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W G Wu

Publications and source records attributed to W G Wu.

36 records · Page 2Linked to original sources
PubMed1991

Preliminary crystallographic analysis of cardiotoxin V with major fusion activity from Taiwan cobra (Naja naja atra) venom.

Crystals of a cardiotoxin from Taiwan cobra venom have been obtained by the vapor diffusion method using methyl pentanediol as precipitant. The crystals belong to the hexagonal space group P6(1)22 (or P6(5)22), with cell dimensions a = b = 47.5 A, c = 111.3 A, alpha = beta = 90 degrees and gamma = 120 degrees and diffract to a resolution of 2.2 A. There is one molecule per asymmetric unit and the solvent content is estimated to be 53%.

Cobra Cardiotoxin Proteins↗
PubMed1991

Phenylarsine oxide inhibits insulin-dependent glucose transport activity in rat soleus muscles.

Phenylarsine oxide (PAO) is known to block insulin-stimulated glucose transport activity in 3T3 L1 adipocytes at a post-receptor step. Herein, we demonstrate that, at right concentration, PAO also inhibits insulin activation of glucose uptake in rat soleus muscles but does not affect basal level of uptake. In control experiments, insulin stimulation of 2-deoxy-D-glucose uptake is about 400% of that of the control level. After PAO treatment, the stimulation reduces to 150% of the control. Since the intracellular level of ATP remains unchanged after PAO treatment, when measured by phosphorus-31 nmr spectroscopy, this inhibition is not due to depletion of ATP pool size. Moreover, PAO does not affect autophosphorylation of the insulin receptors purified from rat soleus muscles, implying that the PAO blockage of insulin-dependent glucose uptake in soleus muscles also may be post-receptor.

Adenosine Triphosphate↗
PubMed1991

Fusion of sphingomyelin vesicles induced by proteins from Taiwan cobra (Naja naja atra) venom. Interactions of zwitterionic phospholipids with cardiotoxin analogues.

Egg sphingomyelin vesicles were used to assay aggregation/fusion activities of proteins from Taiwan (Naja naja atra) venom to avoid the problem of phospholipase A2 contamination during protein purification. It led to the identification of a new cardiotoxin (CTX) analogue protein (CTX V) with major aggregation/fusion, but few hemolysis, activities. On the contrary, cardiotoxin (CTX III) induced significant hemolysis of human red blood cells but exhibited few aggregation/fusion activities. To study the structure/activity relationship of these CTX-induced processes, the amino acid sequence of CTX V was determined and its aggregation/fusion activity was compared with that of CTX III by transmission electron microscopy, quasielastic laser light scattering, differential scanning calorimetry, and fluorescence spectroscopy. The results show that the CTX-induced fusion process at temperatures slightly above that of the gel to liquid-crystalline phase transition of sphingomyelin vesicles can ultimately convert small sonicated vesicles into large fused vesicles with sizes of 1-2 microns. The abilities of CTX V to induce the leakage of sphingomyelin vesicles content and to cause the fusion of vesicles are approximately 10-fold higher than those of CTX III. Based on the CTX structures determined in the present and other studies, it is suggested that the amino acid residue X within the well conserved sequence of -Cys-Pro-X-Gly-Lys-Gln-Leu-Cys- plays a role in the interaction of CTX with lipid molecules. The lipid phase transition could further enhance the protein-lipid interaction in the process leading to the fusion of vesicles.

Amino Acid Sequence↗
PubMed1991

Mechanism of hemolysis of red blood cell mediated by ethanol.

The effects of ethanol on hemolysis of human red blood cells (RBCs) were studied at 21 +/- 1 degrees C in the saline buffer (138 mM NaCl, 6.1 mM Na2HPO4, 1.4 mM NaH2PO4, 5 mM glucose and pH 7.4). The hemolysis process for ethanol-treated RBCs was preceded by the leakage of the small cation K+ from the cells indicating the colloid-osmotic nature of lysis. Since the extent of membrane lesion increased with an increasing ethanol concentration, osmotic protection experiments by using solutes varying in size were carried out to estimate the diameter of the pore. Quantitative analysis of the data by considering the effect of molecular seiving of the protectants with different sizes indicated that ethanol induced formation of membrane pores with a diameter of approximately 13 A. There was no detectable release of membrane fragments as assayed by the acetylcholinesterase activity, but the membrane structures were significantly perturbed, presumably at the membrane cytoskeletal protein, as evidenced by the altered rheological properties of RBC in the presence of ethanol. It is suggested that the creation of membrane pores might involve in the deranged cytoskeletal network of ethanol-treated RBC.

