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Biomedical subjects

L Ding

Publications and source records attributed to L Ding.

At least 109 records · Page 6Linked to original sources
PubMed1998

[The sensitivity of carcinogenic initiation effect of regenerated liver induced by diethylnitrosamine in rats].

OBJECTIVE: To compare the sensitivity of carcinogenic initiation effect of regenerated liver with normal liver induced by diethylnitrosamine (DEN) in rats. METHODS: Experimental group was composed of rats that had 2/3 of their liver excised 8 weeks previously, normal rats were used as controls to study: (1) weight of their livers, conventional histological examination and 3H-TdR incorporation test; (2) a modified Solt-Farber carcinogenesis scheme was applied in order to detect the degree of carcinogenic initiation effect by stereologic study of GGT positive preneoplastic liver cell foci; (3) damage of DNA in hepatocytes were detected by in situ nick translation test after DEN treatment both in vivo and in primary cultured liver cells. RESULTS: (1) the regenerative process in liver was completed by the end of the 8th post-operative week and no proliferation of hepatocytes was detected. (2) both the number and volume density of GGT positive foci in the experimental group were higher than those in control group. (3) DNA damage in hepatocytes of experimental group were more severe than in the control group. CONCLUSION: Even after the regeneration process was completed, the regenerated liver still possessed higher sensitivity to carcinogenic initiation effect than normal liver, this sensitivity was related with the severity of DNA damage in hepatocytes of the regenerated liver after DEN attack.

Animals↗
PubMed1998

[Relationship between oval cells and preneoplastic lesions induced by 2-acetylaminofluorene in rat liver].

OBJECTIVE: To study the cellular origin of preneoplastic lesion of liver induced by the 2-acetylaminofluorene (2-AAF) in rat. METHODS: Male fisher 344 rats were used for two different carcinogenesis models. Model 1: Rats were fed with regular diet containing 0.02% 2-AAF for totally 28 days, and subjected to a standard two thirds partial hepatectomy (2/3 PH) on the 7th day in order to stimulate the proliferation of oval cells. 3H thymidine (3H-Tdr) was administered intraperitoneally on the 12th day for selective labelling of oval cells. Model II: Rats were subjected to 2/3 PH and 3H-Tdr was administered intraperitoneally 22 hours after the operation for the selective labelling of hepatocytes. The rats were then fed with 2-AAF for totally 28 days after a 9 days recovery period from 2/3 PH. The relationship between preneoplastic lesion and selectively labelled oval cells, or hepatocytes, was traced by autoradiography. RESULTS: Pathological examination and autoradiography denoted that the silver grains (labelled signals) were only formed in the preneoplastic cells in model I rather than the cells of model II animals. CONCLUSION: It is a direct evidence to demonstrate that the preneoplastic cells are mostly originated from the oval cells.

2-Acetylaminofluorene↗
PubMed1998

Interferon-ç induces cathepsin B expression in a human macrophage-like cell line by increasing both transcription and mRNA stability.

We have demonstrated previously that treatment of the phorbol ester PMA-primed THP-1 human macrophage-like cells with interferon-ç (IFN-ç) in vitro induced time and dose-dependent increases in steady-state levels of cathepsin B (CB) mRNA. The present study was undertaken to investigate the mechanism of that increase. In vitro nuclear transcription (nuclear run-off) assays of CB gene expression were performed with purified nuclei from IFN-ç-treated or untreated THP-1 cells. These assays showed transcription to be increased approximately three-fold by IFN-ç in the PMA-primed THP-1 cells. Studies with á-amanitin indicated that the half-life of CB mRNA is prolonged after PMA and IFN-ç treatment, by more than 90%. Therefore, the elevated CB mRNA level results from a combination of IFN-ç-induced increase in the transcription rate of the CB gene and stabilization of the corresponding transcripts. The IFN-ç-mediated increase in CB gene transcription and steady-state mRNA level was blocked by á-amanitin or cycloheximide, suggesting the involvement of RNA polymerase II and the requirement of de novo protein synthesis.

