Search PubMed⌕ Search

Biomedical subjects

S Wang

Publications and source records attributed to S Wang.

At least 217 records · Page 12Linked to original sources
PubMed2001

Transgene expression in the brain stem effected by intramuscular injection of polyethylenimine/DNA complexes.

Gene delivery into the CNS without tissue destruction is challenging. As neurons are capable of taking up exogenous particulates from the muscles that they innervate, we investigated the feasibility of achieving gene transfer in CNS neurons by peripheral intramuscular injection of plasmid DNA complexed with the cationic polymer polyethylenimine (PEI) in the rat hypoglossal system. Using the luciferase reporter gene driven by a Rous sarcoma virus promoter, transgene expression of up to 4 x 10(6) RLU per brain stem at 20 microg of plasmid DNA was achieved after tongue injection. Using lacZ as a reporter gene, transgene expression in the brain stem was detected in hypoglossal motor neurons, a group of neurons that innervate tongue muscles. The plasmid DNA was detected by PCR analysis in the brain-stem samples, demonstrating that the PEI/DNA complexes had migrated by retrograde axonal transport to neuronal cell bodies in the brain stem after being internalized by nerve terminals in the tongue muscle. Using a therapeutic bcl-2 gene driven by a cytomegalovirus promoter and Western blotting, transgene expression was detectable in the brain stem as early as 18 h after tongue injection and lasted for at least 2 weeks. Two lipid transfection agents, GenePORTER and TransFast, mediated a weak gene expression in the hypoglossal system, but not two polymers, poly-l-lysine and chitosan. The nonviral neuronal gene delivery method established in this study bypasses the blood-brain barrier and suggests a possible therapeutic strategy for noninvasive CNS gene transfer.

Animals↗
PubMed2001

Gene transfer of p53 to arthritic joints stimulates synovial apoptosis and inhibits inflammation.

Rheumatoid arthritis (RA) is an autoimmune disease that primarily affects joints. During the pathogenesis of rheumatoid arthritis, the synovial lining becomes dramatically thickened and hyperplastic. This highly aggressive tissue invades and destroys articular cartilage and bone. Several lines of evidence suggest that the proliferation of the synovial tissue may be due to disruption in the control of the cell cycle or apoptotic pathways. In particular, mutations in the tumor suppressor protein p53 have been found in synovial tissue from RA joints. We have examined the effects of overexpression of p53 by adenoviral infection in synovial cells in culture and in synovial tissue in vivo in a rabbit model of arthritis. Here we demonstrate that p53 overexpression resulted in significant apoptosis in human and rabbit synovial cells in culture. Furthermore, intraarticular injection of Ad-p53 resulted in extensive and rapid induction of synovial apoptosis in the rabbit knee without affecting cartilage metabolism. Interestingly, a significant reduction in the leukocytic infiltrate was observed within 24 h postinfection of Ad.p53. These results suggest that intraarticular gene transfer of p53 is able to induce synovial apoptosis as well as reduce inflammation and thus may be useful clinically for the treatment of RA.

Adenoviridae↗
PubMed2001

Gene transfer and metabolic modulators as new therapies for pulmonary hypertension. Increasing expression and activity of potassium channels in rat and human models.

UNLABELLED: Chronic Hypoxic Pulmonary Hypertension (CH-PHT) is characterized by pulmonary artery (PA) vasoconstriction and cell proliferation/hypertrophy. PA smooth muscle cell (PASMC) contractility and proliferation are controlled by cytosolic Ca++ levels, which are largely determined by membrane potential (E(M)). E(M) is depolarized in CH-PHT due to decreased expression and functional inhibition of several redox-regulated, 4-aminopyridine (4-AP) sensitive, voltage-gated K+ channels (Kv1.5 and Kv2.1). Humans with Pulmonary Arterial Hypertension (PAH) also have decreased PASMC expression of Kv1.5 and Kv2.1. We speculate this "K+-channelopathy" contributes to PASMC depolarization and Ca++ overload thus promoting vasoconstriction and PASMC proliferation. We hypothesized that restoration of Kv channel expression in PHT and might eventually be beneficial. METHODS: Two strategies were used to increase Kv channel expression in PASMCs: oral administration of a metabolic modulator drug (Dichloroacetate, DCA) and direct Kv gene transfer using an adenovirus (Ad5-Kv2.1). DCA a pyruvate dehydrogenase kinase inhibitor, promotes a more oxidized redox state mimicking normoxia and previously has been noted to increase K+ current in myocytes. Rats were given DCA in the drinking water after the development of CH-PHT and hemodynamics were measured approximately 5 days later. We also tested the ability of Ad5-Kv2.1 to increase Kv2.1 channel expression and function in human PAs ex vivo. RESULTS: The DCA-treated rats had decreased PVR, RVH and PA remodeling compared to the control CH-PHT rats (n=5/group, p<0.05). DCA restored Kv2.1 expression and PASMC Kv current density to near normoxic levels. Adenoviral gene transfer increased expression of Kv2.1 channels and enhanced 4-AP constriction in human PAs. CONCLUSION: Increasing Kv channel function in PAs is feasible and might be beneficial.

