[Advances in experimental pharmacological study of Chinese Taihe chickens].
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Aging↗
Biomedical subjects
M Li
Publications and source records attributed to M Li.
[Removal of a broken needle in the left pterygoid fossa:report of one case]
OBJECTIVE:To research the application of orthodontic techniques of edgewise brackets to enhance the curative effect of stabilizing the loose teeth.METHODS: Between 1993-1998,we applied orthodontic techniques of Edgewise brackets to treat 35 cases of patients which include 58 loosen teeth caused by trauma factors,most adopting edgewise brackets plus round wire.RESULTS: We have obtained excellent curative effect in 45 teeth,good curative effect in 9 teeth,and 4 teeth failed.CONCLUSION: Orthodontic technique of Edgewidw brackets is a reliable method to stabilize the loose teeth.Compared with conventional arch bar splint fixation,the Edgewise technique has its unique advantage.
Journal Article↗
[The 1. 54 microm laser and upconversion luminescence of YELPP noncrystalline induced by 969 nm LD laser].
In this paper, the absorption of Er3+, Yb3+ penta-phosphate noncrystalline (YELPP) was measured and the basic spectral parameters were calculated. Adopting the longitudinal-pump method with a domestic diode laser (LD), we achieved CW 1.5 microm chipped laser in China for the first time. The power of 1.5 microm laser was quite stable. The target of 1.5 microm laser reached the international level of early 1990s' in this field. In addition, the up-conversion luminescence was measured under the condition that 1.5 microm laser was either oscillating or not. The relationship between 1.5 microm chipped laser and up-conversion luminescence was analyzed initially.
English Abstract↗
[Direct upconversion sensitization luminescence of Tm(0.1) Yb (10.9) oxyfluoride vitroceramincs].
This paper studied the direct upconversion sensitization luminescence of Tm (0.1) Yb (10.9) oxyfluoride vitroceramics pumped by 966 nm diode laser for the first time. We found that there are both strong 477 nm three-photon upconversion fluorescence of 1G4 --> 3H6 transition and 799.5 nm two-photon upconversion fluorescence of 3H4 --> 3H6 transition as well as weak upconversion fluorescence of 1D2 --> 3H6, 1Dz --> 3F4,1G4 --> 3F4 and 3F3 --> 3H6 transitions at 361 nm, 449.5 nm, 647.0 nm and (679.5, 698.5 nm), respectively.
English Abstract↗
Protein inhibitor of neuronal nitric-oxide synthase, PIN, binds to a 17-amino acid residue fragment of the enzyme.
Neuronal nitric-oxide synthase (nNOS) is the primary nitric oxide (NO) regulator in neurons. The activity of the enzyme is inhibited by a protein inhibitor called PIN. We were able to purify large quantities of PIN overexpressed in bacterial cells. Analytical ultracentrifugation and chemical cross-linking studies showed that PIN exists as a monomer at low concentrations. The protein forms a high order aggregate at elevated concentrations. We have shown, using NMR spectroscopy, that the previously identified PIN-binding domain (PINB) of nNOS (residues 161-245) adopts a random coil structure in solution. By titrating 15N-labeled PINB with unlabeled PIN, the PIN-binding region of nNOS was precisely mapped to a 17-residue peptide fragment from Met-228 to His-244 of nNOS. NMR titration experiments also showed that PIN binds to nNOS with a 1:2 stoichiometry. A synthetic peptide corresponding to the identified PIN-binding region of nNOS was used to study the interaction between PIN and nNOS in detail. The functional implications of the results obtained from this study are discussed.
Amino Acid Sequence↗
[Effect of Ciwujia (Radix Acanthopanacis senticosus) preparation on exercise performance under constant endurance load for elderly].
The effect of Ciwujia (Radix Acanthopanacis senticosus) preparation on human exercise performance was investigated by using 13 healthy volunteers aged 50-57. Under constant endurance load with 450 kg.m/min (75 W), the respiratory quotient after taking Ciwujia preparation was reduced to 0.88 from 0.96, which implied that the utilization of lipid increased with 27.2% as energy fuel during exercise. Meanwhile, the heart rate was reduced with 8.7%, and O2 uptake per heart beat increased with 16.18%. All results indicated that the Ciwujia preparation could increase O2 uptake, spare the glycogen in muscle and improve the exercise endurance and work performance in human subjects.
