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Biomedical subjects

S Ichikawa

Publications and source records attributed to S Ichikawa.

At least 361 records · Page 20Linked to original sources
PubMedDate not supplied

MRI of the gastroepiploic artery used as a bypass graft.

The right gastroepiploic artery (RGEA) is recognized for its long-term patency as a coronary artery bypass graft, a property shared with the internal thoracic artery. The usefulness of MRI for noninvasive visualization and evaluation of the RGEA graft was assessed using a spine coil as the surface coil in 14 patients with graft patency verified by postoperative angiography. The graft was visualized by spin-echo imaging as a signal-void surrounded by lipomatous tissue with high-signal intensity in all 14 cases. Cine MRI was also performed in 13 of the 14 patients; in each case the graft was confirmed to contain blood flow of high-signal intensity.

Arteries↗
PubMedDate not supplied

Effect of long-term hormone replacement therapy on angiotensin-converting enzyme activity and bradykinin in postmenopausal women with essential hypertension and normotensive postmenopausal women.

OBJECTIVE: Hormone replacement therapy (HRT) reduces the incidence of cardiovascular disease in postmenopausal women. Three-month short-term HRT in postmenopausal women with essential hypertension increased the plasma concentrations ofbradykinin with decreased serum angiotensin-converting enzyme (ACE) activity, which may be partially responsible for the cardioprotective effects of HRT. The objective was to determine whether 12-month long-term HRT in postmenopausal women with essential hypertension would maintain the decreased ACE activity and increased bradykinin levels and whether long-term HRT would increase the plasma bradykinin concentrations of normotensive postmenopausal women who had shown no significant changes in the 3-month HRT study, despite their decreased serum ACE activity. DESIGN: Twenty hypertensive and 15 normotensive postmenopausal women were treated with conjugated estrogens (0.625 mg/day) and medroxyprogesterone (2.5 mg/day) for 12 months. Twenty hypertensive and 15 normotensive postmenopausal women were used as controls. The controls were not treated with HRT. Serum ACE activity and plasma bradykinin concentrations were measured at baseline and at 12 months. RESULTS: Long-term HRT in both hypertensive and normotensive postmenopausal women significantly decreased serum ACE activity from 15.5+/-0.7 IU/L and 16.0+/-0.9 IU/L, respectively, at baseline to 13.3+/-0.5 IU/L and 14.2+/-0.9 IU/L, respectively, 12 months after the start of HRT (p < 0.05 and p < 0.05, respectively). Long-term HRT in both hypertensive and normotensive postmenopausal women also significantly increased plasma bradykinin concentrations from 22.1+/-4.4 pg/mL and 19.2+/-3.0 pg/mL, respectively, at baseline to 86.7+/-21.2 pg/mL and 73.5+/-23.0 pg/mL, respectively, 12 months after the start of HRT (p < 0.01 and p < 0.05, respectively). No significant changes in serum ACE activity or plasma bradykinin concentrations were observed in the control groups. CONCLUSIONS: Long-term HRT in hypertensive and normotensive postmenopausal women decreases their serum ACE activity and increases their plasma bradykinin concentrations. Thus, maintenance of elevated bradykinin with decreased serum ACE activity by HRT may be useful in reducing the risk of cardiovascular disease in both hypertensive and normotensive postmenopausal women.

Administration, Oral↗
PubMedDate not supplied

Operating point control system for a continuous flow artificial heart: in vitro study.

We proposed and developed a practical and effective servo control system for rotary blood pumps. A rotary blood pump for assisting the failing natural heart should be operated only in physiologically acceptable conditions. The operation of a rotary blood pump is based on the rotational speed of the impeller and pressure head. If the pump flow and the pressure head are set within an acceptable range, the driving condition is deemed normal condition, and this control system maintains the preset operating point by applying proportional and detective control (PD control). If the pump flow or pressure head is outside the acceptable range, the driving condition is determined to be abnormal condition, and this system operates the pump in a recovery fashion. If the driving condition is kept under abnormal conditions of sudden decrease of the flow, the condition is termed a suction condition. The controller releases the pump from the suction condition and later returns it to the normal condition. In this study, we evaluated these servo control modes of the centrifugal pump and confirmed whether the performance of this proposed operating point control system was practical.

