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Biomedical subjects

K Kamata

Publications and source records attributed to K Kamata.

At least 127 records · Page 7Linked to original sources
PubMed1995

Renal dysfunction in multiple myeloma.

This study aims to determine the clinical factors that may affect renal function and patient survival in 82 multiple myeloma patients. The patients were divided into 3 groups according to their renal function during the initial 8 weeks after diagnosis: Group I, 54 patients with serum creatinine (S-Cr) < 177 mumol/L; Group II, 11 with S-Cr > or = 177 mumol/L and receiving no dialysis; Group III, 17 undergoing dialysis treatment. Clinical status at diagnosis, subsequent renal function and patient survival were compared. Bence Jones proteinuria (BJP) was found in all patients in Groups II and III, compared to 67% of patients in Group I (p < 0.05, I vs II or III). Hypercalcemia, hyperuricemia and intravenous administration of contrast medium, together with BJP each constituted independent risk factors of renal dysfunction. The incidence of hypercalcemia in Group II was significantly higher than in the other 2 groups. Patient survival was 26.8 +/- 23.7 months in Group I, 8.1 +/- 10.3 in II and 12.1 +/- 16.6 in III (p < 0.05, I vs II or III). Renal function and patient survival depended on the initial renal function. Renal function was likely compromised in the presence of BJP.

Female↗
PubMed1995

Enterogenous cyst in the fourth ventricle--case report.

A 53-year-old male presented with a rare enterogenous cyst in the fourth ventricle associated with repeated ventriculoperitoneal shunt malfunction. Surgical excision of the cyst resolved the shunt problems. Electron microscopy findings of the surgical sample were microvilli covered with electron-dense coating materials, basement membrane, and several intercellular junctional devices, suggesting the cyst was derived from the endodermal structure. The viscous and gelatinous contents of the cyst might be responsible for the shunt malfunction.

Cerebral Ventricles↗
PubMed1995

Ocular absorption, distribution, and systemic absorption of a novel antiglaucoma medication, prostaglandin derivative, in male white rabbits.

A prostaglandin derivative, (5Z,9 alpha,11 alpha,13E)-9,11-dihydroxyprosta- 5,13-dienoic acid sodium salt (S-1033), that lowers intraocular pressure with little adverse effect, may have clinical value in the treatment of glaucoma. After [14C]S-1033 (0.2% solution) was instilled into the eye of a white rabbit, radioactivity and S-1033 appeared in systemic plasma so rapidly (tmax, 5 min) and S-1033 was eliminated very rapidly with half-lives of 2.8 and 11.0 min at alpha- and beta-phases, respectively. The metabolite, M-1, [1R-[1 alpha,2 beta-(1E),3 alpha,5 alpha]]-3,5-dihydroxy-2-(1- octenyl)-cyclopentanepropanoic acid (tetranor-S-1033), appeared in plasma very rapidly (tmax, 5 min), suggesting that a fast metabolism was a major factor in the rapid elimination of S-1033 from plasma. The values for the ratios of the area under the curve of ocular instillation to intravenous administration for radioactivity and S-1033 were 1.01 and 0.52, respectively, indicating that more than half of the S-1033 instilled was transported into the systemic circulation. To clarify the contributing pathway of the massive and rapid systemic absorption of S-1033 after topical dosing, plasma levels of S-1033 were investigated after instillation to rabbits in which the nasolacrimal ducts were occluded. Plasma concentrations of S-1033 were slightly higher than those in intact rabbits, suggesting that conjunctiva would be as important as nasal mucosae for the systemic absorption under the physiological condition. As for the intraocular distribution, the highest levels of radioactivity were found in the cornea, conjunctiva, and anterior sclera.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1995

[Corneal sensitivity after cataract operation by corneal incision or scleral incision].

We studied postoperative corneal sensitivity after cataract operation by scleral incision (30 eyes) or corneal incision (29 eyes). Corneal sensitivity was evaluated at 5 points of the cornea with a Cochet & Bonnet esthesiometer at 3 and 6 months after operation. Total value of corneal sensitivity decreased by 60 +/- 5.0 mg/S (mean +/- deviation) 3 months after corneal incision and by 46 +/- 4.1 mg/S after scleral incision. At 6 months after operation, the total value of corneal sensitivity was deceased by 14.0 +/- 2. 5 mg/S in corneal incision cases and by 7.9 +/- 2.0 mg/S in scleral incision cases. Corneal sensitivity after operation was decreased more by corneal incision than by scleral incision.

