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Biomedical subjects

Y Hiramoto

Publications and source records attributed to Y Hiramoto.

At least 19 recordsLinked to original sources
PubMed1995

Centrifuge microscope as a tool in the study of cell motility.

The centrifuge microscope (CM) is composed of a centrifuge and a microscope optical system designed to observe minute objects, especially living cells, during the application of centrifugal acceleration. Structures and characteristics of various types of CM designed and constructed up to the present and studies done with the CM on cell biology, especially cell motility, are reviewed. These studies include observations of the behavior of cells and cell components in a centrifugal field, determination of the mechanical properties of the cell surface and cytoplasm, microsurgical operations on cells with centrifugal force, and determination of the magnitude and the site of generation of motive force for cell motility.

Animals↗
PubMed1994

Sperm and its soluble extract cause transient increases in intracellular calcium concentration and in membrane potential of sea urchin zygotes.

Fertilization is known to initiate a transient increase of intracellular calcium concentration and an accompanying change of membrane potential in sea urchin eggs. If the fertilization membrane and hyaline layer are removed, sperm can again enter fertilized eggs (refertilization). We have found that Ca2+ and voltage transients were repeatedly induced in fertilized eggs during refertilization. Similar changes were also obtained by external application of a soluble extract of sperm to fertilized eggs. This sperm extract caused no changes in unfertilized eggs. The active factor in the sperm extract survives heating (100 degrees C, 10 min) and incubation with pronase. Its molecular weight is less than 1300.

Animals↗
PubMed1994

Flexural rigidity of echinoderm sperm flagella.

The stiffness (flexural rigidity) of live sperm flagella, Triton-demembranated flagella (axonemes), trypsin-digested axonemes, and doublet microtubules of the axonemes in echinoderms was determined from the relationship between their deformation when a stream of medium was applied and the viscous resistance of the medium acting on the flagellum. The stiffness of the flagellum beating in seawater was 5.8 x 10(-21) Nm2 for bending in the direction perpendicular to the beating plane and 4.2 x 10(-22) Nm2 for bending within the beating plane. A similar difference in stiffness from the difference in bending directions was found in reactivated flagella with 1 mM ATP. The stiffness of live flagella immobilized in CO2-saturated seawater and axonemes in ATP-free medium was similar to that of beating flagella for bending in the direction perpendicular to the beating plane. The stiffness of motionless flagella significantly decreased with erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) and vanadate. The trypsin-digestion of motionless axonemes did not change their stiffness. The stiffness of doublet microtubules was 1.4 x 10(-23) Nm2 in 0.1 mM ATP medium and 6.1 x 10(-23) Nm2 in ATP-free medium. These results suggest that doublet pairs lying parallel to the beating plane of the flagellum retain fewer cross-bridges than doublet pairs lying perpendicular to the beating plane.

Adenine↗
PubMed1994

[The expression of neural cell adhesion molecule (NCAM), neural invasion and recurrence patterns in rectal cancer--a study using anti-NACM (neural cell adhesion molecule) antibody].

Neural invasion may be one of the main causes of local recurrence, but its mechanism has not been sufficiently clarified. We previously reported that the expression of NCAM on cancer cells was correlated with neural invasion in pancreatic cancer. In this study, we examined the neural affinity of rectal cancer cells and the relationship between neural invasion and recurrence patterns of rectal cancers. A total of 64 rectal adenocarcinoma were examined. Specimens from 17 patients (27%) revealed perineural invasion. The incidence of neural invasion increased with the frequency of venous invasion and the degree of lymph node metastasis, but not significantly. The incidence of the expression of NCAM in rectal cancer cell was 45.3 percent. Neural invasion of rectal carcinoma was significantly related to the expression of NCAM (p < 0.05). NCAM immunocytolocalization was classified into the focal type, and the diffuse type. Concerning the recurrence type, 8 of 9 cases that developed local recurrence showed either presence of neural invasion or expression of NCAM. Liver metastasis was associated with absence of neural invasion or NCAM expression. The expression of NCAM may contribute to local recurrence, whereas the absence of NCAM may predict liver metastasis.

Adenocarcinoma↗
PubMed1991

Site-specific mechanisms of initiation by chelated iron and inhibition by alpha-tocopherol of lipid peroxide-dependent lipid peroxidation in charged micelles.

