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Biomedical subjects

K Mikami

Publications and source records attributed to K Mikami.

At least 19 recordsLinked to original sources
PubMed1992

Behavior of germinal micronuclei under control of the somatic macronucleus during conjugation in Paramecium caudatum.

In conjugating pairs of Paramecium caudatum, the micronuclear events occur synchronously in both members of the pair. To find out whether micronuclear behavior is controlled by the somatic macronucleus or by the germinal micronucleus, and whether or not synchronization of micronuclear behavior is due to intercellular communication between conjugating cells, the behavior of the micronucleus was examined after removal of the macronuclei from either or both cells of a mating pair at various stages of conjugation. When macronuclei were removed from both cells of a pair, micronuclear development was arrested 1 to 1.5 hr after macronuclear removal. When the macronucleus of a micronucleate cell mating with an amicronucleate cell was removed later than 3 to 3.5 hr of conjugation, that is, an early stage of meiotic prophase of the micronucleus, micronuclear events occurred normally in the operated cell. These results suggest that most micronuclear events are under the control of the macronucleus and that the gene products provided by the macronucleus are transferable between mating cells. One such product is required for induction of micronuclear division and is provided just before metaphase of the first meiotic division of the micronucleus. This factor is effective at a lower concentration in the cytoplasm and/or is more transferable between mating cells than the factors required for other stages. This factor, which seems to be present at least until the stage of micronuclear disintegration, is able to induce repeated micronuclear division as long as it remains active. The factor can act on a micronucleus which has not passed through a meiotic prophase. Moreover, the results suggest the existence of a second factor which is provided by the macronucleus after the first meiotic division that inhibits further micronuclear division.

Animals↗
PubMed1992

[Three cases of surgical treatment of dumbbell neurogenic tumor of the mediastinum--evaluation of intraspinal extension in cases without clinical symptoms].

Three cases of dumbbell neurogenic tumor of the posterior mediastinum are reported. None of these cases had any clinical symptoms, and an abnormal mass shadow of the mediastinum had been detected on routine chest roentgenogram. In these three cases, however, myelogram and/or CT findings were suggestive of tumor extension to the spinal canal in various degrees. Two tumors were resected in two-stage operations with combined thoracic and neurosurgical approaches, and the other case was treated by one-stage operation with the combined two approaches. All tumors were completely resectable without serious complications such as hemorrhage, leakage of spinal fluid, or neurologic deficit. Even in asymptomatic patients with neurogenic tumor located in the paravertebral region, it should be determined whether or not the tumor extends to the spinal canal through the intervertebral foramen, prior to planning the surgical procedure.

Adult↗
PubMed1992

[Short-duration bladder instillation therapy with pirarubicin for superficial bladder tumor based on pharmacodynamic study].

From our experimental study, an instillation of THP for 5 minutes was attempted in 23 patients with superficial bladder tumors. THP (30 mg dissolved in 50 ml of distilled water) was instilled into the bladder 6 times every 48 hours. Of 23 patients, 9 (39%) showed complete disappearance of the bladder tumors, while partial disappearance (more than 50% tumor reduction) was observed in 3 cases (13%). Therefore the overall response rate was 52%. Neither urinary frequency nor hematuria was observed in all the cases, while painful urination was observed in 3 cases (13%). This newly designed bladder instillation therapy was effective against superficial bladder tumors with low incidence of local side effects.

Administration, Intravesical↗
PubMed1991

HBP-1a and HBP-1b: leucine zipper-type transcription factors of wheat.

Wheat transcription factors HBP-1a and HBP-1b bind to the hexamer motif, ACGTCA, of wheat histone gene promoters. HBP-1b also binds to the hexamer motif in the promoter of the 35S RNA gene of cauliflower mosaic virus, whereas HBP-1a does not. A cDNA clone encoding HBP-1b was isolated on the basis of its binding specificity to the hexamer motif. The deduced amino acid sequence indicates that HBP-1b, like HBP-1a, belongs to a leucine zipper class of transcription factors. Mutational analyses of the HBP-1a and -1b encoded cDNAs revealed that truncated polypeptides containing the leucine zipper and basic regions are sufficient for DNA binding. HBP-1a and -1b form homodimers, as expected from earlier studies on this class of transcription factors, but did not form heterodimers. Although the hexamer motif or its homologs exist in several plant genes, HBP-1a and -1b exhibited the highest binding affinity to the hexamer motif in the histone promoters, suggesting that both DNA binding proteins are involved in transcriptional regulation of wheat histone genes.

