Biomedical subjects

Zheng Shen

Publications and source records attributed to Zheng Shen.

16 recordsLinked to original sources

PubMed2006

Nitric oxide affects preimplantation embryonic development in a rotating wall vessel bioreactor simulating microgravity.

Microgravity was simulated with a rotating wall vessel bioreactor (RWVB) in order to study its effect on pre-implantation embryonic development in mice. Three experimental groups were used: stationary control, rotational control and clinostat rotation. Three experiments were performed as follows. The first experiment showed that compared with the other two (control) groups, embryonic development was significantly retarded after 72 h in the clinostat rotation group. The second experiment showed that more nitric oxide (NO) was produced in the culture medium in the clinostat rotation group after 72 h (P<0.05), and the nitric oxide synthase (NOS) activity in this group was significantly higher than in the controls (P<0.01). In the third experiment, we studied apoptosis in the pre-implantation mouse embryos after 72 h in culture and found that Annexin-V staining was negative in the normal (stationary and rotational control) embryos, but the developmentally retarded (clinostat rotation) embryos showed a strong green fluorescence. These results indicate that microgravity induced developmental retardation and cell apoptosis in the mouse embryos. We presume that these effects are related to the higher concentration of NO in the embryos under microgravity, which have cause cytotoxic consequences.

Animals↗

PubMed2006

Double-cross hydrostatic pressure sample injection for chip CE: variable sample plug volume and minimum number of electrodes.

A novel sample injection method for chip CE was presented. This injection method uses hydrostatic pressure, generated by emptying the sample waste reservoir, for sample loading and electrokinetic force for dispensing. The injection was performed on a double-cross microchip. One cross, created by the sample and separation channels, is used for formation of a sample plug. Another cross, formed by the sample and controlling channels, is used for plug control. By varying the electric field in the controlling channel, the sample plug volume can be linearly adjusted. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip, without any electrode or external pressure pump, thus allowing a sample injection with a minimum number of electrodes. The potential of this injection method was demonstrated by a four-separation-channel chip CE system. In this system, parallel sample separation can be achieved with only two electrodes, which is otherwise impossible with conventional injection methods. Hydrostatic pressure maintains the sample composition during the sample loading, allowing the injection to be free of injection bias.

Electrodes↗

PubMed2006

Preserved implicit form perception and orientation adaptation in visual form agnosia.

Visual form agnosia is mainly characterized by profound deficits in visual form and shape discrimination. Previous studies have shown that patients retain the capacity for coordinated motor behaviors, color naming and implicit letter perception. However, it is unknown to what extent other visual functions, such as implicit form and orientation perception, are preserved. To address these questions, we investigated a single visual form agnosic patient, X.F., in two distinct experiments. X.F.'s visual lesions were mainly localized in the bilateral occipitotemporal cortex, with the dorsal visual stream and early visual cortex largely spared. In Experiment 1, X.F. named the color of different forms across 12 blocks of trials. After the first six blocks, the combinations of a form with its color were changed and the new combination was presented for the remaining six blocks. X.F.'s reaction time increased during the switch block and was significantly greater than the overall RT changes between adjacent, non-switch blocks. This indicates that X.F. retained the ability to perceive changes in form despite her inability to discriminate the forms. In Experiment 2, X.F. showed selective orientation adaptation effects to different spatial frequencies; that is, her contrast threshold was significantly higher when the adapting and test orientations were the same than when they were orthogonal, although her orientation discrimination performance was severely impaired. These data provide evidence of a functional dissociation between explicit and implicit visual abilities, and suggest that the residual early visual cortex mediates form and orientation processing in the absence of awareness.

Adaptation, Physiological↗

PubMed2006

Parallel analysis of biomolecules on a microfabricated capillary array chip.

This paper focused on a self-developed microfluidic array system with microfabricated capillary array electrophoresis (mu-CAE) chip for parallel chip electrophoresis of biomolecules. The microfluidic array layout consists of two common reservoirs coupled to four separation channels connected to sample injection channel on the soda-lime glass substrate. The excitation scheme for distributing a 20 mW laser beam to separation channels in an array is achieved. Under the control of program, the sample injection and separation in multichannel can be achieved through six high-voltage modules' output. A CCD camera was used to monitor electrophoretic separations simultaneously in four channels with LIF detection, and the electropherograms can be plotted directly without reconstruction by additional software. Parallel multichannel electrophoresis of series biomolecules including amino acids, proteins, and nucleic acids was performed on this system and the results showed fine reproducibility.

