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Biomedical subjects

M Amano

Publications and source records attributed to M Amano.

At least 145 records · Page 8Linked to original sources
PubMed1994

Pigmentary retinopathy with nephrotic syndrome, Ménétrier's disease, and diabetes mellitus.

A patient with pigmentary retinopathy, nephrotic syndrome, Ménétrier's disease, and diabetes mellitus is presented. Other complications were congestive heart failure, hypothyroidism, hypertension, and hypertriglyceridemia. Hypogenitalism was also suspected. Pigmentary retinopathy is known to associate with many systemic diseases, which are classified into several syndromes. This case superficially resembles Alström's disease due to the common characteristics of pigmentary retinopathy, diabetes mellitus, renal disease, and hypogenitalism. But clinically and histologically, there are distinct differences. To our knowledge, this association has never been reported.

Consanguinity↗
PubMed1994

Acellular and cellular hemoglobin solutions as vasoconstrictive factor.

The inhibitory effects of acellular and cellular hemoglobin (Hb) solutions on endothelium-dependent vasorelaxation were investigated in rabbit thoracic aortic strips. As acellular Hb solutions, 2,3-diphosphoglycerate (DPG)-depleted Hb and pyridoxylated Hb were examined. Cellular Hb solutions included washed human fresh red cells and liposome Hb encapsulated with pyridoxal-5'-phosphate (PLP). The tissues were precontracted with phenylephrine (PE), after which acetylcholine (ACh) was added to elicit a steady-state relaxation. Acellular Hb solutions cumulatively reversed ACh-induced relaxation, and these inhibitory effects reached a plateau at 10 micrograms/ml. Increasing oxygen affinity by pyridoxylation had little effect on this. In contrast, both red cells and liposome Hb solution showed moderate inhibitory effects, and they reached a plateau at 1 mg/ml. These findings indicate that acellular Hb solutions are more potent inhibitors than cellular Hb solutions by a factor of about 100, and that the encapsulation of Hb is a preferable method to mimic the red cell.

2,3-Diphosphoglycerate↗
PubMed1994

The quality control of stroma-free hemoglobin: lysophosphatidylcholine, a component of stromal phospholipids, as candidate vasoconstrictive factor.

We characterized stromal phospholipids in stroma-free hemoglobin (SFH) by normal-phase and cation-exchange HPLCs, and found that SFH contained not only four phospholipids which were the major constituent classes in membrane, but also several peaks which were not yet identified. The residual amounts of these lipids in SFH were changed with storage of red cell concentrates. The four major phospholipids decreased concomitantly with storage, whereas the unidentified peaks increased after 21 days and then decreased after 48 days. We also found that SFH contained lysophosphatidylcholine (LPC) at 5.71 micrograms/ml, which was the deacylated metabolite of phosphatidylcholine (PC). These results suggest that stromal phospholipids are degradable. Since LPC is known to be capable of producing a defect in endothelium-dependent arterial relaxation, we next examined the effect of stromal lipids on vascular tone in rabbit thoracic aortic strips. Preincubation with the crude lipid extract or the LPC purified from SFH by TLC significantly inhibited acetylcholine (ACh)-induced relaxation in phenylephrine (PhE)-precontracted tissues. These observations have led to the proposal that LPC, a component of stromal phospholipids, induces vasoconstriction as a result of inhibition of endothelium-dependent vasorelaxation.

Animals↗
PubMed1994

[CD7 positive undifferenciated leukemia/lymphoma associated with leukemic pericarditis].

We report here a CD7 positive undifferenciated leukemia/lymphoma which showed a rapid clinical course. A 27-year-old female was complained of palpitation and edema. She had a mediastinal tumor and pericardial effusion. Lymphoblastic cells were found in the effusion, but in the peripheral blood initially. After admission the blast cells appeared in the peripheral blood, and they were revealed negative for peroxidase and had phenotype of CD7 and CD33 positive. The patient suffered from cardiac tamponade and died 15 days after admission. The Southern blotting of mediastinal tumor cells disclosed the germline configuration for TCR-beta a chain and the rearrangement of immunoglobulin heavy chain genes.

Adult↗
PubMed1994

[Attenuation correction using postinjection transmission measurements for PET: the optimization of measurement conditions].

