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Biomedical subjects

Nan Jiang

Publications and source records attributed to Nan Jiang.

At least 19 recordsLinked to original sources
PubMed2006

Electrostatic field-adapted molecular fractionation with conjugated caps for energy calculations of charged biomolecules.

An electrostatic field-adapted molecular fractionation with conjugated caps (EFA-MFCC) approach is implemented for treating macromolecules with several charge centers. The molecular fragmentation is performed in an "electrostatic field," which is described by putting point charges on charge centers, directly affecting the Hamiltonians of both fragments and conjugated caps. So the present method does not need truncation during the calculation of electrostatic interactions. Our test calculations on a series of charged model systems and biological macromolecules using the HF and B3LYP methods have demonstrated that this approach is capable of describing the electronic structure with accuracy comparable to other fragment-based methods. The EFA-MFCC approach is an alternative way for predicting the total energies of charged macromolecules with acyclic, loop, and intersectional loop structures and interaction energies between two molecules.

Electromagnetic Fields↗
PubMed2006

[Effect of guizhi decoction on PKA and PKC activities of hypothalamus in fever rats].

OBJECTIVE: To investigate the changes of the activity of both protein kinase A and C and the mechanisms of antipyretic action of Guizhi decoction. METHOD: The fever responses were observed after combination injection of H-89 (a selective inhibitor of PKA) and calphostin C (a selective inhibitor of PKC), and oral pretreatment of Guizhi decoction in fever rats induced by an intra-cerebroventricular (icv) injection of an EP3 agonist, and both PKA and PKC activity in hypothalamus were measured in rats pretreated with Guizhi decoction and vehicle using isotopic tracing assay. RESULT: The rise in rat body temperature was inhibited by H-89, Calphostin C, and Guizhi decoction, moreover, pretreatment with Guizhi decoction reduced PKA activity obviously. PKC activity in model rats exhibited a tendency to drop compared with that of control group, Oral administration of Guizhi decoction in large dose inhibited the response significantly, while the low dose of Guzhi decoction has no effect on PKC. CONCLUSION: Both PKA and PKC may participate in the mechanism of fever induction by EP3 agonist. The decrease of PKA and PKC may contribute to the antipyretic action of Guizhi decoction, some isoenzyme of PKC may play a role in the fever production.

Analgesics, Non-Narcotic↗
PubMed2005

Actions of brain-derived neurotrophic factor on spinal nociceptive transmission during inflammation in the rat.

The aim of the current study was to investigate whether, and if so how, brain-derived neurotrophic factor (BDNF) acts to develop the spinal sensitization underlying inflammation-induced hyperalgesia. In spinal cord slice preparations from rats with inflammation induced by complete Freund's adjuvant (CFA), BDNF, but not nerve growth factor (NGF) or neurotrophin-3 (NT-3), acted presynaptically to increase the frequency of excitatory miniature EPSCs in substantia gelatinosa (SG) neurones of the CFA-treated, but not untreated rats, through activation of lidocaine (lignocaine)-sensitive, TTX-resistant Na+ channels. This effect was observed in the spinal cord slices of the CFA-treated rat only 2-4 days after the CFA injection. On the other hand, the number of monosynaptic Abeta afferent inputs to the SG significantly increased 1 week after the onset of the inflammation, and this increase was significantly suppressed by treatment with anti-BDNF antiserum administered 1 day before and just after the CFA injection. In addition, the treatment with anti-BDNF antiserum significantly attenuated the CFA-induced hyperalgesia and/or allodynia. These findings, taken together, suggest that BDNF, which is considered to be released from the sensitized primary afferents, increases the excitability of SG neurones through its action on the presynaptic terminals. BDNF may thereafter induce monosynaptic Abeta afferents to the SG, thereby developing hyperalgesia and/or allodynia during inflammation.

Animals↗
PubMed2005

Interpretation of Oxygen K pre-edge peak in complex oxides.

A controversial pre-edge peak has often been observed at the O K-edge in absorption spectra from complex oxides. We study this feature in both K(2)O-SiO(2) glass and MgAl(2)O(4) spinel crystals. Our time-resolved energy-loss spectroscopy (EELS) results indicate that the pre-edge peak is due to radiation damage, rather than from any intrinsic feature of the material. It is assigned to the pi* peak due to the O-O interaction.

Journal Article↗
PubMed2005

Experimental and theoretical improvements on understanding of the O K-edge of TeO2.

Using an electron monochromator attached to an electron microscope, high energy-resolution electron energy-loss spectra collected from TeO2 have revealed new features in the Oxygen K-edge. Using density-functional theory in the local density and the generalized gradient approximation, we find that core-hole strength of 1.3 gives an excellent fit to our high-resolution experimental data. This indicates that screening is not weak in this oxide, as normally assumed, and that neither the ground state nor a full core-hole model is adequate in quantitative reproduction of the O K-edge in the TeO2 system.

