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K Ijiri

Publications and source records attributed to K Ijiri.

71 records · Page 4Linked to original sources
PubMed1985

The production of cloned fish in the medaka (Oryzias latipes).

The measurement of cellular DNA content by DNA microfluorometry revealed that medaka embryos that were fertilized with normal sperm and exposed to heat shock (41 degrees C for 3 min) or hydrostatic pressure (700 kg/cm2 for 10 min) at 85-95 min after insemination were tetraploid. Embryos fertilized with normal sperm and exposed to heat shock (41 degrees C for 2 min at 2-3 min after insemination) were triploid. These results suggest that heat shock or hydrostatic pressure at 85-95 min after insemination arrests the first cleavage, while heat shock at 2-3 min after insemination arrests the second meiotic division. Medaka clones have been produced by the following method: Eggs from orange-red or variegated variety were activated by UV-irradiated, genetically impotent sperm of wild-type fish (UV sperm). The haploid eggs obtained were diploidized by preventing the first cleavage with heat shock or hydrostatic pressure to produce homozygous females. Each of the two homozygous females was mated with vasectomized male in isotonic balanced salt solution to collect unfertilized eggs. The collected eggs were activated with UV sperm and converted from haploid to diploid by arrest of the second meiotic division with heat shock. Hatched fry of each homozygous diploid (all females) were fed with a methyltestosterone-containing diet (40 micrograms/gm diet) to produce sex-reversed males, which were mated with brood females, and thus two cloned lines were obtained.

Animals↗
PubMed1984

The recruitability and cell-cycle state of intestinal stem cells.

Evidence is presented which suggests that the crypts of the small intestine contain at least two discrete but interdependent classes of stem cells, some with discrete cell kinetic properties and some with discrete radiation responses or radiosensitivities. Very low doses of X rays or gamma rays, or neutrons, kill a few cells in the stem cell regions of the crypt in a sensitive dose-dependent manner. Similar doses generate several different cell kinetic responses within either the clonogenic fraction or the cells at the stem cell position within the crypt. The cell kinetic responses range from apparent recruitment of G0 clonogenic cells into cycle, to a marked shortening of the average cell cycle of the cells at the stem cell position. It is suggested that the cell kinetic changes may be the consequence of the cell destruction.

Animals↗
PubMed1984

The re-establishment of hypersensitive cells in the crypts of irradiated mouse intestine.

Within 3-6 h of small doses of radiation (gamma-rays) the number of dead cells (apoptotic cells) in the crypts of the small intestine reaches peak values. These return to normal levels only after times later than 1 day. After higher doses elevated levels of cell death persist for longer times. The dead cells first occur most frequently at the lower positions of the crypt (median value for the distribution of apoptotic fragments is about cell position 6). At later times more dead cells are observed at higher positions. Two doses of radiation separated by various time intervals have been used to investigate when after irradiation the cell population susceptible to acute cell death is re-established. Dead cells were scored 3 or 6 h after the second dose. The yield of dead cells after two doses represents the sum of the dead cells produced by, and persisting from, the first dose and new apoptotic cells induced by the second dose. Since the temporal and dose-dependence aspects of the dead-cell yield after the first dose alone is known, the additional dead cells attributable to the second dose alone can be determined by subtraction. Within 1-2 days of small doses (0.5 Gy) the sensitive cells, recognized histologically as apoptotic cells, are re-established at the base of the crypt (around cell position 6). After higher doses (9.0 Gy) they are not re-established until about the fourth day after irradiation. Even in the enlarged regenerating crypts the sensitive cells are found at the same position at the crypt base. It has been estimated that the crypt contains five or six cells that are susceptible to low doses (0.5 Gy) (hypersensitive cells) and up to a total of only seven or eight susceptible cells that can be induced by any dose to enter the sequence of changes implicit in apoptosis. Between 4 and 10 days after an initial irradiation of 9.0 Gy the total number of susceptible cells increased from seven to eight to about 10 to 13 per crypt.

Animals↗
PubMed1983

Response of intestinal cells of differing topographical and hierarchical status to ten cytotoxic drugs and five sources of radiation.

The spacial distribution of cell death among the epithelial cells lining the adult mammalian small intestinal mucosa at various times after a range of doses of 10 different drugs as well as after internal or external irradiation (beta particles from tritium, gamma- and X-rays and neutrons) has been recorded. Cell death, expressed as pycnosis or apoptosis, has been recorded for each cell position up the side of the crypts of the small intestine. The results, in the form of distributions of dead cells at each cell position, show that each of the various cytotoxic agents tends to act preferentially over a characteristic small range of cell positions. Since cell position is likely to be related to hierarchical cell position within a family tree or cell lineage, each agent tends to act with greatest efficiency on cells at a particular position within the lineage. Adriamycin and the various forms of radiation tend to kill cells preferentially at cell position 4-5 i.e. on cells very early in the lineage, probably stem cells. Isopropyl-methane-sulphonate, nitrogen mustard and possibly Actinomycin-D act on cell position 6-7, while 5-fluorouracil, Myleran, cyclophosphamide, and cycloheximide tend to kill cells at cell position 7-9. Vincristine and hydroxyurea are the 2 agents that exhibit a specificity for cells highest up the crypt, i.e. latest in transit population of the cell lineage by acting on cell positions 10 or 11. The data also suggest that normal healthy cells continue to migrate up the crypt and onto the villus in spite of considerable cell death and reduced cell production.

Animals↗
PubMed1980

Hertwig effect caused by UV-irradiation of sperm of Oryzias latipes (teleost) and its photoreactivation.

