Biomedical subjects

D Wang

Publications and source records attributed to D Wang.

At least 307 records · Page 17Linked to original sources

PubMed2000

Preparation and Characterization of Stearate-Capped Titanium Dioxide Nanoparticles.

The preparation of titanium dioxide nanoparticles capped with stearate by sol-gel methods is presented in this paper. The nanoparticles are characterized by Fourier transform infrared spectroscopy and by X-ray photoelectron spectroscopy. Existence of the organic layer can be confirmed by the results of characterizations, which also indicate that the inorganic nuclei and organic surface layer are linked with chemical bonds. The nanoparticles are poorly crystallized based on the X-ray diffraction pattern. The mechanism of formation of the organo-capped nanoparticles is proposed to be competitive reactions between water and stearic acid, which is similar to a polymerization and inhibition processes. A structural model for organo-capped nanoparticles is also proposed. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

A small amphipathic alpha-helical region is required for transcriptional activities and proteasome-dependent turnover of the tyrosine-phosphorylated Stat5.

Cytokines induce the tyrosine phosphorylation and associated activation of signal transducers and activators of transcription (Stat). The mechanisms by which this response is terminated are largely unknown. Among a variety of inhibitors examined, the proteasome inhibitors MG132 and lactacystin affected Stat4, Stat5 and Stat6 turnover by significantly stabilizing the tyrosine-phosphorylated form. However, these proteasome inhibitors did not affect downregulation of the tyrosine-phosphorylated Stat1, Stat2 and Stat3. With Stat5 isoforms, we have observed that tyrosine-phosphorylated carboxyl-truncated forms of Stat5 proteins were considerably more stable than phosphorylated wild-type forms of the protein. Also, the C-terminal region of Stat5 could confer proteasome-dependent downregulation to Stat1. With a series of C-terminal deletion mutants, we have defined a relatively small, potentially amphipathic alpha-helical region that is required for the rapid turnover of the phosphorylated Stat5 proteins. The region is also required for transcriptional activation, suggesting that the functions are linked. The results are consistent with a model in which the transcriptional activation domain of activated Stat5 is required for its transcriptional activity and downregulation through a proteasome-dependent pathway.

Acetylcysteine↗

PubMed2000

The Smad4 activation domain (SAD) is a proline-rich, p300-dependent transcriptional activation domain.

Transforming growth factor-beta (TGF-beta) family members signal through a unique set of intracellular proteins called Smads. Smad4, previously identified as the tumor suppressor DPC4, is functionally distinct among the Smad family, and is required for the assembly and transcriptional activation of diverse, Smad-DNA complexes. We previously identified a 48-amino acid proline-rich regulatory element within the middle linker domain of this molecule, the Smad4 activation domain (SAD), which is essential for mediating these signaling activities. We now characterize the functional activity of the SAD. Mutants lacking the SAD are still able to form complexes with other Smad family members and associated transcription factors, but cannot activate transcription in these complexes. Furthermore, the SAD itself is able to activate transcription in heterologous reporter assays, identifying it as a proline-rich transcriptional activation domain, and indicating that the SAD is both necessary and sufficient to activate Smad-dependent transcriptional responses. We show that transcriptional activation by the SAD is p300-dependent, and demonstrate that this activity is associated with a physical interaction of the SAD with the amino terminus of p300. These data identify a novel function of the middle linker region of Smad4, and define the role of the SAD as an important locus determining the transcriptional activation of the Smad complex.

Amino Acid Sequence↗

PubMed2000

Basal signaling activity of human dopamine D2L receptor demonstrated with an ecdysone-inducible mammalian expression system.

Basal signaling activity of the dopamine D2L (long isoform) receptor was investigated using an ecdysone-inducible mammalian expression system. Whereas basal signaling activity had been demonstrated for the D1, D2S (short isoform), D3, and D5 receptor subtypes, this issue has yet to be clearly resolved for the D2L receptors. An ecdysone-inducible mammalian expression system was used to express the dopamine D2L receptor in human embryonic kidney cells (HEK293). The two ecdysone analogs, muristerone A and ponasterone A, induced D2L receptor expression dose-dependently from 120 (non-induced) to 2000 fmol/mg protein which is similar to physiological D2 receptor density in dopaminergic brain regions. With this approach, we demonstrate significant basal D2L receptor activity. Basal and agonist-stimulated signaling activity, determined with assays of cAMP levels and [35S]GTPgammaS binding to assess G protein coupling, correlated with the level of receptor expression. Furthermore, among several antagonists tested, only fluphenazine and trifluoperazine exhibited clearly detectable inverse agonist activity. This differs from the D2S receptors, where most antagonists were reported to display full inverse agonism. Differences between inverse agonist effects of D2L and D2S antagonists may be relevant to the treatment of diseases involving dopamine D2 receptors.

