Biomedical subjects

R Han

Publications and source records attributed to R Han.

At least 37 records · Page 2Linked to original sources

PubMed2000

Rabbit oral papillomavirus complete genome sequence and immunity following genital infection.

Rabbit oral papillomavirus (ROPV) infects mucosal tissues of domestic rabbits. The viral genomic sequence has been determined and the most related papillomavirus type was the cutaneous cottontail rabbit papillomavirus (CRPV). Homologies between the open reading frames (ORFs) of ROPV and CRPV, however, ranged from 68% amino acid identity for L1 to only 23% identity for E4. Shared features unique to the two rabbit viruses included a large E6 ORF and a small E8 ORF that overlapped the E6 ORF. Serological responses to ROPV L1 viruslike particles (VLPs) were detected in rabbits infected at either the genital or oral mucosa with ROPV. The antibody response was specific to intact ROPV L1 VLP antigen, was first detected at the time of late regression, and persisted at high levels for several months after complete regression. Both oral and genital lesions regressed spontaneously, accompanied by a heavy infiltrate of lymphocytes. ROPV infection of rabbit genital mucosa is a useful model to study host immunological responses to genital papillomavirus infections.

Animals↗

PubMed2000

Pathogenicity, development, and reproduction of Heterorhabditis bacteriophora and Steinernema carpocapsae under axenic in vivo conditions.

Galleria mellonella larvae cultured axenically were treated with axenic dauer juveniles of Heterorhabditis bacteriophora and Steinernema carpocapsae. After 3 days S. carpocapsae had killed all insects, with 9.4 +/- 4.3 nematodes per larva. H. bacteriophora were unable to kill G. mellonella, although 13.3 +/- 6.4 nematodes per Galleria were found in the hemocoel. Invading nematodes of both strains recovered from the dauer stage. H. bacteriophora developed into hermaphrodites with eggs and J1 in the uterus and in the hemolymph of the living insects. Development beyond the J1 stage was not recorded. An injection of supernatants from different Photorhabdus luminescens cultures killed the insects but could not provide nutrients to support a further development. Only the injection of bacterial cells supported production of dauers in the axenic insects. Axenic S. carpocapsae developed to adults and produced offspring. After 3 weeks an average of 5275 nematodes per larva were counted, of which 6.7% were dauer juveniles, 39.2% other juvenile stages, 11.9% males, and 42.2% females. Compared to in vivo reproduction in the presence of the symbiotic bacterium Xenorhabdus nematophilus the dauer juvenile yields were low. Even after 5 weeks the percentage of dauer juveniles did not surpass 10%.

Animals↗

PubMed2000

DNA vaccination prevents and/or delays carcinoma development of papillomavirus-induced skin papillomas on rabbits.

Malignant progression is a life-threatening consequence of human papillomavirus-associated lesions. In this study, we tested the efficacy of papillomavirus early-gene-based vaccines for prevention of carcinoma development of papillomavirus-induced skin papillomas on rabbits. Rabbit skin papillomas were initiated by infection with cottontail rabbit papillomavirus (CRPV). The papillomas were allowed to grow for 3 months without any treatment intervention. Rabbits were then immunized by gene gun-mediated intracutaneous administration of four DNA plasmids encoding CRPV E1, E2, E6, and E7 genes, respectively. All eight control rabbits receiving vector alone developed invasive carcinoma within 8 to 13 months. In contrast, only two of eight vaccinated rabbits developed carcinoma at 12 and 15 months, respectively. Papilloma growth was suppressed in the majority of vaccinated rabbits but not completely eradicated. These results indicate that gene gun-mediated immunization with papillomavirus early genes may be a promising strategy for prevention of malignant progression of human papillomavirus-associated lesions in humans.

Animals↗

PubMed2000

[Effects of a novel antiprogestin derivative ZXH951 on proliferation and telomerase activity of human breast carcinoma cell lines].