Amino Acids↗

PubMed2006

Studying protein-drug interaction by microfluidic chip affinity capillary electrophoresis with indirect laser-induced fluorescence detection.

We developed a microfluidic chip-affinity CE method based on indirect LIF detection to study protein-drug interactions. The interaction between heparin and BSA was quantitatively studied, as a model system. In our method, sodium fluorescein was chosen as background, and redistilled water as marker to monitor EOF. The electrophoretic mobility changes of BSA were measured, with various concentrations of heparin added to the running buffer. Each run was completed within 80 s. The binding constant was determined to be (1.24 +/- 0.05) x 10(3) M(-1), which was in good agreement with that reported in the literature.

Electrophoresis, Microchip↗

PubMed2006

Studying drug-plasma protein interactions by two-injector microchip electrophoresis frontal analysis.

We developed a simple, rapid, and sensitive two-injector microchip electrophoresis frontal analysis (MCE-FA) method for studying drug-plasma protein interactions. In this method, large volumes of a reference sample and drug-plasma protein mixture were simultaneously introduced into the respective sections of the microchannel through the separated injectors and then electrophoresed. Since the reference sample did not meet with the interacting species during migration, it could be used as an external standard. The interaction between heparin and HSA was quantitatively characterized as a model system. The binding constant was found to be (1.53 +/- 0.01) x 10(4) M(-1).

Anticoagulants↗

PubMed2006

Differential regulation of neutrophil chemotaxis to IL-8 and fMLP by GM-CSF: lack of direct effect of oestradiol.

Neutrophils are a normal constituent of the female reproductive tract and their numbers increase in the late secretory phase of the menstrual cycle prior to menses. Several cytokines are produced in female reproductive tract tissue. In particular granulocyte-macrophage colony-stimulating factor (GM-CSF), a potent activator of neutrophils, is secreted in high concentrations by female reproductive tract epithelia. We previously observed that GM-CSF synergizes strongly with interleukin-8 (IL-8) in enhancing chemotaxis of neutrophils. Thus we investigated whether pretreatment of neutrophils with GM-CSF would prime subsequent chemotaxis to IL-8 in the absence of GM-CSF. Surprisingly, a 3-hr pulse of GM-CSF severely diminished chemotaxis to IL-8, whereas N-formyl-methyl-leucyl-phenylalanine (fMLP)-mediated chemotaxis was retained. Conversely, when cells were incubated without GM-CSF they retained IL-8-mediated migration but lost fMLP chemotaxis. These changes in chemotaxis did not correlate with expression of CXCR1, CXCR2 or formyl peptide receptor. However, IL-8-mediated phosphorylation of p44/42 mitogen-activated protein kinase was greatly reduced in neutrophils that no longer migrated to IL-8, and was diminished in cells that no longer migrated to fMLP. Oestradiol, which is reported by some to exert an anti-inflammatory effect on neutrophils, did not change the effects of GM-CSF. These data suggest that neutrophil function may be altered by cytokines such as GM-CSF through modulation of signalling and independently of surface receptor expression.

Chemotaxis, Leukocyte↗

PubMed2006

VEGF gene expression is regulated post-transcriptionally in macrophages.

The macrophage is critical to the innate immune response and contributes to human diseases, including inflammatory arthritis and plaque formation in atherosclerosis. Vascular endothelial growth factor (VEGF) is an angiogenic cytokine that is produced by macrophages. To study the regulation of VEGF production in macrophages we show that stimulation of monocyte-macrophage-like RAW-264.7 cells by lipopolysaccharide (LPS) increases expression of VEGF mRNA and protein. Three alternative splicing VEGF mRNA isoforms are produced, and the stability of VEGF mRNA increases following cellular activation. To study post-transcriptional regulation of the VEGF gene the 3'-untranslated region (3' UTR) was introduced into the 3' UTR of the luciferase gene in a reporter construct. In both RAW-264.7 cells and thioglycollate-elicited macrophages, the 3' UTR sequence dramatically reduces reporter expression. Treatment with activators of macrophages, including LPS, lipoteichoic acid, and VEGF protein, stimulates expression of 3' UTR reporters. Finally, mapping studies of the 3' UTR of VEGF mRNA show that deletion of the heterogeneous nuclear ribonucleoprotein l binding site affects basal reporter expression in RAW-264.7 cells, but does not affect reporter activation with LPS. Together these results demonstrate that a post-transcriptional mechanism contributes to VEGF gene expression in activated macrophage cells.

