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Biomedical subjects

W Ji

Publications and source records attributed to W Ji.

At least 19 recordsLinked to original sources
PubMed2006

Selective nontemplated adsorption of organic molecules on nanofacets and the role of bonding patterns.

A key element of functionalizing nanocrystals with organic molecules is the nontemplated selective adsorption of different molecules on different facets. Here we report scanning-tunneling-microscopy images of perylene-3,4,9,10-tetracarboxylic-dianhydride and 2,5-dimethyl-N,N'-dicyanoquinonediimine on silver, demonstrating selective adsorption on different facets. We also report first-principles calculations that account for the data and show that bonding, which controls selectivity, occurs via the end atoms, while the molecule's midregion arches away from the substrate. The results are also consistent with data that have been interpreted in terms of bonding via the midregion.

Journal Article↗
PubMed2006

Role of lateral alkyl chains in modulation of molecular structures on metal surfaces.

We use low energy electron diffraction, scanning tunneling microscopy, first-principles density-functional theory, and molecular mechanics calculations to analyze the adsorption and growth of quinacridone derivatives (QA) with alkyl chains of 4 and 16 carbon atoms on a Ag(110) substrate. Surprisingly, we find that the alkyl chains determine the orientation of the molecular overlayers. While the interaction of QA and the Ag substrate is primarily due to chemical bonding of oxygen to the silver substrate, determining the molecular orientation and preferred adsorption site, the intermolecular arrangement can be adjusted via the length of alkyl chains. We are thus able to fabricate uniform QA films with very well controlled physical properties.

Journal Article↗
PubMed2006

Selective analysis of molecular states by functionalized scanning tunneling microscopy tips.

Selective analysis of molecular states in scanning tunneling microscopy (STM) has so far been achieved in a few cases by tuning the bias range of the STM in high-resolution measurements. Correspondingly, perylene adsorbed in a close-packed monolayer on Ag(110) is imaged mainly through the pi states of the molecule. By contrast, functionalizing the STM tip with a perylene molecule leads to a mismatch between the energy levels of the STM tip and the molecule adsorbates and, instead, images only the metal states of the underlying silver surface. The observation opens a route for better energy selectivity in electron transport measurements through organic interfaces.

Journal Article↗
PubMed2006

Establishment of a cell-based drug screening system for identifying selective down-regulators of mPGES-1.

OBJECTIVE: To establish a drug screening system based on transcriptional regulation of microsomal PGE(2) synthase 1 (mPGES-1), cyclooxygenase 1 (COX-1) and 2 (COX-2) for discovering selective down-regulators of mPGES-1. METHODS: The upstream regulatory sequences of mPGES-1, COX-1, COX-2 were respectively cloned into pGL3B-neo vector containing luciferase gene and neomycin resistance gene (the pGL3B-neo vector had been previously constructed by cloning the neomycin resistance gene into the Sal I site of the pGL3-Basic vector). After that, the recombinant reporter gene vectors pGL3B-neo/mPGES-1, pGL3B-neo/COX-1, pGL3B-neo/COX-2 were respectively transfected into A549 cells and therefore stable cell lines, namely M 1, M 2 and M 3, were obtained. Samples were detected then by testing luciferase activity of M 1, M 2 and M 3 cells in microtiter wells to identify compounds that can selectively down-regulate mPGES-1 expression. Through luciferase activity testing, the compounds which had more than 40 % inhibition ratio on M 1 and less than 20 % inhibition ratio on M 2 and M 3 cells could be regarded as hits. RESULTS: Using the cell-based reporter gene assay, we screened compounds for selectively down-regulation of mPGES-1 expression and several compounds were discovered. CONCLUSION: A cell-based drug screening system was established to screen selective down-regulators of mPGES-1 expression, and compound CM188 was identified, which might become a lead compound for novel anti-arthritic drugs.

Acetates↗
PubMed2006

Synthesis of "cactus" top-decorated aligned carbon nanotubes and their third-order nonlinear optical properties.

We report a new morphology of "cactus" top-decorated aligned carbon nanotubes grown by the PECVD method using pure C2H2 gas. Unlike most previous reports, no additional carrier gas is used for pretreatment. Carbon nanotubes can still grow and maintain the tubular structure underneath the "cactus" tops. It is proposed that the H atoms produced by the dissociation of C2H2 activate the catalyst nanoparticles. Scanning electron microscopy (SEM) shows that the top "cactus" morphology is composed of a large quantity of small nanosheets. Transmission electron microscopy (TEM) reveals the amorphous carbon nature of these "cactus" structures. The formation of these "cactus" structures is possibly due to covalent absorption and reconstruction of carbon atoms on the broken graphite layers of nanotubes produced by the strong ion bombardment under plasma. The third-order optical nonlinearities and nonlinear dynamics are also investigated. The third-order nonlinear susceptibility magnitude /chi(3)/ is found to be 2.2 x 10(-11) esu, and the relaxation process takes place in about 1.8 ps.

