Yong Guo - Academia.edu (original) (raw)

Papers by Yong Guo

Research paper thumbnail of A unified stability analysis of meshless particle methods

International Journal for Numerical Methods in Engineering, 2000

A uniÿed stability analysis of meshless methods with Eulerian and Lagrangian kernels is presented... more A uniÿed stability analysis of meshless methods with Eulerian and Lagrangian kernels is presented. Three types of instabilities were identiÿed in one dimension: an instability due to rank deÿciency, a tensile instability and a material instability which is also found in continua. The stability of particle methods with Eulerian and Lagrangian kernels is markedly di erent: Lagrangian kernels do not exhibit the tensile instability. In both kernels, the instability due to rank deÿciency can be suppressed by stress points. In two dimensions the stabilizing e ect of stress points is dependent on their locations. It was found that the best approach to stable particle discretizations is to use Lagrangian kernels with stress points. The stability of the least-squares stabilization was also studied.

Research paper thumbnail of A multiple-quadrature eight-node hexahedral finite element for large deformation elastoplastic analysis

Computer Methods in Applied Mechanics and Engineering, 1998

A multiple-quadrature underintegrated hexahedral finite element, which is free of volumetric and ... more A multiple-quadrature underintegrated hexahedral finite element, which is free of volumetric and shear locking, and has no spurious singular modes, is described and implemented for nonlinear analysis. Finite element formulations are derived in the corotational coordinate system. ...

Research paper thumbnail of Differential Inhibition of Human Immunodeficiency Virus Type 1 Fusion, gp120 Binding, and CC-Chemokine Activity by Monoclonal Antibodies to CCR5

The CC-chemokine receptor CCR5 mediates fusion and entry of the most commonly transmitted human i... more The CC-chemokine receptor CCR5 mediates fusion and entry of the most commonly transmitted human immunodeficiency virus type 1 (HIV-1) strains. We have isolated six new anti-CCR5 murine monoclonal antibodies (MAbs), designated PA8, PA9, PA10, PA11, PA12, and PA14. A panel of CCR5 alanine point mutants was used to map the epitopes of these MAbs and the previously described MAb 2D7 to specific amino acid residues in the N terminus and/or second extracellular loop regions of CCR5. This structural information was correlated with the MAbs' abilities to inhibit (i) HIV-1 entry, (ii) HIV-1 envelope glycoprotein-mediated membrane fusion, (iii) gp120 binding to CCR5, and (iv) CC-chemokine activity. Surprisingly, there was no correlation between the ability of a MAb to inhibit HIV-1 fusion-entry and its ability to inhibit either the binding of a gp120-soluble CD4 complex to CCR5 or CC-chemokine activity. MAbs PA9 to PA12, whose epitopes include residues in the CCR5 N terminus, strongly inhibited gp120 binding but only moderately inhibited HIV-1 fusion and entry and had no effect on RANTES-induced calcium mobilization. MAbs PA14 and 2D7, the most potent inhibitors of HIV-1 entry and fusion, were less effective at inhibiting gp120 binding and were variably potent at inhibiting RANTES-induced signaling. With respect to inhibiting HIV-1 entry and fusion, PA12 but not PA14 was potently synergistic when used in combination with 2D7, RANTES, and CD4-immunoglobulin G2, which inhibits HIV-1 attachment. The data support a model wherein HIV-1 entry occurs in three stages: receptor (CD4) binding, coreceptor (CCR5) binding, and coreceptor-mediated membrane fusion. The antibodies described will be useful for further dissecting these events.

