Biomedical subjects

K Ohki

Publications and source records attributed to K Ohki.

At least 73 records · Page 4Linked to original sources

PubMed1994

Study on the castability of Co-Cr alloy for cast plates. Part 4. Effects of sectional area, number of sprues and alloy components on castability.

Co-Cr alloy is used more frequently than Ni-Cr alloy as a nonprecious alloy for cast plates in Japan. Titanium with good biocompatibility has often been contained in the composition of this Co-Cr alloy. However, since the melting temperature of Co-Cr alloy is very high, about 1300 degrees C, and it oxidizes easily, a vacuum-pressure casting machine capable of melting this alloy in a reduced atmosphere has recently been developed. In this study, using the vacuum-pressure casting machine, the possible effects of sectional area and the number of sprues attached to the cast plate wax pattern, as well as the alloy components, on the castability of three kinds of Co-Cr alloy containing titanium were examined. It was found that all of these parameters had significant effects on Co-Cr alloy castability.

Chromium Alloys↗

PubMed1994

The existence of protein kinase C in cone photoreceptors in the rat retina.

We examined the localization of protein kinase C (PKC) in the rat retina, using a monoclonal antibody against PKC. The PKC immunoreactivities were localized in bipolar cells as reported previously, and also in outer and inner segments (OS and IS) of photoreceptor cells. As the PKC immunoreactive OS and IS of photoreceptors were very few in number, we hypothesized that these were of cone photoreceptors. We then examined whether the PKC immunoreactive OS and IS were bound by peanut agglutinin which was shown to bind specifically to cone OS and IS. Almost all of the PKC immunoreactive OS and IS showed PNA binding.

Animals↗

PubMed1993

Pathophysiological characteristics of cutaneous microcirculation in patients with liver cirrhosis: relationships to cardiovascular hemodynamics and plasma neurohormonal factors.

To elucidate pathophysiological characteristics of the peripheral circulation in liver cirrhosis, cutaneous microcirculation was analyzed at the finger, palm, toe, and arch of the foot using laser Doppler spectroscopy in 19 patients with liver cirrhosis, and the results were correlated with cardiovascular hemodynamics (n = 10) and plasma neurohormonal factors (n = 8). Cutaneous blood flow at each area was all significantly reduced (P < 0.001, < 0.05, < 0.01, < 0.001, respectively) in patients with liver cirrhosis compared to those in normals (n = 20). Cutaneous blood mass was also significantly reduced (P < 0.05, < 0.01, < 0.001, respectively) except at the arch of foot in patients with liver cirrhosis. There were significant correlations between finger cutaneous blood flow and systemic vascular resistance (r = -0.73, P < 0.05), plasma norepinephrine level (r = -0.84, P < 0.01), plasma renin activity (r = -0.77, P < 0.01), plasma concentrations of aldosterone (r = -0.76, P < 0.05) and angiotensin II (r = -0.76, P < 0.05), between palm blood flow and plasma vasoactive intestinal polypeptide concentration (r = 0.83, P < 0.05). From these results and our previous data demonstrating increased forearm muscular blood flow in patients with liver cirrhosis, increases in arteriovenous anastomotic flow and the contribution of neurohormonal factors will represent pathophysiological mechanisms for these changes.

Adult↗

PubMed1993

Abnormal cutaneous vasomotion and reduced cutaneous blood mass remain in congestive heart failure even with normalized cardiovascular hemodynamics.

