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Biomedical subjects

G Zheng

Publications and source records attributed to G Zheng.

At least 37 records · Page 2Linked to original sources
PubMed2001

Photochemical and electrochemical properties of zinc chlorin-C60 dyad as compared to corresponding free-base chlorin-C60, free-base porphyrin-C60, and zinc porphyrin-C60 dyads.

The photochemical and electrochemical properties of four chlorin-C60 or porphyrin-C60 dyads having the same short spacer between the macrocycle and the fullerene are examined. In contrast with all the previous results on porphyrin-fullerene dyads, the photoexcitation of a zinc chlorin-C60 dyad results in an unusually long-lived radical ion pair which decays via first-order kinetics with a decay rate constant of 9.1 x 10(3) x s(-1). This value is 2-6 orders of magnitude smaller than values reported for all other porphyrin or chlorin donor-acceptor of the molecule dyad systems. The formation of radical cations of the donor part and the radical anion of the acceptor part was also confirmed by ESR measurements under photoirradiation at low temperature. The photoexcitation of other dyads (free-base chlorin-C60, zinc porphyrin-C60, and free-base porphyrin-C60 dyads) results in formation of the ion pairs which decay quickly to the triplet excited states of the chlorin or porphyrin moiety via the higher lying radical ion pair states as is expected from the redox potentials.

Carbon↗
PubMed2001

A new locus for hereditary gingival fibromatosis (GINGF2) maps to 5q13-q22.

Gingival fibromatosis (GINGF) is an oral disorder characterized by enlargement of the gingiva. It occurs either as the sole phenotype or combined with other symptoms. Thus far, one GINGF locus has been mapped on chromosome 2, at 2p21, and a second possible locus has been mapped to 2p13. However, the genes responsible for this disorder have not been elucidated. We identified a four-generation Chinese GINGF family in which the disease manifests within 1 year after birth. After exclusion of the two known GINGF loci in this family, we performed a genome-wide search to map the chromosome location of the responsible gene. We identified a new locus, GINGF2, on chromosome 5q13-q22 with a maximum two-point lod score of 4.31 at D5S1721 (theta = 0.00). Haplotype analysis placed the critical region in the interval defined by D5S1491 and D5S1453. Within this region, calcium/calmodulin-dependent protein kinase IV (CAMK4) is a strong candidate.

Age of Onset↗
PubMed2001

Unique spin dynamics and unconventional superconductivity in the layered heavy fermion compound CeIrIn5: NQR evidence.

We report measurements of the 115In nuclear spin-lattice relaxation rate ( 1/T1) between T = 0.09 and 100 K in the new heavy fermion (HF) compound CeIrIn5. At 0.4 < or = T< or = 100 K, 1/T1 is strongly T-dependent, which indicates that CeIrIn5 is much more itinerant than known Ce-based HFs. We find that 1/T1T, subtracting that for LaIrIn5, follows a (1 / T+straight theta)3/4 variation with straight theta = 8 K. We argue that this novel feature points to anisotropic, due to a layered crystal structure, spin fluctuations near a magnetic ordering. The bulk superconductivity sets in at 0.40 K below which the coherence peak is absent and 1/T1 follows a T3 variation, which suggests unconventional superconductivity with line-node gap.

Journal Article↗
PubMed2001

Synthesis, photophysical properties, tumor uptake, and preliminary in vivo photosensitizing efficacy of a homologous series of 3-(1'-alkyloxy)ethyl-3-devinylpurpurin-18-N-alkylimides with variable lipophilicity.