Algorithms↗
PubMedDate not supplied

Evaluation of floating impeller phenomena in a gyro centrifugal pump.

The Gyro centrifugal pump, developed as a totally implantable artificial heart, was designed with a free impeller in which the rotational shaft (male bearing) of the impeller was completely separated from the female bearing. For this type of pump, it is very important to keep the proper magnet balance (impeller-magnet and actuator-magnet balance) to prevent thrombus formation or bearing wear. When the magnet balance is not proper, the impeller is jerked down into the bottom bearing. On the other hand, if magnet balance is proper, the impeller is lifted off the bottom of the pump housing within a certain range of pumping conditions. In this study, this floating phenomenon was investigated in detail. The floating phenomenon was proven by observation of the impeller behavior by means of a transparent acrylic pump. The impeller floating phenomenon was mapped on a pump performance curve. The impeller floating phenomenon is affected by the magnet-magnet coupling distance and the rotational speed of the impeller. To keep the proper magnet balance and to maintain the impeller floating phenomenon at the driving conditions of right and left pumps, the magnet-magnet coupling distance was altered by a spacer that was installed between the pump and actuator. It became clear that the same pump could handle different conditions (right and left ventricular assist) by changing the thickness of the spacer. When magnet balance is proper, the floating impeller phenomenon occurs automatically in response to the impeller revolution. This is called "the dynamic revolutions per minute suspension."

Centrifugation↗
PubMedDate not supplied

Marked retention of indocyanine green and sulfobromophthalein with chronic persistent hepatitis.

A hepatitis B virus (HBV) carrier with marked retention of indocyanine green (ICG) and sulfobromophthalein (BSP) was admitted to our hospital for assessment of liver function. On admission, he was asymptomatic and blood chemistry tests showed normal values for transaminases and bilirubin. Serum hepatitis B surface antigen (HBsAg) and antibody to hepatitis B e antigen (anti-HBe) were positive. A history of drug abuse or alcoholism was denied. Dye excretion tests revealed marked retention of ICG (R15 = 70%) and BSP (R45 = 23%). Histopathological examination of a liver biopsy specimen obtained during laparoscopic observation showed chronic persistent hepatitis (CPH). Familial research of the patient failed to prove the existence of dye excretory defect in his siblings. Usual cases of CPH due to continuous HBV infection do not show such severe disturbance of organic anion transport. This pattern of the dye excretory defect with CPH has not been reported. Although the relationship between this dye excretory defect and HBV infection is unclear, the existence of the constitutional dye excretory defect due to abnormal organic anion transport in the liver might be considered.

Carrier State↗
PubMedDate not supplied

Neuropeptide signaling of lymphocytes in immunological responses.

Peptidergic nerves in immune organs and lymphoid tissues of the lungs and gastrointestinal tract end on or in close proximity to lymphocytes, mast cells and macrophages. Vasoactive intestinal peptide, substance P and some other neuropeptides, that are recognized by distinct sets of cell surface receptors, regulate aspects of T cell differentiation in the thymus, such as negative selection, and contribute to mediating compartmental immune responses. The latter effects include stimulating expression of adhesive proteins by lymphocytes, enhancement of lymphocyte and macrophage migration in vascular and connective tissues, and modulation of proliferative and synthetic responses of lymphocytes to diverse antigens.

Animals↗
PubMedDate not supplied

Plasma adiponectin levels in post-menopausal women receiving hormone replacement therapy.

This study aimed to evaluate the correlation between plasma adiponectin levels and plasma lipid and lipoprotein levels in post-menopausal women (PMW) receiving hormone replacement therapy (HRT). Various clinical and biochemical parameters, including plasma lipid and lipoprotein concentrations and adiponectin levels, were measured in 54 healthy PMW before and after 3 and 6 months of HRT. Control groups consisted of women aged < 40 years (n = 20) or > 60 years (n = 17). PMW had significantly lower baseline adiponectin levels compared with the younger or older control groups, but adiponectin concentrations were not significantly altered after 3 or 6 months of HRT. Adiponectin levels in PMW were positively correlated with plasma high-density lipoprotein-cholesterol levels and were negatively correlated with body mass index and triglyceride levels. Our data suggest that circulating adiponectin may contribute to lipid homeostasis in PMW. Further studies are needed to elucidate the effects of HRT and oestrogen on adiponectin levels.

