Biomedical subjects

Z Li

Publications and source records attributed to Z Li.

At least 379 records · Page 21Linked to original sources

PubMed2001

[Isolation, purification and renaturation of recombinant-DNA-derived porcine somatotropin].

Large scale abstraction and isolation of bacterially synthesized, recombinant-DNA-derived, porcine growth hormone (r-pST) is described. The r-pGH is found in genetic engineering E. coli as the form of inclusion bodies. Pellet fraction which were mainly inclusion bodies, after cell breakage and centrifugation, were collected. Cell envelope components, such as protein, lipid, endotoxin and nucleic acids are selectively removed from the pellet fraction by an EDTA/lysozyme/deoxycholate extraction. Inclusion bodies were dissolved using 6 mol/L guanidine/HCl and air oxidation is then carried out in the presence of the guanidine/HCl. The Guanidine/HCl protein mixture were diluted by renaturation solution. Guanidine/HCl were removed by dialysis and then correctly refolded, oxidized r-pGH were obtained. Injection experiment of hypophysectomized rats proved r-pST with high native bioactivity was obtained.

Animals↗

PubMed2001

[Influence of oral administration of realgar on contents of copper, zinc and selenium in rat tissues].

OBJECTIVE: To investigate the changes of copper, zinc and selenium levels in rat tissues after long-term oral administration of Realgar. METHODS: Rats were given Realgar with dosage of 50, 150, 450 mg.kg-1.d-1 for 5 weeks, and the concentrations of copper, zinc and selenium in different rat tissues as well as the contents of metallothionein in rat liver and kidney were determined with atomic absorption and hydride generation-atomic fluorescent technique. The total amount of copper excreted from feces and urine of each rat 5 days before the rat was killed was also measured. RESULTS: No significant changes of levels of copper, zinc and selenium in rat tissues were found after administration of low and middle dosages of Realgar. But higher dosage (450 mg.kg-1.d-1) of Realgar administration could induce a small but significant decrease of zinc concentration in hearts and a increase of copper contents in spleen and tibia, as well as twice more copper concentration of kidney. CONCLUSION: Copper deposit in kidney was the most significant change found among the trace elements levels in rat tissues, and this might be one of the mechanisms for kidney toxicity of Realgar.

Administration, Oral↗

PubMed2001

[Experimental study of the virus inhibitory effect of chuan-kang-ping granule].

OBJECTIVE: To explore the virus inhibitory effect of Chuan-Kang-Ping Granule. METHODS: Using tissue culture technique, the maximal non-toxic concentration of the drugs in Hep-2 cell culture were measured and the virus inhibitory index of the drugs on the respiratory syncytial virus (RSV), the coxackie B3 virus (Cox B3) and the influenza A1 virus (A1) was calculated. In addition, the degrees of inhibition of the drugs on the cytopathic effect of viruses in cell culture was observed by changing sequence of adding the viruses and the drugs. RESULTS: The maximal non-toxic concentration of Chuan-Kang-Ping Granule was 1:16. The virus inhibitory index on RSV, CoxB3, A1 was 8.8 and 2, respectively. The maximal non-toxic concentration of Shuang-Huang-Lian oral administration Liquid was 1:32. The virus inhibitory index on RSV, CoxB3, A1 was 8, 16 and 2, respectively. The degrees of cytopathic effect were different when changing sequence of adding the viruses and the drugs. CONCLUSION: Chuan-Kang-Ping Granule inhibited the replication of RSV, CoxB3, A1 in cultured cells. The inhibitory effect of the drugs were the same or nearly the same with Shuang-Huang-Lian oral administration liquid. The mechanism of the inhibitory effects of the drugs on the viruses was probably the direct killing effect in vitro, or the drugs might inhibit some key link of the replication of the viruses in cultured cells.

Antiviral Agents↗

PubMed2001

[Study on the expression of fibronectin after cerebral contusion in rats for timing of injuries].

An experimental model of reproducible focal cerebral contusions in rats was made by a free-drop impacting right hemisphere. The expression of fibronectin and its mRNA after cerebral contusion were detected respectively by immunohistochemical staining and in situ hybridization. Results indicated that the expression of fibronectin and its mRNA increased after injury, and there existed a relationship between increased fibronectin and its mRNA and different intervals after brain injury. It is inferred that the expression of fibronectin and its mRNA can be used for timing of brain injuries and distinguishing antemortem and postmortem brain contusions.

Animals↗

PubMed2001

[Effects of the mold temperature on the castability of titanium zirconium alloy for dental clinical use].