Cactaceae↗
PubMed2006

Developmental potential of vitrified holstein cattle embryos fertilized in vitro with sex-sorted sperm.

In vitro fertilization (IVF) is a feasible way to utilize sex-sorted sperm to produce offspring of a predetermined sex in the livestock industry. The objective of the present study was to examine the effects of various factors on bovine IVF and to systematically improve the efficiency of IVF production using sex-sorted sperm. Both bulls and sorting contributed to the variability among differential development rates of embryos fertilized by sexed sperm. Increased sorting pressures (275.8 to 344.75 kPa) did not have a significant effect on the in vitro fertility of the sorted sperm; neither did an extended period of 9 to 14 h from semen collection to sorting. As few as 600 sorted sperm were used to fertilize an oocyte, resulting in blastocyst development of 33.2%. Postwarming of vitrified sexed IVF embryos resulted in high morphological survival (96.3%) and hatching (84.4%) rates, similar to those fertilized by nonsexed sperm (93.1 and 80.6%, respectively). A 40.9% pregnancy rate was established following the transfer of 3,627 vitrified, sexed embryos into synchronized recipients. This was not different from the rates with nonsexed IVF (41.9%, n = 481), or in vivo-produced (53.1%, n = 192) embryos. Of 458 calves born, 442 (96.5%) were female and 99.6% appeared normal. These technologies (sperm sexing-IVF-vitrification-embryo transfer) provide farmers, as well as the livestock industry, with a valuable option for herd expansion and heifer replacement programs. In summary, calves were produced using embryos fertilized by sex-sorted sperm in vitro and cryopreserved by rapid cooling vitrification.

Animals↗
PubMed2005

Ultrafast and large third-order nonlinear optical properties of CdS nanocrystals in polymeric film.

We report the ultrafast and large third-order nonlinear optical properties of CdS nanocrystals (NCs) embedded in a polymeric film. The CdS NCs of 2 nm radius are synthesized by an ion-exchange method and highly concentrated in the two layers near the surfaces of the polymeric film. The two-photon absorption coefficient and the optical Kerr coefficient are measured with laser pulses of 250 fs duration at 800 nm wavelength. The one-photon and two-photon figures of merit are determined to be 3.1 and 1.3, respectively, at irradiance of 2 GW/cm(2). The observed nonlinearities have a recovery time of approximately 1 ps. The two-photon-generated free carrier effects have also been observed and discussed. These results demonstrate that CdS NCs embedded in polymeric film are a promising candidate for optical switching applications.

Journal Article↗
PubMed2001

Energy substrate requirement for in vitro maturation of oocytes from unstimulated adult rhesus monkeys.

The energy substrates lactate, pyruvate, and glucose were evaluated for supporting in vitro cytoplasmic maturation of rhesus monkey oocytes. A total of 321 cumulus-oocyte complexes (COCs) aspirated from > or = 1000 microm diameter follicles of unstimulated adult monkeys were matured in one of six media with various individual or combinations of energy substrates: (1) mCMRL-1066 (control); (2) HECM-10 (containing 4.5 mM lactate); (3) HECM-10+0.2 mM pyruvate; (4) HECM-10 + 5.0 mM glucose; (5) HECM-10+ 0.2 mM pyruvate + 5.0 mM glucose; and (6) HECM-10 minus lactate + 5.0 mM glucose. All media contained gonadotropins, oestradiol, and progesterone. Following maturation, all mature oocytes were subjected to the same in vitro fertilization and embryo culture procedures. Oocytes matured in control medium or in treatment groups 4 and 6 had the best morulae+ blastocysts developmental responses (35, 36, and 32%, respectively, P < 0.05). HECM-10 + 0.2 mM pyruvate + 5.0 mM glucose for COC maturation supported intermediate embryonic development (16% morulae + blastocysts). The lowest (P < 0.05) morula + blastocyst developmental responses were obtained after maturation of COCs in HECM-t10 and HECM-10 + 0.2 mM pyruvate (4 and 6%, respectively). The COCs matured in glucose-containing medium showed greater levels of cumulus expansion than those in glucose-free medium. These results indicate that (a) glucose is both necessary and sufficient as the energy substrate for supporting optimal cytoplasmic maturation in vitro of oocytes from unstimulated rhesus monkeys; (b) pyruvate suppresses the stimulatory effect of glucose on oocyte maturation; (c) glucose is involved in cumulus expansion; (d) cumulus expansion is not a reliable indicator of primate oocyte competence.