To elucidate the pathophysiologic role of cutaneous microcirculation in congestive heart failure, finger cutaneous microcirculation was analyzed in 17 patients with acute heart failure (AHF) and 12 patients with hemodynamically compensated heart failure (c-HF) by using laser Doppler spectroscopy; the results were correlated with simultaneously obtained cardiovascular hemodynamics. Mean finger cutaneous blood flow in AHF was significantly lower compared with c-HF (p < 0.01) and control (n = 20, p < 0.001). Mean finger cutaneous blood mass was significantly reduced in both AHF (p < 0.01) and c-HF (p < 0.01) compared with control. Frequency of characteristic giant concave waves indicating sudden occurrence of flow reduction (B wave) was significantly higher in AHF (p < 0.01) and c-HF (p < 0.05) than that in control. Frequency of B waves correlated significantly with pulmonary capillary wedge pressure (PCWP) (r = 0.73, p < 0.01) and pulmonary artery systolic pressure (r = 0.54, p < 0.05). When changes after medical treatments were compared there were significant correlations between changes in B-wave frequency and changes in PCWP (r = 0.89, p < 0.01) and changes in finger cutaneous blood flow and changes in total systemic peripheral resistance (r = -0.75, p < 0.05). Cutaneous microcirculation in AHF was characterized by decreased finger cutaneous blood flow and finger cutaneous blood mass and prominent B waves, which reflected abnormal vasomotion activity. B-wave prominence and reduced finger cutaneous blood mass remained in c-HF even with normalized cardiovascular hemodynamics.

Adult↗

PubMed1993

Characterization of a unique scrambled peptide derived from the CD4 CDR3-related region which shows substantial activity for blocking HIV-1 infection.

We have previously identified CD4 peptides that exhibited blocking activity on human immunodeficiency virus type 1 (HIV-1) infection, i.e. CD4(68-130) and CD4(66-92) which include the region corresponding to the third complementarity-determining region of IgG. Here we describe a unique peptide derived from CD4(66-92), altered in amino acid sequence but not in composition, which was found to have increased anti-HIV-1 activity. The acidic amino acid residues in this scrambled peptide, S1, localized at the N-terminus, while in the native peptide they clustered at the C-terminus. On the other hand, a second scrambled peptide, S2, in which the acidic amino acid residues were fully dispersed, did not show any anti-HIV-1 activity. However, we could not identify any correlation between CD4(66-92) and S1 peptides by their hydrophobic or circular dichroism spectrum analyses. The results provide insight into the mechanisms of HIV-1 gp120 and CD4 interaction and may be useful as a new approach to AIDS therapy.

Amino Acid Sequence↗

PubMed1993

Persistently human immunodeficiency virus type 1-infected T cell clone expressing only doubly spliced mRNA exhibits reduced cell surface CD4 expression.

Several cell clones possessing the human immunodeficiency virus type 1 (HIV-1) genome, consisting of an almost full-length DNA sequence, were isolated by limiting dilution of the clonal cell line M10 derived from MT-4 that survived infection with HIV-1 vpr mutant (M10/vpr-). One of the isolated clones (termed Vpr-1) expressed only doubly spliced mRNA, but not unspliced or singly spliced mRNA. Western blots of Vpr-1 revealed the presence of the nef translation product, although no expression of major structural genes such as gag, pol, and env was detected by indirect immunofluorescence and assay of reverse transcriptase activity. These HIV-1 phenotypes differed greatly from those of the original M10/vpr-, most of which expressed major structural HIV-1 proteins. Despite undetectable levels of env expression in Vpr-1, CD4 antigens were greatly down-modulated on the surface without alteration of steady-state levels of CD4 mRNA expression, similar to M10/vpr-. These HIV-1 phenotypes in Vpr-1 did not change after the treatment of the cells with both phorbol 12-myristate 13-acetate and phytohemagglutinin. Therefore, the abnormal HIV-1 life cycle in Vpr-1 seems to be due to some viral factor(s), as well as cellular factors. Thus, Vpr-1 could be a useful model for understanding one HIV-1 latent form.

Base Sequence↗

PubMed1993

Serum-mediated modification of proliferation in factor-dependent macrophage cell lines.

