Biomedical subjects

Xin Jiang

Publications and source records attributed to Xin Jiang.

At least 55 records · Page 3Linked to original sources

PubMed2005

Engulfment-regulated proteolysis of SpoIIQ: evidence that dual checkpoints control sigma activity.

During Bacillus subtilis sporulation, the engulfment checkpoint is thought to directly regulate late forespore transcription but to indirectly regulate late mother cell transcription, via the sigmaG-produced protease SpoIVB. We here demonstrate that SpoIIQ is subject to sigmaG-independent, but engulfment-dependent, proteolysis that depends on SpoIVB. Thus, SpoIVB produced before engulfment supports some SpoIVB-dependent events, suggesting that its activity or access to substrates must be regulated by engulfment. Furthermore, a mutation (bofA) that allows sigmaK to be active without sigmaG does not allow sigmaK activity in engulfment mutants, although the pro-sigmaK processing enzyme (SpoIVFB) is localized to the septum in engulfment mutants, suggesting that engulfment comprises a second checkpoint for sigmaK Finally, we find that SpoIIQ and another protein required for sigmaG activity (SpoIIIAH), which directly interact and assemble helical structures around the forespore, recruit the sigmaK-processing enzyme SpoIVFB to the forespore and these structures. We suggest that these foci serve a synapse-like role, allowing engulfment to simultaneously control both sigmaG and sigmaK, and integrating multiple checkpoints and signalling pathways.

Bacillus subtilis↗

PubMed2005

Localization of translocation complex components in Bacillus subtilis: enrichment of the signal recognition particle receptor at early sporulation septa.

We here demonstrate that in Bacillus subtilis, the signal recognition particle receptor, FtsY, transiently localizes to early sporulation septa, whereas three SecYEG translocase-associated membrane proteins (SecDF, SpoIIIJ, and YqjG) are uniformly distributed. These results suggest FtsY delivers secreted proteins to SecYEG at the septum, consistent with initial septal localization of forespore membrane proteins.

Bacillus subtilis↗

PubMed2005

Chromatin immunoprecipitation-based screen to identify functional genomic binding sites for sequence-specific transactivators.

In various human diseases, altered gene expression patterns are often the result of deregulated gene-specific transcription factor activity. To further understand disease on a molecular basis, the comprehensive analysis of transcription factor signaling networks is required. We developed an experimental approach, combining chromatin immunoprecipitation (ChIP) with a yeast-based assay, to screen the genome for transcription factor binding sites that link to transcriptionally regulated target genes. We used the tumor suppressor p53 to demonstrate the effectiveness of the method. Using primary and immortalized, nontransformed cultures of human mammary epithelial cells, we isolated over 100 genomic DNA fragments that contain novel p53 binding sites. This approach led to the identification and validation of novel p53 target genes involved in diverse signaling pathways, including growth factor signaling, protein kinase/phosphatase signaling, and RNA binding. Our results yield a more complete understanding of p53-regulated signaling pathways, and this approach could be applied to any number of transcription factors to further elucidate complex transcriptional networks.

Binding Sites↗

PubMed2005

[Effects of oxalate on acid phosphatase adsorption and its activity on soil colloids and minerals].

By a batch method, this paper studied the effects of different concentration and pH of oxalate, an important root exudate, on the adsorption of acid phosphatase and its activity on < 2 microm colloids of yellow brown soil and latosol, and on minerals goethite and kaolinite. The results showed that the acid phosphatase adsorption by goethite was less affected by the concentration of oxalate; while the adsorbed amount of this enzyme by the other test colloids and kaolinite was sharply decreased with the increasing oxalate concentration (0-5 mmol x L(-1)) first, and then gradually increased to the level equal to or less than the blank, which may be related to the coordination type of oxalate on soil colloids and minerals, and their surface charge change and dissolution. In the systems oxalate existed, the adsorbed amount of acid phosphatase by soil colloids and minerals decreased in order of goethite >> yellow brown soil > kaolinite > latosol. The pH value for the maximum adsorption of acid phosphatase was between the IEP of the enzyme and the PZC of test colloids and minerals. After the enzyme was immobilized on colloids and minerals, the pH of its maximum specific activity had no change, or shifted to a higher value.

