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Biomedical subjects

K Imamura

Publications and source records attributed to K Imamura.

At least 181 records · Page 10Linked to original sources
PubMed1992

Differential specificities of single mitral cells in rabbit olfactory bulb for a homologous series of fatty acid odor molecules.

1. The molecular specificities of single mitral cells and their locations in the rabbit olfactory bulb were studied using extracellular recordings of single-unit spike discharges and oscillatory local field potentials. A panel of carboxylic acid molecules including a homologous series of fatty acids was used as odor stimuli. 2. Mitral cells showing excitatory responses to fatty acid molecules of different hydrocarbon chain length were localized near each other in a region in the dorsomedial part of the olfactory bulb. 3. Individual mitral cells in the dorsomedial region tended to respond to subsets of fatty acid odor molecules having similar hydrocarbon chain length or structure. Mitral cells responding to subsets of fatty acids of different chain length were distributed with partially shifted overlaps in this region. 4. The results show that stereochemical features of odor molecules are encoded by individual bulbar neurons.

Animals↗
PubMed1992

Coding of odor molecules by mitral/tufted cells in rabbit olfactory bulb. I. Aliphatic compounds.

1. Recordings of extracellular spike responses were made from single mitral/tufted cells in the main olfactory bulb of urethan-anesthetized rabbits. Olfactory epithelium ipsilateral to the recorded olfactory bulb was stimulated with homologous series of aliphatic compounds using periodic artificial inhalations. 2. In the dorsomedial part of the main olfactory bulb, single mitral/tufted cells were activated by subsets of n-fatty acids with similar hydrocarbon chain lengths. Response selectivities of single mitral/tufted cells were examined in detail using a series of n-fatty acids at five different concentrations. The results indicate that although the range of effective fatty acids is broader at the higher concentrations, the best response at higher concentrations was similar to that determined at lower concentrations. 3. Analysis of single-unit responses to the panel of fatty acids, including those with branched hydrocarbon chains, suggested that the determinants for the response specificities of individual mitral/tufted cells in the dorsomedial region include the overall size of hydrocarbon chains of the odor ligand molecules. 4. Single mitral/tufted cells in the dorsomedial region tended to be activated not only by fatty acids but also by n-aliphatic aldehydes. For a panel of a homologous series of n-aldehydes at five different concentrations, individual mitral/tufted cells showed response selectivity to subsets of aldehydes with similar hydrocarbon chain lengths. 5. In most cases, normal aliphatic alcohols and alkanes were ineffective in activating mitral/tufted cells in the dorsomedial region. This suggests that carbonyl group (--C = O) in the odor molecules plays an important role in determining response specificity of these neurons. 6. Examination with an expanded panel of stimulus odor molecules that included ketones and esters indicated that single mitral/tufted cells sensitive to subsets of fatty acids and n-aliphatic aldehydes were also responsive to subsets of ketones and/or esters having hydrocarbon chain lengths similar to those of the effective fatty acids and aldehydes. 7. The present results show a clear correlation between the tuning specificity of individual mitral/tufted cells and the stereochemical structure of the odor molecules, with respect to 1) length and/or structure of hydrocarbon chain, 2) difference in functional group, and 3) position of the functional group within the molecule. 8. A hypothetical diagram suggesting functional convergence of olfactory nerve input to individual glomeruli is proposed to explain the mechanism for selective activation of individual mitral/tufted cells by a range of odor molecules with similar stereochemical structures.

Action Potentials↗
PubMed1992

[Behaviors of crystalline waters of (RS)-7-(2-aminomethylmorpholino)-1- cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid].

Physicochemical characteristics of crystalline water of (RS)-7-(2-aminomethylmorpholino)-1-cyclopropyl-6,8-difluoro-1,4-di hydro-4-oxo-3-quinoline-carboxylic acid were studied by thermal analyses and powder X-ray diffractometry. The dihydrate of the compound was stable under ambient or humidified conditions. The dihydrate converted to a monohydrate on drying under mild conditions. The mono- and dihydrates transformed into alpha-type anhydrate at 110 degrees C. These three kinds of crystals were convertible each other under appropriate conditions. At 165 degrees C, the hydrates and the alpha-anhydrate converted to beta-type anhydrate. The compressed effects on the crystalline waters were also discussed for the dihydrate by kinetic analyses.

