Biomedical subjects

S L Woo

Publications and source records attributed to S L Woo.

At least 127 records · Page 7Linked to original sources

PubMed1996

A single integral finite strain viscoelastic model of ligaments and tendons.

A general continuum model for the nonlinear viscoelastic behavior of soft biological tissues was formulated. This single integral finite strain (SIFS) model describes finite deformation of a nonlinearly viscoelastic material within the context of a three-dimensional model. The specific form describing uniaxial extension was obtained, and the idea of conversion from one material to another (at a microscopic level) was then introduced to model the nonlinear behavior of ligaments and tendons. Conversion allowed different constitutive equations to be used for describing a single ligament or tendon at different strain levels. The model was applied to data from uniaxial extension of younger and older human patellar tendons and canine medial collateral ligaments. Model parameters were determined from curve-fitting stress-strain and stress-relaxation data and used to predict the time-dependent stress generated by cyclic extensions.

Adult↗

PubMed1996

Phenotypic correction of dwarfism by constitutive expression of growth hormone.

GH is normally secreted in a pulsatile fashion. When GH is deficient, dwarfism is the result in both rodents and humans. An adenoviral vector containing the rat GH complementary DNA was used to induce constitutive GH expression in hepatocytes of GH-deficient lit/lit mice. Elevated serum GH increased circulating insulin-like growth factor I concentrations, corrected the growth deficiency, and normalized body composition. The results indicate that correction of the dwarf phenotype can be achieved by constitutive expression of GH at an ectopic site by gene transfer.

Adenoviruses, Human↗

PubMed1996

Molecular basis of phenylketonuria and a correlation between genotype and phenotype in a heterogeneous southeastern US population.

OBJECTIVE: To determine the molecular basis of phenylketonuria (PKU) and related hyperphenylalaninemia (HPA) and to establish correlations between phenylalanine hydroxylase (PAH) genotypes and biochemical and clinical phenotypes in an ethnically diverse US population, PAH genotypes were determined in 35 patients with PKU or HPA and 1 carrier from the Medical Genetics Clinic of the Emory University School of Medicine. METHODOLOGY: Patients were identified through Georgia's population-based newborn screening program. PAH genotypes in these individuals were determined from dried blood spots or whole-blood samples using a combination of polymerase chain reaction-mediated amplification, denaturing gradient gel electrophoresis, and direct-sequence analysis. The phenotypic severity of patients with PKU and HPA was based on pretreatment serum phenylalanine (PHE) levels during the neonatal period and on dietary tolerance of PHE later in life. RESULTS: Sixty-eight (96%) of 71 mutant alleles were identified. Major mutations in this population included R408W (11 of 71), I65T (11 of 71), Y414C (6 of 71), L348V (4 of 71), and IVS10 (4 of 71). Five new nucleotide substitutions, E76A (1 of 71), R241L (1 of 71), Q304R (2 of 71), C334S (1 of 71), and R400R (2 of 71) were also detected. Thirty-two of the thirty-five nonrelated patients examined in this study were completely genotyped. Strong correlations were observed between the level of PAH activity predicted from the genotype, when known from previous in vitro expression studies of the mutant proteins, and pretreatment serum PHE levels (r = .841) or clinical severity (Kendall rank-order correlation coefficient, .936). CONCLUSIONS: These results demonstrate strong correlations between PAH genotype and biochemical and clinical phenotypes in this heterogeneous American sample population, extending our previous findings from relatively homogeneous European populations. These correlations further demonstrate the clinical utility of genotype analysis in the treatment of patients with PKU and HPA.

Alleles↗

PubMed1996

Lack of persistence of E1- recombinant adenoviral vectors containing a temperature-sensitive E2A mutation in immunocompetent mice and hemophilia B dogs.