Animals↗
PubMed2001

Specific targeting of folate-dendrimer MRI contrast agents to the high affinity folate receptor expressed in ovarian tumor xenografts.

The need to develop target-specific MRI contrast agents to aid in disease characterization remains highly essential. In this study, we present a generation four polyamidoamine (PAMAM) folate-dendrimer that specifically targets the high affinity folate receptor (hFR) overexpressed on more than 80% of ovarian tumors. In vitro, mouse erythroleukemia cells expressing the hFR bind the radiolabeled folate-dendrimer chelate resulting in over 2700% increase in binding compared with untreated cells. The binding was inhibited by free folic acid to levels observed on folate-receptor-negative cells. In vivo, ovarian tumor xenografts resulted in a 33% contrast enhancement, following the folate-dendrimer chelate administration, that was significantly different compared with results obtained with a non-specific, extracellular fluid space agent, Gd-HP-DO3A. In addition, this contrast enhancement was absent in saline-treated animals, folate-receptor-negative tumors, and was inhibited by free folic acid. Results suggest that a macromolecular, dendrimeric MRI agent with high molecular relaxivities (1646 mM(-1) s(-1)) can be used in specifically targeting the hFR on tumor cells and ovarian tumors.

Animals↗
PubMed2001

Effects of extracellular ATP on survival of sensory neurons in the dorsal root ganglia of rats.

ATP was added to the cultured sensory neurons obtained from the dorsal root ganglia of the neonatal rats and PBS was added to serve as control. MTT assays were conducted to evaluate the survival and activity of the cultured neurons. And the silicone regenerative chamber was used after the sciatic nerve incision of the mature SD rat. 1 mmol/L ATP was injected into the left chamber and 0.09% natrium chloride was injected into the right chamber as controls. The changes of nitric oxide synthase (NOS) activity in the corresponding dorsal root ganglia were measured histochemically and image analysis was also performed 4 days after the sciatic nerve injury. The results showed that extracellular ATP could enhance the survival of the neurons and the number of NOS positive neurons were significantly different between the ATP and control groups (P < 0.05). It was suggested that extracellular ATP had neurotrophic effect on neurons survival and could inhibit the NOS activity of the sensory neurons after the peripheral nerve incision, hence exerting the protective effect on the neurons, which was valuable for nerve regeneration after nerve injury.

Adenosine Triphosphate↗
PubMed2001

Nephrin is expressed in the pancreatic beta cells.

AIMS/HYPOTHESIS: The NPHS1 gene product, nephrin, is a crucial component of the glomerular filtration barrier preventing proteinuria and previously assumed to be kidney-specific. The aim of this study was to describe the expression of nephrin mRNA and protein in human pancreas as well as identify the nephrin-expressing cell types. METHODS: RNA dot blot, reverse transcriptase-polymerase chain reaction, sequencing, immunoblotting and dual immunofluorescence were used for the characterisation of nephrin in the pancreas. RESULTS: Except for the kidney, the pancreas was found to be the only tissue expressing nephrin as screened with a human tissue RNA dot blot. The expression was verified with reverse transcriptase-polymerase chain reaction and by sequencing nephrin from a human pancreatic complementary DNA library. Nephrin antibody in immunoblot detected a 165,000 M(r) protein in the pancreas. Dual immunofluorescence showed that nephrin was specifically localised in the beta cells of the islets of Langerhans. There was no overlap with glucagon, somatostatin, or the ductal cell marker cytokeratin 19. CONCLUSION/INTERPRETATION: These data show that nephrin is a novel molecule of pancreatic beta cells.

