Biomedical subjects

J Xiang

Publications and source records attributed to J Xiang.

At least 91 records · Page 5Linked to original sources

PubMed1999

[The restoration of the "double peak" in OCT images based on inverse Wiener].

It has been found that the high reflectivity film of the reference mirror in OCT may cause a socalled "double peak effect" in the result images. To eliminate this a restoration algorithm is proposed here. The method is based on the mathematical modals of the point-spread function of OCT with consideration of double peak effect. The power spectrum of the noise and signal are estimated by the average smooth periodogram method. An inverse wiener filter algorithm, which avoids the illness condition in common inverse filter, gives the final restored images. The algorithm is also capable of the image degrading recovery due to the aberration and the band-limited spectrum.

Algorithms↗

PubMed1999

[Spectroscopic study of the 1pig Rydberg states of Na2].

Six highly excited 1pig states of the Na2 molecule have been investigated by optical-optical double resonance (OODR) flourescence excitation spectroscopy. Absolute vibrational numberings are determined and molecular constants and RKR potential curves are obtained. The lowest 10 1pig states have been relabeled according to the hydrogenic nllambda characters of the Rydberg orbital and classified into core-penetrating and core-nonpenetrating Rydberg states.

English Abstract↗

PubMed1999

[The application of ion detection in the study of spectroscopy of Na2].

Ion detection technique has been successfully used in the study of Rydberg states of Na2 by pulse optical-optical double resonance. High-lying Rydberg states near ionization limit have been observed and high sensitive and high gain spectra have been obtained. This technique is very useful for molecular spectroscopy.

English Abstract↗

PubMed1998

Efficient gene delivery into epstein-barr virus (EBV)-transformed human B cells mediated by replication-defective herpes simplex virus-1 (HSV-1): A gene therapy model for EBV-related B cell malignancy.

Subgroups of the B cell malignancies are known to be associated with Epstein-Barr virus (EBV) infection, especially in immunocompromised patients. These are fatal and refractory to conventional antineoplastic therapy. B cells are usually post-mitotic cells and even mitogen activated or transformed B cells have shown relative resistance against viral mediated gene transfer. To address this issue, we employed a replication-defective herpes simplex virus-1 (HSV-1) to mediate gene transfer into EBV-transformed B cells. The virus expresses the herpes simplex virus thymidine kinase (HSV-TK) and the E. coli lacZ reporter genes and is designated T0Z.1. We used the lymphoblastoid cell line SWEIG as a model for human EBV-related B cell malignancy. This cell line was established by in vitro EBV infection of primary human peripheral blood mononuclear cells. When SWEIG cells were infected with T0Z.1, X-gal staining revealed lacZ expression in more than 20% cells even at multiplicity of infection (MOI) as low as 1 and the expression persisted for at least one week. Ganciclovir (GCV) administration after T0Z.1 infection effectively decreased the number of the infected tumor cells in a dose-responsive manner. Viral toxicity was analyzed by cell proliferation assay (MTS assay) and found to be little even at 10 MOI infection. Three MOI of the virus yielded maximum antineoplastic effect and more than 50% tumor cells were killed by HSV-TK/GCV. These results suggest the potential utility of replication-defective HSV-1 for the treatment of EBV-related B cell malignancies.

Antiviral Agents↗

PubMed1998

Functional knock-out of c-myb by an intracellular anti-c-Myb single-chain antibody.

Aberrant expression of the c-myb proto-oncogene is a key factor in the development of the neoplastic phenotype in a variety of contexts. On this basis, it has been proposed that ablation of c-myb function might be an effective approach for therapy. To this end, we have employed an intracellular single-chain antibody (sFv) approach to achieve the functional knock-out of the c-Myb onco-protein. We derived an anti-c-Myb sFv, which was configured into eukaryotic expression plasmids. We confirmed the expression of the cytoplasmic and nuclear forms of the sFvs in the correct subcellular compartments by immunofluorescent staining. Importantly, the anti-c-Myb sFvs strongly inhibited the transactivation activity of c-Myb. Furthermore, cytotoxic effect of the sFv was observed only in the c-Myb positive cell line K562. These results suggest that anti-c-Myb sFv is a valuable tool for understanding the molecular mechanisms of c-myb induced transformation. In addition, this approach may have potential utility in the gene therapy for c-myb-dependent malignant diseases.

