Biomedical subjects

Li Shi

Publications and source records attributed to Li Shi.

At least 19 recordsLinked to original sources

PubMed2005

Stabilization of human papillomavirus virus-like particles by non-ionic surfactants.

Human papillomavirus (HPV) virus-like-particles (VLPs) produced by recombinant expression systems are promising vaccine candidates for prevention of cervical cancers as well as genital warts. At high protein concentrations, HPV VLPs, comprised of the viral capsid protein L1 and expressed and purified from yeast, are protected against detectable aggregation during preparation and storage by high concentrations of NaCl. At low protein concentrations, however, high salt concentration alone does not fully protect HPV VLPs from aggregation. Moreover, the analytical analysis of HPV VLPs proved to be a challenge due to surface adsorption of HPV VLPs to storage containers and cuvettes. The introduction of non-ionic surfactants into HPV VLP aqueous solutions provides significantly enhanced stabilization of HPV VLPs against aggregation upon exposure to low salt and protein concentration, as well as protection against surface adsorption and aggregation due to heat stress and physical agitation. The mechanism of non-ionic surfactant stabilization of HPV VLPs was extensively studied using polysorbate 80 (PS80) as a representative non-ionic surfactant. The results suggest that PS80 stabilizes HPV VLPs mainly by competing with the VLPs for various container surfaces and air/water interfaces. No appreciable binding of PS80 to intact HPV VLPs was observed although PS80 does bind to the denatured HPV L1 protein. Even in the presence of stabilizing level of PS80, however, an ionic strength dependence of HPV VLP stabilization against aggregation is observed indicating optimization of both salt and non-ionic surfactant levels is required for effective stabilization of HPV VLPs in solution.

Calorimetry, Differential Scanning↗

PubMed2005

Universal influenza B vaccine based on the maturational cleavage site of the hemagglutinin precursor.

Conventional influenza vaccines can prevent infection, but their efficacy depends on the degree of antigenic "match" between the strains used for vaccine preparation and those circulating in the population. A universal influenza vaccine based on invariant regions of the virus, able to provide broadly cross-reactive protection, without requiring continuous manufacturing update, would solve a major medical need. Since the temporal and geographical dominance of the influenza virus type and/or subtype (A/H3, A/H1, or B) cannot yet be predicted, a universal vaccine, like the vaccines currently in use, should include both type A and type B influenza virus components. However, while encouraging preclinical data are available for influenza A virus, no candidate universal vaccine is available for influenza B virus. We show here that a peptide conjugate vaccine, based on the highly conserved maturational cleavage site of the HA(0) precursor of the influenza B virus hemagglutinin, can elicit a protective immune response against lethal challenge with viruses belonging to either one of the representative, non-antigenically cross-reactive influenza B virus lineages. We demonstrate that protection by the HA(0) vaccine is mediated by antibodies, probably through effector mechanisms, and that a major part of the protective response targets the most conserved region of HA(0), the P1 residue of the scissile bond and the fusion peptide domain. In addition, we present preliminary evidence that the approach can be extended to influenza A virus, although the equivalent HA(0) conjugate is not as efficacious as for influenza B virus.

Amino Acid Sequence↗

PubMed2005

[Gene frequencies and haplotypes of nine Y-short tandem repeat loci in four minority populations of China].

OBJECTIVE: To investigate the polymorphism of nine Y-short tandem repeat loci in 117 male individuals from four minority populations of China, and to obtain the polymorphism information in these populations. METHODS: Nine loci in all samples were amplified by PCR. Products were electrophoresed on ABI PRISM 377 DNA sequencer. The electrophoresis result was analyzed by Genotyper 2.0 software. Allele frequencies, diversities and genetic distance were calculated. RESULTS: Forty-three alleles and 32 haplotypes were found in Manchu population, 43 alleles and 33 haplotypes in Uygur population, 31 alleles and 15 haplotypes in Kirgiz population and 34 alleles and 23 haplotypes in Zhuang population. The closest genetic distance is 0.02530 between Manchu and Uygur, the highest genetic distance is 0.34590 between Kirgiz and Zhuang. CONCLUSION: High haplotype diversities were found in four populations. The study of genetic diversity among different populations is useful in research of their origins, migrations and their relationships.

China↗

PubMed2004

Dead cells in melanoma tumors provide abundant antigen for targeted delivery of ionizing radiation by a mAb to melanin.