A new method of PET attenuation using post-injection transmission scan is presented, which is especially useful in 18F-FDG static studies. The transmission scan is acquired right before the emission scan, which is used to subtract the emission component from the transmission data. When the effect of measurement condition upon the image noise was evaluated with a 20 cm diameter cylindrical phantom, an increase in the injection dose inflated the noise and caused artifacts. There was an optimum dose that minimized the image noise. As the external source activity increased, the image noise decreased, and the optimum dose increased linearly, which enabled estimation of the optimum injection dose under a given external source. When the total (emission plus transmission) scan time was fixed, longer emission scan resulted in better images than longer transmission scan.

Gallium Radioisotopes↗
PubMed1993

N-methyl-D-aspartate receptors but not non-N-methyl-D-aspartate receptors mediate hypertension induced by carotid body chemoreceptor stimulation in the rostral ventrolateral medulla of the rat.

In urethane-anesthetized rats, excitatory amino acid antagonists were microinjected into the rostral ventrolateral medulla (RVLM) and their effects on the pressor response and tachycardia evoked by carotid chemoreceptor stimulation were examined. Microinjections of the N-methyl-D-aspartate (NMDA) receptor antagonists 2-amino-5-phosphonovalerate (AP5) and MK-801 into the RVLM inhibited these chemoreceptor reflex responses whereas these responses were not affected by injection of the non-NMDA receptor antagonist CNQX. AP5 and MK-801 but not CNQX abolished the pressor response evoked by NMDA whereas CNQX but not AP5 and MK-801 abolished that evoked by AMPA or kainate. These results provide evidence that NMDA receptors in the RVLM of the rat are involved in the carotid chemoreceptor reflex.

Animals↗
PubMed1993

Nuclear magnetic resonance study of the codon-anticodon interaction in Bombyx mori tRNA(GCCGly).

NMR spectra of Bombyx mori tRNA(GCCGly) were recorded in the GCC absence and presence of the oligonucleotide, GGCUp, which contains the codon sequence, GGC. The difference between the spectra with and without the codon oligonucleotide indicates the appearance of five new imino proton peaks. For the assignment of these peaks, G*GCUp, in which the 5'-terminal G was enriched with 95% 15N, was prepared (G*, 15N-labeled guanosine). In the imino proton spectrum of B. mori tRNA(GCCGly) on the addition of G*GCUp, the peak at 12 ppm became a doublet due to coupling with 15N nuclei. In the two-dimensional 1H-15N heteronuclear multiple-quantum correlation (HMQC) spectrum, only the peak at 12 ppm was observed, and thus it was assigned to the imino proton of the 5'-terminal G of GGCUp interacting with tRNA(GCCGly). Judging from the temperature effect and chemical shifts, the five new imino proton peaks are presumed to be due to three G.C base pairs, induced by the codon-anticodon interaction, and one U.U base pair, induced by an interaction between the 3' terminal U of GGCUp and U33 neighboring the anticodon. The binding of three trinucleotides (GGCp, GGUp and GCUp) to B. mori tRNA(GCCGly) was also investigated. Ultracentrifugation analysis showed that tRNA(GCCGly) underwent dimerization through the anticodon-anticodon interaction, but the dimerization was broken on addition of GGCUp. On 1H-NMR and ultracentrifugation analysis, it was found that GCUp not complementary to the anticodon also binds to the anticodon loop.

Animals↗
PubMed1993

Application of the ILISPOT-IDIP system for the enumeration of different sizes of IgA spot forming cells in the murine small and large intestine.