OBJECTIVE: The aims of this study were to investigate the influence of the mold temperature on the castability of Ti-Zr alloy and find out the reasonable method for casting Ti-Zr alloy in clinic. METHODS: Ti-Zr alloy, pure titanium and Ti-6Al-4V alloy were casted respectively, by using a mold made of a zircon (ZrO2.SiO2) investment and a casting machine (China) designed, with a program of vacuum, pressure and centrifuge casting at three mold temperatures (room temperature, 300 degrees C, 600 degrees C). The castability value was obtained by counting the complete segment of the cast alloy grid. The wax pattern provided a grid with 112 segments. The percentage of complete cast segments was calculated by divided by 112, and multiplied by 100. The mesh castability values of Ti-Zr alloy, pure titanium and Ti-6Al-4V alloy were examined. RESULTS: The castability of three titanium alloys was high when the mold temperature was high. The castability values of Ti-Zr alloy at three mold temperatures were 88.57% for the room temperature, 94.55% for 300 degrees C, and 96.67% for 600 degrees C. Ti-Zr alloy casted at the room temperature showed significantly lower castability value than that casted at 300 degrees C and 600 degrees C (P < 0.05), but no significant difference was found between the castability values of 300 degrees C and 600 degrees C (P > 0.05). The castability values of pure titanium at three mold temperatures were 95.33% for room temperature, 98.70% for 300 degrees C, and 98.90% for 600 degrees C. The castability values of Ti-6Al-4V alloy at three mold temperatures were 95.37% for room temperature, 96.00% for 300 degrees C, and 98.78% for 600 degrees C. When casted at room temperature, the castability values of Ti-Zr alloy were significantly decreased comparing with those of pure titanium and Ti-6Al-4V alloy (P < 0.05), but no significant difference was found when cast alloys were casted at 300 degrees C and 600 degrees C (P > 0.05). CONCLUSION: The mold temperature is one of the major factors influencing cast quality. This study suggests that in order to obtain high castability of dental Ti-Zr alloy castings in clinic, the optimal mold temperature should be higher than 300 degrees C.

Dental Alloys↗

PubMed2001

[Transverse deflection study of casted titanium zirconium alloy for dental clinic use].

OBJECTIVE: The aim of this study was to obtain the reasonable thickness of Ti-Zr alloy used for denture base material. METHODS: According to the "Revised ADA Specification No. 12 for denture base polymers", the transverse deflection tests of Ti-Zr alloy after casting were performed. Pure titanium, Ti-6Al-4V alloy and Co-Cr alloy were examined as the control. Three groups of wax patterns with different thickness were designed. Ti-Zr alloy, pure titanium and Ti-6Al-4V alloy were casted into molds at 300 degrees C, which were made of zircon (ZrO2.SiO2) investment, using a casting machine (China), with a program of vacuum, pressure and centrifuge casting. Co-Cr alloy was casted by normal method in clinic. The transverse deflections of these four alloys castings with three different thicknesses were measured using a transverse testing machine. RESULTS: When the thickness is 0.65 mm for Ti-Zr alloy, pure titanium and Ti-6Al-4V alloy, and 0.57 mm for Co-Cr alloy, the transverse deflections could satisfy the requirement. CONCLUSION: The transverse deflection is one of the key indexes for evaluating the ability of dental material to bear biting forces. The reasonable thickness of Ti-Zr alloy used as denture base material is 0.65 mm.

Dental Alloys↗

PubMed2001

[Expression of transforming growth factor beta(TGF-beta) subtypes in oral squamous cell carcinoma].

OBJECTIVE: The objective of this study was to determine the expression of transforming growth factor beta (TGF-beta) subtypes and their relationship with the mechanisms of squamous cell carcinoma (OSCC) growth. METHODS: Totally 40 cases of surgical specimens of OSCC resected between 1998 and 2000 and 20 cases of normal human oral mucosa were investigated. Strepto-adridinibiotin complex (SABC) immunohistochemical staining was used to analyze the expression of TGF-beta protein subtypes and their relations with clinical prognosis of OSCC. RESULTS: Semi-quantitative analysis revealed that the subtypes 1, 2 and 3 of TGF-beta protein could be found in OSCC cells and normal oral epithelial cells, however the intensity of protein expression was different. Comparing with those in normal oral mucosa epithelial cells, the subtypes 1 and 2 of TGF-beta were over-expressed in OSCC cells. The over-expression of subtypes 1 and 2 of TGF-beta protein were associated with their pathological grades, clinical stages and neck lymph node metastasis (P < 0.05), whilst the subtype 3 protein of TGF-beta was not. CONCLUSION: It will be useful to detect the expression of TGF-beta subtypes in OSCC, as the subtypes 1 and 2 of TGF-beta may play an important role in OSCC growth and metastasis.