Starting from methylpheophorbide-a, a homologous series of purpurinimides containing alkyl substituents at two different positions [as 3-(1(1)-O-alkyl) and 13(2)-N-alkyl] were synthesized. These compounds with variable lipophilicity (log P 5.32-16.44) exhibit long wavelength absorption near lambda(max)700 nm (epsilon: 45 000 in dichloromethane) with singlet oxygen ((1)O2) production in the range of 57-60%. The shifts in in vivo absorptions and tumor/skin uptake of these compounds were determined in C3H mice bearing RIF tumors by in vivo reflectance spectroscopy. The results obtained from a set of photosensitizers with similar lipophilicity (log P 10.68-10.88) indicate that besides the overall lipophilicity, the presence and position of the alkyl groups (O-alkyl vs N-alkyl) in a molecule play an important role in tumor uptake, tumor selectivity, and in vivo PDT efficacy. At present, all purpurinimide analogues are being evaluated at various doses, and experiments are underway to establish a quantitative structure-activity relationship on a limited set of compounds. The 1D and 2D NMR and mass spectrometry analyses confirmed the structures of the desired purpurinimides and the byproducts formed during various reaction conditions. The mechanisms of the formation of the unexpected 12-formyl- and 12-(hydroxymethyl)purpurinimides under certain reaction conditions are also discussed.

Animals↗
PubMed2001

Frameless optical computer-aided tracking of a microscope for otorhinology and skull base surgery.

OBJECTIVES: To integrate a digitally controlled operating microscope without a laser autofocus system into a frameless optical computer-aided surgery system and to test the accuracy and usability of this system in otorhinological surgery. DESIGN: Experimental study and case series. SETTING: Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Inselspital, and the Maurice E. Müller Institute for Biomechanics, University of Bern, Bern, Switzerland. PATIENTS: Eight computer-aided microscopic surgical procedures were performed between January and October 2000 on patients with various diseases of the anterior and lateral skull base. RESULTS: The practical accuracy of the navigated microscope on the lateral side of a cadaver skull was 2.27 +/- 0.25 mm and on the anterior side of the same skull was 2.07 +/- 0.35 mm. In all 8 cases of computer-aided microscopic surgery, no complications occurred. Clinical inaccuracy was 2 to 3 mm. CONCLUSION: Integration of a low-cost, non-laser autofocus microscope into our computer-aided surgery system was successfully performed and offers surgeons the ability to combine the precise optics of the operating microscope with the localization power of a computer-aided system.

Cadaver↗
PubMed2001

Enantioselective separation of epoxides by capillary electrophoresis employing sulfated beta-cyclodextrin as chiral selector.

A capillary electrophoresis method was developed for the enantioseparation of epoxide compounds. Sulfated beta-cyclodextrin was employed as a chiral selector. Phosphate-triethanolamine buffer showed a chiral separation effect when employing charged sulfated beta-cyclodextrin. The effect of pH, triethanolamine concentration and sulfated beta-cyclodextrin concentration on the resolution was studied. Methanol was tested as an organic modifier. Several other epoxides were successfully separated by the proposed method.

Journal Article↗
PubMed2001

In vivo inhibition of Fas ligand-mediated killing by TR6, a Fas ligand decoy receptor.

TR6, a member of the tumor necrosis factor (TNF) receptor superfamily, has recently been shown to bind to Fas ligand (FasL) and inhibit FasL-mediated cell killing in vitro. In the current study, we demonstrate that TR6 can block the lethal activity of FasL in multiple in vitro systems, and extend this finding to an in vivo model of hepatitis. The binding of human TR6 to human FasL was verified with BIAcore chip technology. Human primary hepatocytes, HT-29 cells and Jurkat cells were assayed for viability to demonstrate TR6 inhibition of FasL-mediated cytotoxicity in vitro. Human TR6 was also shown to cross-react with membrane-bound mouse FasL, since the in vitro cytotoxic activity of L929 cells transfected with murine FasL was inhibited in the presence of human TR6. In vivo, FasL-induced acute, lethal, fulminant hepatic apoptosis resulting in death within 2 h of intravenous injection into Fas+ mice, but not Fas- MRL/lpr mice. Pretreatment of mice with TR6 blocked FasL-induced mortality, presumably by attenuating FasL-induced hepatic apoptosis. Thus, in both in vitro and in vivo systems, TR6 acts as a functional FasL decoy receptor and may be clinically useful in the treatment of hepatitis and other diseases associated with FasL-mediated tissue injury.

