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S Dosako

Publications and source records attributed to S Dosako.

18 recordsLinked to original sources
PubMed2000

A method for measuring specific IgE in sera by direct ELISA without interference by IgG competition or IgG autoantibodies to IgE.

BACKGROUND: In measuring specific IgE levels in sera by direct ELISA, competition with coexisting IgG often impedes an exact IgE determination; additionally, IgG autoantibodies to IgE (IgG-IgE) in sera affect the assay. In this paper, we attempt to determine accurate specific IgE levels by selective removal of IgG with a protein G-immobilized gel (PG) and by acid treatment of the PG to compensate for the unintended removal of IgE, probably due to the PG binding IgG-IgE. METHODS: IgG in sera was removed using PG at pH 7.0. Then, the PG was treated with citrate buffer at pH 3.0 for 5 min to liberate IgE from IgG-IgE complexes, after IgG-binding sites on the PG were saturated with bovine IgG, since PG came to bind IgE at acidic pHs. IgE levels were then measured by ELISA. RESULTS: The PG treatment of sera removed the effect of inhibitory competition by coexisting IgG, especially at higher concentrations of sera, to improve specific IgE detection by direct ELISA. However, PG treatment alone sometimes reduced IgE levels (39% of sera tested), even though PG does not bind IgE at pH 7.0, which indicated the presence of IgG-IgE complexes. The reduction in IgE returned almost to their original levels in the sera by acid treatment of the PG. By combining the PG treatment with acid treatment, specific IgE measurement in sera was improved significantly (p < 0.01, Wilcoxon signed rank test). CONCLUSION: Measurement of specific IgE in sera by direct ELISA was improved by using the PG and acid treatment technique.

Animals↗
PubMed2000

Role of basic residues of human lactoferrin in the interaction with B lymphocytes.

We have previously demonstrated that lactoferrin was incorporated into B lymphocytes and that a trypsin treatment for a short period reduced the number of lactoferrin molecules incorporated into B lymphocytes. An N-terminal sequence analysis revealed that the mild trypsin treatment had cleaved the three N-terminal amino acids, Gly1-Arg2-Arg3. Chemical conjugation of lost sequence analogue Gly-Arg-Arg-Gly with the mildly digested lactoferrin recovered the interaction with B lymphocytes, while conjugation of acetyl-Arg-Arg-Gly, a deamino analogue of Gly-Arg-Arg-Gly, did not recover the interaction. This shows that the N-terminal basic region containing N-terminal Gly played an important role in the interaction with B lymphocytes. Acylation of the amino groups of lactoferrin also significantly reduced the interaction with B lymphocytes, and an O-methylisourea treatment of the amino groups, which preserved the positive charge, hardly affected the interaction. These results suggest that both the N-terminal basic region and the basic characteristics of the whole molecule contributed to its interaction with B lymphocytes.

Amino Acid Sequence↗
PubMed2000

Inhibitory effects of bovine lactoferrin on the adherence of enterotoxigenic Escherichia coli to host cells.

Adherence is an essential and prerequisite step for the colonization of mucosal surfaces by enterotoxigenic Escherichia coli (ETEC). We studied the effect of bovine lactoferrin (BLF) on the adherence of ETEC to human epithelial cells in vitro, and to intestinal mucosa of ICR germfree mice in vivo. In the in vitro study, BLF was found to inhibit the adherence of ETEC. This adhesion-inhibiting activity of BLF was found to lessen with decreasing BLF concentration, but the data obtained suggest a positive inhibitory effect of BLF against the adhesion of ETEC cells. In the in vivo study, the counts of adherent bacteria in various sections of the intestinal tract (duodenum, jejunoileum, and large intestine) were lower in the BLF group than in the control group, suggesting the possible action of BLF as an intestinal tract adherence-blocking agent with regards to ETEC.

Animals↗
PubMed1996

Lactoferrin-mediated protection of the host from murine cytomegalovirus infection by a T-cell-dependent augmentation of natural killer cell activity.