Melanoma is a cancer with a rising incidence, and metastatic disease is almost always lethal. We investigated the feasibility of targeting melanin, an intracellular melanocyte pigment, to deliver cytotoxic radiation to human melanoma cells in vivo by using a melanin-binding mAb (6D2). Nude mice bearing MNT1 pigmented human melanoma tumors were treated with mAb 6D2 labeled with 1.5 mCi (1 Ci = 37 GBq) of the beta-emitter 188-Rhenium (188Re) and manifested inhibition of tumor growth and prolonged survival. mAb 6D2 bound tumor melanin and demonstrated no crossreactivity with normal melanized tissues in black mice. The mechanism of melanin targeting involved Ab binding to extracellular melanin released during tumor cell turnover or to dying cells with permeable membranes. In this approach, the cytotoxic radiation emanating from labeled Ab bound to melanin is presumably delivered by "crossfire" effect to the adjacent viable tumor cells. Our results establish the feasibility of targeting melanin released from dead melanoma cells in tumors with radiolabeled Abs to achieve a therapeutic effect. In contrast to conventional tumor antigens, melanin is insoluble, resistant to degradation, and can be expected to accumulate in targeted tissues, suggesting that the efficacy of therapy could increase with each subsequent treatment cycle.

Animals↗

PubMed2004

Preclinical study of influenza virus A M2 peptide conjugate vaccines in mice, ferrets, and rhesus monkeys.

A universal influenza virus vaccine that does not require frequent updates and/or annual immunizations will offer significant advantages over current seasonal flu vaccines. The highly conserved influenza virus A M2 membrane protein has been previously suggested as a potential antigen target for such a vaccine. Here, we report systematic evaluation of M2 peptide conjugate vaccines (synthetic peptides of M2 extracellular domain conjugated to keyhole limpet hemocyanin (KLH) or Neisseria meningitidis outer membrane protein complex (OMPC)) in mice, ferrets, and rhesus monkeys. The conjugate vaccines were highly immunogenic in all species tested and were able to confer both protection against lethal challenge of either H1N1 or H3N1 virus in mice and reduce viral shedding in the lower respiratory tracts of mice and ferrets. The protection against lethal challenge in mice could also be achieved by passive transfer of monkey sera containing high M2 antibody titers. In addition, we showed that M2 antisera were cross reactive with M2 peptides derived from a wide range of human influenza A strains, but they failed to react with M2 peptides of the pathogenic H5N1 virus (A/Hong Kong/97). The data presented here will permit better understanding of the potential of an M2-based vaccine approach.

Amino Acid Sequence↗

PubMed2004

Profiling the thermoelectric power of semiconductor junctions with nanometer resolution.

We have probed the local thermoelectric power of semiconductor nanostructures with the use of ultrahigh-vacuum scanning thermoelectric microscopy. When applied to a p-n junction, this method reveals that the thermoelectric power changes its sign abruptly within 2 nanometers across the junction. Because thermoelectric power correlates with electronic structure, we can profile with nanometer spatial resolution the thermoelectric power, band structures, and carrier concentrations of semiconductor junctions that constitute the building blocks of thermoelectric, electronic, and optoelectronic devices.

Journal Article↗

PubMed2004

Cloning of the gene encoding urease subunit A in Helicobacter pylori.

The gene encoding urease subunit A (ureA) of Helicobacter pylori (H. pylori) was cloned from H. pylori isolate by polymerase chain reaction (PCR). Sterile distilled water instead of DNA served as negative control. The nucleotide sequence of the amplified product was determined. Homologous analysis of the ureA against that reported by Clayton CL and the GenBank and SwissProt databases were performed with the BLAST program at the Genome Net through the Internet. 0.8 kb PCR product was amplified from all H. pylori clinical isolators. The nucleotide sequence of the ureA was determined. The nucleotide sequence of the ureA began with ATG as the initiation codon and terminated in TAA as stop codon. The coding regions had a 44% G + C content. The DNA sequence was 98% homologous to that reported by Clayton CL (688 out of 702 residues were identical). The derived amino-acid sequences of the ureA were 99% homologous to that reported by Clayton CL (232 out of 234 residues were identical). The nucleotide sequence and the predicted protein showed significant homology to ureA of H. pylori in the NCBI Entrez database.

Base Sequence↗

PubMed2004

Regulation of alternative splicing of Bcl-x by IL-6, GM-CSF and TPA.

