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G Lu

Publications and source records attributed to G Lu.

At least 145 records · Page 8Linked to original sources
PubMed1996

Transcription factor veracity: is GBF3 responsible for ABA-regulated expression of Arabidopsis Adh?

Assignment of particular transcription factors to specific roles in promoter elements can be problematic, especially in systems such as the G-box, where multiple factors of overlapping specificity exist. In the Arabidopsis alcohol dehydrogenase (Adh) promoter, the G-box regulates expression in response to cold and dehydration, presumably through the action of abscisic acid (ABA), and is bound by a nuclear protein complex in vivo during expression in cell cultures. In this report, we test the conventional wisdom of biochemical approaches used to identify DNA binding proteins and assess their specific interactions by using the G-box and a nearby half G-box element of the Arabidopsis Adh promoter as a model system. Typical in vitro assays demonstrated specific interaction of G-box factor 3 (GBF3) with both the G-box and the half G-box element. Dimethyl sulfate footprint analysis confirmed that the in vitro binding signature of GBF3 essentially matches the footprint signature detected in vivo at the G-box. Because RNA gel blot data indicated that GBF3 is itself induced by ABA, we might have concluded that GBF3 is indeed the GBF responsible in cell cultures for binding to the Adh G-box and is therefore responsible for ABA-regulated expression of Adh. Potential limitations of this conclusion are exposed by the fact that other GBFs bind the G-box with the same signature as GBF3, and subtle differences between in vivo and in vitro footprint signatures indicate that factors other than or in addition to GBF3 interact with the half G-box element.

Abscisic Acid↗
PubMed1996

Oleic acid-induced mitogenic signaling in vascular smooth muscle cells. A role for protein kinase C.

As an initial step in testing the hypothesis that high oleic acid concentrations contribute to vascular remodeling in obese hypertensive patients by activating protein kinase C (PKC), the effects of oleic acid on primary cultures of rat aortic smooth muscle cells (RASMCs) were studied. Oleic acid, an 18-carbon cis-monounsaturated fatty acid (18:1 [cis]), from 25 to 200 mumol/L significantly increased [3H]thymidine uptake in RASMCs with an EC50 of 41.0 mumol/L and a maximal response of 196 +/- 15% of control (P < .01). Oleic acid from 25 to 200 mumol/L caused a concentration-dependent increase in the number of RASMCs in culture at 6 days, reaching a maximum of 210 +/- 13% of control at 100 mumol/L (P < .001). PKC inhibition with 4 mumol/L bisindolyImaleimide I and PKC depletion (alpha, mu, iota, and zeta) with 24-hour exposure to 200 nmol/L phorbol 12-myristate 13-acetate in RASMCs eliminated the mitogenic effects of oleic acid but did not reduce responses to 10% FBS. Stimulation of intact cells with oleic acid induced a peak increase of cytosolic PKC activity, reaching 328 +/- 8% of control (P < .001), but did not enhance PKC activity in the membrane fraction (105 +/- 4%, P = NS). The oleic acid-induced increase of PKC activity in cell lysates was similar in the presence and absence of Ca2+, phosphatidylserine, and diolein (maximum response, 360 +/- 4% versus 342 +/- 9% of control, P = NS). Unlike phorbol 12-myristate 13-acetate, oleic acid over 24 hours did not downregulate any of the four PKC isoforms detected in RASMCs. Oleic acid treatment activated mitogen-activated protein (MAP) kinase. PKC depletion in RASMCs eliminated the rise in thymidine uptake, activation of PKC, and activation of MAP kinase in response to oleic acid. In contrast to oleic acid, 50 to 200 mumol/L stearic (18:0) and elaidic (18:1 [trans]) acids, which are less effective activators of PKC than oleic acid, did not enhance thymidine uptake. These data suggest that oleic acid induces proliferation of RASMCs by activating PKC, particularly one or more of the Ca(2+)-independent isoforms, and raise the possibility that the higher oleic acid concentrations observed in obese hypertensive patients may contribute to vascular remodeling.

Animals↗
PubMed1996

[Inhibitory action of Chinese compound prescription for reinforcing vital energy and invigorating blood circulation on cancer cell multiplication].

