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Biomedical subjects

S Sawada

Publications and source records attributed to S Sawada.

At least 289 records · Page 16Linked to original sources
PubMed1992

Application of expandable metallic stents to the venous system.

Expandable metallic stents were successfully introduced in 12 patients; 6 with superior vena cava (SVC) obstruction due to tumor invasion or lymph node metastases, 3 with inferior vena cava (IVC) obstruction or stenosis due to lymph node metastases or hepatic tumor, one with common iliac vein (CIV) obstruction due to lymph node metastases, one with idiopathic obstruction of the hepatic IVC and Budd-Chiari syndrome, and one with CIV obstruction following a dialysis shunt. The length of the lesions was between 2 and 15 cm. Multiple (2-7) stents in tandem were inserted percutaneously from a femoral venous approach through a 12 to 16 F (4.0-5.3 mm) Teflon sheath. Postoperatively, all 12 patients became free from symptoms such as SVC syndrome or IVC syndrome. In 11 patients, the symptoms did not recur during the follow-up periods of 1 to 21 months.

Adult↗
PubMed1991

[Clinical experience of expandable metallic stent placement for malignant biliary obstruction].

Expandable metallic stents of modified Gianturco design were used in nine cases of malignant biliary obstruction. Stents were placed through a percutaneous transhepatic approach without any severe complications. Initial patency was obtained seven of nine patients. Of these seven patients, recurrent jaundice was observed in three within four weeks. One patient had recurrent stenosis after four months due to ingrowth of the tumor. Although the expandable metallic stent offers several theoretical advantages over currently available stents, a disadvantage is that tumors may grow through the spaces between the legs of the wire or grow over the stent. We found that multi-modal treatment combined with radiation therapy was indispensable to maintain the patency of the stent in malignant biliary obstruction.

Aged↗
PubMed1991

[An animal experiment on arterial wall reaction to stents coated with gold, silver and copper].

Expandable metallic stents coated with gold, silver, and copper, and bare stainless steel stents were implanted into the abdominal aorta of eight dogs to determine their effect on the vessel wall. The animals were observed for two weeks. Abdominal angiograms were taken every week. The dogs were then killed for macroscopic and histopathological examination. The results were as follows. (1) The stents coated with gold and the noncoated stainless steel stents showed less histopathologic change than the other stents. (2) The stents coated with copper were associated with severe erosion of the vessel wall and marked thrombus formation.

Animals↗
PubMed1991

Persistent enhancement of transmitter release accompanying long-term potentiation in the guinea pig hippocampus.

In order to examine temporal changes in enhancement of transmitter release during long-term potentiation (LTP), we examined amplitude fluctuation of excitatory postsynaptic potentials (EPSPs) for longer periods than 2 h after tetanic stimulation (up to 4 h in the longest observation). The relative magnitude of excitatory postsynaptic potentiation (EPSP) fluctuation (coefficient of variation, CV) reduced throughout the observation periods in association with an increase in EPSP amplitude after tetanic stimulation. The reciprocals of squared CVs (= mean2/variance) were almost in proportion to the magnitude of LTP, and the ratio of 1/CV2 and the LTP magnitude did not change significantly for up to 4 h. These findings suggest that a prolonged enhancement of transmitter release from presynaptic terminals underlies LTP, and the relative contribution of this presynaptic enhancement does not change significantly for 2 h (maybe up to 4 h, or longer) after tetanic stimulation.

Animals↗
PubMed1991

[Experimental study of endoesophageal and intestinal expandable metallic stent placement].

Gianturco expandable metallic stents were implanted into the esophagus and small intestine of 10 rabbits in order to evaluate the influence of wire stents on the gastrointestinal tract. The stents were constructed of 0.010 inch stainless steel wire. The relaxed diameter of the stents was 12-14 mm and the length was 10 mm. Except for one stent placed in the small intestine, the stents did not migrate and were covered with thickening mucosal epithelium. The mucosal inflammatory changes were slight, but severe intestinal adhesions were noted. The findings in the two groups were not significantly different at three and six weeks. Five rabbits died within three weeks of intestinal disorders caused by severe intestinal adhesions and/or perforations. The experimental data showed that implantation of metallic wire stents into the gastrointestinal tract resulted in severe damage to the esophagus and small intestine of rabbits.

Animals↗
PubMed1991

Enhancement of transmitter release accompanying with long-term potentiation in synapses between mossy fibers and CA3 neurons in hippocampus.

This study was performed to answer the question whether long-term potentiation (LTP) in mossy fiber-CA3 synapses is accompanied by an enhanced release of transmitter. For this purpose, the relative magnitude of amplitude fluctuation (coefficient of variation, CV) of excitatory postsynaptic potentials (EPSPs) and the probability of transmission failures were examined in thin hippocampal sections from the guinea pig before and after tetanic stimulation of mossy fibers or alteration of Ca2+ concentration. The values of CV were reduced in association with increases in EPSP amplitude after tetanic stimulation or at high Ca2+ concentration. The probability of failures decreased after tetanic stimulation. These findings indicate an enhancement of release of transmitter from mossy fiber terminals after induction of LTP.

