Biomedical subjects

C Xiong

Publications and source records attributed to C Xiong.

At least 19 recordsLinked to original sources

PubMed2005

Alzheimer disease and cancer.

Cross-sectional studies raise the possibility of protective relationships between, or a common mechanism underlying, the development of dementia of the Alzheimer type (DAT) and cancer. Using a prospective longitudinal design, the authors found that the risk of developing cancer is less among participants with DAT vs nondemented participants (p < 0.001) and that the risk of developing DAT may be less for participants with a history of cancer (p = 0.060).

Age Factors↗

PubMed2004

Biological and conformational study of beta-substituted prolines in MT-II template: steric effects leading to human MC5 receptor selectivity.

To investigate the molecular basis for the interaction of the chi-constrained conformation of melanotropin peptide with the human melanocortin receptors, a series of beta-substituted proline analogs were synthesized and incorporated into the Ac-Nle-C[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 (MT-II) template at the His6 and D-Phe7 positions. It was found that the binding affinities generally diminished as the steric bulk of the p-substituents of the 3-phenylproline residues increased. From (2S, 3R)-3-phenyl-Pro6 to (2S, 3R)-3-(p-methoxyphenyl)-Pro6 analogs the binding affinity decreased 23-fold at the human melanocortin-3 receptor (hMC3R), 17-fold at the hMC4R, and eight-fold at the hMC5R, but selectivity for the hMC5R increased. In addition, the substitution of the D-Phe7 residue with a (2R, 3S)-3-phenyl-Pro resulted in greatly reduced binding affinity (10(3)-10(5)) at these melanocortin receptors. Macromodel's Large Scale Low Mode (LLMOD) with OPLS-AA force field simulations revealed that both MT-II and SHU-9119 share a similar backbone conformation and topography with the exception of the orientation of the side chains of D-Phe7/D-Nal (2')7 in chi space. Introduction of the dihedrally constrained phenylproline analogs into the His6 position (analogs 2-6) caused topographical changes that might be responsible for the lower binding affinities. Our findings indicate that hMC3 and hMC4 receptors are more sensitive to steric effects and conformational constraints than the hMC5 receptor. This is the first example for melanocortin receptor selectivity where the propensity of steric interactions in chi space of beta-modified Pro6 analogs of MT-II has been shown to play a critical role for binding as well as bioefficacy of melanotropins at hMC3 and hMC4 receptors, but not at the hMC5 receptor.

Adenylyl Cyclases↗

PubMed2001

Morphological properties of atmospheric aerosol aggregates.

Ultrafine particles (smaller than about 0.1 microm) are often emitted from combustion and other high-temperature processes in the form of fractal-like aggregates composed of solid nanoparticles. Results of a study of atmospheric aggregates are reported. Particles were collected on transmission electron microscope grids fitted on the last two stages of a single-jet eight-stage low-pressure impactor for periods of a few minutes. Photomicrographs of transmission electron microscope grids from the impactor stages were analyzed to obtain the fractal dimension (D(f)) and prefactor (A) for aggregates. D(f) increased from near 1 to above 2 as the number of primary particles making up the aggregates increased from 10 to 180. Total particle concentrations in size ranges roughly equivalent to the low-pressure impactor stages were measured with a mobility analyzer and condensation particle counter. In one set of measurements, the fraction of the particles present as aggregates was about 60% for particles with aerodynamic diameters between 50 and 75 nm and 34% for the range 75 to 120 nm. The total aggregate concentration in the 50- to 120-nm size range was about 400 ml(-1). The primary particles that make up atmospheric aggregates are more polydisperse than soot aggregates generated from a single laboratory source, an ethane/oxygen flame. Most measurements were made in the Los Angeles area, where the aggregates may represent a signature for diesel emissions. Rural aggregate concentrations in the size range 50 to 120 nm were less than 1% of the concentrations at urban sites. The data will permit better estimates of atmospheric aggregate residence times, transport, and deposition in the lung, optical extinction, and heterogeneous nucleation.

Journal Article↗

PubMed2001

Drug-polyionic block copolymer interactions for micelle formation: physicochemical characterisation.