Adult↗
PubMed1991

Effect of aging on phosphate metabolites of rat brain as revealed by the in vivo and in vitro 31P NMR measurements.

Changes of phosphate metabolism in brains of neonate, weaning and adult rats were compared using both in vivo and in vitro nuclear magnetic resonance spectra. Ratios of phosphocreatine/nucleoside triphosphate (PCr/NTP) were the same in neonatal brain in both in vivo and in vitro studies, but not in weaning and adult brains. This discrepancy may have resulted from extended cerebral hypoxia due to slowed freezing of the brain by the increased skull thickness and brain mass in the weaning and adult rats. Variations in in vitro extraction condition for this age-related study may lead to systematic errors in the adult rats. Nevertheless, the phosphomonoester/nucleoside triphosphate (PME/NTP) ratios in extracts of brain from neonatal rats were higher than those obtained in vivo. In addition, the glycerophosphorylethanolamine plus glycerophosphorylcholine/nucleoside triphosphate (GPE+GPC/NTP) ratios, which were not measurable in vivo, showed age-dependent increase in extracts of rat brain. Some of the phosphomonoester and phosphodiester molecules in rat brain may be undetectable in in vivo NMR analysis because of their interaction with cellular components. The total in vitro GPE and GPC concentration in brain from neonatal rat was estimated to be 0.34 mmole/g wet tissue.

Aging↗
PubMed1991

Phosphatidylcholine transfer protein from porcine liver.

A phosphatidylcholine transfer protein (PC-TP) of porcine liver was purified to exhibit transfer activity similar to that of bovine liver but with different structural properties. By using hydrophobic Phenyl-agarose column as the last purification step, a 1400-fold purification with 20% yield was attained. Comparative studies on the effects of pH, salt, and temperature on the phosphatidylcholine transfer activity revealed that PC-TP from porcine and bovine livers were similar as far as its activity is concerned. However, the amino acid compositions, the molecular weight, and the elution profiles during protein purification for the two proteins are markedly different. It is suggested that the amino acid composition of PC-TP could be significantly altered without changing its activity and specificity.

Amino Acids↗
PubMed1990

Biophysical correlates of lysophosphatidylcholine- and ethanol-mediated shape transformation and hemolysis of human erythrocytes. Membrane viscoelasticity and NMR measurement.

The effects of monopalmitoylphosphatidylcholine (MPPC or lysophosphatidylcholine) and a series of short-chain primary alcohols (ethanol, 1-butanol and 1-hexanol) on cell shape, hemolysis, viscoelastic properties and membrane lipid packing of human red blood cells (RBCs) were studied. For MPPC, the effective membrane concentration to induce the formation of stage 3 echinocytes (8 x 10(6) molecules per cell) was one order of magnitude lower than that needed to induce 50% hemolysis (7 x 10(7) molecules per cell). In contrast, short-chain alcohols induced both shape changes and hemolysis within close concentration range (2.5 x 10(8) to 3.5 x 10(8) molecules per cell). Viscoelastic properties of the RBCs were studied by micropipette aspiration and correlated with shape change. Ethanol-treated RBCs showed a decrease in membrane elastic modulus and an increase in membrane viscosity in the recovery phase at the early stage of shape change. MPPC-treated cells showed the same type of viscoelastic changes, but these were not observed until the formation of stage 2 echinocytes. High-resolution solid-state 13C nuclear magnetic resonance technique was applied to study membrane lipid packing in the ghost membrane by following the chemical shift of hydrocarbon chains. Both MPPC and ethanol caused the 13C-NMR chemical shift to move upfield, indicating that membrane lipids were expanded due to the intercalation of these exogenous molecules. Using data obtained from model compounds, we convert values of chemical shift into a lipid packing parameter, i.e., number of gauche bonds for fatty acyl hydrocarbon chains. Approximately 10(8) interacting molecules per cell are required to induce a detectable change of lipid packing by both MPPC and ethanol. The results indicate that homolysis occurs at a smaller surface area for MPPC- than ethanol-treated RBCs. Our findings suggest that progressive changes in the molecular packing in the membrane lead eventually to hemolysis, but the mode responsible for shape transformation varies with these amphipaths.

Adult↗
PubMed1990

Comparisons of lipid dynamics and packing in fully interdigitated monoarachidoylphosphatidylcholine and non-interdigitated dipalmitoylphosphatidylcholine bilayers: cross polarization/magic angle spinning 13C-NMR studies.