The splicing of many alternative exons in the precursor messenger RNA (pre-mRNA) is regulated by extracellular factors but the underlying molecular bases remain unclear. Here we report the differential regulation of Bcl-x pre-mRNA splicing by extracellular factors and their distinct requirements for pre-mRNA elements. In K562 leukemia cells, treatment with interleukin-6 (IL-6) or granulocyte-macrophage colony stimulating factor (GM-CSF) reduced the proportion of the Bcl-xL variant mRNA while treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) had no effect. In U251 glioma cells, however, TPA efficiently increased the Bcl-xL level. These regulations were also seen for a transfected splicing reporter mini-gene. Further analyses of deletion mutants indicate that nucleotides 1-176 on the downstream intron are required for the IL-6 effect, whereas additional nucleotides 177-284 are essential for the GM-CSF effects. As for the TPA effect, only nucleotides 1-76 are required in the downstream intron, Thus UK-6, GM-CSF and TPA differentially regulate Bcl-x splicing and require specific intronic pre-mRNA sequences for their respective effects.

Alternative Splicing↗

PubMed2004

Pharmaceutical stability testing conference.

The Pharmaceutical Stability Testing conference organised by SMi was held on the 8th and 9th of September 2003 in London. The focus of the conference was on stability testing issues related to both compound drugs and biopharmaceuticals and the impact of stability testing on product development and commercialisation. The conference brought two days of presentations given by formulation, process, analytical, quality and regulatory professionals from both the European and US pharmaceutical industries. The presentations discussed various issues related to pharmaceutical stability testing in early stage preclinical development, during clinical studies and in late stage development for regulatory filing. The discussions covered biologicals and small molecules, drug substance and drug product, with supporting case studies.

Drug Approval↗

PubMed2004

[Immunogenecity of combined hepatitis A and B vaccine].

OBJECTIVE: To observe the immunogenicity of combined hepatitis A and B vaccine (HAB). METHODS: The combined HAB vaccine was prepared and different concentrations of HAB were administered on mice in week 0, 4 and 24, and then we tested the antibodies to both hepatitis A virus and B virus. After the first injection, we tested the hepatitis A antigen-induced and hepatitis B surface antigen-induced stimulation indices in spleen monocyte as well as changes of CD4+ and CD8+ cell numbers. RESULTS: The serum antibody positive rates were 100% in all three groups, and the antibody induced by HAB vaccine were earlier than by monovalent vaccine. The hepatitis A antibody and hepatitis B surface antibody titers after the combined vaccine inoculation were not significantly higher than those after the monovalent vaccine inoculation. On the other hand, after the first injection of the combined vaccine, the hepatitis A antigen-induced and hepatitis B surface antigen-induced stimulation indices in spleen monocyte were detected. The numbers of CD4+ and CD8+ cells increased. CONCLUSIONS: HAB vaccine has reliable immunogenicity.

Animals↗

PubMed2004

[Immunoblot and immunohistochemical analysis of CYP2A expression in human olfactory mucosa].

OBJECTIVE: To investigate the nasal expression of CYP2A proteins in human. METHODS: Immunoblot analysis was used to detect fetal tissues at 96-185 days of gestational age and in surgical biopsy tissues from different regions of nasal cavity of 36 adult patients, and immunohistochemical methods were used to localize CYP2A proteins' cellular distribution. RESULTS: In adults, CYP2A protein was detected in olfactory microsomes from 8 of 10 individual, but not in the respiratory nasal microsomes from 37 individual. Quantitative immunoblot analysis confirmed that CYP2A proteins were selectively expressed in the olfactory region in both adult and fetal tissues. Interestingly, the levels of CYP2A proteins in nasal microsomes were generally higher in fetuses than in adults. The CYP2A protein content in olfactory microsomes ranged from 0.1 to 1.1 pmol/mg among adult nasal microsomes, while among five fetuses ranged from 0.8 to 5.3 pmol/mg microsomal protein, with a trend of developmental increase in expression level. Immunohistochemical studies confirmed that the CYP2A proteins were expressed in the supporting cells in the olfactory epithelium and in the Bowman's glands in the lamina propria. CONCLUSIONS: CYP2A proteins expression in human olfactory mucosa indicates that olfactory mucosa is metabolic target site of the xenobiotics. Also CYP2A has a relationship with olfaction. The prenatal expression of the CYP2A proteins in the OM suggests potential risks of developmental toxicity from maternally derived xenobiotics.

Adolescent↗

PubMed2004

[The developmental expression of embryonic-neural cell adhesive molecule in human olfactory mucosa].

