Relation between Leaf Age and Nitrogen Incorporation in the Leaf of the Rice Plant (Oryza sativa L.)

The relation between leaf age and the incorporation of nitrogeninto the leaf was examined in the 13th leaf blade of the riceplant, Oryza sativa L., after feeding it ¹⁵N-labelled ammoniumsulfate. The incorporation of nitrogen into the leaf was activeup to the maximum leaf nitrogen content; thereafter it decreasedquickly. At the beginning of senescence, when the nitrogen contentof the leaf had begun to decrease, the incorporation of ¹⁵Ndecreased to 28% of the value during development. At the middlestage of senescence, when the nitrogen content had decreasedto half the maximum, the incorporation was 13%. The incorporation of ¹⁵N into soluble proteins was examinedby gel filtration on Sephadex G-200. During development, largeamounts of ¹⁵N were incorporated into the ribulose bisphosphatecarboxylase-rich fraction. As the leaf aged, the incroporationof ¹⁵N into this fraction decreased more sharply than it didin other fractions. This tendency was more pronounced at thelate stage of senescence. We concluded that the amounts andkinds of protein synthesized in a leaf are closely related toleaf age. (Received November 24, 1981; Accepted June 17, 1982)     

Action of Single-strand-specific S1 Endonuclease on Locally Altered Structures in Double-stranded DNA

The cleavage of double-stranded DNA by S1 endonuclease was studied by sucrose density gradient centrifugation analysis. The enzyme introduced no single-strand breaks into native T7 DNA under conditions where heat-denatured T7 DNA was completely degraded. By using enzyme at about 6 times higher the amount required for complete degradation of the heat-denatured DNA, it was possible to make a few single-strand breaks in native T7 DNA. Under the conditions where native T7 DNA is absolutely resistant to the enzyme, the susceptibility of locally altered structures naturally present and/or artificially induced in native double-stranded DNA to the enzyme was studied. It was evidenced that S1 endonuclease can cleave circular covalently closed, superhelical fl RFI DNA, depurinated T7 DNA, bleomycin-treated T7 DNA containing internal single-strand breaks, but not cleave intercalating drug-bound T7 DNA.     

Blätteralkohol (XVI)Blätteralkohol (XVII)

2-Methyl-4, 6-cyclohexadienaldehyde and n-butyraldehyde were treated with sodium in p-xylene to yield the aromatized “leaf alcohol reaction” product, 2-methyl-benzylalcohol, in a better yield than that with the cyclohexadienaldehyde alone. n-Butyric acid isolated from the reaction mixture unequivocally showed the operation of the “crossed Cannizzaro disproportionation” in this reaction, aliphatic aldehyde serving as the hydride donor. 2-Propyl-5-ethyl-4, 6-cyclohexadienaldehyde was obtained by the NaOH/H₂O-EtOH Michael-Aldol condensation of leaf aldehyde, gave 2-propyl-5-ethyl-benzylalcohol along with caproic acid.

On the basis of “leaf alcohol-reaction” mechanism, it was obtained following benzyl-alkohols; 2-methyl-, 2-propyl-, 2-methyl-5-ethyl-, 2-propyl-5-ethyl-benzylalcohol, from leaf alcohol and crotylalcohol.     

Metabolic conversion of 24-methyl-Delta25-cholesterol to 24-methylcholesterol in higher plants

Feeding of chemically synthesized [27-13C]codisterol ([27-13C]2), [27-13C]24-epicodisterol ([27-13C]3), [23,24-2H2]codisterol ([23,24-2H2]2), and [26,27-2H6]24-methyldesmosterol ([26,27-2H6]8) to Oryza sativa cell cultures, followed by MS and NMR analysis of the biosynthesized dihydrobrassicasterol (9)/campesterol (10), revealed that both (24R)- and (24S)-epimers of 24-methyl-Delta25-cholesterol (2/3) were converted to 9 and 10 via the common intermediate 24-methyldesmosterol (8).     

Glycosylation and Cell Surface Expression of Kv1.2 Potassium Channel are Regulated by Determinants in the Pore Region

Voltage-gated K⁺ channels contain six membrane spanning segments and a pore-forming domain. We used site-directed mutation to examine the role of specific amino acids in the extracellular region of the pore in Kv1.2. When expressed in CHO cells, a K⁺ current was not observed for mutants S356A, S360A, T383A and T384A. However, coexpression of the Kvβ2 subunit and the S360A mutant resulted in a robust peak current. Immunocytochemistry for Kv1.2 showed staining throughout the cytoplasm in cells coexpressing the β2 and S360A, whereas only the perinuclear region was stained in cells expressing the S360A mutant. Western blotting revealed that the major immunoreactive protein in wild-type- and mutant-expressing cells is 60-kDa, but 87-kDa bands were also detected in cells expressing wild-type Kv1.2 and cells coexpressing β2and S360A. These results suggest that amino acids in the pore region help regulate ion permeability or cellular trafficking by affecting glycosylation of Kv1.2.     

Crossreaction with an anti-Bax antibody reveals novel multi-endocrine cellular antigen.

We found a novel protein that has crossreactivity with a polyclonal anti-Bax antibody (SCBAX antibody). The protein was localized exclusively in the endocrine cells of hypothalamus, pituitary gland, and pancreatic islets. Immunohistochemical (IHC) double labeling revealed that the cells showing crossreactivity with this antibody corresponded precisely to oxytocin neurons and ACTH, alpha-MSH, and glucagon cells in rat and gerbil. By immunoelectron microscopy, the protein was localized predominantly in and just around the secretory granules in the cytoplasm but not in the mitochondria. Double-labeling IHC with the anti-Bax SCBAX antibody and two anti-Bax monoclonal antibodies (MAbs) showed that cells stained with the anti-Bax SCBAX antibody were not stained with anti-Bax MAbs except for very few cells (probably apoptotic cells). Western blotting analysis revealed that the molecular mass of the protein was approximately 55 kD, which differs from that of Bax protein (21 kD). These findings indicate that the anti-Bax SCBAX antibody recognizes not only pro-apoptotic Bax protein (a 21-kD mitochondrial protein) but also an unknown substance present in one endocrine cell group in each endocrine organ. Therefore, the protein is designated as multi-endocrine cellular antigen (MECA). MECA is probably a 55-kD protein secreted from the particular differentiated cell groups of endocrine tissues.