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Biomedical subjects

D Y Chen

Publications and source records attributed to D Y Chen.

At least 19 recordsLinked to original sources
PubMed2004

Evaluation of mollusks as biomonitors to investigate heavy metal contaminations along the Chinese Bohai Sea.

Two gastropod species (Rapana venosa and Neverita didyma) and three bivalve species (Mytilus edulis, Crassostrea talienwhanensis and Ruditapes philippinarum) were collected from eight sites along the coastline of the Chinese Bohai Sea for the investigation of heavy metal contaminations. Cd, Co, Cu, Ni, Pb and Zn were analyzed by using pressure nebulization-inductively coupled plasma-mass spectrometer. Two certified reference materials Dogfish mussel (DORM-2) and Mussel (GBW 08571) were used to validate the methods and the obtained results proved to be in good agreement with the certified values. The results of the present study showed that Crassostrea talienwhanensis possessed a much greater ability for bioaccumulation of Cu and Zn than did the other species. Rapana venosa manifested the most bioaccumulation capacity of Cd. Among the five species, the Ruditapes philippinarum possessed the highest content of Ni. Furthermore, Cd, Cu and Zn contents in some gastropods and oysters samples exceeded the maximum permissible levels established by WHO. Due to their special bioaccumulation capacity of Cd and Ni, Rapana venosa and Ruditapes philippinarum had the potential of being used as biomonitors to control the aquatic contaminations of heavy metals.

Animals↗
PubMed2004

Predominance of Th1 cytokine in peripheral blood and pathological tissues of patients with active untreated adult onset Still's disease.

OBJECTIVE: To determine the type 1 T helper (Th1)/type 2 T helper (Th2) balance in the peripheral blood (PB) and pathological tissues of patients with active untreated adult onset Still's disease (AOSD). METHODS: The percentages of interferon gamma (IFNgamma)- and interleukin (IL)4-producing Th cells in the PB of 20 patients with active untreated AOSD, 20 patients with active rheumatoid arthritis (RA), and 20 healthy controls were determined by intracellular staining and flow cytometry. Serum levels of IL18 and soluble IL2 receptor were measured by enzyme linked immunosorbent assay. Levels of IFNgamma and IL4 messenger (m) RNA expression were examined by real time quantitative polymerase chain reaction in biopsy specimens of evanescent rash and synovitis from 8 patients with AOSD. RESULTS: Significantly higher IFNgamma-producing Th cells and Th1/Th2 ratio in PB were found in patients with AOSD than in healthy controls. Percentages of IFNgamma-producing Th cells and Th1/Th2 ratio in PB correlated significantly with clinical activity score and serum IL18 levels in patients with AOSD. Increased ratio of Th1/Th2 cytokine transcripts was seen in the biopsy specimens of evanescent rash and synovitis from patients with AOSD compared with normal skin controls and patients with OA. Th cell cytokine pattern in PB and cytokine mRNA expression in synovium were similar for patients with AOSD and with RA. After 3 months' treatment, clinical remission was associated with a marked decrease in the percentages of cytokine-producing Th1 cells, but not of the Th2 cells. CONCLUSION: A predominance of Th1 cytokine may precipitate the pathogenesis of AOSD.

Adult↗
PubMed2003

Polo-like kinase-1 in porcine oocyte meiotic maturation, fertilization and early embryonic mitosis.

Polo-like kinases (Plks) are a family of serine/threonine protein kinases that regulate multiple stages of mitosis. Expression and distribution of polo-like kinase 1 (Plk1) were characterized during porcine oocyte maturation, fertilization and early embryo development in vitro, as well as after microtubule polymerization modulation. The quantity of Plk1 protein remained stable during meiotic maturation. Plk1 accumulated in the germinal vesicles (GV) in GV stage oocytes. After germinal vesicle breakdown (GVBD), Plk1 was localized to the spindle poles at metaphase I (MI) stage, and then translocated to the middle region of the spindle at anaphase-telophase I. Plk1 was also localized in MII spindle poles and on the spindle fibers and on the middle region of anaphase-telophase II spindles. Plk1 was not found in the spindle region when colchicine was used to inhibit microtubule organization, while it accumulated as several dots in the cytoplasm after taxol treatment. After fertilization, Plk1 concentrated around the female and male pronuclei. During early embryo development, Plk1 was found to be in association with the mitotic spindle at metaphase, but distributed diffusely in the cytoplasm at interphase. Our results suggest that Plk1 is a pivotal regulator of microtubule organization and cytokinesis during porcine oocyte meiotic maturation, fertilization, and early embryo cleavage in pig oocytes.

