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Biomedical subjects

S Li

Publications and source records attributed to S Li.

At least 307 records · Page 17Linked to original sources
PubMed2001

[Stress-strain properties of the tissue-engineered cartilage].

This study was conducted to investigate the biomechanical properties of tissue-engineering cartilage. The compressive modulus of the collagen-chondrocyte constructs that had been cultured in vivo for 16 weeks and the centrifuge-tube-cultured cartilage in vitro were measured with 5% strain. The results showed that the compressive moduli of the centrifuge-tube-cultured cartilage at the 4th, 8th, 12th and 16th weeks were 0.352 MPa, 0.653 MPa, 0.233 MPa and 0.262 MPa respectively. The top modulus among them was at the 8th week. The compressive modulus of the neocartilage engineered by the collagen-chondrocyte constructs in vivo for 16 weeks was 10.668 MPa and reached the same order of magnitude as human fetal articular cartilage, but it is still under that of the human fetal articular cartilage actually. The culture methods should be developed further though the dynamic alteration of the compressive modulus of the centrifuge-tube-cultured neocartilage is in accord with that of the GAG/DNA content ratio of the neocartilage.

Animals↗
PubMed2001

[Study on the noninvasive measurement of cerebral oxygen saturation and cerebral phronetal function].

With the use of Near-infrared spectroscopy(NIRS), the noninvasive measurement of cerebral oxygen concentration can be achieved in vivo based on the Lambert-Beer Law. In this paper, we discuss the possibility of studying higher brain functions through a combination of cerebral oxygen saturation and cerebral function measurement. Event-related experiments are introduced to measure the cerebral phronetal function. Time domain curves show sight differences among these experiment results. However, with the aid of DFT, experiment data of all five human volunteers show that the frequency near 20 Hz or 40 Hz is evoked depending on the difficulty of the mental tasks. The results demonstrate the feasibility of cerebral function studies by means of cerebral oxygen saturation measurement analysis in the frequency domain.

Adult↗
PubMed2001

Myocardial protection of warm blood cardioplegic induction during cardiopulmonary bypass.

In his prospective randomized clinical study, we evaluated the myocardial protection of warm blood cardioplegic induction and cold blood cardioplegic induction, respectively, during cardiopulmonary bypass. Twenty-eight adult patients who underwent valve replacement were randomly divided into two groups: group T (14 cases) received cold (6-8 degrees C) blood cardioplegic induction after ECG showed straight line induced by warm (35-37 degrees C) blood cardioplegia; whereas, group C (14 cases) received cold blood cardioplegic induction only. The effects of myocardial protection of both cardioplegic inductions were evaluated by clinical outcomes, myocardial biochemistry index (cardiac troponin T, cTnT), and myocardial automorphology. The ratio of myocardial auto resuscitation was significantly higher in group T (93%) than that in group C (50%). Only one case in group T (7%) and three cases in group C (21%) needed temporary pacemakers. No case in group T (0%) and five cases (36%) in group C received dopamine. The postoperative mechanical ventilation time and ICU stay time of group T were shorter than those of group C. Myocardial biochemistry indexplasma level of cTnT in group T was lower than that of group C immediately and 6 h after cardiopulmonary bypass. Myocardial morphology-group T had comparably better outcomes than group C. We concluded that warm blood cardioplegic induction during cardiopulmonary bypass, compared with cold blood cardioplegic induction, provides better myocardial protection.

Adult↗
PubMed2001

[The distribution and natural degradation of cyanide in goldmine waste-solid and polluted soil].

The farmland and river were seriously polluted by cyanide because one goldmine tailing dam collapsed in 1995. 3 and 4 years after the accident, the cyanide distribution in the polluted farmland and the abandoned tailing dam was studied. The results indicated that natural degradation of cyanide in soil section was slower than in natural water body. The cyanide transference in soil section was similar to freely soluble salts. In arid and semiarid area, cyanide can be highly enriched in the salt shell which content degrading 4 years even higher than the fresh tailing slurry. One side the viscidity layer in the soil section can partly prevent cyanide transference to groundwater, on the other side the result can cause the cyanide highly enrich in the viscidity layer. According to character of cyanide natural degradation in soil the measurement of prevention and cure soil pollution by goldmine tailing dam collapsing was brought forward.

