Neural plate morphogenesis and axial stretching in “notochord-defective” Xenopus laevis embryos

The morphogenetic movements of neural ectoderm cells associated with neural plate development and neural fold fusion were examined in notochord-defective embryos. Those movements were apparently normal in embryos which displayed a notochord reduced in size or which completely lacked a notochord. Likewise, axial stretching in the anterior-posterior direction was also normal in “notochord-defective” embryos. A role for the anuran notochord in directing neural fold fusion and axial stretching can, therefore, be ruled out.     

Nitrogen Nutrition and Xylem Transport of Nitrogen in Ureide-producing Grain Legumes

Xylem sap composition was examined in nodulated and nonnodulated cowpea (Vigna unguiculata [L.] Walp.) plants receiving a range of levels of NO₃ and in eight other ureide-forming legumes utilizing NO₃ or N₂ as sole source of nitrogen. A ¹⁵N dilution technique determined the proportions of plant nitrogen derived from N₂ in the nodulated cowpeas fed NO₃. Xylem sap composition of NO₃-fed, nodulated cowpea varied predictably with the relative extents to which N₂ and NO₃ were being utilized. The ratios of asparagine to glutamine (N/N) and of NO₃ to ureide (N/N) in xylem sap increased with increasing dependence on NO₃ whereas per cent of xylem nitrogen as ureide and the ratio of ureide plus glutamine to asparagine plus NO₃ (N/N) in xylem sap increased with increasing dependence on N₂ fixation. The amounts of NO₃ and ureides stored in leaflets, stems plus petioles, and roots of cowpea varied in a complex manner with level of NO₃ and the presence or absence of N₂ fixation. All species showed higher proportions of organic nitrogen as ureide and several-fold lower ratios of asparagine to glutamine in their xylem sap when relying on N₂ than when utilizing NO₃. In nodulated (minus nitrate) cowpea and mung bean (Vigna radiata [L.] Wilczek) the percentage of xylem nitrogen as ureide remained constant during growth but the ratio of asparagine to glutamine varied considerably. The biochemical significance of the above differences in xylem sap composition was discussed.     

Biosynthesis of Ureides from Purines in a Cell-free System from Nodule Extracts of Cowpea [Vigna unguiculata (L) Walp.

The synthesis of ¹⁴C-labeled xanthine/hypoxanthine, uric acid, allantoin, allantoic acid, and urea from [8-¹⁴C]guanine or [8-¹⁴C]hypoxanthine, but not from [8-¹⁴C]adenine, was demonstrated in a cell-free extract from N₂-fixing nodules of cowpea (Walp.). The ¹⁴C recovered in the acid/neutral fraction was present predominantly in uric acid and allantoin (88-97%), with less than 10% of the ¹⁴C in allantoic acid and urea. Time courses of labeling in the cell-free system suggested the sequence of synthesis from guanine to be uric acid, allantoin, and allantoic acid. Ureide synthesis was confined to soluble extracts from the bacteroid-containing tissue, was stimulated by pyridine nucleotides and intermediates of the pathways of aerobic oxidation of ureides, but was completely inhibited by allopurinol, a potent inhibitor of xanthine dehydrogenase (EC 1.2.1.37). The data indicated a purine-based pathway for ureide synthesis by cowpea nodules, and this suggestion is discussed.     

以家蚕Bombyx mori L.讨论鳞翅目幼虫头部的形态

鳞翅目幼虫(通称蠋)头部的构造比较特殊,到现在还有各种不同的见解。我们试用家蚕来解释和统一这些不同的见解。     

武功棕色金龟子之研究

金龟子在武功一带发生者,种类颇多,据笔者调查,发生普遍而为害较烈者,计有四种。一为棕色金龟子Rhizotrogus(Amphimallus)sp.;二为酱色金龟子Holo-trichia diomphalia Bates;三为黑色金龟子Trematodes tenebrioides Pall.,本种为     