Previously we described that bacterial lipopolysaccharide (LPS) promoted DNA synthesis and supported the cell viability in the factor-dependent macrophage cell lines BDM-1 and BDM-1W3 in the absence of colony-stimulating factor (CSF). To further examine this phenomenon, in the present study we examined the effects of serum on CSF-dependent proliferation and LPS-induced DNA synthesis in BDM-1 and BDM-1W3 cells. Fetal calf serum (FCS) was required for CSF-dependent proliferation in BDM-1 and BDM-1W3 cells. FCS was also required for LPS-induced DNA synthesis in BDM-1W3 cells. However, at concentrations higher than 0.2%, FCS inhibited LPS-induced DNA synthesis in BDM-1W3 cells in a dose-dependent manner. To obtain the inhibitory activity in FCS (FCS-In) for LPS-induced DNA synthesis, FCS was fractionated by gel filtration chromatography using Sephacryl S-200, chromatography on DEAE-Sephacel, and affinity chromatography on heparin-Sepharose. FCS-In was eluted in the void volume peak from a Sephacryl S-200 column, indicating that FCS-In has a molecular weight of more than 250,000. The molecular weight of FCS-In was apparently 270,000 as determined by SDS-polyacrylamide gel electrophoresis (PAGE) under non-reducing conditions. Upon reduction, four components became detectable with apparent molecular weights of 170,000, 110,000, 67,000, and 30,000. The inhibitory activity in FCS-In material was inactivated by heat and trypsin treatment. The partially purified FCS-In inhibited LPS-induced DNA synthesis in BDM-1W3 cells, but did not inhibit the proliferation of BDM-1W3 cells induced by IL-3, granulocyte-macrophage CSF (GM-CSF), or macrophage CSF (M-CSF).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Basic studies on visible light-cured resin as a denture base. Part 17. Transverse and tensile strengths of repaired denture base resin using a trial repair resin.

Trial production of a visible light-cured repair resin (powder/liquid type, TPL) as a denture base resin was carried out using cyclophosphazene monomer, and then the transverse and tensile strengths of the repaired specimens were examined. As a control, Triad Gel (TRI) was used. In the transverse strength test, TPL showed values of 507-470 kgf/cm2, which were about double those of TRI. As for tensile strength, TPL showed values of 329-268 kgf/cm2, and higher values were obtained in comparison with TRI, especially after 30 days of water immersion, when the values were doubled. The durability of TPL was favorable in comparison with TRI.

Composite Resins↗

PubMed1993

Study on the castability of Co-Cr alloy for cast plates. Part 3: Effects of alloy fusion temperature and the heating temperature of the cast ring.

Co-Cr alloy is used more frequently than Ni-Cr alloy as a non-precious alloy for cast plates in Japan. However, since the melting temperature of Co-Cr alloy is very high, about 1300 degrees C, and since it oxidizes easily, a vacuum-pressure casting machine capable of melting this alloy in a reduced atmosphere has recently been developed. Using this machine, the effects of fusion temperature and the heating temperature of the cast ring on the Co-Cr alloy were studied. It was found that in the vacuum-pressure casting method, both the fusion temperature of the Co-Cr alloy and the heating temperature of the cast ring had a significant effect (p < 0.01) on the castability of the Co-Cr alloy.

Chromium Alloys↗

PubMed1992

Effects of poly(L-lysine) on the structural and thermotropic properties of dipalmitoylphosphatidylglycerol bilayers.

The effects of poly(L-lysine) on the structural and thermotropic properties of dipalmitoylphosphatidylglycerol (DPPG) bilayers were studied with differential scanning calorimetry (DSC), X-ray diffraction and freeze-fracture electron microscopy. For thermal behavior, in the DPPG/poly(L-lysine) system the main transition temperature rises to 45.7 degrees C and the pretransition disappears in opposition to pure DPPG vesicles. An additional transition appears approximately at 36 degrees C for the DPPG/poly(L-lysine) system after incubation at 4 degrees C for two months. The incubated sample gives a X-ray diffraction pattern having several additional reflections in the range of 0.2-0.9 nm at 15 degrees C. These results suggest that even in the presence of poly(L-lysine) the DPPG bilayers form the subgel (Lc) phase after the long incubation at a low temperature. The X-ray diffraction measurements indicate that the structure of the Lc phase for DPPG/poly(L-lysine) system is different from that of pure DPPG bilayers. On the other hand, in the gel (L beta') phase, the wide-angle X-ray diffraction pattern suggests that the presence of poly(L-lysine) hardly affects the packing of hydrocarbon chains in the DPPG bilayers. The small-angle X-ray diffraction and freeze-fracture electron microscopy exhibit that the DPPG/poly(L-lysine) system forms a tightly packed multilamellar structure in which the poly(L-lysine) is intercalated between the subsequent DPPG bilayers.