Experiments have proved that the Chinese compound prescription for reinforcing vital energy and invigorating blood circulation markedly helps to improve the morphology of cancer cell nucleolus and membrane surface microvillus, amend the composition of microtubulin and facilitate intercellular gap junctional communication. Cell cycle kinetics shows that the multiplication of cancer cells in human stomach is checked mainly at G2M stage.

Adenocarcinoma, Mucinous↗
PubMed1996

A quadriplegic patient's cholescintigraphic findings: delayed gallbladder visualization and common bile duct dilation.

A Tc-99m DISIDA cholescintigraphic study of a 37-year-old patient with a 20-year history of quadriplegia demonstrated dilation of the common bile duct and delayed gallbladder visualization. A concurrent sonographic study showed an enlarged gallbladder with stones and dilation of the common bile duct. These findings were proved by autopsy. Quadriplegia secondary to a high level of spinal cord injury may result in gallbladder dysfunction.

Adult↗
PubMed1996

[The value of dynamic pulmonary perfusion imaging in the diagnosis of hepatopulmonary syndrome (HPS)].

OBJECTIVE: To evaluate the value of 99m-Tc-MAA dynamic pulmonary perfusion imaging in the diagnosis of HPS. METHODS: 3 cases of liver cirrhosis with marked hypoxemia were studied. RESULTS: The shunt ratios with 100% inspired oxygen were elevated (16%, 27% and 11% respectively). Imaging with gamma camera revealed radioisotope uptake in their lungs, brains and kidneys. Shunt ratios estimated by the quantitative radionuclide method were 43%, 52% and 32% respectively). (control < 7%). The contradictory shunt ratio by using the above method results from dilation of alveolar capilaries. The same examinations were done in 10 cases of healthy controls and other patients. CONCLUSION: The imaging helps diagnosing the HPS as well as estimating the degree of shunting.

Adult↗
PubMed1995

Fructose-1,6-bisphosphatase: arginine-22 is involved in stabilization of the T allosteric state.

A comparison of the X-ray crystallographic structures of the R and T allosteric states [Ke, H. M., Liang, J.-Y., Zhang, Y., & Lipscomb, W. N. (1991) Biochemistry 30, 4412-4420] of the pig kidney fructose-1,6-bisphosphatase (EC 3.1.3.11) reveals major changes in the quaternary structure of the enzyme upon the binding of the allosteric inhibitor AMP. This change in quaternary structure involves the breaking of one set of interactions that stabilize the R state and the formation of another set of interactions that stabilize the T state of the enzyme. In particular, the interactions of Arg-22 with nearby amino acid residues are quite different in the R and T states of the enzyme. Although the crystallographic data suggest that intersubunit interactions such as those involving Arg-22 are important for stabilization of the R and/or T states, the X-ray structures do not provide direct evidence concerning the functional role of specific amino acid residues. Therefore, site-specific mutagenesis has been used to probe the function of Arg-22 in pig kidney fructose-1,6-bisphosphatase. The replacement of Arg-22 by Ala results in a mutant enzyme with enhanced catalytic efficiency compared to the wild-type, as indicated by a kinetic analysis showing a slightly lower Km and increased Vmax compared to the wild-type enzyme. In addition, the substitution enhances both substrate inhibition and the affinity of the inhibitor fructose 2,6-bisphosphate. Moreover, the replacement of Arg-22 by Ala results in a more than 10-fold loss of the ability of AMP to inhibit the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Monophosphate↗
PubMed1995

Structural studies on corn nitrate reductase: refined structure of the cytochrome b reductase fragment at 2.5 A, its ADP complex and an active-site mutant and modeling of the cytochrome b domain.

