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Biomedical subjects

H Zheng

Publications and source records attributed to H Zheng.

At least 289 records · Page 16Linked to original sources
PubMed1997

Pharmacological basis for a novel therapeutic strategy based on the use of aquated cisplatin.

In pursuit of a strategy for increasing delivery of platinum drugs to tumors, we compared the cytotoxicity, extent of cellular uptake, and DNA platination of native cisplatin (DDP) and aquated cisplatin (aqDDP) in human head and neck carcinoma UMSCC10b cells. AqDDP was 1. 8-fold more toxic than DDP when tested against UMSCC10b cells in vitro. At high concentrations, aqDDP uptake was 3-fold more rapid than that of DDP; uptake of DDP and aqDDP was nonsaturable up to a concentration of 1600 micrometer. AqDDP produced 6.4-fold more platination of DNA than did DDP at the same concentration, suggesting that once inside the cell, aqDDP was 2-fold more effective at producing adducts in DNA than the native drug. Despite the paradox that aqDDP, which contains some charged species, entered the cell more rapidly than did neutral native DDP at high concentrations, studies on the effect of temperature, ATP depletion, and sulfhydryl group blockade did not provide evidence for uptake of aqDDP via a channel or transporter. AqDDP was more nephrotoxic to mice than DDP; however, s.c. administration of sodium thiosulfate protected against this toxicity and permitted a 7-fold escalation of aqDDP dose. These studies provide the preclinical basis for a novel therapeutic strategy based on the regional intraarterial or intracavitary administration of aqDDP in combination with a systemic neutralizing agent.

Adenosine Triphosphate↗
PubMed1997

In vitro antineoplastic activity of a novel lanthionine-containing peptide.

It has been a long-term goal to discover peptides that can kill tumor cells while sparing normal tissues. Lan-7 is a novel, chemically stable peptide structurally related to somatostatin that contains a lanthionine bridge between the two cysteines in the peptide; TT-232 is a less stable analogue containing a disulfide bridge. The antitumor activity of Lan-7 was examined, relative to that of TT-232 and the clinically used analogue octreotide, against a panel of malignant human tumor cell lines and normal human hematopoietic precursors. Lan-7 was cytotoxic to all four tumor cell lines, with IC50 values ranging over a 2-fold range from 16 to 36 microM. The potency of Lan-7 was comparable to that of TT-232, and both of these agents were two to three times more potent than octreotide. At concentrations that were highly cytotoxic to tumor cells, Lan-7 produced no significant toxicity to normal human hematopoietic precursors. Lan-7 induced apoptosis in human ovarian carcinoma 2008 cells over the same concentration range at which it produced cytotoxicity, but it did so without activating G1, S, or G2 checkpoints, given that it produced no perturbation of cell cycle phase distribution. Cells engineered to overexpress P-glycoprotein were not more resistant to Lan-7 than isogeneic cells not expressing the mdr1 gene. These results make Lan-7 of interest as a potential cancer chemotherapeutic agent.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

[A comparative study of laryngeal reinnervation from the ansa cervicalis].

A comparative study of four methods of laryngeal muscle reinnervation in dogs is presented. Twenty-eight cases were divided into four groups to undergo main branch and branch of ansa cervicalis nerve anastomosis, and nerves implantation an neuromuscular pedicles transfer respectively for restoration of vocal cord adduction on left sides. The results showed that the four procedures seemed to induce effective reinnervation of adductor muscles. But the main branch of ansa cervicalis nerve suture was superior to the other methods among which little difference was noted in the functional recovery, electrophysiological activity and muscle strength. It demonstrated that main branch of ansa nerve suture was the best procedure for treatment of unilateral vocal cord paralysis among the four methods.

Animals↗
PubMed1996

The role of DNA mismatch repair in platinum drug resistance.