AIM: To investigate the antiproliferative activity of a new synthetic steroid ZXH951 structurally related to mifepristone (RU486) and its effects on cell cycle traverse and telomerase activity in human breast carcinoma cell lines. METHODS: Antiproliferative activity was determined by cell growth curve, MTT reduction and colony formation. Receptor binding affinities were measured by competitive binding assay using radiolabelled ligands. Cell cycle distribution was analyzed by flow cytometry. Telomerase activity was investigated by TRAP-PCR. RESULTS: ZXH951 exhibited potent antiproliferative activity in estrogen receptor and progesterone receptor positive human breast carcinoma cell lines in vitro, high affinity with human progesterone receptor-A, little affinity with estrogen receptor and blockade the cells in G1 phase. Moreover, when T47D cells were exposed to 0.4, 1.0 and 10 mumol.L-1 of ZXH951 for 72 h, the telomerase activity was significantly decreased. CONCLUSION: ZXH951 is a promising progesterone receptor antagonist. It significantly inhibits the growth of estrogen receptor and progesterone receptor positive human breast carcinoma cells. Its mechanism of action may be related to its antiproliferation mediated by progesterone receptor and inhibition of telomerase activity.

Breast Neoplasms↗

PubMed2000

[Comparison of infrared spectroscopy between native and binding metals' phytoplankton].

Infrared spectroscopy of native and metalbinding duckweed was compared. After binding metals, the absorbance peak around 3,400 cm-1, which reflects OH group stretching vibration, had been moved about 83 cm-1, and its absorbance was decreased. The absorbance of the dominating bands near 1,650 and 1,540 cm-1, the characteristic IR absorption of protein, was decreased. Therefore, the peak absorbance at 620 cm-1 was increased significantly by exposure to high concentration of ZnSO4 solution. So we concluded that OH group play a important role in binding zinc cation and the structure of cell walls had changed due to zinc existing. Furthermore, the process of binding metals by duckweed is physical adsorption and chemical adsorption simultaneously.

Adsorption↗

PubMed2000

[Nickel cation biosorping studies by yeast with dimethylglyoxime spectrophotometry].

The beer yeast as the biosorbent of Ni2+ is studied. Nickel cation was determined by dimethylglyoxime spectrophotometry. The adsorbed quantity is larger at pH = 6. The equilibrium time was 60 minutes. Salinity and Ca2+, Mg2+ have no significant effect on the biomaterial uptake. Higher the equilibrium concentration(c) is, larger the adsorbed quantity(q) of yeast is. In addition, relations between c and q were fitted with followed equations: 1/q = 0.340 + 0.0753 x 1/c, r = 0.995; lgq = 3.989 + 0.789 lgc, r = 0.995. So we concluded that the models of adsorption are fitted with Langmuir and Freundlich isotherm adsorption equation.

Adsorption↗

PubMed1999

Solution structure of the major alpha-amylase inhibitor of the crop plant amaranth.

alpha-Amylase inhibitor (AAI), a 32-residue miniprotein from the Mexican crop plant amaranth (Amaranthus hypochondriacus), is the smallest known alpha-amylase inhibitor and is specific for insect alpha-amylases (Chagolla-Lopez, A., Blanco-Labra, A., Patthy, A., Sanchez, R., and Pongor, S. (1994) J. Biol. Chem. 269, 23675-23680). Its disulfide topology was confirmed by Edman degradation, and its three-dimensional solution structure was determined by two-dimensional 1H NMR spectroscopy at 500 MHz. Structural constraints (consisting of 348 nuclear Overhauser effect interproton distances, 8 backbone dihedral constraints, and 9 disulfide distance constraints) were used as an input to the X-PLOR program for simulated annealing and energy minimization calculations. The final set of 10 structures had a mean pairwise root mean square deviation of 0.32 A for the backbone atoms and 1.04 A for all heavy atoms. The structure of AAI consists of a short triple-stranded beta-sheet stabilized by three disulfide bonds, forming a typical knottin or inhibitor cystine knot fold found in miniproteins, which binds various macromolecular ligands. When the first intercystine segment of AAI (sequence IPKWNR) was inserted into a homologous position of the spider toxin Huwentoxin I, the resulting chimera showed a significant inhibitory activity, suggesting that this segment takes part in enzyme binding.

Amino Acid Sequence↗

PubMed1999

Intramuscular injection of plasmid DNA encoding cottontail rabbit papillomavirus E1, E2, E6 and E7 induces T cell-mediated but not humoral immune responses in rabbits.

