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Biomedical subjects

K Ohki

Publications and source records attributed to K Ohki.

190 records · Page 11Linked to original sources
PubMed1979

Correlation between fluidity and fatty acid composition of phospholipid species in Tetrahymena pyriformis during temperature acclimation.

The correlation between the fluidity of phospholipids and their fatty acid composition was studied by spin label technique and gas-liquid chromatography for three major phospholipid species in Tetrahymena pyriformis during temperature acclimation. The fluidity of 2-aminoethylphosphonolipid increased within the first 10 h of the cold-acclimation when the content of gamma-linolenic acid in 2-aminoethylphosphonolipid was highest, and it then decreased up to 24 h. On the other hand, the fluidities of phosphatidylethanolamine and phosphatidylcholine showed a gradual decrease up to 24 h after the temperature shift, although gamma-linolenic acid contents were highest at 10 h after the temperature shift. Thus the fluidity changes of these two phospholipids were interpreted as resulting from the altered content of other fatty acids in addition to gamma-linolenic acid, since the gamma-linolenic acid content was smaller than that of 2-aminoethylphosphonolipid. The results suggest that the content of gamma-linolenic acid in 2-aminoethylphosphonolipid plays a role in regulating the thermal adaptation process.

Acclimatization↗
PubMed1979

Interaction of polyene antibiotics with sterols in phosphatidylcholine bilayer membranes as studied by spin probes.

Interaction of filipin and amphotericin B with sterols in phosphatidylcholine membranes has been studied using various spin probes; epiandrosterone, cholestanone, phosphatidylcholine with 12-nitroxide or 5-nitroxide stearate attached to 2 position and also with tempocholine at the head group. Filipin caused increase in the fluidity of cholesterol-containing phosphatidylcholine membranes near the center, while it rather decreased the fluidity near the polar surface. On the other hand, amphotericin B did not apparently affect the fluidity. In the electron spin resonance spectrum of steriod spin probes in the antibiotic-containing membranes, both bound and free signals were observed and the association constant was calculated from the siganal intensity. In the binding of steriods with filipin, both 3 and 17 positions were involved, while the 17 positions was less involved in the binding with amphotericin B. Phase change in the host membrane markedly affected the interaction of filipin with epiandrosterone probe. The bound fraction jumped from 0.4 to 0.8 on going to the crystalline state and increased further with decrease in temperature. The overall splitting of the bound signal also increased on lowering the temperature below phase transition. This change was attributed to aggregate formation of filipin-steriod complexes in the crystalline state. On the other hand, effect of phase transition was much smaller on the interaction of amphotericin B with the steriod probe.

Amphotericin B↗
PubMed1979

The effect of metal complex of thyrotropin-releasing hormone on locomotor activity of neonatal chicken.

Neonatal chickens were injected intraventricularly with Ni(II), Pd(II), Cu(II) or Zn(II) complex of TRH and the potencies of stimulating locomotor activity were compared with that of TRH, Ni(II)-TRH was more potent than the ligand while Pd(II)-TRH was inert. Cu(II)- and Zn(II)-TRH induced the response to the same extent of the ligand. These results indicate that the action of TRH in the CNS resulting in the locomotor hyperactivity is dependent on the tertiary conformation of molecule which is modified by chelate formation.

Animals↗
PubMedDate not supplied

Structure and phase behaviour of dimyristoylphosphatidic acid/poly(L-lysine) systems.

Differential scanning calorimetry (DSC) and X-ray diffraction studies on (DMPA)/poly(L-lysine) systems are reported. DSC studies revealed that addition of poly(L-lysine) to DMPA bilayers raises the gel to liquid-crystalline phase transition of the systems, and that this effect depends on the molecular weight of the poly(L-lysine). Small-angle X-ray diffraction measurements showed that, in the liquid-crystalline phase, the lamellar spacing of a DMPA/short-poly(L-lysine) (approximately 4000 mol. wt.) system is shorter than that of a DMPA/long-poly(L-lysine) (approximately 22000 mol. wt.). In this connection wide-angle X-ray diffraction measurements indicate that the long-poly(L-lysine) adopts a beta-sheet conformation on the DMPA bilayers in both the gel and the liquid-crystalline phases, but the short-poly(L-lysine) adopts this conformation only on gel phase DMPA bilayers. We found that the spacings of the hydrocarbon chain packing in a DMPA bilayer in the gel phase increases with temperature, while the spacing between neighbouring polypeptide chains in long-poly(L-lysine) in the beta-sheet conformation remains almost constant. These observations indicate that the positively charged lysine residues are structurally independent of the negatively charged head groups of the phospholipid. On the basis of the present results we propose a model to explain the elementary behaviour of extrinsic membrane proteins in biomembranes.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

Granular cell ameloblastoma of the mandible with metastasis to the third thoracic vertebra. A case report.

A 62-year-old housewife had a metastasis of granular cell ameloblastoma to the third thoracic vertebra. She had suffered at least four local recurrences during the 38-year duration of the right mandibular tumor and was treated by posterior decompression of the spinal cord with instrumentation. Histologically, the granular cells appeared to be of epithelial origin. Ultrastructurally, the granules were identified as lysosomes, including some that were autophagic. Of 45 reported cases of granular cell ameloblastoma, there have been only three cases with pathologically confirmed metastasis. Their characteristics are long duration of the tumor, multiple local recurrences, and predominance in blacks.

Ameloblastoma↗
PubMedDate not supplied

A study of discoloration of the gingiva by artificial crowns.

In this study, soft tissue discoloration including the marginal gingiva, gingival papilla, and attached gingiva were evaluated in subjects with artificial crowns and compared to the soft tissue of natural teeth using a spectrophotometer. Gingivae around artificial crowns had a lower value (L*) and chroma (C*ab) than the gingivae surrounding natural teeth. Hue (Hab o) shifts toward red-purple were frequently noted. There was generally a more noticeable color difference (E*ab) in the marginal gingiva and gingival papilla of teeth with crowns than was found in the attached tissue.

Adult↗