The refined crystal structures of the recombinant cytochrome b reductase fragment of corn (Zea mays) nitrate reductase, its ADP complex and the active-site mutant Cys242Ser are reported here. The native structure has been refined at 2.5 A resolution to a crystallographic R-factor of 18.7% with root-mean-square (r.m.s) deviations from standard bond lengths and angles of 0.013 A and 2.0 degrees. The diffraction pattern of the crystals is highly anisotropic and correction of this effect lowered the crystallographic R-factor by 5% during the refinement. The structure of the enzyme co-crystallized with ADP has been solved at 2.7 A resolution and refined to an R-factor of 18.6% with r.m.s. deviations from standard bond lengths and angles of 0.014 A and 2.1 degrees. It revealed the binding site of the ADP moiety of the NADH cofactor, which is the electron donor for nitrate reduction. Based on this structure, a model of NADH at the active site of the enzyme was built and the implications for electron transfer from NADH to the flavin cofactor are discussed. The crystal structure of an active-site mutant enzyme, Cys242Ser, has been solved by difference Fourier synthesis and refined to an R-factor of 19.0% to 3.0 A resolution with standard deviations of bond lengths and angles of 0.017 A and 2.5 degrees. This structure analysis suggests that the observed decrease in catalytic activity of this mutant might be due to misalignment of the nicotinamide ring in its binding site. A model of the heme-containing domain of nitrate reductase has been built based on the X-ray structure of bovine cytochrome b5 and has been docked with the cytochrome b reductase fragment of nitrate reductase. The model of the complex contains six salt-bridges at the domain-domain interface and a hydrophobic core. In this model, His48, an invariant residue in the cytochrome b reductase family, forms an interaction with the propionic acid group of the D-ring of the heme cofactor. This group is in contact with the C-8 methyl group of the flavin ring. Residues that might influence the redox potential of the flavin cofactor are proposed and their possible role in electron transfer is discussed.

Adenosine Diphosphate↗
PubMed1995

Dietary n - 3 polyunsaturated fatty acids modify Syrian hamster platelet and macrophage phospholipid fatty acyl composition and eicosanoid synthesis: a controlled study.

The aim of this study was to determine the effects of varying intakes of dietary n - 3 polyunsaturated fatty acids (PUFA) on the fatty acyl composition and arachidonic acid metabolite synthesis of platelets and macrophages in Syrian hamsters consuming diets that were strictly controlled for n - 6 PUFA content. Animals consumed highly controlled diets which were not supplemented with n - 3 PUFA (control) or supplemented with 0.4%, 0.8% or 2% (w/w) n - 3 fatty acids. The content of n - 3 PUFA in cellular phospholipids increased progressively with the intake of n - 3 PUFA, while n - 6 PUFA, including arachidonic acid, decreased despite the constant intake of 18:2(n - 6); this latter effect was more substantial in macrophages than in platelets. The synthesis by stimulated macrophages of prostaglandin E2, 6-keto-prostaglandin F1 alpha, thromboxane B2 and 11- and 15-hydroxyeicosatetraenoic acids decreased with the intake of 0.8% n - 3 PUFA to 30-50% of the control values. Little effect of diets on platelet aggregation and eicosanoid synthesis was observed reflecting the limited effect on platelet arachidonic acid content. The synthesis of 12-hydroxyeicosapentaenoic acid by stimulated platelets increased with n - 3 PUFA consumption in a dose-dependent fashion. Circulating triacylglycerols and HDL-cholesterol were decreased only in animals consuming 2% n - 3 PUFA. The strict control of n - 6 PUFA intake allows the determination of the effects of n - 3 PUFA intake on the measured parameters without confounding effects of other dietary lipids.

Animals↗
PubMed1995

Sequence identity and antigenic cross-reactivity of white face hornet venom allergen, also a hyaluronidase, with other proteins.

White face hornet (Dolichovespula maculata) venom has three known protein allergens which induce IgE response in susceptible people. They are antigen 5, phospholipase A1, and hyaluronidase, also known as Dol m 5, 1, and 2, respectively. We have cloned Dol m 2, a protein of 331 residues. When expressed in bacteria, a mixture of recombinant Dol m 2 and its fragments was obtained. The fragments were apparently generated by proteolysis of a Met-Met bond at residue 122, as they were not observed for a Dol m 2 mutant with a Leu-Met bond. Dol m 2 has 56% sequence identity with the honey bee venom allergen hyaluronidase and 27% identity with PH-20, a human sperm protein with hyaluronidase activity. A common feature of hornet venom allergens is their sequence identity with other proteins in our environment. We showed previously the sequence identity of Dol m 5 with a plant protein and a mammalian testis protein and of Dol m 1 with mammalian lipases. In BALB/c mice, Dol m 2 and bee hyaluronidase showed cross-reactivity at both antibody and T cell levels. These findings are relevant to some patients' multiple sensitivity to hornet and bee stings.

