PubMed Health⌕ Search

Biomedical subjects

Jun Ding

Publications and source records attributed to Jun Ding.

33 records · Page 2Linked to original sources
PubMed2004

Adsorption thermodynamic, kinetic and desorption studies of Pb2+ on carbon nanotubes.

Adsorption thermodynamics of Pb2+ on carbon nanotubes has been studied at various temperatures of 280, 298 and 321 K and the thermodynamic parameters, such as equilibrium constant (K0), standard free energy changes (DeltaG0), standard enthalpy change (DeltaH0) and standard entropy change (DeltaS0), have been obtained. A pseudo-second-order rate model has been employed to describe the kinetic adsorption processes. Desorption studies reveal that Pb2+ can be easily removed from carbon nanotubes by altering the pH values of the solution using both HCl and HNO3, indicating that carbon nanotubes are a promising absorbent for wastewater treatment.

Adsorption↗
PubMed2004

Toosendanin increases free-Ca(2+) concentration in NG108-15 cells via L-type Ca(2+) channels.

AIM: To examine if toosendanin (TSN) affects intracellular free-Ca(2+) concentration ([Ca(2+)](i)) in neuroblastoma pluglioma hybrid cells (NG108-15 cells). METHODS: The [Ca(2+)](i) was determined by laser-scanning confocal microscopic imaging technique in which Fluo-3 was used as Ca(2+) indicator. RESULTS: TSN induced an increase in resting [Ca(2+)](i) and in high K(+)-evoked Ca(2+) transient in differentiated NG108-15 cells. The TSN-induced increase in [Ca(2+)](i) was dose-dependent and disappeared in CdCl(2-), nifedipine-containing or Ca(2+)-free solution, and appeared after washing out the Ca(2+) channel blockers or adding Ca(2+). CONCLUSION: TSN increased [Ca(2+)](i) in differentiated NG108-15 cells. The [Ca(2+)](i) enhancement was due to the influx of extracellular Ca(2+) and related to L-type Ca(2+) channels.

Animals↗
PubMed2004

Removal of heavy metals from aqueous solution by carbon nanotubes: adsorption equilibrium and kinetics.

Carbon nanotubes prepared by catalytic chemical vapor deposition of hydrocarbon at 650 degrees C show good adsorption capability of Pb2+, Cu2+ and Cd2+ ions from aqueous solution after oxidized with concentrated nitric acid at 140 degrees C for 1 h. The specific surface area and particle size distribution of the as-grown and oxidized CNTs were studied by BET method and laser particle analyzer. Three kinetic models, that is, first-, pseudo second- and second-order, were used to investigate the adsorption data and the pseudo second-order model can represent the experimental data better than two others. The equilibriumdata fitted well with the Langmuir model and showed the following adsorption order: Pb2+ > Cu2+ > Cd2+.

Adsorption↗
PubMed2003

Effect of potentiation on the catchlike property of human skeletal muscles.

The catchlike property of skeletal muscle is the force enhancement produced when a brief, high-frequency burst of pulses (two to four pulses) is added to a subtetanic train of pulses. Stimulation trains that take advantage of the catchlike property have been shown to produce greater forces than trains commonly used during clinical application of functional electrical stimulation (FES). We recently showed, however, that there was no force enhancement observed with the catchlike property when muscles were nonfatigued and highly potentiated. Thus, understanding the relationship between the force augmentations produced by the catchlike property and potentiation may provide insight into the physiological conditions that best take advantage of the catchlike property. The goal of this study was to explore quantitatively the effect of potentiation on the catchlike property of the muscle. Isometric data were collected from human quadriceps femoris muscles. A negative linear relationship between the force augmentation produced by the catchlike property and the amount of potentiation was observed. These data showed that for nonfatigued muscles, the catchlike property would be most beneficial at the onset of activation, when muscles are the least potentiated. These results should help to guide clinicians to design stimulation protocols that optimize performance during FES.

Adult↗
PubMed2003

Mathematical models for fatigue minimization during functional electrical stimulation.