Research paper thumbnail of A recombinant human imunodeficiency virus type 1 envelope glycoprotein complex stabilized by an intermolecular disulfide bond between the gp120 and gp41 subunits is an antigenic mimic of the trimeric virion-associated structure

Journal of Virology, 2000

The few antibodies that can potently neutralize human immunodeficiency virus type 1 (HIV-1) recog... more The few antibodies that can potently neutralize human immunodeficiency virus type 1 (HIV-1) recognize the limited number of envelope glycoprotein epitopes exposed on infectious virions. These native envelope glycoprotein complexes comprise three gp120 subunits noncovalently and weakly associated with three gp41 moieties. The individual subunits induce neutralizing antibodies inefficiently but raise many nonneutralizing antibodies. Consequently, recombinant envelope glycoproteins do not elicit strong antiviral antibody responses, particularly against primary HIV-1 isolates. To try to develop recombinant proteins that are better antigenic mimics of the native envelope glycoprotein complex, we have introduced a disulfide bond between the C-terminal region of gp120 and the immunodominant segment of the gp41 ectodomain. The resulting gp140 protein is processed efficiently, producing a properly folded envelope glycoprotein complex. The association of gp120 with gp41 is now stabilized by the supplementary intermolecular disulfide bond, which forms with approximately 50% efficiency. The gp140 protein has antigenic properties which resemble those of the virionassociated complex. This type of gp140 protein may be worth evaluating for immunogenicity as a component of a multivalent HIV-1 vaccine.

Research paper thumbnail of A chemokine receptor CCR2 allele delays HIV1 disease progression and is associated with a CCR5 promoter mutation

Research paper thumbnail of Genetic characterization of rebounding HIV1 after cessation of highly active antiretroviral therapy

Journal of Clinical Investigation, 2000

Research paper thumbnail of Quantifying Residual HIV1 Replication in Patients Receiving Combination Antiretroviral Therapy

New England Journal of Medicine, 1999

In patients infected with human immunodeficiency virus type 1 (HIV-1), combination antiretroviral... more In patients infected with human immunodeficiency virus type 1 (HIV-1), combination antiretroviral therapy can result in sustained suppression of plasma levels of the virus. However, replication-competent virus can still be recovered from latently infected resting memory CD4 lymphocytes; this finding raises serious doubts about whether antiviral treatment can eradicate HIV-1. We looked for evidence of residual HIV-1 replication in eight patients who began treatment soon after infection and in whom plasma levels of HIV-1 RNA were undetectable after two to three years of antiretroviral therapy. We examined whether there had been changes over time in HIV-1 proviral sequences in peripheral-blood mononuclear cells, which would indicate residual viral replication. We also performed in situ hybridization studies on tissues from one patient to identify cells actively expressing HIV-1 RNA. We estimated the rate of decrease of latent, replication-competent HIV-1 in resting CD4 lymphocytes on the basis of the decrease in the numbers of proviral sequences identified during primary infection and direct sequential measurements of the size of the latent reservoir. Six of the eight patients had no significant variations in proviral sequences during treatment. However, in two patients there was sequence evolution but no evidence of drug-resistant viral genotypes. In one patient, extensive in situ studies provided additional evidence of persistent viral replication in lymphoid tissues. Using two independent approaches, we estimated that the half-life of the latent, replication-competent virus in resting CD4 lymphocytes was approximately six months. These findings suggest that combination antiretroviral regimens suppress HIV-1 replication in some but not all patients. Given the half-life of latently infected CD4 lymphocytes of about six months, it may require many years of effective antiretroviral treatment to eliminate this reservoir of HIV-1.

Research paper thumbnail of Differentiation of clinically benign and malignant breast lesions using diffusion-weighted imaging

Journal of Magnetic Resonance Imaging, 2002

PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign... more PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.To evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.Materials and MethodsFifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.Fifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.ResultsThe ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).The ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).ConclusionThe ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.The ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.

Research paper thumbnail of Differentiation of clinically benign and malignant breast lesions using diffusion-weighted imaging

Journal of Magnetic Resonance Imaging, 2002

PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign... more PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.To evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.Materials and MethodsFifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.Fifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.ResultsThe ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).The ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).ConclusionThe ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.The ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.