Amino Acid Sequence↗

PubMed1998

Induction of apoptosis by SB202190 through inhibition of p38beta mitogen-activated protein kinase.

p38, a subfamily of the mitogen-activated protein kinase, regulates gene expression in response to various extracellular stimuli. The pyridinyl imidazoles like SB202190 are specific inhibitors of p38alpha and p38beta and have been widely used in investigation of the biological functions of p38. Here we show that SB202190 by itself was sufficient to induce cell death, with typical apoptotic features such as nucleus condensation and intranucleosomal DNA fragmentation. SB202190 stimulated the activity of CPP32-like caspases, and its apoptotic effect was completely blocked by the protease inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone and expression of bcl-2. In addition, SB202190 was able to potentiate apoptosis induced by Fas(APO-1) ligation or UV irradiation. Expression of p38beta attenuated the apoptotic effect of SB202190 and the cell death induced by Fas ligation and UV irradiation. In contrast, expression of p38alpha induced cell death mildly. These results indicate that SB202190 induces apoptosis through activation of CPP32-like caspases and suggest that distinct members of the p38 subfamily of mitogen-activated protein kinase have different functions in apoptosis.

Apoptosis↗

PubMed1998

Choroid plexus histidine transport.

System-N transport plays an important role in l-glutamine uptake into isolated rat choroid plexus but its role in the transport of another System-N substrate, l-histidine, has yet to be determined. Similarly, the possible effects on System-N mediated l-histidine transport of changes in pH and extracellular l-glutamine, such as occur in cerebral ischemia and hepatic encephalopathy, have yet to be examined. In the absence of competing amino acids, l-[3H]histidine uptake in isolated rat choroid plexus was mediated by both Na+-independent and Na+-dependent transport. The former was inhibited by 2-amino-2-norbornane carboxlic acid, indicating System-L transport, while the latter appears System-N mediated as it was inhibited by three System-N substrates but not substrates for System-A and -ASC. The Na+-dependent uptake had a Km of 0.2 mM and a Vmax of 1.4 nmol/mg/min. It accounted for 30% of l-histidine uptake in the presence of physiological concentrations of amino acids. Reductions in pH markedly inhibited Na+-dependent but not Na+-independent transport indicating that, as in liver but not neurons, System-N mediated transport at the choroid plexus is pH sensitive. Increases in l-glutamine concentration in the pathophysiological range reduced l-histidine uptake via both System-L and -N.

Animals↗

PubMed1998

Gene transfer into hematopoietic cells of mouse and its in vivo expression after transplantation.

We have shown previously that high-efficient gene transfer can be attained in primary hematopoietic cells using liposome-mediated gene transfer strategy. In order to examine the stability of gene expression mediated by this gene transduction protocol, we observed the expression of marker gene in vivo by using bone marrow transplantation (BMT) to engraft lethally irradiated mouse with the genetically modified hematopoietic cells. The results showed that the mouse transplanted with appropriated number of transduced cells remained alive and healthy. The PCR analysis and G418 selection of the spleen colonies and bone marrow cells isolated from lethally irradiated animals 15 days and 30 days after injection of genetically modified bone marrow cells showed that the progeny cells of the transduced hematopoietic stem cells still contained and expressed the transduced genes, suggesting that the hematopoietic system is at least partially re-constructed by the stem cells with marker gene and that the stable expression of foreign genes in vivo can be attained by using this easy and harmless transduction protocol. These findings provide experimental basis for clinician to further investigate the biology of marrow reconstruction and the mechanism of leukemia relapse after BMT.

Animals↗

PubMed1998

Expression of functional domain of chicken gizzard calponin.