Loss of DNA mismatch repair occurs in many types of tumors. The effect of the loss of DNA mismatch repair activity on sensitivity to cisplatin and a panel of analogues was tested using two pairs of cell lines proficient or deficient in this function. HCT116+ch2, a human colon cancer cell line deficient in hMLH1, was 2.1-fold resistant to cisplatin and 1.3-fold resistant to carboplatin when compared to a subline complemented with chromosome 3 expressing a wild-type copy of hMLH1. Likewise, the human endometrial cancer cell line HEC59, which is deficient in hMSH2, was 1.8-fold resistant to cisplatin and 1.5-fold resistant to carboplatin when compared to a subline complemented with chromosome 2 with a wild-type hMSH2. In contrast to cisplatin and carboplatin, which form the same types of adducts in DNA, there was no difference in sensitivity between the DNA mismatch repair-proficient and -deficient cell lines for oxaliplatin, tetraplatin, transplatin, JM335, or JM216. The formation of protein-DNA complexes that contained hMSH2 and hMLH1 was documented by mobility shift assay when nuclear extracts were incubated with DNA platinated with cisplatin but not with oxaliplatin. These results demonstrate a correlation between failure of the DNA mismatch repair proteins to recognize the platinum adduct and low-level resistance, suggesting a role for the DNA mismatch repair system in generating signals that contribute to the generation of apoptotic activity. They also identify the use of drugs whose adducts are not recognized as a strategy for circumventing resistance due to loss of DNA mismatch repair.

Adaptor Proteins, Signal Transducing↗
PubMed1996

UNC-40, a C. elegans homolog of DCC (Deleted in Colorectal Cancer), is required in motile cells responding to UNC-6 netrin cues.

UNC-6 netrin, a laminin-related protein secreted from neuroglia and neurons along the ventral midline, orients migrating cells and pioneering growth cones on the nematode epidermis. UNC-5, a cell surface protein expressed on motile cells and pioneer axons, orients movements away from UNC-6 sources. UNC-40, a homolog of the cell surface proteins DCC (Deleted in Colorectal Cancer) and neogenin, is also expressed on motile cells and pioneer neurons. UNC-40 acts cell autonomously to orient movement toward UNC-6 sources. For cells coexpressing UNC-5, it helps orient movement away from UNC-6 sources. Finally, UNC-40 helps determine the dorsoventral position of cells undergoing purely longitudinal migrations. Together with the recent report that DCC is a netrin receptor in vertebrates, our results suggest that UNC-40 is a component of UNC-6 receptors on motile cells.

Amino Acid Sequence↗
PubMed1996

Negative-strand RNA viruses: genetic engineering and applications.

The negative-strand RNA viruses are a broad group of animal viruses that comprise several important human pathogens, including influenza, measles, mumps, rabies, respiratory syncytial, Ebola, and hantaviruses. The development of new strategies to genetically manipulate the genomes of negative-strand RNA viruses has provided us with new tools to study the structure-function relationships of the viral components and their contributions to the pathogenicity of these viruses. It is also now possible to envision rational approaches--based on genetic engineering techniques--to design live attenuated vaccines against some of these viral agents. In addition, the use of different negative-strand RNA viruses as vectors to efficiently express foreign polypeptides has also become feasible, and these novel vectors have potential applications in disease prevention as well as in gene therapy.

Animals↗
PubMed1996

Construction of human factor IX expression vectors in retroviral vector frames optimized for muscle cells.