Two recombinant adenoviruses expressing either human alpha 1-antitrypsin (hAAT) or canine factor IX (cFIX) were modified so that they also contained a temperature-sensitive mutation (ts125) in the DNA binding protein encoded within the viral E2A region. The effects of the inclusion of the ts125 mutation on transgene expression in vivo were evaluated in Balb/c mice and hemophilia B dogs by comparison with adenoviral vectors containing the same transgene but lacking the ts125 mutation. No significant differences in the duration of transgene expression were observed in either animal model. Insufficiency of the ts125 mutation in the prolongation of transgene expression in these two animal models suggests that further modification of the vector backbone may be required to achieve long-term gene expression in a wide variety of applications. Additionally, humoral immune response to transgene products has been demonstrated in immunocompetent animal models, which will also need to be surmounted for long-term efficacy in disease treatment by gene therapy.

Adenoviridae↗

PubMed1996

Biomechanical properties of peripheral nerves.

The biomechanical properties of peripheral nerves still are not completely understood or quantified. This is partly because of the nonhomogeneous nature of nerves and the variation in the proportions of the components of different nerves. The recognition and quantification of the in-situ stress and the viscoelastic behavior of nerves have been important stepping stones in understanding their mechanical behavior. The effects of stretch and compression on the vascular supply and conduction properties of normal animal nerves have been well studied. Similar studies in injured nerves will provide invaluable information for understanding the mechanics of nerve function and the prevention of stretch- and compression-related trauma.

Animals↗

PubMed1996

Evaluation of promoter strength for hepatic gene expression in vivo following adenovirus-mediated gene transfer.

Transgene expression in studies of both gene function and gene therapy may be assisted considerably through the use of transcriptional regulatory elements which permit high-level, and/or tissue-specific gene expression. We have therefore evaluated the transcriptional activities of a series of viral and cellular enhancer/promoter elements, both in vitro and in vivo. The five enhancer/promoter elements showing either high-level or hepatocyte-specific expression following transient transfection into hepatoma cells were incorporated into recombinant adenoviruses expressing human alpha 1-antitrypsin (hAAT) for in vivo studies in the liver of immunodeficient and immunocompetent mice. The human elongation factor 1 alpha gene promoter produced 2 mg/ml serum level of hAAT, which is physiologic in humans and will be therapeutic for patients with AAT deficiency. This and all other enhancer/promoters except that of the CMV-IE gene yielded persistent hAAT expression in SCID mice. These findings demonstrate that adenovirus vectors provide an effective system for studies designed to evaluate enhancer/promoter activities in vivo. Several of the enhancer/promoters examined in this study will have significant utility in adenovirus-mediated gene therapy for alpha 1-antitrypsin deficiency and other genetic disorders.

Adenoviruses, Human↗

PubMed1996

Gene therapy for hepatocellular carcinoma: long-term remission of primary and metastatic tumors in mice by interleukin-2 gene therapy in vivo.

To explore gene therapy as a new treatment modality for hepatocellular carcinoma, a pre-clinical animal model was established by intrahepatic implantation of a mouse hepatocellular carcinoma cell line (MH134) in syngeneic recipients. The resulting hepatic tumors were treated with a recombinant adenoviral vector expressing the murine interleukin-2 (IL-2) gene, and long-term remission was achieved in 50% of the animals. The remaining animals died of malignant ascites, which also occurs in some human patients. Those animals were treated with a second dose of the recombinant adenoviral vector by direct inoculation into the peritoneal cavity, and long-term remission of the disseminated disease was achieved in 55% of the animals. Thus, a combined cure rate of greater than 75% for primary- and disseminated hepatocellular carcinoma was achieved by successive adenovirus-mediated IL-2 gene treatments. Histopathological and immunocytochemical analyses showed massive infiltration of the tumor by macrophages and T lymphocytes in IL-2 vector treated animals. The surviving animals developed systemic antitumoral cellular immunity that protected them against challenges of parental hepatoma cells implanted at distant sites. The results suggest that IL-2 gene therapy may be a strategy applicable for the treatment of both primary and metastatic hepatocellular carcinomas in man.

Adenoviridae↗

PubMed1996

Forces and moments in six-DOF at the human knee joint: mathematical description for control.