Journal Article↗
PubMed1997

Carboxyl terminus of mitosin is sufficient to confer spindle pole localization.

Mitosin is a nuclear protein of 3,113 amino acids which has been shown to associate with the mitotic apparatus, especially the kinetochore, during mitosis. In this paper we further confirmed its association with the spindle poles in normal monkey kidney CV1 cells by indirect immunofluorescence microscopy. When the carboxyl portion of mitosin containing amino acids 2,094-3,113 (named mitosin-pTN) was stably expressed in rat fibroblast Rat2 cells using a tetracycline-inducible system, strong spindle pole association was observed in addition to expected centromere localization. The same results were achieved in Chinese hamster ovary (CHO) cells. On the other hand, mitosin-pTC containing amino acids 2,756-3,113 was not targeted to spindle poles. Use of the FLAG epitope [Hopp et al., 1988] genetically fused to each amino terminus of these mutants eliminated possible artifacts due to antibody cross-reaction, since the spindle pole localization of wild-type mitosin was confirmed with a FLAG-tagged mutant by an antibody (anti-FLAG M2 monoclonal antibody) irrelevant to antibodies to mitosin. Our data also suggested a possible interaction of mitosin with the spindle microtubules. Interaction of mitosin with the major parts of the mitotic apparatus further implies an important role in mitosis.

Animals↗
PubMed1997

Alternative splicing of the human diacylglycerol kinase zeta gene in muscle.

Diacylglycerol can function as a second messenger, and one mechanism for the attenuation of this signal is its conversion to phosphatidic acid, which is catalyzed by diacylglycerol kinase (DGK). We screened a cDNA library from human skeletal muscle and isolated two DGKzeta cDNAs that differed from the 3.5-kb clone originally identified in endothelial cells. One transcript, which was 3.4 kb long, was shown to be nonfunctional; it had a 77-bp deletion that included the translation initiation site. The other was 4.1 kb long with a unique 5' sequence of 853 bp. We also isolated a genomic clone of DGKzeta and determined its organization and location; it contains 32 exons, spans approximately 50 kb of genomic sequence, and maps to chromosome 11p11.2. The protein encoded by the 4.1-kb transcript contains two cysteine-rich regions, a catalytic domain, and ankyrin repeats like the endothelial form of DGKzeta, as well as a unique N-terminal domain. The coding sequence was shown to be derived from alternative splicing of the DGKzeta gene. In cells transfected with the 4.1-kb clone, we detected a 130-kDa protein with an antibody to DGKzeta and demonstrated that it was localized predominantly in the nucleus. We conclude that alternative splicing generates tissue-specific variants of DGKzeta that share some properties but may have unique ones as well.

Alternative Splicing↗
PubMed1997

harakiri, a novel regulator of cell death, encodes a protein that activates apoptosis and interacts selectively with survival-promoting proteins Bcl-2 and Bcl-X(L).

Programmed cell death is essential in organ development and tissue homeostasis and its deregulation is associated with the development of several diseases in mice and humans. The precise mechanisms that control cell death have not been elucidated fully, but it is well established that this form of cellular demise is regulated by a genetic program which is activated in the dying cell. Here we report the identification, cloning and characterization of harakiri, a novel gene that regulates apoptosis. The product of harakiri, Hrk, physically interacts with the death-repressor proteins Bcl-2 and Bcl-X(L), but not with death-promoting homologs, Bax or Bak. Hrk lacks conserved BH1 and BH2 regions and significant homology to Bcl-2 family members or any other protein, except for a stretch of eight amino acids that exhibits high homology with BH3 regions. Expression of Hrk induces cell death which is inhibited by Bcl-2 and Bcl-X(L). Deletion of 16 amino acids including the conserved BH3 region abolished the ability of Hrk to interact with Bcl-2 and Bcl-X(L) in mammalian cells. Moreover, the killing activity of this mutant form of Hrk (Hrk deltaBH3) was eliminated or dramatically reduced, suggesting that Hrk activates cell death at least in part by interacting with and inhibiting the protection afforded by Bcl-2 and Bcl-X(L). Because Hrk lacks conserved BH1 and BH2 domains that define Bcl-2 family members, we propose that Hrk and Bik/Nbk, another BH3-containing protein that activates apoptosis, represent a novel class of proteins that regulate apoptosis by interacting selectively with survival-promoting Bcl-2 and Bcl-X(L).