Development of a highly refined human factor IX (hFIX) expression vector system is critical for establishing a durable hemophilia B gene therapy. Here we report construction of a series of retroviral vectors and identification of an optimal basic structure and components for expressing hFIX in skeletal muscle cells. These vectors, which are derived from Moloney murine leukemia virus (MoMLV) with its enhancer sequence in the 3' long terminal repeat (LTR) deleted, contained internal hFIX expression units inserted in forward configuration without or with a viral vector intron sequence (pdL or pdLIn vector frame, respectively) or in inverted configuration without a viral vector intron sequence (pdLi frame). Internal expression units contained a hFIX cDNA or hFIX minigene (hIXm1 or hIXm2) derived from the hFIX cDNA by insertion of a shortened first intron sequence of the hFIX gene. Regardless of the promoter and vector frame used, both hIXm1 and hIXm2 gave 10- to 14-fold higher hFIX expression compared to those with hFIX cDNA. Internal hFIX transcriptional control units of these vectors were composed of various promoters linked with or without the muscle creatine kinase enhancer (Me) sequence. Promoters tested included those of alpha-actin (alpha A775), beta-actin (beta A280), cytochrome oxidase (CO1250 and CO650), myogenin (Mg1031 and Mg353), and Rous sarcoma virus (RSV). beta A200, which was derived from beta A280 by eliminating potential polyadenylation sites, was also tested. As extensively examined with the myogenin promoter, presence of one or multiple copies of Me in the vectors elevated the expression activity in myotubes by 4.5- to 19-fold over those without Me, but not significantly in myoblasts. Similar enhancements in expression activity with Me were also observed with other promoters, except those of RSV and CO. The latter two showed only modest enhancements in the presence of Me. As assayed with myotubes in culture, the general order of hFIX expression activity of various promoters with four copies of Me in the three different vector frames was beta A280 approximately beta A200 > Mg353 > Mg1031 approximately RSV approximately CO650 approximately alpha A775 > CO1250. One exception was that CO650 showed significantly less activity in pdLi-type vectors than in the pdLIn vectors. Based on the systematic analyses of various structural components, a group of pdLi vectors consisting of beta A200, two to four copies of Me, and hIXm2 was identified to have the optimal basic vector structure to be used in retrovirus for hFIX expression in differentiated skeletal muscle cells. The present studies provide the critical first step for establishing a highly refined hemophilia B gene therapy based on skeletal muscle-targeted hFIX gene transfer.

Animals↗
PubMed1996

Loss of DNA mismatch repair in acquired resistance to cisplatin.

Selection of cells for resistance to cisplatin, a well-recognized mutagen, could result in mutations in genes involved in DNA mismatch repair and thereby to resistance to DNA-alkylating agents. Parental cells of the human ovarian adenocarcinoma cell line 2008 expressed hMLH1 when analyzed with immunoblot. One subline selected for resistance to cisplatin (2008/A) expressed no hMLH1, whereas another (2008/C13*5.25) expressed parental levels. Microsatellite instability was readily demonstrated in 2008/A cells but not in 2008 and in 2008/C13*5.25 cells. In addition, the 2008/A cells were 2-fold resistant to methyl-nitro-nitrosoguanidine and had a 65-fold elevated mutation rate at the HPRT locus as compared to 2008 cells, both of which are consistent with the loss of DNA mismatch repair in these cells. To determine whether the loss of DNA mismatch repair itself contributes to cisplatin resistance, studies were carried out in isogenic pairs of cell lines proficient or defective in this function. HCT116, a human colon cancer cell line deficient in hMLH1 function, was 2-fold resistant to cisplatin when compared to a subline complemented with chromosome 3 and expressing hMLH1. Similarly, the human endometrial cancer cell line HEC59, which expresses no hMSH2, was 2-fold resistant to cisplatin when compared to a subline complemented with chromosome 2 that expresses hMSH2. Therefore, the selection of cells for resistance to cisplatin can result in the loss of DNA mismatch repair, and loss of DNA mismatch repair in turn contributes to resistance to cisplatin.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Effect of endotoxin in IL-1 beta-deficient mice.