To obtain information on the role of iron-catalyzed lipid peroxidation in the presence of the small amount of lipid peroxide in deterioration of biological membranes, we examined factors affecting peroxidation of fatty acids in charged micelles. Peroxidation of linoleic acid (LA) was catalyzed by Fe2+ via reductive cleavage of linoleic acid hydroperoxide (LOOH) in negatively charged sodium dodecyl sulfate micelles, but not in positively charged tetradecyltrimethylammonium bromide (TTAB) micelles. However, this Fe2(+)-induced, LOOH-dependent lipid peroxidation could be induced in TTAB micelles in the presence of a negatively charged iron chelator, nitrilotriacetic acid (NTA). The linoleic acid alkoxy radical (LO.) generated by the LOOH-dependent Fenton reaction was also trapped by N-t-butyl-alpha-phenylnitrone at the surface of TTAB micelles in the presence of NTA, but not in its absence. The degradation rates of two spin probes, N-oxyl-4,4'-dimethyloxazolidine derivatives of stearic acid (5-NS and 16-NS), were investigated to determine the site of production of radicals formed during LOOH-dependent lipid peroxidation. The rate of consumption of 16-NS during the LOOH-dependent Fenton-like reaction was higher in TTAB micelles containing LA than in those containing lauric acid (LauA), although the rates of formation of LO. in the two types of fatty acid micelles were similar. The rates of 5-NS consumption in LA and LauA micelles were almost the same and were as low as that of 16-NS consumption in LauA micelles. 16-NS was more inhibitory than 5-NS of LOOH-dependent lipid peroxidation, and this inhibition was associated with its higher consumption of 16-NS than of 5-NS. alpha-Tocopherol inhibited NTA-Fe2(+)-induced LOOH-dependent lipid peroxidation in TTAB micelles, and was oxidized during this inhibition process. The rate and amount of alpha-tocopherol oxidized by the LOOH-dependent Fenton reaction were higher in LA micelles than in LauA micelles. alpha-Tocopherol inhibited the consumption of 16-NS during NTA-Fe2(+)-induced LOOH-dependent lipid peroxidation more effectively than that of 5-NS. The distribution of the chromanol moiety of alpha-tocopherol was studied by the fluorescence quenching method. There was no difference between Stern-Volmer plots of the quenchings of alpha-tocopherol fluorescence by 5-NS and 16-NS. From these results, we discuss the mechanism of induction of LOOH-dependent peroxidation of LA and the mechanism of the antioxidant effects of alpha-tocopherol on it from the viewpoint of site-specific reaction.

Electron Spin Resonance Spectroscopy↗
PubMed1990

Mechanical properties of the cortex before and during cleavage.

The changes in stiffness of the cell before and during cleavage reported previously for various kinds of echinoderm eggs are classified into three types. There is no general rule that cleavage starts when the stiffness attains a maximum or a minimum. Because the stiffness of the cell surface is much greater than that of the mitotic apparatus, the change in stiffness of the cell represents mainly the change in stiffness of the cell surface. The tension at the cell surface changes in parallel over the entire surface before the onset of cleavage. After the onset of cleavage, the tension at the furrow surface becomes greater in the direction parallel to the furrow than perpendicular to it. A remarkable change in mechanical properties occurs at the furrow surface simultaneously with the onset of cleavage. Judging from the temporal and spatial coincidence between this change and the formation of the contractile ring reported previously in sea urchin eggs at the onset of cleavage, it is concluded that this change is due to the formation of the contractile ring that generates the motive force for cleavage.

Animals↗
PubMed1989

Effect of glucocorticoid replacement on tumor growth after adrenalectomy in mice.

We studied the effects of glucocorticoid replacement on tumor growth after adrenalectomy of Meth A sarcoma in mice. Tumor growth was inhibited in the adrenalectomized mice when a minimum dose of corticosterone, 0.3 mg/day, was given for replacement, and higher doses led to an even greater inhibition. Corticosterone had no effect on tumor growth in the irradiated mice. Sinecomitant immunity in the case of growth of the retransplanted excised tumor was compromised in the adrenalectomized mice. In vivo neutralization and immunosuppressive activities were absent in the spleen cells of the adrenalectomized mice. It would thus appear that adrenalectomy suppresses tumor growth by mechanisms other than glucocorticoid ablation. For optimum tumor control, glucocorticoid replacement after adrenalectomy should be in excess of the minimum daily requirements.

Adrenalectomy↗
PubMed1989

Sarcoma-180 cells are more sensitive to heat than are mouse normal tissues: esophagus, stomach, small intestine, large intestine, liver, spleen, and kidney.

