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Biomedical subjects

S Sawada

Publications and source records attributed to S Sawada.

At least 451 records · Page 25Linked to original sources
PubMed1987

[Antitumor activity of new derivatives of camptothecin].

With the purpose of obtaining more potent and less toxic camptothecin (CPT) analogs, we prepared many derivatives of CPT. Among them, 7-ethyl-CPT (SN 22) and 7-ethyl-10-hydroxy-CPT (SN 38) showed strong antitumor activity with less toxicity. They were, however, insoluble and when they were made soluble, their activity was markedly diminished, as a result of cleavage of the delta-lactone ring. We therefore attempted to make soluble derivatives without breaking the delta-lactone ring and obtained 7-ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxy-CPT (CPT-11), which showed very strong antitumor activity by i.p., i.v. or p.o. administration against the ascites type of L1210 leukemia, P388 leukemia, sarcoma 180, Meth A fibrosarcoma, B16 melanoma, Ehrlich carcinoma and MH134 hepatoma and the solid type of sarcoma 180, Meth A fibrosarcoma, Lewis lung carcinoma, C3H/HeN mammary carcinoma, Ehrlich carcinoma and MH134 hepatoma. The antileukemic activity of CPT-11 against L1210 was much higher than that of adriamycin. The acute toxicity of CPT-11 was extremely low, particularly in the case of oral administration, the LD50 being 765.3 mg/kg, 22 times greater than that of CPT-Na.

Animals↗
PubMed1987

Action of 7-ethylcamptothecin on tumor cells and its disposition in mice.

Some biological effects of camptothecin (CPT) and its new derivative 7-ethylcamptothecin (ECPT) were studied. The drugs were effective against murine leukemia; ECPT was more effective than CPT. Ip administration of ECPT or CPT gave maximum treated/control values of 325% and 232%, respectively. The drugs also inhibited the growth of KB cells in vitro, 50% effective doses of 3.5 ng/ml of ECPT and 8.6 ng/ml of CPT, indicating the stronger activity of ECPT. Pharmacokinetic studies of the drugs in mice showed that ECPT had a longer biological half-life in the terminal phase and a larger amount remained in the plasma compared with CPT. After iv administration of ECPT, the drug accumulated in the intestine, suggesting that the main route of excretion of the drug is through the biliary tract. The study on cell cycle progression by flow cytometry suggested that the main effect of both drugs on L1210 cells was the blocking of G2-M phase. These results suggest that the main reasons for the superior antitumor activity of ECPT compared with CPT are as follows: (a) ECPT had a stronger growth-inhibiting activity against tumor cells, and (b) ECPT remained in the intestinal tract for a longer time and in higher amounts when administered in vivo.

Animals↗
PubMed1986

Modulation of prostacyclin generation in cultured human vascular endothelial cells and the effects of human alpha-natriuretic polypeptide.

Vascular endothelial cells have been known to possess not only a barrier function but also other biologically important functions maintaining vascular homeostasis. Among these, the generation of prostacyclin is one of the most conspicuous functions, and the modulation of its synthesis and liberation has been of interest with reference to the interaction with several vasoactive substances, including human atrial alpha-natriuretic polypeptide. This paper investigates the regulatory mechanism of prostacyclin generation using cultured human vascular endothelial cells as far as Ca2+ flux, (Na+ + K+)-ATPase activity, and Na+-Ca2+ exchange systems are concerned. Through these experimental studies the following results were obtained. Prostacyclin generation was triggered by an increase of Ca2+ influx, and an increase in intracellular Na+ also enhanced it, and this was accompanied by a decreased Ca2+ efflux arising from suppression of Na+-Ca2+ exchange systems. (Na+ + K+)-ATPase activity as well as prostacyclin generation was also enhanced by the increase of intracellular Na+. These results indicate a possible link between the mechanism which generates prostacyclin in the human vascular endothelial cells and the mobilization of electrolytes; however, in this aspect human atrial alpha-natriuretic polypeptide had no effect on the endothelial cells.