To test the efficacy of genetic vaccination against papillomavirus infection, plasmid DNA encoding cottontail rabbit papillomavirus (CRPV) E1, E2, E6, E7 or without insert were intramuscularly injected into five groups of rabbits. Peripheral blood mononuclear cells (PBMCs) showed specific proliferation upon in vitro stimulation with E1, E2, E6 or E7 proteins in a majority of vaccinated rabbits but Western blot analysis did not detect antibodies specific for these viral proteins in rabbit serum. All rabbits grew papillomas after virus challenge and none of the rabbits showed systemic papilloma regression. These observations showed that intramuscular injection of plasmid DNA encoding CRPV E1, E2, E6 or E7 induced CD4+ T cell-mediated but not humoral immune responses, and did not result in the protection of rabbits from virus infection.

Animals↗

PubMed1999

Development of keratoacanthomas and squamous cell carcinomas in transgenic rabbits with targeted expression of EJras oncogene in epidermis.

Activated ras genes have been frequently identified in both benign and malignant human tumors, including keratoacanthoma and squamous cell carcinoma. In this study, we developed two lines of transgenic rabbits in which the expression of EJras has been specifically targeted to the rabbit epidermal keratinocytes, using the upstream regulatory region of cottontail rabbit papillomavirus. All of the F1 transgenic progenies developed multiple keratoacanthomas at about 3 days after birth. The rabbits developed an average of 20 tumors, which usually reached the size of approximately 1 cm in diameter and then spontaneously regressed in about 2 months, similar to keratoacanthoma regression in humans. In addition, up to 18% of the rabbits then developed squamous cell carcinoma at about 5 months of age. The expression of EJras was detectable in all of the keratoacanthomas and squamous cell carcinomas. These results strongly support the involvement of the ras oncogene in both the initiation and regression of keratoacanthoma, and in the development of squamous cell carcinomas. These novel transgenic rabbits, with their consistent tumorigenic phenotype at an early age, high similarity to the human lesions, and easy accessibility for examination, manipulation, biopsy, and treatment, should provide a unique model system for studying ras activation-related tumor initiation, regression, and progression, and for evaluating antitumor therapies.

Animals↗

PubMed1999

Boswellic acid acetate induces differentiation and apoptosis in leukemia cell lines.

Boswellic acid acetate (BC-4), a compound isolated from the herb Boswellia carterii Birdw., can induce differentiation and apoptosis of leukemia cells. Based on cell morphology and NBT reduction, BC-4 induced monocytic differentiation of myeloid leukemia HL-60, U937 and ML-1 cells at a dose under 12.5 microg/ml (24.2 microM). BC-4 was a potent inducer, with 90% of the cells showing morphologic changes and 80-90% of the cells showing NBT reduction. Specific and non-specific esterase were also increased by BC-4. Based on benzidine staining assay, BC-4 failed to induce erythroid leukemia DS-19 and K562 cells differentiation. In contrast to its selective differentiation effect, BC-4 strongly inhibited growth of all cell lines tested. The growth inhibition effect was dose- and time-dependent. In HL-60 cells, 20 microg/ml (38.8 microM) of BC-4 decreased viable cell number by 60% at 24 h, whereas at 3 days there was virtually no viable cells. Morphologic and DNA fragmentation analysis proved that BC-4 induced cell apoptosis. The dual apoptotic and differentiation effects of BC-4 suggest that it may be a powerful agent in the treatment of leukemia.

Antineoplastic Agents, Phytogenic↗

PubMed1999

Effects of genistein, a soybean-derived isoflavone, on proliferation and differentiation of B16-BL6 mouse melanoma cells.

Genistein, a soybean-derived isoflavone, may contribute to the lower cancer incidence in South Asian countries. In this study, the effects and molecular mechanisms of genistein on growth and differentiation of B16-BL6 mouse melanoma cells were investigated. Genistein suppressed the growth of these melanoma cells. The IC50 value is 15.5 microM. On the other hand, genistein induced the changes of cell shape and cytoskeletal network. The cytoskeletal filaments were induced to form a bundle along the direction of elongation of the cells. Moreover, tyrosine phosphorylation levels of cytoskeleton-associated proteins decreased after the cells were exposed to 20 or 30 microM of genistein for 3 days. All these morphological and molecular changes were accompanied by appearance of the differentiated phenotypes. Genistein induced the increase of cellular melanin content, enhancement of tyrosinase activity, and decrease of colonization potentials in soft agar in a time-dependent and dose-dependent manner. The effective concentration was no more than 10 microM after 3 days' exposure. The tumorigenic potentials of B16-BL6 cells in C57BL/6 mouse also decreased after exposure to 20 or 30 microM of genistein for 3 days. When expressions of tumor-related genes were investigated in the differentiation-induced cells, the content of P53 dramatically increased while that of c-Myc protein decreased. Therefore, due to its ability to induce cellular and molecular changes, genistein suppressed the growth and induced differentiated phenotypes in B16-BL6 melanoma cells.