Calorimetry, Differential Scanning↗

PubMed1992

Luminescence quenching by nitroxide spin labels in aqueous solution: studies on the mechanism of quenching.

The mechanism of luminescence quenching by spin labels was investigated in aqueous solution by steady-state and time-resolved luminescence techniques. Water-soluble nitroxide radicals strongly quenched the luminescence emitted by Tb3+ chelates and by fluorescein, either free or conjugated to proteins. The following features of the quenching reaction were established: (I) the rate constant for quenching of triplet-state Tb3+ by nitroxides was about 4 orders of magnitude smaller (ca. 10(5) M-1 s-1) than those of the singlet-state probes; (II) the quenchers reduced the excited-state lifetime of both probes; (III) the rate constants for quenching of both probes were found to be apparently independent of the temperature (between 6 and 42 degrees C) and viscosity (up to 60 mPa.s) of the solutions; (IV) both singlet and triplet quenching rates were sensitive to solvent polarity; (V) there is a small but significant spectral overlap between the absorption band of weekly absorbing nitroxide radicals and the emission spectra of luminophores, the extent of which, however, does not correlate with the extent of quenching; (VI) the quenching rate declines sharply with an increasing luminophore to nitroxide distance. The distance dependence of the quenching rate showed a satisfactory fit to an exponential function. These findings indicate that the quenching reaction is dominated by an electron exchange between the excited singlet- or triplet-state luminophore and the nitroxide radical rather than controlled by diffusional properties of the reactants.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic N-Oxides↗

PubMed1992

Monoclonal antibodies to a CD4 peptide derivative which includes the region corresponding to an immunoglobulin CDR3: evidence of the involvement of pre-CDR3-related region in HIV-1 and host cell interaction.

A CD4 peptide of amino acid residues 68-130 [CD4(68-130)], which had the capacities to inhibit HIV-1 replication and HIV-1-induced syncytium formation, was used as an immunogen for the preparation of mAb. The mAbs prepared were classified into at least five types (I-V) in terms of their recognition sites by ELISA using various kinds of smaller CD4 peptides. Among them, the type I mAb no. 35 recognizing amino acid residues 72-84, which lies just before the region corresponding to an immunoglobulin third complementarity-determining region (CDR3), showed the strongest effects in reducing both HIV-1 infection and HIV-1-induced syncytium formation, although a large amount of no. 35 mAb was necessary to reduce such HIV-1 activities compared with those of anti-Leu-3a and OKT4A mAbs which recognize CD4 epitopes near a portion corresponding to an immunoglobulin CDR2. Western blot analysis showed that the reactivities of CD4 molecule in CD4-positive cells or sCD4 molecule with types I-V mAbs were stronger than that with anti-Leu-3a mAb. Flow cytometry showed that no. 35 mAb was faintly reactive with native CD4 molecule on cell surface at the concn showing the inhibitory effects on HIV-1 infection and syncytium formation. In addition, a smaller peptide CD4(66-92), one of the good epitope peptides for no. 35 mAb, also showed strong inhibitory effect on HIV-1 infection as well as a weaker inhibitory effect on syncytium formation. These results suggest that, in addition to the CD4 CDR2-related region, the pre-CDR3-related region is also involved in the early events of the interactions between the host cell and HIV-1.

Amino Acid Sequence↗

PubMed1992

Major core proteins, p24s, of human, simian, and feline immunodeficiency viruses are partly expressed on the surface of the virus-infected cells.

We have previously shown the expression of human immunodeficiency virus type 1 (HIV-1) major gag protein, p24, on the surface of persistently HIV-1-infected cells by using murine monoclonal antibodies (mAb). We now report that the cell surface gag p24 antigen expression is a universal phenomenon among HIV-1, simian immunodeficiency virus (SIV), and feline immunodeficiency virus (FIV). The mAbs prepared by immunization with purified HIV-1 particles were used as antibodies cross-reactive to HIV-1 and SIVagmp24 antigens. The mAbs to FIV p24 were raised against the gag precursor 50 kDa protein of FIV, which was expressed by Baculovirus vector. The p24 antigen expression on the cell surface was detectable in certain combinations of virus-host cell systems in all of these viruses. Since these p24 regions of the animal viruses seem to play as important a role in cell-mediated immunity as that of HIV-1, the p24 applicability as a candidate epitope for vaccine development could be evaluated in those animals.