Cytodifferentiation and membrane transport properties in LK sheep red cells

Young cells produced in LK sheep during rapid hematopoiesis after massive hemorrhage contain more K than the cells which are normally released into the circulation. The K content in these new cells falls to that characteristic of mature LK cells after a few days in the circulation. K transport properties in young and old cells before and after massive bleeding were studied. Young and old cells were separated by means of a density gradient centrifugation technique. Evidence showing that younger cells are found in the lower density fractions is presented. Active transport of K in the lightest fraction as measured by strophanthidin-sensitive influx was four to five times greater in red cells drawn 6 days after massive bleeding while the K leak as measured by strophanthidin-insensitive influx was only slightly larger. No change after bleeding was observed in older cells which had been present in the circulation prior to the hemorrhage. It is concluded that the high K content of young cells produced in LK sheep after bleeding is due to temporary retention of membrane K transport properties characteristic of HK cells. Thus, genetically determined modification of membrane transport properties has been shown to occur in nondividing circulating red cells.     

Associations between mutations and a VNTR in the human phenylalanine hydroxylase gene.

The HindIII RFLP in the human phenylalanine hydroxylase (PAH) gene is caused by the presence of an AT-rich (70%) minisatellite region. This region contains various multiple of 30-bp tandem repeats and is located 3 kb downstream of the final exon of the gene. PCR-mediated amplification of this region from haplotyped PAH chromosomes indicates that the previously reported 4.0-kb HindIII allele contains three of these repeats, while the 4.4-kb HindIII allele contains 12 of these repeats. The 4.2-kb HindIII fragment can contain six, seven, eight, or nine copies of this repeat. These variations permit more detailed analysis of mutant haplotypes 1, 5, 6, and, possibly, others. Kindred analysis in phenylketonuria families demonstrates Mendelian segregation of these VNTR alleles, as well as associations between these alleles and certain PAH mutations. The R261Q mutation, associated with haplotype 1, is associated almost exclusively with an allele containing eight repeats; the R408W mutation, when occurring on a haplotype 1 background, may also be associated with the eight-repeat VNTR allele. Other PAH mutations associated with haplotype 1, R252W and P281L, do not appear to segregate with specific VNTR alleles. The IVS-10 mutation, when associated with haplotype 6, is associated exclusively with an allele containing seven repeats. The combined use of this VNTR system and the existing RFLP haplotype system will increase the performance of prenatal diagnostic tests based on haplotype analysis. In addition, this VNTR may prove useful in studies concerning the origins and distributions of PAH mutations in different human populations.     

Insulin-like growth factor I-like immunoreactivity in serum and tissues of the tilapia, Oreochromis mossambicus

Tilapia serum was acidified with 0.5 M HCl and then chromatographed on an octadecasily-silica column. After washing with 4% acetic acid, the column was eluted with methanol. The eluate was evaporated to dryness. The sample cross-reacted in a human insulin-like growth factor I (IGF-I) radioimmunoassay, suggesting immunochemical similarity to human IGF-I. IGF-I-like immunoreactivity was present at high levels in tilapia liver. Other tissues containing IGF-I-like immunoreactivity included the gonad, kidney, heart, spleen, brain and muscle. The serum IGF-I-like immunoreactivity was attributed to substances with a molecular weight of 9,000 and 45,000 respectively, and it was elevated after treatment with bovine growth hormone and carp pituitary extract.     

Purification and the effect of peptide N-glycosidase F on lysosomal membrane-bound glucocerebrosidase from human cultured fibroblasts.

Glucocerebrosidase was purified from human cultured dermal fibroblasts more than 2200-fold to apparent homogeneity using high performance Alkyl-Superose HR 5/5 hydrophobic interaction and Bio-Sil TSK-250 gel permeation column chromatography. Sodium dodecyl sulfate--polyacrylamide gel electrophoresis and protein staining of the catalytically active and concentrated enzyme fractions from the gel permeation columns revealed the presence of one band of Mr 64,000. The glucocerebrosidase preparation purified to homogeneity was digested with peptide N-glycosidase F that cleaves N-linked oligosaccharide structures from glycoproteins. The molecular weight of glucocerebrosidase after digestion with peptide N-glycosidase F was reduced to Mr 57,000, suggesting that the mature enzyme is a glycoprotein and that N-linked oligosaccharide constitutes a minimum of about 10% of the total molecular weight of the polypeptide. These findings are compatible with the hypothesis that glucocerebrosidase was initially synthesized as a precursor polypeptide which was subsequently glycosylated to become the mature enzyme.