Adiponectin↗
PubMedDate not supplied

Effect of antihypertensive therapy on blood rheology in patients with essential hypertension.

Hypertension is an important risk factor for cardiovascular disease, and antihypertensive drugs can decrease the occurrence of such events in hypertensive patients. This study compared the rheological properties of blood in 22 untreated hypertensive patients, 42 patients taking antihypertensive drugs and 74 normotensive subjects. Using a microchannel method, the whole blood passage time was measured and blood movement was observed with a microscope connected to an image display unit. The blood passage time in untreated hypertensive patients was significantly higher than in treated hypertensive patients or normotensive subjects, but was similar in the latter two groups. Microscopic observations showed that platelet aggregation and leucocyte adhesion were increased in untreated hypertensive patients, resulting in poor flow, while blood samples from treated hypertensive patients and normotensive subjects passed smoothly through the microchannels. These rheological differences could contribute to the decrease in cardiovascular disease seen when hypertensive patients are treated effectively.

Adult↗
PubMedDate not supplied

Distribution of TNF endogenously induced by various immunopotentiators and Lactobacillus casei in mice.

Intravenous administration of heat-killed Lactobacillus casei YIT 9018 (LC) elicited endogenous cytotoxic factor (CF) production in ICR mice, peaking in serum after 2 h and declining gradually to basal level at 23 h. The endogenous CF production was significantly enhanced by priming with high molecular-weight lignins and glucans, but not by phenylpropenoid precursors or partially hydrolyzed products of glucans. The extent of stimulation of CF production by these priming agents was positively related to that of tumor necrosis factor (TNF) production, as judged by enzyme-linked immunosorbent assay. Endogenously produced TNF was concentrated more in liver, lung and intestine, as well as in serum, than in other organs. Histochemical examination revealed a significant increase in the number and swelling of Kupffer cells and sinusoidal endothelium in the liver of the treated mice.

Adjuvants, Immunologic↗
PubMedDate not supplied

Effects of a protein-bound polysaccharide from a basidiomycetes against hepatocarcinogenesis induced by 3'-methyl-4-dimethylaminoazobenzene in rats.

PSK, extracted from mycelia of a strain of Coriolus versicolor, was administered to groups of 20 male Wistar rats before and during treatment with 3'-methyl-4-dimethylaminoazobenzene (3-MDAB). After 24 weeks, the survival rates were significantly higher in the groups given PSK before or with the 3-MDAB than in groups not given PSK or given PSK after 12 weeks of 3-MDAB treatment. Blood alpha-fetoprotein levels, determined every four weeks, increased in all groups after 3-MDAB treatment, but were significantly lower in the groups given PSK before or with the 3-MDAB than in the other groups. The results indicate that PSK had a suppressive effect on 3-MDAB-induced hepatocarcinogenesis.

Animals↗
PubMedDate not supplied

Macrophage stimulation activity of antimicrobial N,N-dimethylaminoethyl paramylon.

Pretreatment with N,N-dimethylaminoethyl (DMAE) paramylon significantly protected mice from infection by various microorganisms. When mouse peritoneal macrophages were cultured with DMAE-paramylon, they showed morphological change (spreading) and elevated NBT-reducing activity. Macrophages prepared from DMAE-paramylon-treated mice had higher NBT-reducing activity than those from control mice. On the other hand, carboxymethyl paramylon and paramylon sulfate, which did not induce appreciable antimicrobial activity, failed to stimulate macrophage functions. The data suggest a significant role of macrophages in antimicrobial activity induction by cationized glucans.

Animals↗
PubMedDate not supplied

Stimulation of mouse peritoneal macrophages by lignin-related substances.