While covalent attachment of small drug molecules to AB copolymers for the formation of polymeric micelles for drug delivery has been investigated, few studies have focused on non-covalent interactions. The aim of this study was therefore to explore the potential of non-covalent interactions between an AB copolymer, Poly(aspartic acid)-poly(ethylene glycol) (Pasp-PEG), with anionic pendant groups and diminazene aceturate, a small molecular weight cationic drug. Micelles were prepared by mixing solutions of Pasp-PEG and diminazene in 25 mM Tris-HCl buffer. At all Pasp-PEG concentrations studied, the micelles appeared to be water soluble with a unimodal size distribution and ranged in size from approximately 22 to 60 nm. The polyionic micelles also displayed similar and small absolute zeta potential values at various drug:monomer molar ratios which confirmed stabilisation by the PEG corona. The scattering intensity was maximal and remained unchanged, while particle size increased slightly at pH range from 3.4 to 7.2. At this pH range both the polymer and drug would be ionised and ionic interactions possible to drive micellar formation. An increase in size and scattering intensity with addition of NaCl to the micelles was attributed to dehydration of the PEG corona which may have led to aggregation of the micelles. The absence of micellar dissociation upon addition of salt was attributed to the dominance of hydrogen bonding between Pasp and diminazene aceturate, as assessed by isothermal titration microcalorimetry. Morphological evaluation of these constructs showed them to be discrete and fairly uniform in size and shape. This study was therefore successful in confirming the potential of non-covalent interactions using an AB copolymer to form polyionic micelles for drug delivery.

Drug Delivery Systems↗

PubMed2001

Effect and mechanism of electronic magnetic pulse on peripheral lymphocytes in dogs.

OBJECTIVE: To study the effects of electronic magnetic pulse (EMP) on peripheral lymphocytes in dogs and to explore the mechanisms of the biological effects of EMP. METHODS: T, TH and TS lymphocytes were estimated by acid phosphatase cytochemistry. Apoptotic lymphocytes and Bax and Bcl-2 proteins related to apoptosis were observed with in situ terminal labeling and immunocytochemistry. RESULTS: Peripheral T lymphocyte subpopulations decreased obviously after EMP irradiation with (2-12) x 10(4) V/m. Apoptotic percentages of lymphocytes increased with the elevation of EMP doses. Ten days after different intensity radiation, the Bax protein was found to be elevated in accord with the peak value of lymphocyte apoptosis. However, Bcl-2 protein decreased obviously. CONCLUSION: A definite field intensity EMP could induce injury to lymphocytes. Apoptosis induced by EMP is one of the main causes of peripheral lymphocyte death and leads to immunosuppression of the body. These results suggest that people should pay more attention to the injury caused by EMP, especially to the immunological functions of the body.

Animals↗

PubMed2000

[The effect of polylactide screws on fracture healing].

This experiment aimed at investigating the effect of a kind of home-bred poly-DL-lactide screws on fracture healing. An operation was performed so as to make bilateral lateral condylar fractures of the femur in 8 dogs. The left sides were fixed with 2 home-bred PDLLA(Mv = 43 x 10(4)) screws, and the contralateral sides were fixed with 2 metalic screws to be used as controls. The animals were sacrificed at 2, 4, 8, and 12 weeks after surgery. Optic microscopy and SEM photography were done. The results of optic microscopy showed that fibrous callus formed already in both groups by 2 weeks after surgery, and bilateral fractures united uneventfully by 12 weeks. Although the course of fracture healing in experimental group was slower than that in control group, the osteogenesis in experimental group appeared to be normal. The SEM examination demonstrated that collagenous fibers arranged regularly and calcified normally in both groups at 12 weeks. And many square and rhomboid granules produced from the degradation of PDLLA material were found in experimental group at 12 weeks. Therefore, it is suggested that this kind of home-bred PDLLA screws should be applicable to fractures where the tissues are rich in blood supply.

Animals↗

PubMed2000

[Liver sinusoidal endothelial cell damage during normothermic ischemia and reperfusion of rat].

OBJECTIVE: To observe the damage to liver sinusoidal endothelial cells during normothermic ischemia and reperfusion. METHODS: The afferent vessels of rat liver were clamped for 20, 40, 60 and 90 min respectively. The blood flow to the liver then was restored by removing the clamp. Ultrastructural changes in the sinusoidal endothelial cells in various periods were observed. RESULTS: After 20 or 40 min ischemia, fenestrations of the endothelial cells were enlarged and became mesh-like, but reperfusion for 120 min, led to recovery. After 60 or 90 min ischemia, the sieve plates and cytoplasmic processes of the endothelial cells were destroyed and the perikaryon tended to be desquamated. Reperfusion for 120 min led to no recovery, but resulted in the aggravation of injury and irreversible damage. The liver sinusoids were filled with numerous blood cells and blebs derived from hepatocytes, resulting in circulatory disturbance. CONCLUSIONS: Warm ischemia results in severe endothelial cell destruction. Endothelial cell damages may have unfavorable effects on the microcirculation of the reperfusion liver after prolonged ischemia.

