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Biomedical subjects

Z Li

Publications and source records attributed to Z Li.

At least 541 records · Page 30Linked to original sources
PubMed2000

Odour recognition and segmentation by a model olfactory bulb and cortex.

We present a model of an olfactory system that performs odour segmentation. Based on the anatomy and physiology of natural olfactory systems, it consists of a pair of coupled modules, bulb and cortex. The bulb encodes the odour inputs as oscillating patterns. The cortex functions as an associative memory: when the input from the bulb matches a pattern stored in the connections between its units, the cortical units resonate in an oscillatory pattern characteristic of that odour. Further circuitry transforms this oscillatory signal to a slowly varying feedback to the bulb. This feedback implements olfactory segmentation by suppressing the bulbar response to the pre-existing odour, thereby allowing subsequent odours to be singled out for recognition.

Afferent Pathways↗
PubMed2000

[One of the etiological factors of digestive tract cancers in Chinese: the missense mutation Val384Asp in the hMLH1 gene].

OBJECTIVE: To investigate the etiological role of Val384Asp in the hMLH1 gene, which may be a polymorphism in Chinese, in colorectal, gastric and esophageal cancers. METHODS: Genomic DNA extracted from normal tissues were subjected to analysis in exon 12 of the hMLH1 gene by single strand conformation polymorphism(SSCP) followed by DNA sequencing of aberrant bands in 101 colorectal, 79 gastric and 76 esophageal cancer patients; in 79 and 76 first degree relatives of gastric cancer and esophageal cancer patients respectively; and in 100 healthy control individuals. RESULTS: Six percent of Chinese healthy individuals were the carriers of Val3 84Asp in the hMLH1 gene. There were significant differences in the frequencies of Val384Asp in the hMLH1 gene between the patients with colorectal cancer at young age(<45 years) and the control individuals (P<0.05), and between the gastric cancer patients with family history, the first degree relatives and the control group (P<0.05 and P<0.01 respectively). No difference was found between the esophageal cancer patients, their relatives and healthy controls. CONCLUSION: The alleles frequency of Val384Asp in the hMLH1 gene in Chinese is three percent. This missense mutation may play a part in the etiology of colorectal and gastric cancers in Chinese.

Adaptor Proteins, Signal Transducing↗
PubMed2000

[Studies on properties of biofriction and wear for friction pairs of UHMWPE and Ti matrix-TiN-TiC gradient film materials].

In order to search the possible application of friction pairs of UHMWPE and Ti6Al4V-TiN-TiC etc. gradient materials to total hip joint replacements, we have prepared Ti6Al4V-TiN-TiC etc. gradient film materials by using N ion implant, d. c plasma CVD(PCVD). The properties of biological friction and wear for friction pairs of HUMWPE and Ti6Al4V-TiN-TiC etc. gradient film materials were investigated. The friction coefficient of friction paris and the wear loss of worn UHMWPE were measured; the surface morphology was observed by SEM. It has been shown that in human serum lubrication the wear loss of HUMWPE decreases with the increase in the surface hardness of its pairing ceramic film material. The pairing Ti6Al4V-TiN-TiC gradient film material possesses highest surface hardness, compared with other materials studied; UHMWPE wear loss in lowest. The wear mechanism of studied pairs has been analysed as well in the present paper.

Biocompatible Materials↗
PubMed2000

Clinical observation and experimental study on compound hypoglycemic decoction for hyperglycemia.

PURPOSE: To observe the clinical efficacy of Compound Hypoglycemic Decoction (CHD) and its effect on serum total cholesterol in model mice. METHOD: The paired t test was used to analyze the data recorded before and after administration of drugs for hyperglycemia induced by intraperitoneal injection of 75% egg yolk emulsion in experimental mice. CHD and Fenofibrate were administered as prevention measures. RESULTS: The total effective rate of serum total cholesterol (TC) decrease in 60 cases of hyperglycemia was 86.66% and that of serum total triglyceride (TG) decrease was 81.81%. The total effective rate of high-density lipoprotein-cholesterol (HDL-C) increase was 75%. The decrease in TC and TG, and the increase of HDL-C after treatment by in-group comparison were all significant (P < 0.05). 21.9% and 22.2% decrease in the total cholesterol was respectively found in the CHD and Fenofibrate groups (both P < 0.05), with no significant difference. CONCLUSION: The hypoglycemic action of Compound Hypoglycemic Decoction was remarkable in clinical practice, and it is very effective in preventing hyperglycemia in experimental mice.

