Search PubMed⌕ Search

Biomedical subjects

N Maeda

Publications and source records attributed to N Maeda.

At least 433 records · Page 24Linked to original sources
PubMed1991

Structural and functional characterization of inositol 1,4,5-trisphosphate receptor channel from mouse cerebellum.

The cerebellar inositol 1,4,5-trisphosphate (InsP3) receptor is a high molecular weight glycoprotein abundantly expressed in Purkinje cells. The subunit structure of the InsP3 receptor protein was examined by cross-linking experiments. Agarose-polyacrylamide gel electrophoresis of the cross-linked materials demonstrated that the cerebellar InsP3 receptor protein is composed of four noncovalently bound identical subunits each with a Mr of 320,000 in both purified and microsome-bound states. Chromatography of the purified receptor on a calmodulin-Sepharose column demonstrated a Ca2(+)-dependent interaction of the InsP3 receptor with calmodulin. Photoaffinity labeling of the cerebellar microsomal fraction with [alpha-32P]8-azidoadenosine 5'-triphosphate revealed the presence of ATP-binding site in the InsP3 receptor. Scatchard analysis of the purified InsP3 receptor revealed the Bmax and Kd values for ATP binding of 2.3 pmol/micrograms and 17 microM, respectively. Reconstitution of the purified InsP3 receptor into the planar lipid bilayer indicated channel activity in the purified receptor. It exhibited a calcium conductance (26 pS in 53 mM Ca2+) and sodium conductance (21 pS in 100-500 mM asymmetric Na+ solutions) with permeability ratios of PCa/PTris = 6.3 and PNa/PCl = 5.4. The purified channel was activated with submillimolar ATP in the presence of InsP3 and modified to reach a large conductance state.

Affinity Labels↗
PubMed1991

Regulation of cell-surface galactosyltransferase in isoproterenol-treated mouse parotid glands.

Chronic injection of isoproterenol into mice resulted in hypertrophy and hyperplasia of the parotid gland. As previously described for the rat, cell proliferation was accompanied by an increase in total membrane-associated galactosyltransferase. A plasma membrane localization was determined by fluorescence-activated sorting of intact cells. Co-administration of the galactosyltransferase modifier protein, alpha-lactalbumin, or the calmodulin inhibitor, trifluoperazine, blocked acinar cell proliferation by 96 h post-treatment but not at 24 h. While alpha-lactalbumin appeared to interfere with galactosyltransferase-substrate interactions, trifluoperazine prevented the appearance of cell-surface enzyme in isoproterenol-treated animals.

Animals↗
PubMed1991

Calcium distribution and mobilization in single rat parotid acinar cells investigated by digital imaging microscopy.

The intracellular distribution and mobilization of cytosolic free calcium in single rat parotid acinar cells was analyzed by a digital imaging microscope equipped with a microspectrofluorometer, using calcium-sensitive dye fura-2. In the resting state, intracellular distribution of cytosolic free calcium concentration ([Ca2+]i) was heterogeneous: [Ca2+]i in the nuclear and perinuclear region was usually higher than that in the cytoplasm. By Ca(2+)-ionophore ionomycin and muscarinic agonist carbachol stimulation in the presence of 1 mM extracellular Ca2+, [Ca2+]i increased markedly and the gradient of [Ca2+]i between the nuclear region and the cytoplasm decreased. In ionomycin stimulation, [Ca2+]i increased homogeneously and this homogeneous increase was irreversible. In carbachol stimulation the gradient of [Ca2+]i between the nuclear region and the cytoplasm obviously reappeared within 2 min. By carbachol stimulation in the absence of extracellular Ca2+ (added 1 mM EGTA), [Ca2+]i returned to the prestimulation level after the initial transient increase. The distribution of [Ca2+]i also returned approximately to the prestimulation state. The gradient of [Ca2+]i between the nuclear region and the cytoplasm did not disappear even when [Ca2+]i elevated at the peak value.

Animals↗
PubMed1991

Immunohistochemical expression of P400 protein in Purkinje cells of sphingomyelinosis mouse.

Immunohistochemical expression of P400 protein, a glycoprotein localized to the Purkinje cell membrane, has been studied in the cerebellum of spm mouse using anti-P400 monoclonal antibody. The initial change observed in the Purkinje cells was a swelling of the cell body with distortion of the neurites; this occurred as early as 5 weeks of age. A significant, patchy loss of Purkinje cells started at 6 weeks before cerebellar signs became manifest. With progression of the disease the dendritic processes in the molecular layer showed a marked swelling, followed by irregular arborization and finally by disintegration. A few, heterotopic Purkinje cells were found in the subcortical white matter; this was interpreted as an indication that a disturbance in neuronal migration could be superimposed on the sphingolipid metabolic disorder. Additionally, P400-immunoreactive nerve cells were occasionally encountered in areas of the deep cerebellar nuclei and in the lateral vestibular nuclei of the pontine tegmentum. The number of P400-immunoreactive Purkinje cells correlated well with the percentages of the remaining Purkinje cells during the ages of 4 to 7 wks. At the late stage of 10 to 12 weeks almost all Purkinje cells had lost their P400-immunoreactivity. It is suggested that Purkinje cells that fail to express P400 protein may undergo an immunohistochemical degeneration of the plasma membrane.