Chemical Phenomena↗
PubMed1992

What is the clinical disadvantage of discarding old radiographs? Survey of patients not re-examined for a long time.

The clinical disadvantage of discarding old radiographs was evaluated in patients who had not been re-examined for more than 8 years after their last radiological examination, 38,772 in total. During the 1 year survey, 158 (0.41%) of them underwent re-examination after a long interval. Retrospective evaluation revealed that in only 12 patients (0.032%) were the old films useful. This survey suggested that the clinical risk of not referring to films more than 8 years old would be less than 0.049%. We consider this acceptable, and have formulated new guidelines of storage of films.

Evaluation Studies as Topic↗
PubMed1992

On the visual recognition of moving letter.

The visual recognition (i.e., legibility) of moving object was studied. The numerical letters were mainly used as the objects. The influences of (1) direction of the movement, (2) thickness of line of letter (i.e., stroke width), and (3) design of letter to the visual recognition were measured. From these measurements, the optimal numerical letters were proposed in the first step of the study, which were called as IMAL(initial most optimal arabic letters). The visual recognition of both moving letters IMAL and letters JIS (Japan industrial standard) employed for motionless-state was compared for both the moving and the motionless states. In the presentation for motionless state, letters JIS showed lower error rate, but the statistical significance was not proved, while in the presentation for horizontally moving state letters IMAL showed better visual recognition than letters JIS was the significant level of 5%. Therefore, the useful numerical letters for moving state could be designed in the study. Moreover, the visual recognition of letters IMAL was evaluated for various moving velocities. The optimal moving velocities for both letters IMAL and JIS were found.

Computer-Aided Design↗
PubMed1992

Resistance to ketosis in moderately obese patients: influence of fatty liver.

To elucidate whether the presence of fatty liver influences ketogenesis in obesity, the metabolic and hormonal changes in basal and low-dose epinephrine (EPI)-stimulated states were studied in 12 obese patients (OB) with normal glucose tolerance, consisting of 6 without fatty liver (OBN) and 6 with fatty liver (OBF). In the basal state, the total ketone body (TKB) concentration and the TKB to free fatty acid (FFA) ratio were significantly (p < 0.01) lower in the OBF than in the OBN group, despite elevated, but comparable, FFA levels in both groups. The basal FFA level and the TKB/FFA ratio correlated with the degree of fatty liver (p < 0.05-0.01). EPI infusion resulted in accelerated lipolysis and diminished FFA-induced ketogenesis, similar to the findings of the basal data. These results suggest that fatty liver per se is related to diminished FFA-induced ketogenesis, leading to resistance to ketosis in obesity.

3-Hydroxybutyric Acid↗
PubMed1992

Vascularized toe-to-finger joint transplantation. 11 patients followed for 4 years.

Since 1983, we have transplanted 11 free vascularized joints in 8 men and 3 women, mean age 32 years. The causes of joint involvement were trauma in 9 cases and infection in 2. One MP and 10 PIP joints of the second toe were transplanted to 3 MP and 8 PIP joints of the fingers. After a mean postoperative follow-up period of 4 years, the mean postoperative range of motion was 31 degrees compared with 16 degrees preoperatively. Radiographs showed destruction of 4 PIP joints, probably caused by vascular failure in 2 joints and infection in 2. In spite of no evidence of arthrosis, some of the joints had gradually undergone a loss of extension. Although there are some problems that should be overcome, we advocate a free vascularized toe-joint transplantation for severe finger-joint destruction without extensive surrounding soft-tissue damage.

Adolescent↗
PubMed1992

[Senile osteoporosis in normal women examination using dual energy X-ray absorptiometry].

Osteoporosis is now one of the most serious problems in aged Japanese women. We investigated bone mineral contents of the vertebrae of 132 adult women (28-94y.o.) using dual energy X-ray absorptiometry (DEXA) in order to clarify the change of the bone mineral densities (BMD) with aging, and the influences of a diet and exercise on osteoporosis. In the women, BMD of the vertebrae increase to maximum level in 3 rd or 4 th decade of life, and then reduce with aging. The level of BMD is well matched with the index of osteopenia using the lateral view of vertebral X-ray. According as the BMD reduce, the number of bone fractures and the number of patients with bone fractures increase. More than 80% of the women whose BMD are less than 0.7 g/cm2 have bone fractures. In aged women, over 65 year's old, exercise had significant positive effect with BMD, but that was no evidence for influence of calcium intake to BMD.

