Biomedical subjects

Chun Zhang

Publications and source records attributed to Chun Zhang.

82 records · Page 5Linked to original sources

PubMed2002

An alternatively spliced isoform of transcriptional repressor ATF3 and its induction by stress stimuli.

Activating transcription factor 3 (ATF3) is a member of the ATF/CREB family of transcription factors and its expression is increased by various pathophysiological conditions and in several cancer cells. In this study, we describe two alternatively spliced ATF3DeltaZip mRNAs: ATF3DeltaZip2a and ATF3DeltaZip2b. Both variants encoded the same truncated protein of 135 amino acids, which lacked the leucine zipper domain and was incapable of binding to the ATF/CRE motif. The ATF3DeltaZip2 protein was shown to be localized in the nuclei and counteracted the transcriptional repression by the full-length ATF3. Western blot analysis showed that ATF3DeltaZip2 was expressed in cells exposed to A23187. Further study showed that, similar to the full-length ATF3, the expression of ATF3DeltaZip2 was induced by a wide range of stress stimuli. However, its expression was not detectable in cancer cells that constitutively over-expressed ATF3. Taken together, our results suggest that ATF3DeltaZip2, a protein derived from alternatively spliced mRNAs, is induced by various stress signals and may modulate the activity of the full-length ATF3 protein during stress response.

Activating Transcription Factor 3↗

PubMed2002

Identification and biochemical characterization of a novel transcription elongation factor, Elongin A3.

The Elongin complex stimulates the rate of transcription elongation by RNA polymerase II by suppressing the transient pausing of the polymerase at many sites along the DNA template. Elongin is composed of a transcriptionally active A subunit and two small regulatory B and C subunits, the latter binding stably to each other to form a binary complex that interacts with Elongin A and strongly induces its transcriptional activity. To further understand the role of Elongin A in transcriptional regulation by RNA polymerase II, we are attempting to identify Elongin A-related proteins. Here, we report on the molecular cloning, expression, and biochemical characterization of human Elongin A3, a novel transcription elongation factor that exhibits 49 and 81% identity to Elongin A and the recently identified Elongin A2, respectively. The mRNA of Elongin A3 is ubiquitously expressed, and the protein is localized to the nucleus of cells. Mechanistic studies have demonstrated that Elongin A3 possesses similar biochemical features to Elongin A2. Both stimulate the rate of transcription elongation by RNA polymerase II and are capable of forming a stable complex with Elongin BC. In contrast to Elongin A, however, their transcriptional activities are not activated by Elongin BC. Structure-function analyses using fusion proteins composed of Elongin A3 and Elongin A revealed that the COOH-terminal region of Elongin A is important for the activation by Elongin BC.

Amino Acid Sequence↗

PubMed2002

Modulation of iron regulatory protein-1 by various metals.

Iron regulatory protein-1 (IRP-1) is known as a cytosolic aconitase and a central regulator of iron (Fe) homeostasis. IRP-1 regulates the expression of Fe metabolism-related proteins by interacting with the Fe-responsive element (IRE) in the untranslated regions of mRNAs of these proteins. However, it is less known whether IRP-1 modulates various non-Fe metals. In the present study, we showed that treatment of homogenously purified IRP-1 with non-Fe metals decreased the affinity to IRE in RNA band shift assays and increased aconitase activity. Non-Fe metals also inhibited (55)Fe incorporation into the fourth labile position of the Fe-S cluster of IRP-1. In PLC hepatoma cells, metal loading inactivated binding activity and activated enzyme activity. It also suppressed transferrin receptor mRNA expression in the cells. These results suggest that various non-Fe metals modulate IRP-1 by conversion of the 3Fe-4S apo-form to a [1 non-Fe metal + 3Fe]-4Fe holo-form.

Aconitate Hydratase↗

PubMed2002

[The effect of internal limiting membrane removal on healing of idiopathic macular hole].