Animals↗
PubMed2002

Effects of cisapride on oesophageal transit of solids in patients with progressive systemic sclerosis.

In most patients with progressive systemic sclerosis (PSS) the oesophagus is affected. Reflux symptoms are most frequent, whilst dysphagia also occurs. Cisapride, a prokinetic agent, may enhance motility along the gastrointestinal tract. The effects of cisapride on oesophageal transit were evaluated in 12 PSS patient using a solid-phase radionuclide oesophageal transit study. Each PSS patient was given cisapride 10 mg or placebo orally three times a day in a random, double-blind, crossover fashion. The results show that cisapride does not seem to have any impact on oesophageal transit in patients with PSS.

Administration, Oral↗
PubMed2002

[Protein kinases involved in the meiotic maturation and fertilization of oocyte].

The meiosis and fertilization of vertebrate oocyte are extensively regulated by various protein kinases. Recently, a great progress has been achieved in the studies on the molecular mechanisms of oocyte maturation, activation and fertilization. MPF and MAPK were found to be the key modulators of the cell cycle in oocyte, whose activation and inactivation result in the entry, arrest and exit of meiosis. Many protein kinases influence the meiosis by stimulating or inhibiting the activity of MPF and MAPK. Polo-like kinase activates MPF, whereas Mos initiates oocyte maturation and sustains MII arrest by activating MAPK. CaMK II down-regulates the MPF level through an ubiquitin-dependent pathway, which leads to the breakthrough of M phase arrest. Furthermore, p90(rsk) is involved in themeiosis regulation as a downstream regulator of MAPK; protein kinase C induces cortical granule exocytosis after fertilization and inhibits MAPK activity during maturation; and tyrosine protein kinase family members modulate the calcium release induced by fertilization. The cooperation of these protein kinases is essential to the development and fertilization of the oocyte.

Animals↗
PubMed2001

Maturation of the reconstructed oocytes by germinal vesicle transfer in rabbits and mice.

The present study was designed to evaluate the feasibility of germinal vesicle (GV) transfer in rabbits and mice. The GV oocytes were collected from ovaries and cultured in 20 microg/mL 3-isobutyl-1-methylxanthin (IBMX) in TCM199 medium, which caused oocytes to shrink, enlarging the perivitelline space to facilitate the GV removal and transfer. Pairs of GV-cytoplast complexes were fused with electric pulses, and the fused, reconstructed oocytes were cultured in TCM199 for 24 h. Results are as follows: 1) The exposure time of rabbit GV oocytes to IBMX medium affected the success of GV removal. For oocytes cultured for 2 and 3 h in IBMX medium, removed rates were 56% and 44, respectively, significantly higher (P < 0.05) than removal rates of GV oocytes cultured for 1 and 4 h (27% and 27%, respectively); 2) There was no significant difference (P > 0.1) in fusion and maturation rates of rabbit reconstructed oocytes collected at 72 and 84 h after initiation of FSH injection to donors; 3) eCG in the maturation media improved development of rabbit-to-rabbit GV transferred oocytes but had no positive effect on mouse-to-rabbit GV transferred oocytes; 4) When mouse GV-karyoplasts were injected into enucleated rabbit oocytes, fusion rates of GV-karyoplasts measuring 40- to 50-microm and 80- to 90-microm in diameters obtained were 84% and 93%, respectively. The rates were significantly higher (P < 0.05) than fusion rates after transferring GV-karyoplasts measuring 30- to 35-microm in diameter (63%). The maturation rate (89%) of reconstructed oocytes composed of 80- to 90-microm mouse GV-karyoplasts and rabbit GV-enucleated cytoplasts was higher than that seen for oocytes composed of 40- to 50-microm (77%, P<0.05) or 30- to 35-microm (59%, P<0.01) mouse karyoplasts. Thirty-five of the 63 (56%) mature mouse-to-rabbit reconstructed oocytes had the normal complement of 20 chromosomes.

