Scholarship in Review 84(2)

Scholarship in Review was a magazine highlighting research and scholarly activities at Central Washington University, published by the Office of Graduate Studies and Research.https://digitalcommons.cwu.edu/scholarship_in_review/1000/thumbnail.jp

Quantitation of \u3ci\u3eGiardia\u3c/i\u3e cysts by membrane filtration.

A method of fixing and staining Giardia cysts on a membrane filter is reported. This procedure appears to be a reliable method for the recovery and detection of cysts and also for the determination of cyst densities. Evaluation and possible applications of the technique are described

Migratory birds of central Washington as reservoirs of \u3ci\u3eCampylobacter jejuni\u3c/i\u3e

Migratory ducks, Canada geese, and sandhill crane from the Pacific North American Flyway have been screened for Campylobacter spp. Samples (298) from these birds were examined and the incidence of Campylobacter spp. in the samples were as follows: sandhill crane (Grus canadensis tabida), 81 %; ducks (Aythya collaris, Anas carolinensis, Aythya americana, and Anas platyrhynchos), 73%; and Canada geese (Branta canadensis), 5%. All isolates were identified as Campylobacter jejuni. To our knowledge this is the first report of the isolation of C. jejuni from sandhill crane. The high frequency of isolation in both the sandhill crane and migratory ducks indicated that these bird populations may play a significant role in the dissemination of the bacterium. Because of their migratory habits, these birds may be particularly important in spreading C. jejuni to remote areas

Small rodents and other mammals associated with mountain meadows as reservoirs of \u3ci\u3eGiardia\u3c/i\u3e spp. and \u3ci\u3eCampylobacter\u3c/i\u3e spp.

Sixty-five percent (469 of 722) of the fecal samples collected from small rodents in the central Washington Cascade mountains were positive for Giardia spp. Trapping studies showed that microtines of the genus Microtus were heavily infected with the parasite. Morphologically the cysts and trophozoites were of the Giardia duodenalis type. Small-rodent populations appear to maintain their infection throughout the year. Our data suggest that there is no difference in the percentage of positive animals in areas receiving a lot of human use as opposed to animals in those areas receiving very little or no human use. Giardia spp. were also found in elk and beaver fecal samples. Campylobacter spp. were recovered infrequently from the small rodents inhabiting alpine meadows. Of 551 specimens cultured, less than 1% were positive for the bacterium, and the isolates were identified as Campylobacter coli. Water voles were susceptible to a human isolate of Campylobacter jejuni and shed the bacterium for several weeks. C. jejuni was also isolated from a bear fecal sample collected from a protected watershed. Our studies indicate that microtines and possibly other small rodents inhabiting mountain meadows have a potential to act as a reservoir for both Giardia spp. and Campylobacter spp. Because these animals may carry human pathogens, they should be included in animal surveys designed to assess the health risks associated with mountain watersheds

The Conserved, 5' Termini of RNAs 1 and 2 of Tomato aspermy virus are Dispensable for Infection but Affect Virulence

The original publication can be found at www.springerlink.comThe 5 terminus of each of the three genomic RNAs (RNAs 1, 2 and 3) of Tomato aspermy virus (TAV) begins with the sequence 5-GUUU, which is also shared by a number of other viruses. Mutagenic analyses showed that the 5-GUUU sequence of RNAs 1 and 2 of TAV was dispensable for viral infection and did not prevent symptom induction. On the other hand, substitution of U at position 5 for G in RNA 1, but not RNA 2, induced veinal necrosis symptoms in Nicotiana glutinosa. The mutants constructed included insertion of UUU into the 5-GUUU sequence of TAV RNAs 1 and/or 2. All RNA 2 mutants induced more severe symptoms than viral RNAs containing either mutated RNA 1 or most combinations of mutated RNAs 1 and 2. Some combinations of mutated RNAs 1 and 2 also induced veinal necrosis in N. glutinosa. Virulence was unrelated to the levels of viral RNA accumulation. Sequence analysis of progeny viral RNAs showed that only the mutant viral RNAs with a G to U substitution in RNA 1 and the deletion of the 5-GUUU in both RNAs 1 and 2 were able to maintain the same sequence as the inoculum. The other mutants either reverted to the wildtype sequence or underwent further deletion or insertion. None of the constructed mutants were able to compete for accumulation with the wildtype virus after co-inoculation to the plant species tested.Bu-Jun Shi, Peter Palukaitis and Robert H. Symon

Aldosterone increases KCa1.1 (BK) channel-mediated colonic K+ secretion

Mammalian K+ homeostasis results from highly regulated renal and intestinal absorption and secretion, which balances the unregulated K+ intake. Aldosterone is known to enhance both renal and colonic K+ secretion. In mouse distal colon K+ secretion occurs exclusively via luminal KCa1.1 (BK) channels. Here we investigate if aldosterone stimulates colonic K+ secretion via BK channels. Luminal Ba2+ and iberiotoxin (IBTX)-sensitive electrogenic K+ secretion was measured in Ussing chambers. In vivo aldosterone was augmented via a high K+ diet. High K+ diet led to a 2-fold increase of luminal Ba2+ and IBTX-sensitive short-circuit current in distal mouse colonic mucosa. This effect was absent in BK α-subunit-deficient (BK−/−) mice. The resting and diet-induced K+ secretion was stimulated by luminal ionomycin. In BK−/− mice luminal ionomycin did not stimulate K+ secretion. In vitro addition of aldosterone likewise triggered a 2-fold increase in K+ secretion, which was inhibited by the mineralocorticoid receptor antagonist spironolactone and the BK channel blocker IBTX. Semi-quantification of mRNA from colonic crypts showed up-regulation of BK α- and β2-subunits in high K+ diet mice. The BK channel could be detected luminally in colonic crypt cells by immunohistochemistry. The expression level of the channel in the luminal membrane was strongly up-regulated in K+-loaded animals. Taken together, these data strongly suggest that aldosterone-induced K+ secretion occurs via increased expression of luminal BK channels