Sensitivity of various mouse tissues to heat was determined using mouse sarcoma-180 (S-180) cells and normal tissues: esophagus, stomach, small intestine, large intestine, liver, spleen, and kidney. The in vitro succinate dehydrogenase inhibition (SDI) test was used. The succinate dehydrogenase (SD) activity of tissue fragments was assayed, following exposure to a temperature of 43 degrees C (heat treatment) or 37 degrees C (control) for 1, 2, 5, or 10 hr. The sensitivity to heat treatment was estimated by the percentage of SD activity of the heat-treated cells, compared to that of the control cells. The decrease in SD activity following exposure to heat varied with the tissue. The SD activity decreased to a greater extent in the S-180 cells than in the normal tissues. In the normal tissues, the order of sensitivity to heat was stomach, spleen, large intestine, small intestine, esophagus, kidney and liver. These results show that hyperthermia is tissue selective, hence heat treatment of a malignant lesion should be carefully designed.

Animals↗
PubMed1988

Micromanipulation studies of the mitotic apparatus in sand dollar eggs.

Mechanical properties of the mitotic spindle and the effects of various operations of the mitotic apparatus on the chromosome movement and spindle elongation were investigated in fertilized eggs and blastomeres of the sand dollar, Clypeaster japonicus. On the basis of results with mechanical stretching and compression of the spindle with a pair of microneedles and the behavior of an oil drop microinjected into the spindle, it was concluded that the equatorial region of the spindle is mechanically weaker than the half-spindle region. Anaphase chromosome movement occurred in the spindle from which an aster had been removed or separated with its polar end and in the spindle in which the interzonal region had been removed. This fact indicates that chromosomes move poleward in anaphase by forces generated near the kinetochores in the half-spindle. Because of the effects of separation or removal of an aster from the spindle on the spindle elongation in anaphase and the behavior of the aster, it was concluded that the spindle elongation in anaphase is caused by pulling forces generated by asters attached to the ends of the spindle.

Anaphase↗
PubMed1988

Mechanism of Ca2+ release in medaka eggs microinjected with inositol 1,4,5-trisphosphate and Ca2+.

The reaction time of Ca2+ release from cytoplasmic stores induced by microinjection of inositol 1,4,5-trisphosphate (IP3), calcium ionophore A23187, Ca2+, Sr2+, Ba2+, and cyclic guanosine 5'-monophosphate (cGMP) in Oryzias latipes eggs in Ca2+-free medium was measured by the luminescence of aequorin injected into the egg. Microinjection of IP3 or calcium ionophore induced rapid Ca2+ release without a time lag, while microinjection of either Ca2+ or cGMP required a time lag of 5-30 sec for Ca2+ release. Following microinjection of both IP3 and Ca2+, Ca2+ release commenced in a cytoplasmic region close to the egg surface. These results suggest that in the medaka egg, cytoplasmic Ca2+ induces Ca2+ release from cytoplasmic stores indirectly, probably via a membrane factor such as IP3.

Aequorin↗
PubMed1988

Cytoplasmic Ca2+ release induced by microinjection of Ca2+ and effects of microinjected divalent cations on Ca2+ sequestration and exocytosis of cortical alveoli in the medaka egg.

Intracellular release of Ca2+ by microinjection of Ca2+ was analyzed by measuring the luminescence of aequorin loaded in eggs of the medaka (Oryzias latipes). Microinjection of Ca2+ into the cortical cytoplasm induced propagative waves of cytoplasmic Ca2+ release and exocytosis of cortical alveoli initiated at the injection point. The Ca2+ wave was initiated with a time lag after some was sequestered at the region of the microinjection. Microinjection of Mg2+ or Mn2+ failed to trigger Ca2+ release and exocytosis. When the aequorin-loaded eggs were inseminated after microinjection of Mg2+, Mn2+, or Co2+ into a restricted region of the vegetal hemisphere, the wave of Ca release was propagated through the injected region toward the vegetal pole, but neither Ca sequestration (fall in Ca-aequorin luminescence) nor exocytosis occurred at the area of cortex where the eggs were injected with these divalent cations. These results suggest that a significant period is required to induce Ca2+ release from cytoplasmic stores by the increased Ca2+ concentration and that both the phenomena of Ca2+ release and Ca sequestration are involved in the process of exocytosis.

