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Biomedical subjects

Qin Wang

Publications and source records attributed to Qin Wang.

At least 73 records · Page 4Linked to original sources
PubMed2005

Inactivation kinetics of guanidinium chloride on Penaeus vannamei beta-N-acetyl-D-glucosaminidase and the relationship of enzyme activity and its conformation.

The effects of guanidinium chloride (GuHCl) on the activity of Penaeus vannamei beta-N-acetyl-D-glucosaminidase (NAGase) have been studied. The results show that GuHCl, at appropriate concentrations, can lead to reversible inactivation of the enzyme, and the IC50 is estimated to be 0.6 M. Changes of activity and conformation of the enzyme in different concentrations of GuHCl have been studied by measuring the fluorescence spectra and its relative activity after denaturation. The fluorescence intensity of the enzyme decreases distinctly with increasing GuHCl concentrations, and the emission peaks appear red-shifted (from 339.4 to 360 nm). Changes in the conformation and catalytic activity of the enzyme are compared. The extent of inactivation is greater than that of conformational changes, indicating that the active site of the enzyme is more flexible than the whole enzyme molecule. The kinetics of inactivation has been studied using the kinetic method of the substrate reaction. The rate constants of inactivation have been determined. The value of k(+0) is larger than that of k'(+0) which suggests that the enzyme is protected by substrate to a certain extent during guanidine denaturation.

Acetylglucosaminidase↗
PubMed2005

A cost comparison of alternative regimens for treatment-refractory partial seizure disorder: an econometric analysis.

BACKGROUND: Partial seizure disorder is typically treated by monotherapy with antiepileptic drugs (AEDs). However, when the condition is refractory to the initial treatment regimen, patients may be switched to monotherapy with another AED or to combination therapy with the initial AED plus a second AED. OBJECTIVES: The purpose of this study was to examine the economic costs associated with treatment-refractory partial seizure disorder and to compare the costs of 2 alternative approaches: a switch to oxcarbazepine (OXC) monotherapy or the addition to the regimen of another AED (AED add-on). METHODS: Adult patients with a diagnosis of partial seizure disorder who received initial AED monotherapy between January 1, 2000, and March 31, 2003, were identified from the PharMetrics Patient-Centric Database, a health plan administrative claims database. The medical and pharmacy history of these patients was analyzed from 6 months before a change to either OXC monotherapy or AED add-on therapy through 12 months after the change in treatment. Total health care resource utilization and the associated costs were compared within each cohort before and after the change, as well as between cohorts, with statistical differences tested using Wilcoxon rank sum tests. Multivariate econometric analyses were performed to examine the impact of age, sex, geographic location, Charlson Comorbidity Index, and the presence of specific comorbidities. RESULTS: Demographic and clinical characteristics 102 were similar between the OXC monotherapy cohort (n = 259) and the AED add-on cohort (n = 795). Annual direct treatment costs increased in both groups in the period after the failure of initial monotherapy, increasing from 10,462 US dollars to 11,360 US dollars in the OXC cohort and from 10,137 US dollars to 12,201 US dollars in the AED add on cohort (P < 0.01). Increased pharmacy costs were the primary driver behind cost increases in both cohorts. Patients in the AED add-on cohort were significantly more likely to have an emergency department visit during the period after the failure of initial monotherapy compared with the OXC monotherapy cohort (odds ratio = 1.52; P < 0.05). CONCLUSION: Despite limitations, the results of retrospective analysis of claims data suggest that the care of patients with treatment-refractory partial seizure disorder is costly and may vary significantly based on the pattern of care.

Adult↗
PubMed2005

Treatment of generalized anxiety disorder with escitalopram: pooled results from double-blind, placebo-controlled trials.

