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Biomedical subjects

A Shigematsu

Publications and source records attributed to A Shigematsu.

At least 73 records · Page 4Linked to original sources
PubMed1997

In vitro method for assessing hepatic drug metabolism.

We investigated an in vitro metabolic test using rat liver biopsy samples by TLC-autoradioluminography (ARLG), with a view to developing a method to rapidly assess the drug metabolizing activities of individual patients. Drug metabolizing activity was measured in liver biopsy samples collected from rats in four groups: a female control group, male control group, phenobarbital (PB)-administered male group and cimetidine (CM)-administered male group. The productivity of metabolites of 7-ethoxycoumarin (7-EC), debrisoquine (DB) and diazepam (DZ), respectively, was lower in the female control group than in the male control group, but there were no differences in the productivity of metabolites of 5-fluorouracil (5-FU) and tolbutamide (TB), respectively, between the male and female control groups. Those of 7-EC, TB and DZ were higher in the PB-administered group than in the male control group, but those of DB did not differ between these two groups. Those of 5-FU, 7-EC, TB, DB and DZ were lower in the CM-administered group than in the male control group. Using TLC-ARLG, we could detect drug metabolites in rat liver biopsy samples in a relatively short time span at low concentrations similar to those in vivo. We could also measure drug metabolizing activity in cases with and without the involvement of cytochrome P450. When applied in clinical metabolic tests, TLC-ARLG is expected to be useful for assessing the drug metabolizing activities of patients.

Animals↗
PubMed1996

Inhibitory effects of propofol on catecholamine secretion and uptake in cultured bovine adrenal medullary cells.

In the central and peripheral noradrenergic neurons, the balance between noradrenaline release and reuptake determines the level of noradrenaline at the synaptic cleft or the nerve ending. In the present study, we examined the effects of propofol, an intravenous general anaesthetic, on catecholamine secretion and noradrenaline uptake in cultured bovine adrenal medullary cells and on the serum noradrenaline and blood pressure in rats. In cultured adrenal medullary cells, propofol (10-50 mumol/l) concentration-dependently inhibited catecholamine secretion stimulated by carbachol. Propofol suppressed carbachol-evoked 22Na+ influx as well as 45Ca2+ influx at concentrations similar to those which suppressed the catecholamine secretion. Propofol (10-50 mumol/l) also inhibited veratridine-evoked 22Na+ influx, 45Ca2+ influx and catecholamine secretion, whereas it had little effect on the 45Ca2+ influx and catecholamine secretion induced by 56 mmol/l K+. Cultured adrenal medullary cells show [3H] noradrenaline uptake which is sensitive to imipramine. Propofol (10-50 mumol/l) significantly inhibited the imipramine-sensitive uptake of [3H] noradrenaline. In rats, intravenous administration of propofol (2.5 mg/kg) lowered serum noradrenaline and arterial blood pressure. From these findings, in spite of inhibiting noradrenaline uptake, propofol at anaesthetic concentrations (10-30 mumol/l) seems to reduce catecholamine secretion by interfering with Na+ influx through voltage-dependent Na+ channels as well as nicotinic acetylcholine receptor-associated ion channels in the adrenal medulla and, probably, in the sympathetic nervous system. This may explain the propofol-induced hypotension during anaesthesia.

Adrenal Medulla↗
PubMed1996

Cricoid pressure impedes positioning and ventilation through the laryngeal mask airway.

PURPOSE: To assess the effect of cricoid pressure on the positioning of and ventilation through the laryngeal mask airway (LMA). METHODS: In a double-blind, randomized design, the LMA was inserted with (CP[+] group, n = 20) or without double-handed cricoid pressure (CP[-] group, n = 20). Ventilation through the LMA was assessed by measuring expiratory tidal volume and judged as adequate when a mean expiratory tidal volume of > or = 10 ml.kg-1 could be obtained. The LMA position was examined by fibreoscopy. The position of the mask relative to the cricoid cartilage and the cervical spine was radiologically examined (n = 10 in each group). RESULTS: Ventilation was adequate in all patients in the CP[-] group but in only five patients (25%) of the CP[+] group (P < 0.001). The glottis was visible fibreoptically below the mask aperture in all patients in the CP[-] group, but in only three patients in the CP[+] group (P < 0.001). Fibreoscopy showed that the mask was not inserted far enough in the remaining 17 patients of the CP[+] group. The reason for unsuccessful ventilation in the CP[+] group was excessive gas leakage (n = 2) and/or partial or complete airway obstruction (n = 13), which was noted fibreoptically. The radiographs showed that the tip of the mask in the CP[-] group was located below the level of the cricoid cartilage (C6 or C7 vertebra). The mask tip in the CP[+] group was above this level (C4 or C5 vertebra) (P < 0.01). CONCLUSION: Cricoid pressure impedes positioning of and ventilation through the LMA.