Animals↗
Crystal structure and functional analysis of the HERG potassium channel N terminus: a eukaryotic PAS domain.
The HERG voltage-dependent K+ channel plays a role in cardiac electrical excitability, and when defective, it underlies one form of the long QT syndrome. We have determined the crystal structure of the HERG K+ channel N-terminal domain and studied its role as a modifier of gating using electrophysiological methods. The domain is similar in structure to a bacterial light sensor photoactive yellow protein and provides the first three-dimensional model of a eukaryotic PAS domain. Scanning mutagenesis of the domain surface has allowed the identification of a hydrophobic "hot spot" forming a putative interface with the body of the K+ channel to which it tightly binds. The presence of the domain attached to the channel slows the rate of deactivation. Given the roles of PAS domains in biology, we propose that the HERG N-terminal domain has a regulatory function.
Animals↗
Differential signaling cascade of MAP kinase and S6 kinase depends on 3',5'-monophosphate concentration in schwann cells: correlation to cellular differentiation and proliferation.
Schwann cells produce myelin in the peripheral nervous system (PNS) and play an important role in the maintenance of the normal function of PNS. Our previous studies have shown that derivatives of adenosine 3',5'-monophosphate (cAMP) can regulate the cell-fate (i.e., proliferation and differentiation into cell surface galactocerebroside-positive cells) depending on its concentration in vitro. Higher concentration of cAMP can induce the expression of cell surface galactocerebroside, while proliferation can be induced by lower concentration of cAMP. However, the detailed molecular mechanism of how the same second messenger yields different phenotypes of Schwann cells depending on its concentration remains to be elucidated. Here we show that low concentration of 8-bromo cAMP, a cell-permeable derivative of cAMP, activates S6 kinase activity with a short-lived activation of mitogen-activated protein kinase (MAPK), whereas high dose of the reagent activates S6 kinase much less than that of low dose with a small and prolonged activation of MAPK in Schwann cells. These data clearly demonstrated that a rise in the intracellular cAMP uses the MAPK-S6 kinase pathway as an intracellular sinaling cascade and different magnitude and duration of the activation of this pathway might underlie the different cellular fate depending on the intensity of the stimulation.
8-Bromo Cyclic Adenosine Monophosphate↗
Expression of glial cell line-derived neurotrophic factor and GDNFR-alpha mRNAs in human peripheral neuropathies.
The steady-state mRNA levels of glial cell line-derived neurotrophic factor (GDNF), GDNFR-alpha and RET were examined in various human peripheral neuropathies to determine the relationship with myelinated fiber pathology, and T cell and macrophage invasions in the diseased nerves. GDNF and GDNFR-alpha mRNA levels were elevated to variable extent in the diseased nerves, although they were not specific to the type of diseases. The increase of GDNFR-alpha mRNA levels was correlated with the extent of the nerves with axonal pathology, and was proportional to the extent of invasion of the nerves by T cells and macrophages. The GDNF mRNA levels were not related to axonal, demyelinating pathology, or inflammatory cell invasions. RET mRNA expression was not detected in normal nor diseased nerves. The GDNF and GDNFR-alpha expression in the diseased human nerves is regulated by an underlying pathology-related process, and could play a role in peripheral nerve repair.
Axons↗
Paracrine induction of stem cell renewal by LIF-deficient cells: a new ES cell regulatory pathway.