Animals↗

PubMed1999

Reduction of UV-induced skin tumors in hairless mice by selective COX-2 inhibition.

UV light is a complete carcinogen, inducing both basal and squamous cell skin cancers. The work described uses the selective COX-2 inhibitor celecoxib to examine the efficacy of COX-2 inhibition in the reduction of UV light-induced skin tumor formation in hairless mice. UVA-340 sun lamps were chosen as a light source that effectively mimics the solar UVA and UVB spectrum. Hairless mice were irradiated for 5 days a week for a total dose of 2.62 J/cm(2). When 90% of the animals had at least one tumor, the mice were divided into two groups so that the tumor number and multiplicity were the same (P < 0.31). Half of the mice were then fed a diet containing 1500 p.p.m. celecoxib. Tumor number, multiplicity and size were then observed for the next 10 weeks. Ninety-five percent of the tumors formed were histopathologically evaluated as squamous cell carcinoma. COX-2 expression and activity were increased in tumors. After 10 weeks, the difference in tumor number and multiplicity in the drug-treated group was 56% of UV controls (P < 0.001). The results show that the orally administered selective COX-2 inhibitor celecoxib prevents new tumor formation after the onset of photocarcinogenesis and suggest that treatment with celecoxib may be very useful in preventing UV-induced skin tumors in humans.

Animals↗

PubMed1999

99Tcm-p-aminohippuric acid as a new renal agent.

99Tcm-p-aminohippuric acid (99Tcm-PAH) is a new renal radiopharmaceutical prepared from a lyophilized kit by the addition of sodium pertechnetate (Na99TcmO4). Each vial contains PAH, the calcium trisodium salt of diethylenetriamine pentaacetic acid (CaNa3DTPA) and stannous chloride (SnCl2.2H2O) in an inert atmosphere. It is a stable radiopharmaceutical with high radiochemical purity (> 95%). Its protein binding is very similar to that of 131I-OIH, but it is hydrophilic in character. Animal studies using 99Tcm-PAH have indicated that it provides renal images of satisfactory quality with no external background. Despite its almost identical radiochemical purity and HPLC analysis results to 99Tcm-DTPA, 99Tcm-PAH is rapidly secreted by the kidneys in a manner consistent with tubular secretion, as confirmed by rat probenecid studies, whereas 99Tcm-DTPA is excreted by glomerular filtration. The pharmacokinetic parameters of 99Tcm-PAH (t1/2(alpha)) = 2.5 min, t1/2(beta) = 41.7 min, Cl = 5.22 ml.min-1, Kel = 5.1 x 10(-4) min-1) differ from those of 99Tcm-DTPA. Evaluation of 99Tcm-PAH in two human volunteers confirmed its good renal characteristics: rapid disappearance from the vascular system, high uptake in kidneys followed by its very fast elimination, and low residual activity 20 min after its intravenous administration.

Animals↗

PubMed1999

Protection of rabbits from viral challenge by gene gun-based intracutaneous vaccination with a combination of cottontail rabbit papillomavirus E1, E2, E6, and E7 genes.

In this study, cottontail rabbit papillomavirus infection of domestic rabbits was used as an animal model to develop papillomavirus early gene-based vaccines. Groups of rabbits were intracutaneously vaccinated with single papillomavirus early genes E1, E2, E6, and E7 or with a combination of these four genes. Only a fraction of rabbits were protected from subsequent viral challenge when vaccinated with the E1 or E6 gene. Viral tumor growth in those rabbits vaccinated with the E1 or E2 gene was suppressed compared to that in controls. In contrast, seven of nine rabbits vaccinated with the combination of the E1, E2, E6, and E7 genes were completely protected against viral challenge. These data indicated that intracutaneous genetic vaccination with the combination of the E1, E2, E6, and E7 genes can be an effective strategy for immunoprophylaxis of papillomavirus infection.

Animals↗

PubMed1999

[Formation of germline chimeras from murine embryonic stem cell lines].

