Biomedical subjects

L Jia

Publications and source records attributed to L Jia.

At least 19 recordsLinked to original sources

PubMed2006

Quantitative determination of apogossypol, a pro-apoptotic analog of gossypol, in mouse plasma using LC/MS/MS.

A simple and selective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method based on internal standard quantitation using apigenin as the internal standard has been developed and validated for the analysis of the gossypol analog apogossypol, a pro-apoptotic compound, in mouse plasma. The methodology involves protein precipitation of plasma samples followed by LC/MS/MS analysis. Ascorbic acid was added to the spiking solutions and plasma samples to stabilize the easily oxidized compound. Separation of apogossypol and the internal standard from the plasma matrix was achieved using a C18 column with a gradient elution profile consisting of 5mM ammonium acetate and methanol. The validated range of the method extended from 10 to 2000 ng/mL with accuracies of 85-115% and precision of <15%. The average recovery of apogossypol at three concentrations (50, 200 and 1000 ng/mL) assayed in triplicate using this methodology was determined to be 90.8+/-12.9%. Recovery for the internal standard (apigenin) at a concentration of 500 ng/mL was found to be 99.9+/-6.41%. Apogossypol concentrations of 50 ng/mL and above were found to be stable in extracted plasma for 24h when stored at 25 degrees C. This method has been applied to the determination of apogossypol concentrations in plasma collected from mice given an IV dose of apogossypol.

Animals↗

PubMed2006

Increased risk of chronic obstructive pulmonary diseases in coke oven workers: interaction between occupational exposure and smoking.

BACKGROUND: Coke oven workers are regularly exposed to coke oven emissions (COE) and may be at risk of developing lung diseases. There is limited evidence for the link between exposure to COE and chronic obstructive pulmonary diseases (COPD). The aim of this study was to explore the dose-response relationship between COE exposure and COPD and to assess the interaction with cigarette smoking. METHODS: Seven hundred and twelve coke oven workers and 211 controls were investigated in southern China. Benzene soluble fraction (BSF) concentrations as a surrogate of COE were measured in representative personal samples and the individual cumulative COE exposure level was quantitatively estimated. Detailed information on smoking habits and respiratory symptoms was collected and spirometric tests were performed. RESULTS: The mean BSF levels at the top of two coking plants were 743.8 and 190.5 microg/m3, respectively, which exceed the OSHA standard (150 microg/m3). After adjusting for cigarette smoking and other risk factors, there was a significant dose-dependent reduction in lung function and increased risks of chronic cough/phlegm and COPD in coke oven workers. The odds ratio for COPD was 5.80 (95% confidence interval 3.13 to 10.76) for high level cumulative COE exposure (> or =1714.0 microg/m3-years) compared with controls. The interaction between COE exposure and smoking in COPD was significant. The risk of COPD in those with the highest cumulative exposure to COE and cigarette smoking was 58-fold compared with non-smokers not exposed to COE. CONCLUSION: Long term exposure to COE increases the risk of an interaction between COPD and cigarette smoking.

Adult↗

PubMed2005

Effects of jasmonate-induced defenses on root-knot nematode infection of resistant and susceptible tomato cultivars.

Jasmonates, such as jasmonic acid (JA), are plant-signaling compounds that trigger induced resistance against certain pathogens and a broad range of arthropod herbivores. One goal of this study was to determine the effects of JA-dependent defenses in tomato on root-knot nematodes. Another was to determine if the artificial induction of these defenses could enhance nematode control on plants that carry Mi-1.2, a nematode resistance gene that is present in many tomato cultivars. At moderate soil temperatures, Mi-1.2 can effectively suppress reproduction of most isolates of the common root-knot nematode species Meloidogyne javanica, M. incognita, and M. arenaria. Mi-mediated resistance has its limitations, however. Mi-1.2 is reported to lose its effectiveness at soil temperatures above 28 degrees C, and certain virulent nematode isolates can overcome resistance even at moderate soil temperatures. This study used a foliar application of JA to activate induced resistance in two near-isogenic lines of tomato (Lycopersicon esculentum) with and without Mi-1.2, and evaluated the effects of induced resistance at moderate soil temperatures on one avirulent nematode isolate (M. javanica isolate VW4) and two virulent isolates (M. javanica isolate VW5 and M. incognita isolate 557R). In addition, the effects of induced resistance on avirulent nematode performance were examined at a high temperature (32 degrees C). The results indicate that JA application induces a systemic defense response that reduces avirulent nematode reproduction on susceptible tomato plants. Furthermore, JA-dependent defenses proved to be heat-stable, whereas the effects of Mi-mediated resistance were reduced but not eliminated at 32 degrees C. JA treatment enhanced Mi-mediated resistance at high temperature, but did not suppress either of the virulent nematode isolates tested.