Aged↗
PubMed1995

Decreased Ca2+ influx into the endothelium contributes to the decrease in endothelium-dependent relaxation in the aorta of streptozotocin-induced diabetic mice.

Experiments were designed to investigate the role of Ca2+ influx into the endothelium in the relaxation of mouse aorta caused by acetylcholine (ACh) in streptozotocin (STZ)-induced diabetic and age-matched control mice. When Ca2+ was added to the bath, Ca2+ caused a transient contraction followed by relaxation in Ca(2+)-free medium containing 2 x 10(-6) M prostaglandin F2 alpha (PGF2 alpha) and 10(-5) M ACh in the control experiments. On the other hand, Ca2+ showed a long lasting contraction in STZ-induced diabetic rats. These results suggest that influx of Ca2+ into the endothelium is significantly attenuated in the diabetic vessels, and production or release of relaxing factor is markedly decreased.

Acetylcholine↗
PubMed1995

Relationship between contractile responses and cytosolic free calcium levels in response to phorbol ester (PMA) in isolated rat aorta.

We examined the relationship between phorbol ester (PMA)-induced contractile response and cytosolic free calcium level in the rat aorta. PMA (10(-6)M) produced biphasic contraction, i.e., sustained contraction followed by a phasic response superimposed on the sustained contraction. Increase in [Ca2+]i was accompanied by a phasic but not sustained contraction. These results suggest that PMA-induced phasic contraction is dependent on Ca2+ influx but sustained contraction may be due to an increase in Ca2+ sensitivity of contractile protein.

Animals↗
PubMed1995

Effects of VA-045, a novel apovincaminic acid derivative, on rabbit basilar artery.

We investigated the effects of VA-045, an apovincaminic acid derivative, on isolated basilar artery of the rabbit. In basilar artery precontracted with histamine (10(-6) M), VA-045 (10(-9) to 10(-5) M) produced a concentration-dependent relaxation, but VA-045-induced relaxation was significantly reduced when the tonus of the mesentery was raised by isotonic high K+ (30 or 65 mM) or histamine (10(-6) M) with 15 mM K+. VA-045-induced relaxations of the basilar artery were not affected by 10 mM tetraethylammonium (TEA), 10(-6) M 4-aminopyridine, 10(-6) M charybdotoxin, 10(-7) M apamin and 10(-6) M glybenclamide. VA-045-induced relaxation was not influenced by 10(-5) M methylene blue. These results suggest that increased open probability of potassium channels, which are not Ca(2+)-dependent K(+)-channels or TEA- or ATP-sensitive K(+)-channels, may be involved in VA-045-induced relaxation of basilar artery.

Animals↗
PubMed1994

Tooth pulp stimulation induces c-fos expression in the lateral habenular nucleus of the cat.

Detection of Fos protein expression by the peroxidase-antiperoxidase method was used to determine the area in the habenular (Hb) complex responding to electrical stimulation of the tooth pulp in the cat anaesthetized with pentobarbital. In the anaesthetic-injected group, the Fos-positive neurones were found bilaterally in the lateral Hb nucleus (HbL). Tooth pulp stimulation (intensity: 3 times the threshold for jaw-opening reflex) increased the number of positive neurones within the HbL by up to 300%, but did not induce any expression in the medical Hb nucleus. The increase in HbL was inhibited by morphine (2 mg kg-1, i.p.). These findings and the results of previous research suggest that HbL neurones are involved in defensive mechanisms by means of antinociception following noxious stimulation.

Animals↗
PubMed1994

Decrease in vasodilator effects of platelet-activating factor in resistance vessels of spontaneously hypertensive rats.

We studied the endothelium-dependent vasodilator effects of platelet-activating factor (PAF) on the mesenteric arterial bed of Wistar Kyoto rats (WKYs) and spontaneously hypertensive rats (SHRs) and found that vasodilation induced by PAF was significantly attenuated in SHRs. We discovered no significant differences in reactivity or sensitivity of the mesentery to acetylcholine between WKYs and SHRs. Our results strongly suggest that the attenuated vasodilator effects of PAF on the SHR mesenteric arterial bed may be due in part to desensitization rather than impairment of the endothelium.