Animals↗
PubMed2001

[Purification feasibility of malodorous waste gas contained H2S and CS2 by DBD technique].

Dielectric barrier discharge(DBD) technique was applied to remove H2S and CS2 in industrial waste gas. In the research of laboratory, when the voltage between two electrodes was 12 kV, 4 x 10(3) Pa H2S was discharged in air for 5 seconds, about 100% of H2S was transformed into H2O and SO2; 1.33 x 10(3) Pa CS2 was discharged in air for 15 seconds, about 80% of CS2 was transformed into CO2, CO and SO2. When the concentration of H2S and CS2 increased, the decomposition of them decreased. Based on the results, a DBD purification apparatus which can dispose 420 m3/h, 10 m/s waste gas was designed and manufactured, the removal rate of H2S can reach 89% and the energy consumption was 5.2 W.h/m3. It was concluded that the DBD technique is worth disposing malodorous industrial waste gases contained H2S and CS2.

Carbon Disulfide↗
PubMed2001

[Research on transparent apinoid enemator].

Transparent apinoid enemator is made of polymethacrylate material. It is composed of external shell, big cover, small cover, liquor drain tube and suspension belt. Lateral surface of the shell has 100-1500 ml volume mark. Liquor drain tube is made of PVC, its inner diameter is 6 mm. The cover can reduce contamination and maintain liquor temperature. The transparent enemator made by us can overcome the shortcomings of non-transparent enamel enemator which has been used for many years.

Animals↗
PubMed2001

[Impact of interstitial irradiation with 32P glass microspheres on cellular apoptosis of mice with the solid tumor S180].

OBJECTIVE: The aim of this study is to observe apoptotic changes of tumor cells in mice with the solid tumor S180 after interstitial irradiation with 32P glass microspheres. METHODS: Twenty mice with solid tumor S180 were divided into four groups. The control group was given normal saline. The experimental groups were given different doses of 32P glass microspheres (50, 150, 450uci per mouse) using interstitial implant. The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method was used to determine the apoptotic cells. RESULTS: The mean values of the apoptotic indexes of these groups were respectively 0.39, 0.41, 0.59 and 0.95. The apoptotic indexes of the second and the third experimental groups were significantly higher than that of the control group (P < 0.05). CONCLUSION: The interstitial irradiation with 32P glass microspheres can enhance the activity of apoptotic cells of solid tumor S180, and the effect is dose-dependent.

Animals↗
PubMed2001

[Apoptosis induced by interstitial irradiation with 32P glass microspheres combination with hyperthermia in mouse solid tumor S180].

OBJECTIVE: The aim of this study was to observe the changes of tumor cell apoptosis after interstitial irradiation combination with the hyperthermia treatment. METHODS: Twenty mice with solid tumor S180 were divided into four groups, including a control group which was given normal saline, and three experimental groups which were respectively applied with a hyperthermia treatment (bath water), interstitial irradiation with 32P glass microspheres, and the combined treatment of hyperthermia and interstitial irradiation. The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method was used to determine the final apoptotic cells. RESULTS: The mean values of apoptotic indexes of these four groups were respectively 0.39, 0.53, 0.59 and 0.91. The apoptotic indexes of these experimental groups were significantly higher than that of the control group (P < 0.05). The apoptotic index of the combined treatment group was significantly higher than those of the hyperthermia group and the interstitial irradiation group (P < 0.05). CONCLUSION: Both the interstitial irradiated with 32P glass microspheres and hyperthermia (bath water) can induce the apoptosis of mouse solid tumor S180. It seems that there is a synergistic induction of apoptosis between interstitial irradiation and hyperthermia.

Animals↗
PubMed2001

[Inhibitive effects of lip repair on maxillary growth in patients with complete unilateral cleft lip and palate].