1-Methyl-3-isobutylxanthine↗
PubMed2001

Enhancing fMRI contrast in awake-behaving primates using intravascular magnetite dextran nanopartieles.

Functional MRI in awake-behaving primates is an emerging tool for bridging the gap between human fMRI and neurophysiology information from nonhuman primates. We report the use of magnetite dextran nanoparticles (Feridex) as a blood-pool agent to enhance fMRI contrast-to-noise (CNR) in primate FMRI. The intravascular half-life of the magnetite dextran was long compared to lanthanide chelates (T(1/2) = 198 min) with shortened T(2) relaxation observed in blood and cerebral cortex. Greater than 3-fold enhancement in the percentage MR signal change was observed using nanoparticles (13%) compared with conventional BOLD fMRI (4%). The calculated regional cerebral blood volume in macaque primary visual cortex increased 32% with photic stimulation. The increased CNR allows greater flexibility in the design of awake-behaving primate fMRI studies with the potential for improvements in resolution and significantly shortened imaging times.

Animals↗
PubMed2001

Direct comparison of visual cortex activation in human and non-human primates using functional magnetic resonance imaging.

We report a technique for functional magnetic resonance imaging (fMRI) in an awake, co-operative, rhesus macaque (Macaca mulatta) in a conventional 1.5T clinical MR scanner, thus accomplishing the first direct comparison of activation in visual cortex between humans and non-human primates with fMRI. Activation was seen in multiple areas of striate and extra-striate visual cortex and in areas for motion, object and face recognition in the monkey and in homologous visual areas in a human volunteer. This article describes T1, T2 and T2* values for macaque cortex, suitable MR imaging sequences, a training schedule, stimulus delivery apparatus and restraining hardware for monkey fMRI using a conventional 19 cm knee coil. Much of our understanding of the functional organization of the primate brain comes from physiological studies in monkeys. Direct comparison between species using fMRI such as those described here will help us to relate the wealth of existing knowledge on the functional organization of the non-human primate brain to human fMRI.

Adolescent↗
PubMed2001

Mouse-rabbit germinal vesicle transfer reveals that factors regulating oocyte meiotic progression are not species-specific in mammals.

A series of experiments were designed to evaluate the meiotic competence of mouse oocyte germinal vesicle (GV) in rabbit ooplasm. In experiment 1, an isolated mouse GV was transferred into rabbit GV-stage cytoplast by electrofusion. It was shown that 71.8% and 63.3% of the reconstructed oocytes completed the first meiosis as indicated by the first polar body (PB1) emission when cultured in M199 and M199 + PMSG, respectively. Chromosomal analysis showed that 75% of matured oocytes contained the normal 20 mouse chromosomes. When mouse spermatozoa were microinjected into the cytoplasm of oocytes matured in M199 + PMSG and M199, as many as 59.4% and 48% finished the second meiosis as revealed by the second polar body (PB2) emission and a few fertilized eggs developed to the eight-cell stage. In experiment 2, a mouse GV was transferred into rabbit MII-stage cytoplast. Only 13.0-14.3% of the reconstructed oocytes underwent germinal vesicle breakdown (GVBD) and none proceeded past the MI stage. When two mouse GVs were transferred into an enucleated rabbit oocyte, only 8.7% went through GVBD. In experiment 3, a whole zona-free mouse GV oocyte was fused with a rabbit MII cytoplast. The GVBD rates were increased to 51.2% and 49.4% when cultured in M199 + PMSG and M199, respectively, but none reached the MII stage. In experiment 4, a mouse GV was transferred into a partial cytoplasm-removed rabbit MII oocyte in which the second meiotic apparatus was still present. GVBD occurred in nearly all the reconstructed oocytes when one or two GVs were transferred and two or three metaphase plates were observed in ooplasm after culturing in M199 + PMSG for 8 hr. These data suggest that cytoplasmic factors regulating the progression of the first and the second meioses are not species-specific in mammalian oocytes and that these factors are located in the meiotic apparatus and/or its surrounding cytoplasm at MII stage.