Adult↗
PubMed2000

[Comparison of the expression and activity of phosphatidylethanolamine N-methyltransferase 2 between primary cultured hepatocytes and hepatoma cells in rats].

OBJECTIVE: To compare the expression and activity of phosphatidyl-ethanolamine N-methyltransferase 2 (PEMT(2)) between the primary cultured hepatocytes and CBRH7919 hepatoma cells in rats. METHODS: The expression and activity of PEMT(2) were demonstrated by immunochemistry, Western immunoblotting and [(3)H-CH(3)] SAM incorporation. Flow cytometry (FCM) was used to investigate the DNA content of the cells. RESULTS: PEMT(2) expression and activity were higher in the primary cultured hepatocytes than in hepatoma cells. Cell cycle analysis showed that the proportion of the hepatocytes was higher in G(1) phase and lower in S phase in the primary cultured hepatocytes than hepatoma cell lines. CONCLUSION: There is an intimate relationship between the expression of PEMT(2) and the proliferation of hepatocytes.

Animals↗
PubMed2000

An enzymologic study on bone marrow cells in patients with aplastic anemia treated by supplementing the kidney and removing blood stasis.

The content of cytochrome oxidase (CCO), succinate dehydrogenase (SDH) and neutrophil alkaline phosphatase (NAP) in bone marrow cells in 68 cases of aplastic anemia before and after treatment was determined by computerized graphical analysis and compared with that of normal volunteers (control group). The significantly lowered CCO and SDH levels and the markedly increased NAP content before treatment (P < 0.01) became approximately normal after that of supplementing the kidney and removing blood stasis (P > 0.05).

Adolescent↗
PubMed2000

Effects of overexpression of the amino-terminal fragment of apolipoprotein B on apolipoprotein B and lipoprotein production.

In vitro studies have shown that the binding site for microsomal triglyceride transfer protein (MTP) is within the first 17% of apoB (apoB-17). Expression of apoB-48 in McArdle cells decreases endogenous lipoprotein production; however, overexpression of human apoB in transgenic mice does not decrease endogenous mouse apoB expression. To assess this inconsistency, adenoviruses expressing human apoB-17 (AdB17) or apoB-17-beta (which contains apoB-17 plus a small lipid-binding beta-sheet region of apoB, AdB-17beta) were produced. Hepatoma cells were infected with AdB17 or AdB17-beta with AdLacZ, an adenovirus expressing beta-galactosidase, as a control. Overexpression of apoB-17 and apoB-17-beta in hepatoma cells to levels 2- to 3-fold greater than that of endogenous apoB did not alter endogenous apoB production. This was also true in the presence of oleic acid and N-acetyl-leucyl-leucyl-norleucinal. High levels of apoB-17 or beta-galactosidase expression reduced apoB-100 production; however, control protein production was also reduced. To assess the effects of apoB-17 expression in vivo, mice of three different strains were injected with AdB17. Two days after injection, plasma apoB-17 was approximately 24 times the amount of endogenous apoB in the C57BL/6 mice, 2 times the apoB-100 in human apoB transgenic mice, and 4 times the apoB-48 in apoE knockout mice. Overexpression of apoB-17 did not decrease apoB-100 or apoB-48 concentrations in mouse plasma as assessed by Western blot analysis. These results demonstrate that although the apoB-17 binds to MTP in vitro, it does not alter endogenous apoB expression in mice or in hepatoma cells.

