Inhibition of mugineic acid-ferric complex uptake in barley by copper, zinc and cobalt

The interfering effects of copper, zinc, and cobalt on the uptake of mugineic acid-ferric complex were studied in barley ( Hordeum vulgare , cv. Minorimugi) grown in nutrient solution. Short-term uptake experiments of 3 h were performed utilizing both ionic and mugineic acid-complex forms of each metal at two different concentrations. Copper was most effective in decreasing iron uptake when added in an ionic form at either concentration. The inhibition order at higher concentrations followed Cu(II) > Zn(II) ≥ Co(II), Co(III), which is consistent with the stability constants of these metal complexes with mugineic acid. The displacement of iron from its mugineic acid complex by these metals is suggested as a probable explanation for the decreased iron uptake. The inhibitory effect of metal complexes with mugineic acid on iron uptake was only found in cases with higher concentrations of Cu(II) and Zn(II) complexes. Deformation of the specific iron transport system in the plasma membrane due to their adsorption may be responsible for this effect.     

W-heterochromatin of chicken; its unusual DNA components,late replication,and chromatin structure

About 65% of DNA in the chicken W chromosome has been shown to consist ofXhoI andEcoRI family repetitive sequences. These sequences showed remarkable delay in the electrophoretic mobility at low temperature on a polyacrylamide gel. Three dimensional structures of the 0.7-kbXhoI and the 1.2-kbEcoRI family repeating units were estimated to be irregular solenoids using a computer program based on wedge angles of all the 16 dinucleotide steps. Fluorescencein situ hybridization demonstrated that these two family sequences were localized in a major heterochromatic body in an interphase nucleus. Incorporation of bromodeoxyuridine into the W chromosome in the synchronous culture of MSB-1 cells occurred about 1 h later than the peak of S phase. The chromatin structure formed alongXhoI andEcoRI family sequences was suggested to be different from the total chromatin or chromatin containing the β-actin gene sequence in that the linker DNA lengths of the former were significantly longer. Fractionation of theHaeIII-digested MSB-1 nuclei yielded a chromatin fraction in whichXhoI family sequences were partially enriched. Several DNA-binding proteins showing higher affinity for theXhoI family sequence were present in this fraction.     

Long-term follow up of patients with common variable immunodeficiency treated with intravenous immunoglobulin: Reevaluation of intravenous immunoglobulin replacement therapy

Five patients with common variable immunodeficiency treated in our hospital between December 1979 and December 1990 were given six kinds of intravenous immunoglobulin preparations (pepsin treated, S-sulfonated, polyethylene glycol treated, pH4 treated, alkylated, and pH4.25 formulation preparation) for replacement therapy. Duration of the therapy ranged from 7.6 to 11 years. Incidences of fever and acute infections were variable among patients, but no significant differences were seen in the incidences among periods given each preparation. Three cases revealed abnormal pulmonary functions in tests. Adverse reactions were rarely seen in our study periods, and no severe reactions were observed. No significant differences were seen in incidences of adverse reactions. Postinfusion levels of serum complement slightly decreased from preinfusion levels. However, the decrease in complement was not related to any adverse reaction. No long-term complications such as transmission of hepatitis have been observed. Our data suggest that no obvious differences exist between the efficacy and safety of each IVIG preparation. Differences of efficacy of IVIG replacement therapy may be due to the variable pathophysiology of each patient.Abbreviations CVID common variable immunodeficiency - IVIG intravenous immunoglobulin     

Elucidation of the mechanism enhancing the avidity of lectin with oligosaccharides on the solid phase surface

The mechanism underlying molecular recognition of lectins waselucidated by a novel solid phase binding assay system basedon surface plasmon resonance. When the apparent affinities ofinteractions between chitooligosaccharides and wheat germ agglutininwere compared between lectin-immobilized and oligosaccharide-immobilizedassay systems, the affinity constants (Ka) calculated for theformer system were in good agreement with the previously reportedvalues measured in solution. On the other hand, in the lattersystem, the calculated Ka could be more than 10,000 times higherthan the values in solution at lower lee tin concentrations.To elucidate the reason for this, we systematically investigatedthe effects of the oligosaccha-ride immobilized density andthe lectin valence on the apparent affinity in the oligosaccharide-immobilizedassay system. Both the apparent association (k_ass) and dissociationrate constants (k_diss) showed a tendency to decrease as theoligosaccharide density increased. This effect was most remarkablefor the interaction possessing an extremely fast intrinsic K_ass.Oligomerization of lectin enhanced the avidity due to a significantreduction in k_diss. These phenomena could be explained by consideringthe nonhomogeneous conditions under which binding occurred.The reaction in a nonhomogeneous state is limited by the masstransport effect, and the effect of rebinding becomes so largethat it cannot be disregarded. These findings are the firstto demonstrate the importance of the mass transport effect inmodulating the affinity of lectin for oligosaccharides on asolid phase surface. avidity clustering effect lectin mass transport surface plasmon resonance     