Amino Acid Sequence↗
PubMed1990

A possible model of hemoprotein-fatty acid peroxide complex demonstrated by electron spin resonance.

Coordination reaction between linolenic-acid-hydroperoxide (LHPO) and chloro(5, 10, 15, 20-tetraphenyl)-porphyrinato iron (III), Fe(III)TPPCl, was investigated by means of ESR. ESR spectra of the ferric low-spin complex (g1 = 2.336, g2 = 2.174 and g3 = 1.929) was recorded for the mixture prepared by mixing Fe(III)TPPCl and LHPO at -78 degrees C in the presence of alkaline reagent. ESR line width of complex was broadened when 17O2 labeled LHPO was used for ESR measurement. In terms of the g-parameters of the ferric low-spin species, this complex was concluded to be Fe(III)TPP(-OCH3)(-OO-linolenic acid) type complex.

Electron Spin Resonance Spectroscopy↗
PubMed1990

Acute effects of ethanol on cultured myocardial cells: an ultrastructural study.

Myocardial cells in monolayer culture were examined ultrastructurally at various times (5 min-24 hr) after addition of ethanol (12.5-500 mM). At 5 min, all concentrations of ethanol induced mitochondrial fusion and a remarkable increase in glycogen granules, and the mitochondrial outer membrane seemed more fragile. These initial ultrastructural changes then recovered with time. Glycogen granules were decreased, then returned to normal more rapidly as the ethanol concentration was increased. Mitochondrial fusion and fragile appearance of the outer membrane were hardly seen at 1 hr in the presence of 12.5 or 50 mM ethanol, but were still evident with higher ethanol concentrations (200 and 500 mM), though less frequently than at 5 and 30 min. Furthermore, 'giant mitochondria' (with at least a five-fold increase in sectional area) appeared in the presence of 200 and 500 mM ethanol with increasing time of exposure. These results are discussed in relation to the direct effects of ethanol.

Animals↗
PubMed1990

Possible site of action of 5-hydroperoxyeicosatetraenoic acid derived from arachidonic acid in ACTH-stimulated steroidogenesis in rat adrenal glands.

The site of action of 5-hydroperoxyeicosatetraenoic acid (5-HPETE) in ACTH-induced stimulation of steroidogenesis was examined in rat adrenocortical fasciculata cells. Prior addition of AA861, a specific inhibitor of 5-lipoxygenase, had no significant effect on cyclic AMP-dependent protein kinase activity and cholesterol esterase activities, when stimulated by ACTH in adrenocortical cells, compared with that stimulated by ACTH alone. Cholesterol accumulation in the mitochondria of cells treated with ACTH and cycloheximide was also not altered by pretreatment with AA861. We found, however, that pregnenolone formation, stimulated by ACTH, decreased in a dose-dependent manner when cells were pretreated with AA861. The inhibition of ACTH-stimulated pregnenolone formation by treatment with AA861 was restored only by prior addition of 5-HPETE. Furthermore, addition of AA861 also did not affect the conversion of pregnenolone into corticosterone. In conclusion, 5-HPETE may act at the level of the mitochondria in ACTH-induced steroidogenesis in rat adrenal fasciculata cells.

Adrenal Cortex↗
PubMed1989

Wheat nuclear protein HBP-1 binds to the hexameric sequence in the promoter of various plant genes.

