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Biomedical subjects

I Ueda

Publications and source records attributed to I Ueda.

At least 109 records · Page 6Linked to original sources
PubMed1988

Effect of surface ionization of dimyristoylphosphatidic acid vesicle membranes on the main phase-transition enthalpy and temperature.

The main phase transition of phospholipid bilayers is a property expressed by the order-disorder conformational change of the lipid tails. Nevertheless, with ionizable phospholipids, changes in the surface charge have large effects on the membrane properties. The free energy of a charged phospholipid membrane depends on the degree of ionization, area per phospholipid molecule, and the temperature. Here, the effect of surface electrostatic charges on the temperature and the enthalpy of the main phase transition of dimyristoylphosphatidic acid vesicle membranes is analyzed. A simple equation is presented that describes the relationship among the surface charge density, the phase-transition temperature, the surface area ratio between solid and liquid membranes, and the excess enthalpy. The theory indicated that the pH-induced shift in the excess enthalpy is attributable to the change in the surface area ratio between the solid and liquid membranes.

Calorimetry, Differential Scanning↗
PubMed1988

Activated carbon as a biological model: comparison between activated carbon adsorption and oil-water partition coefficient for drug activity correlation.

Octanol-water partition coefficients have been used as a principal parameter for the analysis of quantitative structure-activity relationships (QSAR). With ionized drugs, however, the correlation is not impressive. Although clinical local anesthetics exist mainly in the ionized form at physiological pH, the nerve-blocking potency is correlated with the oil-water partition coefficients of the un-ionized species. In the present report, the adsorption of 18 local anesthetics onto activated carbon surfaces was compared with oil-water partition coefficients for correlation with the minimum nerve-blocking (MBC) potency. The log octanol-water partition coefficients showed large differences between the charged and uncharged species (lidocaine: 0.49 and 1.82, procaine: -0.56 and 1.74, respectively), whereas the log carbon surface adsorbabilities showed much smaller differences (lidocaine: 3.00 and 3.04, and procaine 2.95 and 3.00, respectively). An excellent correlation was found between the log carbon surface adsorption and the log MBC values in both ionized and un-ionized drugs.

Adsorption↗
PubMed1988

Immunological studies on Crohn's disease. VII. Reduced immunologic activity in monocytes.

Studies done in our laboratories showed that monocytes in Crohn's disease (CD) have an increased phagocytic activity determined using chemiluminescence assay. To further elucidate the pathogenesis of CD, we studied the monokine production activity and the proportion of HLA-DR(+) monocytes in the peripheral blood of 16 Japanese with CD. In contrast to the phagocytic function, an impaired monokine production activity and a decreased percentage of DR(+) monocytes were evident. The number of DR(+) monocytes showed a negative correlation to CRP. These findings provide additional information on the monocyte function in CD and indicate that monocyte dysfunction may be closely linked to the pathogenesis of CD.

Biological Products↗
PubMed1988

High pressure and anesthesia: pressure stimulates or inhibits bacterial bioluminescence depending upon temperature.

Although high pressure is often viewed as a nonspecific stimulus counteracting anesthesia, pressure can either excite or inhibit biological activity depending on the temperature at application. Temperature and pressure are two independent variables that determine equilibrium quantity, e.g., the state of organisms in terms of activity and anesthesia depth. We used the light intensity of luminous bacteria (Vibrio fischeri) as an activity parameter, and studied the effects of pressure and anesthetics on the bacteria's light intensity at various temperatures. The light intensity was greatest at about 30 degrees C at ambient pressure. When the system was pressurized up to 204 atm, the temperature for maximum light intensity was shifted to higher temperatures. Above the optimal temperature for the maximal light intensity, high pressure increased the light intensity. Below the optimal temperature, pressure decreased light intensity. Pressure only shifts the reaction equilibrium to the lower volume state (Le Chatelier's principle). When the volume of the excited state is larger than the resting state, high pressure inhibits excitation, and vice versa. Halothane 0.008 atm and isoflurane 0.021 atm inhibited the light intensity both above and below the optimal temperature. When pressurized, the light intensity increased in the high temperature range but decreased in the low temperature range, as in the control. Thus, high pressure seemingly potentiated the anesthetic action at low temperatures. When the ratio of the light intensity in bacteria exposed to anesthesia and those not exposed to anesthesia was plotted against the pressure, however, the value approached unity in proportion to the pressure increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1987

Structural studies of the carbohydrate moieties of carcinoembryonic antigens.

