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Biomedical subjects

X Tian

Publications and source records attributed to X Tian.

At least 109 records · Page 6Linked to original sources
PubMed1997

Synthesis and antitumor activity of spin labeled derivatives of podophyllotoxin.

Three new nitroxyl labeled derivatives of podophyllotoxin 4-6 have been synthesized and evaluated for their antitumor activity in vitro. Compounds 4-6 showed significant inhibitory activity against human nasopharyngeal carcinoma KB,lung cancer A549 and stomach carcinoma SGC-7901 cells, as well as mouse leukemia L1210 and P388 cells. Compounds 4 and 5 exhibited comparable or superior activity to clinically used etoposide (VP-16,2) in their inhibition of these cell lines.

Animals↗
PubMed1997

Antioxidative activity of 4-oxy- and 4-hydroxy-nitroxides in tissues and erythrocytes from rats.

AIM: To compare the activities of antioxidation of 4-oxy- and 4-hydroxy-nitroxides in tissues and RBC from rats. METHODS: The homogenates of liver, heart, and kidneys of rats were used to determine malondialdehyde (MDA) formation using TBA colorimetric method. H2O2-caused hemolysis was measured spectrometrically. Superoxide anion from zymosan-stimulated neutrophils of rats was assayed by NBT reduction method. RESULTS: Nitroxide free radicals OTMPO and HTMPO inhibited MDA generation caused by .OH generation system (MIC 10.5 and 21 mumol.L-1, respectively), antagonized hemolysis induced by H2O2 (MIC: 338 and 168 mumol.L-1, respectively), but did not affect O2- formation from activated neutrophils. 1-Hydroxyl compounds OTMPOH and HTMPOH possessed similarly potent antilipoperoxidative activities. But nonfree radical OTMP and HTMP had no effect on peroxidation of tissues. CONCLUSION: Nitroxides exert their antilipoperoxidative effect by specifically scavenging .OH free radicals in biological system. Trapping of .OH free radicals by nitroxides is not by reduction of NO. group in nitroxides. Both NO. group and NOH group are essential active groups.

Animals↗
PubMed1997

[Application of the myringoscope and myringophotography in forensice medical identification].

In analysis of tympanitio membrane injury, we have compared conventional otoscope with myringoscope and found that the myringoscope has an advantage over the conventional otoscope. The myringoscope can show the whole tympanitic membrane, the positions, shapes and characteristics of tympanitic membrane injuries more clearly. The pictures of myringophotography could be preserved and offered to court as an important forensic medical evidence.

Adult↗
PubMed1997

[Detection of flaviviruses by reverse-transcription polymerase chain reaction with universal primer set].

For the purpose of early and rapid diagnosis of flavivirus infection, the universal primer set was selected on the NS1 gene. Another five different internal primers were selected on the NS1 genes of DEN1, 2, 3, 4 and JEV. With the universal primer set designed, the NS1 fragment about the size of 413 bp and with the five internal primers, the NS1 fragments about the sizes of 262 bp (DEN1), 189 bp (DEN2), 392 bp (DEN3), 97 bp (DEN4) and 323 bp (JEV) were amplified respectively. The reverse transcription-polymerase chain reaction (RT-PCR) was used to amplify gene fragments of flaviviruses. cDNA of DEN1, 2, 3, 4 and JEV were successfully amplified with universal primer set and internal primers. Sera from 78 patients with dengue fever were assayed by nested PCR, DEN1 was detected from 18 of the 40 patients' sera and DEN2 was detected from 48 patients' sera. Sera from 42 patients with Japanese encephalitis were also assayed by nested PCR, JEV was detected from 35 of the 42 patients' sera. By nested PCR, we completed identification of flaviviruses within 2 days. The results showed that this method has the potential value in rapid clinical diagnosis of flavivirus infection.

DNA Primers↗
PubMed1997

[Changes of erythrocyte membrane lipid in hereditary G6PD deficiency].

OBJECTIVE: To explore the biochemical mechanism of G6PD deficiency. METHODS: A fluorescence polarization technique with 1,6-dipheny 1,1,3,5-heratciene (DPH) as a fluorescent probe was used to determine the fluidity of erythrocyte membrane lipid from G6PD deficient patients and normal controls. The polarization of fluorescence was measured between 0 degrees and 90 degrees. RESULTS: The fluorescence polarization parameter (rho) was high in G6PD deficient erythrocytes as compared with normal controls, indicating a decrease in erythrocyte membrane lipid fluidity. The determination of lipoperoxidation of erythrocyte membrane by fluorescence spectrometry also showed that the content of MDA was significantly higher in G6PD deficient erythrocytes than in normal controls. The percentage of unsaturated fatty acid C18:1 and C18:2 in total phosphalipids and phosphatidyl serine was decreased in G6PD deficient erythrocytes. CONCLUSION: The decrease of erythrocyte membrane lipid fluidity is related to the lipid peroxidant, and the oxidative damage of erythrocyte membrane phosphalipids in G6PD deficient patients might be an important factor of hemolysis.