A mathematical description of six-degree of freedom (6-DOF) forces and moments with respect to a commonly utilized knee joint coordinate system was performed using a [6 x 6] Jacobian matrix developed in this study. The presented Jacobian allows the proper transformation of the forces and moments measured at a sensor coordinate system (attached to the tibia in this case) into the joint coordinate system and is dependent on the kinematics of the joint itself. Experimental application of the developed mathematics to A-P drawer tests of the intact knee confirmed that it is possible to determine the forces and moments applied to a human knee within the joint coordinate system during joint loading. More importantly, the inverse Jacobian was also determined for implementation in the force-moment control of the joint during testing using a robotic testing system. This approach is demonstrated for the joint coordinate system for the human knee in the current study, although it may be more generally applied to allow determination and control of forces and moments within any description of motions, and for any additional joints in the human body.

Aged↗

PubMed1996

A novel DNA-peptide complex for efficient gene transfer and expression in mammalian cells.

To develop a nonviral gene delivery system for treatment of diseases, our strategy is to construct DNA complexes with short synthetic peptides that mimic the functions of viral proteins. We have designed and synthesized two peptides which emulate viral functions - a DNA condensing agent, YKAK(8)WK, and an amphipathic, pH-dependent endosomal releasing agent, GLFEALLELLESLWELLLEA. The active gene delivery complex was constructed step-wise through a spontaneous self-assembly process involving oppositely charged, electrostatic interactions. To assemble DNA-peptide complexes with different overall net charges, only the negative charges of DNA phosphate, the positive charges of the 10 epsilon-amino groups of YKAK(8)WK and the negative charges of the 5 gamma-carboxyl groups of GLFEALLELLESLWELLLEA were considered. In the first step, negatively charged DNA was rapidly-mixed with an excess of YKAK(8)WK to form positively charged DNA-YKAK(8)WK complexes, which gave little gene transfer. In the second step and to form the active complex,the cationic DNA complex was rapidly mixed with spontaneously incorporated through electrostatic interactions. Transfection using these complexes of CMV-luc, YKAK(8)WK and GLFEALLELLESLWELLLEA gave high-levels of gene expression in a variety of cell lines. These simple DNA complexes, which contain only three molecularly defined components, have general utility for gene delivery and can replace viral vectors and cationic lipids for some applications in gene therapy.

Amino Acid Sequence↗

PubMed1995

Near-IR dyes in three-color volumetric capillary cytometry: cell analysis with 633- and 785-nm laser excitation.

Several fluorescent dyes that absorb in the near-infrared are described. The photostability and aggregation properties of the dyes were examined. Two of the dyes, BHMP and BHDMAP, emit at 805 nm and were useful dyes for protein labeling. A dual-laser, three-color scanning instrument was constructed. CD3+CD4+ and CD3+CD8+ populations were enumerated in undiluted, whole blood based on the fluorescence of Cy5, Cy5.5 and BHMP.

Antigens, CD↗

PubMed1995

Adenovirus-mediated gene therapy for experimental spinal cord tumors: tumoricidal efficacy and functional outcome.

We evaluated the efficacy of adenoviral-mediated gene therapy of experimental spinal cord tumors and the functional outcome after this treatment. Spinal cord tumors were generated in the thoracic region of the spinal cord in Fischer 344 rats by stereotaxic intramedullary injection of 1 x 10(4) 9L gliosarcoma cells. Seven days after tumor cell injection, a replication-defective adenoviral vector carrying the herpes simplex virus thymidine kinase gene (ADV-tk) or a control adenoviral vector carrying the beta-galactosidase gene (ADV-beta gal) was injected into the tumors. Beginning 12 h later the animals were treated with the antiviral drug ganciclovir (GCV; 50 mg/kg) or saline twice a day for 6 days. The neurological performance of the animals was assessed during and following treatment. Eighteen days after tumor cell injection, all of the control animals had paraplegia and large tumors. In contrast, no tumors were detected in animals treated with ADV-tk and GCV. In long-term studies, two of the 5 animals treated with ADV-tk and GCV remained tumor-free and remained neurologically intact at 6 months whereas all animals in the control groups became paraplegic within 18 days.

Animals↗

PubMed1995

Gene therapy for diabetes mellitus in rats by hepatic expression of insulin.