OBJECTIVE: The aim of this study was to assess the isolated effects of lip repair on inhibition of maxillary growth in patients with complete unilateral cleft lip and palate. METHODS: The lateral cephalometric analysis were applied to 20 patients with unilateral cleft lip and palate who only had lip repaired in childhood, 32 patients with unilateral cleft lip and palate who had both lip and palate repaired in childhood, as well as 37 normal Chinese of the same age as controls. RESULTS: Both complete unilateral cleft lip and palate groups had almost the same significant degree of maxillary retrusion compared with the normal control group. CONCLUSION: Lip repair is one of important factors that could inhibit maxillary growth in patients with complete unilateral cleft lip and palate.

Adolescent↗
PubMed2000

Isolation and characterization of the notch ligand delta4.

Notch signaling plays a critical role in a variety of developmental programs. In vertebrates, the complexity of the process is underscored by the existence of multiple Notch receptors and multiple ligands, each of which displays a distinct expression profile. Furthermore, the ligands can be subdivided into two families, the Serrate/Jagged family and the Delta family. Here we present the isolation of a novel Notch ligand, Delta4. Expression analyses indicate that mouse Delta4 is highly expressed in the eye and lung during embryogenesis and in the heart, lung, liver, and kidney of the adult. Functionally, Delta4 is indistinguishable from Jagged1 in its abilities to inhibit myogenesis and to stimulate transcription through Notch1 and the DNA binding protein CSL.

3T3 Cells↗
PubMed2000

NADPH oxidase activation increases the sensitivity of intracellular Ca2+ stores to inositol 1,4,5-trisphosphate in human endothelial cells.

Many stimuli that activate the vascular NADPH oxidase generate reactive oxygen species and increase intracellular Ca(2+), but whether NADPH oxidase activation directly affects Ca(2+) signaling is unknown. NADPH stimulated the production of superoxide anion and H(2)O(2) in human aortic endothelial cells that was inhibited by the NADPH oxidase inhibitor diphenyleneiodonium and was significantly attenuated in cells transiently expressing a dominant negative allele of the small GTP-binding protein Rac1, which is required for oxidase activity. In permeabilized Mag-indo 1-loaded cells, NADPH and H(2)O(2) each decreased the threshold concentration of inositol 1,4,5-trisphosphate (InsP(3)) required to release intracellularly stored Ca(2+) and shifted the InsP(3)-Ca(2+) release dose-response curve to the left. Concentrations of H(2)O(2) as low as 3 microm increased the sensitivity of intracellular Ca(2+) stores to InsP(3) and decreased the InsP(3) EC(50) from 423.2 +/- 54.9 to 276.9 +/- 14. 4 nm. The effect of NADPH on InsP(3)-stimulated Ca(2+) release was blocked by catalase and by diphenyleneiodonium and was not observed in cells lacking functional Rac1 protein. Thus, NADPH oxidase-derived H(2)O(2) increases the sensitivity of intracellular Ca(2+) stores to InsP(3) in human endothelial cells. Since Ca(2+)-dependent signaling pathways are critical to normal endothelial function, this effect may be of great importance in endothelial signal transduction.

Calcium↗
PubMed2000

Role of megalin (gp330) in transcytosis of thyroglobulin by thyroid cells. A novel function in the control of thyroid hormone release.

When thyroglobulin (Tg) is endocytosed by thyrocytes and transported to lysosomes, thyroid hormones (T4 and T3) are released. However, some internalized Tg is transcytosed intact into the bloodstream, thereby avoiding proteolytic cleavage. Here we show that megalin (gp330), a Tg receptor on thyroid cells, plays a role in Tg transcytosis. Following incubation with exogenous rat Tg at 37 degrees C, Fisher rat thyroid (FRTL-5) cells, a differentiated thyroid cell line, released T3 into the medium. However, when cells were incubated with Tg plus either of two megalin competitors, T3 release was increased, suggesting that Tg internalized by megalin bypassed the lysosomal pathway, possibly with release of undegraded Tg from cells. To assess this possibility, we performed experiments in which FRTL-5 cells were incubated with either unlabeled or (125)I-labeled Tg at 37 degrees C to allow internalization, treated with heparin to remove cell surface-bound Tg, and further incubated at 37 degrees C to allow Tg release. Intact 330-kDa Tg was released into the medium, and the amount released was markedly reduced by megalin competitors. To investigate whether Tg release resulted from transcytosis, we studied FRTL-5 cells cultured as polarized layers with tight junctions on permeable filters in the upper chamber of dual chambered devices. Following the addition of Tg to the upper chamber and incubation at 37 degrees C, intact 330-kDa Tg was found in fluids collected from the lower chamber. The amount recovered was markedly reduced by megalin competitors, indicating that megalin mediates Tg transcytosis. We also studied Tg transcytosis in vivo, using a rat model of goiter induced by aminotriazole, in which increased release of thyrotropin induces massive colloid endocytosis. This was associated with increased megalin expression on thyrocytes and increased serum Tg levels, with reduced serum T3 levels, supporting the conclusion that megalin mediates Tg transcytosis. Tg transcytosis is a novel function of megalin, which usually transports ligands to lysosomes. Megalin-mediated transcytosis may regulate the extent of thyroid hormone release.