Cell Line↗

PubMed2000

Endoscopic neck dissection in an animal model: comparison of nodal yield with open-neck dissection.

OBJECTIVE: To evaluate the possibility, complications, and efficacy of endoscopic neck dissection (END) in a porcine model. DESIGN: Experimental self-controlled study. SUBJECTS: Minipigs. INTERVENTION: Endoscopic neck dissection was performed using general anesthesia with techniques adapted from laparoscopic surgery. The tissue specimens removed were divided according to porcine equivalents of human neck groups. After the completion of END, open-neck dissection was performed using standard surgical techniques, and the remaining tissue within each neck group was retrieved. A pathologist evaluated each specimen without knowing its exact origin in terms of neck group or side and the type of surgical technique used. For each specimen, the number of retrieved lymph nodes and their anatomical integrity were analyzed. RESULTS: Ten neck dissections were performed in 8 minipigs without any major complications. The number of retrieved lymph nodes by END was 18.4 +/- 7.4 (mean +/- SD). Completed open-neck dissection retrieved an additional 3.3 +/- 1.8 lymph nodes. The efficacy rate of END was 88% +/- 10% (+/ -SD). The majority of retrieved lymph nodes were intact, with less than 5% of nodes exhibiting crushing artifacts. CONCLUSIONS: Endoscopic neck dissection in a porcine model seems to be free of major complications and able to retrieve the majority of neck lymph nodes. A larger number of animals and their survival need to be studied before human studies can begin.

Animals↗

PubMed2000

Regioselective synthesis and electron impact mass spectral fragmentation differentiation of 2- or 3-isopropylthio, phenylthiosuccinic acid 4-methyl/isopropyl ethers.

2- and 3-isopropylthio/phenylthiosuccinic acid 4-methyl/isopropyl esters were synthesized regioselectively by Michael additions of isopropylthiol/thiophenol to maleic anhydride, followed by alcoholysis with methanol/isopropanol. Their mass spectrometric behavior has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under electron impact ionization. All compounds show a tendency to eliminate an alkoxy group, an alcohol, or an alkoxycarbonyl group from the respective molecular ion. Some molecular ions also show a tendency to eliminate a molecule of water, propene or CO(2). The [M - MeCH = CH(2)](+) ions could further lose H(2)O to form substituted succinic anhydride ions, or lose CO(2) to form 3-substituted propionic acid ions. Both of these ions could further yield other small fragment ions by loss of CO(2)H, CO or other small fragments. It has been found that 2-isopropylthio- and 3-phenylthiosuccinic acid 4-esters show more abundant [M - H(2)O](+) peaks than their 3-isopropylthio and 2-phenylthio isomers in their mass spectra.

Carboxypeptidases↗

PubMed2000

Mutational analysis of GLUT1 (SLC2A1) in Glut-1 deficiency syndrome.

Fifteen children presenting with infantile seizures, acquired microcephaly, and developmental delay were found to have novel heterozygous mutations in the GLUT1 (SLC2A1). We refer to this condition as the Glut-1 Deficiency Syndrome (Glut-1 DS). The encoded protein (Glut-1), which has 12 transmembrane domains, is the major glucose transporter in the mammalian blood-brain barrier. The presence of GLUT1 mutations correlates with reduced cerebrospinal fluid glucose concentrations (hypoglycorrhachia) and reduced erythrocyte glucose transporter activities in the patients. We used Florescence in situ hybridization, PCR, single-stranded DNA conformational polymorphism, and DNA sequencing to identify novel GLUT1 mutations in 15 patients. These abnormalities include one large-scale deletion (hemizygosity), five missense mutations (S66F, R126L, E146K, K256V, R333W), three deletions (266delC, 267A>T; 904delA; 1086delG), three insertions (368-369 insTCCTGCCCACCACGCTCACCACG, 741-742insC, 888-889insG), three splice site mutations (197+1G>A; 1151+1G>T; 857T>G, 858G>A, 858+1del10), and one nonsense mutation (R330X). In addition, six silent mutations were identified in exons 2, 4, 5, 9, and 10. The K256V missense mutation involved the maternally derived allele in the patient and one allele in his mother. A spontaneous R126L missense mutation also was present in the paternally derived allele of the patient. The apparent pathogenicity of these mutations is discussed in relation to the functional domains of Glut-1.