We previously reported the development of a force- and fatigue-model system that predicted accurately forces during repetitive fatiguing activation of human skeletal muscles using brief duration (six-pulse) stimulation trains. The model system was tested in the present study using force responses produced by longer duration stimulation trains, containing up to 50 pulses. Our results showed that our model successfully predicted the peak forces produced when the muscle was repetitively activated with stimulation trains of frequencies ranging from 20 to 40 Hz, train durations ranging from 0.5 to 1 s, and varied pulse patterns. The predicted peak forces throughout each protocol matched the experimental peak forces with r2 values above 0.9 and predicted successfully the forces at the end of each protocol with <15% error for all protocols tested. The success of our model system further supports its potential use for the design of optimal stimulation patterns for individual users during functional electrical stimulation.

Electric Stimulation↗
PubMed2003

Effects of myasthenia gravis patients' sera with different autoantibodies on slow K+ current at mouse motor nerve terminals.

The antibodies against pre-synaptic membrane receptor (PsmR) and acetylcholine receptor (AChR) in serum samples of myasthenia gravis (MG) patients and healthy donors were tested by enzyme-linked immunosorbent assays (ELISA). The serum samples of eight MG patients with different autoantibodies and those of six healthy donors without these two kinds of autoantibodies were collected to investigate their effects on the peri-neurially recorded membrane currents at mouse motor nerve terminals. After inhibition of both fast and Ca(2+)-dependent K+ currents by tetra-ethylammonium (TEA), a positive wave was revealed, which was a balance of the slow K+(Ik,s) and Ca2+ currents (ICa). Application of anti-PsmR antibody negative MG sera and healthy donor sera, whether anti-AChR antibody positive or negative, did not affect the positive wave. However, the positive wave shifted to prolonged Ca(2+)-plateau when adding two of four anti-PsmR antibody positive serum samples from MG patients, indicating an inhibition of Ik,s by anti-PsmR antibody positive sera. Meanwhile, all serum samples derived from either patients or healthy donors did not affect INa.

Adolescent↗
PubMed2003

Experimental study on the feasibility and safety of radiofrequency ablation for secondary splenomagely and hypersplenism.

AIM: To assess the feasibility and safety of radiofrequency ablation (RFA) in treatment of secondary splenomagely and hypersplenism. METHODS: Sixteen healthy mongrel dogs were randomly divided into two groups, group I (n=4) and group II (n=12). Congestive splenomegaly was induced by ligation of splenic vein and its collateral branches in both groups. At the end of 3rd week postoperation, RFA in spleen was performed in group II via laparotomy, complications of RFA were observed, CT scan was performed and the spleens were obtained. The radiofrequency (RF) thermal lesions and histopathology of spleen were examined regularly. RESULTS: No complication or death was observed in both groups; CT revealed that the splenomegaly lasted over 2 months after ligation of splenic vein; the segmental RF lesions included hyperintense zone of coagulative necrosis and more extensive peripheral hypointense infarcted zone, the latter was called "bystander effect". The infarcted zone would be absorbed and subsequently disappeared in 4-6 weeks after RFA accompanied with shrinkage of the remnant spleen. The fundamental histopathological changes of splenic lesions caused by RF thermal energy included local coagulative necrosis, peripheral thrombotic infarction zone, subsequent tissue absorption and fibrosis in the zone of thrombotic infarction, the occlusion of vessels in remnant viable spleen, deposition of extensive fibrous protein, and disappearance of congestive splenic sinusoid - "splenic carnification". Those pathologic changes were underline of shrinkage of spleen. CONCLUSION: It is feasible and safe to perform RFA in spleen to treat experimental splenomegaly and hypersplenism. The RFA could be safely performed clinically via laparotomy or laparoscopic procedure while spleen was strictly separated from surrounding organs.

Animals↗
PubMed2003

[The feasibility and safety of radiofrequency ablation for secondary splenomegaly and hypersplenism in dogs].