OBJECTIVE: To prospectively investigate the effect on macular hole healing after internal limiting membrane (ILM) removal during idiopathic macular hole (IMH) surgery. METHODS: Forty-one consecutive patients (forty-one eyes) with idiopathic macular hole underwent pars plana vitrectomy (PPV) combined with surgical removal of the epiretinal membranes overlying the hole, gas/fluid exchange and C(3)F(8) intraocular tamponade. The patients were randomly divided into two groups, group A 19 patients in non-ILM-peeling group, group B 22 patients in ILM peeling group who underwent the removal of internal limiting membrane surrounding the hole. RESULTS: Among the 41 cases, IMHs were completely closed in 37 eyes (90.2%). In the ILM removal group, IMHs were closed in 22 cases (22/22, 100%). In the non-ILM removal group, IMHs were closed only in 15 eyes (15/19, 78.9%). There was a significant difference between the two groups (P < 0.05). CONCLUSION: PPV is a valid treatment for IMH and the removal of ILM may help IMH close after surgery.

Adult↗

PubMed2002

[Phase II clinical trial of nedaplatin in advanced non-small cell lung cancer].

BACKGROUND & OBJECTIVE: The aim of this study was to observe the efficacy and the side effects of nedaplatin in treatment of non-small cell lung cancer (NSCLC). METHODS: This is a multi-center phase II clinical trial. The previously chemotherapy treated patients with NSCLC were administrated nedaplatin alone. Nedaplatin was given at 100 mg/m2, i.v., repeated every 3 weeks. The chemonaive patients with NSCLC were randomized to two groups. The combination trial group was given with nedaplatin + vindesine regimen, and the combination control group with cisplatin + vindesine. RESULTS: Of 138 patients, 16 were in the nedaplatin single drug group; 60 were in the combination trial group; and 62 were in the combination control group. All of the 16 cases in the single drug group, which were treated with platinum previously, achieved 12.5% of response rate. And the combination trial group and control group had a very similar response rate, which were 26.7% versus 25.8%, respectively. The incidence rates of neutropenia and anemia were similar in the two groups. But the incidence rate of thrombocytopenia was higher in the trial group than that in the control group. Nedaplatin has a possibility to result in mild nausea/vomiting. CONCLUSION: Nedaplatin is an effective platinum drug in the treatment of NSCLC, not only for no previously chemotherapy patients, but also for those patients resistant to cisplatin/carboplatin. Nedaplatin has a good clinical tolerance. And the main adverse reaction was myelosuppression, especially thrombocytopenia.

Adult↗

PubMed2002

[Interspecific and intraspecific comparison of valepotrates contents in three Valeriana plants].

OBJECTIVE: To compare the contents of three valepotrates intraspecifically and intraspecifically in three medicinal Valeriana plants grown in different areas in China. METHODS: The method of RE-HPLC was adopted. RESULTS: The results showed that the contents of three valepotriates in Valeriana jatamansi Jones, V. officinalis L. and V. officinalis var. latifolia Miq. were different. Among them, that of Valeriana jatamansi Jones was the highest. The contents of three valepotrates in Valeriana jatamansi Jones varied significantly from different areas, samples collected from Longli of Guizhou province ranking the highest. The contents of three valepotriates in V. officnalis L. also varied significantly from different areas, samples from Liuba of Shaanxi province showing the highest. The results also showed that the contents of three valepotriates in underground part are all higher than that in aerial part. CONCLUSION: The interspecific and intraspecific differences of valepotriates in three Valeriana plans were obvious.

Chromatography, High Pressure Liquid↗

PubMed2002

[Study on the biological character of liposome-mediated 99m-technetium labeled antisense oligonucleotide for c-myc mRNA].

