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Biomedical subjects

K Ohki

Publications and source records attributed to K Ohki.

At least 37 records · Page 2Linked to original sources
PubMed1998

Preparation of liposome-encapsulating adenosine triphosphate.

Liposomes encapsulating adenosine triphosphate (ATP) were prepared by sonication, and the liposomes were evaluated for use in a drug delivery system. The liposomes, which were composed of phosphatidylcholine and cholesterol, were about 1.1 microm in size, as observed under a microscope. From their size, the vesicles were thought to be multilamellar. The maximum concentration of ATP in the liposomes was 1.0 mM, when the initial concentrations of lipid and ATP were 20 mM and 300 mM, respectively. The maximum entrapment ratio of ATP in the liposomes was 88%, when the initial concentrations of lipid and ATP were 20 mM and 500 mM, respectively. About 4% of ATP was encapsulated in these experiments. When liposomes contained 4-7% of cholesterol, about 35% of encapsulated ATP was released from the liposomes for 90 hours at 37 degrees C in vitro. These findings indicated that liposomes encapsulating ATP could be used for the treatment of ischemic retina.

Adenosine Diphosphate↗
PubMed1998

[Pulmonary artery injury caused by mal-manipulation of a pulmonary artery catheter].

A 71-year-old male was scheduled for aortic valve replacement. After tracheal intubation under high-dose fentanyl anesthesia, a pulmonary artery balloon catheter was inserted via the right internal jugular vein. However, after withdrawing the catheter with the balloon inflated, we found abrupt massive bleeding from the endotracheal tube. Fortunately, hemorrhage stopped with PEEP (20-25 cmH2O). Bronchofiberscopy could not detect the bleeding point. Chest X-ray showed the pulmonary artery balloon catheter in the right pulmonary artery and atelectasis of the middle and lower lobes. Five days later, he was extubated without rehemorrhage. Three weeks after hemorrhage, the patient successfully underwent an aortic valve replacement, and was discharged on the 25th post-operative day.

Aged↗
PubMed1997

A chain section containing epitopes for cytotoxic T, B and helper T cells within a highly conserved region found in the human immunodeficiency virus type 1 Gag protein.

Cell-mediated immune responses constitute a major defense against the spread of human immunodeficiency virus type 1 (HIV-1). However, multiple alterations within a particular epitope may accumulate during disease progression, allowing the virus to escape cytotoxic T lymphocytes (CTLs). Therefore, the best candidate for a peptide vaccine that would prevent the onset of the disease might be a chain section containing epitopes for the generation of CTLs in regions of conserved sequences among different HIV-1 isolates. We previously showed that immunizing mice with synthetic peptides consisting of 23-amino acids (Gag-23mer; 287-309 amino acid residues) in a highly conserved region derived from the major core protein p24 of HIV-1 generates specific CTLs as well as antibodies. Here, we identified one CTL (T-1; 291-300) and two B-cell (B-1; 290-299 and B-2; 300-309) epitopes, all of which consisted of 10 amino acids within the region. In addition, helper T cells primed by the Gag-23mer peptide were proliferated by in vitro stimulation with a 21mer (H-1; 289-309) or a 19mer (H-2; 291-309) peptide, but not with a 17mer peptide (293-309) or 19mer peptide (287-305). Immunization with the H-1 peptide generated an antibody reactive to B-1, but not B-2, whereas that with H-2 generated an antibody reactive to B-2, but not B-1. CTLs were not generated by immunization with these peptides, indicating that the entire sequence of Gag-23mer is the helper epitope for CTLs. Thus, the Gag-23mer is a chain section containing epitopes for cytotoxic T, B and helper T-cells within a highly conserved region of HIV-1 Gag protein.

AIDS Vaccines↗
PubMed1997

Clival chordoma presenting as acute esotropia due to bilateral abducens palsy.

A case involving a 14-year-old girl having clival chordoma with symptoms of diplopia, acute esotropia, and bilateral abducens palsy is reported. Magnetic resonance imaging revealed a clival tumor invading the posterior edges of the bilateral cavernous sinuses. After removal of the tumor, no ocular manifestations were noted. The importance of acute esotropia as a sign indicating a possible brainstem mass is emphasized.

Abducens Nerve↗
PubMed1997

Evaluation of blood acid-base balance after experimental administration of endotoxin in adult cow.

Esherichia coli endotoxin was administered intravenously to 7 Holstein adult cows, to evaluate the effect of endotoxin on acid-base balance. Endotoxin shock was observed immediately after the administration of endotoxin. A loss of appetite and depression of digestive tract motility continued for about 120 hr after the challenge. Metabolic alkalosis following hypochloremia and hypokalemia were particularly pronounced at 12 to 72 hr after the administration of endotoxin.