Animals↗

PubMed2005

The role of protein kinase A pathway and cAMP responsive element-binding protein in androgen receptor-mediated transcription at the prostate-specific antigen locus.

Androgen-independent prostate cancer is a lethal form of the disease that is marked by metastasis and rapid proliferation in its final stages. As no effective therapy for this aggressive tumor currently exists, it is imperative to elucidate and target the mechanisms involved in the progression to androgen independence. Accumulating evidence indicates that aberrant activation of androgen receptor (AR) via signal transduction pathways, AR gene mutation and/or amplification, and/or coregulator alterations may contribute to the progression of prostate cancer. In the present study, the effects of protein kinase A (PKA) signaling and its downstream factors on AR activity at the prostate-specific antigen (PSA) gene were tested. Activation of PKA by forskolin resulted in enhanced androgen-induced expression of the PSA gene, an effect that was blocked by the AR antagonist, bicalutamide. Interestingly, when either p300 or CBP was overexpressed, PKA activation was sufficient to stimulate PSA promoter-driven transcription in the absence of androgen, which was not inhibited by bicalutamide. PKA activation did not significantly alter AR protein levels but significantly increased the phosphorylated form of its downstream effector, cAMP responsive element-binding protein (CREB) in the presence of androgen. Furthermore, chromatin immunoprecipitation showed that the combination of androgen and forskolin increased phosphorylated CREB occupancy, which was accompanied by histone acetylation, at the putative cAMP responsive element located in the 5' upstream regulatory region of the PSA gene. Remarkably, mammalian two-hybrid assay indicated that p300/CBP may bridge the interaction between AR and CREB, suggesting a novel enhanceosomal cooperation. These results demonstrate an intriguing interplay between a signal transduction pathway, coactivator overexpression and AR signaling as a possible combined mechanism of progression to androgen-independent prostate cancer.

Acetylation↗

PubMed2004

Axial patterning of C. elegans male sensilla identities by selector genes.

The fan and rays of the C. elegans male tail constitute a compound sensory organ essential for mating. Within this organ, the individual sensilla, known as rays, have unique identities. We show that ray identities are patterned by a selector gene mechanism in a manner similar to other serially homologous axial structures. One selector gene that promotes the identities of a subset of the rays is the Hox gene egl-5. Within EGL-5-expressing rays, further patterning is provided by a Pax-6 homolog and a signal of the TGFbeta family. These genes and pathway coordinately specify multiple ray properties affecting all three terminal ray cell types. These properties include complex patterns of FMRFamide-like (FaRP) neuropeptides, serotonin (5HT) and dopamine expression, and ray morphology. Differences in these differentiated characteristics give each sensillum a unique identity and potentially endow the compound ray organ with a higher-order information gathering capacity.

Animals↗

PubMed2004

Acquired and R-gene-mediated resistance against the potato aphid in tomato.

We examined the effects of three forms of host plant resistance in tomato, Lycopersicon esculentum, on the potato aphid, Macrosiphum euphorbiae. Mi-1.2, a resistance gene (R-gene) in tomato that deters aphid feeding, reduced the population growth of both potato aphid isolates tested, although it appeared to have a greater impact on isolate WU11 than on isolate WU12. The results suggest that there may be quantitative differences in virulence between these two aphid isolates. We also examined two distinct forms of acquired resistance in tomato, jasmonic acid (JA)-dependent and salicylic acid (SA)-dependent induced defenses. Exogenous foliar application of JA triggered expression of a JA-inducible proteinase inhibitor in tomato cultivars with and without Mi-1.2, although the effects of treatment on aphid performance differed between these cultivars. JA-treatment reduced aphid population growth on a susceptible tomato cultivar that lacks Mi-1.2, but did not significantly enhance or inhibit aphid control on a near-isogenic resistant tomato cultivar that carries this gene. Foliar application of an SA analog, benzothiadiazole (BTH), was used to induce SA-dependent defenses. BTH treatment reduced the population growth of both aphid isolates on a susceptible tomato cultivar, and also enhanced aphid control on a resistant cultivar. The results indicate that both SA- and JA-dependent acquired resistance in tomato have a direct negative effect on a phloem-feeding insect. Furthermore, this study demonstrates that acquired resistance and R-gene-mediated resistance can interact for enhanced suppression of insect herbivores.