Cyanides↗
PubMed2001

[Studies on cloning and expression of hepatitis B virus x gene].

OBJECTIVE: To express and purify the x gene of hepatitis B virus (HBV), and then the purity of the protein could specifically be analysed by the human antibodies against HBV x antigen (protein). METHODS: HBV x gene was amplified from the complete genome by PCR, and cloned in the pGEX-2T fused expression vector. After transforming the plasmid into E.coli, the recombinant with HBx gene was obtained. The fusion protein was generated with E.coli fused expression system and purified with affinity chromatography. RESULTS: The HBx protein could be applied to detecting specific antibody of hepatitis B virus patients. CONCLUSIONS: The purity of the HBx protein can specifically be recognized by the human antibodies against HBV x antigen.

Base Sequence↗
PubMed2001

Hypertension in normotensive and hypertensive rats by spermine ingestion.

Polyamines (putrescine, spermidine and spermine) play an important role in the development of hypertension and in the expression of atrial natriuretic peptide (ANP), a cardiac hormone involved in the regulation of blood pressure. Wistar Kyoto normotensive (WKY) and spontaneously hypertensive rats (SHR) were given spermine in drinking water (0.5%) for 15 days. The spermine intake elevated the blood pressures of both SHR and WKY rats and reduced the expression of ANP (Northern blotting) in the ventricles. ANP levels in the plasma determined by enzyme immunoassay (EIA) showed no changes in the levels of plasma ANP after spermine intake. An analysis of polyamines by high-pressure liquid chromatography showed that the levels of spermine and spermidine were elevated in SHR hearts. It was in SHR hearts alone that spermine intake was associated with increases in the levels of putrescine. The results suggest that spermine-induced increases in blood pressure may involve mechanisms other than ANP.

Animals↗
PubMed2001

[Genetic structure and intraspecific genetic polymorphisms in natural populations of Psathyrostachys huashanica].

Psathyrostachys huashanica Keng, which is endemic to China, only distributes in Mt. Hua of Shaanxi Province. 5 enzyme systems coding 13 loci were analyzed in 13 subpopulations of P. huashanica from Mt. Hua. Allozyme analysis showed that high genetic variability and clonal diversity existed in the species. Mean proportions of polymorphic loci (95% criterion), average number of alleles per locus, and mean expected heterozygosity were 69.2%, 1.8 and 0.344, respectively. Simpson index was 0.998. A negative species mean fixation indice (-0.252) indicates that there is a considerable excess of heterozygotes compared to the expected proportions of heterozygote loci. Mean genetic distance among populations was 0.049 (range: 0-0.139), and 91% of the genetic variation resided within populations. Gene flow estimated by indirect methods was 2.77, which was much lower than the Nm value (5.24) of anemophytes. This suggested that gene flow of P. huashanica might be in a critical level, and genetic differentiation might occur in natural population of this species.

Genetic Variation↗
PubMed2001

Automatic analysis of image of surface structure of cell wall-deficient EVC.

Some computer applications for cell characterization in medicine and biology, such as analysis of surface structure of cell wall-deficient EVC (El Tor Vibrio of Cholera), operate with cell samples taken from very small areas of interest. In order to perform texture characterization in such an application, only a few texture operators can be employed: the operators should be insensitive to noise and image distortion and be reliable in order to estimate texture quality from images. Therefore, we introduce wavelet theory and mathematical morphology to analyse the cellular surface micro-area image obtained by SEM (Scanning Electron Microscope). In order to describe the quality of surface structure of cell wall-deficient EVC, we propose a fully automatic computerized method. The image analysis process is carried out in two steps. In the first, we decompose the given image by dyadic wavelet transform and form an image approximation with higher resolution, by doing so, we perform edge detection of given images efficiently. In the second, we introduce many operations of mathematical morphology to obtain morphological quantitative parameters of surface structure of cell wall-deficient EVC. The obtained results prove that the method can eliminate noise, detect the edge and extract the feature parameters validly. In this work, we have built automatic analytic software named "EVC.CELL".