Alternative Splicing↗

PubMed2005

50-Hz magnetic field (0.1-mT) alters c-fos mRNA expression of early post implantation mouse embryos and serum estradiol levels of gravid mice.

BACKGROUND: We exposed pregnant mice to magnetic or sham fields for 24 hr/day during Gestation Day (GD) 5.5-8.5 to study the effects of 50-Hz 0.1-mT sinusoidal magnetic fields on early pregnancy in mouse embryos and mice. METHODS: Mice were sacrificed on GD 8.5. Embryos and blood samples were collected. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the expression of embryo c-fos mRNA. The blood samples were tested through radioimmunoassay for serum estradiol levels and general examinations. RESULTS: We found that the expression of c-fos mRNA of embryos under exposure was enhanced. We reported that 50-Hz 0.1-mT magnetic exposure induced the decline of serum estradiol levels of pregnancy mice on GD 8.5. General examinations of blood including white blood cell (WBC) count, red blood cell (RBC) count, and hemoglobin (HGB) did not show significant differences between the exposure group and the control group (sham exposure). CONCLUSIONS: Under the experimental conditions, 50-Hz 0.1-mT sinusoidal magnetic fields affected the development of early pregnancy mouse embryos and the dams to some extent.

Animals↗

PubMed2005

Chiral separations on multichannel microfluidic chips.

Chiral separations of FITC-labeled basic drugs on multichannel microfluidic chips with LIF detector were investigated. A preliminary screening procedure for seven neutral CDs was performed under optimized conditions for chiral separations of three FITC-labeled drugs (baclofen, norfenefrine, and tocainide) on a mono-channel microfluidic chip. According to the results of screening, FITC-baclofen and FITC-norfenefrine as well as two chiral selectors including gamma-CD and dimethyl-beta-CD (DM-beta-CD) were selected as models to perform chiral separations on a two-channel chip. FITC-baclofen enantiomers were separated completely by gamma-CD in one channel, while resolution of FITC-norfenefrine enantiomers was achieved by DM-beta-CD in the other channel in the same run. Furthermore, the feasibility of using one chiral selector to separate multiple chiral samples was studied on a four-channel chip. These results show that multichannel chip has a potential for chiral high-throughput screening.

Baclofen↗

PubMed2003

Lie detection with contingent negative variation.

topographies of contingent negative variation (CNV) were recorded in a paradigm of delayed response with feedback for three kinds of faces: familiar, strange and target. Subjects made responses to the faces according to whether the faces were familiar or not, but also, gave deliberately deceptive responses to target faces to 'cheat the computer'. Subjects were told that the computer could judge whether they were being honest or not. For each trial of the experiment, if subjects cheated the computer successfully and their responses were judged as honest and they were given a reward, otherwise they received a penalty. In this simulated lie detection test, CNV exhibited more negative shifts for target than those for non-target (familiar and strange). These differences could be accounted for by subjects' motivation and uncertainty about passing the test. With the results of further paired t-tests between target and non-target faces at each electrode, CNV was demonstrated as a reliable indicator for lie detection. In addition, vector length was used to capture global CNV information and was found to be a very good indicator, even better than the CNV information at the individual electrode sites.

Adolescent↗

PubMed2003

[Effects of microgravity on human cognitive function in space flight].

In researches of space flight, studies on the effects of microgravity on cognitive function were relatively few. This paper reviews recent progress on this topic. It was shown that under the condition of microgravity, spatial orientation, motion perception and early process of object recognition were impaired to a certain degree. Capability of muscle movement and coordination was lowered, while higher cognitive functions, such as logic reasoning task, the speed and accuracy of short-term memory retrieval were less affected by microgravity. But long-term memory tasks and performance in which attention processes were needed (e.g., tracking task, selective response task), were impaired during space flight or under simulated weightlessness condition.

Cognition↗

PubMed2002

The hole precedence in face but not figure discrimination and its neuronal correlates.