Animals↗
PubMed2001

Posttraining infusion of norepinephrine and corticotropin releasing factor into the bed nucleus of the stria terminalis enhanced retention in an inhibitory avoidance task.

The present study investigated whether the bed nucleus of the stria terminalis (BNST) is involved in formation and retrieval of affective memory. Male Wistar rats with cannulae bilaterally implanted into the BNST were trained on a one-trial step-through inhibitory avoidance task. Shortly after training they received bilateral intra-BNST infusion of lidocaine, various noradrenergic drugs, or corticotropin releasing factor (CRF). Results showed that posttraining intra-BNST infusion of lidocaine impaired retention. Posttraining intra-BNST infusion of norepinephrine or the alpha1 antagonist prazosin induced a dose- and time-dependent retention enhancement or deficit, respectively. The enhancing effect of norepinephrine was mimicked by the alpha1 agonist phenylephrine, and antagonized by prazosin at a non-impairing dose. Posttraining intra-BNST infusion of the alpha2 antagonist idazoxan or the beta antagonist propranolol failed to affect retention. Posttraining intra-BNST infusion of CRF also enhanced retention in a dose-dependent manner. Various drugs infused shortly before testing did not significantly influence locomotor activity and retention. These findings, taken together, suggest that the BNST is involved in memory formation processes for affective experience and norepinephrine released in the BNST acting via alpha1 receptors plays a critical role in this function.

Adrenergic alpha-Agonists↗
PubMed2001

Viable rabbits derived from reconstructed oocytes by germinal vesicle transfer after intracytoplasmic sperm injection (ICSI).

Abnormal oocyte spindle due to the improper function of ooplasm is associated with female infertility of advanced maternal age. A possible way to overcome this problem is to transfer an oocyte germinal vesicle (GV) which contains genetic materials of a patient with a history of poor embryo development to the cytoplast from a donor oocyte. Here we demonstrate that GV transfer is feasible using a rabbit model. When the GVs were transferred to auto- or hetero-cytoplasts of GV stage oocytes, around 80% of the reconstructed oocytes could mature in vitro and 7.1-9.4% of the oocytes developed to blastocyst stage after intracytoplasmic sperm injection (ICSI). Transfer of 93 fertilized eggs reconstructed via GV transfer into six recipients resulted in two live offspring. Results of this experiment indicate that GV transfer can potentially become a new approach in treatment of infertility because of advanced maternal age.

Animals↗
PubMed2001

Sucrose pretreatment for enucleation: an efficient and non-damage method for removing the spindle of the mouse MII oocyte.

Oocytes enucleated at metaphase II stage can support reprogramming of transferred nucleus and further developing to term. However, the first polar body in mice sometimes migrates away from the original place of expulsion, so the chromosomes of the oocyte will displace from the first polar body. Thus, it is not always possible to successfully enucleate according to the position of the first polar body. Here we use sucrose treatment to visualize metaphase spindle fibers and chromosomes with standard light microscopy. In the manipulation medium containing 3% sucrose, oocytes of poor quality become shrunken, deformed or fragmented, while oocytes of good quality in the same medium would show a swelling around the metaphase chromosomes and a transparent spindle area, shaped like "infinity" and "0". So it is easy to remove the well-distinguished spindle and chromosomes in oocytes of good quality. Re-examined by Hoechst 33342 stain under the UV light, the enucleation rate was 100%. There was no significant difference in IVF and cleavage rates between the sucrose treatment and the control group. In conclusion, this study demonstrated that 3% sucrose pretreatment can give a method for evaluating embryo quality and more importantly, it can, under a common microscope, allow the visualization of the spindle and chromosomes in oocytes of good quality and hence efficiently improve enucleation rate without any harm.

