Immunity

Fig. 1 Negative stain electron micrograph of rotavirus.

disaccharides must be broken down to monosaccharides as only monosaccharides can be absorbed. If they accumulate in the gut lumen then they hold water leading to an osmotic diarrhea. Recently, it has been found that NSP4 or even a 22-amino acid fragment from it can induce diarrhea in neonatal mice when administered orally or intraperitoneally.[5] It is thought that NSP4 acts as an exterotoxin causing diarrhea by opening a cellular cation channel which causes an increase in intracellular [Ca2+], activation of adenyl cyclase, and cAMP-dependent Cl_ secretion. This causes a secretory diarrhea in a manner analogous to some bacterial enterotoxins.[6] Rotavirus is released from enterocytes by lysis and the increased cytoplasmic [Ca2+] causes enterocyte death by oncosis.

Rotavirus diarrhea lasts on average 5-6 days and seems to resolve as the virus exhausts enterocytes to infect when it reaches the colon. In addition, it appears that T-cell-mediated immunity is important in resolution, at least in mice. Natural rotavirus infection protects against subsequent symptomatic infection but to a lesser extent against virological infection. It is likely that we will all experience a rotavirus infection, usually asymptomatic, every 2-3 years. However, immunity does appear to decrease with age and rotavirus outbreaks are increasingly reported in elderly patients. In a cohort study in Mexican infants the risks of rotavirus disease and rotavirus infection after one, two, or three prior episodes of infection were 0.23, 0.17, or 0.08, and 0.62, 0.40, or 0.34, respectively.1-7-1 However, it is not clear which are the most important correlates of immunity. In several studies, serum IgG and IgA rotavirus antibodies correlate best with protection. Fecal antirota-virus IgA (which reflects duodenal IgA) also reflected protection against infection.

Table 1

Rotavirus genome and gene products

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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