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Biomedical subjects

E Sakurai

Publications and source records attributed to E Sakurai.

At least 109 records · Page 6Linked to original sources
PubMed1992

Effects of the histamine H3 receptor ligands thioperamide and (R)-alpha-methylhistamine on histidine decarboxylase activity of mouse brain.

The effects of the histamine H3 receptor ligands thioperamide and (R)-alpha-methylhistamine on the histidine decarboxylase (HDC) activity and histamine content of mouse brain were examined. Thioperamide, a histamine H3 antagonist, significantly increased the HDC activity in the brain of ddY, W/Wv and ICR mice 2-6 hr after its intraperitoneal (i.p.) injection. On the other hand, (R)-alpha-methylhistamine, a histamine H3-receptor agonist, caused no significant change in the HDC activity. The whole brain histamine content of ddY mice decreased significantly to 60-70% of the control level 2-8 hr after injection of thioperamide (25 mg/kg, i.p.), but then increased to 90% of the control level 10 hr after the injection. These in vivo results showed that blockade of the presynaptic histamine H3-receptor, which causes release of presynaptic histamine, increased the HDC activity.

Animals↗
PubMed1992

Enantioselective pharmacokinetics of alpha-fluoromethylhistidine in rats and its comparison with histidine.

The enantiomer-specific pharmacokinetics of histidine and its analogue, alpha-fluoromethylhistidine (FMH), were investigated in rats. After bolus intravenous administration of each enantiomer of histidine or FMH at a dose of 40.3 mg kg-1 as free base equivalents, the plasma concentrations of L-histidine, D-histidine, (S)-FMH and (R)-FMH decreased biexponentially with half-lives of 39.2, 20.8, 32.8 and 25.0 min, respectively, in the elimination phase. Although the concentration of L-histidine in the plasma was lower than that of D-histidine, there was no large difference in plasma concentration-time curves of the enantiomers of FMH. The apparent total clearance of L-histidine from rat plasma was about 4 times that of D-histidine or the enantiomers of FMH. L-Histidine was quickly transferred to the peripheral tissues where the concentrations also decrease biphasically. L-Histidine penetrated more rapidly into the brain than either its D-enantiomer or a compound closely related in structure such as FMH. However, the disappearance of L-histidine from the various brain regions was very rapid. In contrast, brain/plasma ratios of D-histidine and (S)-FMH increased continuously after injection of these compounds, indicating that D-histidine or (S)-FMH partitioned into the brain and was very slowly removed from the brain; (R)-FMH was not distributed to the brain. These results suggested stereoselectivity in disposition of histidine and FMH enantiomers in rats.

Animals↗
PubMed1992

The optical resolution of racemic chlorpheniramine and its stereoselective pharmacokinetics in rat plasma.

An ovomucoid-conjugated column has been developed for the chiral stationary-phase liquid chromatographic resolution of racemic chlorpheniramine with a quantitation limit of 0.05 microgram mL-1. The assay was used to study the stereoselective kinetics of chlorpheniramine enantiomers in rats. After bolus intravenous administration of racemic chlorpheniramine maleate (20 mg kg-1), plasma concentration of the (-)-form was higher than that of the (+)-form. In the elimination phase, the concentrations of (+)- and (-)-chlorpheniramine in the plasma declined biexponentially with half-lives of 18.2 and 50.0 min, respectively. Although there was no significant difference in blood-to-plasma concentration ratio of both enantiomers, the apparent total blood clearance of (+)-chlorpheniramine was twice as large as that of the (-)-isomer. Binding of (-)-chlorpheniramine to rat plasma protein was stronger than that of (+)-chlorpheniramine suggesting stereoselective pharmacokinetics may be due to a difference in the plasma protein binding.

Animals↗
PubMed1992

[Effects of selenium on the serum glucose and insulin levels in diabetic rats].

We investigated the effects of selenium (Se) on the serum glucose and insulin levels in rats with diabetes induced by streptozotocin (STZ, 75 mg/kg, i.p.) and pancreatectomized rats. Moreover, the direct action of Se on insulin release from the isolated pancreatic islets using a slight diabetic rat was studied. The following results were obtained: 1) Selenite at a dose of 173 micrograms/kg (78.9 micrograms/kg of Se base equivalent) drastically reduced the very high level of serum glucose in acute diabetic rats within 5 to 30 min after treatment. During this time period, the insulin level in the serum showed an increasing tendency. 2) The high serum glucose level in chronic diabetic rats returned to the original level with injection of selenite for 4 days, once a day. However, Se did not elicit a significant increase in serum insulin level. 3) Although there was a tendency for the serum glucose level to decrease when selenite was administered into pancreatectomized rats, no secretion of insulin into the serum was observed. 4) Insulin release from isolated pancreatic islets was dose-dependently accelerated by the addition of selenite. These data present the new finding that Se reduced the high level of serum glucose in diabetic rats.

Animals↗
PubMed1992

Effects of inhibitors of protein kinase C on the release and synthesis of histamine in rat basophilic leukemia cells (2H3).