Atrial Natriuretic Factor↗
PubMed1986

A revised method for generation of unitary postsynaptic potentials for quantal analysis in the hippocampus.

For quantal analysis of excitatory postsynaptic potentials (EPSPs) in hippocampal CA3 neurons, a method was devised to evoke trains of unitary EPSPs at intended intervals and to control the number of unitary EPSPs composing each train at will. The amplitudes of the first EPSPs in EPSP trains evoked with this method were measured. From the mean and variance of the EPSP amplitudes, the mean number of quanta (m) released by a single impulse and the mean amplitude of EPSPs induced by individual quanta (q) were estimated in a standard solution and in a high calcium solution.

Animals↗
PubMed1986

Spectroscopic characterization of plastocyanin from hornwort.

Plastocyanin isolated from an aquatic higher plant, Ceratophyllum demersum L. (hornwort), has been characterized by electronic absorption, circular dichroism (CD), and electron paramagnetic resonance (EPR) spectroscopies. The visible absorption, CD, and EPR spectra of hornwort plastocyanin indicated a complete similarity of blue copper center to those of terrestrial higher plants and algae. However, the ultraviolet absorption spectrum of hornwort plastocyanin exhibited a lower tyrosine (Tyr) and a higher phenylalanine (Phe) content of the protein comparing with other plastocyanins. The ratio of Phe/Tyr residues was estimated to be 9 by amino acid analysis. The hornwort plastocyanin resembles in amino acid composition terrestrial higher plant plastocyanins rather than alga plastocyanins but is peculiar in the content of Phe and Tyr residues.

Amino Acids↗
PubMed1986

Generation of hybridomas producing human monoclonal antibodies against herpes simplex virus after in vitro stimulation.

Hybridomas producing human monoclonal antibodies against herpes simplex virus were generated by in vitro antigen stimulation before cell fusion. The cell fusion with tonsillar lymphocytes which were stimulated with antigen and/or pokeweed mitogen generated many hybridomas producing human IgG against the virus. A combination of antigen and pokeweed mitogen synergistically enhanced the generation of virus-specific hybridomas. Furthermore, the higher the antibody response of the tonsil, the more virus-specific hybridomas were generated by the cell fusion. These results suggest that cell fusion with in vitro stimulated lymphocytes can be applied to a variety of clinically relevant viruses.

Animals↗
PubMed1986

An investigation on reduction process of cucumber ascorbate oxidase.

Reduction process of cucumber ascorbate oxidase with L-ascorbate was investigated in detail through absorption and electron paramagnetic resonance (EPR) spectra under anaerobic condition. One of the three type I coppers (the type I copper which is oxidized rapidly (Sakurai, T. et al. (1985) Biochem. Biophys. Res. Commun. 131, 647-652)) and a pair of type III coppers only which contribute to the absorption at 330 nm were reduced faster than other two type I and the other pair of type III coppers, respectively. The principal active site of ascorbate oxidase was confirmed to be comprised of one type I, one type II and a pair of type III coppers. Type II copper seemed to be reduced after all type I and type III coppers have been reduced.

Ascorbate Oxidase↗
PubMed1986

Enhancement of radiation effects by acyclovir.

Acyclovir (ACV), a new antiviral drug, was used to investigate its effect of radiosensitivity in tumors in vivo. In in vivo experiments with Sarcoma-180 transplanted into the ICR mouse and FM3A transplanted into the C3H mouse, ACV enhanced the radiosensitivity of both tumors. In S-180, radiation effects were enhanced by treatment with 100 mg/kg of ACV from 30 min before to 60 min after irradiation. In S-180 treated by 400 mg/kg of ACV, the enhancement ratio was approximately 2.0, as evaluated by the growth delay method. In the FM3A tumor treated by 20 mg/kg of ACV, the enhancement ratio was approximately 1.3, as evaluated by tumor cure (TCD50 assay). ACV is already clinically used as an antiviral drug. Its ability to radiosensitize tumors could therefore have clinical potential when combined with radiotherapy.

