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Biomedical subjects

Z Zheng

Publications and source records attributed to Z Zheng.

At least 55 records · Page 3Linked to original sources
PubMed2001

Nutrient cycling in a tropical seasonal rain forest of Xishuangbanna, Southwest China. Part 1: tree species: nutrient distribution and uptake.

Tropical rain forests are characterized by large numbers of the species with diverse growth habits. The objective of the present study was to determine the distribution of nutrient content in the major trees of the tropical rain forests in Xishuangbanna. This will improve the understanding of the nutrient losses from such sites that result from harvesting and flow of nutrients within the ecosystem and lead to the development of effective and rational forest management strategies. Based on the results in this study, the distribution of nutrients among biomass components of trees varied: The ordering of major elements concentrations was K > N > Mg > Ca > P in branch, stem and root tissues but was N > K > Mg > Ca > P in leaves. The maximum amount of all nutrients per ha occurred in the stems followed by branches, roots and leaves. Of the total uptake of 6167.7 kg ha(-1) of all nutrients, the contribution of various nutrients was found to be N (2010.6 t ha(-1)), P (196.3 t ha(-1)), K (2123.8 kg ha(-1)), Ca (832 kg ha(-1)) and Mg (1005 kg ha(-1)). However, comparing the nutrient uptake of other tropical and sub tropical forests, the results indicated that rates for the Xishuangbanna forests were 20-35% lower than previously reported values.

Biomass↗
PubMed2001

Sexual behaviour and contraceptive use among unmarried, young women migrant workers in five cities in China.

This paper reports the results of exploratory research on reproductive and sexual health knowledge and sexual behaviour of young, unmarried women who migrate to cities from rural areas for work, and their access to and needs in relation to family planning in Beijing, Guangzhou, Shanghai, Guiyang and Taiyuan, in China. Focus group discussions were conducted with 146 young women aged 16-25 and 58 in-depth interviews with key informants. Some of the young female migrant workers were sexually active and living with their boyfriends, most of whom expected to marry each other. Most of the women lacked basic information about reproduction and contraception, and did not know where or how to obtain contraception. There were social, psychological and economic barriers to accessing services. Only a small proportion of those who were unmarried were using contraception, so induced abortion was often the outcome of unprotected premarital sex. Pleasing male partners also played an important role in unprotected sex. The training, attitudes and approach of the entire family planning service system in relation to unmarried and young people in China, including this migrant population, needs to be reorientated so as to provide them with appropriate and adequate services.

Abortion, Induced↗
PubMed2001

Antitumor and antifungal activities in endophytic fungi isolated from pharmaceutical plants Taxus mairei, Cephalataxus fortunei and Torreya grandis.

The purpose of this work was to screen the endophytic fungi having antitumor or antifungal activity, which were isolated from the inner barks of three kinds of pharmaceutical plants, Taxus mairei, Cephalataxus fortunei and Torreya grandis, collected from Fujian province, China. Antitumor activity was studied by the MTT assay and antifungal activity was determined by observing fungal growth inhibition. 13.4% of endophytic fungi fermentation broths displayed cytotoxic activity on HL-60 cells at and below a dilution of 1:50, and 6.4% on KB cells. 52.3% of endophytic fungi fermentation broths displayed growth inhibition on at least one pathogenic fungi, such as Neurospora sp., Trichoderma sp. and Fusarium sp. Among all endophytic fungi isolated, the genus Paecilomyces sp. has the highest positive rate of antitumor and antifungal activity. These results indicate that endophytic fungi could be a promising source for antitumor and antifungal bioactive agents.

Antifungal Agents↗
PubMed2001

A formalism for independent checking of Gamma Knife dose calculations.