The discriminative tasks of face and geometrical figure were trained in three rhesus monkeys. The hole feature speeds up learning of face discrimination, but hampers learning of figure discrimination. By reducing presentation duration of the stimuli, the detecting precedence appears to be the hole feature of the face component, while it appears to be shape feature of figures. The patterns of neuron firings in inferior temporal cortex (IT) are consistent with the context-dependent precedence of hole feature. The results might suggest that the neural correlates exist not only in IT neurons, but also in combination with executive mechanism.

Animals↗

PubMed2002

Shape predominant effect in pattern recognition of geometric figures of rhesus monkey.

Three monkeys were trained successively with discrimination, concurrent matching to sample, and sameness-difference judgment tasks in which learning curves were compared. Then, the display duration for the stimuli was shortened to 100, 50, and 30 ms respectively to test the changes in accuracy and reaction time. All results in three experimental paradigms suggested consistently that the geometric shape (triangle, circle, and square) plays a more predominant role than topological features (the hole inside of a figure and the hole numbers) in monkey figure recognition. The results are different from the experiment by human subjects who presented hole predominant in figure recognition. Therefore, the precedence in perception depends on subject species, stimulus set, and ecological significance of the perceiving process.

Animals↗

PubMed2002

Analysis of amlodipine in human plasma by liquid chromatography-mass spectrometry.

A simple, sensitive, and specific liquid chromatographic method coupled with electrospray ionization (ESI)-mass spectrometry for the determination of amlodipine is developed. After extraction by ethyl acetate using nicardipine as the internal standard, solutes are separated on a C18 column with a mobile phase of methanol-1% HAc (65:35). Detection is performed on an air pressure ionization single quadruple mass spectrometer equipped with an ESI interface and operated in positive-ionization mode. Amlodipine quantitation is realized by computing the peak-area ratio (amlodipine-nicardipine) of the extracts analyzed in single ion monitoring mode (m/z 431 and m/z 480 for amlodipine and nicardipine, respectively) and comparing them with the calibration curve (r = 0.9991).

Amlodipine↗

PubMedDate not supplied

Octreotide augments the effects of hepatic arterial occlusion in treating a rat liver tumor model.

BACKGROUND/AIMS: To observe if octreotide can augment the effects of hepatic arterial occlusion for transplanted cancer in rat's liver. METHODOLOGY: Walker 256 carcinosarcoma was transplanted into rat's liver to create the liver cancer model. Hepatic arterial ligation was used to block the hepatic arterial blood supply. Rats bearing tumor were divided into three groups: control group, HAL (hepatic arterial ligation) group, and HAL plus octreotide group. Change of tumor volume and tumor growth inhibiting rate after therapy were evaluated. Hoechst 33342 labeling assay was used to analyze the blood perfusion of tumor (the labeled cells' number presenting blood perfusion). Expression of vascular endothelial growth factor and matrix metalloproteinase-1 mRNA was detected by in situ hybridization, and the level of serum vascular endothelial growth factor was assayed by ELISA. RESULTS: Six days after hepatic arterial ligation, the mean tumor volume in control group, HAL group, and HAL plus octreotide group was 0.103 +/- 0.043 cm3, 0.030 +/- 0.018 cm3, and 0.016 +/- 0.005 cm3, respectively. The tumor volume in the two behind groups was smaller than that in the control group (P < 0.01), and the tumor growth-inhibiting rate was 70.8%, and 84.5%, respectively. Compared with the HAL group, the tumor volume in HAL plus octreotide group decreased significantly (P < 0.05). Hoechst 33342 labeled cells' number in control group, HAL group, and HAL plus octreotide group was 369.7 +/- 30.2, 344.1 +/- 26.0, and 323.2 +/- 40.4, respectively. The number in HAL combined with octreotide group decreased significantly compared with that in control group (P < 0.05), which suggested that the blood perfusion of tumor in HAL plus octreotide group decreased significantly. The expression of vascular endothelial growth factor and matrix metalloprotenase-1 mRNA decreased slightly, but not significantly in HAL plus octreotide group compared with that in HAL group (P > 0.05). CONCLUSIONS: The results suggest that octreotide can promote the effects of hepatic arterial occlusion therapy for transplanted cancer in rat's liver. Decreasing the blood perfusion of tumor after hepatic arterial blockage maybe one of its major mechanisms.

Animals↗