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Biomedical subjects

Z Li

Publications and source records attributed to Z Li.

At least 397 records · Page 22Linked to original sources
PubMed2001

[The different functions of glnB and glnZ from Azospirillum brasilense YU62 in the control of nitrogen fixation].

The glnB and glnZ genes of A. brasilense have 70% homology at nucleotide sequence. glnB is located in a 3.7 kb Eco RI+ PstI fragment and glnZ is located in a 3.7 kb SalI fragment. Both glnB and glnZ genes were mutagenized by Kmr cassette insertions and glnB- and glnZ- mutants were obtained. glnB- mutant did not have any nitrogenase activity, while glnZ- mutant still has nitrogenase activity. The coding regions of glnB and glnZ were cloned into pVK100 vectors and recombinant plasmids pVK-II and pVK-Z were obtained, respectively. The recombinant plasmids pVK-II and pVK-Z were introduced into glnB- and glnZ- to produce C-glnB and C-glnZ, respectively. C-glnB can restore nitrogenase activity and C-glnZ does not have effect on nitrogenase activity. When pVK-II and pVK-Z were introduced into A. brasilense Yu62 and draT-, respectively, the Yu62-II (containing pVK-II) and draT-II (containing pVK-II) have higher nitrogenase activity than that of wild type Yu62. In contrast, Yu62-Z (containing pVK-Z) and draT-Z (containing pVK-Z) has no effect on nitrogenase activity. The nifA(-)-II (containg pVK-II) and nifA(-)-Z (containing pVK-Z) still have no nitrogenase activity.

Azospirillum brasilense↗
PubMed2001

[An analysis on the forearm bone mass density of rural female and the environmental risk factors].

The distribution of distal and proximal forearm bone mass densities (BMD) with age was discribed and the environmental risk factors of rural female analyzed. A group of 1432 rural female aged 15 and over were sellected. Their demographic characteristics, living and eating habit were obtained by standardized questionnaire. The distal and proximal forearm bone mass density were measured by peripheral dual-energy X ray absorptionmetry (pDEXA). The results showed that the distal and proximal forearm BMDs were increased with age before age 25 and 30 respectively, and reached the peak value at age 30-35. The distal forearm bone density decreased significantly at age 40 while the proximal forearm BMD decreased at age 45. Bone loss rate of the two bone sites was increased significantly at age 50 and reached the peak value at age 55-60. Only the the density of proximal forearm bone, and the year of menopause was the main cause of low bone density. Body weight was the positive factor for bone density at age less than 60. Height only positively affected the proximal forearm bone of those at age 30-45. More ever, drinking tea, parity and educational status may affect distal forearm bone in certain age group while parity, educational status, occupation and marital status were possible risk factors of proximal forearm BMD. It is concluded that environmental risk factors of BMD varied with bone site and age. The prevention of low BMD must rely on subject's age and bone site. The surveillance of low bone density must put the emphasis on spony bone.

Adult↗
PubMed2001

[Studies on the genotoxic effects of acrylonitrile].

The effect of acrylonitrile (AN) on the reproduction was investigated in 341 male and 365 female exposed workers, 384 male and 438 female unexposed controls by questionnaires on the process of childbearing and the outcome of child birth. The results showed that AN caused menstrual disorder and dysgenesis in exposed female workers and the wife of exposed male workers. It is concluded that AN is harmful to the reproduction of exposed male and female workers.

Acrylonitrile↗
PubMed2001

Vitreous cavity-associated immune deviation induced by retinal S antigen.

PURPOSE: To determine whether the vitreous cavity (VC) supports the induction of deviant immune responses to retinal soluble(S) antigen and to observe the influence of interleukin-1 (IL-1) on the immunologic properties of the VC. METHODS: Retinal S antigen was inoculated into the anterior chamber(AC) and the VC in Wistar rats. Seven days after antigen inoculation, the recipient animals were immunized with S antigen and complete Freund's adjuvant. Delayed-type hypersensitivity (DTH) was assessed by footpad challenge. To alter systemic immune conditions, IL-1 was administrated by intraperitoneal injection. RESULTS: Antigen-specific DTH did not develop in rats in which S antigen was injected into the AC and the VC. By contrast, when IL-1 administrated systemically, S antigen was injected into the AC and VC elicited strong DTH. CONCLUSION: The VC supports immune deviation for soluble antigen by acitivity suppressing antigen-Specific DTH. Systemic administration of exogenous IL-1 eliminates the capacity of the VC to support immune deviation to soluble antigen locally injected.