Adult↗
PubMed1996

Use of the fibrescope-video camera system for difficult tracheal intubation.

We describe an alternative technique for difficult intubation using a fibrescope and a video camera system. The fibrescope attached to the video camera was passed nasally, which provided a view of the larynx on the monitor screen. Then the operator inserted a tracheal tube into the trachea orally using a second fibrescope or a stylet under video visual control. This technique permits a view of the tube passing through the vocal cords in patients who present difficulty in intubation.

Fiber Optic Technology↗
PubMed1996

Inhibitory effect of adrenomedullin on rat mesangial cell mitogenesis.

We investigated the effects of adrenomedullin on rat mesangial cell proliferation. Adrenomedullin (10(-10)-10(-7) M inhibited both [3H]thymidine incorporation into cultured rat mesangial cells and cell proliferation in a concentration-dependent manner. Adrenomedullin (10(-10)-10(-6) M) stimulated cyclic adenosine monophosphate accumulation in rat mesangial cells in a concentration-dependent manner. These findings suggest that adrenomedullin inhibits proliferation of rat mesangial cells probably through a cyclic adenosine monophosphate-dependent mechanism.

Adrenomedullin↗
PubMed1996

Inhibition by protamine of catecholamine secretion and ion influxes in bovine adrenal medullary cells in culture.

To elucidate the mechanism of protamine-induced hypotension, we examined the effects of protamine on catecholamine secretion in bovine adrenal medullary cells and on the serum norepinephrine in the rat. 1) in bovine adrenal medullary cells in culture, protamine at concentrations of 10 to 100 micrograms/ml inhibited catecholamine secretion stimulated by carbachol. The inhibitory effect of protamine was diminished by heparin at concentrations of 3.5 to 14 U/ml. Protamine suppressed carbachol-stimulated 22Na+ influx and 45Ca++2 influx at a concentration similar to that which inhibited catecholamine secretion. Protamine (10-100 micrograms/ml) also inhibited veratridine-induced 22Na+ influx and 45Ca++ influx and 56 mM K(+)-evoked 45Ca++ influx. The inhibition of these ion influxes by protamine was closely correlated with that of catecholamine secretion. 2) In rats, i.v. administration of protamine (10 mg/kg) attenuated the arterial blood pressure and the serum norepinephrine. There was a high correlation (r = 0.96) between the serum norepinephrine and the arterial blood pressure in protaminetreated rats. Furthermore, pretreatment with heparin (1000 U/kg) abolished the protamine-induced decreases in arterial blood pressure and serum norepinephrine. Because protamine seems to inhibit catecholamine secretion by interfering with Na+ influx and Ca++ influx to adrenal medullary cells, the protamine-induced hypotension may be, at least in part, due to inhibition of norepinephrine release and ion channel activities of sympathetic nerve terminals in rats.

Adrenal Medulla↗
PubMed1996

Cytolysis of B-16 melanoma tumor cells mediated by the myeloperoxidase and lactoperoxidase systems.