Various lignified materials, including pine cone extract and a commercial lignin, stimulated the morphological change (spreading) of mouse peritoneal macrophages, and their functional maturation as judged by increase in NBT-reducing activity. When these materials were treated with NaClO2 to decompose the phenolic structure, their activity was completely eliminated, whereas the activity was rather enhanced when they were treated with H2SO4 to decompose their sugar moiety. Some monomeric phenolic compounds structurally related to lignin components and several antitumor glucan derivatives had little or no macrophage stimulating activity. The results strongly suggest the importance of lignin-structure in macrophage activation.

Animals↗
PubMedDate not supplied

Chemical modification potentiates paramylon induction of antimicrobial activity.

Induction of antimicrobial activity by two water-insoluble polysaccharides, paramylon and TAK, was significantly potentiated by introduction of positively charged groups (such as N,N-dimethylaminoethyl; N,N-diethylaminoethyl; and 2-hydroxy-3-trimethylammoniopropyl), but not by introduction of negatively charged groups (such as carboxymethyl or sulfate). Cross-linking of these derivatives with epichlorohydrin did not increase their potentiating activity. The effects of these derivatives did not always correlate with their ability to accumulate polymorphonuclear cells and to stimulate the generation of luminol-dependent chemiluminescence by peritoneal exudate cells.

Animals↗
PubMedDate not supplied

Inhibition of herpes simplex virus infection by pine cone antitumor substances.

Several antitumor substances extracted from cones of various pine trees inhibited the plaque formation of Herpes simplex virus types 1 and 2 (HSV-1, HSV-2) strains in African green monkey kidney cells and human adenocarcinoma cells. The 50% effective dose of the most active fraction, Fr. VI (0.3 micrograms/ml) was 0.001 times its 50% cytotoxic dose (greater than 300 micrograms/ml). The anti-HSV activity of various pine cone extracts increased with their acidity. Identification of the polyphenol groups as donors of the acidity was further supported by the observation that the anti-HSV activity of the natural polyphenolic products, such as tannin and lignin, significantly exceeded that of other natural or chemically modified antitumor polysaccharides. An experiment using radiolabeled virus particles indicated that the anti-HSV effect of both Fr. VI and lignin was attributable to interference with virus adsorption to these cells rather than to inhibition of virus penetration into the cells.

Animals↗
PubMedDate not supplied

Mitogenic activity of pine cone extracts against cultured splenocytes from normal and tumor-bearing animals.

An acidic pine cone extract, Fr. V. of Pinus parviflora Sieb. et Zucc. significantly stimulated DNA synthesis of isolated splenocytes from both mice and rats, but only marginally affected the DNA synthesis of leukemic cell lines. The maximum stimulation level attained by Fr. V slightly exceeded that of plant lectins, whereas much weaker stimulating activity was found in natural and chemically modified antitumor polysaccharides, sialic acid-rich glycoproteins, and polyphenolic compounds such as lignin and tannic acid. In mice with subcutaneously transplanted sarcoma-180, responses of splenocytes against Con A declines in the terminal stage of tumor development, whereas responses against Fr. V remained relatively constant throughout all periods of tumor progression. The suppression of Fr. V activity by acetylation or methylation suggests the importance of the hydroxyl group in the expression of its stimulation activity.

Animals↗
PubMedDate not supplied

Methods of detection of lymphatics and their changes with oestrous cycle.

It is difficult to detect lymphatics, and it is extremely risky to identify a lymphatic by only one method. We are attempting accurate identification of a lymphatic by gradually narrowing the field of division by the use of four methods: (1) puncture injection of dye fluid; (2) arterial injection of silver nitrate solution and indian ink; (3) staining of semi- ultrathin sections with toluidine blue, and (4) confirmation by electron microscopy. Observation by these methods of the endometria of the human uterus and of rats in different stages of the respective oestrous cycles has revealed that the lymphatics change with the oestrous cycle. Interestingly, the changes are not only in the thickness but also in the number of lymphatics. Lymphatics have further been found not evenly distributed in organs but concentrated in certain areas.

Adult↗