Search PubMed⌕ Search

Biomedical subjects

S Iwasa

Publications and source records attributed to S Iwasa.

At least 55 records · Page 3Linked to original sources
PubMed1994

An ex vivo assay for estimating the antiviral state of hepatocytes.

An ex vivo antiviral assay was established which uses hepatocytes from mice given recombinant mouse interferon-beta (rmIFN-beta). Assay results were compared with results obtained with a 2',5'-oligoadenylate synthetase (2-5AS) assay. rmIFN-beta was intraperitoneally administered to C3H mice and the antiviral state of their liver parenchymal cells was evaluated in an in vitro cytopathic effect assay. In this assay, cells are infected with vesicular stomatitis virus (VSV) and surviving cells are determined colorimetrically. The antiviral state was measured as the resistance of hepatocytes to VSV infection with increasing doses of rmIFN-beta. The antiviral state correlated well with the dose-dependent increase in hepatic 2-5AS activity. This good correlation suggests that induction of 2-5AS mediates the antiviral action of interferon in liver tissue. This ex vivo assay could be a useful tool for estimating the ability of hepatocytes to resist hepatitis virus infection.

Animals↗
PubMed1994

Antagonism of the human thromboxane A2 receptor by an anti-asthmatic agent AA-2414.

The human thromboxane A2 receptor (TXA2-R)-coding gene was introduced into Chinese hamster ovary cells and a cell line (TCHO-25) stably expressing TXA2-R, at a level of 3 x 10(5)/cell, was obtained. An anti-asthmatic agent AA-2414 [(+-)-7-(3,5,6-trimethyl-1,4-benzoquinon-2-yl)-7- phenylheptanoic acid] competitively inhibited the specific binding of a TXA2 mimic ([3H]U-46619) to the TCHO-25 cells, with an IC50 of 6.0 x 10(-8) M, indicating that the drug is an antagonist of human TXA2-R. The TCHO-25 cells offer a tool for the screening and characterization of human TXA2-R antagonists.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1994

Pharmacokinetic alteration in rats of recombinant interleukin-2 (rIL-2) by immunocomplexing with a monoclonal antibody against rIL-2.

We have investigated the pharmacokinetic alteration in rats of recombinant interleukin-2 (rIL-2) by immunocomplexing with a monoclonal antibody against rIL-2. Serum rIL-2 levels after the intravenous administration of the immune complex at a dose of 100 micrograms/rat as rIL-2 were significantly higher than those after intravenous administration of rIL-2 alone at the same dose. Pharmacokinetic analysis indicated that the distribution volume of rIL-2 decreased from 74.0 to 10.3 ml/rat, while the elimination rate of rIL-2 was little changed by immunocomplexing with the antibody. On the other hand, serum rIL-2 levels after the subcutaneous administration of the immune complex at a dose of 100 micrograms/rat as rIL-2 were sustained longer than those after the subcutaneous administration of rIL-2 alone at the same dose, and Tmax shifted from 0.83 to 3.0 h by immunocomplexing with the antibody. Pharmacokinetic analysis also revealed that the mean-residence-time of rIL-2 increased from 1.98 to 6.52 h, and the area-under-the curve of rIL-2 decreased slightly, from 834 to 548 ng.h/ml, by immunocomplexing with the antibody.

Animals↗
PubMed1994

Intestinal absorption of serrapeptase (TSP) in rats.

A sensitive sandwich enzyme immunoassay (e.i.a.) for serrapeptase (TSP), an orally available anti-inflammatory proteinase, was established using affinity-purified anti-TSP rabbit IgG and its Fab' fragment conjugated with horseradish peroxidase as the first and the second antibodies respectively. TSP in the plasma was determined by the e.i.a. after its oral administration (100 mg/kg) to rats. The peak concentration was observed between 30 min and 2 h after administration. TSP in the plasma samples was trapped on a microtitre plate coated with the affinity-purified anti-TSP rabbit IgG, and the hydrolysis of a synthetic fluorogenic substrate, butoxycarbonyl-Glu(benzyloxy)-Ala-Arg-4-methylcoumaryl-7-amide, by the trapped TSP was fluorometrically measured (proteinase assay). The values obtained by the e.i.a. and those obtained by the proteinase assay correlated well for various plasma samples. These results indicate that orally administered TSP was absorbed from the intestinal tract and transferred into the circulation in an enzymically active form.