Adult↗

PubMed2001

[The effects of MMPs and TIMPs on the metastasis of oral squamous cell carcinoma to neck lymph nodes].

OBJECTIVE: This study is aim at investigating the relationship between the expression and activity of MMP-2,9, TIMP-1,2 and the metastasis of oral squamous cell carcinoma to neck lymph node. METHODS: The expression of MMP-2,9, TIMP-1,2 in 30 oral squamous cell carcinoma, two oral squamous cell carcinoma cell lines GNM and TSCCa was detected by in situ hybridization; Zomography was performed to determined the activity of MMP-2,9 in cancer tissue and conditioned medium of GNM and TSCCa; Ability of invasion of GNM and TSCCa was measured with in vitro invasion assays. RESULTS: Both tumor cells and stroma expressed both MMP-2,9 and TIMP-1,2; It was found that MMP-2,9, TIMP-1,2 had a higher expression in patients with neck lymph node metastasis than those without metastasis (P < 0.05), positive percentage of MMP-2,9 in GNM was higher than that in TSCCa; The MMP-2,9 in node-positive patients was more active than in node-negative ones (P < 0.05); GNM had more active MMP-2, 9 and higher invasive potential than TSCCa. CONCLUSION: MMP-2,9 may play an important role in metastasis of oral squamous cell carcinoma; Elevation of TIMP-1,2 is likely to be the result of interaction of tumor and stroma.

Adult↗

PubMed2001

[Superoxide dismutase and cytokines in otitis media with effusion].

OBJECTIVE: To study the role of superoxide dismutase (SOD) and cytokines in the pathogenesis of secretory otitis media(SOM). METHOD: The content of SOD, interleukin-6(IL-6), interleukin-8(IL-8) and tumor necrosis factor alpha (TNF-alpha) in blood plasma and middle ear effusion (MEE) were measured in 64 (90 ears) patients respectively. RESULT: SOD, IL-6, IL-8 and TNF-alpha were found in 88.9%, 86.8%, 81.5% and 74.6% of MEI respectively. SOD, IL-6, IL-8 and TNF-alpha of blood plasma in SOM group were higher than those in normal control group (P < 0.05). The concentration of SOD, IL-6, IL-8 and TNF-alpha MEE was remarkably higher than that in blood plasma (P < 0.01). It revealed that the shorter the course, the higher the concentration of IL-6 or IL-8 in MEE (P < 0.01, or P < 0.05), and the longer the course, the higher the concentration of SOD or TNF-alpha in MEE (P < 0.01, P < 0.05). IL-6 and IL-8 concentration of MEE in serous fluid group was remarkably higher than those in the mucous fluid group (P < 0.01, P < 0.05), and the concentration of SOD and TNF-alpha of MEE in the mucous fluid group was higher than that in the serous fluid group (P < 0.01, P < 0.05). SOD Level of MEE was positively correlated with TNF-alpha (r = 0.587, P < 0.01). CONCLUSION: SOD, IL-6, IL-8 and TNF-alpha might be important mediators in MEE secretion in SOM. IL-6 and IL-8 might participate in the defensive reaction of organism during the early stages of SOM. SOD and TNF-alpha might be closely related to the persistence of SOM, and might be mediators of mucin secretion in SOM.

Adolescent↗

PubMed2001

[Clinical comparison of bilateral neck dissection for supraglottic carcinoma].

OBJECTIVE: In order to rise the survival rate and quality of life, the patients with bilateral neck dissection was investigated in supraglottic carcinoma. METHOD: 76 cases were retrospectively analyzed. In terms of clinical diagnosis, 33 cases who had bilateral neck metastasis had received simultaneously bilateral neck dissection. 43 patients first diagnosed unilateral neck metastasis got subsequent bilateral neck dissection. All of the patients were pathologically diagnosed. RESULT: The 3 and 5 year survival rates, in the 33 cases who had received simultaneous bilateral neck dissection, were 81.5% (22/27) and 61.5%(16/26) respectively, while in the other 43 cases, was 69.2%(27/39) and 27.8%(10/36) respectively. CONCLUSION: It is necessary for those patients who have suffered from supraglottic carcinoma with bilateral neck metastasis to have simultaneous bilateral neck dissections. Meanwhile, the preservation of bilateral internal jugular veins is the best choice, at least one should be preserved.

