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Biomedical subjects

N Akashi

Publications and source records attributed to N Akashi.

At least 19 recordsLinked to original sources
PubMed2003

Somatic embryogenesis and plant regeneration from immature zygotic embryos of Cryptomeria japonica D. Don.

This report describes the successful plant regeneration via somatic embryogenesis from immature zygotic embryos of Cryptomeria japonica D. Don. For the induction of embryogenic tissue, we determined that the optimal medium contained N6-benzyladenine and 2,4-dichlorophenoxyacetic acid. Immature zygotic embryos that were collected at the end of June yielded embryogenic tissue at the highest frequency. Embryogenic tissues that had proliferated in liquid medium included small and loosely packed cells and elongating or elongated cells. We used ten cell lines to determine the optimal medium for the development of somatic embryos. Induced somatic embryos germinated with synchronous sprouting of cotyledons, hypocotyls and roots. Gibberellin A3 in the germination medium had a positive effect on both the elongation of hypocotyls and the survival of seedlings. The frequencies of induction and germination of somatic embryos differed among the cell lines examined. Most of the seedlings grew normally. This system of somatic embryogenesis required 4-5 months for the regeneration of C. japonica plantlets from immature zygotic embryos.

Cryptomeria↗
PubMed2001

Localization of extracellular matrix receptors in ICGN mice, a strain of mice with hereditary nephrotic syndrome.

Fibrotic degeneration was examined in the kidneys of ICR-derived glomerulonephritis (ICGN) mice, a novel inbred mouse line with a hereditary nephrotic syndrome of unknown etiology considered to be a good model of human idiopathic nephrotic syndrome. In the present study, we histochemically revealed changes in accumulation of extracellular matrix (ECM) components and in localization of integrins, cellular receptors for ECM, in the kidneys of ICGN mice with the progression of renal failure. Excessive accumulation of basement membrane (laminin and collagen IV) and interstitial (type III collagen) ECM components were demonstrated in the glomeruli and tubulointerstitum of ICGN mice. Marked deposition of type I collagen and tenascin was seen only in the glomeruli of ICGN mice but not in those of ICR mice as normal controls. Increased expression of integrin alpha1-, alpha2-, alpha5- and beta1-subunits in glomeruli with fibrotic degeneration and abnormal distribution of alpha6-subunit were noted in the kidneys of ICGN mice. Excessive laminin, a ligand of alpha6beta1-integrin, was demonstrated on the tubular basement membrane, but alpha6-subunit diffusely disappeared on the basal side of the tubular epithelial cells. We presumed that abnormal integrin expression in renal tubules causes epithelial cell detachment, and consequently tubular nephropathy, and results in disorder of ECM metabolism causing excessive accumulation of ECM components in the kidneys of ICGN mice.

Albumins↗
PubMed2001

Changes in quantitative profile of extracellular matrix components in the kidneys of rats with adriamycin-induced nephropathy.

Extracellular matrix components (ECMs) in histological sections of the kidney cortex from the rats with adriamycin (ADR)-induced nephropathy (5 mg/kg, i.v.) were quantified by an immunohistochemical micromethod. Changes in kidney histopathology and urine and blood biochemistry were investigated. Enlarged kidneys were granular on the surface and pale in color in ADR-treated rats, and these rats had kidneys with glomeruli with expanded mesangial area and with capillary aneurysm. Severe albuminuria, hypoalbuminemia, hypercholesterolemia and disorders in other nephrotic parameters were observed in ADR-treated rats. Type I and IV collagens, fibronectin and laminin contents in the renal cortex of ADR-treated rats at 10 weeks were 329, 317, 263 and 295%, respectively, higher than in each vehicle control, and those at 28 weeks were 1,211, 930, 1,057 and 1,012%, respectively. The glomerular sclerotic abnormalities progressed in a time-dependent manner. Moreover, there was a strong correlation between the ECM levels and serum creatinine and blood urea nitrogen levels. In conclusion, microquantification provided useful information for accurate diagnosis and prognosis of nephrotic lesions and is a good tool to assess the advancement of renal disorders in patients with nephropathy.

Albuminuria↗
PubMed2001

Localization of proliferative and apoptotic cells in the kidneys of ICR-derived glomerulonephritis (ICGN) mice.

The ICR-derived glomerulonephritis (ICGN) mouse is a novel inbred mouse strain with a hereditary nephrotic syndrome, considered to be a good model of human idiopathic nephrotic syndrome and develops proteinuria, hypoproteinemia and anemia. In the present study, we compared the cell kinetics in the kidneys of ICGN mice with age-matched ICR mice as normal controls. The proliferating cells were visualized by 5-bromo-2'-deoxyuridine labeling, and apoptotic cells were determined by terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end-labeling. Many proliferating epithelial cells of renal tubules, glomerular mesangial cells and tublointerstitial fibroblast-like cells were observed in the kidneys of ICGN mice, but no proliferating cells were seen in the kidneys of ICR mice. Apoptotic cells had round nuclei, and were observed only in the tubulointerstitium in the kidneys of ICGN mice but not in that of controls. The proliferation of renal tubular epithelial cells may represent a compensatory response, and that of mesangial and fibroblast-like cells may play a pathogenic role in nephrotic syndrome. Apoptosis in tubulointerstitial cells with round nuclei may have been erythropoietin-producing cells, and probably caused anemia.