HBP-1 is a sequence-specific DNA-binding protein that interacts with the hexameric sequence ACGTCA, the putative cis-acting element of the wheat histone H3 gene. Gel mobility shift and DNase I footprint analyses showed that this protein interacts with homologous sequences in the regulatory regions for the transcription of the cauliflower mosaic virus (CaMV) 35S RNA and nopaline synthase (NOS) genes, evidence that HBP-1 may bind to hexameric sequences in the regulatory regions of various genes. An HBP-1-like protein, indistinguishable from wheat HBP-1 in its the DNA-binding specificity, is present in sunflower nuclear extract, an indication that HBP-1-like DNA-binding proteins also exist in dicots.

Amino Acid Oxidoreductases↗
PubMed1989

Multiplicity of the DNA-binding protein HBP-1 specific to the conserved hexameric sequence ACGTCA in various plant gene promoters.

A novel DNA-binding protein that specifically interacts with the hexameric sequence ACGTCA in the regulatory region of the wheat histone H3 gene has been identified in wheat nuclear extract and designated HBP-1a. The nuclear protein HBP-1 previously identified as a DNA-binding protein that interacts with hexameric sequences in the H3, cauliflower mosaic virus (CaMV) 35 S RNA, and nopaline synthase (NOS) promoter regions therefore has been renamed HBP-1b. The flanking sequences that surround the hexameric sequence may account for the difference in the binding properties of HBP-1a and HBP-1b.

Binding, Competitive↗
PubMed1989

A protein that binds to a cis-acting element of wheat histone genes has a leucine zipper motif.

The structure and function of transcription factors of higher plants was studied by isolating cDNA clones encoding a wheat sequence-specific DNA binding protein. A hexameric nucleotide motif, ACGTCA, is located upstream from the TATA box of several plant histone genes. It has been suggested that this motif is essential for efficient transcription of the wheat histone H3 gene. A wheat nuclear protein, HBP-1 (histone DNA binding protein-1), which specifically binds to the hexameric motif, has previously been identified as a putative transcription factor. A cDNA clone encoding HBP-1 has been isolated on the basis of specific binding of HBP-1 to the hexameric motif. The deduced amino acid sequence indicates that HBP-1 contains the leucine zipper motif, which represents a characteristic property of several eukaryotic transcription factors.

Amino Acid Sequence↗
PubMed1989

[Five cases of rectal cancer showing remarkable response to suppository administration of tegafur].

Five cases of rectal cancer, one male and 4 females, were preoperatively treated with Tegafur suppositories at 1,500 mg per day, for 8 to 21 days (mean, 14 days). These tumors were 2 early cancers and 3 advanced cancers, the configuration of which were one IIa type, one IIa + IIc type and 3 Borrmann 2 types. Their size ranged from 1.3 to 4.2 cm in diameter. Curative resections were performed in all cases, and the examination of the resected specimen revealed marked effects of Tegafur as follows: 1) Reduction of tumor size, 2) disappearance of cancer wall, 3) degeneration of cancer cells and destruction of cancer glands accompanied by fibrous stroma with infiltration of lymphocytes and plasma cells, 4) formation of xanthogranulomatous tissue with foamy histiocytes, which were characteristic findings showing that cancer tissue had been present there. As a result, rectal cancer clearly showed remarkable response to suppository administration of Tegafur for only about two weeks, if the tumor cells were sensitive to the drug.

Adult↗
PubMed1989

[A case of the successful surgical treatment of mediastinal giant neurogenic tumor, and the chest wall reconstruction by the autologous ribs].

A mediastinal tumor, particularly a neurogenic tumor, sometimes develops into a giant tumor; this large tumor mass then puts pressure on the heart and lungs, and may cause severe complications. In our department, 164 mediastinal tumors were experienced, the largest one was an intrathoracic fibromyoma which weighed 3,760 g. This report deals with our recent experience in which we found a neurogenic tumor weighed out 4,500 g. This tumor was excised in an emergency operation, after which the patient's life was saved by twenty-two days of artificial respiration. Since this tumor was so large, four entire right ribs had to be removed in order to create enough space to excise it. In order to reconstruct the chest wall, three of the removed ribs were retransplanted in their original sites. An extremely good prognosis resulted.

Adult↗