Administration, Oral↗
PubMed1993

Enhancement of anti-tumor activity of recombinant interleukin-2 (rIL-2) by immunocomplexing with a monoclonal antibody against rIL-2.

We have investigated biological properties of an immune complex of recombinant interleukin-2 (rIL-2) and a monoclonal antibody against rIL-2 in mice for induction of killer cells and for anti-tumor activity. We have also examined the clearance of subcutaneously-injected immune complex in mice and compared it with that of rIL-2 alone. Plasma rIL-2 levels were sustained longer in mice given the immune complex than in mice given rIL-2 alone at a dose of 10 micrograms/mouse, and they were detectable even at 24 hours after the administration of the immune complex, while they fell to undetectable levels by 6 hours after the administration of rIL-2 alone. A more significant portion of rIL-2 was detected in lymph nodes after subcutaneous injection of the immune complex than that of rIL-2 alone. Splenic lymphocytes from mice given the immune complex demonstrated a higher killer cell activity against YAC-1 cells than those from mice given rIL-2 alone. The immune complex also exerted more significant anti-tumor effect in a dose-dependent manner in Meth-A fibrosarcoma-bearing mice than rIL-2 alone. Our results indicate that immunocomplexing of rIL-2 with an antibody against rIL-2 provides a useful tool as the drug delivery system for cancer therapy using rIL-2.

Animals↗
PubMed1992

Thrombolytic and pharmacokinetic properties of an immunoconjugate of single-chain urokinase-type plasminogen activator (u-PA) and a bispecific monoclonal antibody against fibrin and against u-PA in baboons.

Targeting of plasminogen activators to the fibrin component of a thrombus with the use of monoclonal antibodies (MA) directed against human fibrin may enhance their thrombolytic potency and fibrin-specificity. The thrombolytic and pharmacokinetic properties of rscu-PA/MA-FU1-74, an immunoconjugate of recombinant single-chain urokinase-type plasminogen activator (rscu-PA) and a bispecific MA directed against u-PA and against the beta-chain of human fibrin (MA-FU1-74), were investigated in baboons with a [125I]fibrin-labeled autologous blood clot in the femoral vein. Continuous intravenous infusion of rscu-PA/MA-FU1-74 (1:1.2 molar ratio) over 2 hours showed a fivefold increased thrombolytic potency (lysis per unit dose) over that of unconjugated rscu-PA, as evidenced both by a higher maximal rate of lysis (380% +/- 68% v 78% +/- 25% lysis per mg u-PA equivalent of compound administered per kg body weight, P less than .001), and by a lower dose at which the maximal rate of lysis occurs (0.19 +/- 0.03 v 0.82 +/- 0.10 mg compound per kg body weight, P less than .001). The specific thrombolytic activity (percent lysis per unit steady-state plasma u-PA antigen level) was lower for rscu-PA/MA-FU1-74 than for rscu-PA, as shown by both a lower maximal rate of lysis (60% +/- 13% v 220% +/- 22% lysis per microgram/mL u-PA antigen level in plasma, P less than .001) and a higher plasma antigen level at which maximal lysis is achieved (1.2 +/- 0.17 v 0.20 +/- 0.01 microgram/mL, P less than .001). The thrombolytic potency of rscu-PA/MA-UK1-3, an immunoconjugate of rscu-PA with the parental anti-u-PA antibody was similar to that of unconjugated rscu-PA. Clot lysis was achieved without systemic fibrinogen or alpha 2-antiplasmin consumption, and with a minor transient prolongation of the bleeding time. After the end of the infusions, u-PA-related antigen disappeared from plasma in a biphasic manner, with an initial half-life of 3.3 +/- 0.4 minutes for rscu-PA, 13 +/- 1 minutes for rscu-PA/MA-FU1-74, and 13 +/- 1 minutes for rscu-PA/MA-UK1-3, with corresponding plasma clearances of 340 +/- 28, 10 +/- 1, and 37 +/- 4 mL/min, respectively (mean +/- SEM). rscu-PA/MA-FU1-74 has a fivefold higher thrombolytic potency than unconjugated rscu-PA, as a result both of fibrin targeting by the specific idiotype of the antibody and of a slower plasma clearance.

Animals↗
PubMed1992

Therapeutic effect of ansamitocin targeted to tumor by a bispecific monoclonal antibody.