Animals↗
PubMed2000

Measurements of acoustic properties of aqueous dextran solutions in the VHF/UHF range.

The acoustic properties of aqueous solutions of dextran are characterized in the frequency range of 70-400 MHz by the bio-ultrasonic spectroscopy system using an ultrasonic transmission comparison method. The attenuation, velocity, impedance, and density of aqueous dextran solutions, for six molecular weights in the range of 10,400-2,000,000 Da in the concentration range 520% by weight, are reported. All four parameters increase with increasing concentration. As the molecular weight increases, the attenuation coefficient increases and the velocity decreases. The precise frequency and molecular weight dependences of the acoustic properties of the solutions are readily determined by the system.

Dextrans↗
PubMed1997

Acoustic properties of egg yolk and albumen in the frequency range 20-400 MHz.

The acoustic propagation properties of egg yolk and albumen are characterized in the frequency range 20-400 MHz by the bioultrasonic spectroscopy system using an ultrasonic transmission comparison method. Significant differences in the attenuation, velocity, impedance, and density among yolk and thick and outer thin albumen are observed. The acoustic properties of 10% aqueous solutions of ovalbumin and bovine hemoglobin are also measured in order to investigate the contribution of proteins to the acoustic properties of albumen. The differences obtained between thick and outer thin albumen may be mainly due to their macromolecular level structural differences, as their constituents are nearly the same.

Acoustics↗
PubMed1995

Severe mitochondrial cardiomyopathy and extra-neuromuscular abnormalities in mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode (MELAS).

An autopsy case of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) in a 56 yr-old woman is reported. Histopathologic abnormalities are shown widely in the heart, liver, kidney, pancreas and thyroid gland, other than the central nervous system and skeletal muscles that had been so far emphasized in the cases of MELAS. Particularly in the myocardium, focal fibrosis and a disarray of myofibrils were demonstrated, which closely resembled that seen in idiopathic hypertrophic cardiomyopathy. In addition, unique mitochondrial abnormality exhibiting a central glycogen aggregation with surrounding multiple radiating cristae was noted in some cardiomyocytes, which has never been reported in previous cases of MELAS. Thus, in MELAS, various histopathological abnormalities including the mitochondrial abnormalities may involve tissues other than those of the neuromuscular system.

Abnormalities, Multiple↗
PubMed1995

Acoustic properties of selected bovine tissues in the frequency range 20-200 MHz.

The acoustic properties of freshly excised bovine liver, heart muscle, and fat are characterized in the frequency range 20-200 MHz by the bioultrasonic spectroscopy system using an ultrasonic transmission comparison method. Significant differences are obtained in the attenuation coefficient, velocity, impedance, and density among these tissues. Measurements of aqueous solutions of bovine hemoglobin are also reported in order to compare the contribution of the protein content to the acoustic properties. The differences among the acoustic properties of liver and heart muscle can be described in terms of their protein contents and other molecular constituents.

Acoustics↗
PubMed1995

Disulfide bond formation and secretion of Escherichia coli heat-stable enterotoxin II.

The Escherichia coli heat-stable enterotoxin II (STII) is a typical extracellular toxin consisting of 48 amino acid residues, of which 4 are cysteine. There are two disulfide bonds, one between Cys-10 and Cys-48 and one between Cys-21 and Cys-36. We examined the involvement of DsbA in the formation of the disulfide bonds of STII and the role of each in the secretion of STII. A dsbA mutant was transformed with a plasmid harboring the STII gene, and STII was not detected either in the cells or in the culture supernatant. Reducing the level of STII brought about the dsbA mutation restored by introducing the wild-type dsbA gene into the mutant strain. These results showed that DsbA is involved in forming the disulfide bonds of STII and that STII without these disulfide bonds is degraded during secretion. We substituted these four cysteine residues in vivo by oligonucleotide-directed site-specific mutagenesis. The amino acid sequence of the purified STII (C48S) and pulse-chase studies revealed that two intermolecular disulfide bonds must be formed to be efficiently secreted and that cleavage between amino acid residues 14 and 15 is probably the first step in the proteolytic degradation of STII.

Bacterial Toxins↗
PubMed1994

Effect of alterations of basic amino acid residues of Escherichia coli heat-stable enterotoxin II on enterotoxicity.