The immunofluorescence-linked immunospot (ILISPOT) assay associated with the immunofluorescence digital image processing (IDIP) system was originally developed in our laboratory to allow enumeration of immunoglobulin (Ig) producing, spot forming cells (SFC) in a more objective and quantitative manner. In this study, the ILISPOT-IDIP system was further advanced in order to analyze different sizes of SFC (e.g., IgA producing cells) including large (L), medium (M), and small (S) cells which correspond to high (> 2.4 pg), medium (1.2-2.4 pg) and low (< 1.2 pg) IgA secreting cells by the adaptation of real time image processor and intensified video camera system. When the ILISPOT-IDIP system was used to characterize the frequency of IgA secreting cells among mononuclear cells isolated from different parts of the murine gastrointestinal (GI) tract including the small (upper, middle and lower sections) and large (colon and rectum) intestine, the small intestine contained higher numbers of IgA SFC (approximately 8.4 x 10(5) SFC/10(6) cells) when compared with large intestine (approximately 1.3 x 10(5) SFC/10(6) cells). Among the 3 areas of small intestine, the upper (approximately 3.7 x 10(5) SFC/10(6) cells) and middle (approximately 2.4 x 10(5) SFC/10(6) cells) parts had higher numbers of IgA SFC when compared to the lower small (approximately 2.3 x 10(5) SFC/10(6) cells) intestine. When these IgA producing cells in different parts of the intestine were classified into three groups according to the size of individual spots, the upper and middle intestine contained higher frequencies of large (approximately 20%) and medium (approximately 20%) SFC which corresponded to high and medium IgA secretors in comparison to the lower small (approximately 9%) and large (approximately 6%) intestine. In contrast, the lower small and large intestine were dominated by small SFC since approximately 85% of IgA producing cells were categorized as low secretors. Using the advanced ILISPOT-IDIP system, a unique distribution of different sizes (or secretion rates) of IgA producing SFC was elucidated in the different regions of the mouse small and large intestine.

Animals↗
PubMed1993

MK-801 increases endogenous acetylcholine release in the rat parietal cortex: a study using brain microdialysis.

Glutaminergic and cholinergic neuronal interactions were investigated by using the brain microdialysis method in freely-moving rats. Acute administration of (+)-10,11-dihydro-5-methyl-5H-dibenzo[a,d]cyclohepten-5, 10-imine hydrogen maleate (MK-801) increased dose-dependently the extracellular acetylcholine (ACh) level in the rat parietal cortex. Significant increases in the extracellular ACh level were observed at doses of 0.4 and 0.5 mg/kg of MK-801, compared with the saline-treated group. The increase of extracellular ACh level was eliminated by infusion of 10(-2) M N-methyl-D-aspartate (NMDA). These results suggest that the glutaminergic neuronal system regulates functions of the cholinergic neuronal system.

Acetylcholine↗
PubMed1993

Involvement of both GABAA and GABAB receptors in tonic inhibitory control of blood pressure at the rostral ventrolateral medulla of the rat.

The rostral ventrolateral medulla (RVLM) contains vasopressor neurons which increase vasomotor tone. Endogenous GABA is suggested to be involved in mediation of the tonic inhibition of vasopressor neurons in the RVLM. To obtain more precise information about GABAergic mechanisms in the RVLM, we microinjected GABA agonists and antagonists unilaterally into the RVLM and examined their effects on blood pressure and heart rate. In addition, involvement of the other inhibitory amino acids glycine, beta-alanine and taurine in blood pressure regulation in the rat RVLM was also investigated. Male Wistar rats were anesthetized with urethane, paralyzed and artificially ventilated. The GABAA agonist muscimol (3-30 pmol) and the GABAB agonist baclofen (10-100 pmol) microinjected into the RVLM produced a decrease in blood pressure. The GABAA antagonist bicuculline (300 pmol) abolished the depressor response to muscimol (10 pmol) but not to baclofen (30 pmol) whereas the GABAB antagonist 2-hydroxysaclofen (1 nmol) abolished the depressor response to baclofen (30 pmol) but not to muscimol (10 pmol). Either bicuculline or 2-hydroxysaclofen alone produced a pressor response. Both antagonists inhibited depressor responses to nipecotic acid (7.7 nmol) and GABA (0.3 nmol). Glycine (0.13-4.0 nmol), beta-alanine (0.11-3.4 nmol) and taurine (0.08-2.4 nmol) microinjected into the RVLM also produced decreases in blood pressure. The glycine antagonist strychnine (0.58 nmol) abolished the depressor response to glycine, beta-alanine and taurine but not to GABA. The taurine antagonist 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide) (1.3 nmol) inhibited the depressor response to beta-alanine and taurine but not to glycine and GABA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Studies on as-triazine derivatives. XIX. Synthesis of 2,3-diarylpyrazine 2,3-diarylpyridine derivatives as blood platelet aggregation inhibitors].