Animals↗
PubMed1991

[Self-expandable metallic stent for use in arterial occlusive lesions].

Gianturco expandable metallic stents were successfully placed in 4 patients with arterial occlusive disease: aortic obstruction or stenosis due to aortitis (n = 2), dissecting aneurysm (n = 1) and arteriosclerotic obstruction of the iliac artery (n = 1). The length of lesion was from 2 to 15 cm. In one case of aortitis (case 1), eleven stents (5 and 6 stents in tandem connected by wire struts) were inserted through a 12 F Teflon sheath. In another aortitis case (case 2) 4 stents in tandem were inserted through a 10 F sheath. In the two cases the sheaths were introduced by femoral arteriotomy. In case 3 and 4 two or four stents in tandem were placed through a 8 F long sheath which was introduced via the femoral artery by Seldinger method. Symptoms disappeared after placement of stents in all four cases. Our results showed the usefulness of expandable metallic stents in the treatment of arterial occlusive diseases.

Adult↗
PubMed1991

Quantal components of the synaptic potential induced in hippocampal neurons by activation of granule cells, and the effect of 2-amino-4-phosphonobutyric acid.

The probabilistic nature of excitatory postsynaptic potentials (EPSPs) induced monosynaptically in CA3 neurons by impulses of granule cells was studied in thin transverse sections of the guinea pig hippocampus. More than 600 EPSPs were recorded under several conditions, their amplitudes were measured, and histograms representing the EPSP amplitude distribution were constructed. Quantal parameters were estimated by the method of maximum likelihood. Of 9 neurons examined in the control solution, one neuron showed an exceptionally large number of transmission failures. The amplitude distribution of EPSPs recorded from this neuron could be described by Pascal statistics, but not by binomial or Poisson statistics. The EPSP amplitude distribution from the other neurons could be described by either binomial, Poisson, or Pascal predictions with a minor preference for the last statistic. When an apparently homogeneous group of data was divided into two subgroups and parameters were estimated separately, inconsistent values were obtained in some neurons with no failures. 2-Amino-4-phosphonobutyric acid (APB) suppressed the EPSPs reversibly at relatively low concentrations. Theoretical curves calculated according to the Pascal statistics fit quite well to the entire amplitude distribution of EPSPs recorded under the action of APB. The suppression of EPSPs by APB was accompanied by a marked decrease in mean quantal content (m) with no significant reduction in mean quantal amplitude (q). A quantum induced an increase in membrane conductance of about 150 pS. These results suggest that the release probability of the mossy fiber terminal fluctuates temporally according to a gamma distribution, and that APB reduces the liberation of the transmitter from mossy fiber terminals, thereby suppressing transmission between mossy fibers and CA3 neurons.

Aminobutyrates↗
PubMed1991

Functional T cell subpopulations responsible for hyposecretion of IL-2 in patients with systemic lupus erythematosus.

The ability of T cells to secrete IL-2 in patients with systemic lupus erythematosus (SLE) was investigated. In patients with SLE, impaired IL-2 production by peripheral blood lymphocytes stimulated with mitogens is well known. In this paper, we report that purified T cells stimulated with mitogens, in the presence of Epstein-Barr virus transformed B cells (B-LCL) as an accessory cell, however, could secrete a large quantity of IL-2 as much as normal T cells. In order to study this potential capacity of T cells to secrete IL-2 in patients with SLE, IL-2 secreting T cells were examined. To obtain these cells, T cells were divided into cluster forming cells and noncluster forming cells after short culture of T cells with accessory cells in the presence of Con A. Then the ability of IL-2 production in two kinds of separated T cells was examined. We found that 1) after short culture with B-LCL, the cluster forming T cells could secrete IL-2 when cultured again, but non-cluster forming T cells could not, even in the presence of B-LCL, 2) after short culture with macrophages, in normal donors and SLE patients, noncluster forming T cells were able to secrete a greater amount of IL-2 than cluster forming and undivided T cells when cultured with B-LCL.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Effects of an immunosuppressant, FK506, on interleukin 1 alpha production by human macrophages and a macrophage-like cell line, U937.