A full-length cDNA of the function domain of wild-type chicken gizzard calponin was cloned into expression vector pAED4 and the recombinant function domain of wild-type calponin was expressed in an Escherichia coli expression system. The actin domain of calponin (CaP-B) can bind with actin and it is a requisite for its inhibition of ATPase and vasoconstriction of smooth muscle. In this study, the cDNA of CaP-B was inserted into vector pAED4 by direction-cloning method. The cDNA of CaP-B was obtained with PCR cloning technique. The recombinant DNA pAED4-Cap-B was transformed into E. coli BL21 (DE3) and identified with the restriction analysis. The bacterial clones containing transformants were induced to be highly expressed in E. coli BL21 (DE3). The target protein was detected and identified by Western Blot analysis. The content of target protein was as high as 10% of the whole protein after overnight (16 h) culture. The results confirmed that Cap-B was relatively highly expressed in E. coli.

Animals↗

PubMed1998

Effects of tactile interference stimulation on somatosensory evoked magnetic fields following tibial nerve stimulation.

We studied the effects of interfering tactile stimulation applied to the foot ipsilateral and contralateral to the stimulation on somatosensory evoked magnetic fields (SEFs) following tibial nerve stimulation at the ankle. Equivalent current dipoles (ECDs) of all 4 components, 1M-4M, in all sessions were estimated to be very close each other, around the foot area of the primary sensory cortex (SI). The 1M, 2M and 4M components were significantly reduced in amplitude by the ipsilateral-foot interference, and we consider that this phenomenon is due mainly to 'saturation' of the neurons in area 3b of the SI. In contrast, the 3M component was significantly enhanced in amplitude by the contralateral-foot interference. We suspect that this result was due to the effects of neuronal activities in areas 2, 5 and/or 7, which receive inputs from both sides of the body, i.e. to 'bilateral function'. Considering the various types of interference effects on SEFs and somatosensory evoked potentials (SEPs) observed in not only the present, but also in the previous studies, we conclude that both SEFs and SEPs following tibial nerve stimulation are generated mainly by ascending signals mediated by cutaneous fibers of the peripheral nerves rather than the muscle afferents.

Adult↗

PubMed1998

One hundred seventy-fold increase in excretion of an FV fragment-tumor necrosis factor alpha fusion protein (sFV/TNF-alpha) from Escherichia coli caused by the synergistic effects of glycine and triton X-100.

To target tumor necrosis factor alpha (TNF-alpha) to tumor cells, recombinant DNA techniques were used to construct and express the fused gene VKLVH-TNF-alpha, which encodes the secreted form of single-chain fusion protein sFV/TNF-alpha in Escherichia coli. sFV/TNF-alpha was secreted into the culture medium and purified by affinity chromatography. The production of the fusion protein in the culture medium under the optimal conditions of 30 degrees C and 37 micromol of isopropyl-beta-D-thiogalactopyranoside (IPTG) per liter was 16- and 5-fold higher than that under the standard conditions of 37 degrees C and 1 mmol of IPTG per liter. Fusion protein excretion into culture medium with 2% glycine, 1% Triton X-100, or both of these two chemicals was either 14-, 38-, or 170-fold higher, respectively than that without the two chemicals. The final yield of sFV/TNF-alpha was estimated to be 50 mg/liter. The loss of integrity of the cellular membrane may be a potential mechanism for enhancement of fusion protein production and excretion by treatment with glycine and Triton X-100. This study thus provides a practical, large-scale method for more efficient production of the heterologous fusion protein sFV/TNF-alpha in E. coli by using glycine and Triton X-100.

Culture Media↗

PubMed1998

Characterization of hepatitis G virus (GB-C virus) particles: evidence for a nucleocapsid and expression of sequences upstream of the E1 protein.