Research paper thumbnail of A unified stability analysis of meshless particle methods

International Journal for Numerical Methods in Engineering, 2000

A uniÿed stability analysis of meshless methods with Eulerian and Lagrangian kernels is presented... more A uniÿed stability analysis of meshless methods with Eulerian and Lagrangian kernels is presented. Three types of instabilities were identiÿed in one dimension: an instability due to rank deÿciency, a tensile instability and a material instability which is also found in continua. The stability of particle methods with Eulerian and Lagrangian kernels is markedly di erent: Lagrangian kernels do not exhibit the tensile instability. In both kernels, the instability due to rank deÿciency can be suppressed by stress points. In two dimensions the stabilizing e ect of stress points is dependent on their locations. It was found that the best approach to stable particle discretizations is to use Lagrangian kernels with stress points. The stability of the least-squares stabilization was also studied.

Research paper thumbnail of A multiple-quadrature eight-node hexahedral finite element for large deformation elastoplastic analysis

Computer Methods in Applied Mechanics and Engineering, 1998

A multiple-quadrature underintegrated hexahedral finite element, which is free of volumetric and ... more A multiple-quadrature underintegrated hexahedral finite element, which is free of volumetric and shear locking, and has no spurious singular modes, is described and implemented for nonlinear analysis. Finite element formulations are derived in the corotational coordinate system. ...

Research paper thumbnail of Differential Inhibition of Human Immunodeficiency Virus Type 1 Fusion, gp120 Binding, and CC-Chemokine Activity by Monoclonal Antibodies to CCR5

The CC-chemokine receptor CCR5 mediates fusion and entry of the most commonly transmitted human i... more The CC-chemokine receptor CCR5 mediates fusion and entry of the most commonly transmitted human immunodeficiency virus type 1 (HIV-1) strains. We have isolated six new anti-CCR5 murine monoclonal antibodies (MAbs), designated PA8, PA9, PA10, PA11, PA12, and PA14. A panel of CCR5 alanine point mutants was used to map the epitopes of these MAbs and the previously described MAb 2D7 to specific amino acid residues in the N terminus and/or second extracellular loop regions of CCR5. This structural information was correlated with the MAbs' abilities to inhibit (i) HIV-1 entry, (ii) HIV-1 envelope glycoprotein-mediated membrane fusion, (iii) gp120 binding to CCR5, and (iv) CC-chemokine activity. Surprisingly, there was no correlation between the ability of a MAb to inhibit HIV-1 fusion-entry and its ability to inhibit either the binding of a gp120-soluble CD4 complex to CCR5 or CC-chemokine activity. MAbs PA9 to PA12, whose epitopes include residues in the CCR5 N terminus, strongly inhibited gp120 binding but only moderately inhibited HIV-1 fusion and entry and had no effect on RANTES-induced calcium mobilization. MAbs PA14 and 2D7, the most potent inhibitors of HIV-1 entry and fusion, were less effective at inhibiting gp120 binding and were variably potent at inhibiting RANTES-induced signaling. With respect to inhibiting HIV-1 entry and fusion, PA12 but not PA14 was potently synergistic when used in combination with 2D7, RANTES, and CD4-immunoglobulin G2, which inhibits HIV-1 attachment. The data support a model wherein HIV-1 entry occurs in three stages: receptor (CD4) binding, coreceptor (CCR5) binding, and coreceptor-mediated membrane fusion. The antibodies described will be useful for further dissecting these events.

Research paper thumbnail of A recombinant human imunodeficiency virus type 1 envelope glycoprotein complex stabilized by an intermolecular disulfide bond between the gp120 and gp41 subunits is an antigenic mimic of the trimeric virion-associated structure