The administration of bovine lactoferrin (LF) with 1 mg/g body weight before the murine cytomegalovirus (MCMV) infection completely protected the BALB/c mice from death due to the infection. In these LF-treated mice, a significant increase in the activity was found in the NK cells but not in the cytolytic T lymphocytes which recognized an MCMV-derived peptide. Moreover, the elimination of the NK cell activity by an injection with anti-asialo GM1 antibody abrogated such augmented resistance, thus supporting the hypothesis that the LF-mediated antiviral effect in vivo is performed through the augmentation of NK cell activity. No such LF-mediated antiviral effect in vivo with the increased NK cell activity was found in athymic nude mice, whereas it was restored completely by the transfer of splenic T cells from LF-treated donors. These findings therefore suggest that T lymphocytes induce both the augmentation of NK cell activity and the resultant antiviral effect in the LF-treated hosts.

3T3 Cells↗
PubMed1994

Inhibition with lactoferrin of in vitro infection with human herpes virus.

Human lactoferrin (hLF) as well as bovine lactoferrin (bLF) inhibited infection of tissue culture cells with human cytomegalovirus (HCMV) and human herpes simplex virus-1 (HSV-1). The addition of lactoferrin (LF) inhibited both in vitro infection and replication of HCMV and HSV-1 in human embryo lung host cells. The maximum inhibition by more than six exponentials of TCID50 for HCMV and four exponentials for HSV-1 was obtained at a concentration in a range from 0.5 to 1 mg of LF per ml of medium. The antiviral activity of LF was associated with its protein moiety, but not with its iron molecule or sialic acid. None of other transferrin gene family members bound to ferrous ions or sialic acid possessed significant antiviral activity. Additionally, we found that LF prevented virus adsorption and/or penetration into host cells, indicating an effect on the early events of virus infection. Preincubation of host cells with LF for 5 to 10 min was sufficient to prevent HCMV infection, even when LF was removed after addition of virus. These results suggest that LF possesses a potent antiviral activity and may be useful in preventing HCMV and HSV-1 infection in humans.

Adsorption↗
PubMed1992

Inhibition by lactoferrin and kappa-casein glycomacropeptide of binding of Cholera toxin to its receptor.

Inhibition from binding of Cholera toxin (CT) to Chinese hamster ovary (CHO)-K1 cells and ganglioside GM1 by lactoferrin (Lf) and kappa-casein glycomacropeptide (GMP) from cow's milk was examined. Both Lf and GMP effectively reduced the CT-derived morphological changes in CHO-K1 cells. The competitive binding assay demonstrated that both Lf and GMP inhibited the binding of CT to GM1, although their affinity for CT was lower than that of GM1. The inhibitory effect of Lf and GMP seemed to be attributed to their terminal sialic acid, although the sugar chain sequence only partially fitted to the CT-receptor.

Animals↗
PubMed1992

Characteristics of chymotrypsin modified with water-soluble acylating reagents and its peptide synthesis ability in aqueous organic media.

Several kinds of modified chymotrypsin were prepared with water-soluble acylating reagents, and their characteristics after hydrolyzing with unmodified chymotrypsin in aqueous-N,N'-dimethylformamide (DMF) media were compared. It was found that chymotrypsin (Csin), of which a 20% amino group was modified with a benzyloxycarbonyl group (Z(20)Csin), had more favorable characteristics than unmodified chymotrypsin with regard to hydrolytic activity in an aqueous DMF media. We also investigated the Z(20)Csin-catalyzed peptide synthesis in two different solution systems. In the one-layer system containing water and DMF, Z(20)Csin catalyzed the peptide bond formation in a higher yield than that by unmodifide chymotrypsin and enabled a synthetic reaction in even an 80% (v/v) DMF media, in which the hydrolytic reaction could not be carried out. Z(20)Csin catalyzed the condensation between some N-acyl amino acids or peptide derivatives and amino acids in 90% ethylacetate, 90% hexane or 50% benzene. This latter method employs a two-layer system, and the modified enzyme may be able to reduce the number of synthetic steps when preparing acyl peptides.

Acylation↗
PubMed1992

Transformation of human colostrum lymphocytes with Epstein-Barr virus.