Halide-dependent cytolysis of B-16 melanoma cells mediated by myeloperoxidase and lactoperoxidase systems was observed by turbidimetry. A significant decrease in turbidity, which is indicative of cytolysis, was found when a system consisting of myeloperoxidase, a source of hydrogen peroxide (glucose+glucose oxidase), and chloride or bromide were added to a B-16 melanoma cell suspension in the pH 4.7-6.0 region. The myeloperoxidase could be replaced by lactoperoxidase in the system containing bromide, but not that containing chloride. B-16 melanoma cells exposed to myeloperoxidase or lactoperoxidase systems at pH 5.5 or 7.0 were implanted by subcutaneous inoculation into C57BL/6CrSlc mice. After 14 days, a significant suppression of the growth of black tumors was detected in the groups of mice inoculated with melanoma cells exposed to the systems containing myeloperoxidase, glucose, glucose oxidase and chloride or bromide, or the system containing lactoperoxidase, glucose, glucose oxidase and bromide, at pH 5.5, but no significant suppression was observed at pH 7.0. From these findings, we concluded that the exposure of B-16 melanoma cells to a system consisting of myeloperoxidase, hydrogen peroxide (generated by the glucose+glucose oxidase system) and chloride or bromide, or of lactoperoxidase, the hydrogen peroxide and bromide, at moderately acidic pH, causes cytolysis is accompanied by cell death.

Animals↗
PubMed1995

Progressive application of autoradiography in pharmacokinetic and metabolic studies for the development of new drugs.

Autoradiographic data of distinctive tissue distributions of 14C atoms obtained by labeling at two different positions of a new drug suggest the metabolic fates of each labeled compound in experimental animals. A more accurate determination of blood-brain barrier (BBB) damage in several regions was indicated by semimicroautoradioluminography, based on no passage of dopamine through the BBB. Autoradioluminography (ARLG) was useful for quantitative validation of whole body autoradiography (WBA) with both ordinal X-ray film and other detectors. In frozen specimens, a good correlation was obtained between the relative radioactivity, photostimulated luminescence (PSL), and liquid scintillation counting (LSC) values in each organ or tissue. However, the correlation was disturbed in lung, brain, bone, and adipose tissue after freeze-drying. In order to be listed in the regulatory items, WBA data must be quantitative as well. The paste-mold method presented here can be used to support WBA data. The thin-layer chromatography (TLC)-ARLG technique and its applications are also presented in this article. A blood concentration-time curve of both the parent compound and its unknown metabolites can be estimated with this technique.

Animals↗
PubMed1995

The triple airway manoeuvre for insertion of the laryngeal mask airway in paralyzed patients.

The efficacy of the triple airway manoeuvre (mouth opening, head extension and jaw thrust) for insertion of the laryngeal mask airway (LMA) was compared with the standard insertion method. One hundred paralyzed patients were allocated randomly into two groups: in the control group (n = 50) the LMA was inserted by the standard method, and in the other (TAM group, n = 50) by the triple airway manoeuvre. In ten patients of each group, the position of the LMA and the epiglottis was assessed radiographically before insertion, after insertion but before cuff inflation, and after cuff inflation. In all patients the position was examined using fibrescopy before and after cuff inflation. The mean distance between the epiglottis and the posterior pharyngeal wall, measured radiographically before LMA insertion, was greater in the TAM group (16.3 (SD 4.3) mm) than in the control group (7.0 (2.8) mm) (P < 0.001). Before cuff inflation, radiography and fibrescopy showed that the LMA compressed the epiglottis downwards more frequently in the control group. After cuff inflation the glottis was completely visible fibreoptically in 66% in the TAM group, compared with 14% in the control group (P < 0.001). Complete downfolding of the epiglottis was seen in 10% in the control group and none in the TAM group (P < 0.05). We conclude that in paralyzed patients LMA insertion with the triple airway manoeuvre provides wider pharyngeal space and decreases the incidence of epiglottic downfolding by the LMA compared with the standard method.

Adult↗
PubMed1995

Role of nitric oxide during carrageenan-sensitized endotoxin shock in mice.