Acid Phosphatase↗

PubMed2005

[Nitrate vertical transport and simulating model in saturated soils in typical region].

By simulating soil column in laboratory, the nitrate vertical transport characteristics in farmland soil in Fengqu region of Henan Province were studied. The results show that, under saturated soil condition, the different concentrations of nitrate (100 mg x L(-1) 200mg x L(-1)) had no obvious influence on the breakthrough curves (BTCs) of nitrate vertical transport. When the soil columns were eluted by nitrate solution containing co-existing cations (K+ and Ca2+), the BTCs of nitrate vertical transport in the topsoil(0 - 30cm) of yellow fluvo-aquic soil and aeolian sandy soil were very similar. However, the outflow time of nitrate in the middle and bottom soil layers in the yellow fluvo-aquic soil was significantly extended, when the soil columns were eluted by nitrate solution containing Ca2+. The longer the outflow time of nitrate transport out of soil column was, the evener and lower the peak of the BTCs was. The mathematical model, CXTFIT2.0, could be applied to accurately estimate nitrate leaching mass in the saturated soil with steady-state flow condition. The fitted BTCs were in good agreement with the observed BTCs, which had high correlative coefficients (0.8594 - 0.9978).

Models, Theoretical↗

PubMed2005

[Photoluminescence of tetragonal ZrO2 nanoparticles synthesized by severral methods].

Five methods for the preparation of stabilized ZrO2 nano-powders have been used. They are hydro-thermal method, alcohol-thermal method, sol-gel method, microwave-irradiation, and sonochemical method. XRD (X-ray diffraction) and PLspectra (Photoluminescence spectra) have been utilized to characterize these samples. Stable tetragonal nanometre ZrQ powders have been synthesized by these methods. From the XRD pattern, it is clear that the ZrO2 samples we obtained are crystal and distributed well. The PL pattern shows that the nano-ZrO2 powders can emit clear red and blue light when they are excited by the ultraviolet. The emphasis of this thesis is to discuss the ZrO2 emission nanocrystals' luminescent procedures.

Crystallization↗

PubMed2005

[Hysteretic characteristics of atrazine desorption from fluvo-aquic soil].

Kinetic batch experiments are carried out in order to investigate the effects of a wide range of atrazine initial concentrations and consecutive desorption time on the desorption characteristics of atrazine from fluvo-aquic soil. The results reveal that, atrazine concentrations in soil solution gradually decreased with desorption time increasing, whose relationship can be expressed with empirically exponential functions. After consecutive five steps (or 5 days), when atrazine initial concentrations increased from 50 microg x L(-1) to 2000 microg x L(-1), the average desorption percentages were 23.1%, 30.4%, 33.0%, 36.4% and 38.5%, respectively. The relationships between the amount of atrazine adsorbed by soil colloids and corresponding atrazine concentrations in soil solutions may be described through the traditional and time-dependent desorption isotherms. The obvious discrepancies in two families of both traditional and time-dependent desorption isotherms from adsorption isotherm, which retention time last for 168 hours before commencement of desorption, were indicative of hysteresis. Two sets of Freundlich parameters derived from both desorption isotherms can quantify the hysteresis between desorption and adsorption isotherms. However, hysteresis coefficient, omega, was applicable only for the traditional desorption isotherms, H and lamda applicable for both.

Adsorption↗

PubMed2005

[Degradation regulation of fenthion and chlorfenvinfos combined pollutants in red soil].

The degrading regulations of combined pollutants of chlorfenvinfos and fenthion in red soil were studied, in which soil incubation, gas chromatography with nitrogen-phosphorus detection for analysis are utilized. The main conclusions drawn are as follows: under combined pollution condition, the degrading amount of fenthion was significantly higher than that of fenthion alone in soil; under saturated soil humidity, the degrading amount of fenthion was less changed, while that of chlorfenvinfos was increased by 33.3% - 1250%. Soil drought made degradation amount of fenthion decreased a little, while made chlorfenvinfos increased significantly prior to the 21st day after addition of pesticide; nitrogen fertilizer application stimulated both fenthion and chlorfenvinfos degraded; the chemical degrading amount of fenthion in soil with organic matter eliminated was decreased by 22.4% - 30.8%, while that of chlorfenvinfos was increased 42.1% - 2370% at the earlier stage, and was decreased 11% - 17.3% at the later stage. Therefore, there are differences of degrading regulation between single pesticide pollutant and combined pesticide pollutants in soil, and the degradation of organophosphorus pesticides in combined pollutants are influenced with each other.