Animals↗
PubMed2001

[Rapid construction of directional cDNA library from human nasopharynx].

OBJECTIVE: To construct a directional cDNA library from human adult nasopharynx by SMART (switching mechanism at 5' end of RNA transcript) technique. METHODS: The total RNA was separated from human adult nasopharynx epithelial tissue and the first-strand cDNA was synthesized through reverse transcription by a modified oligo(dT) primer(contained sfi IB site) while the SMART oligonucleotide(contained sfi IA site) was utilized as a template so that the first-strand cDNA could be extended over the 5' end of mRNA. The double-strand cDNA was amplified by LD-PCR(long-distance PCR) with the above two primers and then digested by sfi I (IA & IB) restriction enzyme. After cDNA size fractionation through CHROMA SPIN column, the double-strand cDNA was ligated into the sfi I-digested lambda TripIEx2 vector and then the recombinant DNA was packaged in vitro. RESULTS: The unamplified human adult nasopharynx cDNA library consists of 1.5 x 10(6) independent clones in which the percentage of recombinant clones is about 100%. The titer of the amplified cDNA library is 3.8 x 10(9) pfu/ml and the average exogenous inserts of the recombinants is 1.5 kb. CONCLUSION: These results shows that the human adult nasopharynx cDNA library has an excellent quality and lays solid foundation for screening and cloning new tumor suppressor genes of nasopharyngeal carcinoma(NPC) and tissue-specific genes of human nasopharynx.

Adult↗
PubMed2001

[Significance and expression of transforming growth factor beta in human nasal polyp tissue].

OBJECTIVE: To explore the pathogenesis of nasal polyposis and the expression of transforming growth factor beta (TGF-beta) in human inflammatory nasal polyps. METHODS: TGF-beta 1-3 in nasal polyp tissues and inferior turbinate mucosa of twenty-five polyposis patients were detected with immunohistochemistry alkaline phosphatase and anti-alkaline phosphatase (APAAP) method. The inferior turbinate mucosa of eight healthy volunteers were selected as control. Six polyp tissues were estimated with double immunolabeling and Western-blot analysis to compare the characterization of the TGF-beta isoforms expression and the proportion of macrophages and eosinophils in nasal polyp tissues. RESULTS: The expression of TGF-beta 1-3 in nasal polyps was significantly higher than that in nasal mucosa and indetecable in nasal mucosa from healthy volunteers; TGF-beta 1 was the main isoform detected in nasal polyps; TGF-beta positively was accompanied by numerous macrophage and eosinophil infiltration. CONCLUSIONS: TGF-beta mainly TGF-beta 1 is strongly expressed in nasal polyps and its mucosa, where it could be produced by macrophages and eosinophils. TGF-beta could induce modification of epithelium and connective tissue and therefore be involved in the pathogenesis of nasal polyposis.

Eosinophils↗
PubMed2001

[Misdiagnosis in isolated sphenoid sinus diseases].

OBJECTIVE: To improve the correct diagnosis for isolated sphenoid sinus diseases. METHODS: Twelve patients with isolated sphenoid disease from 1991 to 1998 were reviewed. The factors of misdiagnosis were discussed. RESULTS: In this group of 12 patients with isolated sphenoid diseases, 8 failed to be diagnosed at the first time of medical consultation. The misdiagnosis included optic neuritis, neuralgia, ophthalmitis, pulmonary tuberculosis, epistaxis and epilepsy. CONCLUSIONS: The main causes of misdiagnosis were: low incidence of the disease, nonspecific clinical symptoms, and unawareness of the doctor. CT or magnetic resonance imaging (MRI) can provide much more informations about the diagnosis.

Adult↗
PubMed2001

Relationship between human parvovirus B19 infection and aplastic anemia.