Adenoviridae↗
PubMed2000

[A quantitative analysis of IL-6 mRNA expression of peripheral blood monocyte cell in patients with chronic hepatitis B].

OBJECTIVE: To investigate the relationship of interleukin-6 (IL-6) mRNA expression with the immunopathogenesis and viral clearance. METHODS: The serum IL-6 level of patients with chronic hepatitis B (CHB) were detected by ELISA and quantitatively the IL-6 mRNA expression of peripheral blood monocyte cell (PBMC) in patients with CHB were analysed by competitive RT-PCR-ELISA. RESULTS: Serum level of IL-6 in patients with CHB was significantly increased. Both expression rates of IL-6 mRNA target fragment in control and in patients with CHB were 41.7% (5/12) and 82.1% (23/28) respectively. The quantitative ELISA of production of RT-PCR showed the copies of IL-6 mRNA in 5 cases of control were 1 000 to 10 000 (the mean log copies was 3.65), while the copies of IL-6 mRNA in 23 cases of patients were all more then 10 000 (the mean log copies was 4.40). CONCLUSION: This study shows that the increased level of IL-6 may play some role in hepatitis B infection, the increased serum level of IL-6 is related to the enhanced expression of IL-6 mRNA of PBMC.

Adult↗
PubMed2000

[The design and comparative biomechanical study of TDP&CS].

A new internal fixation device(TDP&CS) for subtrochanteric fracture of the femurs was designd and compared with Gamma nail and Jewwet nail biomechanically. A model with 5 mm bone deficit presenting as fracture fixation (mFF) and a model with nail holes presenting as fracture healed and nails removed(mFHNR) were designed. Four-point anti-bent test, anti-axial compression test and anti-torsion test were continually performed on mFF, and four-point anti-bent and anti-torsion tests were performed on mFHNR. The results showed that in mFF group, TDP&CS was stronger than Jewwet nail(P < 0.05) in all the three tests, but it was not statistically different from Gamma nail. In mFHNR group, TDP&CS had better features than Gamma nail and Jewett nail in anti-bent and anti-torsion tests (P < 0.05). These data indicate that TDP&CS is a good internal fixation device for subtrochanteric fracture of the femurs, it is as good as Gamma nail and better than Jewett nail in fixing the fracture, and its nail holes could do less injury to the bone as compared with those of the Gamma nail and Jewett nail.

Adult↗
PubMed2000

[Studies on metabolite of beta-elemene in rat bile].

AIM: To study the metabolite of beta-elemene in the bile of rat. METHODS: After i.v. 100 mg.kg-1 beta-elemene, the metabolite in rat bile was extracted by ether. Mass spectrometry, nuclear magnetic resonance, infrared spectrometry and ultraviolet spectrometry were used to analyze the metabolite of i.v. beta-elemene in rat bile. RESULTS: It was confirmed by nuclear magnetic resonance that the methyl of No. 11 carbon connecting with No. 10 carbon of a metabolite in rat bile was oxidized to be aldehyde. The molecular weight of the metabolite was 218 which detected by mass spectrometry. Infrared spectrometry and ultraviolet spectrometry proved that the aldehyde existed in the metabolite. The structure of the metabolite in bile of rat was identified, that was 1-methyl-1-ethenyl-2-isopropenyl-4-isopropenyl aldehydohexamethylene. CONCLUSION: The biotransformation of beta-elemene exists in vivo.

Animals↗
PubMed2000

[A study of human breast carcinoma xenografts in nude mice].