Escherichia coli heat-stable enterotoxin II (STII) is composed of 48 amino acid residues. Among these, one histidine, two arginine, and six lysine residues are basic. Isoelectric focusing showed that the isoelectric point of STII is 9.7, indicating that the side chains of some of these basic amino acid residues project outside the molecule. To understand the role that these basic amino acid residues play in toxicity, STII was chemically modified with ethoxyformic anhydride, maleic anhydride, and phenylglyoxal, which alter the side chains of basic amino acid residues in proteins. Maleic anhydride, which modifies the epsilon amino group, caused a significant loss of enterotoxic activity, but the other two modifiers did not. This indicated that lysine residues play an important role in the expression of the enterotoxic activity of STII and that the contribution of the other basic amino acid residues to the toxicity is relatively low. To confirm this hypothesis, we substituted these nine basic amino acid residues by oligonucleotide-directed site-specific mutagenesis and examined the enterotoxicity of these purified mutant STIIs. The enterotoxic activity was reduced when the lysine residues at positions 18, 22, 23, and 46 were substituted. In particular, the substitution at positions 22 and 23 induced a remarkable reduction. These results demonstrate that the lysine residues at positions 22 and 23 are very important in the expression of the enterotoxic activity of STII.

Animals↗
PubMed1993

Production of heat-stable enterotoxin II by chicken clinical isolates of Escherichia coli.

Enterotoxigenic Escherichia coli isolated from diarrhea stools of chickens were examined for production of heat-stable enterotoxin II which is considered to be implicated only in diarrhea of pigs. Seven out of 38 strains examined were found to contain heat-stable enterotoxin II gene, determined by colony hybridization and the polymerase chain reaction. The culture supernatants of these strains caused fluid accumulation in the mouse intestinal loop test. This fluid accumulation activity was not lost by heating at 100 degrees C and was neutralized by anti-heat-stable enterotoxin II antiserum. Purified heat-stable enterotoxin II caused fluid accumulation in the chicken intestinal loop assay. These results indicate that STII-producing E. coli is implicated in chicken diarrhea.

Animals↗
PubMed1993

Identification and characterization of heat-stable enterotoxin II-producing Escherichia coli from patients with diarrhea.

Stock strains of Escherichia coli isolated from patients with traveller's diarrhea were examined for production of heat-stable enterotoxin II (STII). Of 400 strains examined, 3 were found to produce STII. The nucleotide sequence of the STII gene of these human strains was shown to be identical to that of porcine strains. Cultured cells of these strains induced fluid accumulation in ligated mouse intestinal loops and the activity was neutralized by anti-STII antiserum. These results suggest that STII-producing enterotoxigenic E. coli can cause human diarrhea.

Animals↗
PubMed1990

[Gore-Tex grafts for replacement of the superior vena cava in 10 patients with intrathoracic malignant tumors].

Ten patients with lung cancer and mediastinal tumor invading the mediastinal structures underwent replacement of superior vena cava (SVC) with ringed Gore-Tex to resect malignant tumors. In patients with lung cancer sleeve pneumonectomy (3 patients), sleeve lobectomy (1 patients) and tracheal resection (one patient) were performed simultaneously. By resection of the VCS system, invasive thymomas were able to be resected completely in 2 of 3 patients. In 2 patients with mediastinal tumors, one with metastatic testicular chorio carcinoma and one with malignant lymphoma of non-Hodgkin type, aggressive chemotherapy was followed by resection of the residual tumors including VCS. Except for one patient, there was no sign showing disturbance of the venous return in the VCS system in the 5 to 43 months' postoperative follow up period. We conclude that ringed Gore-Tex graft permits the extended operation for intrathoracic malignancies invading the mediastinal structures.

Adenocarcinoma↗
PubMed1989

[Arrhythmia in patients with cerebral infarction evaluated by Holter ECG].

In the present study, Holter ECG (24 hours continuous monitoring) was applied for detection of arrhythmia in patients with cerebral infarction to elucidate the relationship between arrhythmias and types of cerebral infarction. The subjects were 111 patients (80 males and 31 females) with cerebral infarction who were admitted to our institution during the acute stage. Their average age was 65.4 years old. They were divided into the following three groups: Group L; patients having a large low density area on CT including the cortex, group S; those having a small low density area in the basal ganglia, and group N; those having no low density area on CT. Holter ECG was taken at least three weeks after onset in all cases. Fourteen of them were also examined in the acute stage, and these findings were compared with those taken in the chronic stage. Three Holter ECGs recorded incidentally before the onset of stroke were used for comparison. Based on the basic rhythms recorded on the Holter ECG, the subjects were divided into sinus rhythm and atrial fibrillation cases. The total number of ventricular premature contractions (VPCs), were determined in each case. There was little difference in the number of total VPCs among the records taken in the pre-onset, acute and chronic stages. There also was no relation between the total number of VPCs and the age, history of hypertension, and the site of infarction on CT. There was no consistent relationship between the total number of VPCs in cases with atrial fibrillation and CT findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