BACKGROUND: Escitalopram 10 mg/day is an effective and well-tolerated antidepressant. Three randomized controlled trials recently evaluated the safety and efficacy of escitalopram in the treatment of generalized anxiety disorder (GAD). METHODS: The trial designs were virtually identical, allowing data to be pooled across studies. Male and female outpatients, ages 18-80 years, with DSM-IV-defined GAD were randomized to double-blind treatment with escitalopram or placebo for 8 weeks. Escitalopram dose was fixed at 10 mg/day for the first 4 weeks, after which increases to 20 mg/day were permitted. The primary efficacy variable was the mean change from baseline in total Hamilton Anxiety Scale (HAMA) score. RESULTS: Approximately 850 patients were randomized to double-blind treatment. In each individual study, escitalopram was significantly superior to placebo (p<0.05) as measured by change from baseline in HAMA score. By-visit analyses of data pooled across studies revealed significantly greater improvement (p<0.05) in the escitalopram group beginning at week 1 or 2 and continuing through week 8 for all primary and secondary efficacy variables. The mean change in HAMA total score from baseline to endpoint also was significantly greater for patients maintained at escitalopram 10 mg/day than for those receiving placebo. Escitalopram was generally well tolerated. LIMITATIONS: The studies included in this analysis were of short-term duration and excluded patients with significant medical and psychiatric comorbidities, such as major depressive disorder. CONCLUSION: Results from the individual trials and the pooled analysis demonstrate that escitalopram is effective and well tolerated for the treatment of GAD.

Adolescent↗
PubMed2005

Iron loading inhibits ferroportin1 expression in PC12 cells.

Ferroportin1 (FP1 or MTP1/IREG1), the product of the SLC40A1 gene, is a main iron export protein in mammals. Its mRNA contains an iron response element (IRE) in its 5' untranslated region, but the way this gene is regulated by iron is still unclear. The existence of FP1 in the brain has been recently confirmed. To better understand the role of this important transmembrane iron exporter in brain iron homeostasis, we investigated the effects of iron and nitric oxide (NO) on FP1 expression and that of a FP1 antibody on iron release in nerve growth factor-treated rat PC12 cells. We found that FP1 expression was down-regulated by iron loading but stimulated by iron chelation and treatment with a NO donor, S-nitroso-N-acetylpenicillamine (SNAP). In addition, a significant decrease in iron release was found in cells treated with a FP1 antibody. Our findings imply that regulation of FP1 by iron in the cells is at the transcriptional level, rather than by an IRE/IRP-mediated pathway. Based on our results and published data, it is suggested that the transcriptional and translational (IRP/IRE pathway) mechanisms of FP1 expression might both operate in a tissue-specific manner and that FP1 might have a role in iron export from PC12 cells.

Animals↗
PubMed2005

Quantitative proteomic analysis of age-related changes in human cerebrospinal fluid.

Identification of cerebrospinal fluid (CSF) biomarkers of the common age-related neurodegenerative diseases would be of great value to clinicians because of the difficulties in differential diagnoses of these diseases in clinical practice. Proteins are one class of potential biomarkers currently under investigation in the hope that different ensembles of proteins will aid in the diagnosis of these diseases, as well as in the assessment of progression and response to therapy. However, before undertaking a rational approach to CSF protein biomarkers of age-related neurodegeneration, we must first systematically identify CSF proteins and determine whether their levels change with normal aging. In this study, we used a powerful shotgun proteomic method, two-dimensional microcapillary liquid chromatography electrospray ionization tandem mass spectrometry, to identify proteins in human CSF. Additionally, using pooled CSF samples, we quantitatively compared the CSF proteome of younger adults with that of older adults using isotope-coded affinity tags (ICAT). From these studies we identified more than 300 proteins in CSF and found that there were 30 proteins with >20% change in concentrations between older and younger individuals. Finally, we validated changes in concentration for two of these proteins using Western blots in CSF from a separate set of individuals. These data not only expand substantially our current knowledge regarding human CSF proteins, but also supply the necessary information to appropriately interpret protein biomarkers of age-related neurodegenerative diseases.

Adult↗
PubMed2005

Effect of comorbidities on medical care use and cost among refractory patients with partial seizure disorder.