Case-Control Studies↗
PubMed1997

Reduction of choline acetyltransferase mRNA in the septum of developing rat exposed to inorganic lead.

We previously reported that perinatal exposure to low levels of lead (Pb) results in a pronounced reduction of choline acetyltransferase (ChAT) activity in the septohippocampal pathway of the rat. In the present study we employed a ChAT specific 43-base oligonucleotide hybridization probe to compare the developmental expression of ChAT mRNA and ChAT activity in the septum of normal and Pb-exposed rats. Rats were exposed to Pb via maternal administration of 0.2% solution of Pb acetate in drinking water from one week before birth through postnatal day 21 (PN21). In normal animals, the developmental changes in the ChAT mRNA and activity levels were temporally correlated and approached adult levels by PN21. In the Pb-exposed pups, ChAT mRNA and activity levels were reduced respectively by 69% and 50% at PN7, 47% and 33% at PN14, and 47% and 22% at PN21. In contrast, Pb exposure had no significant effect on either ChAT mRNA or ChAT activity in the dams. These results indicate that cholinotoxicity of Pb in the septohippocampal pathway of the rat involves developmental stage-dependent disruption of ChAT gene expression.

Animals↗
PubMed1997

Study on stress distribution of the condyle.

OBJECTIVE: To investigate the internal state of stress distribution in healthy human condyles and to offer some references for application of the temporomandibular joint (TMJ) biomechanics. METHODS: Six male volunteers were selected to perform CT examination of the TMJ with 1.5 mm-thick sections at 1.5 mm intervals. Three dimensional image reconstruction of the joint was performed in the SUN workstation and the CT data were converted into the decimal system. The three dimensional finite element model mesh generation resulted from 1188 elements and 264 nodes in each condyle. Stress calculation was performed with SAP-V program, and the results were converted into mechanical density scalar. During the study, the internal state of stress distribution on each side condyle in every subject was analysed on the basis of loading on the anterior articular surface of the condyle. RESULTS: Stress was concentrated in the anterior articular surface of the condyle and was highest at the loading point. The condylar cortical bone was the main load-bearing area. The level of stress distribution in the cancellous bone of the condyle was very low. Near condylar neck stress was well-distributed on the cortical. The internal state of stress was essentially symmetrical on the same cuts of both side condyles. CONCLUSIONS: The results showed that three dimensional finite element analysis may indicate the internal state of stress distribution in the condyle, suggesting that a combination of the three dimensional finite element methods and the three dimensional imaging technique may be a useful means for diagnosis and treatment of TMJ diseases.

Adult↗
PubMed1997

[A knowledge-based method for 3D segmentation and display of human brain].

From the view of the artificial intelligence, a new method of segmentation and display of human brain medical images is descrided. On the basis of the knowledge of brain anatomy and image processing, we have built the 3D knowledge mobel using frame as the main knowledge expression method. Under the guide of the knowledge, the main structures in the brain are segmented and displayed by means of the "inelligent ray-tracing".

Artificial Intelligence↗
PubMed1997

[New species of Natronobacterium].

An extreme haloalkalophilic bacterium HAM-2 with pleomorphic rods was isolated from Hamatai soda lake in Inner Mongolia Autonomous Region. Growth occurs in 12%-30% NaCl, no growth below 12%, optimum 17.5%. pH range for good growth 7.8-10.4, optimum 9.0-9.5. The strain HAM-2 is non-motile, Gram-negative, pleomorphic, cell of which were 1.0-2.0 by 2.0-5.0 microns in size in liquid medium. The major polar lipids of the organisms are phosphatidylglycerol phosphate and phosphatidyglycerol and contains an unidentified phospholipid as a minor component PL4. G + C contant of DNA is 59.5 mol%. Based on the characteristics, the strain HAM-2 could be included in the genus Natronobacterium, but since HAM-2 differs from reported four species of this genus in cell shape, polar lipids and biochemical features. The name Natronobacterium innemongoliae sp. nov. is proposed. The type strain is designated HAM-2.

Natronobacterium↗
PubMed1996

Enhanced sympathetic neurite outgrowth on rat hippocampal tissue sections following septal lesions.

Cryostat sections of the rat hippocampus were used as tissue culture substrates for embryonic chick sympathetic explants. Neurite outgrowth from these explants was found to be significantly greater on sections taken from animals with septal lesions as compared to those receiving sham operations. This finding suggests that septal denervation leads to hippocampal substrate changes that enhance sympathetic neurite outgrowth in vitro, perhaps analogous to the sympathetic sprouting response that occurs in vivo.