Journal Article↗
PubMed2005

Aggregation behavior of hexadecyltrimethylammonium surfactants with various counterions in aqueous solution.

Both thermodynamic and microenvironmental properties of the micelles for a series of cationic surfactants hexadecyltrimethylammonium (C16TAX) with different counterions, F-, Cl-, Br-, NO3-, and (1/2)SO4(2-), have been studied. Critical micelle concentration (CMC), degree of micelle ionization (alpha), and enthalpy of micellization (DeltaH(mic)) have been obtained by conductivity measurements and isothermal titration microcalorimetry. Both the CMC and the alpha increase in the order SO4(2-) < NO3- < Br- < Cl- < F-, consistent with a decrease in binding of counterion, except for the divalent anion sulfate. DeltaH(mic) becomes less negative through the sequence NO3- < Br- < Cl- < F- < SO4(2-), and even becomes positive for the divalent sulfate. The special behavior of sulfate is associated with both its divalency and its degree of dehydration. Gibbs free energies of micellization (DeltaG(mic)) and entropies of micellization (DeltaS(mic)) have been calculated from the values of DeltaH(mic), CMC, and alpha and can be rationalized in terms of the Hofmeister series. The variations in DeltaH(mic) and DeltaS(mic) have been compared with those for the corresponding series of gemini surfactants. Electron spin resonance has been used to assess the micropolarity and the microviscosity of the micelles. The results show that the microenvironment of the spin probe in the C16TAX surfactant micelles depends strongly on the binding of the counterion.

Journal Article↗
PubMed2005

Microcalorimetric study on the interaction of dissymmetric gemini surfactants with DNA.

The interaction of a series of dissymmetric gemini surfactants, [C(m)H(2m+1)(CH(3))(2)N(CH(2))(6)N(CH(3))(2)C(n)H(2n+1)]Br(2) (designated as C(m)C(6)C(n)Br(2), with constant m+n=24, and m=12, 14, 16, and 18) with DNA in 10 mM NaCl solution has been investigated by isothermal titration microcalorimetry (ITC). The curves for titration of the surfactants into DNA solution show noticeable differences from those into 10 mM NaCl solution without DNA. It is attributed to the interaction between DNA and surfactants. The critical aggregation concentration (CAC), the saturation concentration (C(2)), and the thermodynamic parameters for the aggregation and interaction processes were obtained from the calorimetric titration curves. The results show that the dissymmetry degree (m/n) has a marked effect on the interaction of the C(m)C(6)C(n)Br(2) surfactants with DNA. The CAC and C(2) tend to become smaller with increased m/n. The enthalpy change (DeltaH(agg)) and the Gibbs free energy change (DeltaG(agg)) for aggregation become more negative down the series, indicating that the hydrophobic interaction between the hydrophobic chains of the surfactant molecules increases and the aggregation process is more spontaneous with increased m/n. The entropy changes of aggregation (DeltaS(agg)) are all positive and TDeltaS(agg) is much larger than |DeltaH(agg)|, revealing that the aggregation process is mainly entropy-driven. However, the calculated Gibbs free energy (DeltaG(DS)) for the interaction between the gemini surfactants and DNA becomes less negative with increased m/n, which reveals that the interaction between the gemini surfactants and DNA tends to be weaker with increased m/n. This is induced by the disruption of the chain-chain hydrophobic interaction between the surfactant molecules at higher m/n, where the entropy change DeltaS(DS) for the interaction process tends to be an unfavorable factor. In addition, the DNA concentration also has a remarkable influence on the interaction.

Binding, Competitive↗
PubMed2005

Tobacco smoke dysregulates endothelial vasoregulatory transcripts in vivo.

We hypothesized that human smoking and its deleterious effects on endothelial function can be modeled by exposure of mice to tobacco smoke, and further that these changes would be reflected in gene regulation in vascular endothelium. We used for these studies a mouse strain that expresses green fluorescent protein under the control of an endothelial-specific promoter, Tie-2. Mice were exposed to sidestream smoke from reference cigarettes at 34 mg total suspended particulates/m3. After exposure for 5 days/wk for 1 and 6 wk, aortas were pooled from treatment and control groups. Endothelial cells were rapidly isolated by collagenase treatment followed by fluorescent activated cell sorting to yield populations of >95% purity. RNA isolated from >500 endothelial cells was amplified and analyzed on deeply representative long oligo microarrays. Transcripts dysregulated by >2.5-fold were confirmed by real-time PCR and selected proteins by immunofluorescent localization. In the endothelial cells, the observed more than threefold upregulation of complement factor H (Cfh), calcitonin receptor-like (Calcr1), and soluble epoxide hydrolase (Epxh2) may play a role in hypertensive responses of the vasculature to smoking. We have identified gene regulation in vivo in vascular endothelium that potentially underlies hypertensive responses to tobacco smoke.

