Biomedical subjects

X Shi

Publications and source records attributed to X Shi.

At least 109 records · Page 6Linked to original sources

PubMed2001

Cr (VI) increases tyrosine phosphorylation through reactive oxygen species-mediated reactions.

While Cr (VI)-containing compounds are well established carcinogens, the mechanisms of their action remain to be investigated. In this study we show that Cr (VI) causes increased tyrosine phosphorylation in human lung epithelial A549 cells in a time-dependent manner. N-acetyl-cysteine (NAC), a general antioxidant, inhibited Cr (VI)-induced tyrosine phosphorylation. Catalase, a scavenger of H2O2, sodium formate and aspirin, scavengers of hydroxyl radical (*OH), also inhibited the increased tyrosine phosphorylation induced by Cr (VI). SOD, an inhibitor of superoxide radical (O2*-), caused less inhibition. ESR study shows that incubation of Cr (VI) with the A549 cells generates *OH radical. The generation of radical was decreased by addition of catalase and sodium formate, while SOD did not have any inhibitory effect. Oxygen consumption measurements show that addition of Cr (VI) to A549 cells resulted in enhanced molecular oxygen consumption. These results indicate that Cr (VI) can induce an increase in tyrosine phosphorylation. H2O2 and *OH radicals generated during the process are responsible for the increased tyrosine phosphorylation induced by Cr (VI).

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

On the mechanism of Cr (VI)-induced carcinogenesis: dose dependence of uptake and cellular responses.

Cr (VI) compounds are widely used industrial chemicals and are recognized human carcinogens. The mechanisms of carcinogenesis associated with these compounds remain to be investigated. The present study focused on dose-dependence of Cr (VI)-induced uptake and cellular responses. The results show that Cr (VI) is able to enter the cells (human lung epithelial cell line A549) at low concentration (< 10 microM) and that the Cr (VI) uptake appears to be a combination of saturable transport and passive diffusion. Electron spin resonance (ESR) trapping measurements showed that upon stimulation with Cr (VI), A549 cells were able to generate reactive oxygen species (ROS). The amount of ROS generated depended on the Cr (VI) concentration. ROS generation involved NADPH-dependent flavoenzymes. Cr (VI) affected the following cellular parameters in a dose-dependent manner, (a) activation of nuclear transcription factors NF-kappaB, and p53, (b) DNA damage, (c) induction of cell apoptosis, and (d) inhibition of cell proliferation. The activation of transcription factors was assessed by electrophoretic mobility shift assay and western blot analysis, DNA damage by single cell gel electrophoresis assay, cell apoptosis by DNA fragmentation assay, and cell proliferation by a non-radioactive ELISA kit. At the concentration range used in the present study, no thresholds were found in all of these cell responses to Cr (VI). The results may guide further research to better understand and evaluate the risk of Cr (VI)-induced carcinogenesis at low levels of exposure.

Antioxidants↗

PubMed2001

Arsenic-induced NFkappaB transactivation through Erks- and JNKs-dependent pathways in mouse epidermal JB6 cells.

Tumor promoting effects of arsenic are believed to be associated with its transactivation activity on transcription factors, such as AP-1 and NFkappaB. However, the results from different groups studying the effects of arsenic on NFkappaB activation are contradictory in different cell models. Since arsenic is a strong skin carcinogen, we have investigated the activation of NFkappaB by arsenic in a mouse skin epidermal cell line, JB6 cells. Exposure of cells to arsenite or arsenate led to NFkappaB transactivation in mouse epidermal JB6 NFkappaB-luciferase reporter stable transfectants, C141 NFkappaB mass1. This induction of NFkappaB activity by arsenic was dose- and time-dependent. The transactivation of NFkappaB by arsenic appeared to be through activation of Erks and JNKs pathways because increased NFkappaB activity by arsenic could be dramatically inhibited by either pre-treatment of cells with PD98059 or overexpression of dominant negative JNK1. That Erks activation is required for arsenic-induced NFkappaB transactivation was further supported by the findings that arsenic-induced NFkappaB transactivation was impaired in JB6 30.7b cells, which were deficient in Erks.

Animals↗

PubMed2001

Molecular mechanisms of metal toxicity and carcinogenesis.