Anaphase↗
PubMed2001

Colonic transit disorders in systemic sclerosis.

Systemic sclerosis (SS) alters smooth muscle function throughout the gastrointestinal tract, the oesophagus being the segment most often involved. Involvement of the colon, though less common, may lead to life-threatening complications. We studied 23 unselected patients with SS and 20 age-matched healthy controls using radionuclide colon transit studies. The geometric centre (GC) at 4 and 24 hours was used to summarise overall transit in the colon. In patients with SS, colon transit was delayed (GC4: 0.39 +/- 0.36 vs 0.85 +/- 0.45; P=0.001) (GC24: 1.68 +/- 0.9 vs 2.58 +/- 1.08; P=0.006). These findings suggest that delayed colon transit is common in patients with SS.

Adolescent↗
PubMed2001

In vitro fertilisation of mouse oocytes reconstructed by transfer of metaphase II chromosomes results in live births.

The interaction between nucleus and cytoplasm can be explored through nuclear transfer. We describe here another tool to investigate this interaction: MII meiotic apparatus transfer (MAT) between mouse oocytes. In this study, the MII oocyte meiotic apparatus or spindle from C57BL/6 mice, a black strain, was transferred into an enucleated metaphase oocyte from Kunming mouse, a white strain. The results showed that the enucleation rate by treating oocytes with 3% sucrose was 100%, but the electrofusion efficiency was very low, with only 17.6% of reconstructed karyoplast-recipient cytoplasm pairs fused. When the fused oocytes were exposed to spermatozoa from C57BL/6 mice, 9 of 11 (82%) were fertilised. Eight reconstructed embryos at 1- to 4-cell stages were transferred into the oviducts of two synchronously pregnant Kunming strain fosters and one delivered two normal C57BL/6 offspring. This study indicates that MII meiotic apparatus or spindle sustains normal structure and function after micromanipulation and electrofusion. MAT provides a model for further research on the application of this technique to assisted human reproduction.

Animals↗
PubMed2001

Phosphorylation of p90rsk during meiotic maturation and parthenogenetic activation of rat oocytes: correlation with MAP kinases.

This paper reports on the activation of p90rsk during meiotic maturation and the inactivation of p90rsk after electrical parthenogenetic activation of rat oocytes. In addition, the correlation between p90rsk and MAP kinases after different treatments was studied. We assessed p90rsk activity by examining its electrophoretic mobility shift on SDS-PAGE and evaluated ERK1+2 activity by both mobility shift and a specific antibody against phospho-MAP kinase. The phosphorylation of p90rsk during rat oocyte maturation was a sequential process that may be divided into two stages: the first stage was partial phosphorylation, which was irrelevant with MAP kinases because p90rsk phosphorylation took place prior to activation of MAP kinases. The second stage inferred full activation occurred at the time when MAP kinases began to be activated (3 h after germinal visicle breakdown). Evidence for the involvement of MAP kinases in the p90rsk phosphorylation was further obtained by the following approaches: (1) okadaic acid (OA) accelerated the phosphorylation of both MAP kinases and p90rsk; (2) OA induced phosphorylation of both MAP kinases and p90rsk in the presence of IBMX; (3) when activation of MAP kinases was inhibited by cycloheximide, p90rsk phosphorylation was also abolished; (4) dephosphorylation of p90rsk began to take place at 3 h post-activation, temporally correlated with the completion of MAP kinase inactivation; (5) phosphorylation of both kinases was maintained in oocytes that failed to form pronuclei after stimulation; (6) OA abolished the dephosphorylation of both kinases after parthenogenetic activation. Our data suggest that MAP kinases are not required for early partial activation of p90rsk but are required for full activation of p90rsk during rat oocyte maturation, and that p90rsk dephosphorylation occurs following MAP kinase inactivation after parthenogenetic activation of rat oocytes.

1-Methyl-3-isobutylxanthine↗
PubMed2001

Phosphorylation of mitogen-activated protein kinase is regulated by protein kinase C, cyclic 3',5'-adenosine monophosphate, and protein phosphatase modulators during meiosis resumption in rat oocytes.