We have constructed a murine hybrid hybridoma that secretes a bispecific monoclonal antibody (mAb) by fusing a hybridoma secreting an anti-ansamitocins mAb with a hybridoma secreting an anti-human transferrin receptor (TfR) mAb that binds to human A431 epidermoid carcinoma cells. The bispecific mAb, reactive to both ansamitocins and TfR, was purified by a combination of hydrophobic column chromatography and hydroxyapatite high-performance liquid chromatography, and evaluated in in vivo experiments using human tumor cell-implanted nude mice. Ansamitocin P-3 targeted through one of the antigen combining sites of the bispecific mAb was potentially more effective in suppressing the growth of established A431 tumor xenografts implanted on nude mice than unconjugated ansamitocin P-3 or the immunoconjugate of ansamitocin P-3 and monospecific anti-ansamitocins antibody, and the targeted ansamitocin P-3 finally eradicated the tumor mass. The bispecific mAb also played an important role in reducing such undesirable side-effects of ansamitocin P-3 as the loss of body weight, the damage to liver functions and the decrease in the number of white blood cells.

Animals↗
PubMed1992

Cord blood lymphocyte responses to food antigens for the prediction of allergic disorders.

Proliferative responses of cord blood lymphocytes (CBLs) to food antigens and cord blood IgE concentrations were measured in 37 full term newborn infants for the prediction of allergic disorders. In these 37 infants who were followed up for two years, allergic history of the family was found in four (sensitivity 57.1%) and cord blood IgE concentrations were greater than 0.5 IU/ml in three (sensitivity 42.9%) of seven infants who developed allergic disorders. When CBLs were stimulated twice by ovalbumin or bovine serum albumin, the value of the stimulation index in proliferative responses of CBLs to ovalbumin or bovine serum albumin was greater than 1.5 in six (sensitivity 85.7%) of seven infants who developed allergic disorders. The specificity of the responses of CBLs in the prediction of the development of allergic disorders was 93.3%. The proliferative responses of CBLs to food antigens were useful in the prediction of not only development of allergic disorders but also offending allergens. These observations provide further evidence that sensitisation is occurring in utero. This would appear to be increasingly important in the genesis of early atopic problems. As our follow up is only two years, in utero sensitisation is a prediction for the early development of atopic disease but only longer follow up will show whether this holds good for allergic disorders at any age.

Allergens↗
PubMed1992

Endotoxin of Pseudomonas pseudomallei detected by the body weight-decreasing reaction in mice and comparison of it with those of P. cepacia and P. aeruginosa.

The heat-treated whole cells, culture supernatants, and extracted endotoxin preparations of Pseudomonas pseudomallei were examined for endotoxin by the mouse body weight-decreasing (BWD) test. The experiments were conducted also with those of P. cepacia and P aeruginosa. Endotoxin was detected in all the samples of P. pseudomallei. Endotoxin of P. cepacia was detected in whole cells, but not in culture supernatant. The BWD activity of P. aeruginosa was 30 times as high as that of P. pseudomallei. This result was confirmed by the experiments with endotoxin preparations. In the limulus amebocyte lysate gelation (LAL) test, however, the endotoxin preparations of the two species showed the same level of activity.

Animals↗
PubMed1992

[Two cases of recurrent brain tumor during GH replacement therapy].

Two cases of patients with recurrent brain tumor are presented. Each of them received growth hormone (GH) replacement therapy for growth failure secondary to cranial irradiation. The first case is that of a 10-year-old girl who was treated with a combination of surgical resection, radiotherapy and chemotherapy for cerebellar medulloblastoma at 1 y.o. At the age of 9, 10 month after the beginning of GH replacement therapy, she complained of headache. This was due to shunt malfunction when CSF cytology was class V. It revealed that there was recurrence of medulloblastoma. The second case is that of a 14-year-old girl who was treated with a combination of surgical resection, radiotherapy and chemotherapy for suprasellar germinoma at the age of 10. This tumor completely disappeared after these procedures. For her growth failure, we started GH replacement therapy and after 1 year, she complained of lt. leg pain due to tibial and pelvic bone metastasis. In medical literature, we found 15 recurrent brain tumors during GH replacement therapy. These include our 2 cases, and 9 cases in which there was recurrence within 1 year. Recently, receptors for some somatomedins have been found in brain tumors. Although these numbers are too small for us to arrive at conclusions, we think it is possible that there are some mechanisms connecting GH replacement therapy and recurrence of certain brain tumors.

Adolescent↗
PubMed1991

Enhancement of clot lysis in vitro and in vivo with a bispecific monoclonal antibody directed against human fibrin and against urokinase-type plasminogen activator.