The propagation of pluripotential mouse embryonic stem (ES) cells is sustained by leukemia inhibitory factor (LIF) or related cytokines that act through a common receptor complex comprising the LIF receptor subunit (LIF-R) and the signal transducer gp130. However, the findings that embryos lacking LIF-R or gp130 can develop beyond gastrulation argue for the existence of an alternative pathway(s) governing the maintenance of pluripotency in vivo. In order to define those factors that contribute to self-renewal in ES cell cultures, we have generated ES cells in which both copies of the lif gene are deleted. These cells showed a significantly reduced capacity for regeneration of stem cell colonies when induced to differentiate, confirming that LIF is the major endogenous regulatory cytokine in ES cell cultures. However, self-renewal was not abolished and undifferentiated ES cell colonies were still obtained in the complete absence of LIF. A differentiated, LIF-deficient, parietal endoderm-like cell line was derived and shown to support ES cell propagation via production of a soluble, macromolecular, trypsin-sensitive activity. This activity, which we name ES cell renewal factor (ESRF), is distinct from members of the IL-6/LIF family because (i) it is effective on ES cells lacking LIF-R; (ii) it is not blocked by anti-gp130 neutralizing antibodies; and (iii) it acts without activation of STAT3. ES cells propagated clonally using ESRF alone can contribute fully to chimaeras and engender germline transmission. These findings establish that ES cell pluripotency can be sustained via a LIF-R/gp130-independent, STAT-3 independent, signaling pathway. Operation of this pathway in vivo could play an important role in the regulation of pluripotency in the epiblast and account for the viability of lifr -/- and gp130 -/- embryos.
Animals↗
Cloning and characterization of a novel human hepatocyte transcription factor, hB1F, which binds and activates enhancer II of hepatitis B virus.
Enhancer II (ENII) of hepatitis B virus (HBV) is one of the essential cis-elements for the transcriptional regulation of HBV gene expression. Its function is highly liver-specific, suggesting that liver-enriched transcriptional factors play critical roles in regulating the activity of ENII. In this report, a novel hepatocyte transcription factor, which binds specifically to the B1 region (AACGACCGACCTTGAG) within the major functional unit (B unit) of ENII, has been cloned from a human liver cDNA library by yeast one-hybrid screening, and demonstrated to trans-activate ENII via the B1 region. We named this factor hB1F, for human B1-binding factor. Amino acid analysis revealed this factor structurally belongs to nuclear receptor superfamily. Based on the sequence similarities, hB1F is characterized to be a novel human homolog of the orphan receptor fushi tarazu factor I (FTZ-F1). Using reverse transcription-polymerase chain reaction, a splicing isoform of hB1F (hB1F-2) was identified, which has an extra 46 amino acid residues in the A/B region. Examination of the tissue distribution has revealed an abundant 5.2-kilobase transcript of hB1F is present specifically in human pancreas and liver. Interestingly, an additional transcript of 3.8 kilobases was found to be present in hepatoma cells HepG2. Fluorescent in situ hybridization has mapped the gene locus of hB1F to the region q31-32.1 of human chromosome 1. Altogether, this study provides the first report that a novel human homolog of FTZ-F1 binds and regulates ENII of HBV. The potential roles of this FTZ-F1 homolog in tissue-specific gene regulation, in embryonic development, as well as in liver carcinogenesis are discussed.
Amino Acid Sequence↗
Molecular genetics of Wiedemann-Beckwith syndrome.
Wiedemann-Beckwith syndrome (WBS) is a heterogeneous overgrowth syndrome associated with malformations and an elevated risk of developing embryonal tumors. WBS is a multigenic disorder caused by dysregulation of imprinted growth regulatory genes within the 11p15 region. Elucidation of the genetic cause of WBS will provide important insights into the molecular and epigenetic changes associated with loss of normal growth control and cancer in this syndrome. Currently available protocols for diagnostic testing, patient monitoring and genetic counselling will evolve as our understanding of the molecular basis of WBS progresses.
Beckwith-Wiedemann Syndrome↗
Amino acid residues that control pH modulation of transport-associated current in mammalian serotonin transporters.