Animals↗

PubMed2004

Increase in the ratio of mitochondrial Bax/Bcl-XL induces Bax activation in human leukemic K562 cell line.

The p53- and Bcl-2-negative leukemic K562 cell line showed resistant to DNA damage-induced Bax activation and apoptosis. The constitutive balanced ratio of Bax/Bcl-XL in K562 mitochondria allowed the formation of active Bax and cytochrome c release from mitochondria in the presence of a BH3-only protein, tBid, in a cell-free system. Bax transfection led to Bax undergoing a conformational change, translocation to mitochondria and homo-oligomerization but not apoptosis in the K562 cell line. After treatment with UV light, while Bcl-XL but not Bax translocated to mitochondria in K562, both Bax and Bcl-XL translocated to mitochondria in the Bax stable transfectant K/Bax cells. The increased ratio of Bax/Bcl-XL in K/Bax mitochondria led to an increased conformationally changed Bax, formation of the homo-multimer of Bax-Bax, and a reduced hetero-dimerization of Bax-Bcl-XL. Increased proportion of active Bax was accompanied with increased percentage of apoptosis. We therefore demonstrate that direct increase in the ratio of mitochondrial Bax/Bcl-XL can induce Bax activation in the p53- and Bcl-2-negative leukemic cells. Increased Bcl-XL translocation and failure in Bax translocation from cytosol to mitochondria play important roles in preventing Bax activation.

Apoptosis↗

PubMed2003

Potential mechanisms of leukemia cell resistance to TRAIL-induced apopotosis.

There are many factors contributing to the resistance to TRAIL (Tumor necrosis factor-related apoptosis-inducing ligand)-induced apoptosis. However, it is not clear whether the mechanism of resistance to TRAIL is constitutive or inductive. Therefore, the purpose of this study was to investigate the resistant mechanisms to TRAIL at different levels in the apoptotic pathway. The human T-lymphoblastic leukemic CEM cell line showed more resistant to TRAIL-induced apoptosis compared with the human chronic myeloid leukemic K562 cell line. Lower level of constitutive caspase-8 expression in the CEM cell line led to a poor response to both TRAIL-induced activation of caspase-3 and reduction in the mitochondrial membrane potential (DeltaPsim). There was no significant difference in the constitutive levels of NF-kappaB in CEM and K562 cell lines. However, CEM cells showed a faster response to TRAIL-induced NF-kappaB activation than K562 cells. TRAIL-induced regulation of Bcl-2 family of proteins included an up-regulation in Bcl-2/Bcl-XL and a down-regulation in Bax. IAPs, such as XIAP, cIAP-1, cIAP-2 and Survivin were all up-regulated during the treatment with TRAIL. In summary, our data suggest that the leukemic cells resistance to TRAIL-induced apoptosis might be due to the deficiency in the constitutive caspase-8 expression. Development of potential resistance to apoptosis by TRAIL can occur in both TRAIL-resistant and TRAIL-sensitive leukemic cells.

Apoptosis↗

PubMed2002

The enhancement of hydration of fluidized bed combustion ash by sonication.

The use of limestone to control SO2 emissions in fluidized bed combustors (FBC) results in high CaO content in the ashes. This presents challenges for their disposal including significant exothermic behavior and uncontrolled expansion in the landfill. Hydration of the ashes is required to convert the CaO, but the current two-step hydration process is not very effective. In the present work a new technique using ultrasound to promote the hydration was examined. Initial work was done using an ultrasonic bath and subsequently an ultrasonic probe. Hydration levels greater than 80% in 20-40 min with amplitudes of 40% or more were achieved with residues containing high levels of CaO. This is about twice what can be achieved using conventional hydration technique. Similar results were obtained using FBC ashes from four utility/industrial scale and one pilot plant scale FBC units. The mechanism for the promotion of hydration bythe ultrasound is also explored.