13C-NMR spectra have been obtained at 50.3 MHz for monoarachidoylphosphatidylcholine (MAPC) and dipalmitoylphosphatidylcholine (DPPC) dispersions from 25 degrees C to 55 degrees C and for DPPC polycrystals at 25 degrees C using the cross polarization/magic angle spinning technique. Differential scanning calorimetric studies on DPPC and MAPC dispersions show comparable lipid phase transitions with transition temperatures at 41 degrees C and 45 degrees C, respectively, and thus enable the comparison of thermal, structural and dynamic differences between these two systems at corresponding temperatures. Conformational-dependent 13C chemical shift studies on DPPC dispersions demonstrate not only the coexistence of the tilted gel (L beta') and liquid-crystalline (L alpha) phases in the rippled gel (P beta') phase, but also the presence of an intermediate third microscopic phase as evidenced by three resolvable peaks for omega - 1 methylene carbon signals at the temperature interval between Tp and Tm. By comparing chemical shifts of MAPC in the hydrocarbon chain region with those of DPPC at similar reduced temperatures, it can be concluded that the packings are perturbed markedly in the middle segment of the fatty acyl chain during the lamellar to micellar transition. However, terminal methylene and methyl groups of interdigitated MAPC lamellae were found to be more ordered than those of non-interdigitated DPPC bilayers in the gel state. Interestingly, the terminal methyl groups of MAPC in the micelles remain to be relatively ordered; in fact, they are more ordered than the corresponding acyl chain end of DPPC in the liquid-crystalline state. Analysis of data obtained from rotating frame proton spin-lattice relaxation measurements shows a highly mobile phosphocholine headgroup, a rigid carbonyl group and an ordered hydrocarbon chain for lamellar MAPC in the interdigitated state. Furthermore, results suggest that free rotations of the glycerol C2-C3 bond within MAPC molecules may occur in the interdigitated bilayer, whereas intramolecular exchange between two conformations of the glycerol backbone in DPPC become possible at temperatures close to the pretransition temperature. Without isotope enrichment, we conclude that high-resolution solid-state 13C-NMR is indeed a useful technique which can be employed to study the packing and dynamics of phospholipids.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Effective bilayer expansion and erythrocyte shape change induced by monopalmitoyl phosphatidylcholine. Quantitative light microscopy and nuclear magnetic resonance spectroscopy measurements.

When human erythrocytes are treated with exogenous monopalmitoyl phosphatidylcholine (MPPC), the normal biconcave disk shape red blood cells (RBC) become spiculate echinocytes. The present study examines the quantitative aspect of the relationship between effective bilayer expansion and erythrocyte shape change by a newly developed method. This method is based on the combination of direct surface area measurement of micropipette and relative bilayer expansion measurement of 13C crosspolarization/magic angle spinning nuclear magnetic resonance (NMR). Assuming that 13C NMR chemical shift of fatty acyl chain can be used as an indicator of lateral packing of membrane bilayers, it is possible for us to estimate the surface area expansion of red cell membrane induced by MPPC from that induced by ethanol. Partitions of lipid molecules into cell membrane were determined by studies of shape change potency as a function of MPPC and red cell concentration. It is found that 8(+/- 0.5) x 10(6) molecules of MPPC per cell will effectively induce stage three echinocytes and yield 3.2(+/- 0.2)% expansion of outer monolayer surface area. Surface area of normal cells determined by direct measurements from fixed geometry of red cells aspirated by micropipette was 118.7 +/- 8.5 microns2. The effective cross-sectional area of MPPC molecules in the cell membrane therefore was determined to be 48(+/- 4) A2, which is in agreement with those determined by x-ray from model membranes and crystals of lysophospholipids. We concluded that surface area expansion of RBC can be explained by a simple consideration of cross-sectional area of added molecules and that erythrocyte shape changes correspond quantitatively to the incorporated lipid molecules.

Adult↗
PubMed1989

Proton nuclear magnetic resonance studies of plasma to determine metabolic status of patients with adult respiratory distress syndrome.