Alternative Splicing↗

PubMed2000

The tumorigenic and angiogenic effects of MGSA/GRO proteins in melanoma.

Continuous expression of the MGSA/GROalpha, beta, or gamma chemokine bestows tumor-forming capacity to the immortalized murine melanocyte cell line, melan-a. The mechanism for this transformation is unclear, although both autocrine and paracrine processes are possible because melan-a cells as well as endothelial cells express a low level of the receptor for this ligand. To further define the role of MGSA/GRO proteins in melanocyte transformation, two types of experiments were designed to neutralize the biological effects of MGSA/GRO in the transfected melan-a clones: (1) the effect of neutralizing antiserum to MGSA/GRO proteins on melan-a tumor growth was assessed; (2) the tumor-forming capacity of melan-a clones expressing ELR motif-mutated forms of MGSA/GRO with compromised receptor affinity was compared to the tumor-forming capacity of clones expressing wild-type MGSA/GRO. These experiments revealed that SCID mice inoculated with MGSA/GROalpha- or gamma-expressing melan-a cells and subsequently treated with antiserum to the respective chemokine exhibited decreased tumor growth. This reduction in tumor growth was accompanied by declining angiogenic activity in MGSA/GROgamma-expressing tumors. Moreover, athymic nude mice injected with melan-a cells expressing ELR-mutant forms of MGSA/GROalpha exhibited markedly impaired tumor-forming capacity compared with those mice injected with melan-a clones expressing wild-type MGSA/GRO. These data suggest that continuous expression of MGSA/GRO proteins may facilitate tumor growth by stimulating the growth of microvessels into the tumor (paracrine) and by affecting melanocyte growth (autocrine).

Animals↗

PubMed2000

High-Resolution Fourier Transform Emission Spectroscopy of the TiCl Radical in the 420-nm Region.

Emission spectra of the TiCl radical in the 420-nm region have been observed at a resolution of 0.04 cm(-1) using a Fourier transform spectrometer. A new electronic assignment of (4)Gamma-X(4)Phi has been proposed. Rotational analysis has been provided for the 0-0 and 1-1 vibrational bands of the (4)Gamma(5/2)-X(4)Phi(3/2) and (4)Gamma(7/2)-X(4)Phi(5/2) spin components and the 0-0 band of (4)Gamma(9/2)-X(4)Phi(7/2). Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Effects of prostaglandins and leukotrienes on hypoxic pulmonary vasoconstriction in rats.

To investigate the effects of prostaglandins (PGs) and leukotrienes (LTs) on hypoxic pulmonary vasoconstriction (HPV), in vivo rats experiment and in vitro perfused lung experiment were conducted. The effect of hypoxia on hemodynamics, concentrations of TXB2 and 6-keto-PGF1 alpha in serum and lung tissue during hypoxia and effects of PGs and LTs on HPV were observed. The results showed that pulmonary arterial pressure (Ppa) and pulmonary vascular resistance were increased during hypoxia, but cardiac output and systemic arterial pressure were decreased. There were increases of the concentrations of TXB2 and 6-keto-PGF1 alpha and their ratio in serum and lung tissue during hypoxia. After use of cyclooxygenase inhibitor (indomethacin) in vivo and in vitro, HPV was augmented respectively, but after use of lipoxygenase inhibitor (diethylcorbamazine) or leukotriene receptor blocker (LY-171883), HPV was attenuated. It was suggested that LTs mediated pulmonary vasoconstriction, PGs inhibited pulmonary vasoconstriction and they played a modulating role during hypoxia.

6-Ketoprostaglandin F1 alpha↗

PubMed2000

Experimental study on the effect of ligustrazine in the prevention of intimal proliferation of deendothelial artery.

To evaluate the possibility of employing ligustrazine in the prevention of restenosis, the effects of ligustrazine on the intimal thickening of air-injured carotid artery of rats were investigated, and the effects of ligustrazine on the proliferation of rabbit aortic median smooth muscle cells (SMCs) cultivated in vitro were examined. Artery injury model of 18 rats of about 3 months old was established by Fishman air-dry method. Fourteen days after operation, the maximal artery intimal and medial thickness of the control and ligustrazine group was measured on the image analysis system. Using cell counting and thymidine (3H-TdR) up-take method, we also examined the effects of ligustrazine on the proliferation of aortic median SMC from 4 rabbits. Ligustrazine was found to inhibit the proliferation and 3H-TdR up-take of SMC in a dose-dependent manner in vitro (P < 0.05 or P < 0.01 vs control). It also inhibited the intimal thickening of rat arteries after deendothelialization. The maximal intimal thickness of ligustrazine group was much thinner than that of the control (35.9 +/- 3.8 microns vs 80.2 +/- 23.4 microns, P < 0.01). It was showed that ligustrazine could be used for prevention of restenosis in clinical practice.