For stereotactic radiosurgery using the Leksell Gamma Knife system, it is important to perform a pre-treatment verification of the maximum dose calculated with the Leksell GammaPlan (DLGP) stereotactic radiosurgery system. This verification can be incorporated as part of a routine quality assurance (QA) procedure to minimize the chance of a hazardous overdose. To implement this procedure, a formalism has been developed to calculate the dose DCAL(X,Y,Z,dav,t) using the following parameters: average target depth (dav), coordinates (X,Y,Z) of the maximum dose location or any other dose point(s) to be verified, 3-dimensional (3-dim) beam profiles or off-centerratios (OCR) of the four helmets, helmet size i, output factor Oi, plug factor Pi, each shot j coordinates (x,y,z)i,j, and shot treatment time (ti,j). The average depth of the target dav was obtained either from MRI/CT images or ruler measurements of the Gamma Knife Bubble Head Frame. DCAL and DLGP were then compared to evaluate the accuracy of this independent calculation. The proposed calculation for an independent check of DLGP has been demonstrated to be accurate and reliable, and thus serves as a QA tool for Gamma Knife stereotactic radiosurgery.

Biophysical Phenomena↗
PubMed2001

Gamma knife surgery for treatment of central neurocytomas. Report of four cases.

The authors investigated the use of gamma knife surgery (GKS) in the treatment of central neurocytoma, a usually benign primary brain tumor of the lateral and third ventricles. Four patients with subtotally resected or recurrent central neurocytomas were retrospectively studied. The prescription isodose was 9 to 13 Gy to the 30 to 50% peripheral isodose line. Pre- and postoperative magnetic resonance (MR) images were compared to determine the volume reduction following GKS. Follow-up review included annual MR imaging and clinical evaluation by a neurosurgeon. Follow-up periods ranged from 12 to 99 months. Marked reduction in tumor size was seen in all four patients; the decrease in tumor volume for each was 48%, 72%, 81%, and 77%, respectively, at the last follow-up review. None of the four patients required additional treatment and none experienced a decline in neurological function during the follow-up period. No complications have been noted in any of these patients to date. Even though there have been few observations and follow-up time has been limited, because of the consistency of the response and the lack of observed side effects, GKS may be the treatment of choice for subtotally resected and recurrent central neurocytomas.

Adult↗
PubMed2001

"Hybrid" revascularization: video-thoracoscopy assisted MIDCAB combined with angioplasty.

A "hybrid" revascularization technique has been developed for cases in which a chronic total occlusion of the left anterior descending coronary artery (LAD) cannot be recanalized by percutaneous coronary intervention, but the lesions in the right coronary artery and/or left circumflex artery are very good candidates for angioplasty. This technique, which uses video-thoracoscopy assisted minimally invasive direct coronary artery bypass to recanalize the occluded LAD and angioplasty to dilate favorable lesions in other vessels, would achieve complete revascularization in selected patients with multi-vessel disease. In this preliminary study of four patients, angioplasty and stenting were successful in all patients without any complications; complete revascularization was achieved in all 4 patients. No recurrence of angina and no cardiovascular events developed during follow-up; this study therefore supports the belief that the "hybrid" revascularization technique is both feasible and safe.

Adult↗
PubMed2001

Peritoneal dialysis solutions disturb the balance of apoptosis and proliferation of peritoneal cells in chronic dialysis model.

The present study investigated variation in apoptosis and proliferation, and the balance between apoptosis and proliferation, for peritoneal mesothelial cells (MCs) after exposure to peritoneal dialysis solution (PDS) in vivo. We implanted 32 male Sprague-Dawley rats (4 groups; n = 8 in each group) with catheters and intraperitoneally infused the animals with 20 mL Dianeal 1.36%, 2.27%, or 3.86% (Baxter Healthcare Corporation, Deerfield, IL, U.S.A.) PDS twice daily for eight consecutive weeks, using saline as a control. At the end of the eighth week, samples of peritoneal membrane were fixed and sliced. Expression of apoptosis was checked with TUNEL kits (Boehringer Mannheim, Mannheim, Germany), and expression of proliferative cell nuclear antigen (PCNA) was checked by immunohistochemistry [streptoavidin-biotin-peroxidase complex (SABC) method]. The ratio of MC apoptosis to proliferation was measured from the same slices using the dual-stain combination of TUNEL and SABC. Cells positive for apoptosis and PCNA were counted for all samples by light microscopy in 50 consecutive grids (10 x by 40). Peritoneal dialysis solution was found to significantly induce MC apoptosis as compared with control at the end of the eighth week. The degree of apoptosis was proportional to the concentration of glucose in the PDS. The 1.36% PDS, but not the 2.27% or 3.86%, significantly stimulated the expression of PCNA. The degree of PCNA expression was negatively related to the glucose concentration of the PDS. The MC apoptosis: PCNA ratio was significantly higher for 3.86% and 2.27% PDS than for the control, but no significant difference was seen between 1.36% PDS and control. We conclude that glucose-based PDS may induce apoptosis and disturb the balance of MC apoptosis and proliferation, and that 1.36% PDS damages the balance less than does 2.27% or 3.86% PDS. These effects may be partly due to pH, calcium, hyperosmolality, and glucose degradation products (GDPs). Loss of balance between MC proliferation and apoptosis--induced by unphysiologic PDS--may be one of the major causes of peritoneal membrane failure during long-term continuous ambulatory peritoneal dialysis.