Many metals and metal-containing compounds have been identified to be potent mutagens and carcinogens. Recently, a new sub-discipline of molecular toxicology and carcinogenesis has been developed. The combination of newly developed molecular techniques and free radical approach makes it possible to insightfully examine metal-induced carcinogenesis in precise molecular terms so that intricate biological interrelationships can be elucidated. In consideration of the increased amount of new findings deciphered by utilizing these new methods, the 1st Conference on Molecular Mechanisms of Metal Toxicity and Carcinogenesis was held. In this conference, more than 50 scientists from nine countries presented their novel discoveries concerning metal-induced carcinogenesis, delineated molecular mechanism of metal carcinogenesis, and proposed novel therapeutic intervention and prevention strategies. This article reviews some of the state-of-the-art information presented at the meeting regarding the molecular mechanisms of metal cytotoxicity and carcinogenesis.

Apoptosis↗

PubMed2001

In vivo reduction of chromium (VI) and its related free radical generation.

Chromium (VI) compounds are widely recognized as human carcinogens. Extensive studies in vitro and in model systems indicate that the reactive intermediate, Cr (V), generated by cellular reduction of Cr (VI), is likely the candidate for the ultimate carcinogenic form of chromium compounds. Here we review our current understanding of the in vivo reduction of Cr (VI) and its related free radical generation. Our results demonstrate that Cr (V) is indeed generated from the reduction of Cr (VI) in vivo, and that Cr (V) thus formed can mediate the generation of free radicals. Cr (V) and its related free radicals are very likely to be involved in the mechanism of Cr (VI)-induced toxicity and carcinogenesis. These studies also illustrate that in vivo EPR spectroscopy and magnetic resonance imaging can be very useful and powerful tools for studying paramagnetic metal ions in chemical and biochemical reactions occurring in intact animals.

Animals↗

PubMed2001

Cr (VI) induces cell growth arrest through hydrogen peroxide-mediated reactions.

Cr (VI) compounds are widely used in industries and are recognized human carcinogens. The mechanism of carcinogenesis associated with these compounds is not well understood. The present study focused on Cr (VI)-induced cell growth arrest in human lung epithelial A549 cells, using flow cytometric analysis of DNA content. Treatment of the cells with Cr (VI) at 1 microM caused a growth arrest at G2/M phase. An increase in Cr (VI) concentration enhanced the growth arrest. At a concentration of 25 microM, Cr (VI)-induced apoptosis became apparent. Superoxide dismutase (SOD) or sodium formate did not alter the Cr (VI)-induced cell growth arrest. While catalase inhibited growth, indicating H2O2 is an important mediator in Cr (VI)-induced G2/M phase arrest. Electron spin resonance (ESR) spin trapping measurements showed that incubation of cells with Cr (VI) generated hydroxyl radical (*OH). Catalase inhibited the *OH radical generation, indicating that H2O2 was generated from cells stimulated by Cr (VI), and that H2O2 functioned as a precursor for *OH radical generation. The formation of H2O2 from Cr (VI)-stimulated cells was also measured by the change in fluorescence of scopoletin in the presence of horseradish peroxidase. The mechanism of reactive oxygen species generation involved the reduction of molecular oxygen as shown by oxygen consumption assay. These results support the following conclusions: (a) Reactive oxygen species are generated in Cr (VI)-stimulated A549 cells through reduction of molecular oxygen, (b) Among the reactive oxygen species generated, H2O2 played a major role in causing G2/M phase arrest in human lung epithelial cells.

Antioxidants↗

PubMed2001

[Experience in surgical treatment of 110 patients with craniopharyngiomas].

OBJECTIVE: To study the effective method for surgical treatment of craniopharyngioma. METHODS: 110 patients with craniopharyngioma were operated on. Their tumors were totally removed. Of the 110 patients, 62 were male and 58 female, with age ranging from 15 to 67 years (mean 34.4 years). Pterional approach was performed in 102 patients, subfrontal approaches in 5, and transcallosum into the anterior third ventricle part in 3. The perforating arteries from the carotid, posterior and anterior communicating and anterior choroidal arteries to the hypothalamic structures were preserved when the tumors were excised by pterional approaches via the parachiasmal opticocarotid, carotidotentorial spaces and by opening the lamina terminals. The neural structures of the third ventricular floor were preserved by the transcallosum approach to the anterior part of the third ventricular floor. The cystic fluid was initially aspirated from cystic tumors, solid portion of the tumor was excised by piecemeal and calcification mass was crushed for removal. RESULTS: Of the 110 patients, 101 had a total removal of tumor, 7 a subtotal removal of tumor, and 3 a partial removal of tumors. The pituitary stalk was preserved in 57 patients, ruptured in 29, and unidentified in 24. In 54 patients with diabetes insipidus after surgery, 52 recovered from 3 months to one year after surgery and only two patients failed to over one year after surgery. 52 patients had normal blood sodium level 3 months after surgery. Three patients after surgery had decreased visual acuity. In 3 patients with oculomotor paralysis after surgery, one failed recover till one year. Two patients after surgery had temporal paralysis of the extremities. All the patients after surgery were followed up for one month to five years (mean, 1.1 years). Four patients died after surgery. CONCLUSIONS: The proper surgical approaches for the removal of craniopharyngiomas are the key to achieve good surgical results and avoid the injury to the hypothalamic structures and the perforating arteries to hypothalamus.