Animals↗
PubMed1994

Liquid chromatographic determination of carnitine by precolumn derivatization with pyrene-1-carbonyl cyanide.

A method is described for the determination of carnitine chloride in pharmaceutical preparations by precolumn derivatization and high-performance liquid chromatography (HPLC). Carnitine chloride is derivatized by reaction with pyrene-1-carbonyl cyanide (PCC) in dimethyl sulphoxide. The PCC derivative of carnitine is then used for quantitative HPLC analysis on a cation-exchange column with fluorescence detection. The calibration graph was linear over a sample concentration range from 2.0 to 20 micrograms/ml; the limit of detection was 0.5 microgram/ml under the conditions studied. The proposed method was applied satisfactorily to the determination of carnitine chloride in pharmaceutical preparations.

Carnitine↗
PubMed1994

Hypotensive effects of lithospermic acid B isolated from the extract of Salviae miltiorrhizae Radix in the rat.

1. The in vivo and in vitro effects of lithospermic acid B (LSA-B), which was extracted from Salviae miltiorrhizae Radix, on vascular relaxation responses were examined in rats. 2. Intravenous injection of LSA-B (10-30 mg/kg) decreased the blood pressure in a dose-dependent manner. 3. In perfused mesenteric arterial bed precontracted with methoxamine (10(-5) M), LSA-B (10(-5) - 10(-3) M) produced a concentration-dependent relaxation. 4. Vasodilator response of the mesentery in response to LSA-B was reversed by 10(-4) M NG-monomethyl-L-arginine (L-NMMA). 5. The inhibition of vasodilation by L-NMMA was reversed by L-arginine (3 x 10(-4) M). 6. These results suggest that LSA-B-induced hypotensive effect may be due to the endothelium-dependent vasodilation of resistance artery such as mesenteric arterial bed.

Anesthesia↗
PubMed1994

T and R states in the crystals of bacterial L-lactate dehydrogenase reveal the mechanism for allosteric control.

The crystal structure of L-lactate dehydrogenase from Bifidobacterium longum, determined to 2.5 A resolution, contains a regular 1:1 complex of T- and R-state tetramers. A comparison of these two structures within the same crystal lattice and kinetical characterization of the T-R transition in solution provide an explanation for the molecular mechanism of allosteric activation. Substrate affinity is controlled by helix sliding between subunits which is triggered by the binding of the activator, fructose 1,6-bisphosphate. The proposed mechanism can explain activation by chemical modification and mutagenesis, as well as suggesting why vertebrate counterparts are not allosteric.

Allosteric Regulation↗
PubMed1994

Vasodilator effects of clonidine on the mesenteric arterial beds in normotensive and spontaneously hypertensive rats.

Clonidine, an alpha 2-agonist, caused a concentration-dependent vasodilation of the mesenteric arterial beds in both normotensive and hypertensive rats. The clonidine-induced vasodilation was inhibited by NG-nitro-L-arginine, and the inhibition was reversed by L-arginine. The concentration-dependent vasodilation was not significantly different between normotensive and hypertensive rats. These results suggest that clonidine has an endothelium-dependent vasorelaxant action in the resistance artery such as rat mesenteric arterial bed, and the endothelium-dependent vasodilator effects of clonidine in the mesentery may be involved in the depressor effect of the drug.

Animals↗
PubMed1994

[Comparative study of type of prosthesis on late results after double valve replacement].

This study was performed to clear the influence of combination of prostheses on late results by comparing our patients. The patients were divided into two groups. Group I patients received a mechanical valve in the aortic position and a bioprosthesis in the mitral position (n = 25): and group II, dual mechanical valves (n = 89). The duration of follow-up ranged from 0.2 to 13.5 years, with a total of 466 patient-years. There was no difference between the two groups in terms of actuarial survival or incidence of reoperations, thromboemboli, or nonstructural dysfunction. Group I, however, had a significantly greater incidence of structural valve deterioration, anticoagulant-related hemorrhage, and all valve-related morbidity and mortality when compared with group II. In conclusion, 1. combining a mechanical valve and a bioprosthesis is disadvantageous: 2. dual mechanical valves have excellent long-term results.

Aortic Valve↗