Generation of germline chimeras is the crucial step in ES cell-mediated transgenesis. The prerequisite for germline chimerism is the maintenance of germline differentiating potency of ES cells, whereas production of germline chimeras is the only method to prove whether such potency is maintained. In order to investigate the germline differentiating potency of three newly established ES cell lines (MESPU21, MESPU22 and MESPU29), ES cells were introduced into host embryos from inbred C57BL/6J and outbred KMW or ICR through blastocyst injection or 8-cell stage morula injection. Totally 81 chimeras were obtained; among 42 test-bred ones, 19 were germline transmitters assessed by coat analysis, as is the first report of ES cell-embryo germline chimeras in China. MESPU21 and MESPU22 formed germline chimeras in high frequency and most of those chimeras produced ES cell-derived progeny in high proportion, which proved that both ES cell lines retained good germline differentiating potency and could be used as valuable cellular vehicles to introduce genetic modifications into mouse genome.

Animals↗

PubMed1999

Mutated ras p21 as a target for cancer therapy in mouse transitional cell carcinoma.

PURPOSE: To establish an experimental mouse model for bladder cancer immunotherapy using mutated ras as a target. MATERIALS AND METHODS: A tumorigenic mouse bladder transitional cell carcinoma (TCC) line MB49 (C57BL/6 origin) was analyzed for its c-ras gene status by DNA cloning and sequencing. Aberrant expression of the ras gene was measured with Western blotting. 13-mer peptides corresponding to residues 5 to 17 of the ras protein were synthesized and tested for immunogenicity in syngeneic C57BL/6 mice. Induction of specific immune responses was evaluated by analyzing splenocyte activity in vitro and tumor suppression in vivo. RESULTS: MB49 cells were found to contain a single amino acid substitution of serine for glycine at codon 12 in K-ras loci and an abundant amount of cellular mutated ras p21 protein. C57BL/6 mice immunized with the 13-mer serine-containing ras peptide exhibited mutation-specific immune responses in splenocyte proliferation, cytokine production and cytotoxicity. Specific antitumor immunity in the form of tumor growth delay in vivo was observed in mice immunized with the same mutant peptide followed by subcutaneous MB49 tumor challenge and was enhanced by the addition of low dose interleukin-12. CONCLUSIONS: The mouse bladder TCC line MB49 contains a serine mutation at codon 12 of its K-ras gene that is sufficient to induce mutation-specific immune responses in vitro and specific protective immunity to MB49 tumor in vivo. Mutated oncoproteins may be ideal targets for the development of specific immunotherapy regimens for bladder cancer immunotherapy.

Animals↗

PubMed1999

[Establishment of two ES cell lines with good germline contribution].

Nine embryonic stem cell lines have been established from mouse strain 129/ter. Three of the nine ES cell lines were karyotypically normal. The nine cell lines showed some difference in the growth rate and the differential competence. Chimeras were made by injecting the ES cells into C57BL/6J blastocysts, and the germline compositions of the chimeras were detected by mating them with albino ICR mice. The results indicated that ES cell line MESPU21 and MESPU22 were both highly germline-competent. Comparing with other ones, these two cell lines both were karyotypically normal and propagated fast. The tissue composition of the teratocarcinomas derived from these cell lines appeared paralle to the results of chimera production. Careful manipulation during the process of ES cell establishment was helpful to obtain good cell lines.

Animals↗

PubMed1999

[Establishment of a high germline competent C57BL/6J ES cell line].

Eleven ES cell lines from C57BL/6J mice were established, with the primary culture of mice embryos as feeder cells and 1 x 10(3) units Leukemia Inhibitory Factor (LIF) in the DMEM (high glucose) medium. The frequency of establishment was 9.6%. Five of these ES cell lines were demonstrated karyotypically normal with diploid composition of over 70%. They shared the characteristics of early embryonic cells: positive for alkaline phosphatase activity and oct4 gene expression. They also showed high potency to differentiate into wide types of cells in vivo. Following injection of the blastocysts, three of them showed abilities to give rise to chimeras and MESPU35 cell line was identified to have high efficiency of colonization into the germline. The clones of MESPU35 cells maintained the germline competence and the mutant clone also retained the high potency to participate into the development of embryos. MESPU35 cells can serve as a valuable vehicle for the production of mutant mice.

Animals↗