Adolescent↗

PubMed2001

[A comparative study of friction behaviour matching of natural tooth and new type dental prosthetic materials--titanium].

New type dental prosthetic materials Titanium not only have excellent biocompatibility, better corrosion resistance, appropriate hardness, light density approaching to human skeleton, but also good mechanical properties as those of type II, IV gold alloy recommended by ADAS, and their strength to weight ratio is 1.3 times that of aluminum, 1.5 times that of steel. Friction wear comparative tests of natural living teeth and dental Titanium materials have been carried out against Gr15 steel ball. A reciprocating movement was realized at the modified machine of fretting to simulate the pair of real tooth. The main test parameters were: slip amplitude 500 microns, normal load 20 N, frequency 2 Hz, and number of cycles 5000. The wear behavior results show that titanium is comparatively a prospective dental materials for restoration.

Child↗

PubMed2001

[Autoantibodies against the myocardium beta 1-adrenergic and M2-muscarinic receptors in patients with heart failure].

OBJECTIVE: To determine whether the autoantibodies against beta(1)-adrenergic and M(2)-muscarinic receptors are related to congestive heart failure (CHF) patients with different cardiac diseases. METHODS: Both synthetic peptides corresponding to amino acids sequence of the second extracellular loops of the beta(1) and M(2) receptors were used as the antigens to screen the serum from CHF patients with ischemic cardiomyopathy (ICD, n = 42), idiopathic dilated cardiomyopathy (IDCM, n = 52) and hypertensive heart disease (HHD, n = 44). Meanwhile healthy donors were tested as normal controls (NC, n = 40). RESULTS: The positive rates of serum for beta(1)-adrenergic-receptor were 45.7% (86/188) and 10.4% (8/77) in CHF patients and controls respectively (P < 0.01); the positive rates of serum for M(2)-muscarinic receptor were 52.7% (99/188) and 11.7% (9/77) in CHF patients and controls (P < 0.01). The frequencies of the both receptor autoantibodies in patients with cardiac function of class II approximately III were significantly higher than those with cardiac function of class VI. CONCLUSIONS: Our finding indicates indicates that autoantibodies against beta(1)-adrenergic-receptor and M(2)-muscarinic receptor can be detected not only in the serum of CHF patients with IDCM, but also in CHF patients with ICM and HHD. It is suspected that autoantibodies against beta(1) and M(2) receptors may be related to the myocardial remodeling and/or CHF.

Adult↗

PubMed2001

[Abdominal tuberculosis misdiagnosed as tumor].

OBJECTIVE: To evaluate the clinical and pathological features of abdominal tuberculosis (TB) in order to establish correct diagnosis. METHODS: Forty-five cases of abdominal TB, which were clinically misdiagnosed as tumor (misdiagnosed as malignant tumor in 31 cases) between 1962 and 1997 were reviewed. The diagnosis was confirmed histopathologically after the operation. RESULTS: Most of the patients with abdominal TB were young in age (< 40 years in 29 cases, 64%) and females (28 cases, 62%). The main clinical manifestations were abdominal mass (37 cases, 82%), abdominal pain (30 cases, 67%), fever (17 cases, 38%), abdominal distension, constipation or diarrhea (15 cases, 33%) and weight loss (14 cases, 29%). The finding during operation showed multiple massive lesions involving intestine, peritoneum and lymph nodes in all the cases, which mimicked those with abdominal tumor. Under microscopy, proliferative type of lesions were found in 29 cases, caseous necrosis type in 11 cases and mixed type in 5 cases. CONCLUSIONS: It is showed that the clinical manifestations of abdominal TB mimic those in abdominal tumor. It is recommended that clinicians should improve understanding of clinical and pathological features of the abdominal TB and that exploratory laparotomy biopsy should be performed on those with suspected abdominal TB.

Abdominal Neoplasms↗

PubMed2001

Retrospective study of mechanical ventilation in treating multiple trauma accompanied with craniocerebral injury.