PURPOSE: The goal of this work was to assess the effect of comorbidities on medical care use and costs among patients with partial seizure disorder who are also refractory to initial antiepileptic drug (AED) monotherapy. METHODS: Retrospective data from the PharMetrics managed care claims database were collected for adult patients treated with AED monotherapy between January 1, 2000 and March 31, 2002. The associations of comorbidity, specifically the Charlson Comorbidity Index (CCI) and incidence of specific comorbid conditions, with total costs and with hospitalization were analyzed via econometric analysis and logistic regression. RESULTS: Five hundred forty-nine patients were identified and analyzed. The odds of hospitalization were 3.7 times greater among patients with a CCI1, than for patients without comorbidities (OR=3.7, 95% CI=1.7-7.9), while treatment costs for all medical care were 136% higher (P<0.05). Depression had the largest marginal effect on costs and on the likelihood of hospitalization. CONCLUSIONS: For patients refractory to initial AED monotherapy, the presence of comorbidities, especially depression, is associated with a substantial increase in medical care use and costs.

Adolescent↗
PubMed2005

Inhibitory effects of 4-vinylbenzaldehyde and 4-vinylbenzoic acid on the activity of mushroom tyrosinase.

Tyrosinase (EC 1.14.18.1) catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones which form brown or black pigments. Here, the inhibitory effects of 4-vinylbenzaldehyde and 4-vinylbenzoic acid on the activity of mushroom tyrosinase have been investigated. The results showed that both 4-vinylbenzaldehyde and 4-vinylbenzoic acid could inhibit both monophenolase activity and diphenolase activity of the enzyme. For the monophenolase activity, 4-vinylbenzoic acid could lengthen the lag time, but 4-vinylbenzaldehyde could not. Both 4-vinylbenzaldehyde and 4-vinylbenzoic acid decreased the steady-state activity, and the IC50 values were estimated as 93 microM and 3.0 mM for monophenolase activity, respectively. For the diphenolase activity, the inhibitory capacity of 4-vinylbenzaldehyde was stronger than that of 4-vinylbenzoic acid, and the IC50 values were estimated as 23 microM and 0.33 mM, respectively. Kinetic analyses showed that inhibition by both compounds was reversible and their mechanisms were mixed-II type; their inhibition constants were also determined and compared.

Agaricales↗
PubMed2005

Quantitative proteomics of cerebrospinal fluid from patients with Alzheimer disease.

Biomarkers to assist in the diagnosis and medical management of Alzheimer disease (AD) are a pressing need. We have employed a proteomic approach, microcapillary liquid chromatography mass spectrometry of proteins labeled with isotope-coded affinity tags (ICAT), to quantify relative changes in the proteome of human cerebrospinal fluid (CSF) obtained from the lumbar cistern. Using CSF from well-characterized AD patients and age-matched controls at 2 different institutions, we quantified protein concentration ratios of 42% of the 390 CSF proteins that we have identified and found differences > or = 20% in over half of them. We confirmed our findings by western blot and validated this approach by quantifying relative levels of amyloid precursor protein and cathepsin B in 17 AD patients and 16 control individuals. Quantitative proteomics of CSF from AD patients compared to age-matched controls, as well as from other neurodegenerative diseases, will allow us to generate a roster of proteins that may serve as specific biomarker panels for AD and other geriatric dementias.

Adult↗
PubMed2005

Safety and efficacy of escitalopram in the long-term treatment of generalized anxiety disorder.

INTRODUCTION: Generalized anxiety disorder (GAD) is a chronic disorder that requires long-term treatment. Escitalopram has previously been shown to be effective and well tolerated in the acute treatment of GAD. METHOD: Three 8-week, double-blind, placebo-controlled trials of nearly identical design were conducted of escitalopram in moderate-to-severe GAD (DSM-IV criteria). Patients completing these trials were given the option of entering a 24-week, open-label, flexible-dose trial of escitalopram (10-20 mg/day). Data were collected from September 20, 2000, to August 15, 2002. RESULTS: Two hundred ninety-nine (56.8%) of 526 patients completed 24 weeks of open-label treatment. The mean Hamilton Rating Scale for Anxiety (HAM-A) score at baseline of open-label treatment was 13.1. Long-term escitalopram treatment led to continuing improvement on all anxiety and quality-of-life (QOL) scores. Of those completing 24 weeks of treatment, 92.0% were responders (Clinical Global Impressions-Improvement scale score < or = 2), and the mean HAM-A score in the completed analysis was 6.9; using the last observation carried forward (LOCF), 75.9% were responders, and the mean HAM-A score in the LOCF analysis was 9.2 at endpoint. Insufficient therapeutic response and adverse events led to withdrawal of 4.2% and 9.9% of patients, respectively. Mean increase in weight from baseline was 3.0 lb. No clinically notable changes in mean laboratory, vital sign, or electrocardiographic values were observed. CONCLUSION: These results support the long-term tolerability and effectiveness of escitalopram in the treatment of GAD.