OBJECTIVE: To explore the relationship between human parvovirus B19 (HPV B19) infection and aplastic anemia (AA) and to investigate the role of HPV B19 in the occurrence of AA. METHODS: The presence of HPV B19 DNA was detected in the peripheral blood samples of 60 patients with AA (children 38 and adults 22) by nested polymerase chain reaction (PCR) assay, and 30 healthy persons were selected as control. RESULTS: Sixteen (26.7%) of 60 AA cases were HPV B19 DNA positive, while all the samples in the control group were negative for HPV B19 (P = 0.000914). Among the case group, the positive rates of HPV B19 DNA were 21.4% (6/28), 30.0% (3/10), 20.0% (1/5) and 35.3% (6/17) in children acute AA (AAA), children chronic AA (CAA), adults AAA and adults CAA patients respectively, which were significantly higher than that in the control group. Furthermore, there was no remarkable difference between children AA and adults AA in the 16 HPV B19 DNA positive patients; neither was there between AAA and CAA. CONCLUSION: HPV B19 infection is not only correlated with the occurrence of children AAA and CAA, but also with adults AAA and CAA, and might be an important viral cause for AA in humans.

Acute Disease↗
PubMed2001

Gut barrier function damage following multiple firearm injuries in a porcine model.

OBJECTIVE: To study the characteristics and pathogenesis of gut barrier damage following multiple firearm injuries in a porcine model. METHODS: Twenty-four small pigs were divided into 4 groups: control group (n = 6, group C), group H (n = 6, gunshot-induced tangential fracture of parietal bone), group L (n = 6, gunshot-induced comminuted fracture of bilateral femora) and group M (n = 6, combined group H + L). Gastric intramucosal pH (pHi), plasma endotoxin levels in portal vein, and plasma D-lactate levels were measured and blood samples were cultured at different intervals after trauma. The animals were sacrificed at 72 h following trauma and intestinal tissues were harvested for pathological examination and diamine oxidase (DAO) activity measurement. RESULTS: In group M at 72 h, pHi was significantly lower than that of group H and L ( P < 0.01), and plasma endotoxin level was significantly higher than that of group H (P < 0.01) and group L (P < 0.05). Simultaneously, in group M, D-lactate level was markedly higher than that of group H ( P < 0.01), and incidence of positive blood culture was much higher than that of group H and L ( P < 0.05). Necrosis and exfoliation were revealed at ileum villus top in all trauma groups, especially in group M, in which ileum DAO activity declined most significantly as well. CONCLUSION: Multiple trauma is prone to cause gastrointestinal ischemia even without hemorrhagic shock. The damage of gut barrier in multiple trauma appears to be more severe than that in one-site trauma, thereby promoting gut-derived endotoxemia and bacterial translocation and contributing to the development of endogenous infection.

Amine Oxidase (Copper-Containing)↗
PubMed2001

Surgical treatment of malignant esophageal tumors in PUMC Hospital.

To study how to prolong the postoperative survival time of the patients with malignant esophageal tumors. The clinical data of 1098 patients with malignant esophageal tumors from 1961 to 1992 were retrospectively analyzed. The deletion of fragile histamine triplet (FHIT) gene (a tumor suppressor gene) in 30 fresh esophageal samples obtained in 1996 was detected with PCR and RT-PCR method. The resectability was raised gradually and the operative morbidity and mortality decreased year by year, but there was no significant improvement on the postoperative 5-year survival rate. Delayed diagnosis and irradical resection influenced the long-term survival. The deletion of cDNA of FHIT gene was 64. 2% in esophageal cancer and 20% in the resected margin of the cancer. We believe that high-grade atypical hyperplasia in esophageal epithelium and deletion of FHIT gene in esophageal cancer and its resected margin are pathological and molecular markers for early diagnosis of esophageal cancer respectively, and the latter may be one of the molecular markers for the resection. Early diagnosis and treatment, radical, resection, and postoperative nutritional support are very important for the improvement of the postoperative survival time of the patients.

Acid Anhydride Hydrolases↗
PubMed2001

[Analysis of the plasma radiation induced by laser ablating Al at low pressure].

The plasma was obtained with Nd:YAG laser ablating aluminum. The energy of a pulsed laser beam was set up to 145 mJ. Ar gas was used as protecting gas, its pressure was set up to 100 Pa. The information of the plasma radiation was acquired with time-resolved technique. The time-resolved spectra including continuum radiation, absorption of continuum radiation and Al atomic spectral lines radiation were obtained. The evolutions of all these radiations were analyzed, and the relationship between them was discussed briefly. We found that the evolutions of all these radiation at the low pressure were similar to that of at the pressure of one atmosphere.