When sperm of the fish Oryzias latipes were irradiated with ultraviolet light and allowed to fertilize normal eggs, the so-called "Hertwig effect" was observed, with a dose-dependent decrease in survival rate at low doses (0-27 J . m-2) but a better survival rate at higher dose ranges. Illumination with visible light after fertilization (10-70 min after insemination) showed the existence of photoreactivation (PR), demonstrating that pyrimidine dimers are a lesion in sperm DNA that is mainly responsible for the UV-caused Hertwig effect. Genetic analysis, in which sperm from a wild-type of this fish was used, showed that, after UV-irradiation at the high dose range, male nuclei did not participate in embryonic development (a gynogenetic haploid condition). Embryos having only a maternal set of chromosomes could develop no further than stage 27. Only the visible light during the early part (until around 20-30 min after insemination, at 25 degrees C) of the single-cell stage was effective for PR; illumination thereafter was not.

Animals↗
PubMedDate not supplied

Changes with respect to time in the in vivo adsorption of plasma proteins onto artificial heart blood pumps.

The distribution of adsorbed plasma proteins (albumin, IgG, and fibrinogen) on 10 artificial heart blood pumps coated with 2 segmented polyurethanes was evaluated quantitatively after long-term in vivo experiments with goats to determine how the adsorption of plasma proteins on the pumps was affected by the kinds of biomaterials used, and by the pumping duration. The adsorbed plasma proteins on the materials were determined quantitatively using the iodine-125 conjugated antibody method. Microscopically, the adsorbed plasma proteins were marked by the gold colloid conjugated antibody method, and analyzed using a field emission scanning electron microscope. The macroscopic results showed that: 1) the adsorbed plasma proteins on KP-13 were more evenly and finely distributed than those on Cardiothane; 2) with KP-13, the adsorption of IgG and albumin at the center of the pumps was significantly less than in the peripheral areas, and the adsorbed IgG and albumin decreased significantly as the pumping duration increased; 3) in contrast, the adsorbed fibrinogen increased significantly with time; and 4) with Cardiothane, the tendencies for adsorbed IgG and albumin to decrease, and for adsorbed fibrinogen to increase, were less significant than with KP-13. Microscopically, the gold colloids marking plasma proteins were found to not cover the whole of the surface, but were found scattered randomly or in clusters, with no relationship observed between the distributions of the three plasma proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMedDate not supplied

LY309887, antifolate via the folate receptor suppresses murine type II collagen-induced arthritis.

OBJECTIVE: To examine the effect of LY309887, an inhibitor of glycinamide ribonucleotide formyltransferase in de novo purine biosynthesis on murine type collagen-induced arthritis (CIA). METHODS: CIA was induced by immunization with bovine type II collagen in adjuvant. The expression of folate receptors was examined in dissected synovial tissues and bone marrow cells from arthritic and non-arthritic mice by the semi-quantitative reverse transcription-polymerase chain reaction. LY309887 was administered to CIA mice after the onset of arthritis. Mice were monitored for arthritis index for 21 days. Levels of IgG1 and IgG2a antibodies against bovine type II collagen were measured in sera from CIA mice with or without LY309887 treatment by the enzyme-linked immunosorbent assay. Histologic analyse were also performed in synovial tissues from arthritic joints with or without LY309887 treatment. RESULTS: Levels of mRNA of folate receptor beta (FR-beta) were elevated in arthritic joints from CIA mice, compared with those in nonarthritic joints. The expression of mRNA of FR-beta was dominant in bone marrow cells of CIA mice. The administration of LY309887 suppressed the disease progression of CIA mice as defined by the lower arthritis index, and decreased production of serum IgG1 and IgG2a anti-type II collagen antibody, and the damage to cartilage or bone. CONCLUSION: The administration of LY309887 was effective on CIA mice. It was suggested that LY309887 might be useful in the treatment of rheumatoid arthritis.

Animals↗
PubMedDate not supplied

Osteogenesis by pulsing electromagnetic fields (PEMFs): optimum stimulation setting.

The optimum setting for electromagnetic stimulation was examined by histologically assessing the degree of osteogenesis at different settings of electromagnetic stimulation, and comparing alkaline phosphatase (ALP) activity in the bone marrow. For this experiment, an electromagnetic field generator manufactured by the Institute of Physical and Chemical Research was used. The intensity of the magnetic field was set at eight levels; 0.1, 0.2, 0.4, 1, 2, 4, 6 and 8 gauss (G). The frequencies used were 5, 10, 20, 50, 100 and 200 Hz. Pulse durations were 6, 12, 25, 50 and 100 micro sec. Significant ALP elevation and osteogenesis were observed at magnetic field intensities of 0.4, 1, and 2G. ALP activity did not differ between different frequencies. ALP activity at pulse durations of 25 and 50 micro sec were significantly higher than at the other pulse durations. The effect of electromagnetic stimulation on osteogenesis greatly depends on the intensity and pulse duration of the stimulation.

Alkaline Phosphatase↗
PubMedDate not supplied

The effect of pulsing electromagnetic field on bone ingrowth into a porous coated implant.

Electromagnetic stimulation is known to promote bone formation in cases of fracture and pseudoarthrosis. The possibility of using electromagnetic field to promote bone ingrowth into a porous coated implant was investigated in this study using Japanese albino rabbits. A titanium implant coated with beads of 250-300 microns in diameter around a stem of 1.7 mm in diameter was inserted into the humerus cavity of a Japanese albino rabbit. The humerus was stimulated by pulsing electromagnetic fields at 2 Gauss, 10Hz, 25 microseconds for 14 days. The circumference of grown bone into the implant was measured, and calculated in area equivalent for determination of the area of new bone. Bone ingrowth was significantly promoted by consecutive 14 days. The result suggests that electromagnetic stimulation is useful for achieving further bone ingrowth into a porous coated implant.

Animals↗