Biodegradation, Environmental↗

PubMed2004

Zipper-like interaction between proteins in adjacent daughter cells mediates protein localization.

Protein localization is crucial for cellular morphogenesis and intracellular signal transduction cascades. Here we describe an interaction between two membrane proteins expressed in different cells of the Bacillus subtilis sporangium, the mother cell protein SpoIIIAH and the forespore protein SpoIIQ. We used affinity chromatography, coimmunoprecipitation, and the yeast two-hybrid system to demonstrate that the extracellular domains of these proteins interact, tethering SpoIIIAH to the sporulation septum, and directing its assembly with SpoIIQ into helical arcs and foci around the forespore. We also demonstrate that this interaction can direct proteins made in the same cell to active division sites, as when SpoIIQ is made in the mother cell, it localizes to nascent septa in a SpoIIIAH-dependent manner. Both SpoIIIAH and SpoIIQ are necessary for activation of the second forespore-specific transcription factor (sigma(G)) after engulfment, and we propose that the SpoIIIAH-SpoIIQ complex contributes to a morphological checkpoint coupling sigma(G) activation to engulfment. In keeping with this hypothesis, SpoIIIAH localization depends on the first step of engulfment, septal thinning. The SpoIIQ-SpoIIIAH complex reaches from the mother cell cytoplasm to the forespore cytoplasm and is ideally positioned to govern the activity of engulfment-dependent transcription factors.

Bacillus subtilis↗

PubMed2004

Development of a method for screening short-lived proteins using green fluorescent protein.

We have developed a screening technology for the identification of short-lived proteins. A green fluorescent protein (GFP)-fusion cDNA library was generated for monitoring degradation kinetics. Cells expressing a subset of the GFP-cDNA expression library were screened to recover those in which the fluorescence signal diminished rapidly when protein synthesis was inhibited. Thirty clones that met the screening criteria were characterized individually. Twenty-three (73%) proved to have a half-life of 4 hours or less.

Cell Line↗

PubMed2004

Interactions between variable-charge soils and acidic solutions containing fluoride: an investigation using repetitive extractions.

The reaction between two variable-charge soils and acidic solutions containing F was investigated with a repetitive extraction method. When added F concentration was 10(-4) mol/L, F did not markedly enhance solution pH in the whole prolonged extractions, in comparison with F-free acidic solution extractions. Most of the added F was adsorbed on soil surfaces and Al-F complexes were the dominant F species in solution. With increasing extractions, the fraction of Al-F slightly increased, arising from dissolution and/or desorption of Al. In comparison with F-free acidic solution extractions, F-induced Al dissolution did not significantly increase Al release, probably because of the modest reactivity of metal-F surface complexes at terminal sites at low F loading. The gradual decrease in Al release in the following extractions was due to the gradual depletion of readily reactive Al-containing mineral phases. In contrast to the low F loading, at an F concentration of 10(-3) mol/L, the pH was enhanced dramatically in the initial extraction and a high pH was maintained in the following extractions. In the initial extraction, the increase in negative surface charges and solution pH seemingly depressed proton-induced Al dissolution and enhanced readsorption of some positively charged Al-F complexes, resulting in low amounts of Al and F in solution. In the following several extractions, F-induced Al dissolution and desorption of Al-F complexes substantially enhanced the amounts of Al and F, and the fraction of Al-F complexes in solution. Several interconnected mechanisms such as ligand exchange, the release of OH(-) ions from soluble hydroxylated Al groups, desorption of Al as Al-F complexes, and F-induced breakdown of soil minerals were responsible for the alteration in pH, Al release, and the fraction of Al-F complexes in the later extractions. A molecular-level interpretation is needed in order to address the different impacts of varying F concentration levels on soil chemistry and environments.