English Abstract↗
PubMed2001

[Establishing a model of neutropenia rat with Pseudomonas aeruginosa pneumonia and a study on its inflammatory reaction].

OBJECTIVE: To establish an animal model and study the inflammatory reaction of P. Aeruginosa pneumonia in neutropenia rats. METHODS Fifty SD rats were randomly divided into two groups: drug-treated group and control CON group. Drug-treated group was given a combination regimen of cyclophosphamide (15 m x kg(-1) d(-1)) and cortisone acetate (100 mg x kg(-1) x d(-1)) for seven days,then both groups were intratracheally challenged with P. Aeruginosa (0.2 ml ATCC 27853 6 x 10(8) CFU/ml). Their blood, bronchial alveolar lavage fluid (BALF) and lung tissue were collected before and 3, 6, 9, 24 h after challenging. Cytological and bacteriological examinations were performed, histopathologic changes of lung tissue were observed. Total proteins (TP) of BALF and the wet/dry ratio (W/D) of lung tissue were determined. RESULTS: (1) Compared with CON group, rats of drug-treated group showed obviously weight loss and thymus atrophy [(141 +/- 8) g] vs [(201 +/- 14) g], [(0.06 +/- 0.05) g] vs (0.40 +/- 0.10) g, P < 0.001], developed leukocytopenia [(0.9 +/- 0.3) x 10(9)/L] vs [(7.3 +/- 1.9) x 10(9)/L, P < 0.001] and the numbers of alveolar macrophage in BALF decreased significantly; (2) After PA challenging, drug-treated rats showed less activities, worse situations and higher mortality (10.8%) than CON group which recovered quickly and none of them died. PA was identified from samples of BALF and lung tissue, both groups developed inflammatory reaction at 6 - 9 h in high level. Pulmonary pathologic study revealed that polymorphonuclears response of drug-treated group was delayed and less serious than that of CON group [at 9 h, drug-treated group, (102 +/- 13)/HP vs CON group (291 +/- 20)/HP, P < 0.01], however, interstitial edema, capillary congestion and focal hemorrhages were more obvious; (3) After PA challenging especially at 6 - 9 h, W/D ratio and TP concentrations were significantly high in both groups than those of before [drug-treated group, W/D (9.2 +/- 1.3) vs (5.9 +/- 1.4) TP (1.59 +/- 0.83) mg/ml vs (0.19 +/- 0.07) mg/ml; CON group:W/D 7.2 +/- 2.5 vs 4.9 +/- 0.8,TP(0.42 +/- 0.16) mg/ml vs (0.13 +/- 0.04) mg/ml, P < 0.05], however the alterations were much greater in drug-treated group (P < 0.05). Alteration of TP concentration showed some correlation with numbers of polymorphonuclears in lung tissue of CON group (r = 0.926, P < 0.05), but not in drug-treated group (r = 0.58, P = 0.31). CONCLUSION: It was indicated that there may be other mechanisms than polymorphonuclears infiltration contributing to the more severe lung injury in drug-treated group characterized as neutropenia.

Animals↗
PubMed2000

Identification of domain-domain docking sites within Clostridium symbiosum pyruvate phosphate dikinase by amino acid replacement.

