Influence of rice cultivars on CH4 emissions from a paddy field was studied using four Japonica types, two Indica types, and two Japonica/Indica F1 hybrids. In addition, the suppression of CH4 emission by interrupting irrigation at the flowering stage was investigated. Patterns of seasonal variation in CH4 emission rates were similar among the eight cultivars. Two of the Japonica types showed the maximum and minimum CH4 emissions among the cultivars investigated. Neither the number of tillers, shoot length, shoot weight, and root weight correlated with the CH4 emission rates at the tillering and reproductive growth stages. Following temporary interruption of irrigation at the flowering stage, CH4 emission rates decreased drastically and remained at very low levels until the harvesting stage, indicating its great effectiveness for the suppression of CH4 emission from rice paddies.

following correction should be noted. On page 2475, the second line of the left column that reads ". . . were reconstituted with aly͞aly BM cells after lethal irradiation" should read ". . . were reconstituted with aly͞ϩ BM cells after lethal irradiation."Immunology. In the article "Modifying the sequence of an immunoglobulin V-gene alters the resulting pattern of hypermutation," by Beatriz Goyenechea and César Milstein, which appeared in number 24, November 26, 1996, of Proc. Natl. Acad. Sci. USA (93, 13979-13984), the following revision should be noted: The formula at the bottom of the first column of page 13980 was misprinted. The correct formula is:FIG. 6. Three-dimensional structure of rQR1 in complex with FAD and NADP ϩ (12). The C-terminal 43 amino acids (232-274) are shown in red (Left), and have been truncated at the arrow (Right). Different colors of the backbone indicate the two different subunits. It can be seen that the truncated portion of QR2 is critical for binding of the pyrophosphate moiety of the NAD(P)H cofactor. Note that the contact regions between the enzyme and FAD are presumably preserved in QR2 (Right), consistent with the tight binding of FAD. The structural comparison between rQR1 and hQR2 is appropriate since the homology between rQR1 and hQR1 is very high (85% identity). CorrectionsProc. Natl. Acad. Sci. USA 94 (1997) Contributed by Robert A. Good, January 3, 1997 ABSTRACTThe development of T cells within the thymus is largely dependent on intact cortical and medullary epithelial cells. However, it has been reported that positive selection of natural killer antigen 1.1 ؉ (NK1.1 ؉ ) T cell antigen receptor (TCR)-␣͞␤ ؉ thymocytes recently identified among CD4 ؉ 8

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A 50-year