Cell Membrane↗
PubMed2001

Use of up-converting phosphor reporters in lateral-flow assays to detect specific nucleic acid sequences: a rapid, sensitive DNA test to identify human papillomavirus type 16 infection.

BACKGROUND: A lateral-flow (LF) device using the new reporter up-converting phosphor technology (UPT) was applied to DNA (hybridization) assays for the detection of specific nucleic acid sequences, thereby aiming to perform the test outside well-equipped laboratories. The methodology reported here is sensitive and provides a rapid alternative for more elaborate gel electrophoresis and Southern blotting. In a preliminary study, it was applied to screen for the presence of human papillomavirus type 16 (HPV16) in a defined series of cervical carcinomas. METHODS: A LF assay was used to capture haptenized DNA molecules and hybrids, which were immunolabeled (before LF) with 400-nm UPT particles. These particles emit visible light after excitation with infrared in a process called up-conversion. Because up-conversion occurs in only the phosphor lattice, autofluorescence of other assay components is virtually nonexistent. RESULTS: The use of the UPT reporter in LF-DNA tests, as compared with colloidal gold, improved the detection limit at least 100-fold. UPT LF-DNA tests were successfully applied to detect (in a blind test) the presence of HPV16 in DNA extracts obtained from cervical carcinomas. Test results matched 100% with previous characterization of these carcinomas. CONCLUSIONS: The use of UPT in LF assays to detect specific nucleic acids provides low attamole-range sensitivity. Hybridization and consecutive detection of PCR-amplified HPV16 sequences were successful in a background of 10 microg of fish-sperm DNA. The sensitivity of UPT detection in these complex mixtures indicates that detection of viral infections without PCR or other amplification technique is achievable.

Antibodies, Monoclonal↗
PubMed2001

[Trihalomethane formation potential (THMFP) of soils in Guangdong Province].

Trihalomethane formation potentials were analyzed with the lixivia of typical soil samples in Guangdong Province. The results showed that the bulk THMFP contents of soil lixivia (b-THMFP) range from 0.7 to 36.8 micrograms/g with a median value of 10.6 micrograms/g, and the THMFP contents of 0.45 micron filtered soil lixivia, representing the THMFP contents of dissolved organic matter (d-THMFP), from 0.5 to 21.2 micrograms/g with a median value of 3.9 micrograms/g. Sample 19 (Calcareous soil) had the highest b-THMFP and d-THMFP while sample 20 (Purple soil) had the lowest b-THMFP and sample 5 (Latored soil) had the lowest d-THMFP. In general, suspended organic matter had great contribution to the THMFP. The physico-chemical properties, such as organic matter contents and contents of various oxides, as well as soil genetic horizon and vegetation are main factors dominating the THMFP levels in the soil.

Soil Pollutants↗
PubMed2001

Effect of Cr(VI) exposure on sperm quality: human and animal studies.