Three samples of carcinoembryonic antigens were purified from liver metastases of primary colon cancer. The asparagine-linked sugar chains of carcinoembryonic antigens (CEA) were released as oligosaccharides by hydrazinolysis and the structures of oligosaccharides, thus obtained, was studied in combination with methylation analysis and several limited exoglycosidase digestions. All three CEAs contain approximately 25 asparagine-linked sugar chains in one molecule and about 10% of them was high mannose type. However, structural features of the outer chain moieties of the remaining complex-type sugar chains were different by CEA samples. The complex-type sugar chains were mono-, bi-, tri-, and tetraantennary with Man alpha 1----6(+/- GlcNAc beta 1----4)(Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4(+/- Fuc alpha 1----6)GlcNAc as their cores, half of which were bisected; 86% of their proximal N-acetylglucosamine was fucosylated. The major outer chains in two samples were N-acetyllactosamine and Gal beta 1----4(Fuc alpha 1----3)GlcNAc (X-antigenic determinant) and the remaining one sample contained Fuc alpha 1----2Gal beta 1----4(Fuc alpha 1----3)GlcNAc (Y-antigenic determinant) as an additional major outer chain. Furthermore, small amounts of type 1 chain and Lea antigenic determinant were found in some samples. Acidic oligosaccharides consisted of sialic acid containing fractions and sialidase-resistant fractions, and their contents seemed to be in a reciprocal relationship. Sialic acid was linked at the C-3 and C-6 positions of the nonreducing terminal galactose residues of the outer chains.

Asparagine↗
PubMed1987

Origin of calcium-induced minimum in bulk compressional modulus of lipid membranes. Configurational entropy of adsorbed Ca2+.

Addition of Ca2+ to a dipalmitoylphosphatidylcholine lamellar system decreases the bulk compressional modulus (increases compressibility) of the membrane (S. Aruga, R. Kataoka and S. Mitaku, Biophys. Chem. 21 (1985) 265). The bulk modulus was reported to show a minimum value at 10 mM Ca2+ within the temperature range 20-45 degrees C. In the present report, the occurrence of this minimum in the bulk modulus is explained quantitatively as a result of fluctuation in the number of Ca2+ adsorbed onto the lipid bilayer surface. From this theory, the change in apparent molal volume of Ca2+ upon surface adsorption is estimated to be 5.7 cm3 mol-1, which appears to be a reasonable value. The number of adsorbed Ca2+ at the concentration where the bulk modulus assumes the minimum value is half of the number of allowable adsorption sites on lipid membranes. The configurational entropy of the adsorbed Ca2+ attains a maximum at the minimum point.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Production and isolation of recombinant somatomedin C.

High-level production of a growth promoting peptide hormone somatomedin C (insulin-like growth factor I) has been achieved using recombinant DNA techniques in Escherichia coli. We found a new structural protein, designated as LH, to stabilize somatomedin C in vivo, and constructed expression vectors for somatomedin C fusing to LH through a methionine and through a tryptophan, respectively. Each of the fused proteins was produced at approximately 4.5 X 10(5) molecules per single E. coli cell and comprised more than 20% of the total cellular proteins. Somatomedin C was obtained in high yield by limited cyanogen bromide degradation of the methionine-type fused protein, in spite of somatomedin C itself having a Met at the 59th position, followed by renaturation of the resultant reduced peptide. The tryptophan-type fused protein was also converted to the peptide hormone by treating with 3-bromo-2-nitrophenylsulphenyl skatole or N-chlorosuccinimide. The recombinant somatomedin C obtained by these procedures was identical with the native one in amino acid sequence as well as in biological activity of stimulation of DNA synthesis in BALB/c 3T3 cells.

Chromatography, High Pressure Liquid↗
PubMed1987

Direct expression of a synthetic somatomedin C gene in Escherichia coli by use of a two-cistron system.