Adult respiratory distress syndrome (ARDS) is a non-cardiogenic pulmonary edema of various etiologies. Here we report the first application of proton nuclear magnetic resonance (NMR) for the detection of abnormal metabolites in plasma from patients with ARDS. By comparing plasma obtained from the systemic artery with that obtained from the pulmonary artery, we could study the metabolic status of the lung in patients with ARDS. Although their concentrations may vary, the peaks for acetate, acetoacetate, beta-hydroxybutyrate, phenylalanine, and other unidentified compounds in water-suppressed NMR of these patients' plasma were higher than in the normal controls. The proton NMR resonance at a chemical shift of about 7.4 ppm (relative to sodium tetradeutero-3-trimethyl-silylpropionate), presumably caused by phenylalanine and its related metabolites produced by a disordered amino acid metabolism, is detected in greater than 65% of the samples from ARDS patients. We discuss the detection of abnormal metabolites in terms of possible deranged metabolism of carbohydrates, lipids, or amino acids in this syndrome.

3-Hydroxybutyric Acid↗
PubMed1985

19F NMR investigation of molecular motion and packing in sonicated phospholipid vesicles.

Dimyristoylphosphatidylcholine (DMPC) labeled with a C19F2 group in the 4-, 8-, or 12-position of the 2-acyl chain has been investigated in sonicated unilamellar vesicles (SUV) by fluorine-19 nuclear magnetic resonance (NMR) at 282.4 MHz from 26 to 42 degrees C. The 19F NMR spectra exhibit two overlapping resonances with different line widths. Spin-lattice relaxation time measurements have been performed in both the laboratory frame (T1) and the rotating frame (T1 rho) in order to investigate the packing and dynamics of phospholipids in lipid bilayers. Quantitative line-shape and relaxation analyses are possible by using the experimental chemical shift anisotropy (delta nu CSA) and the internuclear F-F vector order parameter (SFF) values obtained from the 19F powder spectra of multilamellar liposomes. The following conclusions can be made: The 19F chemical shift difference between the inside and outside leaflets of SUV can be used to monitor the lateral packing of the phospholipid in the two SUV monolayers. The hydrocarbon chains in the outer layer are found to be more tightly packed than those of the inner one, and the differences between them become smaller near the chain terminals. The effective correlation time [(1-4) x 10(-7) s] obtained from either the motional narrowing of the line widths or off-resonance T1 rho measurements is shorter than that estimated from the Stokes-Einstein diffusion model (10(-6) s), on the basis of a hydrodynamic radius of 110 A for SUV.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimyristoylphosphatidylcholine↗
PubMed1985

Pressure effect on the rate of crystalline phase formation of L-alpha-dipalmitoylphosphatidylcholines in multilamellar dispersions.

Fully hydrated dipalmitoylphosphatidylcholine (DPPC) in multilamellar dispersions undergoes a subtransition between the crystalline Lc phase and the gel L beta phase. This so-called subtransition occurs only if the DPPC-H2O system has been incubated at temperatures near 0 degrees C for an extended period. We have examined the effect of pressure, up to 336 atm, on the rate of crystalline Lc phase formation of multilamellar DPPC dispersions at 0 degrees C. The hydrostatic pressure is generated by a centrifugal field; the formation of the lamellar Lc phase in the multicomponent DPPC dispersions is monitored calorimetrically at ambient pressure. Results indicate that the rate of formation of the hydrated crystalline Lc phase decreases with increasing pressure. Based on transition state theory, the retardation of the formation of the hydrated crystalline Lc phase by pressure is due to an increase in the volume of the lipid-water system when the activated state is formed. We interpret that the positive value of activation volume is attributed primarily to the dehydration of the lipid polar head group. Although the acyl chain ordering and the head group dehydration are both associated with the L beta----Lc phase transition, the observation of the pressure effects on the rate of crystalline Lc phase formation is used to show that the head group dehydration plays a predominant role in controlling the kinetics of the L beta----Lc phase transition.

Calorimetry, Differential Scanning↗
PubMed1967

Influence of cellular factors on immune unresponsiveness induced by Klebsiella pneumoniae capsular antigen.

The mechanisms by which immune unresponsiveness (immune paralysis) develops are still uncertain. The present work was based on the assumption that this condition may be due to failure of certain activities of the macrophages. Data from passive transfer of such cells are interpreted as supporting this hypothesis. Purified capsular polysaccharide from type 2 Klebsiella pneumoniae induced immunity when given to Swiss albino mice in 5-mug amounts and immune paralysis when given in 1,000-mug amounts. The unresponsive state lapsed to that of acquired immunity 3 months after induction. Passive transfer of cells from groups of K. pneumoniae immune, "paralyzed," and control mice showed that peritoneal cells from "paralyzed" donors induced significant protection against challenge in both control and "paralyzed" recipients. In contrast, spleen cells from control, "paralyzed," and immune animals failed to effect such transfer. The finding that unresponsiveness could be terminated by peritoneal cells and not spleen cells indicates that macrophages played a primary role in immune paralysis, possibly owing to their loss of capacity to transfer factors or information for induction of antibody synthesis.