Hepatitis G virus (HGV or GB-C virus) is a newly described virus that is closely related to hepatitis C virus (HCV). Based on sequence analysis and by evaluation of translational initiation codon preferences utilized during in vitro translation, HGV appears to have a truncated or absent core protein at the amino terminus of the HGV polyprotein. Consequently, the biophysical properties of HGV may be very different from those of HCV. To characterize HGV particle types, we evaluated plasma from chronically infected individuals with and without concomitant HCV infection by using sucrose gradient centrifugation, isopycnic banding in cesium chloride, and saline density flotation centrifugation. Similar to HCV, HGV particles included an extremely-low-density virion particle (1.07 to 1.09 g/ml) and a nucleocapsid of approximately 1.18 g/ml. One major difference between the particle types was that HGV was consistently more stable in cesium chloride than HCV. Plasma samples from chronically HGV-infected individuals and controls were assessed by a synthetic peptide-based immunoassay to determine if they contained HGV antibody specific for a conserved region in the coding region upstream of the E1 protein. Chronically HGV-infected individuals contained antibody to the HGV core protein peptide, whereas no binding to a hepatitis A virus peptide control was observed. Competitive inhibition of binding to the HGV peptide confirmed the specificity of the assay. These data indicate that HGV has a nucleocapsid and that at least part of the putative core region of HGV is expressed in vivo.

Amino Acid Sequence↗

PubMed1998

[Rescue and prevention of serious systemic toxicity following local anesthesia to mucous membranes of tetracaine].

Tetracaine remains a popular agent in clinical for the purpose of local anesthesia to mucous membranes. Its potential for systemic absorption and resulting toxicity has been seldom emphasized. One case of fatality from tetracaine pharyngeal local anesthesia for fibro-laryngoscopic procedure is described. The pharmacologic basis, clinical features, rescue and prevention for systemic toxicity is discussed.

Adolescent↗

PubMed1998

[Chemical constituents of Bufo Siccus].

OBJECTIVE: To study the chemical constituents of Bufo Siccus. METHOD: Based on silica column chromatography six compounds were obtained from the alcoholic extract of Bufo Siccus and identified by physico-chemical and spectroscopic analyses. RESULT: The compounds were identified as cholesterol, beta-sitosterol, resibufogenin, cinobufagin, bufalin and gamabufotalin. CONCLUSION: Studies on the chemical constituents of Bufo Siccus were reported for the first time.

Animals↗

PubMed1998

[Surgical treatment of the hypopharyngeal and cervical esophageal carcinoma].

OBJECTIVE: To review the experience of surgical treatment of hypopharyngeal and cervical esophageal carcinoma. METHOD: Seventy-six patients with squamous-cell carcinoma of the hypopharynx and cervical esophagus underwent surgery in our department from 1980 to June 1997. The site of the tumour was in hypopharynx in 31 patients and in cervical esophagus in 45. RESULT: The resectability rate of hypopharyngeal carcinoma (HPC) was 98.6% (30/31). The types of the esophageal reconstruction included pharyngo-esophageal anastomosis (3 patients) platysmamyocutaneous flaps reconstruction (PMFR) (12) free jejunal interposition (3) and gastric tube transposition following total pharyngolaryngo esophagectomy (12). The resectability rate of cervical esophageal carcinoma (CEC) was 91% (41/45). The esophageal construction applied gastric tube after esophagectomy without thoracotomy except one. The postoperative morbidity was 36.5% for gastric tube reconstruction (including one died of heart failure), 33.3% (1/3) for free jejunal interposition and zero for PMFR. The overall follow-up was from 2 to 108 months (median: 56.5 months) and the 1-, 3-, 5-year survival rates were 79.3%, 60% and 31.6% respectively for HPC and 68.3%, 9.5%, 0% respectively for CEC. CONCLUSION: Our data demonstrated that the resectability rate of the HPC and CEC was quite high but the long-term result of HPC was better than that of CEC. The PMFR after pharyngolaryngo-cervicalesophagectomy was a safe, effective operation with low morbidity and excellent long-term results.

Adult↗

PubMed1997

The effects of hypo- and hyperkalemia on choroid plexus potassium transport.