OBJECTIVE: To assess the feasibility and safety of radiofrequency ablation (RFA) in spleen to treat secondary splenomegaly and hypersplenism in dogs. METHODS: Fourteen healthy mongrel dogs were randomly divided into two groups: group A (n = 4) and group B (n = 10) Both groups underwent ligation of the splenic vein and its collateral branches to induce congestive splenomegaly. At the end of the 3rd week, radiofrequency thermal ablation of the spleen was performed in the group B via laparotomy. After splenic RFA, the procedure-related complications were observed, CT scan was performed and the spleens were obtained according to schedule. The radiofrequency (RF) thermal lesions and its histo- pathological changes of the spleen were examined regularly. RESULTS: There were no morbidity and mortality in the experimental dogs. CT findings revealed that splenomegaly could sustained over 2 months after ligation of the splenic vein. The segmental RF lesions included hyperintense zone of coagulative necrosis and more extensively peripheral hypo-intense infarcted zone. The latter was called as "bystander effect". The infarcted zone would be absorbed and subsequently disappeared between 4 and 6 weeks after RFA, and the size of the remnant spleen shrunk, but the lesion of coagulative necrosis hardly altered. The fundamental histopathological changes of splenic lesions caused by RF thermal energy included local coagulative necrosis and the peripheral thrombotic infarction zone. Subsequently, tissue absorption and fibrosis occurred in the zone of thrombotic infarction. Simultaneously occluded vessels, fibrin deposition, and disappearance of normal splenic sinuses resulted in the condensed structure of the viable remnant spleen, which were the pathological basis responsible for the shrunk spleen. CONCLUSIONS: It is feasible and safe to perform RFA in the spleen to treat experimental splenomegaly and hypersplenism. The RFA technique could be safely performed clinically via laparotomy or laparoscopic procedure to strictly isolate the spleen from the surrounding organs.

Animals↗
PubMed2002

Electrical stimulation factors in potentiation of human quadriceps femoris.

Potentiation is the enhancement of force seen after repetitive activation of skeletal muscle. The frequency and duration of stimulation, total number of pulses delivered to the muscle, and the peak forces or force-time integrals produced by the stimulation all have been suggested to affect the degree of potentiation. The purpose of this study was to determine the effect of the electrical stimulation characteristics on the development of post-activation potentiation. Eleven subjects were tested with five potentiating trains, including 12-pulse 100-HZ, 31-HZ, 14-HZ, and 5-HZ, and 6-pulse 14-HZ trains. The potentiating trains differed in stimulation frequency, train duration, and total number of pulses. They also produced different peak forces and force time integrals from the activated muscles. Our results showed that the 12-pulse 5-HZ train produced about 50% less potentiation than the other four potentiating trains. At stimulation frequencies of 14 HZ or higher, the total number of pulses delivered to the muscle was the primary factor in potentiation development. Furthermore, peak force and force-time integral had no effects on the rate or amount of potentiation. These results should help clinicians and researchers to design protocols that control for the effects of muscle potentiation.

Adult↗
PubMed2002

A mathematical model that predicts the force-frequency relationship of human skeletal muscle.

In previous work we developed and validated a mathematical model that predicted force output from skeletal muscles subjected to six-pulse stimulation trains under isometric condition. The current study investigated the model's ability to predict force responses to longer stimulation trains under both nonfatigued and fatigued conditions. Using the six-pulse train model to predict the force produced by longer stimulation trains showed that the model was successful, but a modified parameter identification scheme was required. For most of the trains tested the model accounted for 95% of the variance in the experimental forces produced by stimulation trains, with mean frequencies from 12.5 to 100 HZ, train durations from 485 to 1000 ms, and number of pulses from 14 to 50 for both nonfatigued and fatigued muscles. The success of our mathematical model in predicting forces produced by stimulations with a wide range of frequencies, durations, and number of pulses implies great potential of the model for the identification of optimal activation patterns that should be used during functional electrical stimulation.

Actins↗
PubMed2002

Modeling the length dependence of isometric force in human quadriceps muscles.

Functional electrical stimulation is used to restore movement and function of paralyzed muscles by activating skeletal muscle artificially. An accurate and predictive mathematical model can facilitate the design of stimulation patterns that produce the desired force. The present study is a first step in developing a mathematical model for non-isometric muscle contractions. The goals of this study were to: (1) identify how our isometric force model's parameters vary with changes in knee joint angle, (2) identify the best knee flexion angle to parameterize this model, and (3) validate the model by comparing experimental data to predictions in response to a wide range of stimulation frequencies and muscle lengths. Results showed that by parabolically varying one of the free parameters with knee joint angle and fixing the other parameters at the values identified at 40 degrees of knee flexion, the model could predict the force responses to a wide range of stimulation frequencies and patterns at different muscle lengths. This work showed that the current isometric force model is capable of predicting the changes in skeletal muscle force at different muscle lengths.