Animals↗

PubMed1992

Cells surviving infection by human immunodeficiency virus type 1: vif or vpu mutants produce non-infectious or markedly less cytopathic viruses.

Under conditions in which a clonal cell line (M10) isolated from a human T cell lymphotrophic virus type I-transformed MT-4 cell line was completely killed by infection with wild-type human immunodeficiency virus type 1 (HIV-1), equivalent M10 cells survived infection with HIV-1 vif, vpr or vpu mutant virus after transient cytopathic effects. Several cell clones, which were isolated from the proliferating M10 cells after infection with vif and vpu mutant viruses (M10/vif- and M10/vpu-), had heterogeneous HIV-1 phenotypes in terms of HIV-1 antigen expression, their syncytium forming capacity, reverse transcriptase activity and the infectivity of HIV-1 particles produced. When the replication kinetics of the HIV-1 particles produced were assayed in M10 cells, the clones could be classified into three types, i.e. type I producing non-infectious HIV-1, type II producing infectious HIV-1 with low replicative ability and type III producing infectious HIV-1 with a replicative ability similar to that of wild-type HIV-1. HIV-1 major viral cell proteins and virus particle fractions were almost typical in types II and III but not in type I. Electron microscopic examination of particles released by I, II and III clones revealed rare defective, predominantly defective and essentially normal virions, respectively. Northern and Southern blot analyses revealed no apparent deletion in the proviral DNA and mRNA prepared from these clones, except in the case of type I and II clones isolated from M10/vpu- which contained large deletions in the mRNAs for gag and gag-pol proteins. Thus, M10 cells surviving infection with HIV-1 vif or vpu mutants are heterogeneous, persistently expressing HIV-1 antigens and producing non-infectious or less cytopathic virus.

Blotting, Northern↗

PubMed1992

Human immunodeficiency virus type 1 (HIV-1) superinfection of a cell clone converting it from production of defective to infectious HIV-1 is mediated predominantly by CD4 regions other than the major binding site for HIV-1 glycoproteins.

A cell clone, L-2, which produces non-infectious doughnut-shaped human immunodeficiency virus type 1 (HIV-1) particles, was permissive for HIV-1 superinfection, which resulted in the production of infectious particles. The superinfection showed slow kinetics compared with primary HIV-1 infection of M10 cells, the parent of the L-2 cell clone. Inhibition studies on the superinfection of L-2 cells using several CD4-related reagents showed that the CD4 molecule was an essential component of the receptor for superinfection. Strong inhibitory effects were obtained using CD4 peptides such as CD4(68-130), which includes a portion homologous to the immunoglobulin third complementarity-determining region (CDR3), as well as recombinant soluble CD4. In contrast, a CD4(45-60) peptide, which includes most of the CDR2-related region, was not effective, although the Leu-3a monoclonal antibody (MAb), which recognizes a site near the CDR2-related region, did slightly, but significantly, delay the superinfection kinetics. Comparative flow cytometry of L-2 and M10 cells revealed that the cell surface of L-2 cells despite expressing HIV-1 env protein, reacted slightly with OKT4 or anti-CD4(68-130) MAb, but not with Leu-3a or OKT4A MAb. In contrast, no reaction was detected with any of these anti-CD4 MAbs on the surface of another HIV-1 superinfection-resistant cell clone, MOLT-#8IIIB-14, which expresses HIV-1 env proteins but does not produce infectious HIV-1 particles. These results strongly suggest that expression of the CD4 major receptor site for primary HIV-1 infection is preferentially decreased on the surface of L-2 cells, but that the OKT4 epitope and the nearby region corresponding to immunoglobulin CDR3 remain exposed on the cell surface. Consequently, the CD4 CDR3-related region could play a major role as the receptor for the superinfection reported here.