Lymphocytes from human colostrum were transformed with EB virus to obtain immunoglobulin secreting cells. Equal proportions of IgG, IgA and IgM were detected in wells containing transformed colostrum cells. Pretreatment of colostrum cells with BCGF prior to EB virus infection reduced the transformation slightly. We discussed the possibility of establishing cell lines that produced human monoclonal antibody using colostrum cells.

Cell Transformation, Viral↗
PubMed1991

Generation of hybrid hybridomas secreting human IgM class hybrid antiricin and antidiphtheria toxin antibodies.

Two lines of mouse-human hybridomas were fused to produce human bifunctional antibodies. A hybridoma that secretes human IgM (kappa) class antiricin monoclonal antibody was treated with actinomycin D to inhibit cell growth. Another cell line, secreting human IgM (lambda) class antidiphtheria toxin monoclonal antibody, was 6-thioguanine resistant (HAT sensitive). Six hybridomas secreting IgM with both kappa and lambda light chains were obtained. Two of them secreted antibodies with antiricin specificity (kappa and lambda light chains) and antidiphtheria toxin specificity (kappa and lambda light chains). Antidiphtheria toxin antibodies secreted from other hybrid hybridomas did not contain kappa light chain, but lambda chain. A hybrid hybridoma clone 5-29 secreted complete hybrid IgM with lowered affinity to diphtheria toxin. These results suggested unbalanced recombination of immunoglobulin polypeptide chains in hybrid hybridomas.

Animals↗
PubMed1990

Purification and some properties of proliferation suppressing factor from human lung adenocarcinoma PC-8.

Extracts by 3 M KCl from a human lung adenocarcinoma cell line, PC-8, suppressed the proliferation of phytohemagglutinin activated lymphocytes. The proliferation suppressing factor (PSF) was purified from the extracts by ammonium sulfate precipitation, gel filtration and ion exchange chromatography. The purified PSF had a molecular weight of 50 kDa by SDS-PAGE and was acid- and heat-labile. Since the PSF also suppressed the proliferation of three established human cell lines, it is unlikely that the PSF hinders the interaction between lymphocytes and mitogens.

Adenocarcinoma↗
PubMed1990

Iron uptake from transferrin and lactoferrin by rat intestinal brush-border membrane vesicles.

Interaction of 59Fe-labeled rat transferrin, human lactoferrin, and bovine lactoferrin with rat small intestinal brush-border membrane vesicles was investigated with the use of a rapid filtration technique. Specific binding of 59Fe-labeled rat transferrin and bovine lactoferrin to brush-border membrane vesicles from suckling and adult rats was identified. In contrast, no binding of human lactoferrin occurred. The presence of transferrin receptors on the brush-border membrane of suckling rats was confirmed by immunoblotting, and the molecular mass of the receptor was 96 kDa under nonreducing conditions. Scatchard plot analysis indicated 2.4 x 10(14) binding sites/mg of membrane protein with an affinity constant (Ka) of 4.9 x 10(6) M-1 for rat milk transferrin and 2.2 x 10(14) binding sites/mg of membrane protein with a Ka of 3.2 x 10(6) M-1 for bovine lactoferrin. Bovine lactoferrin competitively inhibited the binding of rat transferrin to the brush-border membrane vesicles. Deglycosylation of rat transferrin and bovine lactoferrin had no influence on the binding of these proteins. The results suggested that bovine lactoferrin bound to the receptor for rat transferrin on the brush-border membrane and that the polypeptide chain rather than the glycan moiety is responsible for the interaction of these proteins with the rat brush-border membrane.

Aging↗
PubMed1988

Human hybrid immunoglobulin M containing immunoglobulin A.

Some hybridoma clones made by fusion of a human lymphoblastoid cell line, HO323 with human B lymphocytes, secreted not only IgA but also IgM-like immunoglobulin molecules. The IgM-like immunoglobulin had a molecular size of 900 K which corresponded to that of IgM. Immunochemical analyses revealed that the IgM-like immunoglobulin contained two monomeric IgA and three monomeric IgM molecules. In the IgA moieties, half of original light chains were replaced with kappa chains derived from the IgM, and vice versa.