Journal of Virology, 2000

The few antibodies that can potently neutralize human immunodeficiency virus type 1 (HIV-1) recog... more The few antibodies that can potently neutralize human immunodeficiency virus type 1 (HIV-1) recognize the limited number of envelope glycoprotein epitopes exposed on infectious virions. These native envelope glycoprotein complexes comprise three gp120 subunits noncovalently and weakly associated with three gp41 moieties. The individual subunits induce neutralizing antibodies inefficiently but raise many nonneutralizing antibodies. Consequently, recombinant envelope glycoproteins do not elicit strong antiviral antibody responses, particularly against primary HIV-1 isolates. To try to develop recombinant proteins that are better antigenic mimics of the native envelope glycoprotein complex, we have introduced a disulfide bond between the C-terminal region of gp120 and the immunodominant segment of the gp41 ectodomain. The resulting gp140 protein is processed efficiently, producing a properly folded envelope glycoprotein complex. The association of gp120 with gp41 is now stabilized by the supplementary intermolecular disulfide bond, which forms with approximately 50% efficiency. The gp140 protein has antigenic properties which resemble those of the virionassociated complex. This type of gp140 protein may be worth evaluating for immunogenicity as a component of a multivalent HIV-1 vaccine.

Research paper thumbnail of A chemokine receptor CCR2 allele delays HIV1 disease progression and is associated with a CCR5 promoter mutation

Research paper thumbnail of Genetic characterization of rebounding HIV1 after cessation of highly active antiretroviral therapy

Journal of Clinical Investigation, 2000

Research paper thumbnail of Quantifying Residual HIV1 Replication in Patients Receiving Combination Antiretroviral Therapy

New England Journal of Medicine, 1999

In patients infected with human immunodeficiency virus type 1 (HIV-1), combination antiretroviral... more In patients infected with human immunodeficiency virus type 1 (HIV-1), combination antiretroviral therapy can result in sustained suppression of plasma levels of the virus. However, replication-competent virus can still be recovered from latently infected resting memory CD4 lymphocytes; this finding raises serious doubts about whether antiviral treatment can eradicate HIV-1. We looked for evidence of residual HIV-1 replication in eight patients who began treatment soon after infection and in whom plasma levels of HIV-1 RNA were undetectable after two to three years of antiretroviral therapy. We examined whether there had been changes over time in HIV-1 proviral sequences in peripheral-blood mononuclear cells, which would indicate residual viral replication. We also performed in situ hybridization studies on tissues from one patient to identify cells actively expressing HIV-1 RNA. We estimated the rate of decrease of latent, replication-competent HIV-1 in resting CD4 lymphocytes on the basis of the decrease in the numbers of proviral sequences identified during primary infection and direct sequential measurements of the size of the latent reservoir. Six of the eight patients had no significant variations in proviral sequences during treatment. However, in two patients there was sequence evolution but no evidence of drug-resistant viral genotypes. In one patient, extensive in situ studies provided additional evidence of persistent viral replication in lymphoid tissues. Using two independent approaches, we estimated that the half-life of the latent, replication-competent virus in resting CD4 lymphocytes was approximately six months. These findings suggest that combination antiretroviral regimens suppress HIV-1 replication in some but not all patients. Given the half-life of latently infected CD4 lymphocytes of about six months, it may require many years of effective antiretroviral treatment to eliminate this reservoir of HIV-1.

Research paper thumbnail of Differentiation of clinically benign and malignant breast lesions using diffusion-weighted imaging

Journal of Magnetic Resonance Imaging, 2002

PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign... more PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.To evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.Materials and MethodsFifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.Fifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.ResultsThe ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).The ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).ConclusionThe ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.The ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.

Research paper thumbnail of Differentiation of clinically benign and malignant breast lesions using diffusion-weighted imaging

Journal of Magnetic Resonance Imaging, 2002

PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign... more PurposeTo evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.To evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions.Materials and MethodsFifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.Fifty-two female subjects (mean age = 58 years, age range = 25–75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated.ResultsThe ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).The ADCs varied substantially between benign breast lesions ((1.57 ± 0.23) × 10−3 mm2/second) and malignant breast lesions ((0.97 ± 0.20) × 10−3 mm2/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = −0.542).ConclusionThe ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.The ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors. J. Magn. Reson. Imaging 2002;16:172–178. © 2002 Wiley-Liss, Inc.