize and compare the establishment of the gastrointestinal microbiota in dairy calves given two different commercial milk replacer (MR) diets. MR1 and MR2 contain different levels of macronutrients such as protein and fat. Moreover, differences in manufacturing methods infer that MR2 may contain a greater proportion of conjugated milk oligosaccharides (OS), while MR1 contains more free milk OS. A total of 10 dairy calves, five in each group, were assigned to one of the two MR diets. Freshly voided fecal samples were taken at 0, 7, 14, 28, and 49 days after first consumption of milk replacer. The relative abundance of two individual Bifidobacterium species, which are known to utilize milk OS, and Faecalibacterium prausnitzii were significantly higher at day 7 in the fecal microbiome of calves fed MR2 compared with MR1. These commensal bacteria are widely regarded as probiotic organisms that confer a health benefit on the host. Our findings suggest that the composition of bovine milk replacers can have significant effects on the establishment of the gut microbiota in pre-weaned (neonatal) dairy calves. Better understanding of milk composition-microbiota-host interactions in early life will inform targeted interventions to increase growth and reduce mortality in young animals.
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