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Biomedical subjects

K Hiraki

Publications and source records attributed to K Hiraki.

At least 19 recordsLinked to original sources
PubMed1991

Conformation changes of cuttlefish (Euprymna morsei) rhodopsin following photoconversion.

Cuttlefish (Euprymna morsei) rhodopsin solubilized in lauryl ester of sucrose and its photoproduct, acid metarhodopsin, were examined by small-angle X-ray scattering and chromatofocusing to investigate the conformation changes of visual pigment following photoconversion. From spectroscopic studies, it was found that more than 93% of Euprymna rhodopsin could be converted to meta form under the condition of red light irradiation at neutral pH. Since almost pure acid metarhodopsin solution was prepared without changing the specimen concentration, the small-angle X-ray scattering intensities of both pigment-detergent complexes were directly compared. The radius of gyration increased on going from rhodopsin to acid metarhodopsin by approximately 1.5%. There were also discernible changes in the secondary peak intensities. The distribution function, derived by the Fourier transformation of intensity data, showed a significant change around 55 A. The maximum linear dimension of the rhodopsin-detergent complex was about 95 A and hardly changed after illumination. Intensity at zero angle did not change after illumination, suggesting that the aggregation did not occur. The change of the intensity profile could be due to the conformational change of the pigment-detergent monomers. The pI value of rhodopsin determined by chromatofocusing was 5.32 and that of acid metarhodopsin was 5.06, indicating that a few carboxyl groups are newly dissociated. The shift of the protein mass and the charge redistribution were observed following photoconversion.

Animals↗
PubMed1988

Amino acid sequence of the retinal binding site of squid visual pigment.

The retinylpeptides of visual pigments of two species of squid were identified in invertebrate visual pigments. Their primary structures were identical: H-Phe-Ala-Lys-Ala-Ser-Ala-Ile-His-Asn-pro-Hse(Met)-OH. The sequence was homologous to those of the corresponding region of other visual pigments, but the eighth amino acid, His, was found in squid visual pigments. In this experiment the retinylpeptides of eleven amino acid residues were isolated by monitoring the absorbance spectrum of the reduced retinal Schiff base without using radio-active [3H]retinal. This method is valid for the isolation and identification of retinylpeptides of other invertebrate visual pigments in which the chromophore is not exchangeable.

Amino Acid Sequence↗
PubMed1988

4-Hydroxyretinal, a new visual pigment chromophore found in the bioluminescent squid, Watasenia scintillans.

The bioluminescent squid, Watasenia scintillans has three visual pigments. The major pigment, based on retinal (lambda max 484 nm), is distributed over the whole retina. Another pigment based on 3-dehydroretinal (lambda max approximately 500 nm) and the third pigment (lambda max approximately 470 nm) are localized in the specific area of the ventral retina just receiving the downwelling light. Visual pigment was extracted and purified from the dissected retina. The chromophores were then extracted and analyzed with HPLC, NMR, infrared and mass spectroscopy, being compared with the synthetic 4-hydroxyretinal. A new retinal derivative, 11-cis-4-hydroxyretinal, is identified as the chromophore of the third visual pigment of the squid.

Animals↗
PubMed1986

Fluorometry of nanogram amounts of selenium in biological samples.

For fluorometry of selenium in human blood, hair, and liver and in leaves, we wet-ashed the samples with conventional nitric and perchloric acids, and then extracted piazselenol (complex of Se and 2,3-diaminonaphthalene) in cyclohexane. Selenium was back-extracted from the cyclohexane into nitric acid to remove the fluorometric interferences of trace amounts of organic compounds. This fluorometric method is rapid and suitable for routine analysis. We applied the method to human hair samples and compared it with the data for non-destructive neutron activation analysis of the hair.

2-Naphthylamine↗
PubMed1985

Volatile anesthetics cause conformational changes of bacteriorhodopsin in purple membrane.