In rat basophilic leukemia cells (2H3), a tumor analog of mast cells, the aggregation of IgE receptors results in histamine secretion and the increase in histidine decarboxylase activity which synthesizes histamine. Using inhibitors of protein kinases C, we studied the relationships between these events and protein kinase C which is activated by antigens. Histamine release is suppressed by inhibitors of protein kinase C, staurosporine, K252-a and H-7, in this decreasing order of effectiveness; and the IC50 values are 1.5 nM, 29.9 nM and 3.8 microM, respectively. The changes in the intracellular Ca concentration monitored by fura-2 fluorescence is not modified by staurosporine, although the histamine response is suppressed. Meanwhile, the increase of histidine decarboxylase was abolished by inhibitors of protein kinase C; staurosporine was the strongest, K-252a of moderate activity and H-7, the weakest, having IC50 values of 0.8 nM, 100 nM and 11.5 microM, respectively. The inhibitors of protein kinase C suppress both histamine secretion and synthesis. Therefore, the histamine synthesis may be stimulated via activation of protein kinase C to supplement the released histamine.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Calcium signal and histamine secretion induced by aggregation of immunoglobulin E receptors in rat basophilic leukemia (RBL-2H3) cells.

The changes in cytosolic Ca concentration in rat basophilic leukemia cells (RBL-2H3) were determined using a fluorescent Ca probe, fura-2, after aggregation of IgE receptors. By means of a superfusion system, both histamine secretion and changes in cytosolic Ca concentration were determined simultaneously. In addition, the microscopic observation revealed the oscillatory Ca signal after stimulation with an antigen.

Animals↗
PubMed1991

Role of altered prednisolone-specific lymphocyte sensitivity in chronic renal failure as a pharmacodynamic marker of acute allograft rejection after kidney transplantation.

The effects of four immunosuppressive agents on the in vitro blastogenesis of peripheral blood lymphocytes activated by concanavalin A have been studied using cells from 26 healthy subjects, 34 patients with chronic renal failure (CRF) and 30 kidney transplant recipients. Differences in lymphocyte sensitivity to prednisolone between the healthy subjects and the CRF patients were statistically significant (P less than 0.0002), with impaired sensitivity in CRF. Impaired lymphocyte sensitivity occurred in 3.8% and 52.9% of the healthy and CRF subjects, respectively. Lymphocyte sensitivity to prednisolone, both preoperatively and 3 months post-operatively, was strongly correlated with early allograft rejection during co-administration of prednisolone with cyclosporin or azathioprine. Lymphocyte sensitivity to cyclosporin, azathioprine, and mizoribine in CRF was not significantly less than that in healthy subjects. Since the pharmacokinetics of prednisolone are little altered in renal transplantation, it is concluded that lymphocyte sensitivity specific to prednisolone may be a pharmacodynamic marker characteristic of successful graft survival in patients with histo-incompatibility and/or drug resistance.

Adult↗
PubMed1991

Impaired prednisolone sensitivities of the endocrine system and peripheral-blood lymphocytes are closely related to clinical incidence in renal transplantation.

Endocrine- and immune-responses to prednisolone and their relation to clinical incidence were assessed in 19 renal transplant recipients. All of the patients were treated with prednisolone and cyclosporin. Response of the hypothalamic-pituitary-adrenal (HPA) system to prednisolone was evaluated by measuring serum cortisol concentration. Cortisol concentration before transplantation was 126.7 +/- 38.6 ng mL-1, while it decreased to 4.1 +/- 2.5 ng mL-1 within the period characterized by a cumulative dose of prednisolone from 300 to 700 mg. A statistically significant high incidence (P less than 0.01) of acute rejections was observed in low HPA responders; (mean cortisol concentration during prednisolone treatment exceeded 3.0 ng mL-1), 6 of 12 with a low HPA response to prednisolone showed signs of rejection, while none of the 7 with a high HPA response showed signs of rejection. The concentrations of prednisolone suppressing the in-vitro response of pretransplant lymphocytes to concanavalin A by 50% (ID50) were determined. Lymphocytes from 8 patients were extremely insensitive (ID50 greater than 500 ng mL-1), and 5 of the 8 showed signs of rejection. Lymphocytes from the other 11 patients showed high sensitivity (ID50 less than 500 ng mL-1), and only one of those showed signs of rejection. Thus, a significantly high incidence of rejection was observed in low lymphocyte-responders to prednisolone (P less than 0.05). The results suggest that an insensitive endocrine response to prednisolone correlates with an impaired lymphocyte response to the steroid, and that both of the indices are related to occurrence of rejection. Evaluation of these pharmacodynamic parameters in combination may serve as a guideline for successful immunosuppressive therapy in renal transplantation.

Adult↗
PubMed1991

Recovery of decreased ability of peripheral-blood mononuclear cells from chronic renal failure to produce interleukin-1 alpha and beta after renal transplantation.

