N-glycans harboring the Lewis a epitope are expressed at the surface of plant cells

In plants, N-linked glycans are processed in the Golgi apparatus to complex-type N-glycans of limited size containing a beta(1,2)-xylose and/or an alpha(1,3)-fucose residue. Larger mono- and bi-antennary N-linked complex glycans have not often been described. This study has re-examined the structure of such plant N-linked glycans, and, through both immunological and structural data, it is shown that the antennae are composed of Lewis a (Le(a)) antigens, comprising the carbohydrate sequence Gal beta 1-3[Fuc alpha 1-4]GlcNAc. Furthermore, a fucosyltransferase activity involved in the biosynthesis of this antigen was detected in sycamore cells. This is the first characterization in plants of a Lewis antigen that is usually found on cell-surface glycoconjugates in mammals and involved in recognition and adhesion processes. Le(a)-containing N-linked glycans are widely distributed in plants and highly expressed at the cell surface, which may suggest a putative function in cell/cell communication.

Simple and Sensitive Determination of Urea in Serum and Urine

In this method for serum and urinary urea determination, the same reagent is used without predilution of urine samples. The method is based on the pH increase resulting from the ammonia released by urease hydrolysis of urea. o-Cresolphthalein complexone is used to monitor the pH change colorimetrically. Urea concentration and absorbance at 570 nm are linearly related for concentrations as great as 600 mmol/L for urine samples and 100 mmol/L for serum. There are no clinically significant interferences from physiological substances or drugs, and precision and accuracy are excellent (CV approximately 2%, except at very low concentrations in serum; analytical recovery was 99% in urine, 100% in serum). Results by this method (y) and by the Astra method (x) for urine correlated well (y = 0.991x - 2.87, Sy/x = 9.21, r = 0.994), as did the results by this method and by the total enzymatic method (x') for serum (y = 1.002x' + 0.192, Sy/x' = 0.598, r = 0.997). This method is applicable to automated as well as manual instruments, and one-reagent or two-reagent formats can be used.

Simple and sensitive determination of urea in serum and urine

In this method for serum and urinary urea determination, the same reagent is used without predilution of urine samples. The method is based on the pH increase resulting from the ammonia released by urease hydrolysis of urea. o-Cresolphthalein complexone is used to monitor the pH change colorimetrically. Urea concentration and absorbance at 570 nm are linearly related for concentrations as great as 600 mmol/L for urine samples and 100 mmol/L for serum. There are no clinically significant interferences from physiological substances or drugs, and precision and accuracy are excellent (CV approximately 2%, except at very low concentrations in serum; analytical recovery was 99% in urine, 100% in serum). Results by this method (y) and by the Astra method (x) for urine correlated well (y = 0.991x - 2.87, Sy/x = 9.21, r = 0.994), as did the results by this method and by the total enzymatic method (x') for serum (y = 1.002x' + 0.192, Sy/x' = 0.598, r = 0.997). This method is applicable to automated as well as manual instruments, and one-reagent or two-reagent formats can be used.