Adult↗
PubMed2005

Redifferentiation of human hepatoma cell induced by 6-(p-chlorophenyl)-3-[1-(p-chlorophenyl)-5-methyl-1 H-1,2,3-triazol-4-yl]-s-triazolo[3,4-b]-1,3,4-thiadiazole (TDZ).

6-(p-Chlorophenyl)-3-[1-(p-chlorophenyl)-5-methyl-1 H-1,2,3-triazol-4-yl]-s-triazolo[3,4-b]-1,3,4-thiadiazole (TDZ) is a derivative of various substituted s-triazolo[3,4-b]-1,3,4-thiadiazoles, which are associated with diverse pharmacological activities. However, the antitumor activity of TDZ is not well understood. To evaluate its role on tumor cell lines, we have examined the effect of TDZ on two tumor lines: human hepatoma cell (SMMC-7721) in vitro and Sarcoma180 tumor (S180) in vivo. The cytotoxicity of TDZ on human hepatoma cells was assessed using the MTT assay. The inhibition on tumor growth was evaluated by means of trypan blue exclusion test in vitro, and using a Sarcoma180 tumor (S180) animal model in vivo. A scanning electronic microscope was used to discover the morphological changes on cell surface, cell electrophoresis was employed to determine the changes of cell surface negative charges, and alpha-fetoprotein was applied as a biomarker of hepatoma. The effect of TDZ on DNA synthesis was determined by a [3H]-thymidine incorporation assay, and cell cycle distribution by flow cytometry. The IC50 value of TDZ on SMMC-7721 cells was 52.9 microg/ml (48 h). However, TDZ could inhibit the growth of SMMC-7721 cells at concentrations far lower than the IC50 value. Treated with the same low concentrations of TDZ, microvilli on the surface of SMMC-7721 cells decreased obviously, electrophoresis rate of cells reduced from 2.14 microm ms(-1) x V(-1) x cm(-1) of control to 1.54 and 1.56 microm x s(-1) x V-1 x cm(-1), the content of AFP dropped from 205.14 +/- 6.41 ng x mg(-1) Pr to 115.68 +/- 3.47 and 78.57 +/- 2.35 ng mg(-1) Pr, and the DNA replication was inhibited by 26.8% and 45.2%. These results indicated that TDZ may inhibit proliferation of cancer cells by reversing SMMC-7721 cells malignant phenotypic characteristics and inducing redifferentiation. Flow cytometry showed that TDZ-treated cells resulted in a higher proportion of cells in S phase compared with untreated cells, and only when the concentration reached 64 microg/ml, the apoptosis could happen at the rate of 4.2%. Detection of the inhibition of Sarcoma 180 tumor growth in vivo showed that TDZ reduced the tumor weight and 69.08% of the growth was inhibited. TDZ could inhibit the proliferation of tumors in vitro and in vivo; the possible antitumor mechanism might be inducing redifferentiation at a lower dosage on vitro.

Animals↗
PubMed2005

Diterpenoids from the Chinese herb Caryopteris terniflora and their antibacterial and antitumor activity.

Two ent-kaurene type diterpenoids, diterpenoids A (1) and B (2) were isolated from the Chinese herb Caryopteris terniflora and defined as ent-7beta, 11alpha,14-trihydroxy-18-aldehyde-11beta-20-epoxy-kaur-16-en15-one and ent-7beta,14-dihydroxy-11alpha-methoxy-18-aldehyde-11beta-20-epoxy-kaur-16-en-15-one respectively. Compounds 1 and 2 showed significant antibacterial and antitumour activity.

