Effect of formaldehyde on the efficiency of hybridization of DNA immobilized on nitrocellulose filters

DNA isolation and amplification from formaldehyde-fixed animal tissues rich in mucopolysaccharides, pigments, and chitin

Formaldehyde, once the fixative of choice, is a known obstacle to DNA extraction and amplification. However, when fixed tissues contain other problematic compounds such as pigments, mucopolysaccharides, and chitin, and when only small amounts of archival tissues are available, obtaining amplifiable DNA can become extremely challenging. Here, I present a procedure that has enabled me to extract amplifiable DNA from minute specimens of polychaetes successfully; like many other invertebrates, these worms are rich in pigments, mucopolysaccharides, and chitin. This inexpensive procedure can be used to obtain and amplify DNA from miniscule amounts of other similarly-problematic formaldehyde-fixed tissues as well.

Immunocompetence of macrophages in rats exposed to Candida albicans infection and stress

The integration of innate and adaptive immune responses is required for efficient control of Candida albicans. The present work aimed to assess, at the local site of the infection, the immunocompetence of macrophages in rats infected intraperitoneally with C. albicans and exposed simultaneously to stress during 3 days (CaS group). We studied the 1) ability to remove and kill C. albicans, 2) tumor necrosis factor-alpha (TNF-alpha) release, 3) balance of the inducible enzymes NO synthase (iNOS) and arginase, and 4) expression of interleukin (IL)-1beta and IL-1 receptor antagonist (ra) mRNA. Compared with only infected animals (Ca group), the number of colony-forming units was significantly higher in CaS rats (P < 0.01), and the macrophage candidicidal activity was approximately 2.5-fold lower (P < 0.01). Release of TNF-alpha was diminished in both unstimulated and heat-killed C. albicans restimulated macrophages of the CaS group (Ca vs. CaS, P < 0.03 and P < 0.05, respectively). In Ca- and CaS-group rats, the rates for both the arginase activity and the NO synthesis were significantly enhanced. However, the stress exposure downregulated the activity of both enzymes (CaS vs. Ca, P < 0.05). After in vitro restimulation, the IL-1ra/IL-1beta ratio was significantly diminished in CaS-group rats (P < 0.05). Our results indicate that a correlation exists between early impairment of macrophage function and stress exposure.

Self-cleaving circular RNA associated with rice yellow mottle virus is the smallest viroid-like RNA

We report the sequence, structural features, and self-cleaving activity of the small circular RNA (sc-RNA) associated with rice yellow mottle sobemovirus (RYMV). At 220 nucleotides, the RYMV sc-RNA represents the smallest naturally occurring viroid-like RNA currently documented in the literature. It is similar to other circular satellite RNAs (sat-RNAs) and viroids in being G-C-rich with a high level of self-complementarity. The predicted native structure is essentially a rod with one branched terminus. A region of the RYMV sc-RNA, constituting 24% of the sequence, exhibits 89% identity to the sat-RNA associated with the Australasian isolates of lucerne transient streak sobemovirus. This region is also structurally similar in all three RNAs in that it forms the left terminus of each rod. Dimeric runoff transcripts of cloned RYMV sc-RNA undergo efficient autocatalytic in vitro cleavage in the (+) but not the (-) polarity. Analysis of the (+) sequence indicates the presence of a hammerhead ribozyme resembling that of carnation small retroviroid-like RNA and the genomic satellite transcript of newt. Inefficient cleavage of (+) monomeric transcripts, and a short stem III in the hammerhead, are features consistent with a double-hammerhead mode of self-cleavage. The presence of sat-RNA and retroviroid-like structures within a single RNA suggests a possible role for the RYMV sc-RNA as an evolutionary intermediate between these subviral RNAs.