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Biomedical subjects

I Horikoshi

Publications and source records attributed to I Horikoshi.

At least 73 records · Page 4Linked to original sources
PubMed1986

Characterization of histamine release in digitonin-permeabilized rabbit platelets.

To manipulate the intracellular milieu of rabbit platelets, permeabilization was performed using digitonin. Permeabilized platelets showed dose-dependent release of histamine, which was stored in granules of rabbit platelets, in response to extracellular calcium ion. As PMA stimulated the release reaction in digitonin-permeabilized platelets, the protein kinase C system, which regulates metabolic processes and cell reactions in intact platelets, was revealed to be working. Cupric phenanthroline also released histamine from permeabilized rabbit platelets dose-dependently, and dithiothreitol inhibited the release strongly. Since cupric phenanthroline is a mild oxidant which catalyzes the formation of disulfide bridges, as in the case of Ca2+-ATPase of sarcoplasmic reticulum, the results suggested that protein cross-linking is implicated in the regulation of the release reaction in permeabilized rabbit platelets.

Adenosine Triphosphate↗
PubMed1986

Purification and properties of a cytochrome b560-d complex, a terminal oxidase of the aerobic respiratory chain of Photobacterium phosphoreum.

A cytochrome b560-d complex, a terminal oxidase in the respiratory chain of Photobacterium phosphoreum grown under aerobic conditions, was purified to near homogeneity. The purified oxidase complex is composed of equimolar amounts of two polypeptides with molecular weights of 41,000 and 54,000, as determined by gel electrophoresis in the presence of sodium dodecyl sulfate. It contains 10.2 nmol of protoheme and 22.5 nmol of iron/mg of protein. The enzyme is a "cytochrome bd-type oxidase," showing absorption peaks at 560 and 625 nm in its reduced minus oxidized difference spectrum at 77K. This oxidase combined with CO, and its CO difference spectrum at room temperature in the Soret region showed a peak at 418 nm and a trough at 434 nm. In addition, a trough at 560 nm (cytochrome b), and a trough at 620 nm and a peak at 639 nm (cytochrome d) were observed in the CO-binding spectrum. This cytochrome b560-d complex catalyzed the oxidation of ubiquinol-1 and ascorbate in the presence of N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride or phenazine methosulfate. The oxidase activity required phospholipids and was inhibited by the respiratory inhibitors, KCN and NaN3, and the divalent cation, ZnSO4. Formation of a membrane potential by the cytochrome b560-d complex reconstituted into liposomes was observed with the fluorescent dye, 3,3'-dipropylthiodicarbocyanine iodide, on the addition of ubiquinol-1, showing that the enzyme provided a coupling site for oxidative phosphorylation.

Amino Acids↗
PubMed1986

EL-4 tumor cell-induced human and rabbit platelet aggregations.

EL-4 tumor cells were assayed in vitro for their ability to aggregate two kinds of platelets. An inhibition study showed that the EL-4 tumor cell can induce platelet aggregation by at least two different mechanisms. One, mediated by thrombin, was dominant with rabbit platelets because hirudin, which specifically inhibits thrombin, considerably suppressed the rabbit platelet aggregation induced by EL-4 tumor cells. In contrast, EL-4 cells induced the aggregation of human platelets even in citrated PRP. It is the apyrase-sensitive pathway that is believed to work in human platelets. The human platelet responses to EL-4 tumor cells clearly differed from those of rabbit platelets in terms of inhibition by hirudin and apyrase and of reactivity in citrated PRP. Both phospholipase A2 and dibutyryl cAMP strongly inhibited EL-4 tumor cell-induced platelet aggregation in both rabbit and human platelets. These two compounds may block a vital step in platelet aggregation that is elicited by the EL-4 tumor cells. Our results show that human platelet response to tumor cells is not necessarily deducible from experimental data obtained with animal platelets.

Animals↗
PubMed1986

Heparin-induced leukocyte lysis in vitro.