Anti-Bacterial Agents↗
PubMed2005

[Restenosis and its management after metallic stents implantation in benign tracheal and main bronchial stenosis].

OBJECTIVE: To observe the occurrence of restenosis after metallic stents implantation in benign tracheal and main bronchial stenosis, and to evaluate the therapeutic effects of balloon dilatation, cryotherapy and electrocautery. METHODS: Thirty patients with benign tracheal stenosis and 35 patients with main bronchial stenosis caused by tuberculosis were treated with metallic stents implantation and a follow-up was carried out to observe the occurrence of restenosis. Combined balloon dilatation, cryotherapy and electrocautery were used to manage the restenosis. The lumen of stenotic segment, dyspnea index and pulmonary function were measured before management and after the patient's condition became stable. RESULTS: Restenosis occurred in 6 of the 30 patients receiving tracheal stenting and in 8 of the 35 patients receiving bronchial stenting, the restenosis rates were 20% and 22.86%, respectively. In total, 30 Chinese-made stents and 36 Ultraflex stents were implanted, and the restenosis rate was 20% and 22.2%, respectively (P > 0.05). The restenosis rate was 4/9 in the upper segmental tracheal stents, and was 9.09% in the middle-lower segmental stents (chi(2) = 5.114, P < 0.05, but chi(c)(2) = 3.100, P > 0.05). The restenosis rate was 16.67% in the fibrotic stage of endobronchial tuberculosis (EBTB), and was 60% in the inflammatory reaction stage of EBTB (chi(2) = 4.564, P < 0.05, but chi(c)(2) = 2.437, P > 0.05). The effective rate was 4/6 in the tracheal stenting restenosis patients, and was 2/4 and 2/2 in the upper and middle-lower segment groups, respectively. The effective rate was 7/8 in the bronchial stenting restenosis patients. After management, the lumen diameter of stenotic segment in the tracheal stenting restenosis patients increased from (3.33 +/- 1.63) mm to (9.33 +/- 3.98) mm (P < 0.02), the dyspnea index decreased from (3.67 +/- 0.52) to (1.50 +/- 1.64) (P < 0.02), the vital capacity (VC) increased from (1.39 +/- 0.17) L to (2.43 +/- 0.70) L (P < 0.01), the forced expiratory volume in one second (FEV(1)) increased from (1.02 +/- 0.15) L to (2.00 +/- 0.72) L (P < 0.02). After management, the lumen diameter of stenosis segment in the bronchial stenting restenosis patients increased from (3.00 +/- 0.76) mm to (7.38 +/- 2.00) mm (P < 0.001), the dyspnea index decreased from (1.63 +/- 0.52) to (0.50 +/- 0.76) (P < 0.005), VC increased from (1.74 +/- 0.16) L to (2.74 +/- 0.41) L (P < 0.001), FEV(1) increased from (1.41 +/- 0.19) L to (2.36 +/- 0.37) L (P < 0.001). CONCLUSION: Restenosis occurred in some patients with benign tracheal and tuberculous bronchial stenosis after metallic stent implantation. The restenosis rate was higher in the upper tracheal stenosis than that in the middle-lower tracheal stenosis. Caution should be taken when metallic stents are placed in this part of the trachea. The restenosis rate was higher in the inflammatory reaction stage of EBTB than in the fibrotic stage. Effort should be made to avoid placing metallic stents at this stage of the disease. Balloon dilatation, cryotherapy and eletrocautery are effective methods in managing restenosis after stent implantation.

Adult↗
PubMed2005

[Building immune microsphere against tumor necrosis factor-alpha (TNF-alpha)].