OBJECTIVE: To study the spontaneous metastasis and the genetic stability of human breast carcinoma xenografts in nude mice and its micrometastasis. METHODS: The intact tissue of surgical specimens from breast carcinoma were xenografted into nude mice and transplanted from generation to generation. Cells from the xenografts were cultured in vitro and retransplanted into nude mice. Microsatellite DNA in genome of human breast carcinoma, xenotransplanted tumors and metastases in nude mice were analysed at three microsatellite loci. RESULTS: The tumorigenicity of orthotopic xenotransplantation was 88.6%(31/35) with a metastasis rate of 41.9%(13/31). Cells from the xenografts were cultured in vitro successfully, both the take rate of retransplantation into nude mice and the spontaneous lung metastasis rate were 100%(10/10). Microsatellite DNA sequences in genome of the xenotransplanted tumors and metastases in nude mice were identical with that of the original human breast carcinoma at the three microsatellite loci. CONCLUSIONS: The tumorigenicity and metastasis potential can be improved in human breast carcinoma xenograft using the intact fresh tumor tissue and orthotopic graft. The xenotransplanted tumors and their passaged tumors maintained the genetic stability. The detection of microsatellite DNA may discover micrometastasis in the nude mice model.

Animals↗
PubMed2000

[Analysis of the design principle and mechanics nature of adjustable semi-circular planum external fixator].

This thesis presents our studies of an adjustable semi-circular planum external fixator and offers a relatively detailed introduction and analysis of the structure principle and mechanics nature. Because dual-direction joining pole with active joints was used, by adjusting the length of each pole, it can not only make the two semi-circular steel plates more parallely along the axis line to stabilize the fracture and lengthen the extremity, but it also can change the planum angle of the steel plate, and thus achieve the effect of orthopaedic function.

Equipment Design↗
PubMed2000

Distraction osteogenesis in functional reconstruction of mandible--report of 6 cases.

OBJECTIVE: To study the application of distraction osteogenesis in mandibular function reconstruction. METHODS: Three types of mandibular distractors were used in 6 patients with different mandibular defects due to tumor resection. For 2 cases with ramus defects, specially designed distractors were used to restore the normal height of the ramus. In 1 case, the trifoci distraction principle was used and a trifoci distractor was designed. In 3 cases, vertical distractors made in Germany or China were used. The patient average age was 31.5 years old (ages ranged from 8 to 54). RESULTS: In 5 cases the mandibular lengthenings were successful according to the direction and distance chosen before distraction. In 1 case, the trifoci distraction principle was applied and a proximal 23 mm mandibular defect was successfully corrected; however, the 23 mm distal mandibular defect was not corrected because the screws for fixation of the transport block were loosened. Infection and dysosteogenesis did not occur in any cases. CONCLUSION: Distraction osteogenesis can successfully be used in mandibular functional reconstruction and is more advantageous than traditional techniques. The most favorable time for distraction osteogenesis in mandibular reconstruction is at the time of tumor resection.

Adult↗
PubMed2000

Experimental study of phosphopeptide in promoting tooth remineralization.

OBJECTIVE: To explore a new method for effective and safe prevention and treatment of caries. METHODS: Following the theory of tooth remineralization, we searched for the mechanism and clinical application of tooth remineralization with phosphopeptide. RESULTS: Phosphopeptide, with calcium and phosphorus, had a high affinity for hydroxyapatite and could enhance tooth remineralization. CONCLUSION: Phosphopeptide was effective in the prevention and treatment of tooth decay. Clinically, it could be safely applied.

Animals↗
PubMed2000

The research and development of noncontact 3-D laser dental model measuring and analyzing system.

OBJECTIVE: To research and develop a new laser scanning 3-dimensional digitization system for collecting, showing, and measuring the data of dental casts. MATERIAL AND METHODS: According to the 3-dimensional measuring method, by using 2 pulsate motors to make the synthetic movement of the dental cast, a special semiconductor laser, and 2 special line array CCD, the 3-D data could be found anywhere on the surface of the dental cast. The program, developed with Visual C++ language under the Windows (Windows tm) system, can control the scanner, rebuild the 3-D graphics and measure the data of the dental cast. RESULTS: The system offers 70 x 70 x 70 mm measurement scope, 0.01 mm resoling power, < 0.1 mm mean deviation, and 25 mins for single cast scanning. CONCLUSION: The advantages of this system are its precision, simplicity, high efficiency, and wide range of measurements with complete direct view. This system also supplied new information that cannot be found with traditional measurement methods.

Computer Graphics↗