Direct expression of a growth-promoting peptide hormone, somatomedin C/insulin-like growth factor I, which is quite difficult due to the instability of somatomedin C itself in Escherichia coli, has been achieved by the use of a two-cistron system. Assuming that basic somatomedin C might be stabilized by forming a complex with an acidic polypeptide, we constructed synthetic genes consisting of two cistrons; an acidic 93-amino-acid polypeptide was coded in the first cistron followed by a synthetic somatomedin C gene in the second cistron. The chain termination codon for the first polypeptide overlapped the initiation codon for the second polypeptide in the intercistronic region, as occurs in the polycistronic E. coli tryptophan operon, whose products are associated in multi-subunit enzyme complexes. In the expression of the resulting genetic system, recombinant somatomedin C associated with the acidic polypeptide was accumulated to high levels in the cells. After treatment of the product with acetic acid to dissociate the two components, the recombinant somatomedin C was isolated in a yield of 4.0 mg from a liter of culture broth at A600 = 1.6. It was determined to be Met-somatomedin C by chymotryptic mapping as well as amino-terminal analysis.

Amino Acid Sequence↗
PubMed1987

Bacterial synthesis of recombinant alpha-human atrial natriuretic polypeptide.

The high-level synthesis of alpha-human atrial natriuretic polypeptide hormone in Escherichia coli has been achieved based on the idea that the yield of a small, basic and unstable polypeptide, such as the natriuretic polypeptide, would be improved by fusion with an appropriate protective polypeptide to construct a neutral fused polypeptide. We prepared an expression vector, pCLaHtrp3t, coding a neutral polypeptide containing 130 amino acid residues in which the polypeptide hormone was fused to a newly designed protective polypeptide through lysine as an enzymatically cleavable residue. The fused polypeptide was synthesized at the high level of 32% of total cellular proteins and at 4.7 X 10(6) molecules per single cell. It was recovered as cellular insoluble fraction and purified to homogeneity. For the isolation of the peptide hormone from the resultant fused polypeptide, Achromobacter protease I, a lysine-specific endopeptidase was used, because it has sufficient activity even in 8 M urea. The recombinant natriuretic polypeptide was indistinguishable from native alpha-human atrial natriuretic polypeptide as regards amino acid sequence as well as biological activity.

Amino Acid Sequence↗
PubMed1987

Fourier transform infrared studies on phospholipid hydration: phosphate-oriented hydrogen bonding and its attenuation by volatile anesthetics.

Water-phospholipid (dimyristoylphosphatidylcholine) interaction was analyzed in a water-in-oil(benzene) reversed micellar system using Fourier transform infrared spectroscopy, and the effects of inhalation anesthetics (halothane, enflurane, chloroform, and carbon tetrachloride) on the interaction were studied. The O-H stretching frequency, representing water, increased from 3369 cm-1 to a steady 3430 cm-1 when the water/phospholipid mole ratio exceeded 18. The value did not quite reach the frequency of free water of 3490 cm-1 at the water/phospholipid mole ratio of 30. The O-H bending frequency of water did not appear until the water/phospholipid mole ratio exceeded 9. The P=O stretching frequency in the polar head group of unhydrated dimyristoylphosphatidylcholine was 1262 cm-1 and decreased with the addition of water, reaching a steady value of 1238 cm-1 at the water/phospholipid mole ratio of 9. However, the (CH3)3N+ stretching of the choline head, as well as the C-H stretching of the hydrocarbon tail and the C=O stretching of the ester linkage, showed little change by the addition of water. The present results suggest that the primary hydration site of dimyristoylphosphatidylcholine is the phosphate moiety, and up to 18 water molecules are restricted at the polar head group. Apparently, the choline head has a minor role in the hydration of phospholipids despite the positive electrostatic charge. Among the water molecules interacting with the phospholipid head group, about 9 water molecules are strongly bound. The water content in the micelles correlated linearly with the ratio of the absorbance band area between O-H and C=O stretching. The addition of polar anesthetics (halothane, enflurane, and chloroform) increased the O-H stretching frequency and elevated the ratio of the absorbance band area between O-H and C=O stretching, implying that the anesthetics released the structured water molecules bound at the phospholipid-water interface. The anesthetics disrupted the hydrogen bond between the phosphate moiety of the phospholipid and water. Although apolar carbon tetrachloride also released bound water molecules, the magnitude was less than that of the polar anesthetics, as expected. The anesthetics did not affect the C-H stretching or C=O stretching bands, indicating that the disordering action upon the hydrocarbon core of phospholipid membranes is minimal at low water content. These results support our view that the primary site of action of inhalation anesthetics is the membrane-water interface, releasing bound water molecules.

