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Biomedical subjects

H Aoshima

Publications and source records attributed to H Aoshima.

At least 37 records · Page 2Linked to original sources
PubMed1997

Modulation of GABA receptors expressed in Xenopus oocytes by 13-L-hydroxylinoleic acid and food additives.

To study the effects of 13-L-hydroxylinoleic acid (LOH) and food additives on gamma-aminobutyric acid (GABA) receptors, ionotropic GABA receptors were expressed in Xenopus oocytes by injecting mRNAs prepared from rat whole brain. LOH, which was prepared by reduction of 13-L-hydroperoxylinoleic acid (LOOH), inhibited the response of GABA receptors in the presence of high concentrations of GABA. LOH also inhibited nicotinic acetylcholine, glycine, and kainate receptors, while it had little effect on NMDA receptors expressed in Xenopus oocytes. However, LOH potentiated the response of GABA receptors as well as LOOH in the presence of low concentrations of GABA, possibly increasing the affinity of GABA for the receptors, while linoleic acid did not. Since some modification of the compounds seemed to change their effects on GABA receptors, the responses of GABA receptors elicited by 10 microM GABA were measured in the presence of compounds with various kinds of functional groups or the structural isomers of pentanol. Potentiation of GABA receptors depended strongly on the species of functional groups and also depended on the structure of the isomers. Then effects of various kinds of food additives on GABA receptors were also examined; perfumes such as alcohols or esters potentiated the responses strongly, while hexylamine, nicotinamide, or caffeine inhibited the responses, mainly in a competitive manner, and vanillin inhibited the responses noncompetitively. These results suggest the possibility that production of LOOH and LOH, or intake of much of some food additives, modulates the neural transmission in the brain, especially through ionotropic GABA receptors and changes the frame of the human mind, as alcohol or tobacco does.

Animals↗
PubMed1997

The sugar specificity of Na+/glucose cotransporter from rat jejunum.

A cDNA for a Na+/glucose cotransporter was cloned from rat jejunum cDNA library. This transporter was expressed in Xenopus oocytes by injection of cRNA synthesized from the cDNA, and the transporter ability was electrophysiologically examined. The cotransporter had a very narrow sugar specificity. Only D-glucose, D-galactose, and some of their derivatives elicited significant electrical responses. These results of sugar specificity were compared with those of the H+/hexose cotransporter of Chlorella. Dose-response relationships of several sugars followed a simple Michaelis-Menten type of kinetics. Both Vm and Km were dependent on the sugars. Not only the affinity of sugars to the cotransporter but also the rate of conformational change of the cotransporter loaded with the sugar and Na+, which translocates them from outside to inside, possibly depends on the sugar structure. The rate-limiting step of the transportation may be the conformational change, i.e., isomerization, of the cotransporter that translocates both the sugar and Na+ from outside to inside.

Animals↗
PubMed1997

Functional versus aesthetic articulation of maxillary anterior restorations.

The correct orientation of the master model is a frequently overlooked aspect of communication between the clinician and the ceramist. The master model must provide the ceramist with the same perspective of the patient as is seen by the clinician--facing the viewer. Unless precise information is transferred to the laboratory, the ceramist can only estimate horizontal and vertical alignment of the working cast from landmarks taken from the cast itself. It is unwise to leave such appraisal to chance, especially when restoring multiple anterior preparations, where the potential for misalignment of the cast increases with the number of restorations involved. The learning objective of this article is to discuss communication techniques between the clinician and the ceramist for achieving precise and predictable orientation in the treatment of aesthetic anterior restorations.

Communication↗
PubMed1997

Aesthetic all-ceramic restorations: the internal live stain technique.

The utilization of porcelain as a restorative material began a new era in aesthetic dentistry. By today's standards, the early porcelains were rather primitive and of low value. However, the potential of all-ceramic material for aesthetic dentistry was recognized, and various modifications and enhancements followed to render the material applicable for dental restorations. The learning objective of this article is to present the history of development, the principles, and the laboratory fabrication of ceramic restorations utilizing the Internal Live Stain Technique. The technique uses stains with all-ceramic material to achieve the optimal simulation of natural dentition. While replicating the optical properties inherent in the natural dentition, the application of the stain improves the physical characteristics of the all-ceramic material. The general principles of the first and second applications are disclosed, followed by presentation of two clinical cases--all-ceramic crown and laminate veneer restorations in the maxillary anterior segment.

Adult↗
PubMed1996

Potentiation and inhibition of ionotropic neurotransmitter receptors expressed in Xenopus oocyte by linoleic acid and its hydroperoxide.

