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Biomedical subjects

H Iwamoto

Publications and source records attributed to H Iwamoto.

At least 217 records · Page 12Linked to original sources
PubMed1989

Incidence and prognosis of subarachnoid hemorrhage in a Japanese rural community.

Twenty-six first episodes of subarachnoid hemorrhage occurred among 1,621 Hisayama residents aged greater than or equal to 40 years during the 22-year follow-up of a prospective study. Subarachnoid hemorrhage was confirmed by both clinical and autopsy findings. The average annual incidence (96.1/100,000 population) was 3-13 times higher than any previously reported and steeply increased with age in both sexes, being 2.3 times higher for women than for men after adjusting for age. Nine patients (35%) died less than or equal to 8 hours after the onset of subarachnoid hemorrhage. None was correctly diagnosed on the death certificates, and four of the nine (44%) were misdiagnosed as intracerebral hemorrhage. We found the survival rate of patients suffering subarachnoid hemorrhage to be much lower than previously reported because we detected a large number of sudden deaths due to subarachnoid hemorrhage through the high rate of autopsy in our cohort (81.4%).

Adult↗
PubMed1989

[A patient with alternating hemiplegia in childhood].

Alternating hemiplegia in childhood (Verret, 1971) is a disorder presenting with frequent episodes of alternating hemiplegia from early infancy. We report a patient with this disorder, along with a pathophysiological study and a discussion about the available therapies for this disorder. The patient, an 11-year-old boy, visited our hospital with episodes of alternating hemiplegia from early infancy. His family history showed that many members suffered from migraine. He was born with asphyxia. Mental and motor developmental delays were seen from early infancy. The hemiplegic episodes with ipsilateral facial palsy had occurred frequently from early infancy. The episodes were frequently induced by emotional stress. The duration of hemiplegia varied from 10 minutes to 3 days. From the age of 11 years, he had begun to have migrainous attacks with or without hemiplegic episodes. Neurological examination revealed slight muscle hypotonia, choreoathetosis and dystonic movements induced by locomotion, positive Myerson sign, increased deep tendon reflexes and Babinski reflex. CAG, VAG and CAT revealed normal findings. EEG revealed diffuse generalized slowing during hemiplegic episodes. Measurement of regional cerebral blood flow (CBF) by 133Xe inhalation method revealed a slight decrease of bilateral CBF during a quadriplegic episode. Positron emission tomography using C15O2 revealed a slight decrease of CBF at the insula, putamen and claustrum of the left side during a right sided episode. Increased excretion of urinary 5-HIAA was seen during one episode. From our clinical and laboratory findings, we think this disorder may be a special type of migraine. Therapeutic trials of diazepam and flunarizine were both effective, but the initial effectiveness was decreased after 5 months.

Age Factors↗
PubMed1989

[Cerebellar ataxia of early onset: clinical symptoms and MRI findings].

Eight cases of childhood cerebellar ataxia were reported. All these cases showed chronic cerebellar ataxia with early onset, and the other diseases of cerebellum such as infections, neoplasms and storage diseases were excluded by clinical symptoms and laboratory findings including blood counts, blood chemistry, lactate, pyruvate, ceruloplasmin, urinalysis, serum immunoglobulins, amino acid analysis in blood and urine, CSF analysis, leukocyte lysosomal enzymes, MCV, EMG, EEG and brain X-CT. Two pairs of siblings were included in this study. The clinical diagnosis were cerebellar type (5), spinocerebellar type (1), one Marinesco-Sjögren syndrome and undetermined type (1). The age of onset was 1 to 5 years. The chief complaint was motor developmental delay in 6 cases; among them 5 patients could walk alone at the ages of 2 to 3 years'. Mental retardation was observed in 7 cases and epilepsy in 2. TRH was effective in 5 cases. The MRI study revealed that the area of medial sagittal slice of the cerebellum was reduced significantly in all cases and also that of pons was reduced in 5 cases. Different from typical adult onset spinocerebellar degenerations, most of the present cases have achieved slow developmental milestones and the clinical course was not progressive. Genetic factors are suspected in the pathogenesis of this disease in some cases.

Adolescent↗
PubMed1988

Regulatory mechanism of contraction in the proboscis retractor muscle of a sipunculid worm, Phascolosoma scolops.