Animals↗

PubMed1999

Investigation on process parameters involved in preparation of poly-DL-lactide-poly(ethylene glycol) microspheres containing Leptospira Interrogans antigens.

Block copolymer, poly-DL-lactide-poly(ethylene glycol) (PELA) with 11.5% of poly(ethylene glycol) (PEG) content was prepared by bulk ring-opening polymerization using stannous chloride as initiator. PELA microspheres with entrapped Leptospira Interrogans antigens, outer membrane protein (OMP) were elaborated by solvent extraction method based on the formation of multiple w/o/w emulsion, and the resulting microspheres were characterized with respect to particle size, OMP entrapment and morphology characteristics. The purpose of the present study is to perform the optimization of preparative parameters for OMP-loaded PELA micropsheres to control particle size and improve the OMP encapsulation efficiency. Of all the parameters investigated, the polymer concentration of organic phase and the external aqueous phase volume play major roles on particle size, while the organic phase volume, internal aqueous phase volume and the addition of surfactant into the internal aqueous phase display considerable effects on OMP loading efficiency. A small volume of internal aqueous phase and intermediate volumes of organic phase and external aqueous phase were favorable to achieve micropsheres with a size of 1-2 microns and high antigen encapsulation efficiency (70-80%). In vitro OMP release profiles from PELA microspheres consist of a small burst release followed by a gradual release phase. The OMP release rate shows some relations with the porous and water-swollen inner structure of the microspheres matrix. The presence of surfactant in microspheres accelerates OMP release, but the OMP entrapment within microspheres shows limited effects on the release profile.

Antigens, Bacterial↗

PubMed1999

[Internal fixation for zygomatic arch fracture with super-high molecular weight poly D, L-lactic acid mini-plates and screws: a study in dogs].

OBJECTIVE: To investigate the internal fixation effects of super high molecular weight (Mv = 6.0 x 10(5) kD) poly D, L-lactic acid(PDLLA) mini-plates and screws. METHODS: 10 dogs were utilized in this experiment with the self-contrast study method, comparing with the titanium mini-plates and screws. RESULTS: The mechanical properties of the PDLLA mini-plates and screws appeared to be sufficient to enable undisturbed healing of depressed zygomatic arch fracture. CONCLUSION: The good fixation effect of PDLLA mini-plates and screws was as same as that of the titanium mini-plates and screws without the need of secondary operation.

Animals↗

PubMed1999

[Tissue reaction and degradation of super-high molecular weight poly D, L-lactic acid mini-plates and screws: an animal experiment].

OBJECTIVE: To investigate the tissue reaction and degradation processes of the super-high molecular weight(Mv = 6.0 x 10(5) kD) poly D, L-lactic acid(PDLLA) mini-plates and screws through the internal fixation for zygomatic arch fracture. METHODS: It was carried out by the self-contrast study method and comparing with the titanium mini-plates and screws. RESULTS: There was no side-effects on bone healing. The reaction of soft and hard tissues to PDLLA mini-plates and screws was similar to that of the titanium mini-plates and screws. No complication had been seen with the use of PDLLA mini-plates and screws, including infection, foreign body reaction and underlying osteolysis. The PDLLA devices had no changes in shape after 3 months, and then became the grains in different sizes after 6 months, and were completely resorbed within 12 months in vivo. CONCLUSION: The super-high molecular weight PDLLA mini-plates and screws has good biocompatibility and proper degradation time. It is safe and effective to use the mini-plates and screws made of the super-high molecular weight PDLLA for internal fixation of bone.

Animals↗

PubMed1999

Apoptosis of hemopoietic cells in irradiated mouse bone marrow.

Apoptosis of hemopoietic cells in bone marrow following radiation has been rarely reported, let alone studied quantitatively and pathologically. LACA mice were irradiated with 2.5, 4.0, 5.5, and 7.0 Gy gamma-rays, and the bone marrow was examined at 6 hours, 1 day, and 3 days after radiation. Semi-thin and thin sections were examined by light and electron microscopy. The number and area density of the apoptotic cells were assessed by means of a Cambridge Quantimet 970 Image Analyzer. We found that apoptosis occurred in only a few hemopoietic cells in the control mouse bone marrow, whereas 6 hours after radiation there were many apoptotic hemopoietic cells in each sample of irradiated bone marrow. Compared with controls, both the number and area density of the apoptotic cells markedly increased in the bone marrow of animals in every radiation dose group, and the difference was statistically significant (p < 0.01). Furthermore, the number and area density increased as the radiation dose increased. Our findings suggest that apoptosis is the main mode of radiation-induced hemopoietic cell death.