Aging↗
PubMed1991

Closure of big toe defects after wrap-around flap transfer using the arterialized venous flap.

Sixteen arterialized venous flaps, free flaps that have arterial blood only flowing through the vein of the flap, were applied to reconstruct skin defects of the big toe resulting from wrap-around flap transfers. There were seven complete successes, six partial successes, and three complete failures. The clinical course of the cases indicated that the donor site itself and flap tension due to postoperative edema might play key roles in flap survival. The success rates of the flap from the leg and foot donor sites (including partial survival cases) were 75 percent and 87.5 percent, respectively. Flaps from the leg donor site appeared to develop more extensive postoperative congestion and edema than those from the foot donor site, which had a negative effect on flap survival. Covering the big toe with this flap causes no significant morbidity. The technique may have potential indications for closing a big-toe defect after a wrap-around flap transfer.

Adolescent↗
PubMed1991

Nerve regeneration in rat composite-tissue allografts.

Reinnervation of composite-tissue allografts was examined in a rat hind-limb transplant model under Cyclosporin A (CyA) immunosuppression. Two groups of animals were studied. Group 1 consisted of 10 composite-tissue allografts using inbred Fisher rats (F344) as recipients and inbred Lewis rats (LEW) as donors. Recipient animals received 15 mg/kg/day CyA subcutaneously for three weeks and then twice weekly for three months. Group 2 consisted of 10 composite-tissue isografts undergoing no immunosuppression, and using F344 as both donors and recipients. Eight months after operation, electromyographic, histologic, and morphometric assessments of nerve regeneration were made. There were no significant electromyographic differences between these two experimental groups in amplitude and conduction velocity, but the levels were lower than in controls. The histologic patterns of nerve regeneration within the composite-tissue transfers were similar in the two groups. However, the fiber population in the regenerated nerves in the two groups was different from that in the normal sciatic nerve. This study confirmed the reinnervation of composite-tissue allografts under CyA immunosuppression. The quality of regeneration in allografts was similar to that in isografts, but the histologic and electromyographic properties of regenerated nerves were different from those of normal sciatic nerves.

Animals↗
PubMed1991

Stacks of flattened smooth endoplasmic reticulum highly enriched in inositol 1,4,5-trisphosphate (InsP3) receptor in mouse cerebellar Purkinje cells.

By immunogold electron microscopy we have shown that in mouse cerebellar Purkinje cells fixed by perfusion with formaldehyde-glutaraldehyde solution, the InsP3 receptor are numerously detected on the stacks of flattened cisterns (OTSU et al, (1990) Cell Struct. Funct., 15: 163-173). In the present experiment we investigated distribution, structure and properties of the stacks by conventional electronmicroscopy, lectin cytochemistry and immunoelectron microscopy. The size and number of stacks were variable depending on their intracellular localization; short stacks with 2-4 parallel cisterns predominate in the perikaryon, long stacks with 4-15 cisterns in the proximal dendrite, and long stacks with 3-4 cisterns in the distal dendrites. The flattened cisterns bind with concanavalin A but not with wheat-germ agglutinin and may contain KDEL proteins loaded with Lys-Asp-Glu-Leu at their C-terminin in their lumens, indicating that the cisterns are derived from ER membranes. The electron dense materials sandwiched between the cisternal membranes are composed of small particles, short cylindrical in shape and approximately 20 nm in diameter, and markedly labeled with anti InsP3R antibody. We suggest that they correspond to the tetramer of the InsP3R or their related molecules. It is not clear whether the stacks of flattened cisterns exist per se in the Purkinje cells or smooth ER existing in singlet in vivo in the Purkinje cells forms stacks during fixation. It is strongly suggested, however, that the smooth ER membranes covered by the InsP3R or their related molecules can easily interact and stack each other in the Purkinje cells.

Animals↗
PubMed1991

Optical measurement of perfused rat hindlimb muscle with relation of the oxygen metabolism.