4,5-Diphenyl-2-ethoxypyrimidine (1), 3,4-diphenyl-6-ethoxypyridazine (2) and 2,3-diphenyl-5-ethoxypyrazine (3) were evaluated for inhibitory activity towards arachidonic acid-induced aggregation of rabbit blood platelet in vitro. 2,3-Diphenyl-5-ethoxypyrazine (3) exhibited significant inhibitory activity. Thus, various 5-substituted 2,3-bis(4-methoxyphenyl)pyrazines were synthesized by the nucleophilic substitution reaction of 5-chloro-2,3-bis(4-methoxyphenyl)pyrazine (9). In a similar manner, substituted 2,3-bis(4-methoxyphenyl)pyridines were prepared from 2,3-bis(4-methoxyphenyl)-6-methylsulfonylpyridine (17), which was synthesized by the cycloaddition retro Diels-Alder reaction of 5,6-bis(4-methoxyphenyl)-3-methylsulfonyl-1,2,4-triazine (16) with norbornadiene. Among the compounds prepared, 6-isopropoxy-2,3-bis(4-methoxyphenyl)-pyrazine (10f) showed the most potent inhibitory activity, which was more than the activity of anitrazafen[5,6-bis(4-methoxyphenyl)-3-methyl-1,2,4-triazine.

Animals↗
PubMed1993

Effects of BMY-21502 on anoxia in mice.

The protective effects of BMY-21502 (1-[[1-[2-(trifluoromethyl)-4-pyrimidinyl]-4-piperidinyl]methyl]-2- pyrrolidinone) against cerebral anoxia were investigated using various models in mice, in comparison with those of other cerebroactive drugs. Oral administration of BMY-21502 (10-100 mg/kg) significantly prolonged the survival time in KCN (2.4 mg/kg, i.v.)-induced anoxia. Oxiracetam and idebenone exerted similar but weak protection at doses above 100 mg/kg, p.o. and only at a dose of 100 mg/kg, p.o., respectively. Significant protection by BMY-21502 against moderate hypobaric hypoxia was observed at doses of 30 and 100 mg/kg, p.o. Idebenone (100 and 300 mg/kg, p.o.) significantly prolonged the survival time of mice in this model, but oxiracetam (30-300 mg/kg, p.o.) did not. Oral administration of all of these drugs (BMY-21502, 3-300 mg/kg; Oxiracetam, 100-1000 mg/kg; Idebenone, 100-1000 mg/kg) failed to increase the number of gasps and the duration of gasping in the decapitated head of mice as a complete ischemic model. The anti-anoxic effect of BMY-21502 in the KCN-anoxia model was blocked by pretreatment with scopolamine. These findings suggest that BMY-21502 has an anti-anoxic action superior to those of the other cerebroactive drugs used, and activation of the CNS cholinergic system is involved as one of the causative mechanisms for the anti-anoxic effect of BMY-21502.

Animals↗
PubMed1993

Comparison of the anticonflict effect of buspirone and its major metabolite 1-(2-pyrimidinyl)-piperazine (1-PP) in rats.

The anxiolytic effects of buspirone and its major metabolite, 1-(2-pyrimidinyl)-piperazine (1-PP) have been investigated with a conflict (shock-induced suppression of drinking) paradigm in rats. Buspirone (10 mg/kg, p.o.) showed an anticonflict activity with a bell-shaped dose-response relationship without any effect on spontaneous water consumption. Higher doses of buspirone reduced the punished response. Diazepam (20 and 40 mg/kg, p.o.) also showed an anticonflict activity in a dose-dependent manner, but animals with diazepam showed an increase in spontaneous water consumption at these doses. On the other hand, 1-PP (6.25-200 mg/kg, p.o.) showed a weak anticonflict activity with a significant effect at 25 mg/kg without any effect on spontaneous water consumption. In the 7-day treatment test, buspirone (5 and 10 mg/kg, p.o.), 1-PP (5 and 25 mg/kg, p.o.) and diazepam (10 and 40 mg/kg, p.o.) did not develop the tolerance to the anticonflict activity. Conversely, the anticonflict activity of diazepam was increased by the repeated treatment. Diazepam (10 mg/kg, p.o.) showed an anticonflict activity without any effect on spontaneous water consumption in this test. These results demonstrated that buspirone clearly exhibited an anticonflict effect similar to that of diazepam in a Vogel-type conflict test, and its real anxiolytic effect may not be always based on 1-PP, the main metabolite of buspirone.