Amino Acid Sequence↗
PubMed1997

A role for arabinogalactan-proteins in root epidermal cell expansion.

Arabinogalactan-proteins (AGPs) are abundant plant proteoglycans that react with (beta-D-Glc)3 but not (beta-D-Man)3 Yariv reagent. We report here that treatment with (beta-D-Glc)3 Yariv reagent caused inhibition of root growth of Arabidopsis thaliana (L.) Heynh. seedlings. Moreover, the treated roots exhibited numerous bulging epidermal cells. Treatment with (beta-D-Man)3 Yariv reagent did not have any such effects. These results indicate a role for AGPs in root growth and control of epidermal cell expansion. Because treatment with (beta-D-Glc)3 Yariv reagent phenocopies the reb1 (root epidermal cell bulging) mutant of Arabidopsis, AGPs were extracted from the reb1-1 mutant and compared with those of the wild type. The reb1-1 roots contained an approximately 30% lower level of AGPs than the wild type. More importantly, while the profile of AGPs from wild-type roots showed two major peaks upon crossed electrophoresis, the profile of AGPs from reb1-1 roots exhibited only one of the major peaks. Therefore, the reb1 phenotype appears to be a result of defective or missing root AGPs. Taken together, this pharmacological and genetic evidence strongly indicates a function of AGPs in the control of root epidermal cell expansion.

Arabidopsis↗
PubMed1997

In vitro packaging of an infectious recombinant adeno-associated virus 2.

Adeno-associated virus 2 (AAV), a human parvovirus, has properties such as stable chromosomal integration, high infectivity and lack of known human pathogenicity, making it a potentially useful vector for human gene therapy. AAV requires a helper virus, such as an adenovirus, for optimal replication and packaging in mammalian cells. Although replication of the wild-type AAV genome has been demonstrated in vitro, packaging of infectious viral particles was not documented until now. In this study, we produced in vitro infectious recombinant AAV virions containing the neomycin resistance (NeoR) and the human CD-16 (FC gamma RIIIa) gene. Our in vitro packaging of AAV has the same characteristics as AAV produced in vivo and demonstrates the feasibility of developing a safe packaging method for AAV to be used in gene therapy.

DNA, Recombinant↗
PubMed1997

Reduced Na+ uptake in the NaCl-hypersensitive sos1 mutant of Arabidopsis thaliana.

Sos1 is an Arabidopsis thaliana mutant with > 20 times higher sensitivity toward Na+ inhibition due to a defective high-affinity potassium-uptake system. We report here that sos1 accumulates less Na+ than the wild type in response to NaCl stress. The Na+ contents in sos1 seedlings exposed to 25 mM NaCl for 2 or more d are about 43% lower than those in the wild type. When assayed at 20 mM external NaCl, sos1 seedlings pretreated with low potassium have 32% lower Na+ uptake than the wild type. However, little difference in Na+ uptake could be measured when the seedlings were not pretreated with low potassium. Low-potassium treatment was shown to induce high-affinity potassium-uptake activity in Arabidopsis seedlings. No substantial difference in Na+ efflux between sos1 and the wild type was detected. The results show that the reduced Na+ accumulation in sos1 is due to a lower Na+ influx rate. Therefore, the sos1 mutation appears to disrupt low-affinity Na+ uptake in addition to its impairment of high-affinity K+ uptake.

Arabidopsis↗
PubMed1997

Performance evaluation of a diode array for enhanced dynamic wedge dosimetry.