Adult↗

PubMed2001

[Experimental studies on antitumor effect by the new recombinant tumour necrosis factor and cyclophosphamide in nude mice bearing laryngeal carcinoma].

OBJECTIVE: We aimed at finding ideal biological treatment and regime for laryngeal carcinoma. METHOD: Nude mice model bearing laryngeal carcinoma were established using laryngeal carcinoma cell line (HEP-2). New recombinant human tumor necrosis factor (NrhTNF-alpha) and cyclophosphamide were administered locally or systemically, single or in combination. The microstructural and ultra-micro-structural changes of carcinoma after administration of NrhTNF-alpha were observed under light and electron microscopes. RESULT: 1. After treatment, the tumor showed hemorrhage, necrosis, regression, the survival time was prolonged. 2. More significant antitumor effect was observed when locally administered NrhTNF-alpha than intravenously administered of NrhTNF-alpha. 3. There is a notable synergistic antitumor effect by the combination use of NrhTNF-alpha and cyclophosphamide. 4. Microscopy showed that cell changes mostly took place in plasma especially in mitochondria and endoplasmic neticula. The mitochondria were highly bloated. Besides, some nuclei were condensed and fragmented resulted in cell death. CONCLUSION: These studies provide experimental basis for biological treatment of laryngeal carcinoma.

Administration, Topical↗

PubMed2001

[Study on the coagulation state of laryngeal cancer patients before and after operation].

OBJECTIVE: To explore the coagulation state of laryngeal cancer patients before and after operation. METHOD: The eight parameters of coagulant system of 46 laryngeal cancer patients were examined before operation, 1 day and 10 days after operation, and compared with control group. RESULT: The result suggests, anticoagulant activity decreased and fibrinolytic activity increased in laryngeal cancer patients before operation. Laryngectomy trauma may worsen the abnormality. With the incision of tumors and recovery from operation trauma, anticoagulant activity and fibrinolytic activity of the patients gradually returned to normal level. CONCLUSION: Coagulation disorders in laryngeal cancer patients had existed in a way. With operation trauma, it may worsen the abnormality. So anticoagulant and fibrinolytic systems of these patients should be taken seriously to prevent thrombosis and bleeding.

Adult↗

PubMed2001

[A study on expression of tumor necrosis factor alpha in middle ear cholesteatoma and its effect on bone destruction].

OBJECTIVE: To determine the expression and localization of tumor necrosis factor alpha (TNF-alpha) in human middle ear cholesteatoma and its effects on bone resorption. METHOD: The distribution of TNF-alpha in 18 cholesteatoma tissues and 8 normal external ear canal skin, facial skin and tympanic membrane were studied immunohistochemically with paraffin-embedded sections. RESULT: TNF-alpha was localized in the epithelium and connective tissue of cholesteatomas studied, particularly on basal and spinous cells and macrophages. The epithelium of normal external ear canal skin, facial skin and tympanic membrane was slightly stained. CONCLUSION: This study revealed significantly increased level of TNF-alpha in cholesteatoma tissues. TNF-alpha acts both directly, by causing bone erosion as an autocrine growth factor, and indirectly as an important mediator by stimulating the release of enzymes causing bone destruction.

Adolescent↗

PubMed2001

[Primary restoration for congenital malformation of external and middle ear].

OBJECTIVE: To promote the hearing, improve the appearance, shorten the therapeutic course in congenital malformation of external and middle ear, the program of primary restoration has been designed. METHOD: Under general or local anaesthesia a Z-shaped incision is made in skin. After turn up the flap A (defective ear) and flap B(retroauricular skin), a periosteal flap C with pedicle in front is made and elevated from mastoid. Then made frameworklize on mastoid and perform tympanoplasty. Once the myringograft is put properly the flap C is turn into the mastoidal cavity to serve as the lining of anterior wall. Flap A is sutured with the edge of retroauricular incision to serve as the lower part of new auricle. Then use the flap B to wrap a siliceous frame to make the upper part of new auricle. Finally, the naked walls of mastoidal cavity are lined with free skin graft and the cavity is packed with vaseline gauze for two weeks. RESULT: Two cases of congenital malformation of external and middle ear were treated with the procedure mentioned above and were followed up for one and 3 years respectively. Both effects of shape and hearing were good. CONCLUSION: The primary restoration for congenital malformation of external and middle ear designed by the authors is an excellent method worthy to be recommended.