OBJECTIVE: To probe the biological character of liposome-mediated 99m-technetium-labeled antisense oligonucleotide of c-myc mRNA, and lay the foundations for clinical research on antisense image or treatment. METHODS: Antisense, sense and scrambled oligonucleoyide, each containing 15 bases, were synthesized elsewhere. The rates of liposome-entrapped 99mTc-DNA and 99mTc-DNA combination with plasma protein were tested through trichloroacetic acid precipitation. BALB/c mice were used to test the biodistribution in vivo, and rabbits were used to investigate the pharmacokinetics characters. RESULTS: Their rates of combination with plasma protein ranged from 34.81% to 70.53%. Reticuloendothelial system played an important role in the biodistribution; stomach, blood and intestines were less important; other tissues accumulated the least of the liposome-mediated 99mTc-labeled c-myc oligonucleotides. The pharmacokinetics of liposome-entrapped 99mTc-DNA fitted the open dithecal model. Their distribution (t1/2 alpha) half time was about 2 to 5 minutes, and clearance (t1/2 beta) half time about 100 to 150 minutes. Plasma clearance was smaller than 2 ml/min. CONCLUSION: The rate of 99mTc-DNA combination with plasma protein was high. The biological half time of liposome-mediated 99mTc-DNA was proper. Plasma clearance was high. So liposome-mediated 99mTc-DNA is a potential kind of radioactive agent.

Animals↗

PubMed2002

[A study on morphology and distribution of mast cells in oral lichen planus].

OBJECTIVE: The aim of this study was to investigate the features of mast cell subtypes and relationship between mast cells and pathogenesis of oral lichen planus. METHODS: Mast cells in the tissue of oral lichen planus were stained with Alcian blue/safranine in order to demonstrate mature and immature mast cells, and the constituent ratio of these two subtypes was calculated. Afterwards, LUZEX-F image pattern analysis system was applied to demonstrate the size of these two subtypes and their morphological features. RESULTS: The constituent ratio of mature and immature types of mast cells in the tissue of oral lichen planus was significantly different from that in the normal tissue (P < 0.01), and such difference was also demonstrated among different types of this malady, including papule-, net- and erosion-type of oral lichen planus (P < 0.05). There was significant difference between the sizes of mature and immature mast cells (P < 0.01) and also the sizes, amount and distribution of the plasma granules within these two mast cells. CONCLUSION: It could be implied that mast cells might play a role in the pathogenesis of oral lichen planus.

Adult↗

PubMed2002

[Screening of antimitotic portions from sea hare using conidia of Pyricularia Oryzae].

OBJECTIVE: To apply conidia of Pyricularia Oryzae to the screening of antimitotic constituents from marine animal sea hare. METHOD: To extract and fractionate active portions from sea hare through detecting deformation of mycelia germinated from conidia of P. Oryzae P-2b, in comparison with the cytotoxic test results in vitro. RESULT: Two active portions, of which IC50 against P388 and HL-60 was 23.4, 18.6 and 19.4, 12.5 micrograms.ml-1, respectively, were screened from this animal. CONCLUSION: This bioassay method was efficiently applied to the primary screening of antimitotic portions from marine animals for the first time. Being convenient, speedy and cheap, the screening model is suitable for the bioassay of active constituents from marine life.

Animals↗

PubMed2002

[Treatment for chronic dacryocystitis by dacryocystorhinotomy with Ho: YAG laser under endoscope].

OBJECTIVE: To analyze the experience and curative effect in treating chronic dacrocystitis by dacryocystorhinotomy with Ho:YAG laser under endoscope. METHOD: 20 patients of chronic dacryocystitis were treated by dacryocystorhinotomy with Ho:YAG laser under endoscope, followed-up for 1 approximately 2 years to observe the curative effects. RESULT: One was unplugged 8 months after the operation, six after 6 months, four after 4 months and nine after 3 months. No recidivations was found one year after the operation and the effective rate was 100%. There was no complications in all of the cases. CONCLUSION: The technique of dacryocystorhinotomy with Ho: YAG laser under endoscope overcomes the disadvantages of traditional method of operation.

Adult↗