Animals↗
PubMed2001

Changes of urinary steroid conjugates and gonadotropin excretion in the menstrual cycle and pregnancy in the Yunnan snub-nosed monkey (Rhinopithecus bieti).

The Yunnan snub-nosed monkey (Rhinopithecus bieti) is one of the most endangered species in the world, and it is endemic to China. According to our knowledge, there was no information on reproduction for this species. The present study was designed to understand the characteristics of reproductive hormone secretion during the menstrual cycle and pregnancy of this species by monitoring urinary estrone conjugate (E1C), pregnanediol-3-glucuronide (PdG), bioactive follicle-stimulating hormone (FSH), and luteinizing hormone (LH). The urine samples were collected each day from four adult females for eight menstrual cycles, and once in 3 days during pregnancy (three full-term pregnancies, one mid-term abortion). The steroid conjugate was tested by radioimmunoassays (RIAs), and bioactive FSH and LH levels were measured in vitro by the sensitive bioassays granulosa cell aromatize bioassay (GAB) and rat interstitial cell testosterone (RICT), respectively. The results showed that: 1) E1C presented a preovulatory peak (183.9 +/- 8.6 ng/mgCr) followed by a definite elevation of PdG; 2) PdG in the luteal phase (754.4 +/- 30.6 ng/mgCr) was three- to fivefold higher than during the corresponding follicular phase (198.3 +/- 11.4 ng/mgCr); 3) the peaks of bio-LH and bio-FSH were on the same day, while the E1C peak was 1 or 2 days before the peaks for these two hormones; 4) bio-FSH levels were higher in the follicular phase than in the luteal phase, and bio-LH levels elevated slightly in the luteal phase; 5) the mean cycle length was 23.6 +/- 3.5 days (n = 3) based upon successive urinary LH peaks; 6) based on the interval from the day of E1C peak to the day of parturition, the gestation was 203.7 +/- 2.5 days (n = 3); and 7) both E1C and PdG increased and remained high after pregnancy, with a sharp decrease in basal levels following parturition or mid-term abortion. The results suggested that the pattern of reproductive hormones for R. bieti is similar to that of other Old World monkeys, but the concentration of the hormones is different from that of other species. This species has a longer progestation period, which may be related to its classification status.

Animals↗
PubMed2001

DQX1, an RNA-dependent ATPase homolog with a novel DEAQ box: expression pattern and genomic sequence comparison of the human and mouse genes.

DQX1 is a novel gene related to the RNA-dependent ATPases. The gene was classified as a member of the DEAD/H family on the basis of the conserved order and spacing of ten short protein motifs. The unique features of DQX1 include replacement of the signature DEAH motif with DEAQ and the absence of the helicase motif. We determined the coding sequences of human and mouse DQX1, which encode proteins of 717 and 718 amino acids with 84% amino acid sequence identity. The 3.2-kb Dqx1 transcript has highest expression in muscle and liver. DQX1 is located between AUP1 and HOX11L1 in a gene-dense region of human Chromosome (Chr) 2p13 and mouse Chr 6. Although DQX1 is within the nonrecombinant region for the mouse neuromuscular mutant mnd2, no difference in coding sequence, transcript length, or transcript abundance was observed between normal mice and mnd2 mutant mice. The ubiquitous expression of DQX1 and its close phylogenetic relationship to the yeast pre-mRNA processing (Prp) proteins suggest a role in cellular RNA metabolism.

Adenosine Triphosphatases↗
PubMed2001

Activation-induced cell death in peripheral blood mononuclear cells (PBMCs) from patients with chronic hepatitis B may be related to abnormal production of interleukin 12 and 10.