Acyclovir↗
PubMed1986

Prostacyclin generation by cultured human vascular endothelial cells with reference to angiotensin I-converting enzyme.

Prostacyclin (PGI2) generation has been known to be regulated by several endogenous vasoactive substances, and in this study the relationship between angiotensin I-converting enzyme (ACE) related substances and PGI2 generation was investigated using cultured human vascular endothelial cells. Addition of angiotensin I (AI) or bradykinin (BK) enhanced PGI2 generation and increased the level of ACE activity in the culture medium, while the addition of ACE inhibitor (captopril) caused a dose dependent suppression of PGI2 generation and ACE activity. The enhancement of PGI2 generation induced by AI or BK was not affected by pretreatment with captopril, and angiotensin II (AII) did not show any effect on either PGI2 generation or ACE activity. Through these experimental results, the conversion of AI to AII by ACE was considered not to cause the enhancement of PGI2 generation. Captopril solely inhibited PGI2 generation and the reported hypothesis that captopril enhances PGI2 generation by the accumulation of AI or BK via inhibition of ACE was not confirmed in this experimental system. Rather, it is proposed that AI or BK induced PGI2 generation may be regulated by the increased breakdown of AI or BK, as an autoregulation mechanism, that is derived from increased ACE activity by AI or BK.

Angiotensin I↗
PubMed1986

The effects of acebutolol alone and in combination with furosemide or hydralazine in experimentally induced hypertensive G-minipigs.

Experimentally induced hypertensive G-minipigs were used for assessing the antihypertensive effects of acebutolol, a cardioselective beta-adrenergic blocking agent. In the acute experiment, six females were used. Acebutolol (3 mg/kg, i.v.) alone or in combination with furosemide (1 mg/kg, i.v.) or hydralazine (1 mg/kg, i.v.) was administered through an implanted catheter. In the chronic experiments, five females received oral acebutolol (100-200 mg/day). The blood pressure, heart rate, plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were used as parameters. In the acute experiment, there were no marked changes in the blood pressure or heart rate during the nondosing period. Acebutolol alone caused a marked decrease in the blood pressure and heart rate. In the two combination tests, combined administration with acebutolol and furosemide had a greater effect on the blood pressure and heart rate than did acebutolol alone. A combined acebutolol and hydralazine regimen caused a slight reduction not only in the blood pressure, but also in the heart rate compared with acebutolol alone. PRA and PAC remained essentially constant, with minor fluctuations, throughout the nondosing period. Following the injection of acebutolol alone, PRA showed an elevation with a significant rise after three hours and PAC showed a tendency to increase. PRA and PAC generally tended to increase in the case of combined administration with furosemide or hydralazine, but these tendencies were less conspicuous than with acebutolol alone. On the other hand, chronic treatment with acebutolol produced a significant decrease in the heart rate from two weeks after the administration and in the blood pressure from four weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Acebutolol↗
PubMed1986

Elicited antibody nature of human monoclonal protein with anti-streptolysin O activity--analysis with monoclonal anti-idiotype antibody.

Sera from 7 patients with multiple myeloma having antistreptolysin O (ASO) activity in high titers were detected by a streptolysin O (SLO) inhibition assay. However, activity was in low titer when assayed by a passive agglutination assay. The discrepancy between these 2 assays raised some doubts as to whether these monoclonal proteins (M.protein) bond to SLO in the same manner as elicited antibodies. Immunochemical analysis and idiotope analysis using monoclonal antibody to one of these M.proteins strongly suggest that M.protein with ASO activity bind to SLO in a manner similar to elicited antibody. The discrepancy between the 2 assays might be due to differences in the antigenic structure of different forms of the SLO molecule.

Antibodies↗