Acid-Base Equilibrium↗
PubMed1997

Circulating tumor necrosis factor and interleukin-1 after administration of LPS in adult cows.

This study examined the levels of serum tumor necrosis factor (TNF), interleukin-1 (IL-1) and plasma cortisol levels in adult cows after intravenous administration of lipopolysaccharide (LPS) extracted from Escherichia coli. The adult cows exhibited clinical signs of endotoxic shock. The mean concentrations of serum TNF was 557.9 U/ml and serum IL-1 was 90.6 U/ml at 2 hr after LPS administration following severe endotoxic shock. Plasma cortisol concentrations increased immediately and a peak level was 131.4 ng/ml at 1 hr after LPS challenge. These results suggested that circulating concentrations of TNF, IL-1, and cortisol may be associated with clinical signs of endotoxemia in adult cows.

Animals↗
PubMed1996

Targeted mutagenesis of acyl-lipid desaturases in Synechocystis: evidence for the important roles of polyunsaturated membrane lipids in growth, respiration and photosynthesis.

Acyl-lipid desaturases introduce double bonds (unsaturated bonds) at specifically defined positions in fatty acids that are esterified to the glycerol backbone of membrane glycerolipids. The desA, desB and desD genes of Synechocystis sp. PCC 6803 encode acyl-lipid desaturases that introduce double bonds at the delta12, omega3 and delta6 positions of C18 fatty acids respectively. The mutation of each of these genes by insertion of an antibiotic resistance gene cartridge completely eliminated the corresponding desaturation reaction. This system allowed us to manipulate the number of unsaturated bonds in membrane glycerolipids in this organism in a step-wise manner. Comparisons of the variously mutated cells revealed that the replacement of all polyunsaturated fatty acids by a monounsaturated fatty acid suppressed growth of the cells at low temperature and, moreover, it decreased the tolerance of the cells to photoinhibition of photosynthesis at low temperature by suppressing recovery of the photosystem II protein complex from photoinhibitory damage. However, the replacement of tri- and tetraunsaturated fatty acids by a diunsaturated fatty acid did not have such effects. These findings indicate that polyunsaturated fatty acids are important in protecting the photosynthetic machinery from photoinhibition at low temperatures.

Calorimetry, Differential Scanning↗
PubMed1996

A Chinese hamster ovary cell mutant resistant to phosphatidylserine is defective in transbilayer movement of cell surface phosphatidylserine.

A mammalian plasma membrane protein(s) which catalyzes ATP-dependent transbilayer movement (flip-flop) of phosphatidylserine (PS) has been suggested to be involved in the formation and maintenance of membrane lipid asymmetry. Flip-flop of PS in the cell surface of nucleated cells was first described by O. C. Martin and R. E. Pagano (1987, J. Biol. Chem. 262, 5890-5898). It has been suggested that flip-flop is involved in the internalization of exogenous PS in cultured cells. In the present study we report that incubation with an excess amount of PS is cytotoxic to Chinese hamster ovary (CHO) cells, while the same amount of phosphatidylcholine gives no effect. This effect allowed us to obtain PS-resistant cells among mutagenized CHO cells. Endocytosis-independent internalization of exogenous fluorescent PS analog was defective in 40% of the PS-resistant mutants. One of the mutants, PSR (phosphatidylserine resistant) 406 was further characterized. Unlike wild-type CHO cells, this mutant did not transport fluorescent PS significantly at 15 degrees C. Fluorescent PS was not metabolized at 15 degrees C in either wild-type or mutant cells. These results suggest that transbilayer movement of cell surface PS is defective in PS-resistant cells.

Animals↗
PubMed1996

Changes in descemet membrane and endothelium after corneal epithelial abrasion alone and with photorefractive keratectomy in rabbits.

OBJECTIVES: To investigate the effects of epithelial abrasion on the corneal endothelium and Descemet membrane in rabbits and to compare the changes with those after excimer laser photoablation of the cornea. METHODS: Central epithelial abrasions, 6 mm in diameter, were created by mechanical removal of the cells, and the specimens were examined from 24 hours up to 30 days by transmission electron microscopy. Corneas that were photoablated by an excimer laser and nontreated normal corneas were investigated as controls. RESULTS: Corneas denuded of epithelium showed massive enlargement of the mitochondria in the endothelium and exhibited a layer of electron-dense fibrillogranular material that had migrated forward through the Descemet membrane. These alterations were similar to the changes observed after photoablation of the cornea by an excimer laser. CONCLUSION: It was postulated that the extrusion of electron-dense material in the Descemet membrane observed after excimer laser ablation might have occurred primarily not as a result of shock waves, but from destruction of the epithelial integrity.