Cell Line↗
PubMed1987

One-step isolation of lactoferrin using immobilized monoclonal antibodies.

Immunoaffinity columns made with monoclonal antibodies to either human or bovine lactoferrins were prepared to isolate human lactoferrin or bovine lactoferrin from milks by a single chromatographic step. Recoveries of human lactoferrin and bovine lactoferrin were 98 and 97%, respectively. The human lactoferrin recovered from defatted human colostrum was 98% pure with 93% iron-binding capacity. Amount of recovered bovine lactoferrin, as well as purity and iron-binding capacity, varied widely depending on the source of bovine milks and pretreatments (particularly pasteurization temperature). The best source to isolate bovine lactoferrin was raw skim milk yielding a protein 97% pure and with a 99% iron-binding capacity. Thus, immunoaffinity chromatography provides an effective one-pass isolation of highly pure human or bovine lactoferrin with reasonable recovery and iron-binding capacity.

Animals↗
PubMed1986

IgA specific helper factor (alpha HF) in human colostrum.

Induction of immunoglobulin secretion by human colostrum was investigated using human peripheral blood lymphocytes (PBL) and Epstein-Barr virus transformed human B lymphoblastoid cells. Stimulation of the cells with colostrum induced IgA plaque forming cells but neither IgG nor IgM plaque forming cells, indicating the occurrence of IgA specific helper factor (alpha HF) in human colostrum. alpha HF activity was eluted into fractions with an apparent molecular weight of about 80 kD by gel filtration, and with a PI range of 5.8 to 6.2 by chromatofocusing. IgA secreted by PBL stimulated with alpha HF had a similar molecular weight distribution to that of IgA in human colostrum. From these results a hypothesis is proposed; IgA-committed B cells in the mammary gland differentiate to plasma cells producing dimeric IgA after stimulation by alpha HF so that the dominant immunoglobulin in human colostrum is IgA.

Antibody-Producing Cells↗
PubMed1984

Transformation of human colostrum lymphocytes with Epstein-Barr virus and the production of IgA in culture.

Human colostrum lymphocytes obtained on day 2-5 after delivery were found to be as susceptible to transformation with Epstein-Barr virus (EBV) as peripheral lymphocytes. An enzymelinked immunosorbent assay showed that the proportion of transformed cells producing IgA, IgG, and IgM varied from colostrum specimen to specimen. 1 microgram/ml of IgA could be produced by freshly transformed cell mixture. But the capacity to produce IgA was lost or decreased by one order of magnitude during and after cloning of producing cells; the highest production with cloned cell cultures was about 0.2 micrograms/ml. Immunofluorescence staining of IgA-positive cells showed instability of the capacity of transformed cells to produce IgA.

Cell Transformation, Viral↗
PubMed1983

Milk of northern fur seal: composition, especially carbohydrate and protein.

The milk of northern fur seal was analyzed with special interest in carbohydrate and protein. High solids (61%) and fat (45.6%) were characteristics of its gross composition. Fatty acid distribution showed that more than 22% of the fatty acids had carbon chains longer than 20 and that approximately 70% contained one or more double bonds. Analysis of free sugars showed no lactose but 123 mg/100 ml of myo-inositol. In carbohydrates bound to casein, .99% of sialic acid and .2% of glucosamine were determined. The amino acid composition of casein showed higher tryptophan, lysine, serine, and glycine than bovine casein, and lower arginine, proline, and leucine. In whey, arginine, threonine, and valine were higher, whereas lysine, aspartic acid, isoleucine, and leucine were lower than in bovine whey. Amino acid patterns in casein and whey were similar to those of cat milk. The appearance of casein micelles was similar to bovine casein micelles. The mean diameter, however, was larger (approximately 330 nm). Electrophoretic pattern of casein showed five major bands in addition to minor components. One of the minor components was a glycoprotein, probably kappa-casein-like protein. The major whey protein had a mobility similar to that of bovine beta-lactoglobulin. No alpha-lactalbumin-like protein was observed.

Amino Acids↗