We have previously clarified that sensitization with a sulfated polygalactose, carrageenan (CAR), enhances endotoxin-induced tumor necrosis factor (TNF) production and lethality in mice. The present study was performed to examine the role of nitric oxide (NO) in CAR-sensitized septic mice with two different types of NO synthase (NOS) inhibitors, a non-selective inhibitor to NOS subtypes, N omega-nitro-L-arginine methyl ester (L-NAME), and a selective inhibitor to inducible NOS, aminoguanidine. Seven or eight-week-old male ddY mice were given 5 mg of CAR intraperitoneally as a primer. Then, 5 micrograms of lipopolysaccharide (LPS) was injected into the tail vein 16 hours later the pretreatment. Marked synthesis of NO was induced in CAR-sensitized mice, as indicated by the high plasma levels of the stable endproducts, NO2-/NO3- peaking at 12 hr after the LPS challenge. The peak values at 12 hr after the LPS challenge were dependent on the dose of CAR with 1 to 5 mg, although the injection with 10 mg of CAR was adversely inhibited NO production compared with 5 mg of CAR. The LPS challenge was followed by either L-NAME (0.25, 0.5 or 1 mg) or aminoguanidine (1, 2 or 4 mg) in the septic mice sensitized with 5 mg of CAR. L-NAME reduced the plasma NO2-/NO3- level in a dose-dependent fashion, although it augmented liver injury, as measured by plasma levels of ornithine carbamyltransferase (OCT) and the LPS-induced lethality in a dose-dependent fashion. In contrast, aminoguanidine did not significantly deteriorate either liver injury or lethality in spite of the decrease of NO endproducts in a similar fashion to L-NAME. These findings suggest that the inhibition of constitutive NOS is detrimental and augments LPS-induced liver injury and subsequent lethality.

Animals↗
PubMed1995

Studies on the quantitative autoradiography. III. Quantitative comparison of a novel tissue-mold measurement technique "paste-mold method," to the semiquantitative whole body autoradiography (WBA), using the same animals.

A novel preparation technique, so called "Paste Mold," was devised for organ and tissue distribution studies. This is the most powerful by joining with autoradioluminography (ARLG), which was established and validated recently in the working group of Forum '93 of Japanese Society for study of xenobiotics. A small piece (10-50 mg) of each organ or tissue was available for measuring its radioactive concentration and it was sampled from the remains of frozen carcass used for macroautoradiography (MARG). The solubilization of the frozen pieces was performed with mixing a suitable volume of gelatine and strong alkaline solution prior to mild heating kept at 40 degrees C for a few hours. After that, the tissue paste was molded in template pattern to form the small plates. The molded plates were contacted with Imaging plate (IP) for recording their radioactive concentration. The recorded IP was processed by BAS2000. The molded plate was formed in thickness of 200 microns, so called infinit thickness against soft beta rays, and therefore the resulting relative intensities, represented by (PSL-BG)/S values, indicated practically responsible ratio of the radioactive concentration in organs and tissues, without any calibulation for beta-self absorption coefficiency. On the other hand, the left half body of the frozen carcass was used for making whole body autoradiography (WBA) before the Paste-Mold preparation. Comparison was performed for difference in (PSL-BG)/S values of organs and tissues between frozen and dried sections. A good concordance in relative intensities, (PSL-BG)/S by the Paste-Mold preparation was given with those by the frozen sections rather than dried sections.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Studies on the quantitative autoradiography. IV. Quantitative reliability of TLC-autoradioluminography.

Phosphor Imaging plates (IPs) with high sensitivity to both low- and high-energy radiation have been on the market since 1988. The TLC-autoradioluminography (ARLG) method was developed utilizing such IPs. The conventional TLC method was suited for discrimination of microradioactive components; however, the method could only present semi-quantitative values. Conversely, the TLC-ARLG method showed completely quantitative values. That is, the TLC-ARLG method could be used to measure the radioactivity ratio between 14C-radiolabeled spots A and B, which were spotted 1 mm apart on a TLC plate, after development with chromatogram, not only when the radioactivity ratio between spots A and B was 1:1, but even when it was 16:1, within the measurement error of +/- 10%. The ARLG method showed sensitivity, resolution, and quantitative reliability far superior to those of the scraping-liquid scintillation counter (LSC) method or radiochromatoscanner method. In the future, the ARLG method will be widely used as a quantitative microanalytical method for unknown radioactive metabolites existing as microcomponents in organisms, especially for quantitative analysis considering mass balance to dose in biological samples, which is considered to be an important point in pharmacokinetic research.

Autoradiography↗
PubMed1995

Study of the de novo synthesis of cholesterol in the rat liver: a newly developed radiotracer technique, "TLC-autoradioluminography".