To study the effects of lipid hydroperoxide on ionotropic neurotransmitter receptors, gamma-aminobutyric acid (GABA), N-methyl-D-aspartate (NMDA), and non-NMDA receptors (GABARs, NMDARs, and non-NMDARs, respectively) were expressed in Xenopus oocytes that received an injection of mRNA prepared from rat whole brain. Linoleic acid (LA) and its hydroperoxide 13-L-hydroperoxylinoleic acid (LOOH) prepared with soybean lipoxygenase inhibited the response of GABARs in the presence of GABA at high concentrations. The inhibition was stronger when the inhibitors were perfused 1 min before a mixture of GABA and the inhibitors than when they were perfused simultaneously with GABA. On the other hand, only LOOH potentiated the response of GABARs in the presence of GABA at low concentrations, possibly increasing the affinity of GABA to the receptors. Both LA and LOOH accelerated the rate of desensitization of GABARs, but LOOH did not affect their equilibrium between the active and desensitized form of the receptors. They also inhibited the response of NMDARs in a noncompetitive manner but barely inhibited the response of non-NMDARs in the presence of kainate at various concentrations. These results suggest the possibility that production of lipid hydroperoxide modulates the neural transmission in the brain, especially through GABARs.

Animals↗
PubMed1996

Effects of alcohols and food additives on glutamate receptors expressed in Xenopus oocytes: specificity in the inhibition of the receptors.

To study the effects of food additives on glutamate receptors, they were expressed in Xenopus oocytes that received an injection of poly(A)+ mRNAs prepared from rat brain. The response of the receptors elicited by kainate (KA) and N-methyl-D-aspartate (NMDA) was measured electrophysiologically in the presence and absence of food additives. Both responses elicited by KA and NMDA were inhibited similarly by addition of additives such as caffeine, vanillin or saccharin. However, inhibition of KA-elicited response by food additives followed a competitive inhibition scheme with two binding sites, while that of NMDA-elicited response followed a simple noncompetitive inhibition scheme. Inhibition constants of food additives for both responses were more than 1 mM. So it is unlikely that food additives taken with processed food interrupt signal transmission under physiological conditions. The specificity of inhibition of both responses was examined by adding various compounds to the bathing solutions containing the agonist. Increase of the number of hydroxyl groups in alcohols with the chain of three carbon atoms decreased the potency of inhibition. Potency of the inhibition depended on the species of functional groups. The order of potency of the inhibition by compounds with a chain of six carbon atoms was alcohol = diamine > aldehyde > carboxylic acid. Hexanol inhibited the receptors more strongly than (3Z)-hexen-1-ol. NMDA-elicited response showed little selectivity in inhibition by structural isomers of pentanol, while KA-elicited response showed some selectivity in inhibition by the structural isomers.

Alcohols↗
PubMed1995

[Fracture threshhold of rheumatoid arthritis patients].

The Bone mass measurement had been difficult while the fracture risk of the rheumatoid arthritic patient had been depended on osteoporosis. Recently, the accuracy of bone mass measurement became reliable that the adequate data could be obtained from the patients. This study shows the fracture threshold of rheumatoid patients by obtaining the bone mass density of those who had been suffering from fracture by DEXA. Twenty two limbs of 21 female patients were affected, average age of 65 and duration of 18 years, and the sites of fracture were femoral neck in 9 cases and humeral neck in 4 cases (62% of the fracture). The BMD of the spine in these patients shows. 828 g/cm2 which was below -3.4 sd of the normal japanese female and thought to be a fracture threshold in RA patients. The risk factors of the fractures in RA were ADL in the limbs, history of total joints arthroplasty and low body mass index.

Activities of Daily Living↗
PubMed1994

Phenylethanoid glycoside from Veronica undulata.

From a water extract of whole plants of Veronica undulata, a new phenylethanoid triglycoside and five known glycosides were isolated. The structure of the new compound was elucidated from chemical and spectroscopic evidence.

Carbohydrate Sequence↗
PubMed1994

Effects of aliphatic alcohols and food additives on nicotinic acetylcholine receptors in Xenopus oocytes.