Animals↗
PubMed2001

Telomerase activity and homozygous deletions of the p16 gene in liver metastases of colorectal carcinoma.

OBJECTIVE: To study the interaction between telomerase activity and abnormalities of the p16 gene in liver metastases of colorectal carcinoma. METHODS: Telomerase activity was detected by a non-isotopic PCR-based telomeric repeat amplification protocol (TRAP) assay, and homozygous deletions of the p16 gene were detected by a semiquantitative multiplex polymerase chain reaction in tissue samples from 24 liver metastases of colorectal carcinoma and 5 primary colorectal carcinomas. RESULTS: Telomerase activity was observed in 19 (79.2%) of 24 liver metastases of colorectal carcinoma. Telomerase activity was also observed in all 5 primary colorectal carcinomas and in 3 of their liver metastatic samples. The incidence of telomerase activity in liver metastases of colorectal carcinoma was not significantly correlated to tumor diameter, number of tumors, cirrhosis, and HBsAg. Homozygous deletions of the p16 gene were found in 9 of 24 (37.5%) liver metastases of colorectal carcinoma. Homozygous deletions of the p16 gene were observed in 2 of the 5 primary colorectal carcinomas and in 1 of the matching liver metastatic cancers. There was a correlation between telomerase activity and homozygous deletions of the p16 gene. CONCLUSIONS: There is a correlation between telomerase activity and homozygous deletions of the p16 gene in liver metastases of colorectal carcinoma, suggesting its crucial role in liver metastases. However, telomerase activation and homozygous deletions of the p16 gene might not be the initiating event in liver metastases of colorectal carcinoma.

Colorectal Neoplasms↗
PubMed2001

[New advances in research of combined pollution].

Combined pollution has become one of the important directions of environmental science at present. In this paper, new advances of studies on combined pollution were summarized. The studies of inorganic combined pollution, inorganic-organic combined pollution and organic combined pollution were reviewed. The mechanisms of combined pollution were approached from chemistry, physiology, enzymology, cytology and molecular biology. Then some problems and developing aspects on the research of combined pollution were put forward.

Environmental Pollutants↗
PubMed2001

Endocytic routes of exogenous antigen in murine dendritic cells and macrophages.

OBJECTIVE: To compare the endocytic routes of exogenous antigen between murine dendritic cells (DCs) and macrophages (M phi s). METHODS: Murine bone marrow-derived DCs and peritoneal M phi s were pulsed with horseradish peroxidase (HRP)-5 nm colloidal gold for 10 minutes, then grouped and chased for 0-120 minutes in culture medium. Intracellular distribution of 5 nm colloidal gold was explored by means of the cellular enzymatic-chemistry of acid phosphatase and MHC II immuno-cytochemistry under electron microscope. RESULTS: After 10 minutes of pulse with HRP-5 nm colloidal gold and 30 minutes of chase, most HRP-5 nm gold particles internalized by DCs entered into MHC class II compartments (M II Cs), and a small portion entered into acid phosphatase-positive lysosomes. In contrast to DCs, most M phi s lysosomes were accessed by HRP-5 nm gold particles, and a small portion of HRP-5 nm gold particles entered into M II Cs. After 60 minutes of chase, 5 nm gold particles could hardly be seen within M phi s, whereas most 5 nm gold particles were still retained in DCs. CONCLUSIONS: The endocytic route of exogenous antigen in DCs seems to be different from that in M phi s. Antigens taken by M phi s mainly enter into lysosomes within 30 minutes. In the case of DCs, most internalized antigens enter into M II Cs, which may be related to their unique antigen-presenting function. In addition, M phi s seem to have more powerful capacity to scavenge exogenous antigen than DCs.