An investigation on the effect of heparin on leukocytes in vitro was conducted. We have demonstrated that heparin and other mucopolysaccharides destroyed leukocytes as judged by macromolecule leakage. The cytotoxicity of heparin was suppressed by protamine. A medium which mimics intracellular ionic conditions was found to suppress the cytotoxicity of heparin. Macromolecule leakage induced by heparin is thought to be facilitated by passive ion flux. Mepacrine, a phospholipase inhibitor, suppressed the heparin-induced macromolecule leakage from leukocytes. Thus, the activation of phospholipase appears to be involved in the cytotoxicity of heparin. These results suggest that activation of phospholipase and passive movement of ions may be important steps for the heparin-induced leukocyte lysis in vitro.

Animals↗
PubMed1986

Age-dependent changes in warfarin tissue distribution.

Whole blood levels, serum protein binding and tissue concentration following intravenous administration of warfarin were investigated in 1-d-old, 1-, 3- and 8-week-old rats to determine the drug disposition in the growth process. It was shown that the clearance of warfarin in 1-d-old or 1-week-old rats was considerably lower than that in 3- or 8-week-old rats. The decrease in clearance in infant and young rats was considered to be caused by the immaturity of the physiological function of the liver to remove exogenous compounds. The distribution volume in 1-d-old or 1-week-old rats was larger than that in 3- or 8-old rats. The percentages of serum free warfarin in 1-d-old and 1-week-old rats were about twice those in 3- and 8-week-old rats. The increased distribution volume in infant rats was considered to be caused by a lower serum protein binding in these rats.

Aging↗
PubMed1985

The change of p-aminohippuric acid disposition kinetics accompanied by growth in mice.

The change of disposition kinetics for p-aminohippuric acid (PAH) was studied following intravenous administration of p-[glycyl-1-14C]aminohippuric acid to 1-day-old, 1-week-old, 3-week-old and 8-week-old mice. The expiratory excretion of 14CO2 in 24 h following the administration was almost negligible in 1-day-old and 1-week-old mice in contrast to 3-week-old (6.8 +/- 1.8%) and 8-week-old (8.8 +/- 1.9%) mice. The ability to metabolize PAH may not be developed in these infant mice. The elimination of blood radioactivity following the administration was considerably delayed in 1-day-old and 1-week-old mice, especially in 1-day-old mice, suggesting that the renal tubular secretory function for PAH might not have been developed in the infant mice. Whole-body autoradiographic data showed that the transfer of PAH from blood to muscle was enhanced in 1-day-old and 1-week-old mice, especially in 1-day-old mice, compared to 3-week-old and 8-week-old mice. The enhanced muscular cell membrane permeability to PAH in 1-day-old and 1-week-old mice was considered to be the most plausible explanation for this result.

Age Factors↗
PubMed1984

Chemical reactivations of inactivated acetylcholinesterase after 2-PAM therapy in fenitrothion-poisoned rat and rabbit.

We investigated the reactivation of inactivated acetylcholinesterase (AChE) after 2-PAM therapy in acute fenitrothion poisonings of two species of rat and rabbit. By single treatment with 2-PAM carried out immediately after fenitrothion administration, the significant reactivations of inactivated AChE in red blood cell (RBC) and brain as well as inactivated cholinesterase (ChE) in plasma were observed at 2 h after administration of 20 mg/kg fenitrothion in rat, while these reactivations became less in rats severely poisoned with 500 mg/kg fenitrothion. Although these significant reactivations disappeared 6 h after the single treatment with 2-PAM, the repeated treatments with 2-PAM induced the prolongation of the reactivations of inactivated AChEs and ChE. These results suggest that 2-PAM would be more effective to light poisoning with fenitrothion, and that the repetition of 2-PAM treatment would be very important to obtain the sufficient antidotal actions. In rabbits as well as rats, the considerable reactivations of inactivated AChEs in RBC and brain and inactivated ChE in plasma were observed by the single treatment with 2-PAM in fenitrothion poisoning. These reactivations in brain AChE indicate that 2-PAM can penetrate the blood brain barrier of both rat and rabbit, despite its quaternary character.