Amitrole↗
PubMed2000

Wittig reactions on photoprotoporphyrin IX: new synthetic models for the special pair of the photosynthetic reaction center.

A first example of spirochlorin-chlorin dimer with fixed distances and orientations as potential model for the "special pair" of the photosynthetic reaction center is discussed. For the preparation of such a novel structure, the Wittig reagent of the desired "spacer" 5 was reacted with photoprotoporphyrin IX dimethyl ester 3 to produce the intermediate dimer 6, which on intramolecular [4 + 2] Diels-Alder cycloaddition gave an unexpected spirochlorin-chlorin dimer 9. Dehydration of dimer 6 under acid-catalyzed conditions generated the corresponding spirochlorin-porphyrin dimer 16 in quantitative yield. The asymmetry in dimer 6 caused by the biphenyl-type anisotropic effect was confirmed by NMR and model studies. The formation of dihydrobenzoporphyrin 14 by reacting chlorin 3 with the phosphonium salt of p-methylbenzylbromide 10 and isolation of 8-phenanthrenevinylporphyrin 19 from chlorin 7 further confirmed our proposed mechanism for the formation of a spirochlorin-chlorin dimer 9. Following a similar approach, chlorin 3 on reacting with bis-phosphonium salt of 4, 4'-bischloromethylbiphenyl produced conjugated chlorin dimer 25. The spectroscopic data obtained from these dimers suggest that, in these compounds, the individual chromophores are not behaving as an individual molecule, but as a single macrocycle. To examine whether the pi-pi interaction exhibited by dimer 9 resembles the structural arrangement of bacteriochlorophylls in reaction center (RC), we investigated the geometrical parameters used to characterize the pi-pi interactions in tetrapyrrolic macrocycles. Starting from the crystallographic coordinates of 9, the molecular mechanics energy minimization was performed to obtain the model dimer structure. The geometrical parameters that measure the single pyrrole ring overlap were used to compare the model structure with the crystallographic coordinates of the special pair in photosynthetic reaction center. The results indicated that the ring A of spirochlorin and the ring C of chlorin in our model dimer 9 mimic the ring A-ring A interaction found in the crystallographic special pairs, which are strategically placed by the surrounding photosynthetic reaction center protein matrix.

Dimerization↗
PubMed2000

Photosensitizers related to purpurin-18-N-alkylimides: a comparative in vivo tumoricidal ability of ester versus amide functionalities.

For a comparative study, 3-(alkyloxyethyl)-3-devinylpurpurin-18-N-hexylimides with ester and amide functionalities were investigated for tumor selectivity and in vivo photosensitizing efficacy. Compared to amide analogues, the related photosensitizers with ester functionalities were found to be more effective. Among these compounds the 3-devinyl-(3-hexyloxyethyl)-purpurin-18-N-hexylimide as methyl ester 12 showed excellent tumor uptake (tumor versus muscle ratio: 8:1), and produced 100% tumor cure on day 30 at a dose of 1.0 micromol/kg. The mice were treated with light (135 J/cm2, 705 nm) at 24 h post injection of the drug.

Amides↗