Acid Phosphatase↗
PubMed2001

[Experiment study of the effect of enhanced external counterpulsation on shear stress].

This study inquired into the therapeutic mechanism of external counterpulsation(ECP) in the treatment of myocardial ischemia. Blood flow was measured at the arteria carotics, truncus brachiocephalics and other places in six chest-open dogs, and shear stress was operated. The statistical results show that the average, the range of change, and the changing rate were augmented with ECP, i.e. the phasic characteristics of shear stress were increased.

Animals↗
PubMed2001

[The expression and clinical significance of proliferative antigen Ki-67 and apoptosis-antagonizing antigen Bcl-2 in non-Hodgkin's lymphoma].

OBJECTIVE: To evaluate the expression of proliferative antigen Ki-67 and apoptosis-antagonizing protein Bcl-2 as well as their clinical significance in non-Hodgkin's lymphoma (NHL). METHODS: Ki-67 antigen and Bcl-2 protein were measured by immunohistochemistry on paraffin -embedded slices in 35 cases of NHL. RESULTS: (1) The level of Ki-67 expression in low grade NHL was lower than that in high grade NHL (P < 0.01),while Bcl-2 expression in lower grade NHL was higher than that in high grade (P < 0.01). (2) The level of Bcl-2 expression in B cell NHL was higher than that in T cell NHL (P < 0.02), but there was no difference in the expression of Ki-67. (3) The level of Bcl-2 expression in remission group was lower than that in non-remission group after the first course of chemotherapy, but there was no significant difference in Ki-67 expression. (4) The survival time was longer in the group with Ki-67 < or = 20% than that in the group with Ki-67 > 20%, but there was no significant difference of survival time between the high and low expression group of Bcl-2. CONCLUSIONS: The level of Ki-67 and Bcl-2 expression was closely related with the grade of malignant and the prognosis of NHL. They were a pair of useful markers for understanding the generation and prognosis of NHL.

Adolescent↗
PubMed2000

A maize sesquiterpene cyclase gene induced by insect herbivory and volicitin: characterization of wild-type and mutant alleles.

Plants can defend themselves from herbivorous insects by emitting volatile chemical signals that attract natural enemies of the herbivore. For example, maize seedlings attacked by beet armyworm larvae (Spodoptera exigua) produce a mixture of terpenoid and indole volatiles that serve to attract parasitic wasps. A key step in terpenoid biosynthesis is the conversion of acyclic prenyl diphosphates to terpenoid compounds by specific terpenoid synthases (cyclases). We have cloned a maize sesquiterpene cyclase gene, stc1, by transposon tagging and have identified two deletion mutations of the gene. The stc1 gene is located on chromosome 9S and does not seem to have a closely related ortholog in the maize genome. It is induced 15- to 30-fold in maize leaves by beet armyworm larvae feeding or by application of purified volicitin, the insect-derived elicitor, at a mechanically wounded site. stc1 induction is systemic, because undamaged leaves of the same plant show a similar increase in stc1 transcription. Analysis of volatiles from volicitin-treated seedlings revealed that a major naphthalene-based sesquiterpene was present in wild-type seedlings but absent in the Ac-insertion and x-ray-deletion mutants. Therefore, we have identified a maize gene that responds to caterpillar herbivory by producing a chemical defense signal that most likely serves to attract natural enemies of the herbivore.

Alleles↗
PubMed2000

Taxol from Tubercularia sp. strain TF5, an endophytic fungus of Taxus mairei.