Animals↗

PubMed1998

Optimal utilization of cryopreserved human semen for assisted reproduction: recovery and maintenance of sperm motility and viability.

PURPOSE: Our purpose was to evaluate sperm motility and viability and the maintenance of these parameters in already cryopreserved semen samples following repeated freezing/thawing cycles. METHODS: Human spermatozoa were subjected to five cycles of cryopreservation/thawing. Recovery of sperm motility and viability and the proportion of viable nonmotile sperm were determined up to 6 hr after thaw. RESULTS: Sperm motilities (prefreeze motility, 70.1%; n = 9 samples) after each of five freeze/thaw cycles were 24.4, 8.0, 3.5, 1.5 and 1.8%. The recovery of sperm viability was higher than that of motility after each cycle: 39.1, 25.3, 22.6, 17.8, and 16.5%. Recoveries of motility and viability were improved if the thawed samples were left in the original cryopreservation medium prior to refreezing vs. if a washing/ resuspension step was included. The recovery of sperm motility in the first thawing cycle was indicative of the expected motile sperm recovery in the second thawing cycle. CONCLUSIONS: Cryopreserved semen that is intended to be reused in future assisted reproduction treatments should be thawed only once and aliquoted in the original freezing medium before refreezing. The recovery of sperm motility and viability in the second thawing cycle, thus the applicability of the sample in conventional in vitro fertilization or intracytoplasmic sperm injection may be anticipated in > 90% of the samples. In view of intracytoplasmic sperm injection it is important that sperm viability is maintained better than motility; after the first, second, and third thawing cycles the ratios of motile:nonmotile viable sperm were 1:1, 1:4, and 1:7, respectively.

Cryopreservation↗

PubMed1998

[Effect of prolonged inhalation of nitric oxide on chronically hypoxic rats].

OBJECTIVE: To explore the effect of prolonged nitric oxide (NO) inhalation on chronically hypoxic rats. METHODS: Male Wistar rats were randomly divided into 3 groups: 1) room-air control (C); 2) hypoxia (H); 3) hypoxia with the inhalation of 20 ppm NO(2NH). RV/LV + S, mPAP and the histopathology of the lung were examined. Plasma levels of ET-1 and cGMP were detected by radioimmunoassay. RESULTS: 1. Hypoxia caused marked elevation in mPAP and RV/LV + s (both P < 0.001 vs Group C). NO significantly reduced mPAP and RV/LV + S; 2. Hypoxia raised the percentage of intra-acinar muscular artery (MA) and lowered that of nonmuscular artery (NAM). MA decreased from 35.2% to 16.8% in Group 2NH; NMA increased from 43.6% to 64.8% in Group 2NH, 3. The plasma level of ET-1 increased and that of cGMP droped significantly in Group H(both P < 0.001 vs Group C). NO resulted in a marked reduction in the plasma ET-1 and an increase in plasma cGMP; 4. Inhalation of NO had no effect on methemoglobin and lung index in hypoxic rats. CONCLUSIONS: Prolonged inhalation of 20 ppm NO can attenuate hypoxic pulmonary hypertension and inhibit the hypertrophy of the pulmonary vascular smooth muscle and the right ventricle NO, when inhalated at a concentration of 20 ppm for a long duration, will cause no toxicity in chronically hypoxic rats.

Administration, Inhalation↗

PubMed1998

[The effect of nitric oxide administration on pateints with pulmonary hypertension: a dose-response study].

OBJECTIVE: To explore the dose-response relationship in patients with pulmonary hypertension after inhalation of nitric oxide (NO). METHODS: The effect of various concentrations (20, 40, 60 and 80 ppm) of NO on hemodynamics and cardiac function in 16 patients with pulmonary hypertension was studied with right heart catheterization. RESULTS: Pulmonary artery pressure and pulmonary vascular resistance reduced significantly after inhalation of various concentrations (20, 40, 60 and 80 ppm) of NO. The vascular response to NO was not concentration-dependant with a maximal effect obtained at 20 ppm. At inhalation of low dose of NO (20 ppm), the mean pulmonary artery pressure and pulmonary vascular resistance dropped by 26.5% and 40.3% (P < 0.0001), respectively. With the increase of inhaled NO concentration, pulmonary artery pressure and pulmonary vascular resistance did not decline. CONCLUSION: The best concentration of inhaled NO was not more than 20 ppm in the patients of this study.