Animals↗

PubMed2000

Effects of aprotinin on serum interleukin-2 and soluble interleukin-2 receptor during cardiopulmonary bypass.

Interleukin-2 and its receptor are of importance in regulating immunity responses. The changes of interleukin-2 (IL-2) and soluble interleukin-2 receptor (IL-2R) during heart valve (s) replacement operation and effects of aprotinin on them were observed. Twenty patients undergoing heart valve(s) replacement were randomly divided into two groups: control group (n = 10) and aprotinin group (n = 10). In aprotinin group, 1,000,000 KIU aprotinin was given by vein injection and then 2,000,000 KIU was given as a bolus in prime. Blood samples were collected before CPB, right after CPB and on the 1st, 3rd and 7th postoperative day (POD) for serum IL-2 and sIL-2R determination. Results showed that after CPB, IL-2 was reduced and sIL-2R increased. Meanwhile, serum IL-2R was lower in aprotinin group than that of control. It is concluded that the immunity depression after CPB is associated with low level of IL-2 and high level of sIL-2R and aprotinin can ameliorate the situation.

Aprotinin↗

PubMed2000

The effect of coriaria lactone on NMDA receptor mediated currents in rat hippocampal CA1 neurons.

To investigate the exact mechanism of epileptogenesis induced by coriaria lactone (CL), the effect of CL on NMDA receptor mediated current (IAsp) in rat hippocampal CA1 neurons was investigated by using nystatin perforated whole-cell patch clamp. 10(-6)-10(-4) mol/L Asp acted on NMDA receptors and elicited an inward current (IAsp) at a holding potential (VH) of -40 mV in presence of 10(-6) mol/L glycine and absence of Mg2+ extracellularly. CL enhanced NMDA receptor mediated current induced by Asp, but had no effect on threshold concentration, EC50, Hill coefficient as well as maximal-effect concentration and reversal potential of IAsp. The effect had no relationship with holding potential. These results showed that CL could enhance NMDA receptor mediated current to increase [Ca2+]i of neurons by acting on Gly site, thereby inducing epilepsy.

Animals↗

PubMed2000

Comparative genomic sequence analysis of the Williams syndrome region (LIMK1-RFC2) of human chromosome 7q11.23.

Williams syndrome (WS) is a complex neurodevelopmental disorder arising from a microdeletion at Chr band 7q11.23, which results in a hemizygous condition for a number of genes. Within this region we have completely characterized 200 kb containing the genes LIMK1, WBSCR1, and RFC2. Evidence was also found for WBSCR5 in this region, but not the previously proposed genes WSCR2 and WSCR6. The syntenic region in mouse was also sequenced (115 kb) and characterized, and a comparative sequence analysis with a percent identity plot (PIP) easily allowed us to identify coding exons. This genomic region is GC rich (50.1% human, 49.9% mouse) and contains an unusually high abundance of repetitive elements consisting primarily of Alu (45.4%, one of the highest levels identified to date) in human, and the B family of SINES (30.6% of the total sequence) in mouse. WBSCR1 corresponds to eukaryotic initiation factor 4H, identified in rabbit, and is herein found to be constitutively expressed in both human and mouse, with two RNA and protein products formed (exon 5 is alternatively spliced). The transcription pattern of WBSCR5 was also examined and discussed along with its putative amino acid sequence.

Amino Acid Sequence↗

PubMed2000

Distribution of fibrillin I in extracellular matrix and epithelia during early development of avian embryos.