IL-1 plays an important role in the pathophysiologic responses to infection and inflammation, in part by mediating its own production and that of other proinflammatory cytokines. However, the relative contribution of IL-1 alpha and IL-1 beta to the inflammatory response has not been well clarified. Using IL-1 beta-deficient (IL-1 beta -/-) mice, we investigated the specific role of IL-1 beta in the in vivo and in vitro response to LPS. No differences between IL-1 beta +/+ and IL-1 beta -/- mice were observed in circulating levels for IL-1 alpha, IL-6, or TNF-alpha after the systemic administration of either a low (5 micrograms/kg) or high (5 mg/kg) dose of LPS. IL-1 beta -/- mice also had a normal response to LPS in terms of activation of the hypothalamus-pituitary-adrenal axis, hypoglycemia, serum amyloid A production, and anorexia. IL-1 beta -/- mice were normally sensitive to the lethal effect of LPS and were protected against LPS toxicity when pretreated with low-dose LPS. However, in vitro, peritoneal macrophages from IL-1 beta -/- mice stimulated with LPS produced significantly less IL-1 alpha than macrophages from IL-1 beta +/+ mice (p < 0.05). No differences in IL-6 or TNF-alpha synthesis were observed between macrophages from IL-1 beta +/+ and IL-1 beta -/- mice. In summary, our results suggest that either IL-1 beta is not essential for the in vivo systemic response to LPS or that its role can be fulfilled by other cytokines with overlapping activities.

Animals↗
PubMed1996

Reduction of tumor hypoxia and inhibition of DNA repair by nicotinamide after irradiation of SCCVII murine tumors and normal tissues.

The alkaline comet assay was used to measure both tumor hypoxic fraction and DNA strand break rejoining kinetics in individual cells from tumors and tissues of C3H/HeN mice exposed to ionizing radiation and nicotinamide. The percentage of hypoxic cells in SCCVII marine squamous cell carcinoma decreased from 18.4 to 4.4% in mice injected with a clinically relevant dose of 200 mg/kg nicotinamide 30 min before irradiation. At higher doses (500 and 800 mg/kg), nicotinamide also increased the half-time of strand break rejoining in tumor, thymus, spleen, bone marrow, and testis from 10-20 min to 40-80 min. Cells from the brain rejoined radiation-induced breaks 3-5 times more slowly than did cells from other tissues and showed no additional delay after nicotinamide. Cells with extensive numbers of strand breaks appeared 24 h after treatment with nicotinamide and radiation and 48 h after treatment with radiation alone. For most tissues, damage was more consistent with necrosis than with apoptosis. The percentage of heavily damaged cells was dependent on tissue type, time after irradiation, radiation dose, nicotinamide dose, and sequence of administration. In SCCVII tumors of air-breathing mice, nicotinamide enhanced radiation-induced cell killing primarily in cells close to the vasculature, but in tumors clamped before irradiation, 500 mg/kg nicotinamide did not increase cell kill. It appears that in addition to promoting tumor reoxygenation, nicotinamide inhibits DNA strand break rejoining in tumors and most normal tissues and promotes the earlier appearance of radiation-damaged cells, perhaps through inhibition of poly(ADP-ribose) polymerase.

Animals↗
PubMed1996

Nonconserved nucleotides at the 3' and 5' ends of an influenza A virus RNA play an important role in viral RNA replication.

The genome of influenza A viruses is composed of eight negative-strand RNA segments which contain short noncoding regions at their 3' and 5' ends. The signals required for replication, transcription, and packaging of the viral RNAs are thought to be located in these regions. The highly conserved noncoding nucleotides, which form "panhandle" or "fork" structures by partial complementarity, are important for the transcriptional activity of the viral RNA polymerase. In contrast, the nonconserved noncoding nucleotides located close to the open reading frame of the viral RNAs had not been implicated in RNA transcription. Using a reverse-genetics system, we have now rescued influenza A/WSN/33 viruses whose NA-specific RNA segments have deletions in these nonconserved noncoding regions. Deletion either of the nucleotide residues between the poly(U) stretch and the stop codon at the 5' end or of the nucleotides between position 15 and the start codon at the 3' end did not affect the amount of NA-RNA species found in virions or infected cells. However, a combination of deletions at both the 3' and the 5' ends decreased by 60 times the levels of NA-specific viral RNA found in infected cells at late periods of infection and in virions. This double deletion was also responsible for a fourfold reduction of the steady-state levels of the NA-specific mRNA in infected cells. Viruses whose NA-specific open reading frames were flanked by the noncoding regions of the PB1- or the NS-RNA segments of infuenza A/WSN/33 virus also showed a reduction in the NA-specific viral RNA in virions and in infected cells. The present results demonstrate that the nonconserved nucleotides at the 3' and 5' ends of the NA-RNA segment of influenza A virus play an important role in the replication of this segment.