We examined the effects of volatile anesthetics on the structure of the bacteriorhodopsin in the purple membrane by measurements of the absorption spectrum and the visible circular dichroism (CD) spectrum and assay of the retinal composition. As the concentrations of halothane, enflurane and methoxyflurane were increased, the absorption at 560 nm decreased but that at 480 nm increased with an isosbestic point around 510 nm. These anesthetic-induced spectroscopic changes were reversible. The CD spectrum showed the biphasic pattern with a positive and a negative band. As the concentration of halothane was increased from 4 mM to 8mM, the negative band reversibly diminished more drastically than the positive band, and at 8 mM of halothane the positive band shifted to around 480 nm. These results show that halothane disturbed the exciton coupling among bacteriorhodopsin molecules. The retinal isomer composition was analyzed using high performance liquid chromatography. The ratio of 13-cis- to all-trans-retinal was 47:53, 34:66 and 19:81 at control, 7.4 mM and 14.9 mM enflurane, respectively. After elimination of enflurane, the ratio returned to the control value. These findings indicate that volatile anesthetic directly affect a bacteriorhodopsin in the purple membrane and induce conformational changes in it.

Anesthetics↗
PubMed1977

Vitamin B12 levels of cerebrospinal fluid in patients with a variety of neurological disorders.

The vitamin B12 levels of cerebrospinal fluid were assayed microbiologically (Lactobacillus leichmannii method) using samples from 44 patients with various neurological disorders, 4 patients with megaloblastic anemia and 34 controls. Twenty-seven controls that did not receive vitamin B12 showed a mean cerebrospinal fluid vitamin B12 level of 21.5 pg/ml (range: 0-60). No decrease in cerebrospinal fluid vitamin B12 level was seen in patients with subacute myelo-optico-neuropathy (SMON). High levels of cerebrospinal fluid vitamin B12 were observed only in the patients receiving long term administration of the vitamin. Intrathecal administration of vitamin B12 caused only a slight increase in serum vitamin B12 level after four hours. The existence of blood brain barrier for vitamin B12 was suggested.

Anemia, Megaloblastic↗
PubMed1976

Production of lymphoid tumors in hamsters by direct implantation of normal human peripheral and umbilical cord leukocytes.

Peripheral leukocytes from Epstein-Barr virus (EBV)-seropositive or seronegative normal adults, or human umbilical cord leukocytes infected or not infected with EBV, were directly transplanted into 50 newborn hamsters treated with anti-lymphocyte serum. Lymphoid tumors were produced after a latent period of 10-25 days in 39 animals: 8 of 14 recipients of seropositive donor leukocytes, 2 of 2 recipients of seronegative donor leukocytes, 13 of 15 recipients of EBV-infected cord leukocytes, and 16 of 19 recipients of non-infected cord leukocytes. EBV-determined nuclear antigen-positive human lymphoblastoid cell lines were established in vitro from tumors produced with seropositive donor leukocytes or EBV-infected cord leukocytes but not from tumors produced with seronegative donor leukocytes or non-infected cord leukocytes. The results indicate that EBV is not a prerequisite for in vivo production of tumors but necessary for in vitro establishment of lymphoblastoid cell lines from such tumors.

Animals↗
PubMed1975

Effect of sodium dodecyl sulfate on immuno-electrosyneresis between normal human erythrocyte membrane and sera of systemic lupus erythematosus patients.

An anti-membrane antibody was present in the sera of systemic lupus erythematosus patients in immunoelectrosyneresis with sodium dodecyl sulfate (SDS) solubilized erythrocyte membrane as antigen. The SDS bound to protein was detected by chromatography at 10(-3)M concentration under U.V. light, at 10(-5)M concentration by the distilled water spray method and at 10(-6)M concentration by using rosaniline hydrochloride colorimetry. SDS was removed from the membrane protein at a concentration of 10(-3)M by the first gel filtration of Sephadex G-25 column and at a concentration of 10(-6)M by rechromatography of the same column. More than 99% of SDS in the solubilized erythrocyte membrane was removed by gel filtration. The antigenicity was still positive in the refiltrated fractions of systemic lupus erythematosus patients. Therefore, all precipitates in the gels were antigen-antibody aggregates.

Antibodies↗