Peripheral blood mononuclear cells (PBMCs) from 70 patients with chronic hepatitis B and 32 normal healthy persons were isolated and cultured with or without Staphylococcus aureus enterotoxin B (SEB; 0.2 mg x l(-1)) and recombinant HBcAg (rHBcAg; 1.0 mg x l(-1)) for 48 h in vitro. After incubation, the cells were harvested by centrifugation and apoptosis of the PBMCs was studied by staining with fluorescent dyes YOPRO-1 and Hoechst 33342. The levels of IL-12 and IL-10 in the serum and the supernatants of cultured PBMCs were assayed by ELISA. The levels of IL-12 heterodimer in the serum and the supernatants of PBMCs cultured with SEB or rHBcAg were lower in patients than controls. The levels of IL-10 in both the serum and supernatants were higher in patients than controls. In addition, the percentage of apoptotic cells in PBMCs from the infected patients was significantly greater than from normal persons in the presence or absence of SEB and rHBcAg. Patients seropositive for HBeAg had much greater percentage of apoptotic cells in the PBMCs cultured with rHBcAg than patients seronegative for HBeAg, reaching 24.08%. We speculate that activation-induced cell death of PBMCs in the patients with hepatitis B may be related to abnormal expression of IL-12 heterodimer and IL-10, which may lead to persistent infection in the patients.

Adult↗
PubMed2001

Sex-biased dispersal and a density-independent mating system in the Australian brushtail possum, as revealed by minisatellite DNA profiling.

Natal dispersal can have important effects on mammal population structure and dynamics following a local population crash. Such dispersal is of practical importance when applied to the control of pest species because dispersal may significantly, and undesirably, reduce the population recovery time following a control operation. The relative dispersal rate of the sexes is also critical because that too will affect the rate of population increase. Here, we describe a field experiment in which we reduce the density of two populations of the Australian brushtail possum, and use genetic similarity, as estimated by minisatellite DNA profiles, to investigate dispersal in the original (undisturbed) and recovering populations. Our results show that the genetic similarity within the undisturbed populations was lower between males than between females. Conversely, the genetic similarities between males and females in the two recovering populations were not significantly different, while relatedness among males was significantly higher in the recovering populations when compared with those in the pre-removal populations. These data indicate two important characteristics of dispersal in possums: (i) that dispersal in established populations is sex biased towards males; and (ii) that within the first 3 years following population control, 'the vacuum effect', whereby individuals from areas adjacent to a control area expand their home range and invade the depopulated area, is the most important factor in the re-colonization process for possums. We found no evidence that the mating system, which is polygynous, varied when the density was markedly reduced. These results indicate that drastic reductions in population density by conventional control will not affect the rate of spread of biological control agents that rely on sexual transmission for dissemination.

Animals↗
PubMed2001

Maturation of rhesus monkey oocytes in chemically defined culture media and their functional assessment by IVF and embryo development.

This study compared success of in-vitro maturation of rhesus monkey oocytes in protein-free versus serum-containing culture systems, assessed by embryo development subsequent to IVF. Four media were tested: (i) modified Connaught Medical Research Laboratories medium (mCMRL-1066); (ii) hamster embryo culture medium-10 (HECM-10); (iii) control: mCMRL-1066 + 20% bovine calf serum (BCS); (iv) HECM-10 + 20% BCS. Immature oocytes from FSH-stimulated rhesus monkeys were allocated among the media containing ovine FSH (5 microg/ml) and LH (10 microg/ml) and cultured for 36-40 h. Metaphase II ova were inseminated and putative zygotes were cultured in mCMRL-1066 + 20% BCS until development arrested. Ova matured in all four media had similar (P> 0.05) potential to initiate (66, 67, 82 and 69% respectively) and complete meiotic maturation (60, 50, 76 and 57% respectively). Inseminated ova in all groups had similar potential to be fertilized (86, 83, 84 and 90% respectively), cleave (71, 83, 76 and 90% respectively) and develop to the blastocyst stage (19, 17, 16 and 30% respectively). These results indicate for the first time that primate oocytes can be successfully matured in protein-free medium, with subsequent blastocyst development, comparable to responses in complex medium with serum. This finding will facilitate studies on mechanisms regulating primate oocyte maturation.

Animals↗
PubMed2001

Effect of age and breeding season on the developmental capacity of oocytes from unstimulated and follicle-stimulating hormone-stimulated rhesus monkeys.

Effects of age and season on the developmental capacity of oocytes from unstimulated and FSH-stimulated rhesus monkeys were examined. Immature cumulus-oocyte complexes were matured in vitro in modified CMRL-1066 medium containing 20% bovine calf serum and subjected to in vitro fertilization followed by embryo culture. After fertilization, ova from unstimulated prepubertal monkeys displayed lower development to morula (4%) than those from unstimulated adult females (18% in breeding season and 22% in nonbreeding season). No developmental difference was found between ova from unstimulated adult monkeys in breeding and nonbreeding seasons. However, ova from FSH-primed prepubertal monkeys displayed greater development to blastocyst stage (54%) than those from adult monkeys in the breeding season (16%) and nonbreeding season (0%); and ova from FSH-primed adult females in the breeding season had significantly (P < 0.05) greater developmental competence than those obtained in the nonbreeding season (> or = morula stage, 54% vs. 3%; blastocyst stage, 16% vs. 0%). These data indicate that 1) rhesus monkey oocytes acquire developmental competence in a donor age-dependent manner, and 2) animal age and breeding season modulate the effect of FSH on oocyte developmental competence in the rhesus monkey.