Absorptiometry, Photon↗
PubMed1992

A case of liver cirrhosis with an unusual portosystemic shunt via the right testicular vein.

We report a case of liver cirrhosis with a rare portosystemic shunt via the right testicular vein. Angiographic examination demonstrated two major hepatofugal collateral pathways. First, the enlarged and tortous left gastric and short gastric veins which drain into the left renal vein after forming varices in the stomach. Second, the superior mesenteric vein forms the large mesenteric varices which drain into the inferior vena cava via the enlarged right testicular vein, which is a very rare shunt.

Humans↗
PubMed1992

[Cytokine production by peripheral blood monocytes/macrophages in the patients with multiple sclerosis and its suppression by methylprednisolone].

The production of tumor necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) by stimulated peripheral blood monocytes/macrophages (PBM) was assessed in patients with multiple sclerosis (MS), other neurological diseases (OND) or normal controls (NC) using enzyme-linked immunosorbent assay (ELISA). PBM obtained from acute phase of MS produced significantly higher amount of all these cytokines than those from chronic stable MS, OND or NC (TNF alpha, IL-1 alpha, IL-6: p less than 0.01, IL-1 beta: p less than 0.05). Methylprednisolone (MP) inhibited the lipopolysaccharide-induced cytokine production in a dose-dependent manner. These results suggest the possible roles of activated monocytes/macrophages in the acute exacervation of MS and suppressive effect of MP on cytokine production by activated monocytes/macrophages.

Adult↗
PubMed1991

Purification and characterization of N-acyl-D-glutamate deacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6.

The purification and properties of N-acyl-D-glutamate deacylase from the cell extracts of Alcaligenes xylosoxydans subsp. xylosoxydans A-6 were studied. The two active fractions (peaks I and II) were obtained by a Mono Q column chromatography. The predominant enzyme (peak I) has been purified, 1960-fold to homogeneity and characterized. The enzyme was a monomer with a molecular weight of 59,000. The optimum pH and the isoelectric point were 8.0 and 5.5, respectively. The enzyme catalyzed the hydrolysis of N-acyl derivatives of D-glutamate. The Kms for N-acetyl, N-butyryl and N-propionyl derivatives of D-glutamate were 0.129, 0.066 and 0.01 mM, respectively.

Alcaligenes↗
PubMed1991

Lithium reduces ocular dominance plasticity in kitten visual cortex.

Activity-dependent processes within the visual pathway play a crucial role in the expression of ocular dominance plasticity in immature visual cortex. The necessity of non-retinal, modulatory afferents to the regulation of ocular dominance plasticity has been recognized. Among a few chemically defined signaling systems, the noradrenaline-activated beta-adrenoreceptors seem to have a prime role in this matter. The involvement of acetylcholine afferents was also proven. We looked for plausible molecular mechanisms which integrate the contribution of the two neuromodulator systems to ocular dominance plasticity. At the first step, based on the rich literature on psychotropic action of lithium and the recent advancement in understanding of its molecular mechanisms, we physiologically studied visual cortex of kittens which had been repeatedly injected with the lithium solution intraperitoneally or the cortex directly infused with it. We found (1) that ocular dominance plasticity was significantly reduced in lithium-injected kittens, (2) that the decrease was directly correlated with plasma concentrations of lithium (i.e. the higher the lithium concentration, the lower the plasticity), and (3) that the comparable decrease in the plasticity was obtained from kitten visual cortex which had been directly infused with the lithium solution. The present results suggest that lithium-sensitive processes, through most likely reduced production of second messengers, underlie the regulation of ocular dominance plasticity.

Animals↗
PubMed1991

6R-tetrahydrobiopterin perfusion enhances dopamine, serotonin, and glutamate outputs in dialysate from rat striatum and frontal cortex.