Regulatory mechanism of contraction in the proboscis retractor muscle of Phascolosoma scolops was studied by physiological measurements and cytochemical electron microscopy. The magnitude of K+-contracture was dependent on external Ca2+ concentration and the contracture disappeared in Ca2+-free solution. The K+-contracture was suppressed by application of procaine and Mn2+. Caffeine induced contracture even when external Ca2+ was absent. Ultrastructural observations of the retractor muscle cells showed the presence of a large number of vesicles (subsarcolemmal vesicles), corresponding to the sarcoplasmic reticulum in vertebrate skeletal muscle, underneath the plasma membrane. For the cytochemical electron microscopy, the muscle fibers were fixed with 1% OsO4 solution containing 2% K-pyroantimonate. In the relaxed fibers, pyroantimonate precipitates were localized along the inner surface of plasma membrane and in the subsarcolemmal vesicles. In the contracting fibers, the precipitates were uniformly distributed in the myoplasm. The X-ray microanalysis revealed that the precipitates contained Ca. These results suggest that the contractile system is activated by the influx of extracellular Ca2+ as well as by the release of Ca2+ from the intracellular structures such as the inner surface of the plasma membrane and subsarcolemmal vesicles.

Acetylcholine↗
PubMed1988

Subunit structures of three human myeloperoxidases.

The heavy and the light subunits of human myeloperoxidase (donor: H2O2 oxidoreductase [EC 1.11.1.7]) I, II, and III were isolated from the reduced and S-carboxymethylated enzymes. These three enzymes have the same terminal amino acid sequences and similar chemical compositions in both subunits. The NH2-terminal sequences of the heavy and light subunits were determined to be Val-Asn-Cys-Glu-Thr- and Thr-Cys-Pro-Glu-Gln-, respectively; a heterogeneity was observed in the NH2-termini of the latter subunits for the three enzymes. As for COOH-termini, the sequences -(Asn, 2 Leu, Ala, Ser, Trp)-Arg-Glu-Ala and -Ala-Arg were obtained for the heavy and the light subunits, respectively. The heavy subunits contained 8-10 mol/mol of glucosamine. On the basis of these results and the amino acid sequence deduced from cDNA clones, the heavy subunits probably correspond to amino acids 279-744 and the light subunits to amino acids (164-167)-272. For the heavy subunits, Ser-745, which was predicted as the COOH-terminal amino acid from the nucleotide sequence, was removed. The light subunits were also processed at their COOH-termini by 6 residues. Four or five high mannose type carbohydrate chains were attached to the heavy subunits.

Amino Acid Sequence↗
PubMed1988

Purification, crystallization, and characterization of peroxidase from Coprinus cinereus.

Peroxidase (donor: H2O2 oxidoreductase [EC 1.11.1.7]) was purified from a culture broth of an inkcap Basidiomycete, Coprinus cinereus S.F. Gray. A single component containing a low amount of carbohydrate was isolated by affinity chromatography on concanavalin A-Sepharose and crystallized from ammonium sulfate solution. The enzyme is an acidic protein (pI 3.5) and consists of a single polypeptide chain having the molecular weight of 41,600 daltons. The enzyme contains one protohemin per molecule and exhibits the characteristic absorption, circular dichroism, and magnetic circular dichroism spectra of a heme-protein. The Coprinus peroxidase forms two characteristic intermediate compounds, I and II, and the rate constants for hydrogen peroxide and guaiacol had similar values to those for higher plant peroxidases. The ferric enzyme formed a cyanide compound with a dissociation constant similar to those for higher plant enzyme, but the dissociation constant of the ferrous enzyme-cyanide was large. The chemical composition of Coprinus peroxidase showed 381 amino acid residues, 1 glucosamine, 3 true sugars, 3 calcium, and 1 non-heme iron other than 1 protohemin. The secondary structure of the fungal enzyme was very similar to that of horseradish peroxidase.

Agaricales↗
PubMed1988

Cardiac rhabdomyoma. A case report with reference to atrial natriuretic peptide.

An autopsy case of cardiac rhabdomyoma in a male infant is reported. Many nodules of rhabdomyoma were present in all four cardiac chambers and were microscopically composed of ovoid, glycogen-laden cells and typical "spider cells". Atrial natriuretic peptide (ANP) was immunohistochemically demonstrated in both normal myocytes and rhabdomyoma cells of both atria, but not in normal myocytes and rhabdomyoma cells of both ventricles. Ultrastructurally, atrial specific granules were present in atrial rhabdomyoma cells and normal atrial cardiocytes, and these showed ANP immunoreactivity with protein A-gold technique. It could be said that the localization and intracellular distribution of ANP in this cardiac rhabdomyoma were closely similar to those of normal human heart. With regard to the presence of ANP, cardiac rhabdomyoma cells arising in atria seemed to differ from those in ventricles, although many tumor nodules occurred in both atria and ventricles. Furthermore, it seemed that cardiac rhabdomyomas could also be divided into two parts: 1) an atrial part with ANP, and 2) a ventricular part without ANP. Therefore, this study confirms the hypothesis that cardiac rhabdomyoma is a hamartoma rather than a true neoplasm.