The rat and human serotonin transporters (rSERT and hSERT, respectively) were expressed in Xenopus oocytes and studied using site-directed mutagenesis, electrophysiological recordings, and [3H]5-HT uptake measurements. rSERT, but not hSERT, displayed increased transport-associated current at low pH. Chimeras and point mutations showed that, of the 52 nonidentical residues, a single residue at position 490 (threonine in rSERT and lysine in hSERT) governs this difference. Furthermore, potentiation required the glutamate residue at position 493. Cysteine substitution and alkylation experiments showed that residue 493 is extracellular. Cysteine at 493 increased, whereas aspartate decreased, the net charge movement per transported 5-HT molecule. The mutations at this region did not significantly affect other aspects of SERT function, including agonist-independent leakage current, voltage-dependent transient current, and H+ current. This region may therefore be part of an external gate required for rSERT function. The data and analyses show that, in the absence of detailed structural information, a gate-lumen-gate scheme is useful for interpreting results from mutations that alter functional properties of neurotransmitter transporters.
Acids↗
[Effects of different zinc level diets and heat exposure on the contents of Zn, Cu and Fe in brains of rats].
Forty-eight SD male rats were randomly divided into group A, B and C. Rats in each group were also divided into 2 parts. One part was used for heat exposure and the other was used for room temperature control. On the basis of AIN-93 m diet composition, group A, B and C zinc diets were prepared by adding or reducing zinc carbonate. Zinc contents of group A, B and C zinc diet per kilogram were 92.2 mg, 45.61 mg and 21.70 mg respectively. 14 days later the rats were exposed to high temperature (Tdb 40 degrees C, Twb 30.8 degrees C) for 3 hours. The Contents of Zn, Cu and Fe in hippocampus, cerebral cortex and cerebellum of rats were determined by atomic absorption spectrophotometer. The results revealed that 1. hyperthermal exposure could increase Cu content in rat hippocampus significantly, 2. after heat exposure, Cu content in hippocampus was higher than in cerebral cortex and cerebellum. Cu contents in cerebellum of room temperature control rat were higher than cerebral cortex and hippocampus, 3. intakes of different zinc level diets chiefly influenced content of Cu rat cerebellum and slightly affected iron content in it, 4. high, middle level zinc diet intake could reduce Cu content in heat-stressed rat cerebellum.
Animals↗
Direct spectroscopic detection of molecular dynamics and interactions of the calcium pump and phospholamban.
In order to test molecular models of cardiac calcium transport regulation, we have used spectroscopy to probe the structures, dynamics, and interactions of the Ca pump (Ca-ATPase) and phospholamban (PLB) in cardiac sarcoplasmic reticulum (SR) and in reconstituted membranes. Electron paramagnetic resonance (EPR) and phosphorescence of probes bound to the Ca pump show that the activity of the pump is quite sensitive to its oligomeric interactions. In cardiac SR, PLB aggregates and inhibits the pump, and both effects are reversed by PLB phosphorylation. Previous analyses of PLB's oligomeric state were only in detergent solutions, so we used EPR and fluorescence to determine the oligomeric structure of PLB in its native state in lipid bilayers. Wild-type PLB is primarily oligomeric in the membrane, while the mutant L37A-PLB is monomeric. For both proteins, phosphorylation shifts the dynamic monomer-oligomer equilibrium toward oligomers, and induces a similar structural change, as indicated by tyrosine fluorescence; yet L37A-PLB is more effective than wild-type PLB in inhibiting and aggregating the pump. Fluorescence energy transfer shows that the Ca pump increases the fraction of monomeric PLB, indicating that the pump preferentially binds monomeric PLB. These results support a reciprocal aggregation model for Ca pump regulation, in which the Ca pump is aggregated and inhibited by association with PLB monomers, and phosphorylation of PLB reverses these effects while decreasing the concentration of PLB monomers. To investigate the structure of the PLB pentamer in more detail, we measured the reactivities of cysteine residues in the transmembrane domain of PLB, and recorded EPR spectra of spin labels attached to these sites. These results support an atomic structural model, based on molecular dynamics simulations and mutagenesis studies, in which the PLB pentamer is stabilized by a leucine-isoleucine zipper within the transmembrane domain.
Animals↗
Generation of purified neural precursors from embryonic stem cells by lineage selection.