We have constructed the immune microsphere against tumor necrosis factor-alpha (TNF-alpha) prospectively, hoping to establish the experiment groundwork in more researches which could be used in specific elimination of the TNF-alpha by blood purification method for the future. The recombinant human tumor necrosis factor-alpha monoclonal antibody (rHTNF-alpha McAb) was wrapped on the polystyrene microsphere (PSM) carrier connecting poly-L-lysine (PLL) beforehand. They were earmarked by the fluorescein isothiocyanate (FITC) respectively. The packing conditions were examined using the inversted and fluorescence microscopes and the spectrophotometer. The results showed that the best conditions for wrapping were 20 degrees C, pH9.5 and 60 minutes. The PLL content was not changed in the washing fluid after coating, which indicated the wrapping was quite firm. At the same temperature and same coating time, the rHTNF-alpha McAb coated on the PLL was obviously substantial when the concentration of glutaraldehyde solution was 0.2%. The findings demonstrated that the built immune microsphers can be used as a novel adsorption material. This method is simple and economic, and it offers a new approach to the related studies.

Antibodies, Monoclonal↗
PubMed2004

Characterization of (2R, 3S)-2-([[4-(2-butynyloxy)phenyl]sulfonyl]amino)-N,3-dihydroxybutanamide, a potent and selective inhibitor of TNF-alpha converting enzyme.

TNF-alpha converting enzyme (TACE) is a validated therapeutic target for the development of oral tumor necrosis factor-alpha (TNF-alpha) inhibitors. Here we report the pre-clinical results and characterization of a selective and potent TACE inhibitor, (2R, 3S)-2-([[4-(2-butynyloxy)phenyl]sulfonyl]amino)-N,3-dihydroxybutanamide (TMI-2), in various in vitro and in vivo assays. TMI-2 is a potent TACE inhibitor in an enzymatic FRET assay (IC50=2 nM). It is more than 250-fold selective over MMP-1, -7, -9, -14, and ADAM-10 in vitro. In cell-based assays and human whole blood, TMI-2 inhibits lipopolysaccharide (LPS)-induced TNF secretion with IC50s<1 uM. Importantly, TMI-2 inhibits the spontaneous release of TNF-alpha in human synovium tissue explants of rheumatoid arthritis patients with an IC50 of 0.8 microM. In vivo, TMI-2 potently inhibits LPS-induced TNF-alpha production in mice (ED50=3 mg/kg). In the adjuvant-induced arthritis (AIA) model in rats, treatment with TMI-2 at 30 mg/kg and 100 mg/kg p.o. b.i.d. was highly effective in reducing joint arthritis scores. In a semi-therapeutic collagen-induced arthritis (CIA) model in mice, TMI-2 is highly effective in reducing disease severity scores after oral treatment at 100 mg/kg twice per day. In summary, TMI-2 is a potent and selective TACE inhibitor that inhibits TNF-alpha production and reduces the arthritis scores in pre-clinical models. TMI-2 represents a novel class of TACE inhibitors that may be effective and beneficial in the treatment of rheumatoid arthritis as well as other TNF-mediated inflammatory autoimmune diseases.

ADAM Proteins↗
PubMed2004

SHP-2 modulates interleukin-1-induced Ca2+ flux and ERK activation via phosphorylation of phospholipase Cgamma1.

Interleukin-1 (IL-1) signaling is dependent on focal adhesions, structures that are enriched with tyrosine kinases and phosphatases. Because the non-receptor tyrosine phosphatase Src homology 2 domain-containing protein tyrosine phosphatase-2 (SHP-2) is enriched in focal adhesions and IL-1-induced ERK activation requires increased Ca(2+), we determined whether SHP-2 modulates IL-1-induced Ca(2+) signaling. In SHP-2-deficient fibroblasts, IL-1-induced Ca(2+) signaling and ERK activation were markedly diminished compared with cells expressing SHP-2. IL-1-induced Ca(2+) release from the endoplasmic reticulum occurred in the vicinity of focal adhesions and was strongly inhibited by the blockage of phospholipase C (PLC) catalytic activity. Immunoprecipitation and immunostaining showed that SHP-2, the endoplasmic reticulum-specific protein calnexin, and PLCgamma1 were associated with focal adhesions; however, these associations and IL-1-induced ERK activation dissipated after cells were plated on non-integrin substrates. IL-1 promoted phosphorylation of SHP-2 and PLCgamma1. IL-1-induced phosphorylation of PLCgamma1 was diminished in SHP-2-deficient cells but was restored by stable transfection with SHP-2. BAPTA/AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester)) blocked IL-1-induced phosphorylation of SHP-2 and PLCgamma1, indicating mutually dependent interactive roles for Ca(2+), SHP-2, and PLCgamma1 in IL-1 signaling. We conclude that SHP-2 is critical for IL-1-induced phosphorylation of PLCgamma1 and thereby enhances IL-1-induced Ca(2+) release and ERK activation. Focal adhesions co-localizing with the endoplasmic reticulum may provide molecular staging sites required for ERK activation.