Mitogen-activated protein (MAP) kinase, protein kinase C (PKC), cAMP, and okadaic acid (OA)-sensitive protein phosphatases (PPs) have been suggested to be involved in oocyte meiotic resumption. However, whether these protein kinases and phosphatases act by independent pathways or interact with each other in regulating meiosis resumption is unknown. In the present study, we aimed to determine the regulation of meiosis resumption and MAP kinase phosphorylation by PKC, cAMP, and OA-sensitive PPs in rat oocytes using an in vitro oocyte maturation system and Western blot analysis. We found that ERK1 and ERK2 isoforms of MAP kinases existed in a dephosphorylated (inactive) form in germinal vesicle breakdown (GVBD)-incompetent and GVBD-competent germinal vesicle intact (GVI) oocytes as well as GVBD oocytes at equivalent levels. These results indicate that MAP kinases are not responsible for the initiation of normal meiotic resumption in rat oocytes. However, when GVBD-incompetent and GVBD-competent oocytes were incubated in vitro for 5 h, MAP kinases were phosphorylated (activated) in GVBD-competent oocytes, but not in meiotic-incompetent oocytes, suggesting that oocytes acquire the ability to phosphorylate MAP kinase during acquisition of meiotic competence. We also found that both meiosis resumption and MAP kinase phosphorylation were inhibited by PKC activation or cAMP elevation. Moreover, these inhibitory effects were overcome by OA, which inhibited PP1/PP2A activities. These results suggest that both cAMP elevation and PKC activation inhibit meiosis resumption and MAP kinase phosphorylation at a step prior to OA-sensitive protein phosphatases. In addition, inhibitory effects of cAMP elevation on meiotic resumption and MAP kinase phosphorylation were not reversed by calphostin C-induced PKC inactivation, indicating that cAMP inhibits both meiotic resumption and MAP kinase activation in a PKC-independent manner.

Animals↗
PubMed2001

Ion-induced manipulation of photochemical pathways in crown ether compounds based on fluorinated oligophenylenevinylenes: the border between ultrafast photoswitches and photoproduced nanomaterials.

The photochemical and photophysical properties of the crown ethers trans,trans-1,4-bis[2-(3',4'-benzo 15-crown 5)ethenyl]-2,3,5,6-tetrafluorobenzene (1) and trans,trans-1,4-bis[2-(3',4'-benzo 18-crown 6) ethenyl]-2,3,5,6-tetrafluorobenzene (2) were investigated in the absence and presence of groups I and II metal ions. The photophysical methods used include steady state flurescence, uv spectroscopy, and ultrafast transient absorption spectroscopy. Both compounds showed solvatochromic behavior, due to intramolecular charge transfer state formation, and efficient fluorescence in polar solvents. Photophysical behavior was dependent on the metal ion. The addition of metal ions that completely fit into the crown ether cavity resulted in significant blue shifts in the fluorescence emission spectra (chemosensing properties). Partially fitting ions changed the fluorescence spectra slightly. Transient absorption measurements revealed fast and slow decay components with time constants of 10-20 and 500-600 ps for all fitting ions, respectively. The latter is assigned to a trans-cis photoisomerization process, which decreased in efficiency in the presence of partially fitting ions, i.e., increasing ion size. Steady state irradiation showed clear evidence of a change in the absorption spectra. Trans-cis photoisomerization and [2 + 2] photocycloaddition were found to compete with fluorescence. The ions Li+, Na+, and Ca2+, which fit into the cavity, direct the photoisomerization. Larger ions (K+, Rb+, Sr2+ and Ba2+) that partially fit the cavity cause photocycloaddition. Quantum yields of the photoreaction are between 0.1 and 0.3. Analysis of the photo-product obtained for the 1-Sr2+ system revealed a compound with a molecular weight of nanosize dimension, which was equivalent to seven mass units of 1. The higher molecular weight product was formed due to alternately stacked supramolecular assemblies.

Crystallization↗