Animals↗
PubMed1996

c-fos gene expression in postnatal rat retinas with light/dark cycle.

We examined the diurnal variation of c-fos gene expression during a 12:12 light/dark cycle in developing rat retinas by in situ hybridization histochemistry. c-fos Gene was not expressed before postnatal day 10 (P10) but was expressed on P15 in the outer nuclear layer throughout the dark period and in the inner nuclear layer and the ganglion cell layer during the light period. These results demonstrated that the earliest c-fos gene expression occurred between P11 and P15. The good correlation between the expression of c-fos gene and the genes coding for proteins involved in phototransduction, in terms of their diurnal variation and in their development, suggested that c-fos gene may play a role in the regulation of these genes in retinal cells during the light/dark cycle.

Animals↗
PubMed1996

Mitogenic effect of HIV-infected human T cell lines on mouse B cells mediated by surface immunoglobulin.

Following HIV-1 infection, a number of disorders are induced in both normal T and B cells by virus products derived from infected CD4+ T cells. In the present study, we found that HIV-infected, but not uninfected, human T cell lines generated vigorous blastogenesis and proliferation of freshly isolated mouse B cells in a short-term culture. Neither human B cells nor rat B cells showed significant responses to the HIV-infected T cell lines in the present condition. The mitogenic effect of HIV-infected human T cell line requires direct cell-cell interaction between mouse B cells and HIV-infected T cell lines. Since either mitomycin c treatment or paraformaldehyde fixation of HIV-infected T cell lines resulted in complete loss of the mitogenic effect, it seems that de novo synthesized viral products are responsible for this effect. Furthermore, anti-mouse immunoglobulin antibody inhibited completely the B cell stimulation by the HIV-infected human T cell lines. Thus, surface immunoglobulin (sIg) on mouse B cells appears to be an essential molecule which transduces activation signals from HIV-infected human T cells into cytoplasm of the B cells.

Animals↗
PubMed1996

Effect of growth condition on in-vitro susceptibility of Shigella dysenteriae type 1 killing by murine peritoneal macrophages.

The intracellular fate of Shigella dysenteriae type 1 strains grown in casamino acid-yeast extract (CYE) broth and nutrient broth (NB) was studied in casein-elicited mouse peritoneal macrophages. Virulent strains 14731 and W30864 cultured in NB and opsonised with normal mouse serum were susceptible to killing by peritoneal macrophages (66 SEM 1.7% killing by 2 h). In contrast, both strains grown in CYE broth and opsonised with normal mouse serum showed resistance to killing by peritoneal macrophages (76 SEM 1.4% survival by 2 h). Electronmicroscopy demonstrated that the bacteria escaped from the phagosome compartment by lysing the phagocytic vacuole and remained within the cytoplasm. Lipopolysaccharide (LPS) stimulated peritoneal macrophages to kill the opsonised strains 14731 and W30864 grown in CYE broth (85.4 SEM 1.6% killing by 2 h). Recombinant murine gamma interferon (rIFN-gamma) also stimulated macrophages to kill CYE-grown bacteria (52.1 SEM 1.3% killing by 2 h). However, an avirulent rough mutant strain W30864-22 grown in either NB or CYE broth showed marked susceptibility to killing by peritoneal macrophages, which was similar to that of NB-grown strain 14731 or W30864. The results of the present study suggest that in-vitro growth conditions may modulate the susceptibility of S. dysenteriae type 1 to killing by phagocytes.

Animals↗
PubMed1996

Hydrolytic cleavage of pyroglutamyl-peptide bond. II. Effects of amino acid residue neighboring the pGlu moiety.

We studied the susceptibility of the pyrrolidone moiety and the pyroglutamyl-peptide bond at pGlu-X-Ala-Phe-OH (X = Gly, Ala, Tyr, Ile, Pro, His, Lys, Arg, Thr, Ser, Asp, Glu and Trp) to 1 N HCl or 2 M trifluoromethanesulfonic acid at 60 degrees C. Here we describe the rates of the cleavage reaction of the pGlu-X bond, the pyrrolidone ring-opening reaction of the pGlu moiety and the hydrolysate accumulation. The rank order of the susceptibility rates of the cleavage reactions was Ser > Pro, Gly > Arg, Ala, Glu, Thr, Asp > His, Lys > Trp, Tyr, Ile, and that of the ring-opening reaction was Ile > Tyr, Trp > Arg, His, Lys, Asp > Glu > Ala > Pro, Gly > Ser > Thr. The rank order of the half-lives of the model peptides was Pro > Arg, Lys, Ile > His, Glu > Ala, Tyr > Asp > Gly > Ser > Thr. The results indicated that a bulky and sterically hindered side chain of the amino acid residue neighboring the pGlu moiety favors the ring-opening reaction, and retards the decomposition on acid hydrolysis and the cleavage reaction. Thus, the ring-opening and the cleavage reactions were greatly affected by the amino acid residue neighboring the pGlu moiety in the hydrolysis of pGlu-peptides.