A hybrid hybridoma (FU1-74), secreting a bispecific monoclonal antibody (bs mAb), was obtained by fusion of a murine hybridoma secreting a monoclonal antibody (mAb) specific for human fibrin with a murine hybridoma secreting a mAb against urokinase-type plasminogen activator (u-PA). The bs mAb (MA-FU1-74), purified to homogeneity from mouse ascitic fluid, migrated as a single band with apparent Mr 150,000 on nonreduced SDS-PAGE and had an affinity for both human fibrin (Ka = 2 x 10(7) M-1) and for u-PA (Ka = 10(8) M-1) comparable to that of the mAbs obtained from the respective parental hybridomas. MA-FU1-74 did not influence the enzymatic activity of two-chain u-PA (tcu-PA) towards plasminogen or towards a chromogenic substrate. The complex of MA-FU1-74 with recombinant single chain u-PA (rscu-PA) or with tcu-PA (urokinase) enhanced the fibrinolytic potency of the plasminogen activator towards clotted human plasma 20-fold and 5-fold, respectively. In a hamster pulmonary embolism model, the rscu-PA/MA-FU1-74 complex had a 13- to 17-fold increased thrombolytic potency (percent lysis per mg/kg u-PA administered) relative to that of rscu-PA. The specific thrombolytic activity (percent lysis per microgram/ml steady state plasma level of u-PA antigen) of the complex was, however, not significantly different from that of rscu-PA. The complex of rscu-PA with the parental anti-u-PA mAb (MA-UK1-3) had only a 2-fold enhanced thrombolytic potency relative to that of rscu-PA and had a 5-fold decreased specific thrombolytic activity. The plasma clearance rates of the complexes of rscu-PA with both MA-FU1-74 and MA-UK1-3 were about 10-fold lower than that of rscu-PA. In a rabbit jugular vein thrombosis model, the rscu-PA/MA-FU1-74 complex had a 4-fold enhanced thrombolytic potency, an unchanged specific thrombolytic activity and 20-fold reduced plasma clearance. In both animal models, the rscu-PA/MA-FU1-74 complex did not cause more extensive systemic activation of the fibrinolytic system than rscu-PA. It is concluded that the bispecific anti-fibrin/anti-u-PA mAb MA-FU1-74 targets u-PA to the fibrin clot, resulting in a significantly enhanced thrombolytic potency of the plasminogen activator.

Amino Acid Sequence↗
PubMed1991

[19-Hydroxyandrostenedione in human ovarian vein measured by GC-MS].

Nineteen-hydroxyandrostenedione (19-OHA) is considered to be an obligatory intermediate of estrogen synthesis. To clarify the role of 19-OHA in the human ovary, the following experiments were undertaken. Ovarian and peripheral vein blood in mid follicular and luteal phase were obtained from 14 women during gynecological surgery. The concentrations of androstenedione (A), testosterone (T), 19-OHA, estrone (E1) and estradiol (E2) were measured by gas chromatography mass spectrometry using deuterium-labeled steroids as internal standard. The effect of human chorionic gonadotropin (hCG) on those steroids was also studied in mid luteal phase. The concentrations of 19-OHA in ovarian vein were 1.20 +/- 0.16 ng/ml (mean +/- SE) in mid follicular and 0.78 +/- 0.18 ng/ml in mid luteal phase. The steroid levels measured in ovarian vein were significantly higher than those in peripheral vein. Though the administration of hCG in mid luteal phase enhanced A and E2 levels in ovarian vein, the levels of T, 19-OHA and E1 were not altered. Significant correlation between the levels of E2 and A was observed while none of the steroids correlated with 19-OHA. These results suggest, for the first time, that 19-OHA is produced and secreted from the human ovary. The question as to the physiological and biosynthetic role of ovarian 19-OHA has to be answered in the future.

Adult↗
PubMed1991

Effective production of anti-tetanus toxoid and anti-HBsAg human monoclonal antibodies by serum-free culture of hybridomas.

Two hybridoma systems, mouse.human-human (m.h-h) heterohybridoma and human-human (h-h) hybridoma, have been established, and hybridomas secreting anti-tetanus toxoid and anti-HBsAg human monoclonal antibodies (MoAbs), both having a neutralizing activity have been obtained. Cell-line improvement was shown to be an efficient method for improving the productivity in a cell culture process. Two kinds of serum-free media, GFS (a serum substitute)-containing media and polyethylene glycol (PEG)-containing media, have been established to produce human MoAbs. m.h-h Heterohybridomas could be cultivated for a long period by perfusion culture in an agitation vessel, but h-h hybridomas could not. We found that h-h hybridomas show growth-associated antibody production kinetics and established two kinds of long-term cultivation systems: continuous perfusion culture and semi-continuous immobilized perfusion culture. We also scaled up batch culture and short-term perfusion culture to 200-L and 50-L fermentors, respectively. Processes for large-scale purification from the culture supernatants of both GFS- and PEG-containing serum-free media have also been developed.