The effect of 6R-tetrahydrobiopterin (R-THBP) on neurotransmitter release was investigated using in vivo brain microdialysis in urethane-anesthetized rats. Perfusion of 1.0 mM R-THBP enhanced the level of dopamine output in dialysates collected from the striatum and frontal cortex. R-THBP perfusion also increased serotonin (striatum) and glutamate outputs (striatum and frontal cortex). Dopaminergic terminals in the striatum were destroyed unilaterally by continuous infusion of 6-hydroxydopamine (6-OHDA) using an osmotic minipump system. The effect of R-THBP administration on glutamate level was found to be almost completely suppressed in the 6-OHDA-lesioned side of striatum, while in the intact side of striatum the glutamate level in the dialysates responded normally to R-THBP perfusion. These results suggest that R-THBP may play a role in the mechanisms of release of dopamine, serotonin, and glutamate. The functioning of the catecholaminergic system probably mediates the increase in glutamate output due to R-THBP perfusion.

Animals↗
PubMed1991

Localization of prostaglandin endoperoxide synthase in neurons and glia in monkey brain.

The localization of prostaglandin endoperoxide synthase in monkey brain was investigated by the immunoperoxidase method using the monoclonal antibody (PES-7) raised against the enzyme purified from bovine seminal vesicle. The frozen sections with 30-microns thickness were employed after the brain was fixed with perfusion of 2% paraformaldehyde in phosphate-buffered saline. The immunoreactivity was most intense in the neurons of cerebral cortex and hippocampus, and was moderate in the neurons of caudate nucleus, putamen, globus pallidus and amygdala, while it was relatively weak in glial cells in the whole brain regions including the white matter. The majority of neurons showed the immunoreactivity in the somata and proximal dendrites, but exceptionally in the pyramidal cells of the hippocampus, positive staining was also observed in the apical dendrites. In the cerebellum, the immunoreactivity in both neurons and glia was rather faint as compared with that in other regions. Positive staining was not significantly observed in the vasculatures and arachnoid membranes. These findings indicate that most of neuronal and glial cells in monkey brain contain the enzyme of the rate-limiting and initial step of the biosynthesis of prostaglandins which regulate a variety of neural functions.

Animals↗
PubMed1991

[How many years should we keep films?].

In our university hospital, all of the radiographs have been stored since the hospital opening in 1974, and they can be retrieved easily. The total number of jackets is about 230,000. Access rates to them were surveyed, and it became clear that inactive jackets were increasing with the age of the hospital. On the contrary, fraction of active jackets increased slightly. Five radiologists evaluated the usefulness of referring to the previous films in the film reading processes. Subjects were 158 patients who were examined after the interval of 8 years or more. Assuming to discard their previous radiographs, the simple inaccessibility risk was 0.41% and the risk decreased to 0.0026% taking the clinical disadvantage into consideration. Risk to research works was estimated as 0.97%. Based on these surveys and evaluations, our university decided to discard radiographs of patients who had not revisited these 10 years with the exception of important cases for researches.

Humans↗
PubMed1991

Role of prostaglandins in interleukin-1-induced bone resorption in mice in vitro.

The mechanism of bone resorption induced by interleukin 1 (IL-1) was examined in mice using three different in vitro assay systems: a fetal long bone organ culture system, a bone marrow culture system, and a coculture system of primary osteoblastic cell populations and spleen cells. In the organ culture system, recombinant human IL-1 alpha (rhIL-1 alpha) increased both bone resorption and osteoclast number. Both were partially suppressed in the presence of indomethacin. In the marrow culture, both rhIL-1 alpha and rhIL-1 beta stimulated osteoclastlike cell formation, which was completely inhibited by adding indomethacin concurrently. Furthermore, there was a good correlation between the number of osteoclastlike cells formed and the amount of prostaglandin E2 (PGE2) released into the culture media. This indicates that PGE2 is involved in the mechanism of IL-1-mediated osteoclastlike cell formation. In the coculture of primary osteoblastic cell populations and spleen cells, rhIL-1 again stimulated osteoclastlike cell formation, which was inhibited by adding indomethacin. In the cocultures in which direct interaction between osteoblastic cells and spleen cells was inhibited, PGE2 synthesis was similarly increased but no osteoclastlike cells were formed. These results indicate that IL-1 induces osteoclast formation by a mechanism involving PG (most likely PGE2). Furthermore, direct interaction between osteoclast progenitors and osteoblastic cells is required in the osteoclast recruitment induced by IL-1.

Acid Phosphatase↗