Optical measurements of myoglobin (Mb) and cytochromes (Cyts) in the isolated rat hindlimb muscle perfused with cell-free medium were performed at 35 and 15 degrees C under various oxygen supply, in the relation to the oxygen metabolism. Molar ratio of Cyt a + a3, Cyt b, Cyt c + c1, and Mb, oxygen affinity of Mb (P50), and the thermodynamic parameter (delta H degree) of Mb oxygenation in cyanide-perfused muscle were similar to those reported. The "apparent P50" of Mb in cyanide-free muscle was almost two orders larger in magnitude than P50 in the presence of cyanide. O2 uptake by the perfused hindlimb muscle was constant above O2 supply of 0.73 mumol/(min.g muscle) (under a flow rate of 1.0 ml/(min.g muscle) at 35 degrees C). Below the value of O2 supply, the O2 uptake decreased and lactate/pyruvate ratio increased. The critical mean oxygen tension in tissue (estimated by Mb oxygenation) for O2 uptake at 35 degrees C was ca. 10 mmHg. It was found that oxidation level (%) of Cyt a + a3 was equivalent to oxygenation level (%) of Mb at 35 degrees C, while the oxidation level of Cyt a + a3 was higher than the oxygenation level of Mb at 15 degrees C. Based on the results, the uneven distribution of O2 in the muscle tissue and the intracellular O2 gradient were discussed.

Animals↗
PubMed1991

Immunohistochemical localization of an inositol 1,4,5-trisphosphate receptor, P400, in neural tissue: studies in developing and adult mouse brain.

The immunohistochemical localization of P400/inositol 1,4,5-trisphosphate (InsP3) receptor protein was studied in developing and adult mouse brain by using monoclonal antibodies. The developmental expression pattern of P400/InsP3 receptor protein differed among different classes of neurons. It was first detected in the somata of immature Purkinje cells at embryonic day 17, in the ventrolateral region of the posterior vermis in the cerebellum. Axonal immunoreactivity within the cerebellar nuclei was first present at postnatal day 3. Neurons in the retrosplenial cortex, the anterior olfactory nucleus, and the CA1 region of the hippocampus expressed immunoreactivity earlier than other regions of the brain. In the adult brain, not only the Purkinje cell but also many other types of cells in many areas of the brain expressed P400/InsP3 receptor, though to a lesser extent. These included the neurons in the striatum, globus pallidus, nucleus accumbens septi, anterior olfactory nucleus, olfactory tubercle, precommissural hippocampus, hippocampus, substantia nigra, cerebral cortex, pons, and certain hypothalamic nuclei. Forebrain cortical regions that receive afferents from the olfactory bulb, such as the anterior olfactory nucleus, olfactory tubercle, prepiriform cortex, entorhinal cortex, and amygdala, exhibited distinct immunoreactivity, while olfactory bulb was almost devoid of staining. Immunoreactivity in the axonal pathways was also found in the limbic-hypothalamic pathways, strionigral projection, and part of the corpus callosum. Results of Western blot analysis and 3H-InsP3 binding assay were consistent with the qualitative regional differences of immunoreactivity demonstrated by immunohistochemical study. The location of InsP3 receptor in the brain correlates well with the InsP3 binding sites demonstrated by an autoradiographic study.

Animals↗
PubMed1991

Lectin-reactive patterns of markedly elevated serum alpha-fetoprotein in patients with chronic active hepatitis.

Four cases of chronic hepatitis associated with high serum levels of alpha-fetoprotein (AFP) without hepatocellular carcinoma are reported. All showed transient elevations of serum AFP, with peak levels of 13,500, 8,000, 4,450, and 3,000 ng/ml shortly after aggravation resulting from liver function tests. Liver biopsies revealed severe parenchymal damage in all the cases with piece-meal necrosis, bridging necrosis or bridging fibrosis. In two of four cases, there was a lobular distortion. AFP stain by an immunoperoxidase method showed a positive result in surviving hepatocytes. Lectin affinity electrophoresis of AFP in the four cases, together with an additional 12 patients with chronic hepatitis and cirrhosis and 44 patients with hepatocellular carcinoma, all having AFP levels above 1,000 ng/ml, revealed that the chronic hepatitis patients had a benign pattern of AFP bands, in contrast with the pattern of hepatocellular carcinoma with increased proportions of lentil lectin-reactive AFP-L3 and/or erythroagglutinating phytohemagglutinin-reactive AFP-P4, indicating that the analysis of lectin reactivity of AFP has a great value in differentiating the benign and malignant conditions with increased serum levels of AFP above 1,000 ng/ml.

Adult↗
PubMed1991

[Tissue plasminogen activator treatment of postvitrectomy pupillary fibrin membrane].

Twenty-five micrograms of human recombinant tissue plasminogen activator (tPA) was injected via the corneoscleral limbus of 14 postvitrectomy aphakic eyes with prominent pupillary fibrin membranes. Fibrinolysis by tPA was initiated by thirty minutes after the injection, and the fibrin membrane was completely dissolved within sixty minutes. No toxicity attributed to tPA was observed clinically. Intraocular fluid was obtained during fluid-gas exchange after complete dissolution of fibrin and analyzed for decomposed fibrin products (FDP). Intraocular FDP was significantly higher (160 +/- 250 micrograms/ml) than normal after tPA treatment. Intraocular tPA administration is a potent modality to treat postvitrectomy fibrin membrane. Fluid-gas exchange must be performed to eliminate as much FDP as possible to reduce postoperative inflammation.