OBJECTIVE: To discuss the expressional features and physical function of E-NCAM (embryonic- neural cell adhesive molecule) in human fetal olfactory mucosa. METHOD: The immune expressions of E-NCAM in human olfactory mucosa at different gestational stages was detected with the technique of immunohistochemistry. RESULT: The positive expression of E-NCAM began at gestational week 14 (14W), and was localized in the cell bodied, dendrites, axis of olfactory neurons and olfactory nerve fiber bundles in lamina propria. The positive cells increased and the densities of staining of fiber bundles rose with the development of the fetus and reached the peak at 28W and decreased gradually then on. And at each stage the E-NCAM positive cells were localized at middle-lower parts of olfactory mucosa while the sustentacular cells and neurons at the top part were always E-NCAM negative. CONCLUSION: The expression features of E-NCAM are coincident with the plastict transformation of olfactory neurons. The high expression of E-NCAM at early half parts of gestation is helpful to the growth of neurons in differentiation and the down-regulation at late-half parts of gestation is helpful to the stabilization of structure of mature neurons.

Embryo, Mammalian↗

PubMed2004

[Genetic analysis of 17 biallelic markers on Y chromosome in 3 Chinese ethnic group populations].

OBJECTIVE: To study the genetic polymorphism of Y chromosome in different Chinese ethnic group populations. METHODS: Genotypes of 17 biallelic markers located in the nonrecombining portion of the Y chromosome in 76 men from 3 Chinese ethnic group populations (Han in Shandong, Bai in Yunnan, and Tu in Qinghai) were examined with polymerase chain reaction (PCR) and allelic-specific PCR (ASPCR). Their haplotypes made of these 17 binary markers were constructed. The principle component (PC) analysis was conducted based on the haplotype frequency distribution among these 3 and other 15 published Chinese ethnic group populations. RESULTS: The diversities of M50, M110, M103, M88, M3, and M7 were not found in these 3 populations. The frequencies of YAP+ were 23.8%, 6.7%, and 4% respectively in Tu, Bai, and Shandong Han. Eleven haplotypes were found in 3 populations--7 haplotypes (H1, H3, H5, H6, H8, H9, and H11) in Shandong Han (Han.SD), 8 haplotypes (H1, H2, H3, H5, H6, H8, H11, and H16) in Tu, and 9 haplotypes (H1, H3, H4, H5, H6, H8, H9, H11, and H13) in Bai. The predominant haplotypes were H1, H3, H5, H6, H8, and H11. According to PC analysis, Bai was close to Northern Han; Shandong Han, Southern Han (Han.S), Bai and Yunnan Tibetan clustered together; and Tu was close to Yi, Hui and Manchurian. CONCLUSIONS: Shandong Han may have had genetic exchanges with southern populations in China. It has been confirmed that some gene components of Han had flowed into Bai's gene pool. Gene flowed from Central Asia had impacted Chinese western populations.

Alleles↗

PubMed2003

Immunoblot analysis and immunohistochemical characterization of CYP2A expression in human olfactory mucosa.

The aim of the present study was to further characterize the expression of the CYP2A genes in human nasal mucosa. Fetal nasal tissues at 12-26 weeks of gestational age and surgical biopsy tissues from various regions of nasal cavity of adult patients were studied to determine whether CYP2A proteins can be detected by immunoblot in adults, whether higher levels of CYP2A proteins are present in adult than in fetal nasal mucosal microsomes, and whether CYP2A13 mRNA is more abundant than CYP2A6 mRNA in fetal nasal mucosa. In adults, immunoblot analysis detected CYP2A proteins in microsomes of the olfactory region from 8 of 10 individuals, but in none of the nasal microsomes of the respiratory region from 47 patients. Quantitative immunoblot analysis confirmed that CYP2A proteins are selectively expressed in the olfactory region in both adult and fetal tissues. Interestingly, the levels of CYP2A proteins in nasal microsomes were generally higher in fetuses than in adults. In the fetus, the level of CYP2A13 mRNA was much higher than that of CYP2A6 mRNA, as has been previously found in adult nasal mucosa. Immunohistochemical studies confirmed that, in the fetus, the CYP2A proteins are expressed in the supporting cells in the olfactory epithelium and in the Bowman's glands in the lamina propria. The prenatal expression of the CYP2A proteins in the olfactory mucosa suggests potential risks of developmental toxicity from maternally derived xenobiotics, since both CYP2A6 and CYP2A13 are known to be efficient in the metabolic activation of tobacco-specific nitrosamines and other respiratory toxicants.

Aryl Hydrocarbon Hydroxylases↗

PubMed2003

Repression of MUC2 gene expression by butyrate, a physiological regulator of intestinal cell maturation.