Type 1 diabetes mellitus is caused by severe insulin deficiency secondary to the autoimmune destruction of pancreatic beta cells. Patients need to be controlled by periodic insulin injections to prevent the development of ketoacidosis, which can be fatal. Sustained, low-level expression of the rat insulin 1 gene from the liver of severely diabetic rats was achieved by in vivo administration of a recombinant retroviral vector. Ketoacidosis was prevented and the treated animals exhibited normoglycemia during a 24-hr fast, with no evidence of hypoglycemia. Histopathological examination of the liver in the treated animals showed no apparent abnormalities. Thus, the liver is an excellent target organ for ectopic expression of the insulin gene as a potential treatment modality for type 1 diabetes mellitus by gene therapy.

Animals↗

PubMed1995

Combination gene therapy for liver metastasis of colon carcinoma in vivo.

The efficacy of combination therapy with a "suicide gene" and a cytokine gene to treat metastatic colon carcinoma in the liver was investigated. Tumor in the liver was generated by intrahepatic injection of a colon carcinoma cell line (MCA-26) in syngeneic BALB/c mice. Recombinant adenoviral vectors containing various control and therapeutic genes were injected directly into the solid tumors, followed by treatment with ganciclovir. While the tumors continued to grow in all animals treated with a control vector or a mouse interleukin 2 vector, those treated with a herpes simplex virus thymidine kinase vector, with or without the coadministration of the mouse interleukin 2 vector, exhibited dramatic necrosis and regression. However, only animals treated with both vectors developed an effective systemic antitumoral immunity against challenges of tumorigenic doses of parental tumor cells inoculated at distant sites. The antitumoral immunity was associated with the presence of MCA-26 tumor-specific cytolytic CD8+ T lymphocytes. The results suggest that combination suicide and cytokine gene therapy in vivo can be a powerful approach for treatment of metastatic colon carcinoma in the liver.

Adenoviridae↗

PubMed1995

Adenovirus-mediated gene therapy for human head and neck squamous cell cancer in a nude mouse model.

Adenovirus-mediated transfer of the herpes simplex virus thymidine kinase gene followed by ganciclovir administration was used to treat human head and neck cancer in nude mice. Tumors were generated by transcutaneous needle injection of 6 x 10(6) human squamous carcinoma cells into the floor of the mouth. After 14 days, 10(10) particles of a replication-defective recombinant adenovirus containing the herpes simplex virus thymidine kinase gene (ADV/RSV-tk) were injected directly into the tumors. The mice subsequently received ganciclovir injections for six consecutive days and were sacrificed at 21 days post tumor cell implantation. Clinical response to the treatment was assessed by computer-imaged morphometric analysis of cross sectional area of nonnecrotic tumor and mitotic activity, which were used for the calculation of a tumor index. The median tumor index value of the treatment group was 280- to 2400-fold smaller than controls which did not receive the therapeutic gene (P < 0.001-0.016), and three-quarters of the treatment group had tumor index values that were indicative of near total tumor regression. Survival studies show that 50% of the ADV/RSV-tk-treated mice are free of tumor at 160 days post adenovirus injection, while all controls died or required sacrifice within 43 days. These results demonstrate that clinically effective in vivo treatment of human squamous cell cancer can be achieved using adenovirus-mediated gene therapy.

Adenoviridae↗

PubMed1995

Interspecies variation of compressive biomechanical properties of the meniscus.

Various animal models have been used to investigate the normal and reparative properties of the knee meniscus. Yet, only limited data on meniscal biomechanical properties of various animals are available. It was therefore the objective of this study to compare measurements of meniscal biomechanical properties between six species: human, bovine, monkey, canine, sheep, and porcine. Uniaxial confined compression tests were conducted on 1-mm-thick, 4-mm-diameter meniscal discs, and the viscoelastic creep deformation was obtained. Two biomechanical parameters, the aggregate modulus (HA) and permeability (K), were found by implementing the linear biphasic theory and a newly developed nonlinear regression scheme. A one-way analysis of variance was conducted along with Student-Newman-Keuls comparison tests to assess the differences in these parameters among the species. Sheep menisci exhibited HA and K values most similar to human menisci. The water content of each specimen was also measured and correlated significantly with K. The interspecies variations found in material properties of the knee meniscus indicate the need for caution in extrapolating data on the biomechanical behavior of the human meniscus from animal models.