Allergens↗
PubMed1995

Murine T and B cell responses to natural and recombinant hornet venom allergen Dol m 5.02 and its recombinant fragments.

White-face hornet venom allergen, Dol m 5.02, is a protein of 204 amino acid residues. This protein and its overlapping fragments, of 53-114 residues in size, containing the N-terminal, middle, and C-terminal regions of the molecule, can be expressed in high yield in bacteria by using the plasmid vector pQE12. Natural (n) and recombinant (r) Dol m 5.02s and the r-fragments are about equally immunogenic for IgG Ab response in BALB/c mice. n-Dol m 5.02 induces mainly murine IgG Abs specific for its discontinuous B cell epitopes and, to a lesser extent, Abs specific for its continuous epitopes. r-Dol m 5.02 and the r-fragments induce only Abs specific for continuous B cell epitopes that are common with those of the n-protein. Abs specific for the discontinuous epitopes show higher affinity than those specific for the continuous epitopes. r-Dol m 5.02 and the r-fragments are as efficient as n-Dol m 5.02 in inducing murine T cell responses specific for the n-protein. The differences in the immunogenicity of n- and r-proteins or r-peptide fragments for B and T cell responses are related to their conformations, inasmuch as only the n-protein is cross-linked by four disulfide bonds. These findings are relevant to the potential use of r-fragments as immunotherapeutic reagents in humans.

Allergens↗
PubMed1995

A method for processing diffraction data from twinned protein crystals and its application in the structure determination of an FAD/NADH-binding fragment of nitrate reductase.

A general method to deconvolute oscillation data sets from twinned protein crystals to a corresponding single-crystal data set has been developed and applied to diffraction data measured from crystals of a fragment containing the FAD- and NADH-binding domains of nitrate reductase. The procedure allows straightforward processing of diffraction data from twinned crystals. Typically, R(merge) values of reduced data sets from the nitrate reductase crystals after deconvolution are about 0.06 compared to 0.13 and higher before deconvolution. Based on these deconvoluted data sets, the structure of the FAD- and NADH-binding domains of nitrate reductase could be solved successfully. The result indicates that crystal twinning does not necessarily prevent crystallographic structure determination.

Journal Article↗
PubMed1995

Brain-derived neurotrophic factor induces functional expression and phenotypic differentiation of cultured fetal neuropeptide Y-producing neurons.

A series of studies from our laboratory has established an aggregate culture system of fetal rat brain cells that can serve as a model for studying regulatory processes of the developing neuropeptide Y (NPY)-producing neurons. Using aggregate cultures derived from 17-day-old fetal rat cortex, we addressed these questions: 1) Does brain-derived neurotrophic factor (BDNF) stimulate NPY production, and if so, is stimulation a function of the developmental state of the cultured NPY neuron? 2) Does BDNF induce phenotypic differentiation of NPY neurons? BDNF led to an increase in NPY production and the accumulation of NPY-mRNA in a dose dependent manner. BDNF did not alter the stability of NPY-mRNA, judged by the disappearance rate of NPY-mRNA after blockade of RNA synthesis (estimated t1/2 was 6-8 hr). BDNF stimulation of NPY production was dependent on length of exposure to BDNF and on culture-age. A continuous 8-day exposure to BDNF resulted in a significantly higher level of NPY production than a pulse of 2 days (comparing BDNF exposure on days 0-8 vs. 6-8, or days 8-17 vs. 15-17). Moreover, older neurons (age 17 days) produced twice as much NPY as younger (age 8 days) neurons in response to a 2-day pulse of BDNF (50 ng/ml). BDNF was significantly more effective than NT-3 in inducing NPY production, and NGF was ineffective. Immunocytochemical analysis of 8-day NPY neurons revealed that a 2-day pulse of BDNF induced the appearance of an abundance of morphologically well-defined neurons bearing an elaborate network of neurites. This was in contrast to the control-treated NPY neurons, which were morphologically undefined. In summary, the age-dependent effect of BDNF on NPY production is consistent with induction of functional expression, rather than promotion of survival, of cultured NPY neurons. The neurotrophin specificity for stimulation of NPY production, and the lack of effect of BDNF on the stability of NPY-mRNA, implicate the TrkB receptor in mediating transcriptional activation of the NPY gene. Thus, BDNF exerts a dual effect on developing cultured NPY neurons: induction of functional expression, and phenotypic differentiation of immature neurons into mature neurite-bearing neurons.