A possible evaluation technique was devised for examing timely cholesterol synthetic activity in the rat liver. The principle of the technique is to measure the incorporation rate of 14C atoms into a few target metabolites excreted in bile with time after an intraportal injection of [1,2-14C] acetate to the conscious rats. The measuring technique, TLC-autoradioluminography (TLC-ARLG), was devised for much more accurate, quantitative, simple and quick ultramicroanalysis of radioactive metabolites than ever before. Practically, a few microliters of the bile samples were analyzed by TLC before recording of a 2-dimensional radioactive image on the TLC plate. The incorporation ratio of 14C into cholesterol to succinic acid (C/S ratio) varied such that the value found in a 24-h fasting group was less than one-tenth of that in a sufficiently fed control group. For use as an antihyperglycemic drug, the bile C/S ratio in the nicotinic-acid-dosed group was approximately one-fifth of that in the control group.

Acetates↗
PubMed1995

Distribution volume of three 99mTc-labeled compounds in the rat liver with time after intraportal and intravenous injections.

With the aim of making direct investigational studies of various liver functions of sustained healthy animals, we devised operative procedures which are not only simple and reproducible but also adaptable to experiments even over the course of one-week without anesthesia. Using rats which have been operated upon, three kinds of tracers, 99mTc-pool scinti, 99mTc-pertechnetate and 99mTc-phytate, were recorded by a scintillation camera with a single-photon system immediately after intraportal administration. The results revealed that the discharge of these radioactive components from the hepatic vein began 0.2s after the administration, that the maximum intrahepatic concentration was reached between 2 and 5 s thereafter, and that 10 s later, these radioactive components were returned to the liver after their systemic circulation. Intrahepatic uptake of these three tracers was about 20% for all radioactivities administered.

Animals↗
PubMed1995

Studies on the quantitative autoradiography. I. Radioluminography for quantitative autoradiography of 14C.

Evidence is presented to elucidate whether or not quantitative analysis of autoradiographs can be obtained with a 14C-labelled compound by the use of a new type of radiosensor called Imaging plate (IP). Our results showed that a linear relationship between relative intensity of PSL-BG and radioactivity of a given area was obtained. The linearity was maintained in a relatively wide range from 10(1) to 10(5) dpm of radioactivity. About 100 times higher sensitivity of the IP than any commercially available X-ray film was demonstrated for not only 14C-radioactive standard sources but also experimentally obtained 14C-radioactive spots developed on a TLC plate. Results also showed a linear relationship between relative intensity and radioactivity of the specimens in a very wide range from 10(1) to 10(5) dpm/mg after exposure for 7d. Furthermore, the relationship between PSL-BG and relative exposure (radioactivity x exposure time) was linear when PSL-BG was from 10(1) to 10(5). In addition to the above properties, a combination of IP and BAS2000, a computerized image display system, was able to completely erase the background prior to use.

Animals↗
PubMed1995

Studies on the quantitative autoradiography. II. Radioluminography for quantitative autoradiography of 3H.

The process of obtaining 3H-autoradiographic (ARG) images has been expected for a long time. A few X-ray films with no protection layer are commercially available, however, they do not give a reliable image which can be quantitated and can give good contrast. We tried to fabricate a 3H-type sensor which has no protection layer on a highly sensitive sensor, and called it Imaging plate (IP). The IP is composed of one of the specially designed photo-stimulable phosphors containing of BaFX: Eu2+(X = Cl, Br or I) crystals. Results indicated a good contrast and reliable whole-body ARG image of 3H-labelled glucose with trial IP, which has never been obtained with any X-ray films even if these were subjected to a long exposure time. The ARG image can be displayed by either black-and-white hard copy or a colored one with the digital display representing relative intensity of photostimulated luminescence (PSL) without back ground (BG) or relative intensity concentration ((PSL-BG)/S), where S was equivalent to 100 pixels (1 mm2). Similarly to the experimental results of 14C, the linear relationship relative intensity and radioactivity of the 3H standard sources was demonstrated with a very wide range of 10(2) to 10(5) dpm/mg upon the exposure for 7d. Also the relationship between relative intensity and relative exposure (radioactivity x exposure time) was linear within the latitude of relative intensity 10(1) to 10(5) (PSL-BG). The trial IP was particularly effective for the quantitative autoradiography of TLC plates.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