Air Pollutants↗

PubMed2001

Liquid chromatography-mass spectrometry assay of a thiadiazole derivative in mice: application to pharmacokinetic studies.

Modern atmospheric pressure ionization (API) ion-trap mass spectrometry in connection with fast chromatographic separations using a short narrow-bore C8 column was developed to determine 5-phenyl-3-thioureido-1,2,4-thiadiazole (301029), a novel virus inhibitor in serum. Both 301029 and an internal standard (I.S.) were separated from serum samples by acetonitrile deproteinization and extraction without time-consuming reconstitution. The chromatographic separation was achieved on a C8 reversed-phase narrow-bore column using acetonitrile-water-acetic acid (90:10:0.01, v/v/v) as a mobile phase. The mass spectrometric analysis was performed by atmospheric pressure chemical ionization (APCI) mode with positive ion detection. Single ion monitoring (SIM) scan mode of m/z 237 and 158 was used to quantitatively determine 301029 and I.S., respectively. The low limit of quantitation was 25 ng/ml. The assay exhibited a linear range of 25-2500 ng/ml. Recovery from serum proved to be 100-113%. The precision (C.V.) and accuracy (RE) of the method were 2-12% and 94-112%, respectively. The present method was applied to determine the pharmacokinetic parameters of 301029 following oral administration of the agent to mice at 5 g/kg. The results revealed that the elimination half-life of 301029 was 413 min and the area under serum concentration-time curve was 354 microg/ml/min.

Animals↗

PubMed2001

c-IAP1 blocks TNFalpha-mediated cytotoxicity upstream of caspase-dependent and -independent mitochondrial events in human leukemic cells.

Tumor necrosis factor-alpha (TNFalpha) mediates cytochrome c release from mitochondria, loss of mitochondrial membrane potential (DeltaPsim) and apoptosis in sensitive leukemic cells. In the present study, by using the human leukemic U937 cell line, we demonstrate that the cytochrome c release is caspase-8-dependent and can be blocked by an inhibitor of caspase-8, Z-Ile-Glu (OMe)-Thr-Asp(OMe)-fluoromethyl ketone (Z-IETD.fmk), or a pan caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD.fmk). However, TNFalpha-mediated loss of DeltaPsim was not inhibited by caspase inhibitors. The apoptotic process was blocked by either Z-IETD.fmk or Z-VAD.fmk in cells with lower DeltaPsim. U937 cells with stable transfection of the cellular inhibitor of apoptosis protein 1 (c-IAP1) are resistant to TNFalpha-induced activation of caspases, Bid cleavage, cytochrome c release and DeltaPsim collapse. In addition, both c-IAP1 and XIAP were not up-regulated upon prolonged exposure to TNFalpha. In contrast, there was a caspase-dependent cleavage of XIAP, but not c-IAP1, during treatment with TNFalpha for 7 days. These results demonstrate that c-IAP1 blocks TNFalpha signaling at a level controlling both activation of caspase-8 and a signal to cause loss of DeltaPsim. The sensitive U937 cell line failed to acquire resistance and gain a self-protecting advantage against apoptosis, upon induction of c-IAP1 expression.

Apoptosis↗

PubMed2001

Neurophysiological evidence of spared upper motor conduction fibers in clinically complete spinal cord injury: discomplete SCI in rats.