Acetylcholinesterase↗
PubMed1984

Spontaneous reactivation of mouse plasma cholinesterase after inhibition by various organophosphorus compounds.

We investigated the spontaneous reactivation of mouse plasma cholinesterase (ChE) after inhibition by various organophosphorus compounds. The remarkable spontaneous reactivations during storage at 24 degrees C were observed in plasma ChE prepared 30 min after oral administration of three O,O-dimethyl organophosphorus compounds, i.e. malathion, methylparathion and cyanox; while the spontaneous reactivation did not occur after inhibition by tolclofos-methyl, one of O,O-dimethyl organophosphorus compounds. The plasma ChEs inhibited by surecide, salithion and leptophos, which contain no O,O-dimethyl moiety, were not reactivated or only slightly so. These results suggest that a more sufficient attention should be paid in the determination of activity of plasma ChE inhibited by O,O-dimethyl organophosphorus compounds than that of plasma ChE inhibited by organophosphorus compounds without O,O-dimethyl moiety, since plasma ChE inhibited by the organophosphorus compounds with O,O-dimethyl moiety, except for tolclofos-methyl, was more easily reactivated, and the correct activity of inhibited plasma ChE can not be obtained without attention to the spontaneous reactivation. Furthermore, these spontaneous reactivations were examined by using butyrylthiocholine as well as acetylthiocholine as a substrate, and results showed that there was little difference between the spontaneous reactivations observed in using acetylthiocholine and butyrylthiocholine. So, it is concluded that these spontaneous reactivations take place only in pseudo ChE.

Animals↗
PubMed1984

Effect of hypothermia and ether anesthesia on the dispositions of creatinine and urea in mice.

Hypothermal mice were used under the anesthetized condition with ether to clarify the effect of diminished blood circulation on the dispositions of creatinine and urea which are considered to pass through the water-filled pores of biological membranes easily. The total body clearance of each chemical was considerably decreased in hypothermal mice compared with normal mice. This was considered to be caused by the decrease of glomerular filtration rate. The whole-body autoradiograms obtained following intravenous administration of 14C-urea and the rate of muscular blood flow showed that the transfer of urea from blood to muscle was apparently delayed by the decrease of muscular blood flow rate. However, the transfer of creatinine to muscle was not influenced by the change of muscular blood flow rate. This difference between creatinine and urea might be related to the higher permeability of muscular cell membrane to urea than to creatinine.

Anesthesia↗
PubMed1984

Disposition of salicylic acid in analbuminemic rats.

To clarify the role of albumin in the dispositions of drugs by in vivo experiment, analbuminemic rats were used and plasma-level analyses and whole-body autoradiography following intravenous administration of 14C-salicylic acid were carried out. The distribution volume of salicylic acid in analbuminemic rats (650 +/- 33 ml/kg) was remarkably larger than that in normal rats (180 +/- 3 ml/kg) (p less than 0.01). Whole-body autoradiograms demonstrated that transfer of salicylic acid from the blood to the liver, muscle and brain, especially to the liver, may be increased in analbuminemic rats. The increased distribution may be explained by the lack of plasma albumin, since the distribution of salicylic acid depends in part on plasma albumin binding. The total body clearance of salicylic acid in analbuminemic rats (12.2 +/- 1.4 ml/min/kg) was about 3.2 times that in normal rats (3.8 +/- 0.1 ml/min/kg) (p less than 0.01), suggesting that metabolic clearance and/or renal clearance is enhanced in analbuminemic rats. Increased extraction by the liver and/or the kidney due to increased free fraction in total (bound and unbound) plasma salicylic acid assumed to be responsible for this result.

Animals↗