Biomechanical Phenomena↗
PubMed2002

A predictive fatigue model--I: Predicting the effect of stimulation frequency and pattern on fatigue.

Previously we developed a mathematical force- and fatigue-model system that could predict fatigue produced by a wide range of frequencies and pulse patterns. However, the models tended to overestimate the forces produced by higher frequency trains. This paper presents modifications to our previously developed force- and fatigue-model system to improve the accuracy in predicting forces during repetitive activation of human skeletal muscle. By comparing the predictions produced by the modified force and fatigue models to those by our previous models, the modification appears to be successful. The current force- and fatigue-model system accounts for about 93% variance in experimental data produced by fatigue protocols consisting of trains with a wide range of frequencies and pulse patterns. In addition, the present models successfully predict the effect of stimulation frequency and pulse pattern on muscle fatigue. The success of our current force- and fatigue-model system suggests its potential use in helping to identify the optimal activation pattern to use during the clinical application of functional electrical stimulation.

Algorithms↗
PubMed2002

A predictive fatigue model--II: Predicting the effect of resting times on fatigue.

We have recently developed a force- and fatigue-model system that accurately predicted the effect of stimulation frequency on muscle fatigue. The data used to test the model were produced by stimulation trains with resting times of 500 ms. Because the resting times between stimulation trains affect muscle fatigue, this study tested the model's ability to predict the effect of resting times on fatigue. In addition, because this study included different subjects than those used to develop the model, the validity of the model could be tested. Data were collected from human quadriceps femoris muscles using fatigue protocols that included resting times of 500, 750, or 1000 ms. Our results showed that the model predicted fatigue as being a decreasing function of resting time, which was consistent with experimental data. Reliability tests between the experimental data and predictions showed interclass correlation coefficients of 0.97, 0.95, and 0.81 for the initial, final, and percentage decline in peak forces, respectively, suggesting strong agreement between the experimental data and the predictions by the model. The success of our current force- and fatigue-model system helps to validate the model and suggests its potential use in identifying the optimal activation pattern during clinical application of functional electrical stimulation.

Algorithms↗
PubMed2002

Structural, biochemical, and expression analysis of two distinct insulin-like growth factor I receptors and their ligands in zebrafish.

We have cloned and characterized cDNAs encoding the zebrafish IGF ligands and receptors. Sequence comparison showed that the primary structures of zebrafish IGF-I, IGF-II, and IGF-I receptors (IGF-IRs) have been highly conserved in vertebrates. In contrast to the presence of a single IGF-IR gene in mammals, two distinct IGF-IR genes, termed igf-1ra and igf-1rb, were found in zebrafish. Structural and phylogenetic analyses indicated that both genes are orthologous to the human igf-1r gene. Immunoprecipitation studies with specific antibodies showed that both IGF-IR genes are expressed and both receptors bind to IGFs and des(1-3)IGF-I, but not to insulin. The spatio-temporal expression patterns of the two IGF-IRs and their ligands were determined using a combination of RT-PCR, whole mount in situ hybridization, and immunocytochemistry. Transcripts for both IGF-I and -II mRNAs were found throughout embryogenesis in a ubiquitous manner. In adult tissues, IGF-I mRNA was more abundant in liver and testis, and its level was increased after GH treatment, whereas IGF-II mRNA was not regulated by GH. IGF-IRa and IGF-IRb mRNAs and proteins were expressed in overlapping spatial domains, but exhibited distinct temporal expression patterns. In particular, the relative level of IGF-IRa mRNA was low during early embryogenesis and increased in the hatched larva, whereas the situation was reversed for IGF-IRb mRNA. In adult zebrafish, the overall tissue distribution patterns of the two IGF-IRs were similar, but there were differences in their cellular localization and relative abundance in defined cells/regions. The differential expression pattern of IGF-IRa and IGF-IRb suggest that they may play distinct roles in regulating the growth and development of zebrafish.

Amino Acid Sequence↗