Animals↗
PubMed2004

Deletion of the chloroplast-localized Thylakoid formation1 gene product in Arabidopsis leads to deficient thylakoid formation and variegated leaves.

Development of thylakoid membranes depends upon the transport of membrane vesicles from the chloroplast inner envelope and subsequent fusion of vesicles within the interior of the plastid. The Arabidopsis (Arabidopsis thaliana) Thylakoid formation1 (Thf1) gene product is shown here to control an important step required for the normal organization of these vesicles into mature thylakoid stacks and ultimately for leaf development. The Arabidopsis Thf1 gene encodes an imported chloroplast protein, as shown by in vitro import and localization of a Thf1-green fluorescent protein fusion product in transgenic plants. This gene is conserved in oxygenic photoautotrophs ranging from cyanobacteria to flowering land plants. Transcript levels for Thf1 are induced in the light and decrease under dark conditions, paralleling profiles of light-regulated nuclear genes involved in chloroplast function. Disruption of the Thf1 gene via T-DNA insertion results in plants that are severely stunted with variegated leaf patterns. Nongreen sectors of variegated leaves lacking Thf1 expression contain plastids that accumulate membrane vesicles on the interior and lack organized thylakoid structures. Green sectors of Thf1-disrupted leaves contain some chloroplasts that form organized thylakoid membranes, indicating that an inefficient compensatory mechanism supports thylakoid formation in the absence of Thf1. Genetic complementation of a Thf1 knockout line confirms the role of this gene in chloroplast and leaf development. Transgenic plants expressing the Thf1 gene in antisense orientation are stunted with altered thylakoid organization, especially in young seedlings. The data indicate that the Thf1 gene product plays a crucial role in a dynamic process of vesicle-mediated thylakoid membrane biogenesis.

Amino Acid Sequence↗
PubMed2004

MKK3 and -6-dependent activation of p38alpha MAP kinase is required for cytoskeletal changes in pulmonary microvascular endothelial cells induced by ICAM-1 ligation.

Previous studies demonstrated that neutrophil adherence induces ICAM-1-dependent cytoskeletal changes in TNF-alpha-treated pulmonary microvascular endothelial cells that are prevented by a pharmacological inhibitor of p38 MAP kinase. This study determined whether neutrophil adherence induces activation of p38 MAP kinase in endothelial cells, the subcellular localization of phosphorylated p38, which MAP kinase kinases lead to p38 activation, which p38 isoform is activated, and what the downstream targets may be. Confocal microscopy showed that neutrophil adhesion for 2 or 6 min induced an increase in phosphorylated p38 in endothelial cells that was punctate and concentrated in the central region of the endothelial cells. Studies using small interfering RNA (siRNA) to inhibit the protein expression of MAP kinase kinase 3 and 6, either singly or in combination, showed that both MAP kinase kinases were required for p38 phosphorylation. Studies using an antisense oligonucleotide to p38alpha demonstrated that inhibition of the protein expression of p38alpha 1) inhibited activation of p38 MAP kinase without affecting the protein expression of p38beta; 2) prevented phosphorylation of heat shock protein 27, an actin binding protein that may induce actin polymerization upon phosphorylation; 3) attenuated cytoskeletal changes; and 4) attenuated neutrophil migration to the EC borders. Thus MAP kinase kinase3- and 6-dependent activation of the alpha-isoform of p38 MAP kinase is required for the cytoskeletal changes induced by neutrophil adherence and influences subsequent neutrophil migration toward endothelial cell junctions.

Actins↗