Animals↗
PubMed1996

Studies on the metabolism and biological function of APLP2.

Amyloid precursor proteins (APP) are a member of a larger family of proteins that include the amyloid precursor-like proteins (APLP) APLPI and APLP2. We have examined the expression and metabolism of APLP2 and document that APLP2 is expressed at high levels in the nervous system and in peripheral tissues. Furthermore, several APLP2 isoforms encoded by alternatively spliced transcripts are posttranslationally modified by a chondroitin sulfate glycosaminoglycan (CSGAG) chain. Furthermore, CSGAG modification is regulated by the insertion of sequences encoded by an alternatively spliced exon. Notably, expression of the CSGAG form of APLP2 appears restricted to embryonic neurons and mature neuronal populations that undergo regeneration, such as olfactory sensory neurons. Thus, differences in posttranslational modifications between the APLP2 isoforms and APP are likely to underlie differences in the regulation and function of these homologues. Our present efforts are directed towards using gene targeting strategies to disrupt the expression of the mouse APP/APLP2 genes to define the normative roles of the encoded molecules in development, plasticity, regeneration, and repair.

Alternative Splicing↗
PubMed1996

Mice deficient for the amyloid precursor protein gene.

To understand the in vivo function of the amyloid precursor protein (APP) we generated an APP null mutation in mice by homologous recombination in embryonic stem (ES) cells. We show here that homozygous APP deficient mice were produced at expected frequencies. Neither APP mRNA nor protein could be detected in these animals. Yet the homozygous APP mutant mice are fertile and do not show overt abnormalities at up to 12 weeks of age. Neuroanatomical studies of the brain did not reveal significant differences in the knockout mice as compared to the wild-type controls. These results argue against an essential function of APP in mouse embryonic and early neuronal development.

Amyloid beta-Protein Precursor↗
PubMed1996

Metallothionein-I and -II knock-out mice are sensitive to cadmium-induced liver mRNA expression of c-jun and p53.

Zinc pretreatment has been shown in vitro (rat myoblasts) to induce metallothionein (MT) and inhibit cadmium (Cd)-induced protooncogenes c-myc and c-jun mRNA levels. therefore, the purpose of this study was to determine whether the mRNA expression of the protooncogene c-jun as well as the tumor suppressor gene p53 is increased by Cd in the intact animal and, more specifically, in the target organ for Cd toxicity, the liver. Additionally, modulation of the expression of these genes was investigated in the absence of MT. The effect of CdCl2 on the mRNA levels of c-jun and p53 was studied in livers of C57BL/6J (control) and MT-null mice by Northern- and slot-blot analyses. The mRNA for c-jun and p53 were increased by Cd in a dose-dependent fashion. In the control mice, Cd induced c-jun mRNA (5-fold) at 3 and 12 hr and p53 mRNA (1.8- to 2-fold) at 6 and 12 hr. Compared to controls, the MT-null mice were more sensitive to the Cd-induced gene expression. The magnitude of the inductions was more pronounced and the elevated mRNA levels of c-jun and p53 were seen at lower doses of Cd (10mumol/kg in MT-null mice vs 40 mmol/kg in control mice). In conclusion, these data demonstrate that Cd induces mRNA expression of the protooncogene c-jun and tumor suppressor gene p53 in liver, and that MT modulates this effect.

Alanine Transaminase↗