Atrial Natriuretic Factor↗
PubMed1988

Time-resolved X-ray diffraction studies on the effect of slow length changes on tetanized frog skeletal muscle.

1. The mechanism of the enhancement and the deficit of isometric force by slow length changes in frog skeletal muscle was studied with the time-resolved X-ray diffraction technique, using intense X-rays of synchrotron radiation. 2. When a tetanized muscle was slowly stretched by 4% from sarcomere lengths 2.3-2.4 microns, the force rose to a peak during stretch and then decreased to a steady level 10-15% higher than that immediately before stretch. 3. The intensity of the 1,1 equatorial reflection decreased nearly linearly during stretch and then again increased after the completion of stretch, reaching a steady level 12 +/- 5% (mean +/- S.D., n = 11) lower than that immediately before stretch. The above 1,1 intensity change was roughly a mirror image of the force change. 4. The intensity of the 1,0 equatorial reflection showed no marked changes in response to a slow stretch, except for an initial transient increase observed occasionally. 5. If a tetanized muscle was slowly released by 4% from sarcomere lengths 2.3-2.4 microns, the steady force attained after the completion of release was lower than that immediately before release. 6. The 1,1 intensity increased slightly during release, while the 1,0 intensity did not change significantly. 7. The half-width of both the 1,0 and the 1,1 reflections did not change appreciably in response to slow length changes. 8. Slow length changes always produced changes in the spacing between the reflections as expected from the constant-volume behaviour of the myofilament lattice. 9. These results indicate that a slow stretch produces disordering of the myofilament lattice in such a way that the thin filaments are displaced from trigonal positions in the thick filament lattice. The resulting increase in the overall repulsion forces between the filaments may lead to the enhanced isometric force after stretch.

Actin Cytoskeleton↗
PubMed1988

Economic force maintenance in a phasic smooth muscle of mollusca.

The time course of the ability of active shortening was compared to that of isometric contractile force during contraction-relaxation cycles of the pedal retractor muscle of Mytilus by measuring the maximal shortening velocity and the rate of force redevelopment after a quick release. The contractile force had its peak at 2 s after stimulus initiation and decayed with a half relaxation time of 8.3 s at 10 degrees C. At 6 s after stimulus initiation, both the maximal velocity of shortening and the rate of force redevelopment had decreased to 30% or less of the initial values, while 70% of peak force was retained. The results suggest a mechanism of economic force maintenance with a reduced rate of crossbridge cycling.

Animals↗
PubMed1988

A self-induced translation model of myosin head motion along thin filament in muscle contraction.

Evidence has been accumulating that muscle contraction may not be associated with the power stroke of the cross-bridges tightly coupled with ATP hydrolysis cycle. We have constructed a new contraction model which includes a number of basic properties of contraction processes not taken into consideration in the models hitherto reported. The basic assumption is that, when one head of a myosin molecule attaches to an actin monomer on thin filament, conformational changes take place in the neighbouring actin monomers to result in their non-symmetrical charge distribution to exert electrostatic force on the unattached head of the same myosin molecule in one direction. Thus, the unattached head moves along thin filament to attach to another actin monomer, while the already attached head detaches from thin filament. These steps are repeated to cause muscle contraction. The above contraction model can explain the results of our X-ray diffraction experiments as well as the results reported by other authors.

Actin Cytoskeleton↗
PubMed1987

Hyponatremia in small cell lung cancer. Mechanisms not involving inappropriate ADH secretion.

A 62-year-old man with small cell carcinoma (oat cell type) of the lung who had hyponatremia and renal sodium loss with inappropriate antidiuresis is reported. Plasma levels of arginine vasopressin (AVP) were not elevated inappropriately. Plasma levels of atrial natriuretic peptide (ANP), however, were high, and increased after water loading and hypertonic saline infusion. The renin-aldosterone axis was normal, as were adrenal, thyroid, and renal functions. Water restriction to 500 to 700 ml/d resulted in a rise in serum sodium. Analysis of the tumor tissue failed to demonstrate the presence of AVP or ANP. The findings (1) suggest that hyponatremia and renal sodium loss with inappropriate antidiuresis observed in the patient is due to an antidiuretic substance distinct from AVP, and (2) point to the possibility that hypersecretion of ANP may play a role in the pathophysiology.

Arginine Vasopressin↗