Motor evoked potentials (MEP) were recorded and characterized by epidural electrodes (scMEP) and extracellular microelectrodes (exMEP) on T(13) level from 10 normal rats and 40 rats with chronic spinal cord injury (SCI). The spinal cord of 40 anesthetized rats were injured with various severity (sham, 35, 70, and 100 g/cm impact injury) at T(8)-T(9) cord using Allen's drop model. The incline plane and Tarlov techniques were investigated to assess clinical neurological function. MEPs in the normal rats elicited by applying transcortical suprathreshold stimulation consisted of 3-4 early negative peaks (N(1), N(2), N(3), N(4)) followed by several late waves. The N(1) and N(2) peaks had their maximal amplitudes in the anterior and ventrolateral funiculus, respectively, irrespective of the polarity of stimulation, which indicated that these impulses were conducted mostly through the extrapyramidal pathways. The 100 g/cm impact injury or transection of the cord caused abolishment of the MEP signals distal to the lesion, whereas the 35 g/cm injury resulted in a latency shift and amplitude decrement of the MEP peaks. Out of 20 rats with 70 g/cm injuries, 18 showed clinically paraplegia. Among them, seven had neurophysiological evidence of residual conduction pathways through the injured cord segment, such as the presence of N(1) and N(2) peaks in scMEP or exMEP. After 4-aminopyridine (4-AP) administration (1 mg/kg), the amplitude of spared exMEP increased significantly and spread more widely. These results suggest that MEPs evoked by transcortical stimulation travel mostly in the extrapyramid tract. The present study provides further direct and objective electrophysiological evidences of spared functional axons after discomplete SCI, since many other studies on this field have achieved similar results previously. Furthermore, pharmaceutical treatment with 4-AP or other K(+) channel blocking agents proved to be a potential therapeutic strategy for patient with chronic SCI.

Animals↗

PubMed2001

Bax translocation is crucial for the sensitivity of leukaemic cells to etoposide-induced apoptosis.

Bax translocation from cytosol to mitochondria is believed to be a crucial step for triggering cytochrome c release from mitochondria. However, it is unclear whether Bax translocation is associated with Bax induction by DNA damaging agents. The induction of Bax in response to DNA damaging agents has been considered to be linked with p53. In this study, we used the p53 negative human chronic myeloid leukaemia K562 cell line. Bax up-regulation occurred at the whole cell level after DNA damage induced by etoposide. However, after incubation with etoposide, Bax failed to translocate to mitochondria and as a result, the apoptotic process was blocked. A Bax stable transfectant, the K/Bax cell line, expressed more Bax protein in the cytosol, mitochondria and nuclei. This Bax overexpression induced cytochrome c release, a reduction of cytochrome c oxidase activity and mitochondrial membrane potential (Delta(Psi)m). However, Bax-induced apoptosis was blocked downstream of mitochondria in K562 cells. The increased levels of mitochondrial Bax sensitized cells to etoposide-induced activation of caspases-2, -3 and -9 and apoptosis. However, after transient transfection with the Apaf-1 gene, K/Bax cells were sensitized to etoposide-induced caspase activation and apoptosis to a larger extent compared with Bax or Apaf-1 transfection alone. We therefore conclude that two mechanisms contribute to the resistance of K562 cells to etoposide-induced apoptosis; firstly failure of Bax targeting to mitochondria and, secondly, deficiency of Apaf-1. Uncoupling of Bax translocation from Bax induction can occur in response to etoposide-induced DNA damage.

Antineoplastic Agents, Phytogenic↗

PubMed2001

Dioxin and furan formation in FBC boilers.

Fluidized bed combustion (FBC) is increasingly being used for municipal solid waste incineration and for various applications in which dioxin and furan (PCDD/F) formation are concerns. Despite the fact that fluidized bed combustion is a relatively low temperature system, current evidence shows that they perform relatively well. One hypothesis is that sulfur, which is contained in some of the fuels used in FBC (e.g. coal in cofiring situations), helps to reduce dioxin production. This paper endeavors to examine this speculation and finds that such benefits depend on the CI/S ratio and that at higher sulfur addition levels dioxins, furans, and polycyclic aromatic hydrocarbon (PAH) production may actually increase. This and the reasons for it are discussed.

Air Pollutants↗

PubMed2001

Apaf-1 protein deficiency confers resistance to cytochrome c-dependent apoptosis in human leukemic cells.

The human leukemia cell lines K562, CEM, CEM/VLB(100), human leukemic blasts, and the bladder cancer J82 cell line have different sensitivities to UV light-induced apoptosis. It is reported that resistance to UV light-induced apoptosis occurs at a point in the apoptotic pathway upstream of caspase-3 but downstream of mitochondrial cytochrome c release. It is demonstrated that the block is due to deficiency of Apaf-1, a critical member of the apoptosome. Sensitivity to apoptosis was independent of caspase-9b or XIAP (inhibitors of apoptosis proteins) expression or levels of procaspase-9. Transfection of Apaf-1 conferred sensitivity to apoptosis in resistant cells. Apaf-1 deficiency may constitute a significant mode of resistance to apoptosis in human leukemia.