Animals↗
PubMedDate not supplied

Activity of ALRT 1550, a new retinoid, with interferon-gamma on ovarian cancer cell lines.

Retinoids have been shown to be effective regulators of cell proliferation and differentiation in many human cancers. The major biologic activity of the retinoids is mediated by two families of nuclear receptors: retinoic acid receptors (RARs) and retinoid X receptors (RXRs). ALRT 1550 is one of the most potent RAR selective retinoids discovered to date, with 10-100 times more activity than ATRA in competitive binding and cotransfection assays and 300 times more inhibiting activity against proliferation of cervical carcinoma cell. To evaluate the role of ALRT 1550 in ovarian cancer, the growth inhibitory activity of ALRT 1550 was determined in the ATRA-resistant ovarian cancer cell line SKOV-3 and ovarian cancer cell line 2774 after exposure to concentrations of 0.1, 1, 2.5, 5, and 10 microM for 7 days. SKOV-3 showed 51%, 53%, and 68% cell growth inhibition after treatment with ALRT 1550 at concentrations of 2.5, 5, and 10 microM, respectively, and the 2774 cell line showed 46% inhibition after treatment at 10 microM. Because interferon (IFN)-gamma was found to synergistically amplify the growth inhibition of retinoids in cultured breast cancer cells, we investigated the combination of ALRT 1550 with IFN-gamma in two ovarian cancer cell lines. ALRT 1550 (5 microM) in combination with IFN-gamma at a concentration of 500 U/ml inhibited cell growth of SKOV-3 by as much as 81% (CI = 1.88). This is a 28% greater effect than with ALRT alone. Cell line 2774 showed a 69% cell growth inhibitory effect with ALRT 1550 (5 microM) in combination with IFN-gamma at a concentration of 1000 U/ml (CI = 1.03). ALRT 1550 and IFN-gamma may act synergistically in the SKOV-3 ovarian cancer cell line and additively in the 2774 cell line. In conclusion, ALRT 1550 may be a promising drug with a high biologic modulating activity against ovarian cancer. In combination with IFN-gamma, additive and perhaps synergistic effects may be seen in some ovarian cancer cell lines. Combining these two biologic modifiers for the treatment of ovarian cancer may lower the effective dose of the retinoids, thus decreasing their side effects.

Antineoplastic Agents↗
PubMedDate not supplied

TRAIL-R2 is not correlated with p53 status and is rarely mutated in non-small cell lung cancer.

BACKGROUND: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors play an important role in regulating apoptosis. Recently, it was shown that the expression of TRAIL-R2, also known as KILLER, Trick or DR5, can be induced by either DNA damage or overexpression of a wild-type p53 transgene, suggesting a role for p53 in the death-signaling pathway. Furthermore, mutations in the death domain of TRAIL-R2 were reported in 10.6% of non-small cell lung cancer (NSCLC) patients in a Korean population, suggesting a role for TRAIL-R2 in lung tumorigenesis. MATERIALS AND METHODS: To determine the association between expression of TRAIL-R2 and p53 mutation status in lung cancers, we compared the two events in 20 small-cell lung cancer (SCLC) cell lines, 20 NSCLC cell lines, and 30 primary NSCLC tumors. We also sequenced the death domain of TRAIL-R2 in a total of 100 primary NSCLC. RESULTS: Lack of TRAIL-R2 expression was found in eight of 20 (40%) SCLC cell lines and in eleven of 20 (55%) NSCLC cell lines. Interestingly, in primary NSCLC, TRAIL-R2 was overexpressed in seven (23%) of the 30 tumors tested, and all primary tumors expressed TRAIL-R2. No association was found between the expression status of TRAIL-R2 and p53 mutation status in primary NSCLC tumors, SCLC cell lines or NSCLC cell lines. Further analysis of the death domain of TRAIL-R2 failed to identify any mutation in 100 primary NSCLC tumors. CONCLUSIONS: Our data indicate that the expression profile of TRAIL-R2 is significantly different in lung cancer cell lines and primary tumors, that the expression of TRAIL-R2 is independent from p53 mutation status and that mutations in the death domain of TRAIL-R2 play a minimal role in NSCLCs in white Americans.

Carcinoma, Non-Small-Cell Lung↗