Cadaver↗
PubMed2001

Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 ORF50 gene product contains a potent C-terminal activation domain which activates gene expression via a specific target sequence.

The ART (Activator of Replication and Transcription) protein of Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus-8 (HHV-8), is encoded by the ORF50 gene. It is expressed as an immediate-early gene and plays a crucial role in the transition between latency and productive infection. HHV-8 ART is a transcriptional transactivator which can up-regulate viral gene expression. Transient expression assays showed that ART strongly activated ORF57 and K8 promoter-directed gene expression in both CV-1 and BJAB cells. The ART target site was mapped to a 40-bp region compassing nt 81904 to 81943 on the ORF57 promoter. When linked upstream to a heterologous SV40 promoter, this region by itself was able to confer ART responsiveness. This 40-bp segment contains a 16-bp consensus sequence which is also found in the K8 promoter region located between nt 74769 to 74784. Deletion of the fragment including this 16-bp consensus abrogated the ART responsiveness of the K8 promoter. The role of this 16-bp consensus in ART transactivation was further supported by site-directed mutagenesis. Mutations of the conserved nucleotides within the 16-bp consensus in the ORF57 promoter dramatically impaired its responsiveness to ART. Fusion protein analysis with chimeric proteins containing the DNA binding domain of yeast transactivator Gal4 (residues 1 to 147) and different ART segments defined an acidic C-terminal region (amino acids [aa] 527 to 634) as a potent activator. Deletions of this activation domain in the ART protein resulted in a decrease or loss of its ability to activate ORF57 and K8 promoters containing the ART responsive element in transfected cells. How the ART activation domain activates ORF57 and K8 gene expression through the 16-bp consensus sequence remains to be determined.

Basic-Leucine Zipper Transcription Factors↗
PubMed2001

Characterization of Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 ORF57 promoter.

Kaposi's sarcoma-associated herpesvirus (KSHV) is a recently discovered human gamma herpesvirus (HHV-8) that plays an important role in Kaposi's sarcoma development. Here, we further characterize the regulation of the early HHV-8 gene, open reading frame 57 (ORF57). ORF57 is a spliced gene consisting of two exons with a 108-bp intron near the 5' end. The ORF57 mRNA can potentially be initiated at two different start sites, and its expression can be significantly stimulated by ORF50, an HHV-8 immediate early gene. The target site for ORF50 transactivation was mapped to a 40-bp fragment compassing nt 81904 to 81943 in the ORF57 promoter. Our study on the regulation of ORF57 expression by ORF50 provides the basis for further studies on the regulation of HHV-8 lytic gene expression.

Animals↗
PubMed2001

Study of laser vas deferens occlusion.

The objective of this study was to determine threshold levels for high-power laser output Nd:YAG laser photocoagulation and to determine the possible reversibility of laser vas occlusion. The study included vas deferens of 220 rabbits and 20 samples of men in vitro, applying the Nd:YAG laser instrument, doing vasopuncture by a catheter needle, guiding the fiber into the vas, and performing the irradiation occlusion experiment to determine effective threshold value of photocoagulation. The effect and safety of occlusion were followed-up over a year, and reopening a experiment was done in 60 occluded nodes of rabbits. The postoperative sperm disappearance rate was 100%, and reopening rate was 72.7% without obvious complications. High-power lasers may be used as photocoagulation, and its merits are reliable, effective, and rapid recovery. The vas threshold lesion value of rabbits and men in vitro are 50 W/0.5 s, 45 W/1 s, respectively, and irradiation depth reached the middle-ring muscularis.

Animals↗
PubMed2001

Imaging of fungal, viral, and parasitic musculoskeletal and spinal diseases.

There are many nonbacterial infections that have musculoskeletal manifestations and radiologic findings. These infections produce a limited range of tissue responses, depending on the organism, the tissue compartment affected, and the immune competence of the host. Diagnosis is dependent on obtaining an appropriate travel or geographic history, the clinical and laboratory features, and on occasion the specific radiologic findings.