Animals↗
PubMed1993

Characteristics of transient cerebral ischemia-induced deficits on various learning and memory tasks in male Mongolian gerbils.

We examined the characteristics of 5-min cerebral ischemia-induced behavioral deficits in spontaneous locomotor activity and their effects on the performance of habituation (HAB), passive avoidance (PA) and 8-arm radial maze (RM) tasks in Mongolian gerbils. Performances in HAB, PA and RM were impaired within 2 days after occlusion, and gerbils showed hyperlocomotion during this period. Ten days after ischemia, the hyperlocomotion disappeared and performance in the HAB and PA was the same as that in the sham-operated group. Retention in the RM was impaired at that period, but this impairment was overcome, and retention recovered easily to the sham-operated level with a few additional trials. When the acquisition trial in the RM began at 11 days after occlusion, severe learning impairment was found. Destruction of hippocampal CA1 neurons appears from 2-3 days after ischemic insult, with most CA1 neurons having disappeared by day 7. These findings suggest that the impairment of performance in the HAB and PA within 2 days after occlusion may be related to an early phase of CA1 neuronal death and to hyperlocomotion, although the impairment of spatial learning and memory was clearly associated with CA1 injury 10 days after ischemia.

Animals↗
PubMed1993

beta-Alanine and taurine microinjected into the rat caudal ventrolateral medulla increase blood pressure.

Unilateral microinjections of GABA, glycine, beta-alanine and taurine into the caudal ventrolateral medulla (CVLM) of the rat, led to an increase in blood pressure and heart rate. The responses to glycine, beta-alanine and taurine but not to GABA could be blocked by strychnine. The responses to taurine and beta-alanine but not to GABA and glycine could be blocked by 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide (TAG), an antagonist of taurine. The taurine antagonist alone injected bilaterally into the CVLM produced a decrease in blood pressure. From CVLM areas microperfused with Krebs solution, spontaneous release of GABA, glycine, beta-alanine and taurine was detected and high K+ stimulation caused a calcium-dependent release of GABA, beta-alanine and taurine. These results suggest that beta-alanine and taurine as well as GABA may be involved in modulation of the cardiovascular control within the CVLM.

Animals↗
PubMed1993

[Impairment of learning and memory and the accessory symptom in aged rats as senile dementia model (1)--Emotional behavior].

It is well known that there is an increase of emotional behavior in senile dementia. There are few studies investigating age-related emotional behavior. We attempted to investigate emotional behavior of aged rats using various tests. Locomotor activity for 24 h decreased in aged rats compared with that in young rats. There was no difference in locomotor activity between light and dark periods in aged rats. There was no visual abnormality on light/dark discrimination test in aged rats. It suggests that locomotor activity during dark period may be impaired by aging. Head-dips and social interaction time in hole board and social interaction tests, respectively decreased, while start latency, defecation and urination in open field test increased in aged rats. Furthermore, ambulation and rearing in hole board, social interaction and open field tests decreased, and entries into open or closed arms in elevated plus-maze test reduced in aged rats compared with those in young rats. These findings suggest that anxiety may increase, but spontaneous activity decrease in aged rats. These results indicate that aged rats may be useful as an accessory symptom model of senile dementia.

Aging↗
PubMed1993

[Impairment of learning and memory and the accessory symptom in aged rats as senile dementia model (2)--Learning and memory].

We attempted to investigate the ability of learning and memory of aged rats. Swimming speed of aged rats in Morris's water maze was slower compared with that of young rats. Therefore, we used goal distance to indicate ability of learning and memory. In training session, distance for both groups decreased with training, but in aged rats it was significantly longer than that in young rats. In retention test 24 d after the training, distance in aged rats was longer than that in young rats, although there was no difference in distance for both groups between acquisition and retention tests. The distance in the working memory tended to increase with aging. There was no difference in time spent within platform phase in probe trial, in percent movement of first trial in habituation test, and in step-through latency in passive avoidance, between young and aged rats. Drinking latency for aged rats in water finding task was significantly longer compared with that in young rats. These findings suggest that learning and memory were impaired by aging in spatial and latent learning tasks. Aged rats could acquire and maintain memory of simple tasks, but in spatial tasks they tended to show decreased ability of retention and working memory.

Aging↗