The semen status of male workers occupationally exposed to hexavalent chromium(VI) was investigated. Sperm counts from exposed workers were 47.05+/-2.13 x 10(6)/ml and those from control group 88.96+/-3.40 x 10(6)/ml. Sperm motility decreased from 81.92+/-0.41% for the control group to 69.71+/-0.93% for the exposed workers. The levels of zinc, lactate dehydrogenase (LDH), and lactate dehydrogenase C4 isoenzyme (LDH-x) in seminal plasma for the exposed workers were 1.48+/-0.07 micromol/ml, 1.05+/-0.02 x 10(3) U, and 0.47+/-0.01 x 10(3) U, respectively, which were significantly lower than those of 5.72+/-0.15 micromol/ml, 1.49+/-0.02 x 10(3) U, and 0.78+/-0.15 x 10(3) U for the control group, respectively. Follicle stimulating hormone (FSH) (7.34+/-0.34 x 10(-3) IU/ml) in serum from the exposed workers was significantly higher than that (2.41+/-0.08 x 10(-3) IU/ml) from the control group. On the other hand, there were no significant differences in semen volume, semen liquefaction time, luteinizing hormone (LH) level in serum, and Cr concentration in both serum and seminal plasma between the exposed workers and the control group. Feeding Cr(VI) to rats significantly reduced the epididymal sperm counts from 87.40+/-3.85 x 10(6)/g epididymis in control group to 21.40+/-1.20 x 10(6)/g epididymis at a CrO(3) dose of 10 mg/kg body weight and to 17.48+/-1.04 x 10(6)/g epididymis at a CrO(3) dose of 20 mg/kg body weight. Exposure of rats to Cr(VI) also significantly increased the sperm abnormality from 2.75+/-0.06% in the control group to 6.68+/-0.32% in the exposed group at a CrO(3) dose of 10 mg/kg body and to 7.6+/-0.15% at a CrO(3) dose of 20 mg/kg body weight. In exposed rats, there was visible disruption in germ cell arrangement near the walls of the seminiferous tubules. The diameters of seminiferous tubules in exposed rats were smaller. These results suggest that occupational exposure to chromium(VI) leads to alteration of semen status and may affect the reproductive success of exposed workers.

Animals↗
PubMed2001

Mechanism of pluronic effect on P-glycoprotein efflux system in blood-brain barrier: contributions of energy depletion and membrane fluidization.

Pluronic block copolymer, P85, inhibits the P-glycoprotein (Pgp) drug efflux system and increases the permeability of a broad spectrum of drugs in the blood-brain barrier (BBB). This study examines the mechanisms by which P85 inhibits Pgp using bovine brain microvessel endothelial cells (BBMEC) as an in vitro model of the BBB. The hypothesis was that simultaneous alterations in intracellular ATP levels and membrane fluidization in BBMEC monolayers by P85 results in inhibition of the drug efflux system. The methods included the use of 1) standard Pgp substrate rhodamine 123 to assay the Pgp efflux system in BBMEC, 2) luciferin/luciferase assay for ATP intracellular levels, and 3) 1,6-diphenyl-1,3,5-hexatriene for membrane microviscosity. Using 3H-labeled P85 and fluorescein-labeled P85 for confocal microscopy, this study suggests that P85 accumulates in the cells and intracellular organelles such as the mitochondria where it can interfere with metabolic processes. Following exposure of BBMEC to P85, the ATP levels were depleted, and microviscosity of the cell membranes was decreased. Furthermore, P85 treatment decreased Pgp ATPase activity in membranes expressing human Pgp. A combination of experiments examining the kinetics, concentration dependence, and directionality of P85 effects on Pgp-mediated efflux in BBMEC monolayers suggests that both energy depletion (decreasing ATP pool available for Pgp) and membrane fluidization (inhibiting Pgp ATPase activity) are critical factors contributing to the activity of the block copolymer in the BBB.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

[Effects of surface pattern of polymers on adhesion characteristics of transformed human embryonic tendon cells].

Effects of surface pattern of polymers on adhesion characteristics of transformed human embryonic tendon cells (THETCs) have been examined by using a micropipette aspiration technique, which is a cellular mechanical method. The results showed that the adhesion characteristics of THETCs depend on the surface pattern of polymers, and the adhesion force of THETCs to porous films is higher than that to non-porous films and fibers. The adhesion force bears relationships with the aperture of porous films and has a stronger dependence on the large aperture (150-500 microns) than on the small aperture (< 150 microns) of porous films. The adhesion force of THETCs to fibers is increased slightly with the diameter of fibers (P > 0.05). These demonstrate that the tissue-engineered tendon scaffolds made of porous polymer foam with specially designated aperture, or of polymer fiber with specially designated diameter, may serve as a good attachment substrate for THETCs.