Humans↗
PubMed2001

Analgesic efficacy of ketorolac and morphine in neonatal rats.

Ketorolac is a potent nonsteroidal antiinflammatory drug (NSAID). In adult humans and animals, its analgesic efficacy can be comparable to opiates. However, it has not been studied in neonatal animals. We conducted a blinded, controlled study comparing the effects of ketorolac and morphine in neonatal rats using the formalin model. Animals were given intraperitoneal (i.p.) injections of ketorolac or morphine at 3 or 21 days of age. Ketorolac had an analgesic and antiinflammatory effect in 21-day-old pups, but not in the 3-day-olds. Morphine had a significant analgesic, but no antiinflammatory effect at both ages. These results indicate that ketorolac is an effective analgesic agent in preweaning, but not neonatal rats. Opiates may be more appropriate analgesics in neonates.

Age Factors↗
PubMed2001

Fabrication of poly(phosphoester) nerve guides by immersion precipitation and the control of porosity.

Immersion precipitation was employed as a method for the fabrication of polymeric conduits from P(BHET-EOP/TC), a poly(phosphoester) with an ethylene terephthalate backbone, to be applied as guidance channels for nerve regeneration. Coatings of various porosities could be obtained by immersing mandrels coated with a solution of the polymer in chloroform into non-solvent immersion baths, followed by freeze or vacuum-drying. The porosity of the coatings decreased with an increase in polymer molecular weight, drying time before precipitation and concentration of polymer solution. The effects of these parameters can be rationalized by employing ternary phase diagrams, where porosity is directly related to the degree of phase separation available to the system before gelation occurs. To afford improved porosity control, a new system was developed which employed the contrasting phase-separation behavior of P(BHET-EOP/TC)/chloroform solution in methanol and water. As water is essentially a non-solvent for the polymer, the demixing boundary of the P(BHET-EOP/TC)-CHCl3-H2O system is located close to the polymer-solvent edge of the phase diagram, while that of the P(BHET-EOP/TC)-CHCl3-MeOH system is located further away. A mixture of methanol and water allows the demixing boundary to be shifted to intermediate coordinates. By immersing P(BHET-EOP/TC) coatings in immersion baths containing different ratios of water and methanol, then gradually titrating the bath with methanol to a concentration of 70% (v/v) methanol, surface porosities ranging from 2 to 58% could be achieved.

Biocompatible Materials↗
PubMed2001

A new nerve guide conduit material composed of a biodegradable poly(phosphoester).

There is a resurgence of interest in the development of degradable and biocompatible polymers for fabrication of nerve guide conduits (NGCs) in recent years. Poly(phosphoester) (PPE) polymers are among the attractive candidates in this context, in view of their high biocompatibility, adjustable biodegradability, flexibility in coupling fragile biomolecules under physiological conditions and a wide variety of physicochemical properties. The feasibility of using a biodegradable PPE, P(BHET-EOP/TC), as a novel NGC material was investigated. Two types of conduits were fabricated by using two batches of P(BHET-EOP/TC) with different weight-average molecular weights (Mw) and polydispersity indexes (PI). The polymers as well as conduits were non-toxic to all six types of cells tested, including primary neurones and neuronally differentiated PC12 cells. After in situ implantation in the sciatic nerve of the rat, two types of conduits triggered a similar tissue response, inducing the formation of a thin tissue capsule composed of approximately eight layers of fibroblasts surrounding the conduits at 3 months. Biological performances of the conduits were examined in the rat sciatic nerve model with a 10 mm gap. Although tube fragmentation, even tube breakage, was observed within less than 5 days post-implantation, successful regeneration through the gap occurred in both types of conduits, with four out of 10 in the Type I conduits (Mw 14,900 and PI 2.57) and 11 out of 12 in the Type II conduits (Mw 18,900 and PI 1.72). The degradation of conduits was further evidenced by increased roughness on the tube surface in vivo under scanning electron microscope and a mass decrease in a time-dependent manner in vitro. The Mw of the polymers dropped 33 and 24% in the Type I and II conduits, respectively, in vitro within 3 months. Among their advantages over other biodegradable NGCs, the PPE conduits showed negligible swelling and no crystallisation after implantation. Thus, these PPE conduits can be effective aids for nerve regeneration with potential to be further developed into more sophisticated NGCs that have better control of the conduit micro-environment for improved nerve regeneration.