Mouse embryonic stem (ES) cells are non-transformed cell lines derived directly from the pluripotent founder tissue in the mouse embryo, the epiblast [1-3]. Aggregation of ES cells triggers the generation of a diverse array of cell types, including neuronal cells [4-7]. This capacity for multilineage differentiation is retained during genetic manipulation and clonal expansion [8]. In principle, therefore, ES cells provide an attractive system for the molecular and genetic dissection of developmental pathways in vitro. They are also a potential source of cells for transplantation studies. These prospects have been frustrated, however, by the disorganised and heterogeneous nature of development in culture. We have therefore developed a strategy for genetic selection of lineage-restricted precursors from differentiating populations. Here, we report that application of such lineage selection enables efficient purification of neuroepithelial progenitor cells that subsequently differentiate efficiently into neuronal networks in the absence of other cell types.
Animals↗
Phosphorylation-induced structural change in phospholamban and its mutants, detected by intrinsic fluorescence.
We have used intrinsic fluorescence to test the hypothesis that phosphorylation induces a conformational change in phospholamban (PLB), a regulatory protein in cardiac sarcoplasmic reticulum (SR). Phosphorylation of PLB, which relieves inhibition of the cardiac Ca-ATPase, has been shown to decrease the mobility of PLB in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In the present study, we found that this mobility shift depends on the acrylamide concentration in the gel, suggesting that phosphorylation increases the effective Stokes radius. To further characterize this structural change, we performed spectroscopic experiments under the conditions of SDS-PAGE. CD indicated that phosphorylation at Ser-16 does not change PLB's secondary structure significantly. However, the fluorescence of Tyr-6 in the cytoplasmic domain of PLB changed significantly upon PLB phosphorylation: phosphorylation increased the fluorescence quantum yield and decreased the quenching efficiency by acrylamide, suggesting a local structural change that decreases the solvent accessibility of Tyr-6. A point mutation (L37A) in the transmembrane domain, which disrupts PLB pentamers and produces monomers in SDS-PAGE and in lipid bilayers, showed similar phosphorylation effects on fluorescence, indicating that subunit interactions within PLB are not crucial for the observed conformational change in SDS. When PLB was reconstituted into dioleoylphosphatidylcholine (DOPC) lipid bilayers, similar phosphorylation effects in fluorescence were observed, suggesting that PLB behaves similarly in response to phosphorylation in both detergent and lipid environments. We conclude that phosphorylation induces a structural change within the PLB protomer that decreases the solvent accessibility of Tyr-6. The similarity of this structural change in monomers and pentamers is consistent with models in which the PLB monomer is sufficient for the phosphorylation-dependent regulation of the Ca-ATPase.
Acrylamide↗
Differential temporal expression of mRNAs for ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), interleukin-6 (IL-6), and their receptors (CNTFR alpha, LIFR beta, IL-6R alpha and gp130) in injured peripheral nerves.
The mRNA expression of the neuropoietic cytokines, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), interleukin-6 (IL-6), and their receptor components (CNTFRalpha, LIFRbeta, IL-6Ralpha and gp130) was examined in peripheral nerves after two different types of injury, crush and transection. The CNTF mRNA expression levels decreased after injury and remained low in the transected model, but recovered in 4 weeks in the crushed model. The LIF mRNA rapidly increased after damage and returned gradually to control levels. The IL-6 mRNA expression increased rapidly within 1 day after injury but dramatically decreased soon after. The CNTFRalpha mRNA levels gradually increased after nerve injury. LIFRbeta was expressed in the intact nerve and decreased slightly after injury. The IL-6Ralpha expression was observed faintly in the intact nerve and increased significantly soon after injury. There was also an increase in the expression of gp130. Although the temporal expression of these neuropoietic cytokines and receptors was extremely different, their pattern was similar between the crushed and transected models, except for CNTF. These results suggest that the expression of the ligands and receptors are differentially regulated after peripheral nerve injury, implying that each cytokine and signal transduction system has entirely distinctive functions in neuronal regeneration and repair.
Animals↗