The performance of a diode array (Profiler) was evaluated by comparing its enhanced dynamic wedge (EDW) profiles measured at various depths with point measurements using a 0.03 cm3 ionization chamber on a commercial linear accelerator. The Profiler, which covers a 22.5 cm width, was used to measure larger field widths by concatenating three data sets into a larger field. An innovative wide-field calibration technique developed by the manufacturer of the device was used to calibrate the individual diode sensitivity, which can vary by more than 10%. Profiles of EDW measured with this device at several depths were used to construct isodose curves using the percentage depth dose curve measured by the ionization chamber. These isodose curves were used to check those generated by a commercial treatment planning system. The profiles measured with the diode array for both 8 and 18 MV photon beams agreed with those of the ionization chamber within a standard deviation of 0.4% in the field (defined as 80% of the field width) and within a maximum shift of less than 2 mm in the penumbra region. The percentage depth dose generally agreed to within 2% except in the buildup region. The Profiler was extremely useful as a quality assurance tool for EDW and as a dosimetry measurement device with tremendous savings in data acquisition time.

Humans↗
PubMed1997

[An experimental study of bioactive glass ceramics as orbital implants].

One eyeball of experimental rabbits was enucleated in routine procedure, and then implanted the biocative glass ceramic (BGC). No rejection was observed during the postoperation period. After three months of implantation, they were examined with ultrasound, and a venous-flow-like spectra was detected in the ceramic implant. After six months of implantation, the implans were examined histologically; the ingrowth fibrovascular tissue filled the 90% gaps of the implant. The results suggest that the bioactive glass ceramic implants made in China possess acceptable histocompatibility.

Animals↗
PubMed1996

Activated B cells express CD28/B7-independent costimulatory activity.

Resting and activated B cells display distinct phenotypes and functional properties. Resting B cells are incompetent accessory cells whereas activated B cells are capable of triggering T cell activation. The up-regulation of expression of the B7 family of molecules has been considered to be the primary reason for this functional conversion of activated B cells. We report here that activation of B cells induces a novel costimulatory activity for induction of T cell proliferation, which is independent of the CD28/B7 costimulatory pathway. B cells activated by different stimuli expressed comparable levels of many of the known counter-receptors for costimulation and intercellular adhesion (B7-1, B7-2, HSA, ICAM-1), but differed markedly in their capacity to activate CD4+ T cells from CD28-deficient (-/-) mice. Activation of B cells via CD40, and to a lesser extent with LPS, induced potent B7/CD28-independent costimulatory activity that resulted in marked augmentation of IL-2-mediated proliferative responses of CD4+ T cells from CD28 -/- mice. The B7/CD28-independent costimulatory pathway was capable of triggering the activation of naive CD4+ T cells, as both sorted CD45RBhigh and isolated high density naive CD4+ T cells from CD28 -/- mice responded vigorously to the costimulation provided by CD40L-activated B cells.

Animals↗
PubMed1996

Scintigraphic Study of Local Flux and Osmotic Pressure Distributions in Ultrafiltration of Blood and Plasma.

We have investigated the spatial variation of local protein concentration and filtration flux by a scintigraphic technique in the ultrafiltration of bovine albumin solutions and blood. The feed was mixed with (99m)Tc albumin macroaggregates and circulated through a polysulfone 30,000 MWCO hollow fiber filter placed in the field of a gamma-camera. Concentration profiles c(b) (x) were reconstructed from scintigraphic images and the local ultrafiltration flux was calculated by differentiating c(b) (x) and using mass conservation. Tests were run at various inlet shear rates from 472 to 1415 s(-1) and under two different filtration regimes: no net filtration (permeate valve closed) and large filtration (below the pressure independent plateau). The data confirm the filtration decay from the filter inlet to outlet but an unexpected result is the presence of high retrofiltration in the downstream part of the filter length in the case of large filtration. This retrofiltration can be explained by a high osmotic pressure at the membrane created by the protein polarization concentration. Assuming a constant pressure gradient along the fibers, it is possible to estimate the local osmotic pressure at the onset of retrofiltration and to infer from it the protein concentration at the membrane, which is found to vary from 170 to 250 g/liter when gamma(w) increases. Similar experiments were run with blood and a microfiltration membrane (0.55-µm pores). In that case no retrofiltration was obtained, which confirms our explanation since in this case the polarization layer is composed of red cells which exert no osmotic pressure.