Administration, Inhalation↗

PubMed1998

The changes and significance of c-kit expression in the irradiated bone marrow of mice.

There have been only a few studies on the expression of c-kit in bone marrow after radiation and radiation-induced apoptosis of hematopoietic cells. LACA mice were examined after irradiation with a dose of 60Co gamma-rays. Using a light microscope, electron microscope, and immunohistochemistry, we studied radiation-induced apoptosis of hematopoietic cells and the expression of c-kit. We found that 5.5 Gy total body irradiation was a sublethal dose for LACA mice, induced suppression of leukocytes in blood, and of nucleated cells in bone marrow. Apoptosis of the hematopoietic cells occurred within 1 day after irradiation. The expression of c-kit was related to the recovery of hematopoiesis and played an important role in early hematopoiesis.

Animals↗

PubMed1998

Interleukin-3 gene expression in irradiated mouse bone marrow.

The expression of endogenous interleukin-3 (IL-3) gene in mouse bone marrow after whole body irradiation was assessed by immunocytochemistry, in situ hybridization (ISH), and in situ reverse transcription PCR (IS RT-PCR). The results showed obvious injury to the bone marrow followed by recovery 4 weeks after radiation. IL-3 protein was increased in the cytoplasm of recovering hematopoietic cells, especially at 21 days after radiation, while the mRNA was negative, except at 15 days when the mRNA was weakly positive by ISH. IS RT-PCR showed that IL-3 mRNA was strongly positive in the cytoplasm of recovering hematopoietic cells, especially at 10 to 15 days after radiation. We postulate that endogenous IL-3 gene may accelerate hematopoietic recovery in irradiated bone marrow and that IS RT-PCR may objectively report the regulation of IL-3 gene expression.

Animals↗

PubMed1997

Studies on the relationship between urokinase plasminogen activator (uPA) and human sperm motility.

To clarify the role of urokinase plasminogen activator (uPA) in the mechanisms of regulating sperm motility and the ability of fertilizing, we investigated the quantities and activities of uPA in human seminal plasma and on the membrane of spermatozoa. Semens were harvested from 22 infertile patients with asthenospermia and 20 healthy fertile men according to WHO standards. To quantify the membrane-bound uPA in the samples, polyclonal antibodies against human urokinase were employed by means of a sandwich ELISA. The uPA activities in seminal plasma and on the surface of spermatozoa were determined using A-garose-Fibrine-Plate method and the experiment of immunological identification with polyclonal antibodies against urokinase. In lysates of spermatozoa, significantly lower levels of uPA (23.1 +/- 7.35 mu/10(6) cells) and uPA activity (5.13 +/- 3.85 mu/10(6) cells) were found in patient group as compared to healthy fertile men exhibiting normospermia (29.89 +/- 9.40 mu/10(6) cells and 10.17 +/- 6.18 mu/10(6) cells). In seminal plasma, uPA activity in patient group (2134 +/- 1581.3 IU/L) was also found significantly lower than that of normal group (3365 +/- 1859.5 IU/L). Positive correlations were observed between sperm motility and uPA quantities (r = 0.48, P < 0.005), as well as with uPA activities (r = 0.45, P < 0.005). Thus, it is inferred that membrane associated uPA on human spermatozoa may be related directly to sperm motility and fertility.

Adult↗

PubMed1997

[A simple nitric oxide exposure system for small animals].

A nitric oxide exposing system was designed for experimental research, which consist of equipments such as plexiglass chamber, blower, flowmeter, NO/N2 cylinder, pure O2 cylinder, NOx analyzer, and O2/CO2 monitor. The efficacy of the whole system has been verified through our practice as shown by the following results: measured NO inside the chamber were close to designed NO concentration, measured O2 concentrations in the chamber were similar to that of the atmosphere, and the highest nitrogen dioxide (NO2) and carbon dioxide (CO2) concentrations were lower than 3 ppm and 0.3% respectively. The experimental facility is simple in construction, easy to be operated and convenient for research on effects and toxicity of long-term inhaled nitric oxide in small animals.

Administration, Inhalation↗