To examine the mechanisms involved in cerebrospinal fluid (CSF) K+ homeostasis, lateral ventricle choroid plexuses were isolated from rats fed low, normal or high K+ diets for 2 weeks. Potassium (86Rb) influx and efflux were then examined in vitro. Dietary hypo- and hyperkalemia (2.8 +/- 0.1 and 6.8 +/- 0.3 mM) did not affect the efflux rate constant for 86Rb or the influx rate constant in the absence of inhibitors. However, the ouabain-sensitive portion of influx was only 1.9 +/- 0.5 microl/g per min in plexuses from hypokalemic rats compared to 4.5 +/- 0.5 microl/g/min in controls (P < 0.001). This change in Na+/K+-ATPase activity was reflected in an increasing amount (Western blot) of the alpha1 and beta1 subunits of this pump with increasing plasma K+ concentration (P < 0.05) whereas the beta2 subunit was unaffected. The other known choroid plexus K+ uptake mechanism, bumetanide-sensitive K+ cotransport, was unaffected by dietary K+ manipulation. In normo- and hyperkalemic rats, the sum of the ouabain- and bumetanide-sensitive fluxes could account for all of 86Rb uptake. However, in hypokalemic rats a major component (40%) of uptake could not be accounted for by either mechanism. This unidentified mechanism may be a basolateral uptake mechanism involved in increasing K+ transport from blood to CSF during hypokalemia.

Animals↗

PubMed1997

Genetic engineering of a recombinant fusion possessing anti-tumor F(ab')2 and tumor necrosis factor.

The construction, synthesis and expression of a genetically engineered bifunctional antibody/cytokine fusion protein is described. In order to target alpha-tumor necrosis factor (TNF) to tumor cells, recombinant antibody techniques were used to construct an RM4/TNF fusion protein containing the chimeric anti-tumor F(ab')2 (RM4) as well as the TNF moiety. The recombinant cDNA of human TNF was linked to the 3' end of the chimeric heavy-chain gene fragment (M4) containing the VH, the CH1 and the hinge region to form the fused heavy-chain gene fragment M4-TNF. Transfection of the M4-TNF gene fragment into a VKCK cell line producing the chimeric light-chain of the same antibody allowed the transfectant secreting the bifunctional fusion protein RM4/TNF. The RM4/TNF was purified by affinity chromatography. Our data showed that RM4/TNF retained the TAG72 antigen-binding reactivity as well as TNF activity as measured by ELISA, Western blotting, flow cytometry analysis, immunohistochemistry and cytotoxicity assays using the human colon cancer cell line LS174T. Therefore, the bifunctional fusion protein RM4/TNF may prove useful in targeting the biological effects of TNF to tumor cells, and in this way stimulate the immune destruction of tumor cells.

Adenocarcinoma↗

PubMed1997

Acute lung injury induced by a commercial leather conditioner.

Following a formulation change, a leather conditioner was involved in a 1992 nationwide outbreak of respiratory illness. We investigated the composition and toxicity of the conditioner produced before (previous product) and after (new product) the disease outbreak. The new product induced tachypnea, pulmonary edema, pulmonary hemorrhage, and sporadic deaths in exposed guinea pigs and rats. Ultrastructurally, these changes were associate with direct pulmonary cytotoxicity characterized by necrosis of alveolar type I cells and alveolar septal interstitial edema. Chemical analyses suggested major alterations in the fluorohydrocarbon constituents in the new formulation of the leather conditioner. While these alterations could not be specifically identified, they appeared to include changes from fluoralkanes to fluoroalkenes, fluorophenyl, and/or fluoroalcohol compounds. Changes in solvent composition were consistent with traces of 2-butoxyethanol and isomers of dipropylene glycol methyl ether, and additional C10-C12 alkanes. In this study, we demonstrated the toxicity of the new product in laboratory animals. Some of the altered constituents of the new product have been identified and are potential candidates for additional investigations to identify specific etiologic agents.

Acetates↗