Journal Article↗
PubMed1996

Lung cancer risk in relation to the CYP2E1 Rsa I genetic polymorphism among African-Americans and Caucasians in Los Angeles County.

Genetic polymorphisms in the activation or detoxication of carcinogens, such as those in tobacco smoke, may produce differences in individual susceptibility to lung cancer. The cytochrome P450 CYP2E1 is an enzyme involved in the metabolism of nitrosamines in tobacco smoke. A polymorphism of CYP2E1 detectable by the restriction enzyme Rsa I may be functionally important because it is located in a putative binding site for the transcription factor HNF-1 and has been associated with higher levels of CYP2E1 transcription. It is conceivable that this CYP2E1 Rsa I polymorphism might contribute to differences in susceptibility to lung cancer. We conducted a case-control study of patients with incident lung cancer and population controls in Los Angeles County to examine the association between the CYP2E1 Rsa I polymorphism and lung cancer risk among African-Americans and Caucasians. Samples of white blood cell DNA sufficient for determination of the CYP2E1 Rsa I genotype by a polymerase chain reaction-based assay were obtained from 341 cases and 706 controls with data on lifetime smoking history. No subjects were homozygous for the CYP2E1 Rsa I rare c2 allele. The rare c2 allele was not associated with an increased risk of lung cancer (adjusted odds ratio, OR 0.72; 95% confidence interval, CI = 0.35-1.46). Among the population controls the percentage of subjects carrying the rare c2 allele was lower (p = 0.002) among African-Americans (2%) compared with Caucasians (8%). However, the association between the CYP2E1 Rsa I genotype and lung cancer risk did not differ between ethnic groups. There was no important association between the CYP2E1 Rsa I genotype and lung cancer risk in analyses stratified by cell-type, smoking history, gender, occupational asbestos exposure, and dietary intake of antioxidants vitamin C, vitamin E or beta carotene. Due to the low frequency of the c2 allele in these populations, larger studies would be necessary to rule out a modest association between the CYP2E1 Rsa I polymorphism and lung cancer risk.

Adult↗
PubMed1996

[Detection of placental alkaline phosphatase in ovarian cancer].

OBJECTIVE: To establish a method for diagnosis of malignant tumors by determination of the placental alkaline phosphatase (PLAP) in serum. METHODS: A solid phase enzyme immunoassay was adopated by an antibody against PLAP. PLAP in serum of 81 patients with malignant tumor and 86 healthy people as control were determined. RESULTS: In the control group, the PLAP activity showed deviative distribution, the 95th percentile values of PLAP in control group was 3.8U/L. If this value served as normal cut-off line, 18 cases among 81 patients with malignant tumors were positive. The positive rate was 22.2%, but the positive rates in ovarian cancer was 61.9%. CONCLUSIONS: The increasing of serum PLAP may be helpful for the diagnosis of malignant tumors especially ovarian cancer.

Alkaline Phosphatase↗
PubMed1995

B7/CD28-dependent and -independent induction of CD40 ligand expression.

The induction of a T cell-dependent Ab response is mediated by the interaction of the T cell activation Ag, CD40 ligand (CD40L), with CD40. Since this interaction is independent of Ag, coreceptors such as CD4, and MHC molecules, the expression of the CD40L must be strictly regulated or B cell-mediated autoimmunity may be produced. In this study, we examined the requirements for costimulatory signals for induction of CD40L expression in vitro and in vivo on CD4+ T cells from normal and CD28-deficient mice following stimulation with anti-CD3, Con A, or specific peptide Ag. Expression of B7-1 was both necessary and sufficient for induction of the CD40L on normal CD4+ T cells when L cell transfectants were used as APCs. When normal accessory cell populations were used, only partial inhibition of induction of the CD40L was observed with reagents that inhibit B7/CD28 interactions. Furthermore, the CD40L could be induced on CD4+ T cells from CD28-deficient mice. Thus, non-B7/CD28 cellular interactions can also mediate the costimulatory signals needed for induction of CD40L expression.

Animals↗