Journal Article↗

PubMed2004

5beta-reduced neuroactive steroids are novel voltage-dependent blockers of T-type Ca2+ channels in rat sensory neurons in vitro and potent peripheral analgesics in vivo.

T-type Ca(2+) channels are believed to play an important role in pain perception, and anesthetic steroids such as alphaxalone and allopregnanolone, which have a 5alpha-configuration at the steroid A, B ring fusion, are known to inhibit T-type Ca(2+) channels and cause analgesia in a thermal nociceptive model (Soc Neurosci Abstr 29:657.9, 2003). To define further the structure-activity relationships for steroid analgesia, we synthesized and examined a series of 5beta-reduced steroids for their ability to induce thermal antinociception in rats when injected locally into the peripheral receptive fields of the nociceptors and studied their effects on T-type Ca(2+) channel function in vitro. We found that most of the steroids completely blocked T-type Ca(2+) currents in vitro with IC(50) values at a holding potential of -90 mV ranging from 2.8 to 40 microM. T current blockade exhibited mild voltage-dependence, suggesting that 5beta-reduced neuroactive steroids stabilize inactive states of the channel. For the most potent steroids, we found that other voltage-gated currents were not significantly affected at concentrations that produce nearly maximal blockade of T currents. All tested compounds induced dose-dependent analgesia in thermal nociceptive testing; the most potent effect (ED(50), 30 ng/100 microl) obtained with a compound [(3beta,5beta,17beta)-3-hydroxyandrostane-17-carbonitrile] that was also the most effective blocker of T currents. Compared with previously studied 5alpha-reduced steroids, these 5beta-reduced steroids are more efficacious blockers of neuronal T-type Ca(2+) channels and are potentially useful as new experimental reagents for understanding the role of neuronal T-type Ca(2+) channels in peripheral pain pathways.

Analgesics↗

PubMed2004

Protein-DNA array-based identification of transcription factor activities regulated by interaction with the glucocorticoid receptor.

The glucocorticoid receptor (GR) regulates gene expression by binding specific sequence elements within the promoters of target genes or by cross-talk with other transcription factors (TFs). For some TFs, interaction with the GR results in alteration of DNA binding and transcriptional regulation. We used a protein-DNA array, a system that facilitates simultaneous profiling of the activities of multiple transcription factors, to systematically examine the potential cross-talk of GRalpha with 149 TFs. Using this array, we identified several TFs, including IRF, E47, and COUP-TF, whose DNA binding activities were modulated by GRalpha. We then confirmed these results with in vitro electrophoretic mobility shift assays and in vivo reporter assays. In this study, IRF and E47 were identified as participants in GRalpha cross-talk for the first time. This new finding expands our understanding of the functional role of GRalpha in the context of gene expression regulation.

Actins↗

PubMed2004

Tissue damage in the amyloidoses: Transthyretin monomers and nonnative oligomers are the major cytotoxic species in tissue culture.

The transthyretin (TTR) amyloidoses are human diseases in which the misfolded TTR protein aggregates in tissues with subsequent visceral, peripheral, and autonomic nerve dysfunction. Recent reports have stressed the importance of oligomeric intermediates as major cytotoxic species in various forms of amyloidogenesis. We have examined the cytotoxic effects of several quaternary structural states of wild-type and variant TTR proteins on cells of neural lineage. TTR amyloid fibrils and soluble aggregates >100 kDa were not toxic. Incubation of TTR under the conditions of the cell assay and analysis by size-exclusion chromatography and SDS/PAGE reveal that monomeric TTR or relatively small, rapidly formed aggregates of a maximum size of six subunits were the major cytotoxic species. Small molecules that stabilize the native tetrameric state were shown to prevent toxicity. The studies are consistent with a model in which the misfolded TTR monomer rapidly aggregates to form transient low molecular mass assemblies (<100 kDa) that are highly cytotoxic in tissue culture.

Amyloidosis↗

PubMed2004

Selective antagonism of 5alpha-reduced neurosteroid effects at GABA(A) receptors.