Animals↗
PubMed2005

Transgenic mice that express Cre recombinase in hypertrophic chondrocytes.

In order to investigate the physiological control of hypertrophic chondrocytes which present the terminally differentiated form of chondrocytes, we generated a mouse line expressing the Cre recombinase under the control of the mouse type X collagen (Col10a1) promoter. In situ hybridization analysis demonstrated the expression of Col10a1-Cre transgene in hypertrophic chondrocytes of femur at postnatal day 2 (P2). In order to test the excision activity of the Cre recombinase, the Col10a1-Cre transgenic line was crossed with the mouse strain carrying the Smad4 conditional alleles (Smad4co/co) and the reporter line ROSA26. Multiple tissue PCR of Col10a1-Cre;Smad4co/+ mice revealed the restricted Cre activity in tissues containing hypertrophic chondrocytes. LacZ staining revealed that the Cre activity was observed in the cartilage primordia of ribs at E14.5 and only detected in the lower hypertrophic region of ribs at P1. These data suggest that the Col10a1-Cre mouse line described here could be used to achieve conditional gene targeting in hypertrophic chondrocytes.

Animals↗
PubMed2005

Identification of human dopamine D1-like receptor agonist using a cell-based functional assay.

AIM: To establish a cell-based assay to screen human dopamine D1 and D5 receptor agonists against compounds from a natural product compound library. METHODS: Synthetic responsive elements 6 cAMP response elements (CRE) and a mini promoter containing a TATA box were inserted into the pGL3 basic vector to generate the reporter gene construct pCRE/TA/Luci. CHO cells were co-transfected with the reporter gene construct and human D1 or D5 receptor cDNA in mammalian expression vectors. Stable cell lines were established for agonist screening. A natural product compound library from over 300 herbs has been established. The extracts from these herbs were used for human D1 and D5 receptor agonist screenings. RESULTS: A number of extracts were identified that activated both D1 and D5 receptors. One of the herb extracts, SBG492, demonstrated distinct pharmacological characteristics with human D1 and D5 receptors. The EC(50) values of SBG492 were 342.7 microg/mL for the D1 receptor and 31.7 microg/mL for the D5 receptor. CONCLUSION: We have established a cell-based assay for high-throughput drug screening to identify D1-like receptor agonists from natural products. Several extracts that can active D1-like receptors were discovered. These compounds could be useful tools for studies on the functions of these receptors in the brain and could potentially be developed into therapeutic drugs for the treatment of central nervous system diseases.

Animals↗
PubMed2004

In vivo transcriptional response of cardiac endothelium to lipopolysaccharide.

OBJECTIVE: Vascular endothelial cells must integrate stimuli from multiple sources, including plasma, leukocytes, and neighboring components of the vessel. These stimuli are difficult to recapitulate in vitro. We have developed a method to examine the in vivo regulation of gene expression in endothelial cells and have applied it to a model of sepsis. METHODS AND RESULTS: We used fluorescent-activated cell sorting to isolate highly purified endothelial cells from the hearts of transgenic mice that express green fluorescent protein driven by the endothelial-specific promoter Tie2. We treated these mice with intraperitoneal lipopolysaccharide and identified those genes within cardiac endothelium that were >3-fold dysregulated 4 and 24 hours later by microarray analysis. These findings were confirmed by real-time polymerase chain reaction and compared with in vitro regulation in a murine endothelial cell line. CONCLUSIONS: The in vivo regulation was distinct and, in general, more robust than that seen in vitro. We identified endothelial-expressed genes not previously recognized to be regulated in response to lipopolysaccharide. This approach provides insight into the cardiac-specific responses of the endothelium that contribute to the specific responses of the heart to sepsis, and can be generalized to the exploration of endothelial responses in any organ.

Acute-Phase Proteins↗
PubMed2004

Cellular and molecular regulation of skeletal muscle side population cells.

Muscle progenitor cells (satellite cells) function in the maintenance and repair of adult skeletal muscle. Side population (SP) cells are enriched in repopulating activity and also reside in adult skeletal muscle. In this study, we observed that Abcg2 is a determinant of the SP cell phenotype. Using reverse transcription polymerase chain reaction and immunohistochemical techniques, we localized Abcg2-expressing cells in the interstitium and in close approximation to the vasculature of adult skeletal muscle. Muscle SP cells are able to differentiate into myotubes and increase in number after cardiotoxin-induced muscle injury. Similar to myogenic progenitor cells, muscle SP cells express Foxk1 and are decreased in number in Foxk1 mutant skeletal muscle. Using emerging technologies, we examine the molecular signature of muscle SP cells from normal, injured, and Foxk1 mutant skeletal muscle to define common and distinct molecular programs. We propose that muscle SP cells are progenitor cells that participate in repair and regeneration of adult skeletal muscle.

ATP Binding Cassette Transporter, Subfamily G, Mem↗