UV linear dichroism of thymine, uracil, cytosine, cytidine, guanine, guanosine, and adenine partially oriented in stretched poly(vinyl alcohol) film was measured in the 215-320-nm region to determine the directions of electronic transition moments. IR dichroism was measured in the same stretched films in the region 1900-1400 cm"1 to obtain information about the molecular orientation tensor ((cos Zi cos Zj)\. The first -* transitions of thymine (266 nm) and uracil (260 nm) were found to be polarized at about -31°and -11°, respectively, with respect to the -04 line toward the N3 atom, and the first (268 nm) and second (240 nm) transitions of cytosine directed at 25°and 6°. The first (280 nm) and second (248 nm) transitions of guanine were obtained at 4°a nd -88® relative to the N3-C6 line toward the atom, and the second (263 nm) and third (235 nm) transitions of adenine directed at 9® and -75®. The results are in reasonably good agreement with crystal studies.

Myo-inositol is a major compatible osmolyte in the renal medulla that is accumulated under hypertonic conditions via the Na+/myo-inositol cotransporter (SMIT). We have recently reported that SMIT is predominantly present in the thick ascending limb of Henle (TAL) and is strongly induced by acute NaCl loading, suggesting an important role of myo-inositol in this nephron segment. In the present study, we sought to examine in vivo effects of inhibition of myo-inositol transport using a transport inhibitor, 2-O, C-methylene-myo-inositol (MMI). Intraperitoneal injection of MMI caused acute renal failure in the rats. Serum creatinine and urea nitrogen were significantly increased 12 hours after MMI injection. Morphologic study revealed that the tubular cells were extensively injured in the outer medulla. A considerable number of the tubular cells were injured in the cortex as well. Immunohistochemical study for Tamm-Horsfall protein (THP), which was used for identification of the TAL cells, showed that THP-positive cells were predominantly injured. The tubular injury apparently appeared to worsen when high concentration of NaCl was injected with MMI. Administration of myo-inositol prevented acute renal failure and improved the tubular injury after MMI injection. Furthermore, supplementation of betaine, another osmolyte in the TAL cells, partially prevented the toxic effects of MMI. These results suggest that myo-inositol play a crucial role in the TAL regarding osmoregulation of the cells.

The present study demonstrates that (i) apoptosis is involved in the hypertonicity-induced cell death in MDCK cells; (ii) caspase-3, -8, and -9 may contribute to the apoptosis; and (iii) betaine has protective effect on the hypertonicity-induced apoptosis.

SynopsisWe have calculated the uv linear dichroism for the A-and B-forms of DNA using a-a* transition moments and band components determined from the free DNA bases. The reduced dichroism (LDR) as a function of davelength is estimated in the 220-300-nm region, for both the oriented-gas model and a simple exciton model. For B-form DNA, LDR is obtained to -1.48s ( S being the orientation factor) over the whole wavelength region by both models. For A-form DNA, LDR is not constant, but changes monotonically from about -1.15s at 220 nm to about -1.35s to -1.45s at 300 nm, depending on base combination and degree of interaction (-1.35s for the oriented gas). It is emphasized that a common assumption of a single "effective" transition moment of the principal band at 260 nm may not generally be made because of the extensive overlap of differently polarized bands. The possibility of using the reduced dichroism curve for characterizing the secondary structure of DNA is discussed.

These results suggest that HWI reduces TGF-beta mRNA expression in medullary interstitium and ameliorates tubulointerstitial injury in rats with reduced renal mass.