Antibodies↗

PubMed2001

Central nervous system, uterus, heart, and leukocyte expression of the LOXL3 gene, encoding a novel lysyl oxidase-like protein.

A BLASTN search using the mouse lor-2 cDNA identified three overlapping ESTs (AI752772, AA852888, and R55706) in the GenBank database. These expressed sequence tags were assembled into a contig of 3121 nucleotides with an open reading frame of 2262 bp. The encoded putative polypeptide of 754 amino acids presented all structural characteristics of the lysyl oxidase (LOX) enzyme family, a copper-binding site with four histidyl residues, the lysyl and tyrosyl residues known to be involved in LOX enzyme in the formation of the quinone cofactor and surrounding sequences, and the cytokine receptor-like domain. In addition, four scavenger receptor cysteine-rich (SRCR) domains were found in the N-terminal region of the protein. The gene encoding this new cDNA, which we have referred to as human lysyl oxidase-like 3 (humanLOXL3), has been mapped to chromosome 2p13.3, overlapping at its 3' end the HtrA2 serine protease gene. The structure of the humanLOXL3 gene was deduced from the BAC clone bac91a19 sequence and contained 14 exons. The expression pattern of this new member of the LOX gene family appears to be different from that of the LOX and LOX-like genes, as the central nervous system, neurons, and also leukocytes expressed humanLOXL3. A BLASTN search of the human EST database indicated the presence of ESTs, corresponding to alternative splice variants of LOXL3, that lacked exon 5 and exon 8. The putative resulting protein retained the region encoding the structural and functional elements of the amine oxidase but the second and fourth SRCR domains were truncated and the potential BMP-1 cleavage site was not present. The presence of domains unrelated to the traditional amine oxidase activity is a strong indication that humanLOXL3 might fulfill other functions in addition to intrinsic enzyme activity.

Alternative Splicing↗

PubMed2001

Trail-induced apoptosis in Type I leukemic cells is not enhanced by overexpression of bax.

We have previously shown that Bax translocation was crucial in TNFalpha or etoposide-induced apoptosis. Overexpression of Bax sensitized chronic myeloid leukemic K562 cells to etoposide-induced apoptosis. Treatment with TNF-related apoptosis-inducing ligand (TRAIL) induces a loss of mitochondrial membrane potential (DeltaPsim), cytochrome c release from mitochondria, activation of caspases-8, -9, and -3, and cleavage of Bid in the K562 cell line. Bax failed to sensitize K562 cells to TRAIL-induced apoptosis. TRAIL did not induce Bax expression and/or translocation from cytosol to mitochondria in the K562 cell line. However, 100 microM Z-VAD.fmk, a pan caspase inhibitor, completely blocked TRAIL-initiated mitochondrial alterations and cleavages of caspases and Bid. We propose that TRAIL-induced apoptosis in K562 cells is via Type I apoptotic signal pathway. Bax translocation is not essential for TRAIL-induced cytochrome c release and DeltaPsim collapse in the Type I cells.

Amino Acid Chloromethyl Ketones↗

PubMed2001

Apaf-1XL is an inactive isoform compared with Apaf-1L.

Apaf-1 plays a crucial role in the cytochrome c/dATP-dependent activation of caspase-9 and -3. We found that the human myeloid leukemic K562 cells were more resistant to cytochrome c-induced activation of caspase-9 and -3 in a cell-free system compared with the human T-lymphoblastic subclone CEM/VLB(100) cells. Apaf-1 cDNA sequencing revealed an additional insert of 11 aa between the CARD and CED-4 (ATPase) domains in K562 cells, which was identical to the sequence of Apaf-1XL. Immunoprecipitation of Apaf-1 with caspase-9 after a cell-free reaction demonstrated that Apaf-1XL in the K562 cell line showed a lower binding ability to caspase-9 compared with Apaf-1L protein. The resistance of K562 cells to cytochrome c-dependent apoptosis may be partly due to this Apaf-1XL form. These results suggest that the additional insert between CARD and CED-4 domains might affect Apaf-1 recruitment of caspase-9 during apoptosis.

Adenosine Triphosphatases↗