OBJECTIVE: To explore the importance of mechanic al ventilation (MV) in treating multiple trauma mainly accompanied with cerebral injury and improve the treatment level. METHODS: All 116 patients who suffered from multiple trauma accompanied with mainly cerebral injury were analyzed. Rank correlation and Chi-square test were made between MV with GCS, ISS, and whether shock or not. RESULTS: The MV was correlated with GCS, ISS scores, and whether shock or not markedly. Furthermore, when GCS or=35, the ratio of MV was about 85%. CONCLUSIONS: During the treatment of multiple trauma accompanied with cerebral injury, the principle of "early MV, early withdraw" and "individualism" should be insisted on. For patients accompanied with shock, the optimum PEEP is very important. Proper and active MV is of great importance and can improve the treatment level markedly.

Adolescent↗

PubMed2001

[Phacoemulsification of the subluxated lens with cataract].

OBJECTIVE: To study the efficiency of phacoemulsification in the treatment of subluxated lens with cataract. METHOD: Phacoemulsification combined with intraocular lens implantation was performed on 19 eyes of 18 patients. RESULT: The visual acuity in 18 eyes was improved to different degrees. The visual acuity in one eye was not improved due to the preoperative macular contusion. CONCLUSION: Phacoemulsification for treatment of subluxated lens with cataract may decrease many complications occurring in the past procedure.

Adult↗

PubMed2001

[A study on the bond interface between low-fusing dental porcelain and pure titanium].

OBJECTIVE: To evaluate the bond interface between low fusing dental porcelain and pure titanium by observing the topography and detecting the ionic diffusion in the interface area. METHODS: The low fusing-porcelain La-porcelain produced by the authors or Vita Titankeramik porcelain was fused to the surfaces of pure titanium. The topography of the interface between pure titanium and porcelain, and the structure of experimental materials were observed with SEM. The state of ionic diffusion in the interface area was investigated with EPMA. RESULTS: Excellent permeation and diffusion of La-porcelain were observed on the surfaces of pure titanium. The diffusion of ions of stannum and silicon was discovered in the interface area. The microstructure of La-porcelain to pure titanium bond interface was finer than that of Vita Titankeramik porcelain. CONCLUSION: Excellent bond can be produced in the interface between La-porcelain and pure titanium. The bonding mechanism may involve mechanical bond and chemical bond. The ionic diffusion of stannum plays an important role in the bonding of porcelain to pure titanium.

Dental Alloys↗

PubMed2001

[The influences of crystallized compositions in the porcelain on bonding strength of titanium to porcelain].

OBJECTIVE: Sufficient porcelain-titanium bond is a vital factor determining the clinical performance of titanium-porcelain restorations. The purpose of this study was to investigate the effects of self-preparation La-porcelain composition on the porcelain-titanium bonding strength and to compare with the Vita Titankeramik. METHODS: The present study examines 5 different recipes of porcelain by weight%: SiO2, 12%-17%; LaO2, 7%-10%; Al2O3, 9%-14%; B2O3, 23%-31%; CaO, 6%-8%; K2O, 2%-3%; SrO, 2%-4%; Na2O, 1%-3%; SnO2, 8%-10%; ZrO2, 3%-5%; TiO2, 6%-8%. Specimens were tested in push type shear with a universal testing machine. Scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA) were employed to reveal the microstructures and diffusion of elements in the interfacial regions between the porcelain coating and titanium to the bond strength when fired at 800 degrees C. RESULTS: The ratios of crystallized compositions had significant influences on the porcelain-titanium bond strength (P < 0.05). La-porcelain had the highest shear bond strength (37.76 MPa). The shear bond strength of the Vita Titankeramik to titanium was 20.18 MPa. The results of SEM revealed integrity of porcelain-titanium joints in La-porcelain and a greater amount of porosity in the interface of Vita Titankeramik to titanium. EPMA analysis demonstrated the aggregation of Si and Sn in the interfacial regions and their diffusion into the titanium. CONCLUSION: Chemical compositions of porcelain and ratios of crystallized compositions play the important role in the titanium porcelain bond. La-porcelain had the highest shear bond strength and good porcelain-titanium joints. La-porcelain is a new-style low fusing porcelain/titanium system.

Crystallization↗

PubMed2001

[Purification and properties of neutral phytase form Bacillus subtilis].

A strain Bacillus subtilis producing neutral phytase was screened from soil. The protein of phytase was purified by HPLC. Optimal pH value and temperature of the phytase for its activity were 7.5 and 55 degrees C, respectively. The Km values of the phytase for dodecasodium phytate under 37 degrees C was 0.19 mmol/L. The molecule weight of the phytase protein was determined as about 45 kD by SDS-PAGE. The N-terminal amino acids sequence of the phytase protein was determined as Lys-His-Lys-Leu-Ser-Asp-Pro-Tyr-His-Phe-Thr by amino acids sequence analysis.