Amino Acids↗
PubMed1996

Hydrolytic cleavage of pyroglutamyl-peptide bond. III. A highly selective cleavage in 70% methanesulfonic acid.

A method for highly selective cleavage of pGlu-peptide linkages in 70% methanesulfonic acid (MSA) is described. When pGlu-Ala-Phe-OH, pGlu-His-Pro-Oh and dog neuromedin U-8 (d-NMU-8) (1--7)-OH (pGlu-Phe-Leu-Phe-Arg-OH) were hydrolyzed in 70% MSA at 60 degrees C for 3 h or at 25 degrees C for 3 d, the pGlu-peptide linkage was predominantly cleaved to give H-Ala-OH, H-His-Pro-OH and H-Phe-Leu-Phe-Arg-Pro-Arg-OH, in high yields. The results indicated that pGlu-peptide linkages are highly susceptible to 70% MSA, whereas the amide bond of the pyrrolidone moiety of the pGlu residue and other internal peptide bonds are extremely resistant.

Animals↗
PubMed1996

Study on surfactin, a cyclic depsipeptide. II. Synthesis of surfactin B2 produced by Bacillus natto KMD 2311.

The total synthesis of surfactin B2, a cyclic depsipeptide isolated from Bacillus natto KMD 2311, was achieved to elucidate the absolute configuration of its fatty acid moiety. This is the first chemical confirmation of the absolute configuration of a surfactin homolog. Two possible diastereoisomers of surfactin B2, cyclo[D- and L-3-(Glu-Leu-D-Leu-Val-Asp-D-Leu-Leu-O)-n-tetradecanoyl] (1a and b), were synthesized by a solution method using mainly active ester and azide fragment condensation methods. Cyclization reaction of the partially protected linear depsipeptide containing the C-terminal N-succinimidyl active ester in pyridine by the high dilution method at room temperature for 3d gave the desired cyclic depsipeptide in a high yield of about 70%. The synthetic product 1a, containing the D-isomer of 3-hydroxytetradecanoic acid as a fatty acid moiety, was identical with natural surfactin B2.

Amino Acid Sequence↗
PubMed1996

Highly selective cleavage of pyroglutamyl-peptide bond in concentrated hydrochloric acid.

Highly selective cleavage reaction of pGlu-peptide bond is described. Two model peptides, pGlu-X-Ala-Phe-OH (X = Ile and Ser), and dog neuromedin U-8 (d-NMU-8) (1-7)-OH (pGlu-Phe-Leu-Phe-Arg-Pro-Arg-OH) were hydrolyzed in concentrated HCl at 0 degree C for from 6 days to 6 weeks to give the predominant cleavage products of pGlu-X linkage of pGlu-X-Ala-Phe-OH and the pGlu-Phe linkage of d-NMU-8 (1-7)-OH, respectively. The ring-opening reaction of the pyrrolidone moiety of the pGlu residue occurred to a considerably lesser extent.

Amino Acid Sequence↗
PubMed1996

Differential distribution of CaM kinases and induction of c-fos expression by flashing and sustained light in rat retinal cells.

PURPOSE: To examine the expression of c-fos proto-oncogene and phosphorylation of cAMP responsive element binding (CREB) protein in the rat retina after changes in the light-dark condition. METHODS: Rats were exposed to both steady light and flashing light and were killed at the end of light exposure. The retinas were analyzed by in situ hybridization using single-stranded RNA probes for c-fos transcripts and by immunocytochemistry using phosphoSer-133 specific CREB antiserum, anti-calcium calmodulin dependent protein (CaM) kinase II, and anti-CaM kinase IV. RESULTS: c-fos mRNA was expressed in the outer half of the inner nuclear layer (INL) and in the ganglion cell layer (GCL) after 30 minutes of sustained light. After 30 minutes of flashing light, c-fos expression also was detected in the inner border of the INL. Phosphorylated CREB immunoreactive nuclei had similar distribution after steady and flashing light. Both CaM kinase II and CaM kinase IV, which phosphorylate CREB at Ser 133 in vitro, were expressed in the GCL and in the INL. CaM kinase II, however, was localized in the inner border of the INL, whereas CaM kinase IV was distributed in the outer half of the INL. CONCLUSIONS: These results suggest that the differential expression of c-fos mRNA induced by flashing and sustained light may reflect the CREB phosphorylation by CaM kinases in a different subpopulation of retinal cells.

Animals↗