Aging↗
PubMed2001

Effects of acetylcholine and atropine on plasticity of central auditory neurons caused by conditioning in bats.

In the big brown bat (Eptesicus fuscus), conditioning with acoustic stimuli followed by electric leg-stimulation causes shifts in frequency-tuning curves and best frequencies (hereafter BF shifts) of collicular and cortical neurons, i.e., reorganization of the cochleotopic (frequency) maps in the inferior colliculus (IC) and auditory cortex (AC). The collicular BF shift recovers 180 min after the conditioning, but the cortical BF shift lasts longer than 26 h. The collicular BF shift is not caused by conditioning, as the AC is inactivated during conditioning. Therefore it has been concluded that the collicular BF shift is caused by the corticofugal auditory system. The collicular and cortical BF shifts both are not caused by conditioning as the somatosensory cortex is inactivated during conditioning. Therefore it has been hypothesized that the cortical BF shift is mostly caused by both the subcortical (e.g., collicular) BF shift and the activity of nonauditory systems such as the somatosensory cortex excited by an unconditioned leg-stimulation and the cholinergic basal forebrain. The main aims of our present studies are to examine whether acetylcholine (ACh) applied to the AC augments the collicular and cortical BF shifts caused by the conditioning and whether atropine applied to the AC abolishes the cortical BF shift but not the collicular BF shift, as expected from the preceding hypothesis. In the awake bat, we made the following findings. ACh applied to the AC augments not only the cortical BF shift but also the collicular BF shift through the corticofugal system. Atropine applied to the AC reduces the collicular BF shift and abolishes the cortical BF shift which otherwise would be caused. ACh applied to the IC significantly augments the collicular BF shift but affects the cortical BF shift only slightly. ACh makes the cortical BF shift long-lasting beyond 4 h, but it cannot make the collicular BF shift long-lasting beyond 3 h. Atropine applied to the IC abolishes the collicular BF shift. It reduces the cortical BF shift but does not abolish it. Our findings favor the hypothesis that the BF shifts evoked by the corticofugal system, and an increased ACh level in the AC evoked by the basal forebrain are both necessary to evoke a long-lasting cortical BF shift.

Acetylcholine↗
PubMed2001

Pathologic features of occult lymphatic metastasis in supraglottic carcinoma.

OBJECTIVE: To study the pathologic features of occult lymphatic metastasis in supraglottic carcinoma. METHODS: Serial sections of 153 neck dissection specimens in 100 patients with supraglottic carcinoma were evaluated under the microscope. RESULTS: In 100 patients, 38 had occult metastatic lymph nodes. 51 metastatic lymph nodes were found in pathology, and their sizes ranged from 0.5 cm to 2.6 cm (average 1.1 cm). The distribution of 51 lymph nodes was 1 in level I (2%), 37 in level II (73%), 12 in level III (24%), and 1 in level IV (2%). Among the 51 nodes, 21 (41%) were early stage, 18 (35%) were growth stage, 7 (14%) were tull stage, and 5 (10%) were extracapsular stage. The differentiation degree and appearance of supraglottic carcinoma was not directly related with occult metastasis. CONCLUSION: The occult metastatic rate of supraglottic carcinoma is high, and selective neck dissection may be necessary.

Adult↗
PubMed2001

[A report of twice outbreak epidemic of acute tonsillitis and acute pharyngitis].

OBJECTIVE: To discuss the pathogenic factors, prevention and treatment of fulminant epidemic of acute tonsillitis and acute pharyngitis. METHOD: We investigated and analysed the cases of twice fulminant epidemic of acute tonsillitis and acute pharyngitis. RESULT: In the first time, 91 patients among 518 persons were attacted, the sick rate was 17.6%. In the second time, 39 among 295 persons were attacted, the sick rate was 13.2%. The main symptoms were pharyngodynia and fever. Bacterial culture of throat swab of 20 cases of the first time and 17 cases of the second time were carried out. The positive rate of beta-hemolytic streptococcus was 82.5% and 85.3% respectively. CONCLUSION: Environment and individual health condition are important factors in the fulminant epidemic of acute tonsillitis and acute pharyngitis.

Acute Disease↗