The ability of cultured peripheral-blood mononuclear cells (PBMC) to release interleukin-1 alpha and beta (IL-1 alpha, IL-1 beta) in response to concanavalin A (con A) was investigated in patients with chronic renal failure (CRF) and in renal transplant recipients. Mean IL-1 alpha level released by PBMC of healthy subjects (n = 42), CRF patients (n = 42), or transplants 2 months after operation (n = 69) was 152 +/- 103, 110 +/- 80, or 154 +/- 87 pg/5 x 10(5) cells/ml culture, respectively. IL-1 alpha release from PBMC of recipients 2 months after renal transplantation was significantly higher than that of CRF patients (p less than 0.05). Mean IL-1 beta level released by PBMC of healthy subjects (n = 34), CRF (n = 30), or transplants (n = 55) was 223 +/- 159, 135 +/- 129, or 276 +/- 155 pg/5 x 10(5) cells, respectively. Similar to IL-1 alpha, the level in CRF was significantly lower than that in healthy subjects (p less than 0.05). A time course study indicated that the ability of PBMC from transplants to release IL-1 alpha and beta promptly decreased following the operation, possibly owing to prednisolone and ciclosporin immunosuppressive therapy. However, after maintaining a low level for 2-3 weeks, IL-1 release from PBMC gradually increased thereafter. The results were consistent with known characteristics of decreased immunity in CRF states, and further suggested that the decreased ability of PBMC to release IL-1 alpha and beta in response to con A in CRF patients is recovered 2 months after renal transplantation.

Adult↗
PubMed1991

Effects of d-, l- and dl-chlorpheniramine on dopamine and 3,4-dihydroxyphenylacetic acid levels in the regional parts of rat brain.

The purpose of this study was to further investigate the differences in the effects of optical isomers of chlorpheniramine (d-, l- and dl-forms) on the levels of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the regional parts of rat brain. After the intravenous administration of each form of chlorpheniramine at a dose of 20 mg/kg, the DA and DOPAC levels were measured by HPLC system. Each form of chlorpheniramine is effective in reducing DOPAC, but not DA levels in the brain of rats. The degree of reducing DOPAC levels does not correlate with the antihistaminic potency of these drugs. Thus, the present results indicate that there is a lack of stereospecificity in reducing DOPAC levels, suggesting the lack of stereospecificity in inhibiting DA reuptake.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Effects of d- and dl-chlorpheniramine on serotonin and 5-hydroxyindoleacetic acid levels in the regional parts of rat brain.

The purpose of this study was to further investigate the effects of chlorpheniramine (d- and dl-forms) on the levels of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in the regional parts of rat brain. After the intravenous administration of each form of chlorpheniramine, the 5-HT and 5-HIAA levels were measured by HPLC system. Each form of chlorpheniramine is effective in reducing 5-HIAA, but not 5-HT levels in most of the regional brain of rats. The degree of reducing 5-HIAA levels does not correlate with the antihistaminic potency of these drugs. Our previous results showed that chlorpheniramine reduced the 3,4-dihydroxyphenylacetic acid levels, but not the dopamine levels in the brain of rats. Taken together, these findings raise problems regarding possible physiological and behavioral effects by using chlorpheniramine as a histamine H1-blocker in animal experiments.

Animals↗
PubMed1990

Blood platelet monoamine oxidase activity, serotonin uptake and release rates in anorexia and bulimia patients and in healthy controls.

Platelet monoamine oxidase (MAO) activity, serotonin uptake rate and serotonin efflux rate have all been suggested to be markers for central serotonergic mechanisms. Platelet MAO activity is associated with certain personality traits, with low activity linked to traits such as impulsiveness, sensation-seeking and avoidance of monotony, all possible expressions of low central serotonergic activity. Low platelet serotonin uptake rate has been connected to unipolar depression and the rate of efflux, in the presence of the ATP uncoupler CCP, higher in bipolar depressives than in controls. Platelet MAO was found to be lower in 16 consecutive female inpatients fulfilling the DSM-III criteria for bulimia nervosa than in 12 female controls. Rates of serotonin uptake and efflux in the presence of CCP were, on the other hand, similar to the controls. In the controls there were no correlations between platelet MAO activity and any of the other parameters estimated. Vmax for the platelet uptake of serotonin correlated positively with the Km for the uptake, but not with any other parameter. The uninfluenced rate of efflux of serotonin correlated positively with the efflux in the presence of the ATP uncoupler CCP.

Adolescent↗
PubMed1990

The disposition of a histidine decarboxylase inhibitor (S)-alpha-fluoromethylhistidine in rats.

An amino acid analyser method using ninhydrin was developed for (S)-alpha-fluoromethylhistidine (FMH) with a minimum quantitation limit of 0.2 microgram mL-1. The assay was used to study the kinetics of FMH in rat. After bolus intravenous administration of FMH hydrochloride hemihydrate (50 mg kg-1), plasma concentration decreased biexponentially with half-lives of 4.4 and 32.7 min. The distribution volumes of the central and peripheral compartments were 127.4 and 166.3 mL kg-1, respectively. The tissue concentration of FMH was highest in the kidney and also decreased biphasically. The FMH concentrations in other tissues were lower, but their tissue/plasma ratios of FMH increased continuously after FMH injection, indicating that FMH partitioned into these tissues and was lost from them very slowly.

Animals↗