Sodium butyrate (NaB) inhibits proliferation, stimulates apoptosis, and promotes differentiation of human colon cancer cells along the absorptive phenotype. In vitro, butyrate induces a switch from cells with a secretory to an absorptive phenotype. Here, we report that NaB specifically represses the expression of the MUC2 gene, a differentiation marker of the secretory goblet cell lineage, in forskolin- and 12-O-tetradecanoylphorbol 13-acetate-induced HT29 cells, and Cl.16E cells, a clonal derivative of HT29 cells that spontaneously differentiates into goblet cells. Thus, NaB repression is independent of the nature of the stimulus that triggers MUC2 expression. Further, repression was independent of new protein synthesis. Our results suggest that inhibition of MUC2 is linked to the ability of butyrate to repress histone deacetylase activity, since trichostatin A, another inhibitor of histone deacetylases, also inhibited MUC2 expression in induced HT29 cells. Finally, we demonstrate that the NaB effect is specific for this marker of the secretory cell lineage, since carcinoembryonic antigen, which is expressed in both the secretory and absorptive cells, is induced by NaB. Thus, the NaB repression of a definitive function of the secretory cell lineage is a further mechanism, in addition to the effects on proliferation and apoptotic pathways, through which butyrate can regulate intestinal homeostasis.

Butyrates↗

PubMed2003

A potential spontaneous rat model of X-linked congenital stationary night blindness.

PURPOSE: To describe a possible spontaneous rat model of X-linked congenital stationary night blindness (CSNB). METHODS: Experimental animals were generated by mating the affected animal to normal rats, and from interbreeding littermates. To define the inheritance pattern, full-field electroretinograms (ERGs) were recorded from all progeny. RESULTS: During the course of other experiments, an affected male rat was identified by a reduced amplitude ERG b-wave. When this rat was mated to normal Sprague-Dawley rats, all of the F1 progeny had normal ERG waveforms. When F1 offspring were interbred, 51% of the male offspring had b-wave reductions while all female offspring had normal ERG waveforms. When F1 females were backcrossed to the original affected male, b-wave reductions were noted in both male and female offspring; overall, 46.8% of the backcross progeny exhibited a b-wave reduction. In affected animals, the b-wave was selectively affected as the a-wave appeared to retain normal amplitude and kinetics at 1-4 months old. Cone ERGs were significantly reduced in amplitude and somewhat delayed. Similar ERG results were also obtained under the same stimulus conditions from human patients with complete CSNB (CSNB1). CONCLUSIONS: The inheritance pattern is consistent with an X-linked recessive trait. The electrophysiological results suggest that this mutant rat line may provide another model for CSNB1.

Adult↗

PubMed2003

Histological study of experimental reconstructive materials for repair of lateral skull base and dura mater defects in dogs.

OBJECTIVE: In order to assess the reconstructive properties of fascia lata, superficial fascia lata and bone morphogenetic protein (BMP) in skull base surgery, lateral skull base bone and dura mater defect models were established in dogs MATERIAL AND METHODS: As a repair material we selected fascia lata, either alone or in combination with BMP, for reconstructing large cranial defects in dogs. Twenty dogs undergoing a 3.0 x 4.0 cm2 full-thickness excision of the parietal bone were divided into four equal groups as follows: fascia lata reconstruction; fascia lata reconstruction plus BMP; controls; and fascia lata reconstruction plus BMP with direct exposure of fascia lata. The implants were harvested at 2-15 weeks and examined histologically. Results-Treated and untreated implants were quite different: formation of new bone occurred in the dogs treated with BMP whereas the unreconstructed controls demonstrated only a bridge of fibrovascular connective tissue. CONCLUSION: The results of this study suggest that it is better to combine BMP and reconstructive material for the treatment of bone defects.

Animals↗

PubMed2003

Antibodies to a cell surface histone-like protein protect against Histoplasma capsulatum.

A protective role for antibodies has not previously been described for host defense against the pathogenic fungus Histoplasma capsulatum (Hc). Mouse mAb's were generated from mice immunized with Hc yeast that binds the cell surface of Hc. Administration of mAb's before Hc infection reduced fungal burden, decreased pulmonary inflammation, and prolonged survival in a murine infection model. Protection mediated by mAb's was associated with enhanced levels of IL-4, IL-6, and IFN-gamma in the lungs of infected mice. The mAb's increased phagocytosis of yeast by J774.16 cells through a CR3-dependent process. Ingestion of mAb-opsonized Hc by J774.16 macrophage-like cells was associated with yeast cell growth inhibition and killing. The mAb's bound to a 17-kDa antigen expressed on the surface of Hc. The antigen was identified as a histone H2B-like protein. This study establishes that mAb's to a cell surface protein of Hc alter the intracellular fate of the fungus and mediate protection in a murine model of lethal histoplasmosis, and it suggests a new candidate antigen for vaccine development.

Amino Acid Sequence↗