Adolescent↗
PubMed1991

DNA polymorphisms in the controlling region of the human haptoglobin genes: a molecular explanation for the haptoglobin 2-1 modified phenotype.

A haptoglobin 2-1 modified (Hp2-1mod) phenotype results when the amount of Hp2 polypeptide synthesized in Hp2/Hp1 heterozygotes is less than that of Hp1 polypeptide. Cloned Hp2 DNA from an individual with the Hp2-1mod phenotype is here shown to have a C in place of the normal A at nucleotide position -61 in one of the interleukin-6 (IL-6) responsive elements of the haptoglobin promoter region. Direct sequencing of the haptoglobin promoter region, amplified by PCR, from DNA from unrelated American blacks showed a C at -61 in all of 10 individuals with the Hp2-1mod phenotype, in two of four with a "possible Hp2-1mod" phenotype, but in none of 15 with the Hp2-1 phenotype. Thus the -61C mutation in the Hp2-61C allele is strongly associated with the Hp2-1mod phenotype. Sequencing results also show that there are three other promoter sequences in the population studied; each can be associated with either Hp2 or Hp1. The variability seen in the Hp2-1mod phenotype, a variability which ranges from close to Hp2-1 to close to Hp1-1, can be explained, in part, by the existence of several Hp2 alleles differing in their promoters--and possibly, in part, by differences in the promoters of the accompanying Hp1 allele. A further part of the variability may be the consequence of differences in the way that the Hp2-61C and the Hp2 alleles respond to the IL-6-dependent factor during an acute-phase response.

Base Sequence↗
PubMed1990

Septohippocampal cholinergic pathway and penile erections induced by dopaminergic and cholinergic stimulants.

Penile erection was studied in rats injected with pilocarpine, amantadine and apomorphine. Pilocarpine and apomorphine are direct stimulants of muscarinic and dopaminergic receptors, respectively, while amantadine is reported to be an indirect stimulant of dopaminergic nerves. Single intraperitoneal injection of pilocarpine (0.1-3.2 mg/kg), amantadine (1-32 mg/kg) and apomorphine (0.01-1 mg/kg) increased the number of penile erections with bell-shaped dose-response curves. The penile erections, irrespective of the stimulant used, were antagonized by doses (0.032-1 mg/kg) of scopolamine but not by those of methylscopolamine. Sulpiride treatment (1-32 mg/kg) had little effect on pilocarpine-induced penile erection while it attenuated dose-dependently the apomorphine- and amantadine-induced ones. Medial septum and fimbria-fornix lesions abolished penile erections by amantadine and apomorphine but not by pilocarpine. The similar results with amantadine and apomorphine suggest that the drugs activate postsynaptic dopamine receptors, which indirectly activate the septohippocampal cholinergic pathway to induce penile erections. Possible linkage between dopaminergic and cholinergic nerves is discussed.

Amantadine↗
PubMed1990

Influence of 2,3-diphosphoglycerate on the deformability of human erythrocytes.

Effect of 2,3-diphosphoglycerate (2,3-DPG) on the deformability of human erythrocytes was examined with a rheoscope under shear stress of 8-82 dyn/cm2. With increasing 2,3-DPG in erythrocytes (from 5 to 15 mM/l cells) by incubating with inosine and pyruvate in isotonic 50 mM phosphate-buffered saline, erythrocyte deformability under uniform shear stress was remarkably impaired. But reduction of 2,3-DPG (from 5 to 2.2 mM/l cells) did not affect the deformability. In 2,3-DPG-enriched erythrocytes, increased intracellular hemoglobin concentration (MCHC), decreased intracellular pH, and increased contents of ATP and IMP (and ITP) were observed. (1) When the MCHC (i.e., the internal viscosity) was normalized by suspending in hypotonic medium, the deformability of 2,3-DPG-enriched erythrocytes was greatly improved, but still decreased. (2) The change of intracellular pH between 6.5 and 7.5 (as compared adjusting to same MCHC) did not alter the deformability. (3) The changes of purine nucleotides, ATP (0.6-2.1 mM/l cells), IMP (0-0.9 mM/l cells) and ITP (0-0.5 mM/l cells) did not alter the erythrocyte deformability. In conclusion, decreased deformability of erythrocytes induced by augmentation of 2,3-DPG is due mainly to the increased internal viscosity and due partly to the increased membrane viscoelasticity.

2,3-Diphosphoglycerate↗