Animals↗
PubMed1988

Lymphadenectomy for cure in patients with early gastric cancer and lymph node metastasis.

The anatomic distribution, size, and histologic mode of involvement of 98 metastatic lymph nodes in 49 of 370 patients were examined to determine to what extent lymphadenectomy should be performed in addition to gastrectomy in patients with early gastric cancer. Nodal involvement in the marginal sinus (30 nodes) and partial medullary sinus (37 nodes) were commonly seen, and the lymph nodes of those types were enlarged compared with 1,086 patients with no metastatic lymph nodes (control group). Lymph nodes of the wide medullary sinus (11 nodes), small nodule (3 nodes), and massive involvement types (17 nodes) did not enlarge compared with those of the other types and those of the control group. Most of the metastatic sites (76.6 percent) were in the perigastric lymph nodes along the lesser and greater curvatures, about a fifth were in the extraperigastric nodes along the left gastric, common hepatic, celiac, and splenic arteries, and the least were in the extraperigastric nodes (3.1 percent) along the hepatoduodenal ligament. Since the rate of macroscopic diagnosis during operation was so poor, regardless of the histologic modes of nodal involvement, and also in cases of metastatic lymph nodes less than 15 mm in widest diameter, for curative operation of patients with early gastric cancer, perigastric and extraperigastric lymph nodes along the main arteries near the stomach should be completely dissected, in addition to resection of the stomach.

Adenocarcinoma↗
PubMed1988

The amino acid sequence, immunofluorescence and microinjection studies on the 15 kDa calcium-binding protein from sea urchin egg.

The 15 kDa protein is the most abundant low molecular weight Ca2+-binding protein, different from calmodulin, in eggs of sea urchin, Hemicentrotus pulcherrimus. The data from the amino acid sequence demonstrated that the 15 kDa protein belonged to the troponin C superfamily. Based on immunofluorescent and immunomicroscopic observations, we showed that the 15 kDa protein localized in the nuclei of fertilized eggs and mitotic apparatus of dividing eggs. Microinjection of the antibody against 15 kDa protein into sea urchin blastomeres resulted in the arresting of cell division. These results suggest that the 15 kDa protein plays an important role in mitosis of sea urchin egg.

Amino Acid Sequence↗
PubMed1987

Effect of glucocorticoid deficiency after adrenalectomy on antitumor immunity.

We studied the effect of corticosterone after adrenalectomy on antitumor immunity in immunogenic tumors in mice. Antitumor immunity in the glucocorticoid deficient adrenalectomized mice (ADX mice) examined via comitant immunity and cytotoxic activity of spleen cells was compromised. Antitumor immunity was detected in ADX mice receiving sufficient supplementary doses of corticosterone. Loaded stress compromised the cytotoxic activity of the spleen cells in the ADX mice receiving adequate corticosterone, and the failure also contributed to the glucocorticoid deficiency because the activity was not affected by stress in the sham ADX mice. A matured effector cell activity was transferred to the glucocorticoid deficient ADX mice. We conclude that glucocorticoid deficiency compromises the antitumor immune response and that glucocorticoid might play an important role in the maturation of immunocompetent cells.

Adrenalectomy↗
PubMed1987

Specific expression of the chicken delta-crystallin gene in the lens and the pyramidal neurons of the piriform cortex in transgenic mice.

Two transgenic mice, 5-8 and 7-5, carrying the chicken delta-crystallin gene were produced by microinjecting cloned genes into male pronuclei. The mice were analyzed at 8 weeks of age with respect to gene integration and expression by means of blotting techniques and immunohistochemistry. Southern blot analysis indicated that both mice carried, on average, 50 copies of intact delta-crystallin gene per cell. Histological analysis of the mice using DNA-DNA in situ hybridization indicated that mouse 5-8 carried the delta-crystallin gene in every cell while mouse 7-5 was mosaic, with 20-40% of the cells of various tissues carrying the gene. Western blot analysis indicated that in both mice delta-crystallin is expressed in the lens and the cerebrum, but not in any other tissue examined. Immunohistological analysis revealed that, in the cerebrum of the mice, delta-crystallin was expressed specifically in pyramidal neurons located in layer IIb of the anterior piriform cortex. Thus, our results with transgenic mice not only demonstrate the primary specificity of delta-crystallin gene expression in authentic lens tissue, but reveal the unexpected specificity of this chicken gene in the central nervous system of the mouse.

Animals↗