6-Phytase↗

PubMed2001

Preservation of the hypothalamic structures in the total resection of craniopharyngioma.

OBJECTIVE: To explore an effective method of surgical management of craniopharyngioma. SUBJECTS AND METHODS: Fifty patients with craniopharyngioma had total and subtotal tumor ectomy. There were 29 males and 21 females, ranging in age from 15 to 56 years (mean 34.1 years). MR imaging showed that the tumors were located in the superior sellar region in 24 cases, in superior sella region and extended into the third ventricular floor in 19 cases, into parasella in 3 cases and down to intrasella in 4 cases. Complete cystic tumors were found in 5 cases, while the partial cystic tumor in 24 cases and complete solid tumors in 21 cases. Pterional approach was used in 48 patients and subfrontal approach in 2 patients. Great attention was paid to the preservation of the perforating arteries from the carotid, posterior and anterior communicating and anterior choroidal arteries to the hypothalamic structures. The clinical outcome was evaluated according to the GOS scale. RESULTS: Of the 50 patients surgically treated, 47 patients obtained total ectomy of the tumor and 3 patients with the secondary surgery had subtotal ectomy of the tumor. The pituitary stalk was preserved in 29 (58%) patients, severed in 14 patients and unidentified in 7 patients. Forty-six patients regained a normal life; one patient needed assist in life. Of the 3 deaths, one patient died of diabetes insipidus, one of inhalation asphyxia, and another one of water and sodium disorders. CONCLUSION: Avoidance of the injury to the neural structures in the third ventricular floor and preservation of the perforating arteries to hypothalamus are the key to achieve good surgical results in treating craniopharyngioma.

Adolescent↗

PubMed2001

[Eukaryotic expression and in vitro tumor cell apoptosis-induced effect of human TRAIL].

OBJECTIVE: To explore the tumor cell apoptosis induced by the effect in vitro of eukaryotic expression of full-length TRAIL cDNA and its extracellular region. METHODS: The eukaryotic expression vectors for both forms of the cDNA acquired from the fetal heart cDNA library were constructed. After gene transfecting, the stable expression cell lines were obtained by G418 screening. RESULTS: The supernatants from tansfectants could induce apoptosis of different tumor cell lines in vitro, and an enhanced effect was observed by adding TFAR19 (TF-1 cell apoptosis-related protein 19), a novel apoptosis gene product discovered in our laboratory. CONCLUSION: Eukaryotic expression products of TRAIL can induce apoptosis of the tumor cells, and TFAR19 could enhance the effect on apoptosis of tumor cells.

Animals↗

PubMed2000

Induction of activator protein-1 through reactive oxygen species by crystalline silica in JB6 cells.

We reported previously that freshly fractured silica (FFSi) induces activator protein-1 (AP-1) activation through extracellular signal-regulated protein kinases (ERKs) and p38 kinase pathways. In the present study, the biologic activities of FFSi and aged silica (ASi) were compared by measuring their effects on the AP-1 activation and phosphorylation of ERKs and p38 kinase. The roles of reactive oxygen species (ROS) in this silica-induced AP-1 activation were also investigated. We found that FFSi-induced AP-1 activation was four times higher than that of ASi in JB6 cells. FFSi also caused greater phosphorylation of ERKs and p38 kinase than ASi. FFSi generated more ROS than ASi when incubated with the cells as measured by electron spin resonance (ESR). Studies using ROS-sensitive dyes and oxygen consumption support the conclusion that ROS are generated by silica-treated cells. N-Acetylcysteine (an antioxidant) and polyvinyl pyridine-N-oxide (an agent that binds to Si-OH groups on silica surfaces) decreased AP-1 activation and phosphorylation of ERKs and p38 kinase. Catalase inhibited phosphorylation of ERKs and p38 kinase, as well as AP-1 activation induced by FFSi, suggesting the involvement of H(2)O(2) in the mechanism of silica-induced AP-1 activation. Sodium formate (an ( small middle dot)OH scavenger) had no influence on silica-induced MAPKs or AP-1 activation. Superoxide dismutase enhanced both AP-1 and MAPKs activation, indicating that H(2)O(2), but not O(2), may play a critical role in silica-induced AP-1 activation. These studies indicate that freshly ground silica is more biologically active than aged silica and that ROS, in particular H(2)O(2), play a significant role in silica-induced AP-1 activation.

Animals↗