The diterpenoid taxol is an important anticancer agent used widely in the clinic. The purpose of this work was to identify a taxol-producing endophytic fungus (strain TF5) isolated from Taxus mairei and study its anticancer activities. Strain TF5 was identified as a Tubercularia sp. according to the morphology of the fungal culture, the mechanism of spore production and the characteristics of the spores. Strain TF5 produced taxol, when grown in potato dextrose liquid medium and analyzed by thin layer chromatography, high performance liquid chromatography, ultraviolet and mass spectrometry. The fungal taxol, which was isolated from the organic extract of the TF5 culture, had strong cytotoxic activity towards KB and P388 cancer cells in vitro, tested by the MTT assay. Observed with immunofluorescence and electron microscopy, the fungal taxol enhanced microtubule stability and bundling in culture cells and induced tubulin polymerization in vitro similar to the authentic taxol.

Animals↗
PubMed2000

Induction of ref-1 ensures AP-1 activation in intracellular oxidative environment of IL-2-stimulated BA/F3beta cells.

Our previous study of interleukin-2 (IL-2) signaling found that redox factor-1 (Ref-1) mRNA was upregulated by IL-2. In this study, we further studied the function of Ref-1 in the potential redox regulation of IL-2 signaling in BA/F3beta cells. Western blot analysis confirmed that IL-2 stimulation increases Ref-1 protein. Flow cytometric assay by using 2',7'-dichlorofluorescin diacetate indicated that IL-2 stimulation results in an oxidative shift of intracellular environment. However, IL-2-induced activator protein-1 (AP-1) is oxidation-sensitive. Gel shift assays of nuclear extracts immunodepleted of Ref-1 protein demonstrated that IL-2-induced AP-1 DNA binding is dependent on the presence of Ref-1. This was further confirmed by the restoration of AP-1 DNA binding upon the re-addition of immunoprecipitated Ref-1. Additionally, reporter gene assays showed that AP-1 transcriptional activity was enhanced by the overexpression of Ref-1 and attenuated by the introduction of antisense Ref-1. These results suggest that the induction of Ref-1 ensures AP-1 activation in the intracellular oxidative environment of IL-2-stimulated BA/F3beta cells.

Base Sequence↗
PubMed2000

A mouse model of galactose-induced cataracts.

Galactokinase (GK; EC 2.7.1.6) is the first enzyme in the metabolism of galactose. In humans, GK deficiency results in congenital cataracts due to an accumulation of galactitol within the lens. In an attempt to make a galactosemic animal model, we cloned the mouse GK gene (Glk1) and disrupted it by gene targeting. As expected, galactose was very poorly metabolized in GK-deficient mice. In addition, both galactose and galactitol accumulated in tissues of GK-deficient mice. Surprisingly, the GK-deficient animals did not form cataracts even when fed a high galactose diet. However, the introduction of a human aldose reductase transgene into a GK-deficient background resulted in cataract formation within the first postnatal day. This mouse represents the first mouse model for congenital galactosemic cataract.

Aldehyde Reductase↗
PubMed2000

Detection of antitumor and antimicrobial activities in marine organism associated actinomycetes isolated from the Taiwan Strait, China.

The purpose of this work was to screen the actinomycetes having antitumor or antimicrobial activity, which were isolated from the surface, epidermis and intestines of sea plants and animals collected from the Taiwan Strait, China. Antitumor activity was studied by the MTT assay and DNA target activity was studied by the biochemical induction assay while antimicrobial activity was determined by observing bacterial and fungal growth inhibition. 20. 6% of marine actinomycete cultures displayed cytotoxic activity on P388 cells at dilutions at and below 1:320 and 18.6% on KB cells. 2. 96% of marine actinomycete cultures displayed inducing activity. Among all marine actinomycetes isolated, the genus Micromonospora has the highest positive rate of inducing activity. However, most antimicrobial activity was found in the genus Streptomyces. These results indicate that marine organism associated actinomycetes could be a promising source for antitumor and antimicrobial bioactive agents.

Actinomycetales↗