Anesthetics↗
PubMed1986

Miscibility of phosphatidylcholine binary mixtures in unilamellar vesicles: phase equilibria.

Miscibility among phospholipids with different lipid chain-lengths or with different head groups has attracted a number of research efforts because of its significance in biological membrane structure and function. The general consensus about the miscibility of phosphatidylcholines with varying lipid chain-lengths appears to be that binary mixtures of phospholipids with a difference of two carbon atoms in the lipid chain mix well at the main phase transition. Miscibility between phosphatidylcholines with differences of four carbon atoms appears to be inconclusive. Previous reports on the phase transition of binary phospholipid mixtures are concerned mainly with multilamellar vesicles and are mostly limited to the main transition. In the present study, unilamellar vesicles were used and miscibility in binary systems between dimyristoyl-, dipalmitoyl- and distearoyl-phosphatidylcholines at pretransition as well as main transition temperatures was evaluated by constructing phase diagrams. Two methods were used to monitor the phase transitions: differential scanning microcalorimetry and optical absorbance methods. The optical method has the advantage that unilamellar vesicles of dilute phospholipid concentrations can be used. The liquidus and solidus phase boundaries were determined by the onset temperature of heating and cooling scans, respectively, because the completion temperature of a phase transition has no meaning in binary solutions. Dimyristoyl- and distearoyl-phosphatidylcholines, where the difference in the lipid chain-length is four carbon atoms, mixed well even at pretransition temperature.

Kinetics↗
PubMed1986

Do anesthetics fluidize membranes?

The so-called membrane fluidizing effect of anesthetics as a cause of anesthesia has been questioned, mainly because the magnitude of the increase in "fluidity" is insignificant at clinically relevant anesthetic pressures. However, the term "fluidity" has an unfortunate history of being misrepresented in membrane biology. It is often expressed as the ease of movement of probe molecules incorporated into the hydrophobic region of the membrane, thereby representing the property of the microenvironment where the probe molecules reside. In surface chemistry, "membrane fluidity" means inverse viscosity. Membrane viscosity is an integral property of a total membrane (not a part of membrane), and membrane molecules must dislocate and flow against resistance. The ease of motion of probe molecules, therefore, is not fluidity, and is now expressed by the order parameter. The present study measured the effect of halothane on surface viscosity of a phospholipid monolayer spread on a water surface by an oscillating pendulum surface viscometer. The results indicate a significant decrease of about 31% in the surface viscosity by the clinical pressure of halothane; anesthetics do fluidize membranes. Two factors contribute to the surface viscosity of the lipid monolayer; the property of the membrane proper (association between phospholipid molecules) and dragging of water (association between phospholipid and water molecules). The association between phospholipid molecules is in large part related to the order parameter. The fact that anesthetics show little effect on the order parameter, whereas halothane shows a significant effect on the membrane viscosity, indicates that halothane releases surface-bound water. It is postulated that the primary effect of anesthetics on membranes is to weaken the lipid-water interaction forces.

Anesthetics↗
PubMed1986

Biosynthetic somatomedin C (SM-C/IGF-I) increases the length and weight of Snell dwarf mice.

An Escherichia coli derived somatomedin-C/IGF-I preparation (rec-IGF-I) with an amino acid sequence identical to the natural IGF-I derived from human plasma, increases body length and weight, as well as the growth of several organs of Snell dwarf mice, when administered for 4 wk. After 2 wk of treatment rec-IGF-I (22.2 micrograms/day) induced a significant increase over buffer treated controls, to a comparable degree as obtained with bacterially synthesized human growth hormone (bhGH; 8.4 micrograms/day). The weight/length ratio of rec-IGF-I and bhGH-treated dwarf mice after 4 wk of treatment were not significantly different. A significant increase over controls was obtained with both preparations. Organs with increased weights after bhGH treatment (brain; submandibular salivary glands; heart, liver, kidneys, thymus, and spleen) were also heavier after rec-IGF-I. Significance was only reached for the kidneys and the spleen and the musculus quadriceps femoris. Organ weights expressed as a percentage of body weight of bhGH and rec-IGF-I treated dwarfs were similar except for the relative weight of the heart of the bhGH group, which was significantly increased compared to the controls and the rec-IGF-I group. These data resolve the issue as to whether or not pure SM-C/IGF-I will induce growth in length and demonstrate the usefulness of recombinant IGF-I in the studies of growth regulation.

Animals↗