Biomedical subjects

Yu Qin

Publications and source records attributed to Yu Qin.

25 records · Page 2Linked to original sources

PubMed2003

Ion-pairing ability, chemical stability, and selectivity behavior of halogenated dodecacarborane cation exchangers in neutral carrier-based ion-selective electrodes.

Recently, it has been discovered that carba-closo-dodecaborates can be used as cation exchangers in neutral carrier-based ion-selective chemical sensors. Because of their inherent chemical stability and versatile functionalization chemistries, they offer many advantages that may potentially be exploited for ion analyses that require nontraditional sample conditions, including strongly acidic media. In this work, trimethylammonium salts of undecachlorinated (UCC), undecabrominated (UBC), hexabrominated (HBC), and undecaiodinated (UIC) carborane anions were prepared and evaluated for their potential use in solvent polymeric membrane-based sensors. Computational methods including Natural population analysis and electrostatic mapping were used to predict the ion-exchanging ability of each lipophilic anion. In addition, the sandwich membrane technique was used to evaluate the ion-pairing ability of each carborane anion in situ (i.e., within bis(2-ethylhexyl) sebacate (DOS)- and 2-nitrophenyl octyl ether (o-NPOE)-plasticized ISE membranes). The results of the computational and potentiometric studies found that binding affinity of the anions followed the generalized trend HBC > UCC > UBC > UIC. PVC-DOS bulk optode thin films containing the chromoionophore ETH 5315 and a respective anion were used to determine the chemical stability/lipophilicity of the carboranes and tetrakis[3,5-bis(trifluoromethyl)phenyl] borate (TFPB) in acidic media (0.2 M HOAc) under flowing conditions. The studies found that in terms of stability/lipophilicity UIC > UBC > TFPB approximately UCC >> HBC. Electrodes containing a Pb(2+)-selective ionophore, tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide)(lead IV), were used to evaluate the functionality of each cation exchanger. An evaluation of response characteristics such as slope and selectivity found that UIC and UBC were quite comparable to the behavior of TFPB. Interestingly, both UIC and UBC showed a marked selectivity improvement over cadmium, with log K(pot)(pb),(Cd) values of -7.19 and -7.29, respectively, with TFPB giving a value of -5.89. Demonstrating excellent stability and suitable electrostatic properties, the carboranes, UIC in particular, are a very promising alternative to the tetraphenylborates and should find widespread application in the field of chemical sensors.

Boranes↗

PubMed2003

Mechanistic insights into the development of optical chloride sensors based on the [9]mercuracarborand-3 ionophore.

Fluorescent sensing microspheres based on perhaps the most selective and practically useful chloride ionophore known, the recently reported [9]mercuracarborand-3 (MC-3), have been prepared and optimized for physiological measurements. In initial work, this ionophore was shown to yield functional optical sensing films in combination with an electrically neutral chromoionophore, ETH 5418. Unfortunately, however, these optodes suffered from unacceptably high levels of sodium interference under physiological conditions. To better understand the sensing mechanism, optical and potentiometric binding experiments were used to characterize the stoichiometry and the complex formation constants for this ionophore. It was found that the preferred stoichiometry is 1:2, rather than 1:1 as assumed earlier. The 1:2 complex is extremely stable (logbeta2 = 13.4), but a relatively strong 1:1 complex also exists (log K1 = 9.9). These characteristics were used to fabricate chloride optodes that make use of the stepwise ion-ionophore decomplexation equilibrium, by adding a calculated amount of lipophilic anion exchanger to the polymer film. Such optodes showed dramatically reduced sodium interference while maintaining the excellent selectivity of the traditional formulation. The optimized composition also shifted the measuring range to physiological conditions, making them useful for the assessment of chloride in undiluted and 10-fold-diluted blood at pH 7.4. After necessary alterations of the particle preparation procedure and sensor formulation, the new insights were used to fabricate mass-produced optical sensing microspheres with characteristics essentially identical to those of the optode sensing films.

Chlorides↗

PubMed2003

[The regulatory effect of human bone morphogenetic protein 7 gene transfer on the proliferation and differentiation of rabbit bone marrow mesenchymal stem cells].

OBJECTIVE: To detect the proliferation and differentiation of rabbit bone marrow mesenchymal stem cells (BMSc) transferred by retroviral vector carrying human bone morphogenetic protein 7 (hBMP-7) gene. METHODS: hBMP-7-expressing replication-deficient retroviral vector(PT-PLNCX2-hBMP7) was reconstructed using clone technique and recombinant DNA technique. BMSc were infected with the virus granules. The protein of BMP-7 gene in transferred cells were determined by immunohistochemistry. The proliferativity of the transferred cell were assayed by methabenzthiazuron (MTT) method and flow cytometer. Alkaline phosphatase (ALP) were also detected using enzyme kinetics. RESULTS: Cells transferred by PT-PLNCX2-hBMP7 expressed abundant hBMP7 protein in the cytoplasm. Positive findings were not found in those cells that were not transferred. After infected with virus there were not significant difference of cell proliferation and cell cycle between the cells transferred by hBMP-7 or not (P > 0.05). ALP activity in transferred cells were increased significantly (P < 0.01). CONCLUSIONS: hBMP-7 can be transferred and stably expressed in the cultured rabbit bone marrow stem cells. Proliferation and cell cycle of the transferred cell were not affected. hBMP7 gene transfer can be used to induce differentiation of BMSc into osteoblast-like cells.