Animals↗
PubMed1991

Characterization of monoclonal antibodies against human tissue plasminogen activator (tPA): quantitation of free tPA in human cell cultures by an ELISA.

Seven murine monoclonal antibodies produced against tissue plasminogen activator (tPA) were evaluated by means of enzyme-linked immunosorbent assays (ELISAs), and their effects on the enzymatic activities of tPA towards a synthetic substrate (S-2288) and plasminogen were investigated. One of the antibodies, TPA1-70, strongly inhibited the enzymatic activity of tPA in a fibrin agarose plate assay, while it did not affect the enzymatic activity towards the synthetic substrate or plasminogen. The antibody is directed to an epitope on the B-chain of tPA, which is necessary for the formation of a ternary complex of tPA, fibrin and plasminogen, but probably not to the active site. Another antibody, TPA2-14, partially inhibited the enzymatic activities of tPA towards the synthetic substrate and plasminogen, but it was not able to bind to the inactive tPA complexed with plasminogen activator inhibitor-1 (PAI-1). The antibody is directed to an epitope on the second kringle region, which is probably one of the PAI-1 binding sites. This property of the antibody enabled us to develop an ELISA for selective quantitation of free tPA in culture media conditioned with several human cell lines. The results indicate that tPA in these media exists either partially or almost entirely in a complex with PAI-1.

Animals↗
PubMed1990

A human hybrid hybridoma producing a bispecific monoclonal antibody that can target tumor cells for attack by Pseudomonas aeruginosa exotoxin A.

By fusing a human hybridoma producing an IgG2 kappa antibody against human A431 epidermoid carcinoma cells with an Epstein-Barr virus-transformed human B lymphocyte producing an IgG2 kappa antibody against Pseudomonas aeruginosa exotoxin A, we established a hybrid hybridoma producing a bispecific monoclonal antibody reacting with both A431 cells and the exotoxin. Human IgG was purified from the culture supernatant of the hybrid hybridoma, and the bispecific monoclonal antibody in the IgG preparation was further separated from the two parental antibodies by hydroxyapatite high-performance liquid chromatography. The human bispecific monoclonal antibody thus obtained efficiently targeted the antibody-reactive cells, A431, for attack by the exotoxin in vitro.

ADP Ribose Transferases↗
PubMed1990

A human-human hybridoma secreting anti-Pseudomonas aeruginosa exotoxin-A monoclonal antibody with highly potent neutralizing activity.

A hybridoma secreting human monoclonal antibody (MAB) against Pseudomonas aeruginosa exotoxin A (PEA) was constructed by fusing Epstein-Barr virus-transformed peripheral blood lymphocytes with human B lymphoblastoid cell line TAW-925. The human-human hybridoma stably produced human IgG2 MAB at the rate of 0.4-0.5 microgram/ml per 10(6) cells per day for more than six months, and the MAB was capable of neutralizing the in vitro cytotoxic and in vivo lethal effects of PEA with approximately 100- and 70-fold, respectively, higher activity than serum polyclonal antibody preparations.

ADP Ribose Transferases↗
PubMed1990

Enhancement of fibrinolysis by bispecific monoclonal antibodies reactive to fibrin and plasminogen activators.

Murine hybrid hybridomas secreting bispecific monoclonal antibodies (bs mAbs) were constructed by fusing hybridomas secreting an anti-tissue plasminogen activator (tPA) or anti-urokinase (UK) mAb with hybridomas secreting a mAb which binds to human fibrin but not to fibrinogen. The bs mAbs reactive to both fibrin and PA (tPA or UK) were purified by affinity chromatography employing the respective antigen-coupled columns and characterized by fibrin-binding, amidolytic and fibrinolytic assays. Immunochemical conjugation of PAs and the bs mAbs did not impair the catalytic activity of PAs at all and made it possible to concentrate PAs on fibrin clot. Pretreatment of fibrin with the bs mAbs enhanced the fibrin-binding of PAs and the subsequent fibrinolysis.

Animals↗