Although neurosteroids have rapid effects on GABA(A) receptors, study of steroid actions at GABA receptors has been hampered by a lack of pharmacological antagonists. In this study, we report the synthesis and characterization of a steroid analog, (3alpha,5alpha)-17-phenylandrost-16-en-3-ol (17PA), that selectively antagonized neurosteroid potentiation of GABA responses. We examined 17PA using the alpha1beta2gamma2 subunit combination expressed in Xenopus laevis oocytes. 17PA had little or no effect on baseline GABA responses but antagonized both the response augmentation and the direct gating of GABA receptors by 5alpha-reduced potentiating steroids. The effect was selective for 5alpha-reduced potentiating steroids; 5beta-reduced potentiators were only weakly affected. Likewise, 17PA did not affect barbiturate and benzodiazepine potentiation. 17PA acted primarily by shifting the concentration response for steroid potentiation to the right, suggesting the possibility of a competitive component to the antagonism. 17PA also antagonized 5alpha-reduced steroid potentiation and gating in hippocampal neurons and inhibited anesthetic actions in X. laevis tadpoles. Analogous to benzodiazepine site antagonists, the development of neurosteroid antagonists may help clarify the role of GABA-potentiating neurosteroids in health and disease.

Androstenols↗

PubMed2004

Separation of chlorinated hydrocarbons and organophosphorus, pyrethroid pesticides by silicagel fractionation chromatography and their simultaneous determination by GC-MS.

A silicagel fractionation procedure for environmental sample extracts, which separates chlorinated hydrocarbons (CHCs) and organophosphorus, pyrethroid pesticides into two groups for subsequent instrumental analysis, was developed in this study. This method was achieved by optimizing the fraction cut-off volume of elution and different solvents. Using fully activated silica gel and cut-off CHCs collection after 10 ml 10% dichloromethane (DCM) in n-hexane passing through the column resulted in satisfactory separation of CHCs and organophosphorus, pyrethroid pesticides. This procedure had a higher reliability for CHCs than for organophosphorus, pyrethroid pesticides, because there is a relatively reliable recovery for CHCs. This approach is less expensive due to reducing sample pre-treatment time and solvent consumption.

Chemical Fractionation↗

PubMed2004

[Effect of acetic acid on adsorption of acid phosphatase by some soil colloids and clay minerals].

This paper studied the effect of acetic acid with different concentrations and pH values on the adsorption of acid phosphatase by some soil colloids and clay minerals (SCCM). The results showed that the pH values for the maximum adsorption of the enzyme were between the IEP of the enzyme and the PZC of SCCM. In the acetic acid systems, the amount of the enzyme adsorbed by SCCM was in the order of goethite >> yellow brown soil > latosol > kaolinite > delta-MnO2. A remarkable influence of acetic acid concentration on the adsorption amount and the binding energy of the enzyme was observed. With the increase of the concentration from 0 to 200 mmol.L-1 in the system, acetic acid exhibited an enhanced effect, followed by an inhibition action on the adsorption of the enzyme on SCCM. The changes of the binding energy (K value) for the enzyme on SCCM were on the contrary to those of the maximum adsorption. The possible mechanisms for the influence of acetic acid on the adsorption of enzyme by SCCM were also discussed.

Acetic Acid↗

PubMed2004

[Effects of lanthanum on root membrane permeability and nutrient contents in root exudate of rice].

This study showed that when lanthanum was in lower concentration (< or = 50 microg x ml(-1)), the membrane permeability of rice root was stabilized by decreasing the electrolyte exosmosis, and the contents of K+, Ca2+, P and H+ in root exudate were lower than the control; while the concentration of La3+ was in the range of 100-400 microg x ml(-1), the electrolyte exosmosis was reduced in the first 6 hours, and then significantly increased. When the concentration of La3+ was over 500 microg x ml(-1), the electrolyte exosmosis was continuously enlarged because of the destruction of the membrane. Under this condition, K+, Ca2+, P and H+ in root exudate were higher than the control. It could be concluded that the concentration of 50 microg x ml(-1) La3+ was safe to rice growing.

Calcium↗