To study the effects of food additives on nicotinic acetylcholine receptors (nAChR), they were expressed in Xenopus oocytes that received an injection of mRNA prepared from electroplax of Electrophorus electricus. The response of nAChR elicited by acetylcholine (ACh) was measured electrophysiologically in the presence and absence of aliphatic alcohols and food additives. All compounds examined inhibited nAChR non-competitively in a concentration-dependent way. The inhibition was stronger when the inhibitors were perfused 1 min before ACh, than when they were perfused simultaneously with ACh. The inhibition of nAChR by aliphatic alcohols (propanol to hexanol) increased as the number of carbon chains increased. The addition of alcohols and food additives did not affect the desensitization of nAChR caused by 2 microM ACh. These results suggest that alcohols and food additives bind to the anesthetic binding site in nAChR and inhibit it noncompetitively. However, these compounds will not hinder signal transmission in neuromuscular junctions under physiological conditions, because their inhibition constants are more than 1 mM and muscles usually have more receptors than the number necessary for signal transmission.

Animals↗
PubMed1993

The Maillard protein cross-link pentosidine in urine from diabetic patients.

The Maillard protein cross-link pentosidine is a fluorescent condensation product of lysine, arginine and ribose. It accumulates in human tissues with age, and the accumulation process is accelerated in the tissues of diabetic patients. Using SP-Sephadex C-25 in the pretreatment for HPLC, we examined levels of pentosidine in urine without hydrolysis (free form) and levels of pentosidine in urine after hydrolysis (total forms), from 23 diabetic patients and 21 control subjects. The mean percentages of the values of free form per total forms (+/- SD) were 89 +/- 15% in diabetic patients, 88 +/- 16% in control subjects and 89 +/- 15% in total populations of diabetic patients and control subjects. There was a significant correlation between the values of free form and total forms in diabetic patients (r = 0.983, p = 0.0001), in control subjects (r = 0.820, p < 0.02) and in total populations of diabetic patients and control subjects (r = 0.951, p = 0.0001). The mean level of pentosidine per mol creatinine (+/- SD) was significantly elevated in urine from diabetic patients as compared to the level in control subjects (8.8 +/- 4.3 mumol/mol creatinine vs 4.2 +/- 1.4 mumol/mol creatinine, p = 0.0001 in free form; 10.1 +/- 5.3 mumol/mol creatinine vs 4.7 +/- 1.4 mumol/mol creatinine, p = 0.0001 in total forms). These results demonstrate that urinary pentosidine, especially in free form, could be a useful marker for the assessment of diabetes and diabetic complications.

Aged↗
PubMed1993

Age-related changes of urinary pyridinoline and deoxypyridinoline in Japanese subjects.

Urinary pyridinoline (Pyr) and deoxypyridinoline (D-Pyr) are commonly used as bone resorption markers because they are more sensitive to bone resorption than is urinary hydroxyproline. Age-related changes of urinary Pyr and D-Pyr were studied in 337 healthy females, aged 1 to 93 y, and 113 healthy males, aged 3 to 75 y. Levels of urinary Pyr and D-Pyr follow a characteristic pattern as one ages, with very high values during childhood decreasing to low baseline levels in adulthood between 20 and 49 y. Both values in the 0-19 y age group were significantly higher than those in the other age groups for both sexes. These values increased moderately but significantly in females in the 50-59 y age group compared to those in the 40-49 y age group (Pyr: 26.4 +/- 7.6 vs. 19.3 +/- 6.2 nmol/mmol creatinine, p < 0.05; D-Pyr: 7.7 +/- 2.4 vs. 5.6 +/- 2.2 nmol/mmol creatinine, p < 0.05). In contrast, these values stayed at low levels in the 50-59 y age group in males. The values of urinary Pyr and D-Pyr were significantly higher in females than in males in the 50-59 y age group (females vs. males--Pyr: 26.4 +/- 7.6 vs. 17.0 +/- 3.9 nmol/mmol creatinine, p < 0.05; D-Pyr: 7.7 +/- 2.4 vs. 4.7 +/- 1.2 nmol/mmol creatinine, p < 0.05). In our cross-sectional study, the values of urinary Pyr and D-Pyr increased in childhood (0-19 y), and in the early postmenopausal period (50-59 y). These 2 urinary markers reflect the age-related changes of bone resorption.

Adolescent↗
PubMed1992

A minimal model to account for the response of N-Methyl-D-aspartate receptors expressed in Xenopus oocyte injected with rat brain mRNA.

N-Methyl-D-aspartate (NMDA) receptors were expressed in Xenopus oocytes by injecting rat brain mRNA. NMDA-elicited responses in the oocytes were measured by the voltage-clamping method. The following measurements were made in the presence of 50 microM glycine (Gly) to establish the relationship between the NMDA concentration and the current: (1) the NMDA-induced membrane current before desensitization; (2) the NMDA-induced membrane current after desensitization equilibrium; (3) the fraction of the active form of the receptor after desensitization equilibrium in the presence and absence of 50 microM Gly; (4) the rate of the recovery of desensitized receptors upon removal of NMDA. Gly was essential for not only the activation of NMDA receptors but also their desensitization. These results were analyzed on the basis of a minimal model where one agonist and one Gly binding site were assumed. The equilibrium and rate constants of the model were evaluated for NMDA in the presence of saturating amounts of Gly. This model will be useful for systematically explaining the complicated responses of NMDA receptors.