Animals↗
PubMed1995

Milk composition in women from five different regions of China: the great diversity of milk fatty acids.

Human milk samples were obtained from 146 lactating women living in five distinct geographic regions of the People's Republic of China. The regions were characterized as follows: pastoral, rural, urban 1, urban 2, and marine. Dietary information obtained on a subsample of women providing milk suggested distinct differences in the food availability in the five regions and the habitual diets of the lactating women studied. The milk concentration of docosahexaenoic acid (DHA) varied greatly (g/100 g total fatty acids): 0.44 +/- 0.29 (pastoral), 0.68 +/- 0.29 (rural), 0.88 +/- 0.34 (urban 1), 0.82 +/- 0.35 (urban 2), and 2.78 +/- 1.20 (marine region). Docosahexaenoic acid is critical for brain and retina development in the infant. Milk arachidonic acid (AA) ranged from 0.80 +/- 0.14 (rural) to 1.17 +/- 0.33 and 1.22 +/- 0.32 g/100 g fatty acids from the marine and pastoral regions. Arachidonic acid is associated with infant growth. The AA to DHA ratio (g/g) was highly variable also: 2.77 (pastoral), 1.18 (rural), 1.01 (urban 1), 1.23 (urban 2), and 0.42 (marine). The DHA concentration found in the milk of women from the marine region was twice as high as any reported previously, but was in a range similar to the amounts found in the milk of women fed fish oil. Seafood consumption by the women residing in the marine region is a likely contributor to the DHA concentration in their milk. These data illustrate the heterogeneity of the fatty acid composition of human milk and suggest a great influence of geography and the maternal diet on concentrations of DHA and AA in human milk.

Adult↗
PubMed1995

Oleic acid inhibits endothelial nitric oxide synthase by a protein kinase C-independent mechanism.

Many obese hypertensive individuals have a cluster of cardiovascular risk factors. This cluster includes plasma nonesterified fatty acid concentrations and turnover rates that are higher and more resistant to suppression by insulin than in lean and obese normotensive individuals. The higher fatty acids may contribute to cardiovascular risk in these patients by inhibiting endothelial cell nitric oxide synthase activity. To test this hypothesis, we quantified the effects of oleic (18:1[cis]) and other 18-carbon fatty acids on nitric oxide synthase activity in cultured bovine pulmonary artery endothelial cells by measuring the conversion of [3H]L-arginine to [3H]L-citrulline. Oleic acid (from 10 to 100 mumol/L) caused a concentration-dependent decrease in nitric oxide synthase activity at baseline and during ATP and ionomycin (Ca2+ ionophore) stimulation. At 100 mumol/L, linoleic (18:2[cis]) and oleic acids caused similar reductions of nitric oxide synthase activity, whereas elaidic (18:1[trans]) and stearic (18:0) acids had no effect. Oleic acid also inhibited the endothelium-dependent vasodilator response to acetylcholine in rabbit femoral artery rings preconstricted with phenylephrine (P < .05) but had no effect on the response to nitroprusside. The pattern of 18-carbon fatty acid effects on nitric oxide synthase activity in endothelial cells is consistent with activation of protein kinase C. Although oleic acid increased protein kinase C activity in endothelial cells, neither depletion of protein kinase C by 24-hour pretreatment with phorbol 12-myristate 13-acetate nor its inhibition with staurosporine eliminated the inhibitory effect of oleic acid on nitric oxide synthase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