Adolescent↗

PubMed2001

[Appraisement of the operative therapeutical effects of salpingocatheterism for refractory otitis media].

OBJECTIVE: The therapeutical effects of salpingocatheterism and the states of tubal function were studied after different middle ear operations and within different middle ear pathological changes. METHOD: Total 71 patients with tubal occlusion, 18 of myringoplasty, 20 of reconstruction of ossicolar chain followed tympanoplasty, 14 of combined approach tympanoplasty, 10 of radical mastoidectomy followed tympanoplasty, 9 of re-radical mastoidectomy followed tympanoplasty were implemented salpingocatheterism. The patients were followed up for evaluation of the postoperative therapeutical effects and the state of tubal function. RESULT: The causes of operation failure in different middle ear operations or different middle ear pathological changes had no significantly difference. The major cause for postoperative tympanic membrane perforation and tubal occlusion was the pathogenic damage being not cleared up thoroughly and/or there being nasal cavity or pharyngeal cavity pathogenic changes accompanied. CONCLUSION: Salpingocatheterism is effective for preventing eustachian tube postoperative adhesion.

Adolescent↗

PubMed2001

[Determination of polyphenols in tobacco by solid phase extraction and high performance liquid chromatography].

A high performance liquid chromatographic (HPLC) method for the determination of polyphenols in tobacco was studied. Polyphenols can be extracted from tobacco sample by refluxing with 80% (volume fraction) methanol, then subjected to degrease by solid phase extraction with Sep-Pak-C18 column. Chlorogenic acid, rutin, scopoletin, caffeic acid, scopolin and other polyphenols can be separated on a Nova-Pak-C18 column (3.9 mm i.d. x 150 mm) gradiently eluted with methanol and 0.05 mol.L-1 potassium dihydrogen phosphate buffer solution as mobile phase at a flow-rate of 0.5 mL.min-1. Polyphenols were determined at the maximum wavelength of each polyphenol, for chlorogenic acid 326.1 nm, rutin 354.8 nm, scopoletin 344.0 nm, caffeic acid 323.7 nm and scopolin 365.2 nm by photodiode array detector. The main polyphenols in tobacco can be identified with UV spectroscopy. The recoveries of tobacco polyphenols were 94%-105%, and the relative standard deviations were 1.28%-1.49%. This method can be applied to the determination of polyphenols in tobacco with satisfactory results.

Chromatography, High Pressure Liquid↗

PubMed2001

[Screening and characteristics of mutants of E. coli resistant to acetate inhibition].

Acetate is accumulated in the aerobic high cell density culture of Escherichia coli, Which seriously inhibits cell growth and expression of recombinant proteins. To alleviate acetate inhibition, mutants of E. coli JM101 were generated by 60Co radiation and then enriched in continuous culture with acetate as the selective pressure. One of the mutants isolated, JL3, showed obvious increased tolerance toward acetate and maintained phenotypic stability on slant without acetate. In MA medium containing 10 g/L of sodium acetate, the specific growth rate and the glucose consumption rate of JL3 were higher than those of JM101.

Cobalt Radioisotopes↗

PubMed2001

[Expression of thyrotropin-releasing hormone receptor mRNA in the rat testis development].

In order to investigate the regulation of thyrotrophin-releasing hormone receptor (TRH-R) expression in rat testis, and to study their function in spermatogenesis, oligonucleotide primers were designed from the sequences of rat pituitary TRH-R cDNA for reverse transcription-polymerase chain reaction (RT-PCR). Specific fragments of TRH-R cDNA were cloned. DNA sequence analysis indicated that cDNA sequence of TRH-R from rat testis was consistent with those of pituitary TRH-R cDNA. The non-radioactive in situ hybridization (NR-ISH) technique was applied to localize cells encoding TRH-R mRNA in the rat testis. Hybridization signals were detected exclusively in the leydig cells, but not in the spermatogenetic cells of the rat testis. TRH-R mRNA in the testis was quantitated in RNA samples prepared from rats at different developmental stages by real time quantitative RT-PCR. The quantitative analyses demonstrated that no TRH mRNA could be detected at the earliest stage (day 8). TRH mRNA signals were detected on day 15 and increased progressively on day 20, 35, 60 and 90. These results suggested that rat testis could specifically express TRH-R, and the transcription of TRH-R gene in the rat testis was development-dependent.

Animals↗