A recently discovered immunosuppressive agent, FK506, has been shown to be effective primarily as an inhibitor of T cell responses in vitro, but little is known about its effects on accessory cell function. This study was undertaken to determine the effect of FK506 on interleukin 1 (IL-1) production by macrophages, by using a sensitive and specific enzyme-linked immunosorbent assay. FK506 partially suppressed IL-1 alpha release, from macrophage-like U937 cells stimulated with phorbol myristate acetate and from human monocytes and alveolar macrophages activated with lipopolysaccharide, in a dose-dependent manner. Moreover, it was indicated that FK506 suppressed not only IL-1 release but also IL-1 synthesis itself, by measurement of cell-associated IL-1 alpha of U937 cells. The optimal concentrations of FK506 for suppressing IL-1 alpha did not affect cell viability or proliferation, and were 10- to 100-fold lower than those of cyclosporin A. It is concluded that FK506 affects macrophage physiology, suppressing IL-1 alpha production significantly. Thus, FK506 has the potency to act on non-T cells and the effect on macrophages may play an additional role in preventing graft rejection.

Anti-Bacterial Agents↗
PubMed1991

Chromosome aberrations, micronuclei and sister-chromatid exchanges (SCEs) in rat liver induced in vivo by hepatocarcinogens including heterocyclic amines.

The induction of chromosome aberrations, micronuclei and SCEs was studied in hepatocytes of F344 rats exposed in vivo to hepatocarcinogens. Hepatocytes were isolated and allowed to proliferate in Williams' medium E supplemented with epidermal growth factor. Cells were fixed after a culture period of 48 h. Oral administration of dimethylnitrosamine at doses of 2.5-20 mg/kg body weight (bw) induced (1) chromosome aberrations in up to 27% of the metaphase cells 2-48 h after its administration, (2) SCEs with a frequency of up to 0.9 per chromosome 2-48 h after its administration, and (3) micronuclei in up to 2.9% of the cells 16-48 h after its administration. Oral administration of 2-acetylaminofluorene at doses of 6.25-200 mg/kg bw induced (1) chromosome aberrations in up to 35% of the metaphase cells after 2-48 h, (2) SCEs at up to 0.9 per chromosome and (3) micronuclei in up to 2.5% of the cells with a maximum after 4 h. Oral administration of CCl4, a non-genotoxic hepatocarcinogen, at a dose of 1600 mg/kg bw did not induce chromosome aberrations, SCEs or micronuclei within 4-72 h. Intraperitoneal injections of Trp-P-1, Glu-P-1, MeIQx, IQ and nitro-IQ resulted in chromosome aberrations in up to 16% of the metaphase cells and SCEs at up to 0.9 per chromosome, while injections of Trp-P-2 and Glu-P-2 produced SCEs at up to 0.7 and 1.1 per chromosome, respectively. The present method of in vivo cytogenetic assay using rats without partial hepatectomy or mitogen treatment in vivo should be useful for evaluating the tumor-initiating activities of hepatocarcinogens.

Amines↗
PubMed1991

Comparative studies of angiotensin converting enzyme inhibitors with and without the SH-radical.

This study was conducted to evaluate the effects of an SH-radical in an angiotensin converting enzyme (ACE) inhibitor on PGI2 generation, intracellular cGMP, and Ca2+ kinetics in vascular endothelial cells. In the cultured human umbilical vein endothelial cells, the non-SH containing ACE inhibitors, delapril and enalapril, did not result in significant changes in cGMP concentrations. By comparison, captopril significantly (P less than .01) increased cGMP concentrations. Only captopril showed a significant (P less than .01) effect on 45Ca kinetics in cultured human vascular endothelial cells. Captopril also decreased PGI2 generation in vascular endothelial cells. These effects were not seen with delapril or enalapril. The significance of the SH moiety in ACE inhibitors remains controversial. However, these results suggest that there could be differences in the vascular actions of ACE inhibitors related to the presence or absence of SH radical.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1991

9-(Dicyanovinyl)julolidine binding to bovine brain calmodulin.

A molecular rotor, 9-(dicyanovinyl)julolidine (DCVJ), is a fluorescent dye whose intramolecular rotation determines its fluorescence yield [Kung, C.E. & Reed, J.K. (1989) Biochemistry 28, 6678-6686]. DCVJ binds to bovine brain calmodulin and emits strong fluorescence. In fluorescence titration experiments, the dissociation constant and the number of binding sites were determined to be 20 +/- 10 microM and 0.7 +/- 0.5 in the presence of Ca2+, and 22 +/- 10 microM and 0.6 +/- 0.5 in the absence of Ca2+, respectively. The fluorescence intensity of bound DCVJ increased 10-fold in the presence of Ca2+ compared to that in the absence of Ca2+. The fluorescence titration curve of DCVJ-calmodulin showed a transition at pCa 6.5. Over the same Ca2+ range, a decrease in molecular ellipticity at 222 nm and an increase in tyrosine fluorescence of calmodulin were observed. These results mean that the conformational change of calmodulin due to the Ca2+ binding induces the microenvironmental change of the DCVJ binding site from the flexible to the rigid state, resulting in inhibition of the intramolecular rotation of DCVJ and an increase in its fluorescence.

Binding Sites↗