Fibrillin microfibrils are widely distributed components of extracellular matrices that function in the formation of elastin, serve structural roles and provide substrates for cell adhesion. To determine when and how fibrillin-1 (fib-1) may function in early development we have examined the temporal and spatial distribution of fib-1 in chicken embryos. Using homologous PCR we amplified and cloned a 407 nt fragment of chicken cDNA that appears to code for an orthologue of FBN-1. Bacterially expressed protein was used to prepare two monoclonal antibodies, both of which recognize a 350 kD band in immunoblots or immunoprecipitates in supernatants of chicken embryonic aorta cells or human MG-63 cells. Both antibodies recognize fibrillar material associated with the surfaces of cultured cells. The antibodies appear to be specific for fib- as there was only weak cross reactivity to a bacterially expressed fragment from the corresponding region of fib-2 and the pattern of immunofluorescence in embryonic tissue is distinctly different from that of JB-3, a fib-2 specific antibody (Rongish et al. 1998). In embryos, fib-1 is first detected at stage 6 in the epiblast during gastrulation. In subsequent stages fib-1 fibers appear in all tissues and are present throughout the first 6 days of development. Immunoreactive fibers are present in basal laminae and mesenchyme filled spaces, but they also form random arrays with an apical-basal polarity within epithelia. Using primers specific for FBN-1 and FBN-2 in RT-PCR reactions we confirm the presence of fib- 1 and fib-2 mRNA in early embryonic stages. This temporal and spatial distribution indicates fib-1 has functions in early development that are distinct from fib-2.

Amino Acid Sequence↗

PubMed2000

Novel injectable neutral solutions of chitosan form biodegradable gels in situ.

A novel approach to provide, thermally sensitive neutral solutions based on chitosan/polyol salt combinations is described. These formulations possess a physiological pH and can be held liquid below room temperature for encapsulating living cells and therapeutic proteins; they form monolithic gels at body temperature. When injected in vivo the liquid formulations turn into gel implants in situ. This system was used successfully to deliver biologically active growth factors in vivo as well as an encapsulating matrix for living chondrocytes for tissue engineering applications. This study reports for the first time the use of polymer/polyol salt aqueous solutions as gelling systems, suggesting the discovery of a prototype for a new family of thermosetting gels highly compatible with biological compounds.

Animals↗

PubMed2000

The relationship between neurokinin-1 receptor and substance P in the medullary dorsal horn: a light and electron microscopic immunohistochemical study in the rat.

The synaptic relationship between substance P (SP) and its receptor, i.e. neurokinin-1 receptor (NK1R), was examined in the superficial laminae of the caudal subnucleus of the spinal trigeminal nucleus (medullary dorsal horn; MDH) of the rat. For confocal laser-scanning microscopy, double-immunofluorescence histochemistry for NK1 and SP was performed. In electron microscopic double-immunolabeling study, immunoreactivity for NK1R was detected with the silver-intensified gold method, while immunoreactivity for SP was detected with peroxidase immunohistochemistry. SP-immunoreactive axon terminals were observed to be in synaptic (mostly asymmetric) contact with NK1R-immunoreactive neuronal profiles in lamina I and lamina IIo. Although some SP-immunoreactive axon terminals were in synaptic contact with NK1R-immunoreactive sites of plasma membranes, NK1R-immunoreactivity was observed at both synaptic and non-synaptic sites of plasma membrane. Thus, SP released from axon terminals might not only act on NK1Rs facing the SP-containing axon terminals, but also diffuse in the extracellular fluid for distances larger than the synaptic cleft to act on NK1Rs at some distances from the synaptic sites.

Animals↗

PubMed2000

Effects of mandibular setback on the temporomandibular joint: a comparison of oblique and sagittal split ramus osteotomy.

PURPOSE: This investigation studied the changes in temporomandibular joint function and condylar position after mandibular setback using different ramus osteotomies. PATIENTS AND METHODS: The sample consisted of 50 Chinese adults with mandibular prognathism. Twenty-eight of the patients underwent intraoral oblique ramus osteotomy (IORO), and 22 received sagittal split ramus osteotomy (SSRO) with rigid internal fixation (RIF). TMJ symptoms and radiographic findings were evaluated preoperatively and postoperatively. RESULTS: After surgery in the IORO group, the TMJ radiographs showed a significant anterior-inferior displacement of the condyle. Seventy-five percent of the preoperatively symptomatic patients reported fewer or no TMJ symptoms and no preoperatively asymptomatic patients developed new TMJ symptoms. In the SSRO group, the TMJ radiographs showed a posterior displacement of the condyle. Sixty percent of the preoperatively symptomatic patients had no improved TMJ function and 8% of asymptomatic patients developed TMJ symptoms after surgery. CONCLUSION: The results of this study show that IORO with MMF appears to be more favorable to the TMJ than the SSRO with RIF; IORO is particularly good in orthognathic surgery patients with preoperative TMJ symptoms.

Adult↗