Potential domain-domain docking residues, identified from the x-ray structure of the Clostridium symbiosum apoPPDK, were replaced by site-directed mutagenesis. The steady-state and transient kinetic properties of the mutant enzymes were determined as a way of evaluating docking efficiency. PPDK mutants, in which one of two stringently conserved docking residues located on the N-terminal domain (Arg(219) and Glu(271)) was substituted, displayed largely unimpeded catalysis of the phosphoenolpyruvate partial reaction at the C-terminal domain, but significantly impaired catalysis (>10(4)) of the ATP pyrophosphorylation of His(455) at the N-terminal domain. In contrast, alanine mutants of two potential docking residues located on the N-terminal domain (Ser(262) and Lys(149)), which are not conserved among the PPDKs, exhibited essentially normal catalytic turnover. Arg(219) and Glu(271) were thus proposed to play an important role in guiding the central domain and, hence, the catalytic His(455) into position for catalysis. Substitution of central domain residues Glu(434)/Glu(437) and Thr(453), the respective docking partners of Arg(219) and Glu(271), resulted in mutants impaired in catalysis at the ATP active site. The x-ray crystal structure of the apo-T453A PPDK mutant was determined to test for possible misalignment of residues at the N-terminal domain-central domain interface that might result from loss of the Thr(453)-Glu(271) binding interaction. With the exception of the mutation site, the structure of T453A PPDK was found to be identical to that of the wild-type enzyme. It is hypothesized that the two Glu(271) interfacial binding sites that remain in the T453A PPDK mutant, Thr(453) backbone NH and Met(452) backbone NH, are sufficient to stabilize the native conformation as observed in the crystalline state but may be less effective in populating the reactive conformation in solution.

Adenosine Triphosphate↗
PubMed2000

Transcytosis of lipoprotein lipase across cultured endothelial cells requires both heparan sulfate proteoglycans and the very low density lipoprotein receptor.

Lipoprotein lipase (LPL), the major enzyme responsible for the hydrolysis of circulating lipoprotein triglyceride molecules, is synthesized in myocytes and adipocytes but functions while bound to heparan sulfate proteoglycans (HSPGs) on the luminal surface of vascular endothelial cells. This requires transfer of LPL from the abluminal side to the luminal side of endothelial cells. Studies were performed to investigate the mechanisms of LPL transcytosis using cultured monolayers of bovine aortic endothelial cells. We tested whether HSPGs and members of the low density lipoprotein (LDL) receptor superfamily were involved in transfer of LPL from the basolateral to the apical side of cultured endothelial cells. Heparinase/heparinitase treatment of the basolateral cell surface or addition of heparin to the basolateral medium decreased the movement of LPL. This suggested a requirement for HSPGs. To assess the role of receptors, we used either receptor-associated protein, the 39-kDa inhibitor of ligand binding to the LDL receptor-related protein and the very low density lipoprotein (VLDL) receptor, or specific receptor antibodies. Receptor-associated protein reduced (125)I-LPL and LPL activity transfer across the monolayers. When the basolateral surface of the cells was treated with antibodies, only anti-VLDL receptor antibodies inhibited transcytosis. Moreover, overexpression of the VLDL receptor using adenoviral-mediated gene transfer increased LPL transcytosis. Thus, movement of active LPL across endothelial cells involves both HSPGs and VLDL receptor.

Animals↗
PubMed2000

Phonon anomaly in high-pressure Zn

The equation of states and phonon dispersions of hexagonal zinc have been calculated by the plane-wave pseudopotential method within the generalized-gradient approximation. Weak discontinuities are found in the pressure-volume relation as well as the c/a-volume curve. Phonon dispersions of Zn under pressure have been obtained with a direct method and the results are consistent with the neutron scattering data. At V/V0 approximately 0.88, the calculated frequencies of the acoustic phonons near the zone center softened substantially as a result of an electronic topological transition. The theoretical result is consistent with the observed anomaly in the Lam-Mossbauer factor at low temperature.

Journal Article↗
PubMed2000

DNA-PKcs is required for activation of innate immunity by immunostimulatory DNA.

Bacterial DNA and related synthetic immunostimulatory oligodeoxyribonucleotides (ISS-ODN) stimulate innate immunity. However, the molecular recognition mechanism that initiates signaling in response to bacterial DNA and ISS-ODN has not been identified. Herein, we demonstrate that administration of bacterial DNA and ISS-ODN to mice lacking the catalytic subunit of DNA-PK (DNA-PKcs) and in vitro stimulation of BMDM from these mice result in defective induction of IL-6 and IL-12. Further analysis using BMDM of IKKbeta(-/-) revealed that both DNA-PKcs and IKKbeta are essential for normal cytokine production in response to ISS-ODN or bacterial DNA. ISS-ODN and bacterial DNA activate DNA-PK, which in turn contributes to activation of IKK and NF-kappaB. These results reveal a novel role of DNA-PKcs in innate immune responses and a link between DNA repair and innate immunity.

Androstadienes↗