Alkaline Phosphatase↗

PubMed2003

[Effect of bone morphogenetic protein microspheres on biological behavior of rabbit bone marrow stem cells].

OBJECTIVE: To evaluate the effect of bone morphogenetic protein (BMP) on the biological behavior of bone marrow stem cells (BMSCs) of rabbits. METHODS: BMP was either enwrapped or not in the microspheres made of chitosan and sodium alginate, and the biocompatibilities of the composites were examined by means of cell culture. The BMSCs were cultured with the two kinds of microspheres respectively, and the cell extension rate, proliferation, alkaline phosphatase activity and Coomassie blue staining of the cells were assayed. RESULTS: Inhibition of BMSC proliferation did not occur in response to in vitro culture with the microspheres, but alkaline phosphatase activity and D(lambda) values of Coomassie blue staining increased significantly in the cells cultured with BMP microspheres. CONCLUSION: BMP can increase the osteogenic capacity of BMSCs in vitro with the microspheres made of chitosan and sodium alginate as the carrier.

Animals↗

PubMed2002

Evaluation of the separate equilibrium processes that dictate the upper detection limit of neutral ionophore-based potentiometric sensors.

The upper detection limit of polar ionophore-based ion-selective electrode membranes is predicted by utilizing the coextraction constant of dissociated electrolyte, the stability constant of the ionophore, and the membrane composition. The coextraction constant of dissociated electrolytes into the polar poly(vinyl chloride) membrane plasticized with o-nitrophenyl octyl ether (PVC-NPOE) is here measured by a novel approach. The sandwich membrane technique is utilized, with one membrane segment containing a lipophilic cation exchanger and the other containing an anion exchanger. This yields information about the coextraction constant and the free ion concentrations of the electrolyte in the two segments. Predictions correlate quantitatively with the upper detection limit observed for ion-selective electrodes based on the ionophores valinomycin, tert-butylcalix[4]arene tetraethyl ester, and calcimycin. The difficulties of the prediction of the upper detection limit for nonpolar poly(vinyl chloride) membranes plasticized with bis(2-ethylhexyl sebacate) (PVC-DOS) due to ion association are discussed in detail. A thermodynamic cycle experiment with a series of sandwich membranes shows that the principal processes governing the upper detection limit of PVC-DOS membranes are identical to those for the PVC-NPOE membranes. However, the stability of the ion pairs between the ionophore-metal ion complexes and the extracted anion are different from that of ion pairs formed between the same anion and the lipophilic anion exchanger. This makes it difficult to quantitatively predict the upper detection limit on the basis of simple apparent coextraction and complexation data alone. The approach reported herein is useful not only for mechanistic purposes but also to shed light onto the many cases where coextraction effects need to be understood but are not directly experimentally accessible.

Algorithms↗

PubMed2002

[Bacterium culture and flora analysis of gunshot wound on limbs of dogs in hot and humid environment].

OBJECTIVE: To investigate the time of bacterial invasion into the blood and conduct flora analysis of the blood and secretions in the gunshot wound in the limbs of dogs in hot and humid environment. METHODS: Gun-shot wound was induced in 8 dogs who were subsequently assigned at random into hot and humid environment (HHE) group and normal environment (NE) group for observation. At the time points of 0, 4, 6, 8, 12, 24 h after injury, body temperature was measured and bacterial culture and flora analysis performed. RESULTS: Body temperature elevation occurred earlier and lasted for longer time in HEE group than in NE group. Bacterial invasion into the blood occurred at 12 h after the injury in NE group, but at 8 h in HHE group. In the wound tracts of the dogs, surface bacteria were found in both groups. Surface bacteria were also found in the blood of dogs in both groups, but in HHE group, even intestinal flora were identified. CONCLUSION: Body temperature elevation and bacterial invasion into the blood occurred at an earlier time in hot and humid environment where migration of intestinal bacteria into the blood easily takes place, indicating the early application of broad-spectrum antibiotics under such environmental conditions.

Animals↗

PubMed2002

[Apoptosis induced by diacetyldianhydrogalactitol and its mechanism in HL-60 leukemia cells].

AIM: To investigate the apoptosis induced by diacetyldianhydrogalactitol (DADAG) and its mechanism in human HL-60 leukemia cells. METHODS: Inhibition of proliferation was measured by MTT assay. DADAG-induced apoptosis in HL-60 cells was observed by electron microscopy, flow cytometry and DNA fragmentation assay. The levels of Bcl-2 family proteins were detected by Western blotting. Caspase-3 activity was determined by ApoAlert CPP32 colorimetric assay kit. RESULTS: DADAG exhibited potent antiproliferative activity and induced apoptosis in HL-60 cells. After treatment with DADAG 8 micrograms.mL-1 for various times, the Bcl-XL protein level decreased in a time-dependent manner, while the Bad protein level was upregulated. The caspase-3 activity increased markedly after treatment with DADAG for 24 h. The apoptotic signals were suppressed by z-VAD.fmk (a general inhibitor of caspases), whereas z-DEVD.fmk, a selective inhibitor of caspase-3, only induced partial reversion of the apoptotic effects. CONCLUSION: DADAG-induced apoptosis in HL-60 cells required caspase-3 activation and caspase-3 activation was related with Bcl-2 family members.

Antineoplastic Agents↗