Biopolymers↗
PubMed2001

[A study for optimal method of separating and cultivating embryonic rat cerebral neurons].

In order to improve the method of separating and cultivating the embryonic rat cerebral neurons in vitro, we compared different digestive enzymes, mechanical separating methods and two different mediums. It was found that highly purified and active embryonic rat cerebral neurons could be harvested by cultivating the neurons in the standard neurobasal medium with B-27 supplement, 10% horse serum, 10% fetal bovine serum and L-Glutamine after separated by digestion with the use of 0.05% trypsin and 0.05% collagenase II.

Animals↗
PubMed2001

[The transcription of interleukin-8 in gastric epithelial cells by Helicobacter pylori strains in Chinese].

OBJECTIVE: To observe the effect of the vac A genotype and the existence of cag pathogenicity island (cag PAI) of Helicobacter pylori (Hp) isolated from Chinese patients on the transcription of IL-8 in gastric epithelial cells. METHODS: The genotype of vac A and the existence of cag PAI of Hp were determined by gene sequencing and Southern blot, respectively; the constructed L5F11 cells were cocultured with the bacteria and the transcription of interleukin-8(IL-8) was indicated by luciferase activity and the cytotoxin activity showed by using HeLa cell vacuolating assay. RESULTS: The ability to induce luciferase by the strains with complete cag PAI (n = 15) was much higher than that by the wild cag negative strain G50[(0.47 +/- 0.09) x 10(6) cpm vs (0.13 +/- 0.02) x 10(6) cpm, P < 0.01] and there was no difference in the luciferase activity induced by the strains with partial cag (n = 4) and by G50[(0.23 +/- 0.08) x 10(6) cpm vs (0.13 +/- 0.02) x 10(6) cpm, P > 0.05]; Also no difference was found in the luciferase activity induced by the strains with vac A s1/m1 (n = 5) and the strains with s1/m2 (n = 14) [(0.29 +/- 0.12) x 10(6) cpm vs (0.53 +/- 0.41) x 10(6) cpm, P > 0.05] although the formers had much higher vacuolating cytotoxin activity than the latters (P < 0.001). CONCLUSION: The transcription of IL-8 in gastric epithelial cells induced by Hp isolated from Chinese patients was associated with the existence of cag PAI and not with the genotype of vac A.

Bacterial Proteins↗
PubMed2001

[Significance of vascular endothelial growth factor expression in colorectal cancer].

OBJECTIVE: To investigate the expression of vascular endothelial growth factor (VEGF) mRNA in colorectal cancer (CRC) and its relation with the clinicopathologic features and explore new approaches to prevent and inhibit recurrence and metastasis of CRC. METHODS: Surgical samples of 68 patients with CRC were studied using reverse transcription-polymerase chain reaction (RT-PCR). The relative level of VEGF mRNA expression was measured by determining a ratio of PCR products of VEGF to that of beta-actin gene. RESULTS: (1) Expression of VEGF mRNA in tumor tissue was found in 67.6% (46/68) of the sample, whereas it was seen in 32.4% (22/68) of the surrounding nontumorous colorectal tissue. (2) The level of VEGF mRNA expression in tumors with serosal invasion, lymph node metastasis, distant metastasis or Dukes' D stage was higher than that without serosal invasion, lymph node metastasis, distant metastasis or Dukes' A and B and C stage (P < 0.01). (3) There was no significant difference in the expression of VEGF mRNA between large CRC (diameter > 5 cm) and small CRC (diameter < or = 5 cm) (P > 0.05) or histologic types (P > 0.05). CONCLUSION: VEGF may play an important role in the invasion and metastasis of CRC. It is thus show that angiogenesis in tumor correlates with the progression of CRC.

Adult↗