Binding Sites↗

PubMed1992

Bactericidal activities of rat defensins and synthetic rabbit defensins on Staphylococci, Klebsiella pneumoniae (Chedid, 277, and 8N3), Pseudomonas aeruginosa (mucoid and nonmucoid strains), Salmonella typhimurium (Ra, Rc, Rd, and Re of LPS mutants) and Escherichia coli.

Rat defensins were purified and tested for in vitro bactericidal assay against gram-positive and gram-negative bacteria. Staphylococcus aureus (209P, Cowan I, Smith diffuse and Smith compact) were resistant to defensins, whereas Staphylococcus epidermidis, Staphylococcus saprophyticus, Micrococcus lysodeikticus and Bacillus subtilis were less sensitive. Gram-negative bacteria, such as Pseudomonas aeruginosa (mucoid and K) and Klebsiella pneumoniae (Chedid, 277, and 8N3 which were heavily capsulated, moderately capsulated and noncapsulated, respectively) were all very sensitive to defensins and killed within 20 min. Escherichia coli was moderately sensitive and the rough mutants of lipopolysaccharide (LPS) of Salmonella typhimurium LT2, such as Ra, Rc, Rd, and Re were equally sensitive to defensins, being killed within 40 min. Lysozyme did not show any bactericidal activity except against M. lysodeikticus and B. subtilis, whereas it enhanced the bactericidal activity of defensins against P. aeruginosa, E. coli, and K. pneumoniae and suppressed the killing activity of defensins against S. typhimurium and S. aureus. With regard to the three synthetic rabbit defensins, NP1, NP4, and NP5, NP1 showed strong bactericidal activity against K. pneumoniae 277, comparable to that of rat defensins. Neither NP4 nor NP5 showed any bactericidal activity, while NP5 rather enhanced the bactericidal activity of NP1 against K. pneumoniae 277.

Animals↗

PubMed1992

Lung traction causes an increase in plasma prostacyclin concentration and decrease in mean arterial blood pressure.

The effects of lung traction on arterial blood pressure and plasma prostacyclin concentrations were studied in five patients undergoing partial pneumonectomy or lobectomy. After manual traction of a lung segment, mean arterial blood pressure decreased from 77 +/- 5 mm Hg (mean +/- SEM, before lung traction) to 59 +/- 5 mm Hg. The concentrations of 6-keto prostaglandin F1 alpha (a stable breakdown product of prostacyclin) increased significantly from 46 +/- 6 pg/mL (mean +/- SEM, before thoracotomy) to 593 +/- 91 pg/mL. Four of five patients showed facial flushing and palmar erythema. Arterial blood pressure returned to pretraction value, and both the facial flushing and palmar erythema disappeared within 30 min after lung traction. These results suggest that traction of the lung stimulates release and/or production of prostacyclin, which results in facial flushing, palmar erythema, and decrease in arterial blood pressure.

Adolescent↗

PubMed1992

Differential effects of bacterial lipopolysaccharide and interferon-gamma on proliferation of two factor-dependent macrophage cell lines.

We examined the responsiveness of two factor-dependent macrophage cell lines, BDM-1 and its subclone, BDM-1W3, to bacterial lipopolysaccharide (LPS), interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) for their growth. LPS inhibited the M-CSF-dependent proliferation of BDM-1 cells but it had no effect on the proliferation of BDM-1W3 cells. LPS promoted DNA synthesis and supported the cell viability in the absence of CSFs in BDM-1 and BDM-1W3 cells, suggesting that the intracellular signals are transduced from the interaction of LPS with LPS-binding sites in BDM-1W3 cells as well as in BDM-1 cells. IFN-gamma inhibited the proliferation of BDM-1 and BDM-1W3 cells. However, BDM-1 cells were more susceptible to the inhibitory effect of IFN-gamma than BDM-1W3 cells. In contrast to LPS and IFN-gamma, TNF-alpha did not inhibit the proliferation of BDM-1 and BDM-1W3 cells. These cell lines should be useful for studying the regulatory mechanisms in CSF-dependent macrophage proliferation.

Animals↗