Adult↗

PubMed1995

Effect of growth factors on the proliferation of fibroblasts from the medial collateral and anterior cruciate ligaments.

Growth factors have been shown to stimulate fibroblast division and thus may influence ligament healing. We analyzed the effects of individual growth factors on the proliferation of fibroblasts from the medial collateral and anterior cruciate ligaments of the rabbit in vitro in order to identify growth factors that might enhance proliferation of fibroblasts and to compare the responses of the fibroblasts from the two ligaments to these growth factors. Through measurement of the uptake of [3H]-thymidine into DNA, fibroblasts from these ligaments that had been treated with epidermal growth factor and basic fibroblast growth factor were found to proliferate nearly eight times more than control fibroblasts. Additionally, the fibroblasts of both ligaments proliferated at similar rates when exposed to platelet-derived growth factor-AA, platelet-derived growth factor-BB, basic fibroblast growth factor, insulin-like growth factor-1, and interleukin-1-alpha. However, epidermal growth factor and transforming growth factor-beta caused the fibroblasts from the medial collateral ligament to proliferate at a rate 1.3-1.4 times greater than that of fibroblasts from the anterior cruciate ligament. The reverse was true with acidic fibroblast growth factor, which stimulated the fibroblasts from the anterior cruciate ligament to proliferate at a rate 1.3-1.6 times greater than that of fibroblasts from the medial collateral ligament. This study demonstrated that growth factors can stimulate cell division in ligaments and may be effective in enhancing ligament healing but that these differences were not great enough to explain fully the clinical differences observed between healing of the medial collateral and anterior cruciate ligaments.

Animals↗

PubMed1995

Immobilization of the knee joint alters the mechanical and ultrastructural properties of the rabbit anterior cruciate ligament.

The effects of immobilization of the knee joint on the mechanical and ultrastructural properties of the anterior cruciate ligament have not been well documented. Our goal was to determine these effects in a rabbit model and to assess the effect of knee flexion angle during immobilization. The knee joint was immobilized in either 170 degrees or 105 degrees of flexion, and new methodologies were utilized to determine the mechanical properties of the anterior cruciate ligament. In specimens from knees that had been immobilized, the cross-sectional area of the ligament was 74% of the control value. The stress-strain curve was altered slightly, and the strain at failure increased 32-40%. The modulus and stress at failure did not decrease significantly. There was no significant difference between the mechanical properties of the knees immobilized at 170 degrees and 105 degrees of flexion. Histological and ultrastructural evaluation demonstrated changes in the shape and intracellular make-up of the fibroblasts from the ligament after immobilization. This cellular response may account for the alterations in the mechanical properties of the anterior cruciate ligament.

Animals↗

PubMed1995

Comparative study of the size and shape of human anterior and posterior cruciate ligaments.

As an important step toward determination of the function of cruciate ligaments, the cross-sectional shapes and areas of the anterior cruciate, posterior cruciate, and meniscofemoral ligaments were evaluated in situ within the same knee with use of a laser micrometer system. Measurements were made in eight human cadaveric knees at five levels along the midsubstance of each ligament, with the knee at 0 degree, 30 degrees, 60 degrees, and 90 degrees of flexion. The posterior cruciate ligament was found to be widest in the medial-lateral direction, whereas the anterior cruciate ligament usually was larger in the anterior-posterior direction. The cross-sectional shapes of the anterior cruciate ligament generally were noted to be more circular along the entire midsubstance than were those of the posterior cruciate ligament. In contrast, the cross-sectional shapes of the posterior cruciate ligament were more circular near the tibia, becoming progressively more elongated toward the femur. The meniscofemoral ligaments were more circular than the cruciate ligaments, with an occasional medial-lateral widening similar to that of the posterior cruciate ligament. The cross-sectional area of both the cruciate ligaments changed along the length of the midsubstance, with the anterior cruciate ligament becoming slightly larger distally and the posterior cruciate ligament enlarging proximally. The angle of flexion of the knee was not found to have a significant effect on the cross-sectional areas of the ligaments but was noted to alter the cross-sectional shapes.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