Animals↗
PubMed1996

Developmental age-dependent upregulation of choline acetyltransferase and vesicular acetylcholine transporter mRNA expression in neonatal rat septum by nerve growth factor.

We examined the effect of intraventricular injection of nerve growth factor (NGF) on the choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) mRNA expression in the septa of neonatal rats. Rat pups were injected with 2.5 S NGF or cytochrome-c (control) on postnatal days (PN) 4 and 18, and sacrificed 3 days after injections for analysis of ChAT and VAChT mRNA levels by dot-blot hybridization of total septal RNA. In the NGF-treated pups, the ChAT and VAChT mRNA levels were elevated 3- and 2-fold, respectively, at PN7, and 1.8- and 1.3-fold at PN21. These results indicate that (1) NGF upregulates the expression of both ChAT and VAChT genes, (2) NGF has a greater effect on the expression of ChAT mRNA than VAChT mRNA, and (3) the effect of exogenous NGF on the expression of both genes diminishes with developmental age.

Age Factors↗
PubMed1996

Cholinergic denervation-like changes in rat hippocampus following developmental lead exposure.

We investigated the effects of developmental lead exposure from embryonic day 16 (E16) through postnatal day 28 (PN28), on cholinergic and catecholaminergic markers in the septohippocampal pathway in rats through fourth month of age. Lead exposure resulted in a persistent 30-40% reduction of [3H]hemicholinium-3 ([3H]HC-3) binding in the hippocampus through PN120, and 20-30% reduction of septal and hippocampal choline acetyltransferase (ChAT) activity which persisted through PN84 but returned to control levels in both septum and hippocampus at PN112. The muscarinic ligand [3H]quinuclidinyl benzylate ([3H]QNB) binding was reduced in the septum at PN28 but did not differ significantly from controls at PN56-PN112. Neither short- nor long-term effects of Pb exposure on [3H]QNB binding were seen in the hippocampus. Similar to the effects of fimbria-fornix transection, Pb exposure resulted in a long-term 50-90% increase of tyrosine hydroxylase(TH) activity in the hippocampus, although neither treatment affected TH activity in the septum. The lead-induced increase in hippocampal TH was significantly attenuated by superior cervical ganglionectomy. It is concluded that the effects of perinatal lead exposure resemble in several respects those seen following surgical disruption of the septohippocampal pathway in adult animals. The denervation-like effects in the hippocampus may be an important factor in long-term learning and cognitive impairments following developmental exposure to low-levels of lead.

Aging↗
PubMed1996

Changes in average blood pressure and incidence of high blood pressure 1983-1984 to 1987-1988 in four population cohorts in the People's Republic of China. The PRC-USA Cardiovascular and Cardiopulmonary Epidemiology Research Group.

OBJECTIVE: To assess comparative changes in systolic and diastolic blood pressure and incidence of high blood pressure over 4 years, and factors related to these changes, in northern and southern, urban and rural adults in the People's Republic of China. SETTING: This is a prospective study of populations surveyed by standardized methods in 1983-1984 and 1987-1988 in north China, Beijing area steel mill workers and farmers, and south China, Guangzhou area shipyard workers and farmers. SUBJECTS: The subjects were 8805 men and women aged 35-54 years at baseline (1983-1984), of whom 7338 were non-hypertensive (systolic blood pressure < 140, diastolic blood pressure < 90 mmHg, not being administered antihypertensive drugs). MAIN OUTCOME MEASURES: The main outcome measures were 4-year changes in systolic and diastolic blood pressures and the 4-year incidence of high blood pressure in persons not hypertensive at baseline. RESULTS: At baseline, the average systolic and diastolic blood pressures were higher for Beijing than for Guangzhou cohorts. At resurvey the average systolic blood pressure had increased for seven of eight sex-city-setting cohorts (all but Guangzhou urban men). The Beijing urban cohorts had the greatest increases (men 6.2 mmHg, women 4.9 mmHg, slopes of 1.6 and 1.2 mmHg/year). The incidence of high blood pressure was higher for Beijing than for Guangzhou cohorts in all four comparisons (men and women, urban and rural). Beijing men, urban and rural, had the highest incidence rates (about 21%). In multiple logistic analyses by sex, variables significantly related to 4-year high blood pressure incidence were city, baseline systolic blood pressure and body mass index, change in weight, and, for men, baseline alcohol use and heart rate. CONCLUSION: Modifiable lifestyle traits, previously shown to be related to blood pressure and high blood pressure in cross-sectional studies, also relate to the incidence of hypertension.

Adult↗