RAD51 homologues in Xenopus laevis: two distinct genes are highly expressed in ovary and testis

The RAD51 gene is a eukaryotic counterpart of the Escherichia coli recA gene which is involved in genetic recombination. Two distinct Xenopus laevis RAD51 cDNA clones (XRAD51.1 and XRAD51.2) were isolated from an oocyte cDNA library using the human RAD51 cDNA (HsRAD51) as a probe. Sequence analysis revealed that 98.2% of the amino-acid residues were identical between XRAD51.1 and XRAD51.2, and that both were 95% identical to HsRAD51. Both of the XRAD51 genes were expressed at a higher level in ovary and testis than in other somatic tissues, suggesting their involvement in meiotic recombination. The expression of XRAD51.1 was about eightfold in excess of that of XRAD51.2 in all of the tissues examined. Analysis of the rates of synonymous substitution in the coding sequences of the two XRAD51 suggests that these two genes diverged about 50 million years ago. The structural similarities of the XRAD51 proteins to RecA in E. coli and Rad51 in yeasts or vertebrates are discussed.     

Production of monoclonal antibodies and development of an ELISA for solamargine

The ratio of hapten and bovine serum albumin in an antigen conjugate was determined by matrix-assisted laser desorption/ionization mass spectrometry. A hybridoma secreting monoclonal antibodies against solamargine was produced by fusing splenocytes immunized with a solamargine-bovine serum albumin conjugate with HAT-sensitive mouse myeloma cell line, P3-X63-Ag8-653. Extensive cross-reaction of anti-solamargine antibodies against solasonine appeared. Aglycone of solamargine, solasodine cross-reacted with anti-solamargine antibodies resulting in a 43.8% cross-reaction. Insignificant cross-reaction appeared with tomatine (2.06%). The full measuring range of the assay extends from 57.5 pmol ml^–1 to 11.5 nmol ml^–1 of solamargine.     

Selective solubilization and purification of cell-surface concanavalin A-binding glycoproteins from Novikoff hepatocellular carcinoma cells

Novikoff hepatocellular carcinoma cells possess cell-surface glycoproteins that bind the lectin, concanavalin A. A subset of Con A-binding plasma membrane glycoproteins was solubilized by addition of n-butanol to a suspension of Novikoff cells. Glycoproteins solubilized into the n-butanol-saturated aqueous phase of the two-phase mixture were purified by sequential chromatography on DEAE-cellulose and Sepharose-conjugated concanavalin A. Glycoproteins specifically bound to the Sepharose-conjugated Con A exhibited apparent M_r = 72,000 to 125,000. The plasma membrane localization of these components was inferred by their isolation from cells surface labeled with NaIO₄/ NaB³H₄. A xenoantiserum, raised against glycoproteins specifically bound to Sepharose-conjugated concanavalin A was employed to identify reactive components in nonionic detergent extracts of Novikoff tumor cells or rat hepatocytes surface labeled using lactoperoxidase-catalyzed iodination (¹²⁵I). Major reactive peptides in extracts of Novikoff cells exhibited apparent M_r = 74,000, 82, 000, 110,000, and 135,000, while those in extracts of hepatocytes possessed apparent M_r = 98,000 and 105,000. The reactivity of the antiserum with extracts of ¹²⁵I-labeled Novikoff cells was abolished by absorption of the antiserum with hepatocytes, indicating that the qualitative differences observed may result from structural modification of one or more cell-surface glycoproteins, rather than the expression of new or inappropriate glycoproteins. This antiserum will provide a useful probe to investigate alterations in the expression or structure of glycoproteins that occur as a consequence of malignant transformation or adaptation of malignant cells to growth in the ascitic form.