Animals↗
PubMed2001

Progressive visual sensitivity loss in the Royal College of Surgeons rat: perimetric study in the superior colliculus.

The Royal College of Surgeons rat has a retinal pigment epithelial cell defect which causes a progressive loss of rods occurring primarily over the first few months of life. We have studied the consequences of this degenerative process on visual sensitivity across the visual field. Sensitivities were determined in the superior colliculus for unit responses recorded from 22 days up to one year of age from sites encompassing the whole visual field representation. Following visual sensitivity assessment, retinae were examined anatomically at the light and electron microscopic level. At 22 days of age, sensitivities in dystrophic rats were comparable to those of non-dystrophics at any age (40+/-1 and 41+/-1dB, respectively), despite the fact that signs of degenerative events were clear at the electron microscopic level, including presence of pyknotic photoreceptor nuclei, disorganised outer segments and accumulation of debris. However, loss in sensitivity was first detected only at 28-36 days of age (27+/-4dB). From then on, sensitivities progressively decreased to reach a plateau by 180-240 days (4+/-2dB). Starting around 90 days and onward, there was a positive gradient of sensitivities from temporal to nasal field. Drops in visual sensitivity were parallelled by several changes in visual response properties, including prolonged latency, inconsistent responsiveness, appearance of bursting spontaneous activity and activation of units by stimuli presented outside their classical receptive fields. The measure of visual sensitivities by recording visual responses at specific sites in the superior colliculus provides a reliable point-to-point assessment of retinal function comparable to visual perimetry testing in humans. This experimental approach provides the background for answering questions arising during the development of potential experimental therapies for retinal degeneration using animal models like the Royal College of Surgeons rat.

Animals↗
PubMed2001

Risk for respiratory distress syndrome in preterm infants born to mothers complicated by placenta previa.

This study examined the risk factors for respiratory distress syndrome (RDS) in preterm infants from pregnancies complicated by placenta previa. Forty preterm infants born to mothers with placenta previa between January 1989 and December 1995 in a medical center were enrolled. Each of these patients was matched in gestational age and gender with an infant born immediately after to a mother without placenta previa. Obstetric and neonatal outcome variables were collected. The mean+/-S.D. gestational age for both groups was 33.0+/-3.1 weeks. There was no difference in mean birthweight between the placenta previa and control groups (2129+/-598 vs. 2136+/-493 g). All the patients in the former and 11 (28%) in the latter were born by cesarean section. About a half of the mothers in both groups received antenatal steroids. Infants from placenta previa pregnancies had a higher incidence (21/40 vs. 10/40, P<0.01) and more severe RDS than controls. Stratified by the status of treatment with antenatal steroid, we found that gestational age was a significant risk factor for RDS in both treated and untreated groups (P<0.01), but placenta previa was an independent risk factor (odds ratio 32; CI 1-4182) by multiple exact logistic regression in antenatal steroid-treated group. We conclude that preterm infants born to mothers with placenta previa had a higher risk for RDS than controls. It played an independent role, in addition to gestational age, only in infants treated with antenatal steroid. We speculate that placenta previa was not directly contributing to RDS, but through other associated risk factors for RDS.

Adrenal Cortex Hormones↗
PubMed2001

Molecular recognition in a reconstituted tumor cell membrane.

The design of an immunoliposome system for molecular recognition using reconstituted, hydrogel-supported bilayer lipid membranes (sb-BLMs) is described. By monitoring the electrical properties, two kinds of recognition are feasible: (i) the human bladder tumor cells, Ej and its antibody BDI-1, the lifetime of the reconstituted membrane is 42 min; and (ii) the human rectum tumor cells, LOVO, the life of the reconstructed membrane is more than 40 min, the same as conventional BLM. Further, the anticancer drug, Adriamycin (Anticancer Res., 20 (2000) 1391), was shown to be effective in such reconstituted systems, the life of which is less than 5 min. In these experiments, the active ingredients of the Ej and LOVO cells were determined on reconstituted sb-BLMs. The key point is that the component part being recognized on the BLM must be kept in its native state.

Antigen-Antibody Reactions↗