Animals↗
PubMed1992

Minimal model analyzing response of glycine receptors expressed in Xenopus oocyte: inhibition by a lipid hydroperoxide.

Glycine receptor (GlyR) was expressed in Xenopus oocytes by injecting rat brain mRNA. Glycine (Gly)-elicited responses in the oocyte were measured by the voltage-clamping method. The following measurements were made to establish the relationship between Gly concentration and the current: 1) Gly-induced membrane current before desensitization, 2) Gly-induced membrane current after desensitization equilibrium, 3) fraction of the active form of the receptor after desensitization equilibrium, 4) rate of recovery of the desensitized receptors upon removal of Gly. These results were analyzed on the basis of the minimal model proposed for nicotinic acetylcholine and gamma-aminobutyric acid A receptor. The equilibrium and rate constants of the model were evaluated for GlyR. The effects of procaine and 13-L-hydroperoxylinoleic acid (LOOH) on GlyR were examined electrophysiologically. LOOH noncompetitively inhibited the receptor with the inhibition constant of 27 microM, while 1 mM procaine, a local anesthetic, did not inhibit GlyR at all.

Animals↗
PubMed1992

Inhibition of ionotropic neurotransmitter receptors by antagonists: strategy to estimate the association and the dissociation rate constant of antagonists with very strong affinity to the receptors.

Since binding of an agonist to an ionotropic neurotransmitter receptor causes not only channel opening, but also desensitization of the receptor, inhibition of the receptor by the antagonist sometimes becomes very complicated. The transient state kinetics of ligand association and dissociation, and desensitization of the receptor were considered on the basis of the minimal model proposed by Hess' group, and the following possibilities were proposed. 1) When an agonist is simultaneously applied to the receptor with an antagonist whose affinity to the receptor is extremely strong and different from that of the agonist, it is usually impossible to estimate the real inhibition constant exactly from the responses because desensitization of the receptor proceeds before the equilibrium of the ligand binding. Simultaneous addition of the antagonist with strong affinity to the receptor may apparently accelerate inactivation (desensitization) of the receptor. The association rate constant of the antagonist can be estimated by analyses of the rate of the inactivation in the presence and the absence of the antagonist. 2) A preincubated antagonist with a slow dissociation rate constant, i.e., a very effective inhibitor, may cause apparent noncompetitive inhibition of the receptor, since the receptor is desensitized by an agonist as soon as the antagonist dissociates from the receptor and the dissociation of the antagonist from the receptor becomes the rate-determining step. A nicotinic acetylcholine receptor (nAChR) was expressed in Xenopus oocytes by injecting mRNA prepared from Electrophorus electricus electroplax and used for the experiments on inhibition by an antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1992

Effect of nebracetam on nicotinic and muscarinic acetylcholine receptors expressed in Xenopus oocyte by injecting exogenous mRNA.

Using voltage- and current-clamp methods the effects of nebracetam 4-aminomethyl-1-benzylpyrrolidine-2-one hemifumarate, WEB 1881 FU, CAS 118607-07-1), a new agent with nootropic property, on the nicotinic (nAChRs) and muscarinic acetylcholine receptors (mAChRs) were studied, which were expressed in Xenopus oocytes by injecting E. electricus mRNA and rat brain mRNA, respectively. Simultaneous application of nebracetam (0.03-2 mmol/l) with acetylcholine (ACh) (0.01-1 mmol/l) inhibited the ACh-responses of both nAChRs and mAChRs, whereas preapplication of these concentrations of nebracetam for 30 s to 1 min potentiated such inhibition. A simple competitive inhibition model for the effects of both drugs simultaneously applied yielded the inhibition constant, K1 of 0.419 and 0.212 mmol/l for nAChRs and mAChRs, respectively, indicating that the action on mAChRs is a little more potent than on nAChRs. Nebracetam induced a concentration-dependent slight increase in inward currents on mAChRs but not on nAChRs. It is suggested that the direct effects of nebracetam on nAChRs and mAChRS, which were induced only by a rather high concentration, as compared with the clinically expected plasma level, may be a contributing factor to the clinical effectiveness of the drug only if there is some critical change in the sensitivity to the drug.

Acetylcholine↗